L98 Guru's Inside Please! Went Slower!?!?!?

[Mad-Mic]

Went to the track tonight to run the vette and she how she would do. Well she didn't do No where Near what I thought she would! I have some trouble shooting and alittle tuning to do.

Mods I have done since I ran the 13.18 at 105.84 with a 1.858 60' time:
New set of cut back AC Delco Rapid Fire plugs gapped .050
Air Elim Pulley
Crank Pulley
275/40/17's
KBD Mufflers

Here is Total Mods to date:
K&N open air box, MAF descreened, TB Bypassed, 160* T-Stat, Accel Super Coil, 12* degree advance timing, Cut Back AC Delco Rapid Fire plugs gapped at .050 Indexed, TPiS Long Tube Headers, !Air, Air Elim Pulley, !EGR, Crank Pulley, and KBD Targa 3" Mufflers. Hayden Tranny cooler. Stock 1600 rpm stall, 2.59 rear gear on 275/40/17" BF Goodrich Drag Radials

DA for the 13.18 pass was 600

DA tonight around 7pm was about 1500 and at 10pm about 900-1000. Here are my times. The car lost about 6 MPH and 4 tenths off of my previous best. I know the DA was alittle higher but 4 tenths and 6 MPH?

This was my first run. I just got there and the lane I picked was runnig so I was about 225 on water temp and 28 lbs in the DR's no cool down at all. I expected to run a few tenths off !?!?!

7:58 pm
RT .476
60' 1.990
330 3.3795
1/8 8.856
MPH 77.61
1000' N/A
1/4 13.892
MPH 99.33

My Best Run of the Night. This run I almost pulled through into Deep Stage as I tried to Max Cackle the stall at 1500 rpm. backed down and launched at 1300 but was already alittle Deep.

9:02 pm
RT .498
60' 1.934
330 5.616
1/8 8.657
MPH 81.23
1000' 11.284
1/4 13.522
MPH 99.70

This run I got Hot Lapped. :smash: Water Temp was 220.

9:08 pm
RT .589
60' 1.936
330 5.656
1/8 8.732
MPH 80.34
1000' 11.387
1/4 13.651
MPH 98.57

My last run I made sure I nailed the shifts at 4900 RPM in 2nd and 3rd. The run felt pretty strong.

10.22 pm
RT .570
60' 1.931
330 5.649
1/8 8.695
MPH 81.21
1000' 11.321
1/4 13.556
MPH 99.70

The water temp for the 13.5 runs was around 190. I try and stage at 130-140 at most but tonight was a Giant Mess. Stall RPM's were 1300 except the one time of 1400. (Not trying to flash the converter from 500 rpm with the DR's yet)

The timing lights kept going down and it makes me wonder if my Times were off a bit? I know a few other of my friends was saying the same thing. I seen 03/04 Cobra's running high 13's and low 14's.! There was no C5's up there tonight to judge some stock times off of too see if the timing was accurate or not.

The car pulls RPM's alot quicker now with the pulleys. It seems to pull real hard from 3000 rpm to 4900 rpm shift point. There is a more noticable dead spot with the Drag Radials on. From 1600 RPM to about 2600 RPM it's slow out of the hole then from my dyno sheet at 3000 RPM i'm Full Bore and once it hits 3000 RPM it feels like turbo's kicking in. I know the 2.59 Gears and stock 1600 stall is killing my 60' times but i have pulled a best of 1.815 on Good Year F1's at 18.5 psi dead launching.

Could the DR's possibly be bogging me so bad that the car is running that off?

I had to reset the computer putting the Air Elim Pulley on and haven't drove the car much to relearn the computer. Only about 50 miles by the time I got to the track. Could this be part of the problem?

The old regular 99 cent AC Delco cutbacks I had in the car were nice and brown so I know the AF is real close and by my old Dyno Sheet from Febuary the AF Ratio was 12.9:1 They were Gapped at .047
Could the New Gap of .050 cause a faulty burn?

Just shoot me some Idea's to check out while I sleep on this and try to get her back in shape before the Corvette Shoot Out Race this Sunday s: I thought the car would pull atleast a 13.0 if not a 12.9 tonight

 

[Tanreall]

Might be the DRs, I've seen other people lose a few mph and a tenth or 2 by putting them on when they don't really need them. Next time you go if you could have a set of DRs and a set of whatever street tire you like you can find out for sure. Other then that I'm not sure why your car ran slower. Hope you find the problem and fix it soon.


How do you like the sound of the KBDs?

 

[SG4206]

Mad-Mic
Normally, ET is how efficently you apply the power to the ground ,and MPH is how much power you are making. Keep this in mind , and work at each one indiviually.
My opinion is you lost 2 mph from Density Altitude difference and possibly another mph from oxygen content., so if everything stayed the same,you should have run 102 - 103mph. Seeing how you did not , and ran slower, it tells me your weather station is not giving you complete enough information; or you engine combination changed.
I feel the engine management system could be the culprit ; but I can't tell you what to fix. I haven't got into my '95 system in regards to tuning for track conditions. I personally am still a dyed hard Holley man.
Now , the 60 ' can be off from the BFGs ; just like you said. Too much bite, loading the engine too much. A little tire spin can keep the R's up into higher power range overcoming any loss in traction and actually running quicker ET's.
What you experienced , can be very frustating , and everyone fights these problems on race cares. It can take alot of hours and money. I do know, being around the NHRA stockclass fuel injected race cars at the track ; they can make computor adjustments and pick-up loss power ; more than I find with jet changes.

Doug

 

[redc4corvette]

Want a quick time and high mph stage shallow, want a win stage deep.

 

[SPANISHVETTS]

Mic,



I have the KBDs as well…They have Nooooo back pressure whatsoever. Running the KBDs without a Cat on Thunder cost me about 50# of torque below 2500RPM as compared to the old FlowMaster 40s with a hi-flow cat. I haven’t tried the KBDs with the Cat yet but since there is no drag strip within a few thousand miles of me I do not worry about the launch that much. Above 2500RPMs the KBDs feel and sound stronger.

I know that you already know this but… the 2.59 gears and the tall 2nd gear on the R700 will drag the L98 well below its torque curve on the 1 – 2 shift. I think that this is where the drag radials are hurting you. Maybe the street tires broke a lose enough on the shift to let the motor stay high in the torque curve while the DRs do not slip and drag the motor down. Just my $.02