bogor

I finally made it into the 12´s with my Carrol L98 SC system!! 1/4:12.34s/113.7mph, 1/8: 7.95s/90.4mph, 60ft:1.82s-really happy with the time/speed-a couple of weeks ago I would prob be satisfied running high 12´s but now....

There´s not many people around here running supercharged C4´s so my hope stands to you guys! What´s your opinion, can it be done (11´s) or have I reached the limit?? I don´t think the stock pistons will take higher boost-any suggestions how to pick up the remaining 0.35s?

Thanks
Göran

Specs: 1990 6-speed, 3.33, 8lbs max boost, S-trim, H2O inject., stock L98 short block, superram, headers and a blower cam (219/229, 0.490/0.500, CL114) & ET Streets, max SA at full boost 25´& AFR=12.2, airtemp 68´F and low altitude track.

lcvette

well.. swap that straight water injection to a 50/50 meth/water, and go for another 2-3 pounds of boost with a REALLY good tune and you will be there. the L98's had alot lower compression then the LT1 motors and are a good bit more boost tolerant. the other alternative is to go with a shorter length runner intake manifold and some better heads and let that combo rev a little.. being able to hold gears longer before shifts will net you better ET's by gaining you more power area under the curve, and this will also with the same pulley add some boost but not as much as a pulley change. likely it would read the same from flowing more air into the motor to be used in the form of volume rather then the showing a higher restriction in the form of PSI. just soem food for thought.. I am sure others will chime in as well.

Chris

REDC4CORVETTE

8 Pounds of boost with stock bottom end that is about it if you want to be safe,If not change the cogg and run 11 to 12 lbs of boost and you will hit 11's a few times ,then you know the rest.
I don't the clutch will hold up to long pumping it up though.
Making power will alway's cost you money.

bogor

I'm running approx. 20% ethanol now, I'll test with 50%. One idea I've got is to decrease the ignition advance and increase shiftpoint (right now about 5300rpm) slightly (thus increasing boost to, let's say 9 psi). Today I run the following SA at WOT: 27`@3000rpm, 26´@4000rpm and 25´@6000rpm. Maybe take out a couple of degrees to make it less knock prone when I increase the boost? Also considering leaning out slightly, target AFR is now set to 12.2@8psi/5500rpm. Will also check air temp at SC intake. It's really close to the header pipes so maybe a heat shield between the pipes and the airfilter will add some. Another idea is to try E85 fuel (85% ethanol, 15% gasoline). This should, at least make it less knock prone thus making it possible to increase SA.

/Göran

neat

I'd prolly leave the motor combo alone. 113 is enough MPH to get you there, but just barely I think.

I think you can get the last bit of ET you need out of the 60 foot time. If you're dead hooking the slicks, that 3.33 (I think that's what you are saying?) gear is really hurting you. With a set of 4.09 rear hears, I think you could cut well into the 1.6XX territory. If you pick up .2 in the first 60', I think your overall ET will drop enough to get you that high 11. Just drag 4th accross the line if you run out of gear on the big end.

lcvette

a 4.09 rear in his car would have him either in 5th gear crossing the traps or in OD.. both of which would be BAD, he does not have the power band to suit such tall gears and big MPH..im guessing his combo is out of breath around 4900 RPM, let me know if im right here Bogor, so do the math on that rpm and his final 1:1 tranny drive which is ideally what you want to be in crossing the traps near the top of your power band.

obviously with super high trap speeds it is required to use a longer gear at the big end of the track but those cars are pushing almost 2-3 times the power he is. for the 1/8th mile, 4.09's would be perfect but for the 1320.. i think he would be sitting and over revving in the end or in OD/5th without the power to continue a strong acceleration.

Chris

bogor

Yes, the gear ratio in the rear is 3.33. I checked some of my loggings and I cross the line at approximately 5000rpm in 4th gear. Maybe I can cut some on practicing my launches.

just came back from the garage. I installed a heat shield between the header pipes and the air filter. I´ve also manufactured a scoop that draws air from the wheelwell. I put a thermocouple inside the air filter and the result was a 10´F drop of air temp at idle. According to Greg (Blowerworks) the difference will be a lot less when the car is moving but I will keep it-it should at least do me some good when launching.

I think you are right Chris; According to a number of G-tech runs, the peak HP is around 4900-5000rpm. However, this might be caused by the way the G-tech samples the data. According to the Blowerwork catalogue, peak HP should be slightly above 5000 (G-tech measured HP approx 330hp).

Based upon Gregs recommendation I also lifted the oil fill cap and started the engine; unfortunatley it´s "puffing" smoke so I guess a ring is shot or piston cracked Increasing boost is out of the question now, guess "old faithful" is living on borrowed time.

Still, it´s worth it !! Anyway, I will continue to beat the L98 until my fully forged blower 381 is ready...

Thanks
Göran