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  1. #51
    Enthusiast Patentlaw's Avatar
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    Hi Steve,

    So I like the engineering challenge. First, I think you have really analyzed everything well. One thing I noticed and that is really basic, is that you have a tendency to run better times with the temperature right around 50 degrees. The outlier is 8/23 where you were driving really effectively based on your 1/4 mile time and there being a 20 degree temperature increase, but only a very mild increase in time. I think that you were just "on" that day compared with the others. That type of driving on a colder day and I think you have it. No further analysis needed.

    One thing I don't see is the amount of gas you had. At 6lb per gallon, perhaps some of your variability is based upon the amount of fuel in the car. I know.....the last thing you need is another variable, but it is a possibility. 6 gallons is 36 pounds. Just roughly calculating, that is 1 percent difference which would be enough to put you under.

    Another variable that may come into play even more is the coefficient of friction for rubber at different temperatures. There have been a few studies that I saw on the internet looking at the differences between 30 degrees to 85 degrees. Seeing as the temperature really played a factor there, something as simple as warming the tires and a few seconds could make all the difference as the tires will hook up better. Again, not perfect, but we are talking such small amounts here, that any of these factors can come into play.

    Plaw

  2. #52
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    Yes, the density altitude and race weight will both have an impact, but I've largely avoided factoring them in for a couple of reasons:

    1. Up until now, I've had to rely on online resources for the density altitude at my local track. It always seems reasonable, but I've noted enough discrepancies between what the databases say and what I've observed at the track to know they aren't 100% accurate. Having my own weather meter from now on will help, but unfortunately the vast majority of my data was generated without it.
    2. There is a scale at the track - sometimes it is working, but sometimes it isn't. I've only used it a couple of times to get a general idea of where I sit, and it's always been right around 3,600 pounds give or take. Getting a race weight after every run is possible, but it takes up valuable time, and is also a bit cumbersome because it is the same guy running that along with handing out time slips to all of the people running (which is usually about 100 cars on any given night).

    I tend to show up to the track in about the same general state every time - full street trim, about 1/2 a tank of gas for the first pass, and all of my typical equipment (GoPro, laptop w/ my tuning interface, tire pressure gauge, helmet, fire jacket, and usually a couple bottles of water and some light snacks). The car gets driven to and from the track exactly like I race it, because 9 times out of 10 I'm completely on my own. My race weight has probably gone down by about 60-70 pounds over the last 4 years I've been doing this...I've personally lost some weight due to long distance running, and I've also shed some vehicle weight with the lighter weight Nth Moto clutch assembly and the lighter wheels and tires. There was about a 10 pound difference per tire just between the Mickey Thompson drag radials and the Hoosiers I'm running now, which also has the added benefit of being rotational mass - some say a reduction in rotating mass is worth way more than just removing seats/carpet/etc., but how much is debatable. That's why I was expecting to see at least something in the form of better MPH with the Hoosiers, but then I had to go and mess with the tune.

    The weather is always a wild card, especially around here during the month of October when I've run my best times. It could be 80°F, or it could be 50°F on any given day. I also don't really pay attention to other factors like wind speed or direction; the track faces northwest, so any wind will generally be a head wind, but it's never usually any more than 5-10 MPH. I also don't have any idea what the track surface temps are like. So yes, my best results do tend to be when the air temps are under 60°F, but those days have also usually been sunny, so the black track surface will be quite a bit warmer than if it was cloudy. The one thing I've noted is that most people tend to make record breaking passes when the temps are low, but the sky is clear. Cool air + a warm track due to the sun is a pretty good recipe for making power and being able to put it down effectively. Unfortunately, getting those awesome conditions around here that just so happens to also be on a Thursday night when the track is open is rare. This Thursday is looking like it'll be in the +2,000ft DA region, which will be very similar to the two nights I've run so far this year. Good for an A-B comparison, but unless I drastically improve my driving, I'm guessing I'll have another handful of 11-second time slips.

    I've seen the general rule of thumb that for every 100 pounds you lose in race weight, you improve your e.t. by about 0.1 seconds. I've also seen people correct for the density altitude - that one is somewhere between 0.08-0.1 seconds improvement for every 1,000ft decrease in DA. Again, it all sounds good on paper, and would maybe make me feel a little better about what the car could run, but at the end of the day, I can only show my time slips as proof of my accomplishments, and those ain't changing. Yes, the one to two tenths I need to get into the 10s could probably be accounted for with those two factors alone, but the 60' times are where I stand to benefit the most by far in my estimation.

    The more I do this, the more respect I have for anyone that can pilot a manual car into the 10s. Some even make it look easy, but apparently I'm just not one of those guys. My response to anyone that asks "what does it run" when I'm at the track usually gets something along the lines of "It is a 10-second car with an 11-second driver."
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  3. #53
    Enthusiast Patentlaw's Avatar
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    I think you are being too hard on yourself. It is a rare bird that can actually drive a car to the maximum potential. And, generally, for those that do, mechanical problems are usually encountered. That being said, I would agree that working on your launch is the best solution to the issues that you present. It presents the biggest source of error. Really when you look at it, after the shifting, it is all just physics. Not much you can change.

    Since you went into such great detail on the analysis, I just wanted to put in my two cents to get that "perfect" run. I am anticipating that others will pull up this thread in the future and it will be a treasure trove of "this is how you do it" to get to 10.

    Heck....on a different prepared track, you could be well into the 10's and you would be "proud" of what you accomplished. Just that factor alone can make the difference.

    These are the threads that make this website worth while.........people can see and build off of the experience.

  4. #54
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    I will not argue on being hard on myself, sometimes to an unhealthy level. I think my frustration is compounded by my relative lack of access to the track itself, outside of paying $5k+ for a private track rental.

    I will say that the car itself, with what's been done to it, has been 100% reliable - the possibility of breaking something never really crosses my mind anymore when it's go-time. The upgraded axles and the Nth Moto clutch have never skipped a beat. I'm sure my missed shifts have not done the transmission any favors, but it has taken the beatings without issue to date. I'm sure I will end up having to look at a rebuild over the next few years if I keep this up, but I'll cross that bridge when I get to it.

    I'd never personally recommend a Viper for drag racing - there are way cheaper options to go faster, easier. But there's something cool about being the only one there at the track, and receiving pretty much universal praise for even attempting to do something other than just letting it rot in my garage. There's a lot of Viper fans out there of all ages - even some younger kids know exactly what it is. That's what keeps me coming back for more.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  5. #55
    Maybe try the TKO ThrottleMax in the mix.
    I think its done wonders for my launches and smoothed out my shifts.
    2008 Viper SRT-10 Very Viper Orange Coupe * The Orange Lure (Black On Orange)
    2015 Porsche - Mid-Engine Cayman w/PDK / Black * The Black Caiman (Orange On Black)

  6. #56
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    Quote Originally Posted by Patentlaw View Post
    I think you are being too hard on yourself. It is a rare bird that can actually drive a car to the maximum potential. And, generally, for those that do, mechanical problems are usually encountered. That being said, I would agree that working on your launch is the best solution to the issues that you present. It presents the biggest source of error. Really when you look at it, after the shifting, it is all just physics. Not much you can change.

    Since you went into such great detail on the analysis, I just wanted to put in my two cents to get that "perfect" run. I am anticipating that others will pull up this thread in the future and it will be a treasure trove of "this is how you do it" to get to 10.

    Heck....on a different prepared track, you could be well into the 10's and you would be "proud" of what you accomplished. Just that factor alone can make the difference.

    These are the threads that make this website worth while.........people can see and build off of the experience.


    Totally agree with all this. .04 could be as simple as a change in wind direction.
    Steve M, it's great to see the detailed analysis that you are putting into this though. Great work.
    Last edited by RT SERPENT; 10-25-2020 at 10:54 AM.
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  7. #57
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    Event: Thursday Night Test & Tune
    Date: October 22, 2020
    Location: Kil-Kare Dragway (Dayton, OH)

    The highlights:
    - Got a new personal best, but still not a 10 second pass
    - Weather was not great; it was warm, and really humid towards the end of the night (88%)
    - Found my missing HP; as suspected, it was in the tune. I reverted back to the old tune from 2019 - my traps went up even in the not-so-great air, which is what I thought should have happened with the Hoosiers
    - Track prep was exceptionally good - they had a private rental earlier that day. It was better than I've ever seen it, but unfortunately I was not able to take advantage of it.
    - I was full street trim, including my subwoofer (+30 pounds). I got tired of not being able to listen to decent music on my way to/from the track. It probably cost me my 10-second time slip.

    As always, my mods with differences highlighted:

    Power Mods: Metallic Substrate High Flow Cats; Gen 5 Intake Manifold; HPTuners custom tune (reverted back to my 2019 tune)
    Supporting Mods: AEM 30-0300 Wideband O2 Sensor; DSE Heat Shield; DSE Closeout Panel; MCS Shocks; TDS Level 5 Axles; Ecliptech Shift Light; Parking Brake Cable Relocation Kit; Nth Moto Triple Disc Carbon Clutch; Moroso Spark Plug Wires; Line Lock; Metal Throttle Bodies
    Tires: Hoosier DR2 (335/30-18), set to 20 psi hot mounted on Forgestar F14s (18x13 rear, 18x11 front)
    Rear Gears: 3.55
    Race Weight: ~3,600+ lbs - I was around 5/8 of a tank of gas that night.

    I ended up making 3 passes total. The results (right lane for all 3):



    My 2nd pass was the best race I've ever had, and was my best pass to date (even with the crappy DA). It also happened to be against a cool car - a 2012 McLaren MP4-12C. Earlier this evening, I stumbled across the YouTube video someone shot at the track last night (my race starts at 1:37):



    The McLaren got the win light by .0349 seconds, but it was a damn good race. I'll have to upload my GoPro footage when I get a chance so you can see what I was doing in the Viper, which pretty much amounted to losing ground on each shift as I expected would happen against a dual-clutch equipped car.

    As you can tell from the trap speeds on the slip, he clearly has the faster car. He did not use launch control, and he was totally stock on street tires. If he had used launch control, I would have been chasing him rather than what happened - him chasing me down at the end. The guy was really cool, and had only owned the car for 5 weeks. He's the one that suggested the race, so we made it happen. The 570S you see at the beginning of the video was running somewhere in the 10s @ 137 according to the driver (it was tuned).

    All in all, it was a great night - the race with the McLaren made my whole year. Which is good, because next Thursday night is the last night for test and tune this year, and it looks like it is gonna rain. Maybe next year...

    I'll update this thread when I get my GoPro footage edited.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  8. #58
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    The same guy caught my 3 runs from last October, and the 3 runs from the other night and put it all in one video:



    You can see the car go into limp mode on the first race against the blue Corvette due to the camshaft position sensor issue I was having last fall. I still have all the GoPro footage from all of these runs, just never edited them. Much more interesting watching the car from the outside.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  9. #59
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    Density Altitude Discussion

    It's winter, and I'm bored, which means it is time for me to organize all of the data I've gathered over the past year into something that's easier to digest. I like spreadsheets (I have a lot of them), and I have the time, so why not make one more? This time, I decided to focus on density altitude.

    Earlier this year I bought a Kestrel 5100 handheld weather meter so I could directly measure density altitude at the track. While not cheap, it seems to be the standard for being able to get quick, accurate density altitude data. It's really only important if you are a serious racer (i.e. not me), so while it was probably not the wisest decision, what's done is done.

    I only had it for my last two outings to the track this past year, but I was able to use it to gather data from 5 different passes on 2 different nights. Out of curiosity, I decided to compare the readings to a couple of the more well-known websites that gather and archive density altitude data for tracks around the country:

    DragTimes - http://www.dragtimes.com/da-density-...calculator.php

    Air Density Online - https://airdensityonline.com/us-track-list/

    DragTimes has archived weather data dating back to 2015; Air Density Online has archived data back to 2016. I've always considered the DragTimes database to be the gold standard, as it is the one you see most often quoted on different forums. It is also the database behind most of my DA data for the 32 passes I've made to date at my local drag strip over the past few years.

    So how accurate are those databases compared to the Kestrel 5100? Sometimes pretty close, but other times not even in the same ballpark:



    My Kestrel (truth source) readings are in red, DragTimes archived data from the same date/time in blue, and Air Density Online data in green. I wouldn't expect them to be identical, but some of them are way off, upwards of 500-600 feet compared to the Kestrel readings. On average, the DragTimes data was better - averaged over the 5 data points, it was 169 feet off. The Air Density Online data was around 287 feet off. Clearly 5 data points isn't enough to assess trends, but still, I didn't expect them to be that far off. After some poking around, I've seen others claim that online databases can be off by as much as 1,000 feet...now I can see why.

    As a general rule of thumb, every drop of 1,000 feet in density altitude is good for about 0.1 seconds off your elapsed time and about +1 MPH added to your trap speed (it's rough, but close). As a reference, people that run record times generally run in negative DA conditions (a.k.a. mineshaft air), sometimes as low as -1,000 feet, possibly lower. Average conditions at my local track during the driving season will put you around +2,500 feet; a good night will be around +1,000 feet; a great night (rare while the track is still open) will be down close to 0.

    What is Density Altitude (DA), and why does it matter?

    Before this, I couldn't really answer that question. That led to hours of reading through some very dry documents while trying to piece everything together. I'll try to summarize what I learned so you don't have to spend hours retracing my steps.

    Density altitude is a function of the track's elevation, the barometric pressure, the ambient air temperature, and the humidity. It is not the actual altitude, but rather an apparent altitude adjusted for the variables listed. The lower the density altitude (denser air), the more power your engine can make (i.e. low DA = good). Each variable's effect on the density altitude is fairly intuitive, except for the last one (at least for me):

    1. Lower elevation = lower DA (makes sense)
    2. Higher barometric pressure = lower DA (sure)
    3. Lower temperature = lower DA (check)
    4. Higher humidity = higher DA (as in, less dense - say what now?)

    I've always felt that really humid air seems thicker (at least when I'm running in it), but the opposite is actually true. Don't think about it too hard; just press the "I Believe" button and move on with your day.

    So now we need a reference. People often like to correct their numbers (horsepower, e.t., or trap speed) back to a "standard day" just to make it easier to compare apples-to-apples. There's an international standard day definition that's captured in ISO 2533:1975, but I didn't feel like paying $185+ to read it. The US Standard Atmosphere definition, published by NASA in 1976, was a little easier to come by (https://ntrs.nasa.gov/api/citations/...9770009539.pdf). The relevant values for a standard day from that document are listed below:

    1. Elevation = 0 feet (sea level)
    2. Barometric Pressure = 29.92 in Hg (inches of Mercury)
    3. Temperature = 59°F
    4. Humidity = 0%

    Barometric pressure can be a bit tricky, so be careful. The barometric pressure you see reported in your standard weather feed is actually a corrected value as if it was measured at sea level. You can read more about that here: https://www.weather.gov/bou/pressure_definitions As I'm writing this, the corrected (mean sea level) barometric pressure in Dayton is 29.94 in Hg. The uncorrected or "station pressure" value where my house actually sits (@ 986 ft elevation) is 28.89 in Hg. Most online weather databases report barometric pressure values corrected to mean sea level, but devices like the Kestrel 5100 report the pressure uncorrected, so keep that in mind. Also keep in mind that pressure when measured in inches of Mercury changes with the ambient air temperature (it goes up as temperature goes up, and vice versa).

    So why are the online databases so different from each other, and why don't either match up all that well with measured data from my handheld weather meter at the track? There are a couple of reasons.

    First, the two databases don't agree on the track elevation. Air Density Online reports a track elevation for Kil-Kare of 803.8 feet. DragTimes says it is 910 feet. Which one is correct? Technically neither...the US Geological Survey database (https://viewer.nationalmap.gov/theme/elevation/) says it is 813.13 feet. In this case, Air Density Online is closer, and is just on the edge of the error bounds of the USGS data (~10 feet). I'm not sure where DragTimes gets their elevation data, but it isn't even close. I checked a couple of other tracks around the country, and the elevation numbers were much closer among the three sources, so that problem could be unique to Kil-Kare.

    The larger issue is that both databases gather weather conditions from weather stations that are likely not even remotely close to the track. How far away they are is anyone's guess...I couldn't figure it out, and I'm not even sure the folks that own those websites would be able to tell me. DragTimes says their data is "obtained from an airport near the track", but does not specify which one that might be. Air Density Online gets their data from Dark Sky, which does not reveal sources. The temporal resolution of the data for each site is also only in one hour increments, so if you make a pass around 7:30PM, your actual DA value is going to be somewhere between the 7PM and 8PM readings, further complicating things.

    Bottom line: if you really want to be able to compare your runs at the drag strip to others, especially if they are on different days and at different tracks, you need to know the density altitudes at the times/places when each pass was made. If you are relying on an online database for that information, it could be way off. Based on what I've seen from my own DA data (most of which is from online sources), I can't even really compare the different passes for my own car.

    Even if you have the actual DAs, I'd still take it with a grain of salt...if you want to have a pee pee measuring contest with time slips, you really just need to just line 'em up and see who comes out on top. Anything else is pure conjecture.
    Last edited by Steve M; 12-17-2020 at 01:45 AM.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  10. #60
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    Finally got around to editing the in-car footage of the race vs. the McLaren MP4-12C:

    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  11. #61
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    Nice run Steve , and impressive seeing a stick car faster than a McLaren...
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  12. #62
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    This a cool thread. Seeing that 11.02 time slip tells you there's a 10 in there. I know Steve won't let up on himself, but there's also a 10 second driver in the mix!

    Shifting gears a bit, some pun intended, I only took mine to the track once. The fastest time it ran was my first one. The next two were slower, and I drove home.

    I know me > If I start chasing something, I'm not going to stop. I sometimes (not always) regret the money it consumed. Steve is on a mission, and I respect that!

  13. #63
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    Any more runs since October? Another few hundreds off of that 60' and your 10-second pass is there.
    Ryan - 14 Stryker Green Nth Moto TT/Heads/Cam
    Past - 14 Stryker Green VE Stage II Heads/Cam, '16 ACR-E, '14 Anodized Carbon, '14 TA, Orange '03 Paxton vert w/coupe rear, Black '06 coupe w/SSG accents

  14. #64
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    Quote Originally Posted by J TNT View Post
    Nice run Steve , and impressive seeing a stick car faster than a McLaren...
    Thanks...I didn't know anything about the MP4-12C before hand, but I had at least seen his first pass so I knew it would be a pretty even match. Pretty sure he would put 1-2 car lengths on me from a roll on the street based on what he was trapping.

    Quote Originally Posted by Gen3CoupeTX View Post
    This a cool thread. Seeing that 11.02 time slip tells you there's a 10 in there. I know Steve won't let up on himself, but there's also a 10 second driver in the mix!

    Shifting gears a bit, some pun intended, I only took mine to the track once. The fastest time it ran was my first one. The next two were slower, and I drove home.

    I know me > If I start chasing something, I'm not going to stop. I sometimes (not always) regret the money it consumed. Steve is on a mission, and I respect that!
    I'm not short on ideas to get there...I already added an underdrive pulley back in November after the track had closed down. The tune is pretty spot on, but I might try to find a few more tweaks this year...at this point, I'm splitting hairs with this setup. The car clearly makes enough power to get there...just gotta get it off the line better. I have a couple ideas there as well.

    Quote Originally Posted by 98intrigue View Post
    Any more runs since October? Another few hundreds off of that 60' and your 10-second pass is there.
    Unfortunately not...that ended up being the last test and tune of the season up here. The earliest the track will reopen this spring might be sometime in April, but the weather around here usually ends up being a craps shoot until May.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  15. #65
    Enthusiast Vipervin's Avatar
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    This is a great thread. It's rare to see someone provide such great documentation of their experience modding...especially over an extended period of time. Very helpful.

  16. #66
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    I'm glad you find it helpful...sometimes I go back and read through everything just to remember the journey.

    I swore to myself I wouldn't mod this car to the point where it was no longer fun to drive. It happened with my last car, and it really took the joy out of driving.

    I even sorta remember the conversation I had with my wife right before I bought this car:

    Her: And you aren't going to want to mod this one?
    Me: Absolutely not. This car is perfect just the way it is.
    Her: Are you sure?
    Me: Oh yes...I won't make the same mistake twice.

    Obviously I didn't hold up my end of the bargain, but I have a very understanding wife. It's a slippery slope, but I do try to keep it reined in. Sometimes.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  17. #67
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    Event: Thursday Night Test & Tune
    Date: September 9, 2021
    Location: Kil-Kare Dragway (Dayton, OH)

    The highlights:
    - Still no 10 second pass, but it was a new setup, so it was to be expected
    - Weather was not great; it was warm and humid with a slight headwind
    - Had an issue getting into 2nd gear on 2 of my 6 passes, which has never happened before
    - Cut the best 60' time I've ever had (1.67 seconds), but it was unfortunately on a pass where I missed 2nd gear

    Mods this time with differences highlighted:

    Power Mods: Metallic Substrate High Flow Cats; Gen 5 Intake Manifold; HPTuners custom tune (mine)
    Supporting Mods: AEM 30-0300 Wideband O2 Sensor; DSE Heat Shield; DSE Closeout Panel; MCS Shocks; TDS Level 5 Axles; Ecliptech Shift Light; Parking Brake Cable Relocation Kit; McLeod RST Clutch; Moroso Spark Plug Wires; Line Lock; Metal Throttle Bodies; Underdrive Pulley
    Tires: Hoosier DR2 (335/30-18), set to 24-22 psi hot mounted on Forgestar F14s (18x13 rear, 18x11 front)
    Rear Gears: 3.55
    Race Weight: ~3,650+ lbs - I was a bit heavy starting with 3/4 of a tank of gas that night, the substantially heavier clutch assembly (+22 lbs), and subwoofer still installed (+30 lbs).

    I ended up making 6 passes total. The results (right lane for all 6):



    And an Excel screen capture that's a bit easier to read, including the Density Altitude readings from my Kestrel 5100:



    So the biggest differences this year were the addition of an underdrive pulley and the swap from the Nth Moto carbon triple disk clutch to a McLeod RST, which is their street twin that bolts to the stock flywheel. Anyone that has shopped for clutches knows that the Nth Moto clutch isn't cheap at over $4k, so swapping to something seemingly inferior was not a decision I made lightly. I spent the winter mulling the idea over...in the process of doing that, I went back through this thread and this quote stuck out to me:

    Quote Originally Posted by TrackAire View Post
    Regarding your clutch, nothing aftermarket that is like an on/off switch is going to work great at a prepped launch pad. IMO finding a very durable organic clutch (maybe even stock) that you can slip the crap out of and just look at it as a consumable part that you'll need to replace every 12 runs or so. Also, figure out how to keep your clutch fluid as cool as possible to keep it consistent for good launches.
    The Nth Moto clutch can be slipped just fine on the street, but get some heat into it, and it just grabs. Unfortunately, the lower rotating mass combined with my porky Gen 4 caused my car to fall on its face even with some 5,500 RPM dumps out of the hole. I was beyond frustrated. I knew I wanted to try something heavier, which the McLeod certainly is - pretty much identical to the stock clutch at 61 lbs vs. 39 lbs for the Nth Moto. As I said above, it just bolts to the stock flywheel - it has its own flywheel, so you don't have to resurface anything; it just bolts in place and off you go. The install was SO much easier, which was nice for a change. Here's a quick pic:



    The flywheel looks used because it is - I ended up keeping my original around just in case I ever wanted to do something like this. The clutch drives like a dream on the street - very smooth engagement, and shifts are like butter. You notice the extra mass, but it isn't all bad - it makes for smoother low RPM driving and much easier take offs. Overall, I was pleased with the decision.

    At the strip, I think it was a step in the right direction - I cut two of my best 60' times ever (1.67 and 1.74), but getting locked out of 2nd gear a couple of times was definitely cause for some concern. Did I get the clutch too hot, or was I just hammering it into 2nd too hard? After the 2nd time, I almost decided to call it a night, but I'm glad I kept going because I ended up getting a few more clean passes, which gave me confidence that I didn't hurt anything too badly.

    Obviously I didn't reach my goal, but it was a good night for shaking everything down and clearing out the cobwebs. My driving was just off all night long, but that's what you get for not doing something for a while.

    On a positive note, I ended up upgrading my action cam from a first generation GoPro to a GoPro Hero 9 Black. Man what a difference in the quality of the footage, especially in low light conditions:



    ...and zoomed in a bit:



    I also got to exercise the gauge display that was part of last winter's double DIN head unit install: https://driveviper.com/forums/thread...l=1#post432427

    I now have a good way to monitor the IATs (which got to over 100° on a couple of passes even in 78° weather) as well as ECT, RPMs, Timing Advance, and MAP:



    It doesn't help when I'm concentrating on the pass, but my new GoPro has good enough resolution that I can read it well enough on the replay to get a good idea of what's going on.

    I also added a Dragy to capture 0-60 and 60-130 times:





    I now have lots and lots of data to go through after every pass. It's a bit overkill, but I still find it interesting. More on that a bit later.
    Last edited by Steve M; 10-10-2021 at 08:08 AM.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  18. #68
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    Lots of great information and detail Steve , thanks for sharing!
    Love your approach.
    Charter Member ,

  19. #69
    Quote Originally Posted by Steve M View Post
    You're knocking on 10's door!

    Hey maybe add a little air to them tires!

    Quote Originally Posted by Steve M View Post
    but getting locked out of 2nd gear a couple of times
    Sudden Skip Shift? I'm a dork just grabbing at straws.

    Quote Originally Posted by Steve M View Post
    Great pic of your new McLeod RST!

    Here's mine ..before being mounted.
    RST_small.jpg
    Didn't get a pic of it installed.
    2008 Viper SRT-10 Very Viper Orange Coupe * The Orange Lure (Black On Orange)
    2015 Porsche - Mid-Engine Cayman w/PDK / Black * The Black Caiman (Orange On Black)

  20. #70
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    Quote Originally Posted by viperBase1 View Post
    You're knocking on 10's door!
    I've been knocking on that door for years. I'll get there, or I'll put my foot through the firewall trying.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  21. #71
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    Event: Thursday Night Test & Tune
    Date: September 30, 2021
    Location: Kil-Kare Dragway (Dayton, OH)

    The highlights:
    - The weather was great - it started out warm, but a high pressure system had just moved in, the humidity was noticeably lower, and there was a slight tail wind that night (rare)
    - Yet again had an issue getting into 2nd gear on 1 of my 4 passes (starting to see a trend here?)
    - My 60' times were disappointing all evening; I thought I had learned a lot about launching with the new clutch during my last outing, but I was oh so very wrong

    Mods this time with differences highlighted (no major changes since 9 September 2021):

    Power Mods: Metallic Substrate High Flow Cats; Gen 5 Intake Manifold; HPTuners custom tune (mine)
    Supporting Mods: AEM 30-0300 Wideband O2 Sensor; DSE Heat Shield; DSE Closeout Panel; MCS Shocks; TDS Level 5 Axles; Ecliptech Shift Light; Parking Brake Cable Relocation Kit; McLeod RST Clutch; Moroso Spark Plug Wires; Line Lock; Metal Throttle Bodies; Underdrive Pulley
    Tires: Hoosier DR2 (335/30-18), set to 24 psi hot mounted on Forgestar F14s (18x13 rear, 18x11 front)
    Rear Gears: 3.55
    Race Weight: ~3,600+ lbs

    I came up with a new way to estimate my race weight based on the last time I had it on the scales (should be within about 20 pounds or so of reality), and I also put some time into making some better graphics that show the weather conditions as well as how much gas I had during my first and last passes of the night:



    I put more time into that than I'd care to admit.

    I ended up making 4 passes total. The results (right lane for all 4):



    The Excel screen capture including the Density Altitude readings from my Kestrel 5100:



    Dragy 0-60 times:



    Dragy 60-130 times:



    At this point, I was starting to suspect my issue with missing 2nd gear (and only 2nd gear) was related to trying to powershift first to second gear. By the 4th run, I was granny shifting 1-2, and that seemed to fix that problem (but it won't be the last time you'll see this problem rear its ugly head...).

    I was really digging the 60-130 time on my last pass (7.55 seconds!) - that was the result of powershifting 3-4. It makes all the difference with the 60-130 times, and also seemed to help with the trap speed as that was my highest ever at 130.89 MPH, even with the heavier clutch assembly.

    Video of that pass (note the much better video quality thanks to a GoPro that was made during this decade):



    Aside from the shifting issues on the 2nd pass, I felt like I was starting to get a good feel for the new clutch. Little did I know that the honeymoon would end a short couple of weeks later...
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)

  22. #72
    The acceleration trace on the Draggy doesn't make sense to me The Speed trace is linear but the acceleration trace is variable??

    Quote Originally Posted by Steve M View Post
    Aside from the shifting issues on the 2nd pass, I felt like I was starting to get a good feel for the new clutch. Little did I know that the honeymoon would end a short couple of weeks later...
    What does "the honeymoon would end a short couple of weeks later" mean exactly?
    Did the McLeod RST fail in some way?
    2008 Viper SRT-10 Very Viper Orange Coupe * The Orange Lure (Black On Orange)
    2015 Porsche - Mid-Engine Cayman w/PDK / Black * The Black Caiman (Orange On Black)

  23. #73
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    Quote Originally Posted by viperBase1 View Post
    The acceleration trace on the Draggy doesn't make sense to me The Speed trace is linear but the acceleration trace is variable??
    It's an artifact of the scale and the units it is showing. Referencing the 0-60 times above from September 30th, look at run #2. Notice where the blue line (speed) goes flat - I'm still going ~50 MPH, but I'm no longer accelerating because I couldn't find 2nd gear with two hands and a flashlight. The yellow line (acceleration) shows a corresponding dip (down to about 0 g's of acceleration).

    The 60-130 plots are similar - the dips in the yellow trace line up with where the blue lines go flat for a fraction of a second. The first dip in the yellow line on those plots represents the 2-3 shift (around 70-ish MPH), and the second dip shows the 3-4 shift (around 100-ish MPH). The fastest shifting cars will have a smooth sloping blue line with tiny blips in the yellow trace. Longer dips (left-to-right) in the yellow line = slow shifting =

    If they changed the scale, the yellow line would look a bit less noisy, but you'd also lose a little bit of the sight picture it offers. Take a look at this thread in the Gen 5 section - lots of plots and videos to compare against: https://driveviper.com/forums/thread...ph-times/page4

    Bottom line: all this stuff is happening so fast that I can't tell the difference between a 7.7x and a 7.5x 60-130 time. I don't get a chance to check after each run until I'm back in the staging lanes getting ready for my next pass, so it's always a bit of a surprise to see how I did. That's also why I take video footage of each of my quarter mile passes - I watch them over and over again to see what I did right and wrong so I can learn. It's amazing how much stuff you miss in the heat of the moment. Start to finish a run takes about a minute, the last 11 seconds of which is pretty frantic.

    Quote Originally Posted by viperBase1 View Post
    What does "the honeymoon would end a short couple of weeks later" mean exactly?
    Did the McLeod RST fail in some way?
    Putting that story together now...
    Last edited by Steve M; 3 Weeks Ago at 10:15 AM.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes - 1/4 Mile Passes (YouTube)
    High Flow Cats | Gen 5 Intake Man. | UDP | HPT | 3.55s | MCS | DSS Axles | Nth Moto Clutch | 11.027 @ 130.06 (Vid), 1.78 60' (+1,622 ft DA, w/ 3.55s & Hoosier Drag Radials)


 
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