[sunrise]

Hi there,

My '04 Z06 just has headers/cats/tune and dynoed 385RW. It was my first time in a Z06 at the track so I was not hoping for too much so most of my runs were low 13s and high 12s but on one run I got an unbelievable 12.1, 1.806 60' (thanks so much to Ranger and Dr. Ron for give me launching tips!!!) BUT my trap was only 110MPH.

In looking back all my runs were around the 110MPH ranging from 107MPH to 111MPH. Should I not be trapping around 115+ MPH considering I am dynoing 385RW and had that 1.806 60', 12.1 second run?

I fear I may have some valve or rocker issue that is making my Z06 trap low. I felt that once I shifted to 4th that the speed claimed very gradually. Any suggestions anyone?
I am getting the slight Engine Tick noise during cold startups.

Any help would be much appreciated.

Regards,
Sunrise

 

[Greg Irvine]

Well, assuming that the clocks were OK, I can only guess that you are short shifting, meaning shifting at 6000 instead of 6500-6600 rpm range...Do you have it in competition mode? and NEVER watch the tach in you head-up display but rather your actual tach instead..But that would not explain your one run at 12.10...It might have been a terrible DA day for you...Do you know what the DA was?...We have the same HP basically and mine always runs 116.5 to 118.5...With a higher DA your mph will drop and with a lower DA it will raise...Your 1.8 was a great 60 ft time though...But I doubt you have valve train issues with 385 hp and your mods...Your mods seem to be in line with them...

Greg

 

[sunrise]

Hi Greg,

Thanks for your response. I tried to shift as close to the max as possible probably around 6300-6400 and yes I do have it in competition mode and I did not look at the heads-up tach since I know it is delayed.

What is the DA? The track is at 1000' elevation and I was also hoping to get around the 115 - 117 mph. The time ticket does not mention any DA value.

Except for the great launch I did not do anything different on that run in terms of shifting thus I got only a 110mph on that 12.1 run. The other runs I all trapped around 109-111.

What are you usually getting for your 60' time? I read on this forum of a bent lifter or something that happened to another member that also got around 110mph then when he got that fixed he ran consistent 115mph traps and thought I might have that issue but as you mentioned I dynoed 385RWHP.

Is there anything else I can check out or could it just be my driving...? but that does not explain the 12.1 run.

Thanks in advance for your response.
Regards,
Sunrise

 

[robz]

90% of the time its the driver/weather/altitude. 10% of the time there truly is something wrong with the car. What tires were u running? The trap speed seems low and low 13's with that trap speed would point to driver error. A 12.1x with a 109 trap speed doesn't make sense as mentioned above. When you dead hook or close too it your trap speed will often be lower than if you spin alot. A high trap speed can result in false high mph, but your mph for your mods is just too low. Run it a few more times and give us some more feedback so we can have more data to analyze.

 

[IT L GO]

It could be as simple that you were shutting down to soon. Keep the pedal to the metal (SMC in our case) until you pass the finish line. Keep in mind that your speed will be measured both 66 feet in front of and after the actual finish line. :cheers:

.

 

[EnzoM]

I had similar mods in my 02, and was always miffed that I could never trap above 113 mph. I am not the greatest driver out there, but I can shift well and quickly enough. I always wanted to have someone else make a pass in my car to see if they could squeeze some more out of it, but never did.

Strange when you read these posts. You have some guys trapping at 117 plus and others unable to get above 110. Go figure.

 

[sunrise]

90% of the time its the driver/weather/altitude. 10% of the time there truly is something wrong with the car. What tires were u running? The trap speed seems low and low 13's with that trap speed would point to driver error. A 12.1x with a 109 trap speed doesn't make sense as mentioned above. When you dead hook or close too it your trap speed will often be lower than if you spin alot. A high trap speed can result in false high mph, but your mph for your mods is just too low. Run it a few more times and give us some more feedback so we can have more data to analyze.

Yes I understand that 90% of the time it is the driver and I am a very new driver so am probably at fault but in putting in the numbers for the DA the weather was a cool 50F, track altitude was 1000' and the correction factor was almost dead on.

I am running on stock F1s and I can understand the low 13s and high 12s having a 110 trap but the 12.1 should not have a 110 trap as you mentioned. Here are the numbers for the 12.1 run:

R/T - 0.210
60' - 1.802
330 - 5.042
1/8 - 7.774
MPH - 89.48
1000 - 10.160
1/4 - 12.187
MPH - 110.76

On this run I did feel that the launch was dead on and I shifted as close to 6500rpm as possible...quick shifts but not power shifting.

I will try to run it again next week but please let me know if you have further ideas. Once again my mods are: LG LT headers/high flow cats/dyno tune yielding 385RWHP. Stock clutch and stock F1 tires.

Thanks.
Sunrise

 

[sunrise]

It could be as simple that you were shutting down to soon. Keep the pedal to the metal (SMC in our case) until you pass the finish line. Keep in mind that your speed will be measured both 66 feet in front of and after the actual finish line. :cheers:

.

I thought this might have been it also so I made sure I did not shutdown until I saw atleast 116-118mph on the heads-up before shutting down.

Thanks for the info though about the "speed will be measured both 66 feet in front of and after the actual finish line."

Sunrise

 

[EnzoM]

Here are the numbers for the 12.1 run:

R/T - 0.210
60' - 1.802
330 - 5.042
1/8 - 7.774
MPH - 89.48
1000 - 10.160
1/4 - 12.187
MPH - 110.76

On this run I did feel that the launch was dead on and I shifted as close to 6500rpm as possible...quick shifts but not power shifting.

Sunrise

Sunrise - I went back and reviewed my time slips for my runs in the Z. In all of my runs, I picked up about 24.25 mph from the 1/8th to the end of the quarter. You only picked up 21.28 mph on this run. All that happens between the 1/8 mile marker and the end of the strip is the 3-4 shift. (am I correct, guys - 3rd gear before the 1/8?) Your 1/8 mile speed was actually a fraction higher than my best 1/8 mile speed, so you are losing speed in the last 1/8th relative to my car.

Does your clutch feel like it is slipping at all?

When did you have your car tuned? Before or after all of your other mods? Have the car dyno'd again, and see how rich it is running.

 

[sunrise]

Sunrise - I went back and reviewed my time slips for my runs in the Z. In all of my runs, I picked up about 24.25 mph from the 1/8th to the end of the quarter. You only picked up 21.28 mph on this run. All that happens between the 1/8 mile marker and the end of the strip is the 3-4 shift. (am I correct, guys - 3rd gear before the 1/8?) Your 1/8 mile speed was actually a fraction higher than my best 1/8 mile speed, so you are losing speed in the last 1/8th relative to my car.

Does your clutch feel like it is slipping at all?

When did you have your car tuned? Before or after all of your other mods? Have the car dyno'd again, and see how rich it is running.

Hi EnzoM,

Thanks very much for your response. That was what I was thinking since after shifting to 4th I feel like the increase in MPH is quite slow. I do not feel the clutch slipping at all since I only have 10K miles on the car and this is the first time I ran at the track.

I had it dynoed at MTI in Atlanta before with just Blackwing (360RW) and after all the mods were put in: LT headers/cats/tune (385RW). Since you asked may I ask how would running rich cause this?

May I also ask if powershifting necessary to get to the 115+ MPH or would quick shifting near the limiter also get this as I did not do any powershifting?

Regards,
Sunrise

 

[robz]

Powershifting may help a bit but is not necessary. I would have expected 117 mph on that run but not sure why you didn't. Get another day in and let us know your results.

 

[EnzoM]

Hi EnzoM,

Thanks very much for your response. That was what I was thinking since after shifting to 4th I feel like the increase in MPH is quite slow. I do not feel the clutch slipping at all since I only have 10K miles on the car and this is the first time I ran at the track.

I had it dynoed at MTI in Atlanta before with just Blackwing (360RW) and after all the mods were put in: LT headers/cats/tune (385RW). Since you asked may I ask how would running rich cause this?

May I also ask if powershifting necessary to get to the 115+ MPH or would quick shifting near the limiter also get this as I did not do any powershifting?

Regards,
Sunrise

No problem at all, Sunrise. When you run rich, your car is making less power. Generally, the leaner the mixture, the more power you are making. But the leaner you are running, the more likely you are to screw up your motor.

I recall reading on this site a while back that some tunes tend to "undo" themselves in some respect and go back to factory settings. (edit - that is my understanding. I don't profess to be a tuner or tuning expert at all.) It could be that your computer is enriching the fuel mixture too much because it is overcompensating for modifications that you have made but it does not recognize.

 

[sunrise]

No problem at all, Sunrise. When you run rich, your car is making less power. Generally, the leaner the mixture, the more power you are making. But the leaner you are running, the more likely you are to screw up your motor.

I recall reading on this site a while back that some tunes tend to "undo" themselves in some respect and go back to factory settings. (edit - that is my understanding. I don't profess to be a tuner or tuning expert at all.) It could be that your computer is enriching the fuel mixture too much because it is overcompensating for modifications that you have made but it does not recognize.

What would you recommend? Should I have it dyno/tuned again?

Regards,
Sunrise

 

[COUTO1981]

Yes I understand that 90% of the time it is the driver and I am a very new driver so am probably at fault but in putting in the numbers for the DA the weather was a cool 50F, track altitude was 1000' and the correction factor was almost dead on.

I am running on stock F1s and I can understand the low 13s and high 12s having a 110 trap but the 12.1 should not have a 110 trap as you mentioned. Here are the numbers for the 12.1 run:

R/T - 0.210
60' - 1.802
330 - 5.042
1/8 - 7.774
MPH - 89.48
1000 - 10.160
1/4 - 12.187
MPH - 110.76

On this run I did feel that the launch was dead on and I shifted as close to 6500rpm as possible...quick shifts but not power shifting.

I will try to run it again next week but please let me know if you have further ideas. Once again my mods are: LG LT headers/high flow cats/dyno tune yielding 385RWHP. Stock clutch and stock F1 tires.

Thanks.
Sunrise

Congrats on that 1.8 60ft and that 12.1 with stock F1s, that's amazing times, even with the 110mph, you know If I was to observe that on my own car, I would think that I let go before the very end of the track before the race was over, the low trap could be you either shiffting to early or too late hitting the rev limiter on our cars is very normall and could be unnoticeble to the naked eye but would not come out to anythig like the 12.1, so It only seems like something at the very end, this might sound crazy but it could happen when shiffting into 4th your foot actually didnt press the accelerator all the way down, because it was against the carpet on the side, If the same thing its duplicated then I guess not, but I believe is something that silly, because even if something was wrong with your car, it would run poor through out, and 12.1 is Definetely not a poor 1/4 time o:

 

[sunrise]

Congrats on that 1.8 60ft and that 12.1 with stock F1s, that's amazing times, even with the 110mph, you know If I was to observe that on my own car, I would think that I let go before the very end of the track before the race was over, the low trap could be you either shiffting to early or too late hitting the rev limiter on our cars is very normall and could be unnoticeble to the naked eye but would not come out to anythig like the 12.1, so It only seems like something at the very end, this might sound crazy but it could happen when shiffting into 4th your foot actually didnt press the accelerator all the way down, because it was against the carpet on the side, If the same thing its duplicated then I guess not, but I believe is something that silly, because even if something was wrong with your car, it would run poor through out, and 12.1 is Definetely not a poor 1/4 time o:

Thanks for your reply. I don't believe I hit the limiter on that run and anything could have happened but what really concerns me is that I had 7 total passes. 3 of which were high 12s (12.85-12.99)...others were low 13s (2 runs), one 14s run and the 1 12.1 and none of them had anything higher than 111MPH.

I was also told on this forum that my 1/8 mile MPH is also low for my mods being only 89.48MPH on that run.

Could there be something wrong with my tune?

Regards,
Sunrise

 

[robz]

I'll ask my tuner what he thinks!

 

[sunrise]

I'll ask my tuner what he thinks!

Hi Robz,

I just talked to my tuner: MTI Racing out of Atlanta and he says that is probably normal since he has seen 114mph-117mph with my mods but it varies with driver/DA and all that jazz which I already know about. I told him that I was only getting 110mph though.

I am thinking about get some GHL Magnums and maybe a re-dyno.

Regards,
Sunrise