I haven't been back to the track yet. Mine has 9K miles and will spin em in 3 gears if I rip the shift hard. But if I do a good shift that plants the tires it feels like it might slip a bit. I dunno if that's normal and I just had a bad day or what.

 

My questioons are :

What was your mile per hour in the 1/8 th mile?

How many mph did you gain in the last 1/8th mile of the track compared to your friend....It takes horsepower to pull strong after the 1/8th mile.

What was your mph in the 1/4 mile ?

You need to compare these to your friends car first.

Then you need to think about the day and how things transpired...Did you sit at the line with the hood closed with engine idling causing underhood temps to escalate.If you did there is a chance that when you left the line your engine was breathing air temps higher than 100 degrees.....Remember that the pcm pulls timing with air temp increases.Once moving they will come down.


I feel that the next time you go too the track that you should invest in 10 gallons of race fuel(100 octane unleaded-This will rule out detonation) and keep your hood open all the way up to and before the burn out box.Then make a pass.


Feel free to email me if you have any questions...With thise 60 ft times I feel you will be there soon enough.


andym@airmail.net or zo6parts@airmail.net

 

Those are large gains!!
Ron

 

What was your mile per hour in the 1/8 th mile?
What was your mph in the 1/4 mile ?
88.50 mph 1/8, 112.78
88.97 mph 1/4, 112.42 (both with 1.94 & 1.96, 60')

Well (friends car) actually he's a forum member never met him and the last time I talked with him he could'nt find his slip form the weeks before runs! I'm pulling 24.278 mph from the 1/8 at the best.

(underhood temps) no problem there! we set the fans on at 194 deg's and I never see 195 even coming to the line.

(10 gallons of race fuel) I brought the octane unleaded up to 93 last time out "for the race track day from hell" racing time from 12-4 pm
the track ran the the supper comps till the street racers first pass at 4:25 pm track cooled and I got a 2.05 60' and 12.74 at 113.21 my fastest mph ever, that was it at Sacramento race track and my last till I run Vet Magic June 1st.

Note: found a loose exhaust manifold sheiding on the engine, the nuts had backed out, it moves in and out about 3/8" possibley the virbration item we seen on the Dyno and may be causing the computer to retart.
Will let you know.

 

Qoute:

"(underhood temps) no problem there! we set the fans on at 194 deg's and I never see 195 even coming to the line."

If your engine is 190-180,Your AIR TEMP is over 100 degrees.

The Pcm pulls timing over 100 degrees,as much as 6 degrees if the temp is high enough.

Once the car starts moving,the z06 screens will help air flow into the factory airbox lid or air filter area.Do you have a factory airbox or a donaldson blackwing?These pull their air from under the hood which is not good.If you have a Breathless Airbox,MTI Ram Air than discard everything I have typed above.These airboxes pull air from outside the engine bay.

It looks like your horsepower is there.....24 mph gain is very good for a stock car.

Your 1/8th mile mph is low and if I had to guess,Your 1/8th mile time is probably not that hot..It could possibly be that you are spinning real bad in 1st and 2nd.

I would get some drag radials and watch those 60ft times fall along with you mph going up.It is obvious that your car is making the power from the mph after the 1/8th.These cars react very well with traction.Start searching for that next.


1 LAST NOTE - I was making 460 rwhp and gained 26.2 mph after the 1/8th.My time was 11.131@126.20 and 7.207@100. Slicks and skinnies with 1.67 60 ft. The most important thing is that first 1/8th mile.

 

Thanks for the great info. I don't under stand following:

If your engine is 190-180,Your AIR TEMP is over 100 degrees.

by 100 degrees do you mean the differance from engine temp. to outside temp.? (engine at 194 deg's and the air is at 70 deg's now, a differance of 124 degs. your saying can't be over 100?? to or will retard. Please explain futher. I can't see that ever happening as normal engine temp. at the track is around 210.

Airbox type unknown, connects to the stock factory bridge, chromed and "Y" shaped with two K&N's on the ends, does'nt extend to sreen area.

drag radials, problem is I live 100 miles from the track and offten have to go thru water area's in the streets coming down from 7000' in the mountains to the races. the F1's are the limit for bad traction in that mess, and I've seen other threads claiming 1.69, 60' with F1's (of corse trhat's with line RMP's as high as 6000 to 6200 RPM I'm not doing that to my clutch, with it my only ride home.

With a 1.94 to 1.96 60' time leaving at 3200-3500 RMP's do you feel I'm breaking loose bad? I had a friend watch at the line durring a 2.05 time and he said I let loose about 15' on that run but the track temp. had started cooling did'nt get a ground temp. reading that day.

Thanks for the: (26.2 mph after the 1/8th) That really indicates a first half problem on mine.

 

His 26.2 mph gain is due to his higher rwhp.
1.9x consistently is pretty good on F1's...It's all about throttle modulation & traction.
I don't think it's possible to launch on F1's at or even close to 6000rpm's & get a decent 60', let alone a 1.69 60'.
EVen when I hit a 1.711 60' on F1's, it was at a rental w/ a nicely prepped track & in excellent weather conditions w/ a perfect launch at 4200rpms. I tried above that but just spun. The rest of my better launches were in the low 1.8 range.
Ron

 

Ha, I would be the buddy. I am stuck in Hawaii for 6 months on buisness so I wont be around the Sac area any time soon. Email me Sid and I will fill you in on the details.
Robert

 

Bogging the car off the line cost me a ton of mph. Shifting too low on the 3-4 shift also cost me mph.

Here is a synopsis of my car going from 12.77 to 11.933.

http://www.z06vette.com/forums/showthread.php?t=25298

You might have your friend drive the car to see if its a car issue or a driver issue. Since th HP shows to be there, I'm going to have to suspect it launch and shift related at this point.

 

J-Rod this was out standing info! thanks from me, looks like some of my lost in MPH is in the launch, with my other cars I've raced, I've always noticed an increase in MPH when traction was lost at the line, from what your showing it's just the reverse with our Z's. The 1/8 mile times tell me I'm already down by 2-5 MPH. Plus 22 Psi's in the rear I've droped to 27 but did'nt try lower (I will next time out) I do'nt think I'll ever stage at over 3500 RPM's it's a long walk home so I do'nt want to blow a clutch.
As for shift related, no problems there. I shift quick and as close to the rev limiter as possible (6350-6400 RPM's)
Thanks again, Sid

 

No, I agree. Wheelspin will gain MPH. The issue on our cars is if you bog them badly at the line they loose mph on the big end as you have a shorter distance in which to get the car moving.

Think about it this way. A flywheel is like a battery, it stores energy. In my case I launch with alot of rpm so I have potential energy stroed int he flywheel that is already there before the car crosses the beams at the starting line. That is energy the car doesn't have to generate after the clocks start.

That potential energy is then converted into forward motion (when I release the clutch). Now, if I have no energy (or much less, like from a very mild launch) stored in the flywheel, the engie is going to have to make that energy after the clocks are running. Thats time and energy that is required to get the car moving, and thus it takes more time to get to the end of the 1/4 mile.

Good E.T. are just about maximizing what power you have along with the avaliable traction....

 

I under stand.
I just went back through my slips and found my MPH at the 1/8 did pick up 2 mph when I lost a ten to the 60' once.
I ran a 2.05 60' and a 90.56 (insead of the 88.50 & 88.96's) @ 8.345, 1/8 to a 12.74 & 113.21 mph
From your synopsis of "12.71 getting better" our times are amost identical, even that run your: 2.159, and 90.69 @ 8.355 to 12.71 & 111.41
My next effort will be correcting the loose exhaust manifold sheiding on the engine, the nuts had backed out, it moves in and out about 3/8" possibley the virbration item we seen on the Dyno and may be causing the computer to retart durring some runs (we seen it on the dyno), and I've begun indexing the plugs only to find out the original ac 41-974's are no more. I need two to finish, but shall grind the bodies of these to clock em. The original plugs 41-974 gaped at .060" are now 41-985 gaped at .040" Which are you runing??

 

Good advice again.

 

Power shifting is worth a usual .3 and 3mph gain, the 1-2 powershift really does not gain anything because of the wheel spin, but the 2-3 and 3-4 power shift will gain you some more.

 

I rip the shift as hard as any racer could. Out come feels good, loose about two or three spins in 2nd.
My thread is in search of a racer that has a problem with a car pulling a good RWHP but not the MPH to match.
I find looking at other racers slips I'm runing the exact times in the 60's, 330', 660', 990', an end result mph and et, as the other stock 353 rwhp Z06's (but with 388 rwhp) " this is my reason for looking to some thing other than my driving causing a lost of mph due for the 35 wrhp"
May be my dyno shop made an error and I don't have that they said I have, (we did 7 runs, an they verified the calibration prior) that I could accept, but a fellow fourm Z06 members car turning 115 dyno'd the less (-35) I can't. (but then, I did'nt see that slip!, I did see the aboves slip with that hp diff.)
I have corrected the 2nd. possible vibration item I have found but it apears it will rain or snow every week end for the rest or the year.
so no tract test.
Thanks for you throughs again.

 

Trust me, you can shift it as fast as you want letting off the gas, you will pick up 2-3mph keeping your gas pedal flat on the floor.

Friend of mine used to think that he shifted fast enough that it didnt matter. So one night we were at the track I told him to make a pass. I then drove the car, .3 and 3 mph faster than his best time. with the the same 60' time.

Next time when you compare someone else, ask them how they shifted.

Like I said though, dont bother with the 1-2 shift, I get really bad wheel hop when I do that, but I power (or flat foot) shift the car in the 2-3 and 3-4 shift.

Also, make sure you are not letting off the throttle till you pass over the true finish line, there are usually a few white lines across the track.

 

Z06 Tech
Excuse, got ya, some thing I've been staying away from but I guess with the rev limiter to cover my azz if I miss one I don't have to worry.
Do you (under a power shift) begin the clutch press around 6000-6200 rpm? a few rpm's lower, I would guess!
I will reavaluate and find out on the other three possibilties you have menioned.

 

Here is the trick, is to apply pressure to the shifter in the direction before you hit the clutch pedal rather than wait to pull on it once you start pushing in the clutch. As for RPM I usually shoot to start the shift right where you normally would, with a proper shift you usually will only get a 100-200 rpm increase in between gears. Warning though, I went through 1 trans in a 5.0 Mustang learning and borke the 2nd one after a lot of passes, but thats also a T5 which is a weaker trans, when I started running the Tremec 3350's I never ran into any problems. The T56 will take a pretty good beating, but if its done weekend after weekend, you will eventually have a problem. The Mustangs I used to do it on the street all the time. The vette I save for the occasional pass down the track.

 

I went back thru my log and found a series of passes I made at Maryland International Raceway on a very hot day in June 2002. I was running bone stock on stock tires. The density altitude was about 3500 feet, although the actual altitude of MIR is 80' above sea level. The barometer was unusually low, around 28.80 inches.

In those conditions my car ran most passes in the 12.28-12.41 range but the trap speeds were almost all in the 112s, none lower.

The previous weekend at a DA of 2200 feet, it ran traps of 115-116.

So, soblad, what is the name of the track you were running the low traps on?

Ranger

 

Hello Ranger,
Very interesting,
(altitude= 3500 feet, actual altitude of is 80' above sea level. The barometer unusually low, around 28.80 inches).
I always check air temp., and Humidity but not the barometer. I tried to find out the actual altitude of my track; Sacramento Raceway at (95827) but no luck!
With your (passes in the 12.28-12.41 range, with 112's) were you full pedal or power shifting??
Another forum member mentioned that as maybe some of the reason for my mph being lower vs others with less hp going faster.
Durring those passes above (12.28-12.41 range) that tire pressure were you runing, my lowest has been 27 lbs but have seen racers using lower in their threads. (As low as 22 lbs.)
Sid