Two C4 owners having some fun

[TedC]

Car 1: 1989 L98 auto w/3.07 (61K) air foil, open air cleaner, paper air filter
Car 2: 1992 LT1 auto w/2.59 (55K) air foil, open air cleaner, K&N

Stop watch times (dead stop, in drive, used one foot from brake to WOT):
MPH L98 LT1
50 4.9 4.3
60 6.3 6.4
70 8.1 8.1

Head to head:
Car 1: L98 pulled faster off the line to 500 feet (1/2 car length ahead)
10-15 feet of rubber, strong chirp 1st to 2nd
Car 2: LT1 pulled faster after first 500 feet (started to close the gap)
Chirp off the line, chirp 1st to 2nd.

Comments:
Traction in my 1989 is an issue even with a full tank of gasoline. That includes having an extra 200 pound passenger. You can feel the rear wanting to go sideways. LT1 needs a better axle ratio, but it sure could crank up the RPMs.

 

[vetteboy86]

Sounds like some good fun.

What exactly was your procedure for stop watch time?

 

[boomdriver]

interesting results on the 0-60 run.
I have often wondered at what point did added weight for traction then become dead weight as a liability that ruined the power/weight ratio..? Nice to see the L-98 get the jump even with wheel spin, LT's may spool up good further down the lane, but they cant spin up any faster than a good 'ol L98 stump puller.

I know my L98 tends to sit there when WOT is applied and waste rubber as it starts to advance...the only thing thats helped mine was lowering the rear with a 420lb rear spring so there is a mild weight transfer back on the rear with its current posture. That seemed to get a little more traction and allow the rears to hook up better. If I really want some wild ass end action, take the top off and its suddenly like driving on the ice rink.

either way, sounds like a fun day out there ! !

 

[TedC]

Sounds like some good fun.

What exactly was your procedure for stop watch time?

Super high tech!!! Used a track stop watch that could measure to .001 of a second. Minimum of six runs per car, minimum of two runs for each speed, always driving 1 mile at 60 MPH after each run to let the engine cool down, then averaged the results. Passenger managed the watch, and started as soon as the driver's right foot left the brake. We found this method produced consistent results. The 1989 digital dash was a little tricky to read at times when trying to display specific MPH readings during a fast rate of change. After a few runs you see a pattern where it jumps from say 58 to 61, never displaying 60. We did not attempt to optimize our launch in any way. No doubt, both cars could post better results using better launch methods. LT1 had 3/4 of a tank of gasoline, L98 had a full tank. Driver and passenger each weighing in at 200 pounds. At the end, he wanted a 3.07 axle, and I wanted 500 extra RPMs. However, we both felt lucky to be driving vettes with no loan payments!!!

 

[Black Bart]

The LT-1 makes torque at a higher RPM if you had used a LT-1 with a 3:73 gear in the diff it would have been quicker off the line and pulled the L98 all the way.
All that you proved was that a 2.59 coupled to a LT-1 is a terrible mismatch of gearing.

 

[TedC]

The LT-1 makes torque at a higher RPM if you had used a LT-1 with a 3:73 gear in the diff it would have been quicker off the line and pulled the L98 all the way.
All that you proved was that a 2.59 coupled to a LT-1 is a terrible mismatch of gearing.

Agree. But a 2.59 is a mismatch on a L98 as well. When looking for my second vette, almost every auto L98/LT1 I drove had the 2.59 gear. I ended up buying a 1989 with 3.07 and very happy I didn't settle for a 2.59 which my 1988 had. 3.73 would be a little to wild for a stock auto L98.

 

[TedC]

More performance results on my L98, this time using a G-Tech meter (set at zero rollout).
Same spot, similar test procedure. Brake to WOT using right foot.
No attempt to stop wheel spin which lasted for 12 feet (I measured it). Higher humidity.
0-50 4.89 (using stop watch it was 4.9 - pretty darn close)
0-60 6.23 (using stop watch it was 6.3 - off by .07 sec)
0-70 7.89 (using stop watch it was 8.1 - off by .21 sec)
0-80 9.87 (did not measure using stop watch)
1/8 mile 9.85 @ 79.9 MPH
Results are very similar to the Road and Track review for a 1989 L98 with 6 speed.
Looking at the Gs graph, appears to be around .2 sec lost due in the first .5 sec due to traction. I'm going play with the G-Tech to see if I can improve launch times.

 

[warren s]

How about some full quarter mile times run on heated tires??

 

[tmkassin]

Isn't the 89 250 hp and the LT1 300 hp? Gotta wonder if the LT1 is running right..

 

[TedC]

It is all in the gears and power range. L98 is a low to mid range torque monster and is hard to control off the line. LT1 is punch and go with a 2.59 gear auto. Once that LT1 got going, those extra ponies in the upper RPMs pay off. Two design points that I do not like about C4s are autos with 2.59s and L98 intakes designed for a 305.

 

[G Winter]

Get yourself one of these.


G-TECH/Pro Homepage

Glenn

 

[TedC]

I did just that. First round came from a stop watch, second set of numbers from a G-Tech. I'll now use the G-Tech to improve 0-60', 0-330' and 0-60 MPH times. After looking at the results using G-Tech's PASS (Performance Analysis System Software), the lack of tire traction is an issue for the first .5 seconds. Not possible to eliminate all of the .5 seconds, but 50% seems like a reasonable target. Would expect to see the 0 - 60 MPH times drop to 6.0 seconds flat which is inline for a stock L98 auto with 3.07. The problem with the current launch method is that I'm using one foot from brake to throttle. This method makes it harder to feather the throttle. My plan is to use the left foot to hold the car, keeping the right foot just touching the throttle, then using a less aggressive launch that produces tire chirp then full throttle.

 

[TedC]

More performance runs...
Same day, same starting spot, same driver.

Hard Launch: L98 with G-Tech - Brake to gas, full throttle, 14' patch
0-50 4.88
0-60 6.25
0-70 7.91
Comments: Nothing really new. Tire spin does not optimize times.

Soft Launch: L98 with G-Tech - Brake to gas, light then WOT, zero tire spin, no patch
0-50 4.98
0-60 6.37
0-70 8.06
Comment: Was surprised at the results. Car did not feel this quick.

Medium Launch: L98 with G-Tech - Brake to gas, half then full throttle, chirp, 6" patch
0-50 4.76
0-60 6.08
0-70 7.75
Comment: Takes time to master this launch, but provided the best times.

I also made a few second gear runs. L98 is gasping for air after 5000 RPM.

Automatic WOT Shift Points
1st to 2nd @ 4950 RPM +/- 50
2nd to 3rd @ 4850 RPM +/- 50