FANTAZ28

iTrader: (2)

zombie, what kind of rpm do you see at the end of a 1/4 mile pass? at 132mph right?

Zombie

iTrader: (2)

After launch the lowest RPM the car sees is 5400 and I shift at 6100. I'm not sure what RPM it's at when crossing the line though. It's got somewhere between 10-20% slip when I run 18psi.

FANTAZ28

iTrader: (2)

well if you are shifting at 5400 and the car let say goes through at 6100 that is 30 percent slip!

might want to look into that. anytime a car is undergeared it will cause more converter slippage. I think you are bandading your traction issues with the small gear.

even at 5400 the converter slip is already at 15% so im gonna say you are seeing close to 30 pecent slip.

Zombie

iTrader: (2)

I'm going to say that you have no way of knowing what amount of slip i'm seeing when I'm not even sure

Without me logging my 1/4 mile I can't tell you my exact slip. I can tell you that when I topped out the car on 15psi I didn't see my shiftlight (set at 5800 rpms at the time) come on until around 155 mph. That's about 5% slip.

I think my converter is on the edge of being too loose under boost at 15psi and i'm pushing through it some at 18psi, but changing my gearing would just be a bandaid work around for a converter (and make my car a way worse street car) i'm making too much power for. It's only a 9.5" and I feel a 10.5" would be better and am accepting donations (paypal to zombiestang@yahoo.com) for the upgrade.

FANTAZ28

iTrader: (2)

i just went off of , 26 inch tire, 2.75 rear gear 1 to 1 trans ratio and any where between 5400 (which is the lowest your car sees) and 6100 where you shift it, it comes out to 15% at 5400 and 30% at 6100. I used 132mph for the calculation. Unless your car does not go into 3rd in a 1/4 mile pass? but i assumed you do.

im sure 2.75 is great on the street , and im sure it's very easy to hook at the track but all in all it's not a efficent combo. But it is hard to have a very efficent combo and be able to highway cruise it.

MY99TAWS6

iTrader: (3)

I thinki for auto cars a bit lower gears is better but don't think its a huge issue on m6 cars. I see lots of freakin fast turbo cars on the boosted lists with 3.73 gears.
I am torn between 3.54 and 3.73 and going with dana 60 so lowest I can get is 3.54. The advantages of higher gear like these is much better off boost which lets face it is what most street cars will be seeing. Can't be hitting boost much in town for very long. And also easier on the clutch as well I think to get off the line.
Traction well not going to be much traction on big hp turbo cars without et street radial type of tires. Manual cars of course can build boost with a two step. Autos do it with stalls. Not sure why there are no antilag setups for our cars my dsm have antilag which can let my standard talon leave at like 20psi!

Zombie

iTrader: (2)

Maybe i'm wrong the RPMs now that i'm thinking about it. I did a log on the street of a 2-3 shift and I thinking the RPMs dropped from 6100 to 5300, i'll have to log it again. I'm running at the track again tonight so maybe i'll log a pass to get some more info. My tire height is 25.6". I do know that when the shift light was at 5800 rpms I'd see it come on at the top of 2nd around 97mph
so that works out to 12% slip. When I have the boost set to 18psi the shift light comes on around 92 MPH which is 18% slip.

When the shift light is set at 6100 rpms @ 15psi I don't see it until 107 which is 7% slip. On 18psi I see it at 105ish which is about 9-10% slip. Maybe that explains why it only picks up 26mph on the back half but does good in the 1/8 mile. The slippage kills my 1/4 MPH but works out good for my 1/8 mile. The converter seems to become really effecient right around 6000 rpms @ 18psi

Keep in mind these numbers are all aproximate so there is some fudge factor since they are from memory and not a log. I have noticed that since fixing some backpressure issues and shifting it at 6100 vs 5900 that it's picked up 1-2 mph in the 1/4 and 1/8th.

Kinda makes me wish I had another 400 rpms of power band.

P.S. I usually trap 133-134 on a good pass, the 10.38@132 was done into a 25mph headwind

code4

iTrader: (30)

My tranny has got hot a few times & here is what happen the first time we were tuning at ~15# of boost on the street. This is out of my t400.

nutz'00 Z28

iTrader: (16)

Our cars are very similar, 370", 88mm, th400, etc.. I have been running a 3.55 gear 325/50's, spinning to 6500rpm. Trapping 148mph in the 1/4 with a 1.39 60ft leaving on about 8lbs. I believe I am going to step up to a 3.73 car seems very sluggish for the first 150-200ft.

coop5885

iTrader: (2)

holy crap nice car...down to the downpipe. Thats crazy...you didnt see mine and then do that did you? p.s. put a stainless piece around it and it makes it look 100x better, you can see mine in the sig pic.

anyway th400 i assume, leaving on a t-brake or foot brake? What converter are you running?

FANTAZ28

iTrader: (2)

coop5885, here is a vid of my car with a 3.50 gear and 28 inch tire.
http://www.fquick.com/videos/viewvideo.php?id=3498

i wouldnt go any lower than 3.50, i would consider moving up to a 3.70 but the little change in gear is not worth the hassle to me right now

Zombie

iTrader: (2)

So much for the gears hurting 60's. Managed a 1.48 60' tonight 9 psi launch.. felt gooooood. Now I need susp work and skinnies, stock SS wheels are not the best front runners out there.

FANTAZ28

iTrader: (2)

did you log the car to check converter slippage?

nutz'00 Z28

iTrader: (16)

I actually got the idea from a buddy who has his downpipe on his civic running out the side. I planned on using a round 2-piece aluminum bolt together ring to put around it when I am done. That's leaving on the t-brake with a tight yank converter. Its suppose to be a py3400 but on the wood without any boost the converter will only come up to 2500rpm on the transbrake. Then it takes forever to build boost and start pushing through the converter enough to leave on 8llbs or more. I sent it back to have it loosened up some I hope it will help, the guys at Yank where really helpful. Calculated converter slippage is just under 4% which is very effecient I believe, and shift extension is 1600rpm. For some reason the boost bleeds off on the top end of each gear, 23.10psi peak and a average of 21.32psi per gear.

Here is a datalog from one of my runs.

Zombie

iTrader: (2)

unfortunately no, but it's slipping pretty good at 20psi. I could definately benefit from a tighter converter and/or a larger power band.

NA$TY-TA

iTrader: (21)

I would keep the gears you have in there now and leave with more boost. Your going to run out of gear with 3.73's and a 28" tall tire spinning to 7K at around 150-153. I know I did it and that's why I went to a 3.54 rear gear. I can. I can build 15 psi plus on the TB. Sounds like your converter might need to be loosened.

That's just my .02

Kyle

nutz'00 Z28

iTrader: (16)

I sent the converter back to Yank and the guys there took care of me. Hopefully it helps. I was having to set on the transbrake for 7+ seconds to build 8-10lbs. The motor just has no *****, its 8.2:1. Anyone know why it will make 23lbs at the beginning of each gear but then falls off to 20lbs once gear is redlined?

NA$TY-TA

iTrader: (21)

Back pressure will have some play in that for since it being a T4 flanged turbo. She might be getting close to being done. Ie out of its efficency and no more left

coop5885

iTrader: (2)

how much timing are you running in boost and on spool up? What kind of gas?

nutz'00 Z28

iTrader: (16)

Timing on the log above is around 28* at 0psi then total timing is suppose to be around 20*, but on the log above the intake temps where really high later on in the run and caused the timing to drop down to around 13.5*. Running VP113 fuel. I don't know a whole lot of details about the tune, I trust the guy that tunes my car "Bluecat" he is by far the best I know.