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Old 10-16-2020, 01:07 PM   #1
IROCZman15
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Determining best launch and shift points, using math and datalogs

Not expecting everyone to bust out their calculators and notepads to crunch numbers, but if anyone with a bunch of drag racing experience had any scientific knowledge that they might care to share, it would be very much appreciated! I'm aware, none of this is exciting to dive into, but perhaps myself (or someone else in the future) can see this stuff and learn from it.

My goal is to scientifically use the datalogs and timeslips I have got in the past 2 months to help me truly dial in my launch and my shift points so that I can best optimize everything for the quickest N/A drag passes possible. I have the WOT tune dialed in to near-perfection and the WOT timing is staying at 35 deg, with a 12.5 target AFR at torque peak and a 12.7 target AFR for hp peak. Dyno sheet is from February when the engine was built. For full blown details on the car see my build thread: http://www.njfboa.org/forums/showthread.php?t=69033 but essentially it is a sbc 406 with a 3,400 9.5" converter, probuilt 700r4 and a moser 12 bolt with 3.55 gears. I run MT ET street SS drag radials at the track, and do have a multi-use setup of suspension parts because the car also does street driving and autocross.

videos of my runs can be found at my youtube channel in case it clears up when i am shifting and how the launch/shifting looks and sounds: https://www.youtube.com/user/IROCZma...=dd&shelf_id=4


For the Launch:

Through trial and error, I have determined that the car launches the best with a soft rear shock setting and the drag radials at 19psi. Leaving off a 920ish idle has worked well, but I am not scientifically sure that that makes sense. I do not have a trans-brake, so when I try to foot brake, my brakes don't hold past 1,700-1,800 which is when I start to creep forward through the beam. I have a line-lock but have never tried launching off of it at the track, but when I experimented on the street with it, it seemed slow to release the front brakes. I would love to cut a low 1.6x in the 60 foot so if anything jumps out on this chart I made, feel free to shout it out to me. The car is in 1st gear until way past the 60' cone, so that takes any shifting variables out of the equation.







For shifting:
Launching from idle and only needing to make the 1-2 and 2-3 shift during the 1/4 mile is good. I am making both shifts prior to reaching the 1/8th mile so the back half of the track is just climbing up 3rd gear. When it comes to shifting and revving each gear out, I have yet to determine what is best. I know it has to do with not only how high to rev the engine, but also what rpm the shift lands at in the next gear. One school of thought is that you want the shift to land in the rpm where it is just climbing the peak of the torque curve. Another is to have the rpms land after the torque peaks and when the hp rpms are climbing. TYPICALLY, my shifts land right around the 4,700 rpm range of the next gear (with some variation based on how high I rev the previous gear). I have included my VE table (basically same shape/slope as the torque curve) as well as my engine dyno sheet. A chassis dyno won't help here because a dyno pull is only done in 1 gear (3rd gear for a 1:1 ratio).

So, I am crunching numbers and timeslips, but in an effort to optimize each shift I am wondering if I should shift the 1-2 shift at a different (lower) rpm than the 2-3 shift. I am NOT changing rear gear ratio, converter, trans, or any of that either. The rpms go real quick at the top of first gear, in fact when I do the datalog math, it takes only .33 seconds to go from 6,000 to 6,500 rpms in first gear. Obviously the rpms climb slower in 2nd gear, so I have more time to get that shift perfect, where the 1-2 gearshift can be off a few hundred rpms in just a tenth of a second.















I have reviewed all of my many datalogs too, and I can post screenshots of those also if needed. Mechanically the car is dialed in and probably really close to its limit/optimal performance without any big mechanical changes happening. I plan to go to Island dragway next Friday, Oct 23 and that might be the last drag day of the year for me. A 11.7x or even 11.6x second pass at 117 would make me super happy going into the winter time season and would put this car closer to where we all think it should be running for the hp/setup it has.
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Old 10-16-2020, 02:36 PM   #2
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this is way above my mental pay grade. But im sure interested in the results.
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Old 10-16-2020, 04:34 PM   #3
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Originally Posted by LS1ow View Post
this is way above my mental pay grade. But im sure interested in the results.
ha, its well above mine too!
that's why I am reaching out to anyone who has some wisdom and experience at it, I know there are a handful on this board.
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Old 10-16-2020, 04:41 PM   #4
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IMO there are too many variables. I'll donate my time to come to a a track rental with you to help you out the best I can.

IMO you gotta run a few runs as consistently as possible, then make *1* change, then run a few more times, then makes *1* change and run some more. Then you'd have good clean data to dissect.

Runs 1-5
Leave off idle, shift 1-2 at 7k, shift 2-3 at 7k

Runs 6-10
Footbrake as high as you can, shift 1-2 at 7k, shift 2-3 at 7k

Etc...
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and once i get PHB, what do i ajust it too?
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Old 10-16-2020, 05:49 PM   #5
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Another thought, I assume you have the converter spec'd for a 406 on nitrous?

If so, it may be too tight, combined with a too tall of a gear, which could explain why its dropping so low on shifts trying to couple.
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Old 10-17-2020, 03:17 PM   #6
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cool, thanks fellas. Yes, a track rental would be ideal. At the Test-N-Tunes I usually can only get 5-6 runs in. Aside from the Saturday June 5 TnT where I got 11 runs in. I experimented with launching rpms that day as well as with using my lockup feature on the converter, and that amount of runs was very helpful. You are right for sure, the more runs I have that are exactly the same, the better data "pool" I can have and then I can go changing things. I could have filled out the whole front notebook page with the amount of drag passes I have done this year ( which is 41 passes ) and listed all the data, but some of the passes during March, June and July had no relevance anymore, because during that time I was changing ignition timing, figuring out tire pressure and some other stuff. So I only put the most recent 2 month's worth of pertinent info onto paper. Unfortunately, it is all I really have to work with at this point.

Yup, converter was spec'd for this exact motor with nitrous. Sent the converter company the cam card, engine spec sheet, and a list of the other mods, weight, purpose of the car. I told him that the car will be getting nitrous in a year and he said, I can build the converter for that setup and it will be pretty good in the meantime. The goal was so I didn't have to remove the transmission and converter, then mail it back to him plus another $200 this winter just so he could reconfigure it for nitrous use. We opted just to have it done once and I understood I was leaving a bit of N/A performance on the table, but it meant that the car (and me) would be used to it after a year and then I could just leave it in the car this winter. It is probably too tight and thus effecting the shifts, so I am kinda wondering if I should revv out 2nd gear maybe to 6,600 and have it drop into 3rd gear somewhere near 5,000 rpms. First gear climbs just too fast (for me) to reliably shift at a dead accurate 6,300 rpms. In first gear it only takes .35 seconds to go from 6,000 rpms to 6,500 rpms. I'll get better at it, but I think revving out 2nd gear a little higher would land me at a better rpm in 3rd gear.

Won't be revving this engine to 7,000 thats for sure, but I think I will keep the rev limiter at 6,700 or so. Engine builder said to put my shift light at 6,100 and shift it between 6200-6300 with a 6500 rev limiter. He said that would be safe, but also understood I could go a little higher depending on my converter, trans, car weight, rear gear etc.

I had experimented with locking up the converter too during June, and that just caused the shifts to drop much lower into the next gear and the car was a dog. I have the ability to manually lock up the converter in 2nd, 3rd, and in 4th if needed, and this pulls the rpms down a few hundred rpm. It is a toggle switch (actually my old fog light switch on the dashboard) so its not near my shifter or steering wheel. If (on nitrous) I were to run out of rpm at the top of 3rd gear, my thought was to reach over and hit the lockup switch to gain a few more rpm out of 3rd gear, but since I am currently only crossing the finish line around 5,700 rpm I am not worries about that now.
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Old 10-19-2020, 07:26 PM   #7
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a friend sent me this link:

https://glennmessersmith.com/shiftpt.html


I put in the numbers I have from the engine dyno sheet and it is telling me to SEND IT higher into the rpms.







I am unsure with my mph is during the 1->2 shift, but I think the mph given by the calculator (86 mph) is pretty close, because I have usually shifted 2->3 just a little bit before the 1/8th mile cones, and I am typically trapping 91-94 mph in the 8th, so that number seems to mathematically make sense.

Additionally, if that set of mph numbers is correct, I will probably never need to shift into 4th gear even when on the nitrous because this calculator says I should make the shift to 4th around 140 mph... and it is very unlikely this car will get to 140mph in the 1/4 even with the 200 shot. So, keeping this rear gear ratio and tire height seems promising for the nitrous setup, while a switch to 3.73 might indeed put me too deep into 3rd where I would have to shift into 4th (on the bottle).
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Old 10-21-2020, 05:04 PM   #8
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Hereís another of my novels!

There is allot to talk about, and Iím going to make some assumptions,
You are missing a bunch of factors and things you need to consider if just trying to go fast ( as opposed to trying to bracket race), Your on the right track, but it is not that simple. As already said, you have to take in the air temp barometric pressure. Major factor in your ET. And it will change as the day progresses.

Engine / trans temp can affect your ET. When youíre testing, you want to not hot lap the car, but being slightly warm may not be bad. But a hot trans can affect how it shifts. (I would suggest you add at least engine temp to your logs). If the track will allow it, ask if you can make 2-3 60í hits in a row:

Launch - backup, launch - backup, launch, and on the last launch just go easy down the track ( because the trans/convertor will be really hot). But this could let you know if/how temp effects your launch / 60í.

Looking at you logs the first set you made 6 passes at night, so I assume they were pretty close together, I would guess that either the trans was getting hot or the track was starting to go away based on the earlier runs and launch PRMs or both. I would assume the starting line was just getting bad more than the car / your changes.
So pay attention to the starting line and try to find the best groove and stay away from bald spots. Also some tires like being in the glue, others like the groove, or the track being dragged. Play with this as well.

Track conditions and prep is going to be a factor, not only wheel spin but how much grip the entire track has. This could be a big factor when testing on different days and tracks. And what others are running. Street tires do tend to kill a track surface more than slicks will. A good sticky starting line will help your 60í, even launching at the same RPM and even if you are not spinning, the car will react faster. But if the track is real sticky down track, it can affect how the suspension unloads and/or ET as the tires have to pull out of the glue/ sticky track surface. This is going to change the performance of the car allot. Say the track is prepíd for Promods your car would not run as fast. In cars without allot of HP they think they are spinning or rattling their tires, but itís the track having so much grip the car is struggling to pull out of the glue. Iíve even seen this happen to 10 second/big tire cars. Track grip is more than just the starting line and will affect your ET. Look at the track surface, the sides of the groove may not be glued as much as the center, move off to the side a bit once you get into 3rd gear, either towards the center or towards the wall. Donít try to hug them! Just get the tires to where the track isnít so sticky, could get you a few thousands.

So take all this into you logging. You need that in your data so you can connect it to each run record. Also car weight, every 100lbs you take out of a car is generally good for a 10th. So having a ľ tank of gas as opposed to a full tank will help a little. ( the added weight might help the tire hook off the line?) But for ET, take as much weight out of the car as you can. Basic rule is that for every .10 you drop your 60' will drop .20 off the top end. So 10 off the start is 20 off the finish line / ET. (If your N/A - power adders can take .30 off the top ).

You logged rear tire pressure Ė what about front tires. I assume you arenít running skinnies/ front drags. If so, put your front tires to 45PSI, lower the rolling resistance a bit Ė could get you a 10th or more.

Somewhat unrelated? One other thought is fuel. I assume you are running high octane pump gas? Are you using any octane booster? Canned octane seems to vary allot. Even with my street tune my car will pick up 40 and 3-4 MPH if Iím running on race fuel (100 oc unleaded) as opposed to pump gas. Do you have knock sensors, have you checked your not getting any knock that is pulling timing?

It is a bit odd your car does seem to like launching that low. How old are the tires? How many passes? Big burnout can overheat the tire and make them ďgreasyĒ and over time that heat can effect the sidewalls and how well the car is hooking, even if the tires donít show allot of wear. But it does seem like the suspension isnít working? Have you tried changing pinion angle? I would think you should be able to hook at higher RPMs, unless itís all about the condition of the starting line itself. If there are allot of street tires during T~n~T they are going to destroy the starting block. AND DO you have a front sway bar? If you do remove it so the car rocks back to help plant the tires better. And youíll find that you then need to go stiffer in the rear?

AS far as the pass itself:
You need to start with staging the car. You have to make sure you are staged in the same place. Either shallow (You want to just flicker the stage beam ) or Deep ( turning off the pre-stage beam ) There is 6-7" of rollout that will effect everything. Shallow (Think of it as a getting a running start out of the stage beam. ) Deep Ė gets you closer to the finish line. Try both leaving the same RPM and see which gives you the best 60í/ Most likely shallow staging. But be consistent. If you staged shallow one pass, and deeper the next, your data is not valid. Since you are just looking to get your best ET, I would guess that shallow staging is what you want.

Once you have determined which staging works best for you, then focus on RPM launch to 60í. Once you know what creates the best 60í, then you can start working on shift points. One point here, you said when you try to footbrake your brakes donít hold? Are you sure itís your brakes? If the starting line is bald from front wheel drive cars your front tires could be sliding on the bare starting line. And trying to use the line lock is just going to make it worse.

Once you get the 60ís to be low then look at the 330. I assume you are in 2nd by the 330. So start making passes short shifting ( maybe 5400 RPMs ) then move up until you get the best 330í. As you noted shift points and RPM drop. Do this because you want to shift based on torque as well as RPM. Torque gets the car moving by twisting the drive shaft, HPs get the MPH by spinning faster. You want to stay near/above your torque peak. Spinning too high could actually hurt you as shifting to low does dropping out of you torque curve. Looking at your dyno your torque drops over 6,000. So for your 1-2 shift - short shifting might help? Your 2-3 shift will be less effected as your have the weight of the car already accelerated and moving forward. Remember your acceleration between the 1/8 and ľ is minimal. Youíll make up the most time in the 1st half of the track.

Few other comments: All cars move around ( I mean ET wise ), the basic rule is as much as .08. So a slower car can pick-up/fall off more than a faster car. You could make 2 identical runs ( starting line position, RPMs, shift etc ) and still end up with different ETs.

So again, Donít always change things after just one run unless the change throws things way off ( like spinning the tires, or large change in ET ), and if that happens go back to the prior run and test again. If you make a pass and you get good results, make the same pass again to make sure you replicate the results. The car has to repeat before you make changes.

I would suggest making or buying a data logging book that you can make all these entries in. If you have a smart phone, there is probably a good weather App that can be a cheap weather station to get barometric pressure and determine your elevation. A Few hundred feet difference can be a factor. As an example, even with good track prep, and fairly similar weather temps my car runs different at various tracks. Numidia (slower Ė high elevation), Island ( I call this in the middle ), Acto ( lower elevation) Between the 3 there can be up to 1,000í elevation difference and my car will be .40 and 6-7 MPH off. So if the air isnít good the car is just not going to make power.

Good luck.
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Old 10-22-2020, 12:04 AM   #9
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What an awesome writeup! Much thanks. This is way more than I expected anyone to write, and I really do appreciate you typing it all out. I'll reply in the order your comments/questions were typed, so that it can all flow properly.


If you wanted to see my actual datalogs for real, just click through some of the recent pages on my engine build thread. I take a phone screenshot of each datalog, and I post it right with the GoProvideo and timeslip of that pass. I just included the hand-written info above as a cliff-notes version of my datalogs. http://www.njfboa.org/forums/showthr...t=69033&page=9
-Yes, I have been tracking weather conditions at the track each time I go. I use the $5 Summit Racing "Drag Racing Log Book" and also use a few phone apps to track the weather conditions each time. For consistency, I use the weather data from the (That Racing Channel) TRC app when compiling my log-books. I have come to learn from experienced racers that a 150 foot change in the DA will result in a .01 change in my ET.

- I have had only one day during this year where the track was not too crowded and I was able to hot lap the car. It was on Saturday June 5th and I made 11 passes in 3 hours...and the last 6 passes were all within 1 hour, some only a few minutes apart. Also, I do have engine temperature data in the datalogs, it is the CTS sensor on the datalogs, I just usually glance at the values, but don't keep the datalog trace on for viewing unless I see it is "not within a normal range" This engine stays very cool, and trans temp is usually 160-170 during a racing day. I have two trans coolers, one in the radiator and the other behind the frotn bumper where air deflected up from the front air-dam passes over it

-That idea of the several repeated launches back to back would be awesome. If I had a chance to get in on a track rental I would do that for sure. Very doubtful that Island or Atco would let me do that, as I've never seen anyone else do it at a Test-N-Tune day. Usually too many cars in the staging lanes.

- I actually never thought about the topic you mentioned where "tires sticking to the glue downtrack" That is very interesting indeed and makes total sense. Like a bone-head I simply assumed it would make more sense to stay in the grove the whole way down the track; I will have to SAFELY try to nudge the car out of the groove a touch if the track is super sticky! For sure I am not spinning any tires in 2nd or 3rd gear so maybe as I get close to the 330 foot cone I can nudge the car over to the less sticky part of the grove.

- I have been doing a little bit of weight removal before the race events. Since I bring a ton of tools, gear, spare parts to the track with me it helps me to transport them in the car if I take out the passenger seat, rear seats, un-used nitrous bottle, trunk mounted stereo system. weight removal and storage space for tool transport. I also keep the front sway bar removed, but without cutting various parts of the car away, I can't think of much more to "easily" remove for weight. This winter I will do some serious digging into the weight removal topic, because since I still plan on installing a 6 point roll-bar, I would like to offset/negate that added weight by removing the equal amount of weight elsewhere on the car. I would like to keep the car at or under 3,500 pounds WITH me in it and with the upcoming roll bar installed. So I will have to shed about 150 lbs somehow. winter project. This Friday, I also plan on taking off the rear cat-back exhaust again since last time I did that (August 9th) I didn't really determine if it was helpful or not because at that time I was still making ignition timing changes and using different target AFR numbers. It will probably remove another 50 pounds, but then I will have to quickly put it back onto the car before the car show on Sunday in Linden that I plan on going to.

- I was using my street wheels for the first few track sessions this year, but back in August I got a heck of a deal on a barely used set of front-runners from my good buddy on this forum Joey D. They are Jegs SSR wheels 15x4.5" and they have a hardly-used set of MT sportsman SR tires on them. I run those at 37 psi hot, even though the warning label on the side of the tire says "35 psi max hot". They still seem to bulge out where the tire meets the pavement, and I would really like less of a tire bulge for less rolling resistance, but I am a little leery of dangerously over inflating them? Perhaps it is ok for the smooth drag strip passes, but I should air them down for the drive too/from the track? Photos of the wheels can be seen on page 7 at post #153 http://www.njfboa.org/forums/showthr...t=69033&page=7

- Running 93 octane fuel from either Shell or Sunoco gas stations only (unless low fuel emergency). The tune my tuner created is based around a 93 octane pump-gas VE table. I have not tried any octane boosters or enhancers, just stuck to straight up 93 octane. Part of me is curious if I could mix in some higher octane fuel next year, but I would need a new or modified VE table for that as all my CL comp and learn numbers would probably go wacky? The holley sniper EFI setup I have has no provision for knock sensors. I have heard that it is a monumental and often unsuccessful process to try to select a knock sensor (and its parameters) that might work for a shop built crate motor as opposed to a mass produced engine. Apparently there is a easy way of detecting knock that I have used.... looking for abrupt spikes or dips in the RPM line/trace on any of my datalogs. I have certainly seen some and that was when I had timing at 37 and 38 deg at certain RPMS. Now knowing that, I keep the max wot timing at 35 deg. if you look at the screenshot photo from my day racing August 9..on pass 3, 4, 5 on post #169 of the http://www.njfboa.org/forums/showthr...t=69033&page=7 and look at the red rpm line, you can see the spikes where the engine was knocking (jagged line) especially in 3rd gear. the rpm line should be as smooth and diagonal as reasonably possible.. any jaggedness is a sign of pre-detonation and abnormal rpm fluctuation... so I have been told.


The rear tires are the Mickey Thompson ET Street SS tires. I have 35 passes on them, plus about probably 400 miles of street driving too. They were brand new back in May of this year. They seem to do quite well with the launch, but I am unsure about how well they will do next year when I am launching with the nitrous shot. Despite being new, the tires seem to be a little bit scuffed up.... in that they are a little bit peele-y... probably from street driving to/from the track with them? At island dragway, I always go in the "race tire" staging lanes where they then line you up in the rubber groove of the starting line. For other cars with pure street treaded tires, they put a cone on the starting line, forcing the street tire cars to line up on the out-side of the groove, so that their tires don't peel up the good rubber in the starting line groove. This winter I hope to install an electric vacum pump to help give me more vacuum assist with my front brakes (for street, strip, and autocross purposes). I might even wire up the 2-step rev limiter to get a consistent launch, but I don't think I am ready to add a trans-brake anytime soon. The 2-step is super easy to wire up with the holley efi; just two wires and a switch and done... but if my brakes can't hold me from pushing through the beams, well...



- As for staging, I had a very enlightening conversation about this shallow/deep staging concept with Jerry (the Haz Guy on this board) just a few months ago. Prior to that, I had not focused on where I staged. Now, I do my best to shallow stage as often as I can. Like you said, it will result in a better E.T. because I get a rolling start before breaking the beam. I am not bracket racing, nor index racing so shallow staging seems to make the best sense for me.

- yup, that is where I am at currently, and sadly it is the end of the year. I'll say it hasn't been a bad year, but it took me a while and many days at the track to even get to this point. My first real deal street/strip car and build and doing my best to learn what really is important in a drag pass. MUCH MORE THAN I THOUGHT! We all agree that if the car was a true drag-strip dedicated car it should be way faster, like low 11's.. but It the car is a compromise between street-show-drag-autocross so I had to make sacrifices in areas of converter, transmission, rear, wheels, tires, and weight/creature comfort. I am not expecting massive gains from shifting and launching adjustments, but anything I can do to keep getting faster, well, I would like to learn and try it. Overall, the EFI tune is finally set and needs only the most minimal changes, but it is the end of the year now anyway.
---Much thanks for your input; feel free to keep it coming!
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Old 10-23-2020, 09:19 PM   #10
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BUMMER! I was totally packed up with tools, gear, and had everything ready to go around 2pm. Around 3 pm my buddy (3rd gen owner) sent me a text that Island was going to be closed tonight because of potential foggy weather conditions! Man, what a let down... I had planned on racing Friday night sot hat I could get the car ove to the big car show in Linden on Sunday. There is no Test and tune on Saturday at Island, so I am going to have to go to Island on Sunday and skip the car show. Probably wont get a chance to update this post until mid week though, but I do plan on running Sunday. I also wired up the 2-step rev limiter feature so i might try launching from that at a 1,800 rpm launch.

just testing it:
https://www.youtube.com/watch?v=B_vsvgeJJAw

and

https://www.youtube.com/watch?v=LsNEzd5cfiE

tried foot braking it while on the 2-step today on the street and had it set at 2,000 rpms and it was pushhing through the brakes. So I wil have to try lower rpm
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Old 11-01-2020, 06:38 PM   #11
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Here is some new data. I don't want to re-type all the technical info for each run, but if it helps at all, please visit my "build thread" where I have a in-car video, a datalog, and a timeslip for each run down the track.

I was happy to run my best 1/4 mile E.T. of ever, and it was 11.829. my best 1/4 mile mph was at Atco back on October 9th and that was 115.94. I came pretty close to that number on pass 3 this pat weekend, which to me, makes ZERO sense because I had a horrible launch since I am brand-new to the 2-step setup. However on that pass (run#3) I also had my fastest 8th mile mph at 96.36mph. Prior to this weekend I had only seen 94mph in the 8th mile and now I ran a 95.33 and then a 96.36 mph. My best 8th mile E.T. was on pass #1 of this weekend at 7.534 and this makes sense because it was also my quickest 1/4 mile E.T. My best 60-foot was my last pass of the weekend (and last pass of the whole year) and it came off of a foot brake launch at 1,188 rpms which gave me a 1.645 in the sixty-foot.




​​​​​​​





What's all this mean?!?! I don't know!
I guess, it means I am starting to understand what the car can do, but sometimes the numbers confuse me. I'll keep looking it over during the wintertime, but if anyone has any input, insight, advice, please let me know. Lets just keep it on topic as best as possible. Feel free to get real nitty-gritty math and science too, maybe just explain how you got there for some of us cave-man folks.
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Old 11-02-2020, 07:03 AM   #12
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how far apart timewise were your runs? that's something else to log. I know you have the timestamps on the slips, but as far as another line in the log or excel sheet may help as you get more and more runs under your belt.
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Old 11-02-2020, 08:27 PM   #13
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yea, true. I could add that. are you thinking along the lines of heat-soak issues or something else that I am not aware of? I don't mind doing the leg-work and everything, but not coming into this with years of drag racing experience, I am trying to learn as much as I can as fast as I can. Its a bummer that the car is done for the year and even though I made a ton of passes this year (45 I think?) it might not be enough data yet to start making sense. Much of the early runs were trying to figure out ignition timing, and different tires, etc. Only the last 2-3 months were when the car pretty much stayed the same configuration mechanically but I adjusted HOW I would drive it. So yea. This will be continued, would just like to run a little faster N/A before putting in the roll bad and the nitrous system. Gears would do it, and a change in converter, but that comes with compromises to the car at the street/autocross arena.
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Old 11-03-2020, 02:25 PM   #14
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yes, heat soak. You're already covering the change in temperature as far as the DA but heat soak is still a variable you want tracked which affects engine temps, etc.
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Old 11-03-2020, 02:58 PM   #15
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yea, very true. I agree.
I have the datalog capability to display CTS Coolant Temp Sensor info on the datalog. Usually I know while being there at the track and watching the CTS on the dashboard if I am getting hot or not. Usually not. I typically leave the CTS trace off the datalog display, but it is on some of the log screen-shots in my "build thread" Its the dark purple log that stays pretty smooth during the run. Temps while at the track are usually 185-191. Since I street drive the car to the track, I can't avoid generating heatsoak throughout the whole powertrain.
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Old 11-03-2020, 10:37 PM   #16
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What is the stall on the convertor? and heat soak might be giving you some slip.

Also, you made runs with and without the 2-step, and you moved the launch around allot. Make small changes, and when you get positive results make another run with no change and make sure it repeats. Remember what I said, the car could have just picked up but might not have repeated.

You said before the car pushes when you power-brake. Could the last run have pushed you in deep? would explain the quicker 60' but lower MPH.
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Old 11-04-2020, 06:10 PM   #17
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the stall on the converter is 3,400 It is an Edge Racing 9.5" STR (street) converter built knowing I would be spraying nitrous at the car in the future

Not sure I know what you mean by your paragraph #2. The ONLY thing I changed from run 1, to 2, to 3 was the launch rpm on the 2 step. Thats the only different change I made and to me, the change was indeed a small-change. I shifted at the same point as best as I could. I went from 2-step launch at 1,600 (1), 1,800 (2) and 2,000 (3) and then I footbraked at 1,200 knowing that the car would not creep (4). Smaller changes than that?

The car does push forward around 1,700 footbraking it. It did it on run #3 if you wanted to watch the very short video of it happening, check my youtube videos: https://www.youtube.com/user/IROCZma...=dd&shelf_id=4
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