two 91's why is one faster then other one

corvettelover · 09-07-04, 02:00 PM

Hey fellow Vette owners l am the pround owner of two 1991 Corvettes one is a coupe and the other is convertible.The coupe for some reason is much faster then the convertible(a noticeable difference).The coupe has a High performance Pulley on it and performance exhaust and that is all the difference between the two.Would that make a huge difference on the performance.I should say that l didn't do this mods to the coupe the other owner did them not me so there could be something else l am missing.Any info would be help full Thanks Danno

Tuna · 09-07-04, 02:38 PM

The vert weights a lot more?

Have you weighted them?

The x-brace and other chassis additions add a lot of weight to the car.

sleepyhead · 09-07-04, 02:41 PM

Do they both have the same gear ratio's? Maybe one has the performance axle ratio which could account for slightly quicker acceleration. (I'm assuming that they are both auto's since you didn't specify.)

-J.

Edmond · 09-07-04, 02:45 PM

I think the convertibles weighed more.

corvettelover · 09-07-04, 02:50 PM

No l haven't weighted them but l am sure that the rag top weighs more and yes they are both autos,and l have not checked the gear ratios but l will and reply back but would all this make a great diffence because it is so much more faster then the rag top would the mods make any difference Thanks Danno

Moonunit 451 · 09-07-04, 03:01 PM

Quote:

Originally Posted by corvettelover

No l haven't weighted them but l am sure that the rag top weighs more and yes they are both autos,and l have not checked the gear ratios but l will and reply back but would all this make a great diffence because it is so much more faster then the rag top would the mods make any difference Thanks Danno

I bet it's the rear gears. The mods metioned will give you a few ponys, but a higher rear gear would account for the major difference you describe.

Tuna · 09-07-04, 03:03 PM

Quote:

Originally Posted by corvettelover

No l haven't weighted them but l am sure that the rag top weighs more and yes they are both autos,and l have not checked the gear ratios but l will and reply back but would all this make a great diffence because it is so much more faster then the rag top would the mods make any difference Thanks Danno

Check the RPO sticker under the console lid or right rear compartment lid for options specifically for the gear ratios. GM1 = 2.59, G44 = 3.07, GU2 = 2.73. Unless your cars have had the gears changes, this should save you crawling under the car and counting turns on the drive shaft.

vader86 · 09-07-04, 05:47 PM

Well the pulleys and exhaust can make up about 20hp, proven on L98s.

Combine that with extra weight for the vert and probably different gear ratios (but not a huge difference in the stock gearing) and youll get a couple car lengths difference in a 1/4mi.

corvette66 · 09-07-04, 07:16 PM

Is there a big difference in the odometer reading? I know my 86 with 140,000 wouldn't hold a stick to a 40,000 mile 86.

simple things like bad fuel filters could cause a great power loss.

Edmond · 09-07-04, 07:31 PM

Quote:

Originally Posted by corvette66

Is there a big difference in the odometer reading? I know my 86 with 140,000 wouldn't hold a stick to a 40,000 mile 86.

simple things like bad fuel filters could cause a great power loss.

Naturally. The older car is presumed to run slower than the newer car. It's just like a younger athlete versus the older athlete.

Mad-Mic · 09-07-04, 11:20 PM

the tune of the car is what matters. if it's in proper tune and you take care of it ie chaning the fluids then the cars should be fairly close. probably with in 1 car length in the 1/4 mile as long as the gearing is the same.

if one car has had a full tune up and the other one not in 50k+ miles then obviously the newer tuned up car will win.

corvettelover · 09-07-04, 11:24 PM

Well checked the gear ratio and the coupe is the G44-3.07 and the rag top is the GU2-2.73 so are you saying that that is why the difference,can l change that with the same modes as the coupe,l know it won't be the same but do you feel that it would be better or not throuht the trouble.And l hear that the performance pully can cause the alt not to charge as it should has anyone heard of this problem Thanks Danno P.S now that l look at my charging on the coupe it is better on the rag top is this the case or am l crazy Again Thanks

corvettelover · 09-07-04, 11:27 PM

Quote:

Originally Posted by Tuna

Check the RPO sticker under the console lid or right rear compartment lid for options specifically for the gear ratios. GM1 = 2.59, G44 = 3.07, GU2 = 2.73. Unless your cars have had the gears changes, this should save you crawling under the car and counting turns on the drive shaft.

answered the question

G Winter · 09-07-04, 11:38 PM

3.07 to 2.73 gears could make a big diff. in the low end . Add in the mods and it is easy to see why you have such a diff.

Edmond · 09-07-04, 11:54 PM

Quote:

Originally Posted by corvettelover

And l hear that the performance pully can cause the alt not to charge as it should has anyone heard of this problem Thanks Danno P.S now that l look at my charging on the coupe it is better on the rag top is this the case or am l crazy Again Thanks

The performance pulley also causes you to use more effort in steering. I'll try to post that thread.