as it says above, i am having to shift into 5th gear approx 100 ft before the end of the 1/4 mile. GSR tranny with 8600 rpm limiter. M/T 24.5 x 8.0 x 13". Question is, do i need to go with bigger slicks or switch to a B16 tranny? not an option to rev any higher.
btw, what mph would a car be in 4th gear. with a quick glance, i saw a little over 130.

 

man.. all i can say is.. that's fast... once i reach 120 mph in the 1/4, i'll call it a day...

 

Can se see a timeslip? How much power are you making/what's your trap speed?

 

B16 tranny will only make your problem worse.. Why can't you rev higher? 8600 limit seems kinda low for a car doing around 130 trap speed. a 25" tall slick and a couple hundred more rev's and you would be set.

 

i don't have any timeslips as yet. these runs were made without timing lights. last dyno was 515 whp @25-26 psi with an inline pro manifold. since then, it has been replaced with a full-race and tuned @ 29 psi. i am guessing maybe 550 whp. could be more. going to dyno it in a couple of weekes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">Why can't you rev higher? 8600 limit seems kinda low</TD></TR></TABLE>

like he said what with the rev limit

 

Thats kinda High PSI for the horsepower last i recall duc groundzero was boosting at 29 PSI he was runnin 712 HP.

 

That's really strange... Brian is running a straight GSR tranny with MT 24.5x9x13 slicks trapping at 136mph (trap speed, actual is higher) and he's still in 4th... Revs are pretty close to your too... If you're trying to eliminate that 5th gear shift (which I would) a B16 tranny is just going to make it worse just as DIRep said as its' a little tighter... You don't have a 4.785 FD or anything do you? Let me get back to you tho, gotta think about this...

EDIT: I also just calculated this out and you should still have room so something is up... Your actual ground speed attainable at 8600rpm in 4th gear with 24.5" tall slicks on is ~137mph... If you're trapping in the 120's your actual shouldn't be 20mph faster... Also you're sure you have a GSR tranny right... An S4C, etc. (B16) at 8600rpm on the same slicks has an actual ground speed of 128mph... With your trap speeds and the fact that most tachs are normally a bit off (typically we see about a 300rpm difference on the dyno, *tach being higher) the numbers that add up more come from a B16 or a 4.785 FD GSR tranny... You know more than I do about your car, I'm just trying to help you figure this out...


Modified by Kataku2K3 at 10:10 PM 2/4/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Option &raquo;</TD></TR><TR><TD CLASS="quote">Thats kinda High PSI for the horsepower last i recall duc groundzero was boosting at 29 PSI he was runnin 712 HP.</TD></TR></TABLE>

duc's turbo is prolly bigger

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Option &raquo;</TD></TR><TR><TD CLASS="quote">Thats kinda High PSI for the horsepower last i recall duc groundzero was boosting at 29 PSI he was runnin 712 HP.</TD></TR></TABLE>. well, i am doing the tuning myself and trying to learn more, so i try not to tune too aggressive. btw the compression is 8.0:1, so i guess if i had a 9.0:1 or higher, whp could be ~600whp.

 

[QUOTE=Kataku2K3]That's really strange... Brian is running a straight GSR tranny with MT 24.5x9x13 slicks trapping at 136mph (trap speed, actual is higher) and he's still in 4th... Revs are pretty close to your too... If you're trying to eliminate that 5th gear shift (which I would) a B16 tranny is just going to make it worse just as DIRep said as its' a little tighter... You don't have a 4.785 FD or anything do you?

yes, it is a GSR tranny. my first thought when this happened was that the slicks was spinning causing it to bounce off the rev limter or maybe the clutch was slipping. don't know.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">B16 tranny will only make your problem worse.. Why can't you rev higher? 8600 limit seems kinda low for a car doing around 130 trap speed. a 25" tall slick and a couple hundred more rev's and you would be set. </TD></TR></TABLE>

yeah, i can rev higher. have 25" m&H slicks now.

 

I dont know what your problem is because I have a SOHC turbo that can hit 130 in 4th so you definately got somekind of issues. And dont give the man **** about low HP at high PSI, some people cant do everything all at once, I might be building a engine and just crankin up the boost on the little TDO5H before upgrading to a T3

 

Just curious by you say you can rev higher now, are you saying this because you have 25" tall slicks? If so, you know tire size isn't going to have any affect on your revs, it simply affects you ground speed at the same rpm... taller slick = lower rpm at the same ACTUAL ground mph... Good Luck, I really don't know...

 

Ok, a b16 tranny is tighter gearing that a gsr so that is out of the question. You could either find a lower final drive, or put an ls tranny in the car. Alot of people say that an ls tranny will help, but only if your trapping well into the 120's If your trapping at 130mph i would do an ls tranny.

 

I don't think so... That's the worst thing you could do... Again we run a straight GSR tranny on Brian's car and it works great... He's also trapping at 136mph at ~8500rpm in 4th on 24.5x9x13's.... We've run an LS tranny many times before and if you take into consideration what your overall wheel rollout is with 24.5" tall slicks you'll see that's just plain stupid... Try finishing at the beginning of 4th gear... If you wanna see how Brian and Duc's car reacted to an LS tranny compared to a GSR check out the vids in my profile... In "GroundZero.mpg" Brian is running a GSR and Duc is running an LS... I made "PIR.mpg" a couple months before GZ.mpg and as you'll see Brian's car bogs like crazy running the LS tranny...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BoostedbyFastrax &raquo;</TD></TR><TR><TD CLASS="quote">. well, i am doing the tuning myself and trying to learn more, so i try not to tune too aggressive. btw the compression is 8.0:1, so i guess if i had a 9.0:1 or higher, whp could be ~600whp.</TD></TR></TABLE>

Ahh ok that makes more sense now, sorry for bashin yeah just didnt make much sense 2 me.

 

you should be able to make more power with 8:1.. we made 475ho on 20psi and a crappy tune with pump gas on 7.8:1

adding a few more revs shouldnt be a problem with a built motor. we were turning ours to 9500 rpms. that was a 2liter b16 (84.5mm boreX89mm stroke)

 

8600???????????

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kataku2K3 &raquo;</TD></TR><TR><TD CLASS="quote">Just curious by you say you can rev higher now, are you saying this because you have 25" tall slicks? If so, you know tire size isn't going to have any affect on your revs, it simply affects you ground speed at the same rpm... taller slick = lower rpm at the same ACTUAL ground mph... Good Luck, I really don't know... </TD></TR></TABLE>

i can rev higher if i choose to, but set 8600 as the max. just got in 25" M&H slicks.
The MT 24.5 blew out on me on my last run.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">that was a 2liter b16 (84.5mm boreX89mm stroke)</TD></TR></TABLE>
Deckplated motor? If not do you know what your R/S was... Just curious

 

I just did the calculations for a gsr tranny(1.03 4th gear, 4.40 final drive), and 24.5" slick and at 8600rpm's your ground speed should be 138mph. Kataku is absolutely right. I woulda done the calculations earlier but my comp wouldn't let me.(another story) Your not telling us something because unless you are showing around 135mph on your time slip then you shouldn't be topping out your 4th gear.. Just want to clarify that this is a hydro gsr tranny and not a cable right?

 

Isn't there a 4th gear from another B tranny that will allow you to stay in 4th to the end? My B16 LSD cable tranny has a 4.2 FD and I can get the car to 130 in 4th. Can you snag a FD out of one of these trannies and reach the traps in 4th?

Here is a cool gear calculator link that may help.

http://www.housemanautosport.c....html

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">I just did the calculations for a gsr tranny(1.03 4th gear, 4.40 final drive), and 24.5" slick and at 8600rpm's your ground speed should be 138mph. Kataku is absolutely right. I woulda done the calculations earlier but my comp wouldn't let me.(another story) Your not telling us something because unless you are showing around 135mph on your time slip then you shouldn't be topping out your 4th gear.. Just want to clarify that this is a hydro gsr tranny and not a cable right?</TD></TR></TABLE>

it is a hydro tranny. well the runs were not clean runs. spun on 1st & 2nd and hooked afterwards. but shouldn't the car still be able to finish in 4th? never had this problem before, even when spun on 1st & 2nd.

 

only thing i can think of is if you were spinning the slicks in 4th @ the 1000 ft.