4.30 or 4.56 Gearing With a Manual Transmission

[Matt D]

I would love a KB, but the ticket price to the show is more than I am willing to pay. NOS is not my bag and a centrifugal is nothing I want to own (I want all my boost all the time or nothing). Turbo would be sweet, but same issue as the KB. Too much money plus supporting upgrades.

Plus there is something special about a quick N/A car for me.

 

[BOSS302]

Thought I would come over and check out my S197 buddies tonight and glad I did... this thread is exactly what I was lookin for...

Procharger + 530hp + 4.10 gear + 28" Slick = Sucky 1/4 mile times...

I am currently running 4.10 gear, but with tire change last year to a 28.8 Drag Radial for street and 28" Slick for track this year, I can't get the car to bust into the 11's. Car launches great, cutting 1.65 60's but falls on its face by 1/8th mile...times like 8.1, 8.2 and 1/4 miles 12.1 and trap speed of 105 (shifting at 6500 into 4th at the line).

I have been considering 4.30 or 4.56 gear for the 28+ tires. Considering I hardly drive on the street, really considering the 4.56

I have just been disappointed that I havent had this car into the 11's yet... last year went thru stock clutch, upgraded, then blew out transmission 2nd gear, upgraded, early this year took out the spider gears and trac-loc clutches.. Damn... Now everything is up to snuff...and car don't have enough gear for the cams and blower setup... LOL..WTF..

 

[Mike K]

^ you sir are so close wish the best for ya

 

[1179]

A car with 530hp, weighing 3850lbs, should have the capabiliy of running 120mph in the 1/4. Falling down mid-track indicates that you probably have a ignition, fuel sys., tuning, blower or other problem (s). Get it to pull all the way, before deciding about a gear change.

Good Luck

 

[BOSS302]

Thats just it, it does pull all the way just not like it does in the first 300 feet. Its been back on the dyno to be checked and nothing is wrong with the tune or setup but tuner agrees, its doenst pick up hard until about 3800..

Car has made a 12.1 pass at 119mph before with the 28 tire. My slow trap speed of late is due to shifting right at the line

My cam powerband is 3600 - 7000 and with the stock 10# pulley on the Procharger they compliment each other. If I go back to 26" tire, the car pulls like a freight train throughout the run.

MT says the 28" slick grows to 30" down the track. If you do the math, my gearing is effective ratio of 3.93 (approx) at a standstill and drops to about 3.70(approx) during the run.

So, I need to either use a 26" slick or gear up. Gearing up is cheaper than new slicks.

 

[JeremyH]

how the hell are u trapping top of third bottom of fourth with a blower and 410s somethings not right...

 

[1179]

What was your et, mph, and finish line rpm when using a 26" tire ?

 

[BOSS302]

What was your et, mph, and finish line rpm when using a 26" tire ?

Don't know...it never had a 26" tire at the track.
I could tell the difference when I went from stock tire to 305/45/18 tires on the street which was 27" to 28.8" diameter change.

At the track its been pretty consistent with 12.2-5ish, around 110-113mph shifting at 6600-6700 out of third right at the strip. The only 114mph trap speed was due when the clutch was out and it ran a 12.2 shifted 3rd to 4th about 1000ft mark on that run.


I got an in-car video showing one of my recent runs at Route66, just got to figure how to upload (or where). I think track temp was like 110 at the time, so the heat was killing me. Car ran a 12.8 on this particular run.
Launched at 6400+ in 1st, 2nd gear shift 60-80 ft mark at 6500, then 3rd gear shift comes in around 330mark (based on 1st cone after 60ft marker in video) at around 6300 (200rpm short as I know the light came on right as I touched the clutch) and it runs 3rd gear right past the 1000 ft marker and ..shift at 6700 to 4th right couple hundred feet before strip.

I accounted the 12.8 to the heat and the early shift into 3rd gear.

 

[BOSS302]

how the hell are u trapping top of third bottom of fourth with a blower and 410s somethings not right...

Exactly why I am posting... LOL..

Keep in mind, running a centri blower...needs rpms to pull power..

 

[JeremyH]

Exactly why I am posting... LOL..

Keep in mind, running a centri blower...needs rpms to pull power..

I know that, but that doesnt matter, thats actually in your favor as you can build boost easier than i can at the line with a turbo. The fact is a n/a gt would trap the 1/4 at least in mid 4Th gear with 410s, a blower would put you at the top of 4th for sure. 410s keep you in the centri power band.

Unless you are short shifting and shifting very very slow or only have like 200hp or some other tune issue. Or you are boggin really really really bad. (Worse than me) IM boggin bad on dr's as i dont make boost till north of 5,000 rpms in first gear with the turbo. Still managed a 8.2 @ 98mph and a 8.1 @ 96mph in the 1/8. When I was na with 3.55s i trapped the 1/4 at the top of thrid at 6600 rpm with 315rwhp. And trapped 105-106mph. Btw my car is 4,000lbs with me in it.

Now with the turbo and 3.55s im just about done with 3rd gear in the 1/8 mile!
If i had 410s i would definetly be in 4th gear just at or after the 1/8 mile mark.


Your results just sound really odd to me!

 

[BOSS302]

I get what ur saying...but keep in mind a stock gt is running a 27 inch tire...all the way down the track so its a constant 355 and they run 13.5plus. I start off with a 28inch tire and at the end of the 1/4 mile I am running on 30+ inch tire... put a 30 inch tire on a stock gt and I bet they never hit 4th gear or redline in 3rd down the 1/4

The rule is 28inch should be running 430 gear for my setup..this keeps me at of slightly above 410 ratio all the way down track so it will get rpms quickier. My car only make 5 psi at 4000...the up to 13 by 6500.. for 530hp peak..

I am trying to get a 26 aslick to test with....if it works out then I will be swappin to a 456 gear.

Sent from my Ally using Tapatalk

 

[JeremyH]

I have heard of them swelling but 30" thats crazy is that a guess or did you measure?

 

[BOSS302]

Not a guess per say... First evidence was that the tire was rubbing the rocker panel, which we saw on burnout in video..at less than 100mph

So after checking their site for specifics, we found the FAQ on tire growth and had to call them. MT told us the particular tire with my bogart rim, would grow up to 1.5 to 2 inch during my run. Runout shows tire is actually larger than 28" at 18psi cold, so we use the baseline of 30" for the 1/4 mile run.

Here is the FAQ on tire growth
http://www.mickeythompsontires.com/faqpage.php?faq=15

 

[BOSS302]

Mickey Thompson states an average of 3% growth. However after talking to them, it could be 10% based on factors for tires of 28 or larger diameter. Stiff sidewall doesn't grow as much. I dont run stiff sidewall or tubes, and they bulge quite a bit on my rim as well.

 

[BOSS302]

Here are some times from Gateway last year with same tire setup. I know sometimes it helps to see actual numbers.

RUN 1 (18psi tire pressure, 5k launch)
RT ...... .119
60' ..... 1.707
330'..... 5.045
1/8 ..... 7.865
MPH.... 87.44
1000... 10.269
12.322 @ 109.92 (shifted into 4th right before the line)

RUN 2 (16psi tire pressure, 5k launch)
RT ...... .152
60' ..... 1.762
330'..... 5.159
1/8 ..... 7.975
MPH.... 88.92
1000... 10.306
12.270 @ 114.90 (shifted into 4th a little sooner than last run)

 

[JeremyH]

Gotcha! Weird though your 1/8 mph seems low to me, you cut a good 1/8 mile et but looks like its slowing down. I cut a 89mph 1/8 letting out of the gas and getting back into it. That mph looks more like a 400-425hp car. Gregs voretch with 410s was cutting 90-91 mph @ 7.6-7.7 on nitto drag radials hes making 430rwhp. My car at 540rwhp is trapping 96-98mph on nitto drs ( i think you should be closer to that with 530hp). Also your 1/4 mile mph should be closer to 118-122mph. Mph gives you a better feel for power. Def seems like you are down on power, not a tire height/gearing problem but on some more consitent tires or street radials and see if it is the tires but i think you are down on power, maybe the heats pulling alot of timing!

 

[BOSS302]

Yeah..I agree.. these times were the first runs with my 28" the slicks.. I never tried my Nitto Dr's at the 1/4 mile track, only at 1/8 mile. I will look up my log entry for those runs, but they are 29.9 diameter tires.

Here are the notes from my log for the 2 runs above...
Car weight: 3380 with driver
I was running a diablo tune, which dyno'ed at 505hp/413tq. (note this tune feel on its face at launch...until about 4500)
Date: 5/9/09. It was evening, around 6pm and 7pm respectively with temp about 73 and 68 respectively, not sure what humidity was.

Powershifted 1st run (2-3)...never let off the gas.
Powershiftied 2nd run (1-2, 2-3, 3-4).

Slicks spun .5 inch on rim at on 1st run
Slick spun 1 inch on rim on 2nd run.
(slicks are now screwed to rim)

Here was the dyno sheet from Anderson for this tune...

 

[BOSS302]

I know this has kinda got off subject at this point... sorry for hi-jacking thread.

 

[killr3v]

hey boss did you ever figure out what the problem was?

 

[05yellowgt]

Not sure but reading. Get through for the first time and this looks like a clear case of pulling timing at the track due to ait oil or coolant temp.

Sent from my ADR6400L using Tapatalk