My race vs a Corvette - wrong tranny? Gear? and more...

Treachery · Dec 11, 2005

My race vs a Corvette - wrong tranny? Gear? and more... Long

I went on a long distance drive with my '93GT and a Corvette came up on me on a very open road. Ideal race conditions.

My engine mods are as follows: Vortech SQ trim 8lb boost, TFS Stage II CNC Ported heads, 1:6 Roller Rockers, Stage II Cam, Vortech Intake Manifold, Accufab 65mm TB, MSD Ignition & distributor, MAC H-Pipe (no cats), 30lb Injectors, 190lph fuel pump, T-Rex Fuel Pump (came with Vortech Kit), Custom Chip w/ Custom tune.

Suspension Mods: Lakewood Drag Shocks 50/50 (rear) & 90/30 (front), HPM Megabite Jr. Upper & Lower, Kenny Brown Chassis Stiffening Kit - Subframe Connectors, Strut Tower Brace, G-Load Brace, 3.73 rear end

Transmission: Tremec TKO II - .83 OD 5th gear Transmission

More than enough to take an otherwise stock Corvette with (maybe) an upgraded exhaust?

Well... I struggled to keep up with this Corvette past 100mph. Everything in my Mustang says that i should've handled this Vette without blinking.

What i did notice during the race was that i could've used another gear. With a .83 5th gear & 3.73 rear end, i was already reving the hell out of the engine at 100mph. Also, smoke was coming out of my vents. It smelled like burning oil.

Resolution(?)- changing to a 3.55 rear end? As for the smoke blowing through my vents- I don't know.

This race happened yesterday afternoon (Saturday) and it's got me thinking...

Thanks.

Mark89coupe · Dec 11, 2005

What about a 6spd tranny?
What year Vette was it?

TT91 · Dec 11, 2005

time for a turbo

2002BLGT · Dec 11, 2005

yea need more info on the vette , whats your car weigh and what did it dyno ?

Mustang5L5 · Dec 11, 2005

Well, it's hard to hand with a vette past 100MPH when you are already winding the hell out of 5th gear. With the gearing you have, your car is more of a 0-100 car. You are judging your car against a car with AMAZING top end pull.

A vette will pull hard past 150MPH and beyond. He was probably only in 4th gear at the time right in the powerband.

So you need to decide what you want your car set up more for. You can gear it down to maybe 3.27's or 3.55's and make it an all around car, leave the gearing as is or maybe install a T-56 with a 0.63 6th gear (0.8X 5th gear)

5spd GT · Dec 11, 2005

It really depends on what model vette it was. The new one's are trapping 112mph in the quarter mile. Your mods suggest you should have more power than that but you aren't just going to murder one with a good driver. Who is to say the vette was stock or that your driving the car to the full potential. You should have been in 4th gear up to around 115mph or so...maybe a bit more. 5th gear isn't geared right anyways for racing even with the .83. The vette had a steeper gar at that point...

Steam out of vents could have been some sort of coolant leak thru the heater core?

Good Luck

Michael Yount · Dec 11, 2005

The problem was one of aerodynamics. Your 93 is a brick compared to the Vette. You need A LOT more HP than he has to hang with him once aero takes over. And remember -- the power needed to increase speed increases with the CUBE of the speed differential -- so it takes LOTS more HP to overcome aero disadvantages.

Also - how do you know the Vette was stock?

If you're gonna race top end with a Stang against contemporary cars (with a LOT better aero) you better bring a butt-load of HP. And, of course, having it geared so that there's a match between rpm, power peak and top speed helps too...

iapexl8r · Dec 11, 2005

you did not mention tire size and rev limit?? if your running a 25 " tire with 373 gears your top speed will be 125 mph in 4th gear @ 6250. your .82 od is pretty small so if your running 26" tire top speed in 5th should be around 150 @6250 hmm did you tach it out in 5th??? chris

mackey · Dec 11, 2005

Mark89coupe said:
What about a 6spd tranny?
What year Vette was it?

The T56 is the same but it puts a gear inbetween the 3rd and 4th or 4th and 5th so the overall ratio is the same I thought. That is why they called it the road racing tranny.

Mark89coupe · Dec 11, 2005

Here is an example of the vette's.
I drove a 93 auto (Vette) over the summer. I took it out on the hyw to see what she could do. I got up to 70mph and stood on it. It shifted down into 2nd and didnt hit third untill 98mph. I let off at 130.
Thats just the automatic stock 300hp vette. The 6spd LS1 must be a total animal.

Michael Yount · Dec 11, 2005

And the Vette (and the Viper) hits its top speed in 5th gear, not 6th -- so it's all about matching the final gearing to rpm at which the engine makes power.

5spd GT · Dec 11, 2005

Mark89coupe said:
Here is an example of the vette's.
I drove a 93 auto (Vette) over the summer. I took it out on the hyw to see what she could do. I got up to 70mph and stood on it. It shifted down into 2nd and didnt hit third untill 98mph. I let off at 130.
Thats just the automatic stock 300hp vette. The 6spd LS1 must be a total animal.

Yeah the autos have something like 2:58 gears or something like that. 2:53's if you don't get the "performance axle ratio" as an option. Just remember where are car shifts out in a gear doesn't mean it's faster. I get that question all the time, "where does your car shift out of 3rd gear" and people get dissapointed when I tell them 85mph. They think my 00 Gt is quicker because it shifted out at 97ish or so mph in third

timewarped1972 · Dec 11, 2005

as mentioned above i think the aero dynamic factor is a huge one. after you start getting up around 80 or 90 mph it's creating some drag big time........
curious, are there any web sites with wind tunnel drag coefficient tests for cars and the results?? like with different years and makes of cars......

86bluecobra · Dec 11, 2005

with drag shocks wouldn't this amplify the flying brick problem not letting the front of your car come down low thus creating more drag @ 100mph and beyond.

_jb_ · Dec 11, 2005

Mark89coupe said:
The 6spd LS1 must be a total animal.

Nah, try the new Z06 coming out. LS7, sb427 505HP runnin the quarter at 11.4 secs. That's an aminal!

Sicarius428 · Dec 12, 2005

Michael is right. It is the aerodynamics. You are trying to contednd with the vett in it's territory. Say if you had the same body with your power... you should be able to take it granted that it was also stock. A lower rear gear will help on the freeway since you seem to have the power but your lower end will suffer.
Kevin

Michael Yount · Dec 12, 2005

Drag coefficient by itself won't help much -- you need the frontal area of the car too. Some mags like C&D list Cd in their car specs, but hardly anyone has the frontal area of the cars.

Dark Knight · Dec 12, 2005

Sounds like you might have some probs to me.. your car should be trapping at 110-112 with the mods you have, 100mph shouldnt be a big deal.. and the rpms shouldnt be THAT high in 5th at 100... I run through the traps at 6k and 103mph in 3rd with 3.55's with a mild setup and stock cam

If you're getting smoke through the vents, you might be getting alot of blow by, 'specially if it smells like oil.. clutch might be slipping some too..

Treachery · Dec 13, 2005

After some more testing, i've discovered that the smoke is not coming from the vents but rather from the center console where the stick is at. Looking under the car and it's moist.. oily. I think my oil gaskets are compromised. I'll have the clutch looked at while i'm at it.

The Corvette that went up against me was the last generation Vette.. not the new shorter model. I'm pretty sure it was stock because he tried reving his engine at me when we slowed down and i heard and saw nothing to suggest that it was fixed up.

But that aside, i should have took him. Yes.. i have a brick for a Mustang like most of us do.. But a fast brick at that. I could tell that the guy did floor it but i on his tail, almost tailgating with him all the way but i was red lining my Mustang. My Speedo and RPM move almost in unison (1:1).

I believe the last generation Corevette had 345hp stock. Let's say 360hp if the exhaust is upgraded. I dyno'd at 465hp 2 months ago! I understand the aerodynamics explaination and i agree with it. But I should have whooped the Vette.. Bar none. Real life senario. I dunno. I'm probably in denial... Wait.. NO I'm not!

The more i think about it... On a standing stop... yes! I will crush the Vette. But at the high-end is where the Vette shines. I agree my Mustang is a 0-100mph car with this gearing. I will try dropping to 3.55's. The Vortech should make up for the lost low end. I demand the best of both worlds!

I'm running the stock 16" pony rims but with 245/50's - BTW.

How does going to 3.55's at the rear and 17 inch rims sound? What size of tire would be a good fit? Time to break out the calculators.

Michael Yount · Dec 14, 2005

Going to 3.55's and 17's will make your car accelerate more slowly at all speed ranges - assuming traction is the same. Not sure why you think that approach will help. The gearing will reduce torque multiplication; and the 17's will weigh more than similar height 16's -- it takes more power to turn the heavier wheels. And if the 17" package you put on is TALLER than the 16's, that will further reduce your gear.

IF your car is redline limited in 5th with the 3.73's - then 3.55's may give you more top end speed -- but it will take you longer to accelerate to any given speed.

You need more power or better aerodynamics to pull harder at high speed.

By the way -- your EAR (he tried reving his engine at me when we slowed down and i heard and saw nothing to suggest that it was fixed up.) is no way to tell whether he was stock or modified. I'm not suggesting he was -- just that you really have no way of knowing whether he was stock or not, or how hard he was trying.

If you're happy with the way your car runs/drives -- I'd forget about it. Enjoy your car. There's ALWAYS someone that's faster/quicker....

My race vs a Corvette - wrong tranny? Gear? and more...

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