IROCZman15

iTrader: (25)

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 117mph 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.

IROCZman15

iTrader: (25)

yikes! nobody? I know its a wall of text and math, and I didn't expect an outpouring of people jumping in to crunch the numbers, but kinda hoping someone might be able to glance at this stuff and give their opinion.

A fellow TGO member and I have been chatting via text messages and he sent me this website (calculator) so I am going to try to play around with it and see what the results are...

https://glennmessersmith.com/shiftpt.html


I plan on hitting the dragstrip this Friday night for test and tune, and there is a good chance this might be my final drag-strip day of the year, so I am hoping to best prepare myself by then





I put in the numbers I have from my engine dyno printout 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).

89formula350b2l

iTrader: (11)

Wish i could help. My 406 has not been started yet. Next season i will be playing this game.

IROCZman15

iTrader: (25)

Just sat down to start typing up my long update on my "build thread" and also an update from here. That will be posted in about an hour.

But, I am looking at your car setup in your signature and I like it! Would love to see how you worked your exhausts underneath. If you have a build thread on this site, let me know, or if you want to post info/pics on it on my "build thread" please feel free... however maybe don't post them on this particular thread, as I would like to keep this thread on topic with strictly tech stuff about launch and shifting.

IROCZman15

iTrader: (25)

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?!?! 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.

skinny z

Subscribed.
I may even have something useful to offer once I can sit down and have a good read over your posts.

skinny z

I posted this link for hemi so as to give an insight into who's done what and what it takes to get there.

https://www.thirdgen.org/forums/orga...uspension.html

The info is a little thin (I would have liked to have seen greater transmission detail and in particular who uses a transbrake) but I think you can see a trend emerging and that's what the really fast cars have to get a short 60' time (and a wheelie). Seems the faster cars, especially those NA, have short gears, big tires (as in diameter) and adjustable suspensions. Plenty in the 1.60's. 1.50's even with modest parts, gearing and tires. But you saw Matt's white Coupe and that thing leaves at 6000+ and has the bits to plant the tires. 1.40 60'.
It goes on from there. Like 1.1x with the rear tires!
But that's what it takes.

Tootie Pang

iTrader: (2)

With my almost stock 5.7L TPI I shift at 3,900 RPM. LOL

skinny z

C'mon Tootie. You gots more RPM than that!

IROCZman15

iTrader: (25)

thats an awesome link skinnyZ, I am going to have to give that thread an in-depth read.

I also agree with what you said in My hemi's thrread that there is very minimal (if any) change in 60foot from launching at a 900 rpm idle vs a 1600 footbrake. My results show it is negligible. In order to cut a better 60foot, I will certainly have to launch at a higher rpm, and without installing a trans brake, I think my only/best option is to install an electric vacuum pump for the brake booster. since my engine only makes 7.5"vac, the booster can't hold the car back past 1,700 rpm. An electric vac pump connected to the booster would provide 25"vac and hopefully I could footbrake up higher, perhaps into the 3,000 rpm range? think this is possible? or is a transbrake my only real option?

skinny z

That's a really good question.
More vacuum to the brakes for more holding power.
As Orr suggested, and is my practice, I give the engine a neutral free rev after the burnout so as to build some vacuum for a better brake application (it also clears the pipes, so to speak). Thing is, even with that, I'm still pushing through the beams. IIRC, the front tires are locked and skidding along the track. Hard to say really as I've never had video. Just feedback from my spotter. I have seen that from others though.

My opinion is that one of two things are needed. A converter with a different specification. One that'll allow more foot braking RPM. Or a transbrake. Although the later seems a little excessive to me. Still, leaving against the brake with the limiter pinned is definitely going to give you the best launch possible. Kind of exciting just thinking about it really.

If the objective is to go fast, that's one thing. If the objective is pull a wheel, that's another. The two aren't necessarily interdependent , if you know what I mean.

Of course there's another way.
My racing friend, chassis shop owner and NHRA license holder always suggested more gear. More gear and a bigger tire. But that changes the entire dynamic of the car and, like you I think, it's not something I'm willing to sacrifice. I'll suffer with something less at the dragstrip so as to keep more of the overall package I wish to have.

Decisions. Decisions.

IROCZman15

iTrader: (25)

Ordered my 3.91 gearset and the install kit today.
Probably will install it a few weeks from now,
hoping it can really bring down my 60foots to a low 1.5x



this article was just in my Hot-Rod magazine email, might be helpful to some. I learned one or two things, so i will just post it here:
https://www.hotrod.com/articles/how-...41C2CFDB8C8477

skinny z

I doubt you'll be disappointed with the new gears. Judging from the data you've posted, it would seem to me that there's some RPM to be had at the top end. That will (should) transcend into an overall improvement along the entire 1/4 mile.
Now here's the thing. Traction. Which interestingly leads to wheelies. It's been discussed that front end extension is paramount. You have to get the nose up for weight transfer. With enough extension the momentum keeps the front end rising. BUT, that's providing the rear tires are able keep traction. I'm not so sure about adding weight to the trunk but I'm all for relocating weight back there.
It should be an interesting time for you this season.

Orr89RocZ

iTrader: (20)

Wow i did not see this thread til now. What size tire?

are you locking the converter during the run?

i’ll run the shift point math

IROCZman15

iTrader: (25)

cool, thanks guys. yea I am pretty sure the 60 foot will improve and I will come through the finish line right at peak hp (6,000-6100). I posted the wheelie article because even though I am not on a mission to pull a wheelie, I know that with a better 60 foot (hopefully coming form the gear swap) I will be entering wheelie territory.

I spoke to Moser Engineering, Dana at ProBuilt Automatics, Andre at Edge Racing, and a few others .. everyone says that the 3.91 will suit my setup great. We went through everything from camshaft specs, tire height, converter, car weight, car use, future plans, future nitrous use, etc. Andre mentioned that with a 3.55-to-3.91 gear swap my flash stall would drop down a few hundred rpm but this would help me foot-brake launch better from a moderately low rpm. Dana told me that launching at a 1,500-1800 rpm foot brake will be my best for torque multiplication , unless I find that my throttle response is so crisp that I could leave lower like at 900 idle or 1200rpm. Thats what I had been experimenting with most of the summer and that's why I started making the hand-written sheets posted above.


skinny: yup. I did play around with adding weight into the trunk last year, up to 250 pounds at one point, I think we chatted about it in my build thread. This was just an experiment at the time. You are right about traction starting to come into play more. The tires should be good, but the style suspension I have (not drag oriented) is going to be the interesting factor that I will have to wait to test out; but not until the track opens in April.


Orr: the tire is a 255/50/16 the Mickey Thompson 3460. It is the treaded DOT Tire MT offers, not the bias ply ET Street. here is the actual link to the actual tire. https://www.summitracing.com/parts/M...RoCnfIQAvD_BwE
I will be using this tire for the 2021. Maybe once these tires are used up will I budget for another set of taller 28" tires, but for this year, it will be these. On the front I just have some MT Sportsman skinnies on a Jegs SSR wheel.

I now am not locking the converter during the run at all; however I played around with locking it during a few passes last year. When I did lock it, I locked it at the top of 1st gear and left it locked-up the rest of the pass. it caused the shift from 1st-to-2nd (and also the shift from 2nd-to-3rd) to drop much lower in the rpm band and it was a "dog" down the track. Andre at Edge Racing converters had earlier told me that the converter locked would not help me in the quarter mile, and the technical stuff he mentioned was a bit over my head at the time.. I should have wrote it down because I would love to re-visit that topic! My current thought on locking the converter would be that if I am coming up past peak hp and still have a hundred feet of so to go to get the the finish line, I could then lock the converter (via my manually activated toggle switch) and pull the rpms down a few hundred rpm to cross the stripe at peak hp range. Or, am I mistaken, and at that rpm the converter is not slipping anymore and is close enough to being "locked" but not actually locked? It's a 9.5" Edge Racing STR converter re-set to be at 3,400 rpm


Feel free to chime in or ask any questions. I am an open book and advice from experienced racers is much appreciated.

I have plenty of datalogs, videos, and info available if you want anything specific. Here are a few launch photos.

Orr89RocZ

iTrader: (20)

This is tough to fully analyze since 1 converter slip and fall back rpm is hard to predict with changing shifts. 2: no engine power data much higher above 6400.

you say it typically falls to 4700 rpm on shift? With your normal 6000-6500 rpm shifts? Trying to figure out where to start on the power curve for average hp.

right now you have9.5% slip up top end. Not bad but not great. More gear would help that potentially. With the low stall, first gear is much more likely to benefit from much higher rpm. But if the first gear shift is 6000-6400 rpm and falling back to 4700 thats a ton of slip, or maybe thats what some call shift extension. This greatly changes the 2-3 shift rpm.

basically with 3400 stall and acceleration assuming the 9.5% slip up top, and extrapolation of your power curve beyond 6400, it wants to be shifted well above 6400. The curve used to predict power above 6400 is likely wrong and too generous but given that assumption, the values show 6900 as optimal first gear shift.

now its hard to say where the converter rpm goes to on 2nd gear shift, the slip or extension is hard to know. If i use 4700 engine speed, then you shift to 3rd at 6650. If it fell to 5000 in second then shift at 6525. If it fell much below 4700 like 4000 then you go to 6900 again lol

thats what the highest average power across the rpm range is showing me

IROCZman15

iTrader: (25)

very interesting actually. thanks! I am going to re-study what you wrote and analyze it. Revving the engine that high makes me a tad bit uneasy. When the engine builder built the motor I asked him what I can spin it to and he said right around 6,500. He advised to shift between 6,200-6,300 and set my rev limiter about 6,500. So that's been the ballpark I have been comfortable with. If it made great power closer to 7,000 I would be happy, but I don't want to find out by blowing it up. I do see your math and with the converter slip, that all makes sense to me. cool.
-for what its worth, just as you were writing your above reply, i was editing my post above yours and adding a few sentences with tech info as well as a few photos too

One reason I created this whole post and my lists is because previously I was just going off of my timeslips and seat-of-the-pants feel. To me it felt like in 1st gear above 6,000 I was not pulling that hard at all, so I was tossing around the idea of short-shifting 1st gear and then reving out 2nd and 3rd gear higher into the rpms. My math/science/data proved I should NOT short shift ANY gear

I have a bunch of datalogs and videos (with audio) if any of that helps. Below, I'll post one of the datalogs to show where I shift (red line is rpm) and where the shift lands. In my build thread I discuss all of these launch, shifts, car setup in a small paragraph designated for each dragstrip pass. the best and most recent info is on page #4 of the build thread. Don't feel obligated to look or read it all, but in case you needed clarification or more info.. its there! post # 187 is a good example of a day at the track :


https://www.thirdgen.org/forums/tech...install-4.html


here is the datalog of my best pass to date. 11.82 at 115mph
Launched at 1,676 and Shifted 1->2 at 6,573 and 2->3 at 6,632 while tagging the rev limiter a bit, and crossed the stripe around 5,842 (actually less rpms... I ran it out past the stripe, so probably more like 5,700 rpm at the stripe)

Orr89RocZ

iTrader: (20)

Yeah, obviously if you wanna make this more ET friendly it needs more converter and gear and optimal would be a trans brake for a 3000-4000 rpm launch....but that takes away some street functionality and I doubt a 700r4 would like that

am surprised it isnt in the 1.5 60’s tho. I had a 383 with 3.42 and 3600 stall and 1.55-1.58 was fairly easy to do. And i doubt it was much over 500 hp. It peaked at 6250 rpm but held flat to 6500-ish and I found it liked 6800-6900 rpm as shift

if the valvetrain is stable it will take it but to know that you need to dyno to 7000 lol and see if power remains stable. It will drop off obviously but should not fall like a rock either or become wavey

if you dont wanna go that high, i’d try switching those shifts on your best pass. 1-2 at 6650 ish and 2-3 at 6525-ish

skinny z

There's no accounting for what the converter is doing as mentioned.
The hard math, without slip, says 6500-3400 on the 1-2 and 6500-4000 for the 2-3. I'm in agreement on the higher revs for the first shift and somewhat less for the 2nd.
But including the converter is allowing for that reduced gap between shifts and apparently is an independent function from the actual stall although the two are obviously related to some degree.
I know there's no change coming to the converter spec so it is what it is. It's worth mentioning though that "our" Yank 3800 keeps the shift points above 5000 for all gears. And that's probably a 425-450 HP 355. Made for a significant improvement in ET.
Back to the gearing, this to me is where you'll see your gains. The converter isn't going anywhere but there'll be some impact with the change in gear. I believe the Edge guy had something to say in that regard (although more about the stall than the shift extension IIRC).

QwkTrip

iTrader: (22)

Regarding shift points, I think general answer is you rev it to the sky until the engine can't handle any more or torque output is making a beeline for the floor.

The only thing that accelerates the car is torque at tire. Horsepower literally does not matter. Only torque matters. If the torque at tire before the shift is more than the torque at tire after shift.... then it ain't time to shift yet. Maximize area under the torque curve at the tire, not the engine. You must take into account trans gear ratios and torque converter behavior.

ShiftyCapone

iTrader: (7)

Back in my undergrad days I took an advanced automotive dynamics course as an elective and we created a drag car calculator that would basically calculate the optimal conditions for the lowest ET. It even included partial spin of the tires, tractive force vs traction force, roll center, coef of friction/drag, etc. It was pretty nerdy. I will try and dig it up. The prof was one of the top GM diesel scientists that lead the engineering collaboration between Isuzu and GM. If I remember correctly the biggest factors for an optimized ET were getting the little bit of tire slip calculated combined with the CG shift during launch. A dead "hook" without any spin was actually slower, physics wise. Hence why drag tires, "square up", and paddle down the track surface. Bias Ply vs radial also changed the variables. If I find a copy of this it is likely in MatLab of which I don't have a seat.

IROCZman15

iTrader: (25)

this is all awesome advice guys. much thanks. I can't wait to get back out to the track, but my home-track is not opening until April this year sadly. My 3.91 gearset arrives next week and I will probably put it in a week after that.

Orr: i remember reading your info in the early posts on that "post your best 60 foot time and suspension thread" and I kept saying, wow hes killing it with a setup similar to mine, whats wrong with my slow numbers" sometimes i feel like something is ******* the power/torque on this car. I've gone over everything I can think of. Your previous setup and numbers make me have a similar goal to get to. One day this year I would like to get this thing to a dyno and get powertrain numbers instead of crankshaft power numbers.
-also, you asked earlier if I was locking the converter during the run at all? what are your ideas/opinions on locking or not-locking the converter in a setup like mine? any explanation is appreciated

skinny: I get jealous when you discuss the yank converter! A few times you mentioned it in my build thread and ti sounds like a real game-changer. I am going to keep this Edge converter at least for this year and also to see how the nitrous works with it. If it turns out I find a bunch of $ and have a budget to swap a converter, the Yank SS3600 or 4,000 might be the way to go

Qwk: makes total sense to me. thats what I am looking to maximize, is the torque and acceleration through the powertrain..to the tire. engine is one thing, but to the tire is what matters. Chassis dyno time would help!

Shifty": thats awesome. That sounds more advanced than some of the other online calculators i have used. most were for shift points and gearing. I am not smart enough to run the numbers on the fly so I either have to use calculators, or advice from knowledgeable people.

Hopefully the whole world doesn't explode/implode and we can still drag race cars this year. Would love to physically test everything you guys are suggesting and report back with datalogs, video, and tech info !

Orr89RocZ

iTrader: (20)

I was never able to go any quicker et wise with locking the converter. I was suggesting leave it unlocked if you were locking. I have seen more mph and it always dyno’s more rwhp locked up. Some guys have claimed to go quicker. But to me, the gear spread rpm drop does not favor locking, it pulls the engine down and uses too much rpm range. On tighter ratio trans it may be better

converter specs and how it reacts can make or break a combo. Perhaps there are some design tweaks that can be made to let it hit harder. Or simply more stall is needed. My best times were always with footbraking as high as i could get it to hold.

skinny z

Isn't there a concern with putting full torque output through the dinky little clutch of the lockup?
It's obviously designed well enough to handle cruise RPM output but max output? I'd like to try that for the next dyno session but it makes me a little uneasy.
The last converter we spec'd got a triple disc clutch. It was for another Yank (10.5") but for a multipurpose '69 C10. Towing the travel trailer to the track then racing is the plan. (Hoping the cammed LS3 goes low 12's).
I'd have no hesitation locking that one up on the rollers

Orr89RocZ

iTrader: (20)

I have heard that. Not totally sure, i would ask the torque converter manufacturer. I tested my Edge racing one on my bolt on L98 and on my 383, but mainly only locked it on the dyno to see true power