tazman71

iTrader: (1)

Did an entire drivetrain swap into my car from a wrecked donor

Car had 52k on it when wrecked. Has stock bottom end, ported stock heads, LT4 hotcam, 1.6rr's, 52mm TB, LT's, a strange 12 bolt with 4.11's, and a twin intercooled P1SC getting 6psi of boost. Also a 6 speed car. Old dyno sheet shows close to 500 hp to the wheels.

Took down the track, and did not do as well as hoped. went 12.96 at 105.
I know I have to get my reaction time down and launch. Issue is that I hit the rev limiter at 6k well before the end of the track in 4th and had to shift to 5th. Would you recomend swapping the rear gears? Would this get better times, and MPH? Is it safe to up the rev limiter? If so, how much?

This is not really a track car, just take it down the track occasionally. Full street car with suspension bolt ons and AC.

Thanks for your opinions.

draggin97s10

iTrader: (2)

What size tire?

SS RRR

iTrader: (2)

Where is your power peak on the RPM band?

tazman71

iTrader: (1)

Tires are brand new nitto NT555r 275 40 17's.

Peak HP is at 5900. Hits rev limiter at 6000.

SS RRR

iTrader: (2)

Basically a stock height tire and you're running approximately a few hundred RPM shy of your power peak when crossing the traps. Regardless, even with that said you are a few hundred RWHP short of where you should be with that kind of MPH unless your clutch is gone and/or you were zinging the tires down the entire track. At that 500RWHP, taking everything into consideration you should be in the high 120's or low 130's depending on race weight, and you would have been way out of gear long before crossing the line.

tazman71

iTrader: (1)

Was out of gear long before the end of the track. Full weight car with a sub in the trunk and also had a passenger.60 ft was 1.86 and 1/8th mile was at 86mph at 8.56. Clutch is not holding up as well as hoped. It is a Centerforce. Looked like it had very little wear on it, so left it in. No real tire spin. Left just off of idle coming out of the traps.

This was my first time out in about 2 years, so not so good off the line yet. Also, was running rich then. Had to swap out the MAF. Pulling harder now, but not that much harder.

Also just installed the new wideband. A/F is dead on what the dyno sheets show.

SS RRR

iTrader: (2)

No you weren't. At 105mph in 4th gear you are at around 5600 and 5700rpm.

www.f-body.org/gears

Basically that dyno sheet of yours is either dated and there are major problems or is not telling the truth.

Edit.. nevermind. Read through your post again. You need a better tire before gears. If it were me I'd get some 27" QTP's on 15" wheels and see what happens. If you still run out of gear then consider changing out gears based on MPH from the tire swap.

HellTeeOne

Kick the passenger out. Up the rev limiter. Get some better tires. Put the car back on the dyno and find out what's going on.

93M6Formula

You left just off idle?? Get some Hoosier QTPs and dump that bitch at 4500 and see what happens. I'm actually surprised your 60' was that decent.
I launch mine at 4500-5000 usually.

pillarpod

did you have it tune after the swap?

pancho toco loco

iTrader: (8)

Forget what the factory tach says. Is your limiter tuned at 6k? I'd look at the tune before changing tires. Set the limiter to 6400rpms install a shift light set at 6200.. Take it back and go from there... That combo isn't making 500 to wheels btw. More like lower 400's possible mid................ Which pcm are you running? The from the donor or your factory? Where either tuned

bufmatmuslepants

iTrader: (3)

Your times show 350 at the wheels, spin the bitch to 6300, powershift, and give us more details and a dyno sheet. With 4.33s I was at 112 through the traps at 6200, something's wrong. My 300 hp car is faster and quicker than your 500 hp car...

NewOrleansLT1

What's you 60ft? And is your car even tuned? I ran a 12.93@106 UNTUNED with bolt ons...

tazman71

iTrader: (1)

Put in the tuned PCM from the donor car. Donor car was dyno tuned 10 years ago by FLP.
Don't know what dyno they used, but the car does pull very hard. Am sure I am part of the issue. Only had it together less than a week before I took it out to the track. Still working on a few bugs, but was hoping for low 12's considering I am hearing guys with similar setups doing 10.90's.

I know the MAF sensor was going out, because it was running rich. 60 ft was a 1.86. It has a shift light in it tuned to go off at 5800. Rev limiter hits at 6000. It did slow down quit a bit after hitting the rev limiter.

Is it safe to bump the rev limiter to 6400? Considering the stock bottom end.

SS RRR

iTrader: (2)

If your peak is at 5800 I wouldn't shift over 6100, but that's just me. You will have to play around with shift points to get your optimal time, but that's where I'd start out. Rule of thumb for a stock bottom end is to not take it over 6500, due to stock rod bolts having a tendency to stretch.

tazman71

iTrader: (1)

Per the dyno sheet, peek hp is at 5900. Losing over 100hp at 6000(assuming rev limiter) I wonder if it would peak a little higher with the increased rpm.

Thanks for all the advice. Did run the calculations, and should be at 110 before hitting the rev limiter. Wonder if it is off a little.

HarleyZ28

iTrader: (2)

Man my car is hotcammed with 410 gears ( m6 car ) I'm trapping 113 in a full weight car. I also weigh 230

pancho toco loco

iTrader: (8)

Most ppl with that cam shift at 6200-6400. I'd aim at shifting at 6300 w/ limiter at 6500... Anytime you race your risking something. If you touch the limiter and get out of it or complete the shift I don't see any harm