Interesting article on Corvette handling
09-02-2009, 09:10 AM
#1
Team Owner
Thread Starter
Member Since: Mar 2001
Location: Boston, Dallas, Detroit, SoCal, back to Boston MA
Posts: 30,596
Received 238 Likes
on
166 Posts
Interesting article on Corvette handling
http://www.vetteweb.com/features/vem..._c4/index.html
Oh, really?
The old '85 to '87 Corvettes seem to rule the autocross courses around the United States. These old C4s flat beat everything that's come out of Chevrolet since the mid-'80s. When you look at the SCCA National Championships, you'll always find some of these old torque monsters in the standings.
The point here is that, except for the Z06, the C5 is not a very good autocross car.
09-02-2009, 09:39 AM
#2
Melting Slicks
Nice article on the Shrubbers car tho...
This article documents what Roger found out when the 88 came out, so the talk about the 88 not being as competitive as the 86, was, at the time true. There were two reasons for that. The first reason was that the front suspension with the zero scrub loses camber at high turning angles, and you don't get as much grip in really low speed corners, so there is some truth to the bit that these early cars were better.
But what they don't mention is that the biggest reason that the 86 was so competitive in those years is that BFG was developing tires specifically for that car, and Roger was helping them test and develop them. Then they built something that was "close" in a 17 inch tire and those of us running 17" cars never really had the grip of the 16 inch cars. Later as 17 inch tires got better, the 88 and on cars got faster.
A few years before the "Comp TA" came out BFG went to LeMans with a 944 turbo running on "street" tires. You might remember the ads for it ,,,,, "FOR ENTHUSITS!!!!! on TV, that was a "street" dot approved tire, but it had a serious compound and had a lot of testing and development behind it. The 16 inch versions of the Comp TA were based on that tire, and were fantastic. It was really the first R compound tire and it was a whole world different than everything else out there. The 17 inch versions, well, not so much... I remember riding in that car back in about 1983 and the amount of grip it had was, compared to the real street tires that everybody else was running, simply amazing.
The shrubber was cleaning everybodys clock back then, and if you rode in his car, it was obvious why. Driving helps, but huge grip wins. Every time.
What isn't said is that most of the C4's that have been winning in the last four or five years were later 17 inch cars.
Every dog has its day....
This article documents what Roger found out when the 88 came out, so the talk about the 88 not being as competitive as the 86, was, at the time true. There were two reasons for that. The first reason was that the front suspension with the zero scrub loses camber at high turning angles, and you don't get as much grip in really low speed corners, so there is some truth to the bit that these early cars were better.
But what they don't mention is that the biggest reason that the 86 was so competitive in those years is that BFG was developing tires specifically for that car, and Roger was helping them test and develop them. Then they built something that was "close" in a 17 inch tire and those of us running 17" cars never really had the grip of the 16 inch cars. Later as 17 inch tires got better, the 88 and on cars got faster.
A few years before the "Comp TA" came out BFG went to LeMans with a 944 turbo running on "street" tires. You might remember the ads for it ,,,,, "FOR ENTHUSITS!!!!! on TV, that was a "street" dot approved tire, but it had a serious compound and had a lot of testing and development behind it. The 16 inch versions of the Comp TA were based on that tire, and were fantastic. It was really the first R compound tire and it was a whole world different than everything else out there. The 17 inch versions, well, not so much... I remember riding in that car back in about 1983 and the amount of grip it had was, compared to the real street tires that everybody else was running, simply amazing.
The shrubber was cleaning everybodys clock back then, and if you rode in his car, it was obvious why. Driving helps, but huge grip wins. Every time.What isn't said is that most of the C4's that have been winning in the last four or five years were later 17 inch cars.
Every dog has its day....
Last edited by Solofast; 09-02-2009 at 11:48 AM.
09-02-2009, 10:23 AM
#3
Safety Car
I wrote the article. I haven't seen that article for years now. Thanks for pointing it out.
You also have to give a lot of credit to the L98 engine. All of that bottom end torque is a huge advantage. Chevy sold the LT1 by talking about horsepower. The problem is you don't drive horsepower - you drive torque.
Roger should be out at the SCCA Solo Nationals - make sure you say hello to him.
Richard Newton
You also have to give a lot of credit to the L98 engine. All of that bottom end torque is a huge advantage. Chevy sold the LT1 by talking about horsepower. The problem is you don't drive horsepower - you drive torque.
Roger should be out at the SCCA Solo Nationals - make sure you say hello to him.
Richard Newton
09-02-2009, 02:35 PM
#6
Racer
Member Since: Dec 2008
Posts: 327
Likes: 0
Received 0 Likes
on
0 Posts
My '87 is still competitive at the local level. I can sum up the reason why in two words " no drama". I guess between the 3.07 gear and auto, the A6's, and all that torque you can concentrate on car placement instead of worrying about staying hooked up. Also, the car rotates more predictably than any car I've ever driven, it builds confidence. Turn the wheel, stab the brakes, rear starts breaking loose, back on the gas and it just goes where you want.
09-02-2009, 03:03 PM
#7
Race Director
The LT1 was a superior engine to the L98.. just as the LT4 is superior to the LT1 and the LS1 is superior to the LT4.. etc..etc..
L83 < L98 < LT1 < LT4 < LS1 < LS2 < LT5 < LS6 < LS3 < LS7 < LS9
and so the list shall continue..
09-02-2009, 03:11 PM
#8
Race Director
L98 torque peak 3200 RPM
LT1 torque peak 4000 RPM
LT1 torque peak 4000 RPM
09-02-2009, 03:30 PM
#9
Racer
Member Since: Dec 2008
Posts: 327
Likes: 0
Received 0 Likes
on
0 Posts
I'm sure on that running the same size A6's on my '87 and my '94 Z06 that a good driver would be faster. But at my skill level the C4 is more predictable. Don't get me wrong, I'm not saying the C4 is better, but for the age of those cars, it's special. A better driver would be much quicker in the Z06, atleast I think, but an mid-pack driver can get in alot more trouble with the peaky power. C4=NO DRAMA.
09-02-2009, 05:02 PM
#10
Safety Car
Aard - thank you.
BluByU - Did you drink all of the Kool Aid that Chevy was passing out?
Richard Newton
BluByU - Did you drink all of the Kool Aid that Chevy was passing out?
Richard Newton
09-02-2009, 08:30 PM
#11
Melting Slicks
You are absolutey wrong on this one, the LT1 is better. I've owned every year of C4 from 85 to 94 and the LT1 is better than an L98. If there is a pull were you go above 4000 rpm in any gear the LT1 buys you a half a second. Every time. Here are the torque curves and it is clear that the L98 has a bump from 2800 to 3400 but the biggest it is is only 10 ft pounds (hardly enough to make it a "torque monster" amount of difference).
The 92 LT1 was soft, but after the cam change in 93 it was better than an L98 on almost any course. As anybody who has ever driven one will tell you the L98 runs into a wall of jello above 4300 rpm where the LT1 keeps pulling like a train... Matt Braun always said he never downshifted his LT1 after he left first gear and if you look at the torque curves you can clearly see why. The LT1 outpulls the "torque monster" all the way up to 2800... So who has the low end grunt?
09-03-2009, 07:12 AM
#13
Safety Car
If you think this discussion is interesting you should see the one that's going to be coming up in a few months. I found a shop that has a C4, C5 and a C6. They were all built by the same shop. They are all SCCA IT cars.
Now we're going to use one very good driver and the same road course. The results will really surprise you.
Richard Newton
Now we're going to use one very good driver and the same road course. The results will really surprise you.
Richard Newton
09-03-2009, 07:49 AM
#14
Race Director
The old L98 just can't be matched for bottom-end torque-it'll damn near pull stumps out of the ground. The LT1s, LT4, LT5s, LS1s, and LS6s are all great horsepower engines, but each and every one of them lacks the raw low-end grunt of the old Tune-Port Injection 350. Fifteen years of technology has produced some great engines, but none of 'em can match the low rpm power of a well-tuned L98.
LS6 Torque Curve:
09-03-2009, 01:30 PM
#15
Melting Slicks
Looks to me that the LS6 is better, even down low than an L98 from 1,000 rpm and up......
Technology marches on...
One thing that you have to be careful in terms of the "seat of the pants" feel. Sometimes it is very deceptive, if the torque and power come on big time at higher rpm's it might feel like it doesn't have as much torque down low, but it really does, it just doesn't have as much compared to how big it pulls at the higher rpm's...
If you compare stock for stock the C5 is in a different time zone than a C4. If you look at a street prepared Solo II C4, prepared to the limit of the rules, it will have about the same power and about the same lap time as an SS C5Z. That is, with 315's all around, huge springs and shocks, and poly bushings all around the AC yanked and everything done that can be done, they will run about the same. In short, you had to do a heck of a lot to a C4 to get it to run like a C5Z. So can it be done, sure, and if you spend enough you can make a C5Z run like a C6Z, so what's the point?
I would also bet that your C4 IT car sure doesn't have an L98 in it if it is going to run like any C5. An LS4 can be blueprinted to get about 400 hp at the flywheel, or about the same as a LS6, so if the weight is close, you can probably get similar lap times out of each car...
The C4 was a world class car in its time, but time has passed it by.
Technology marches on... One thing that you have to be careful in terms of the "seat of the pants" feel. Sometimes it is very deceptive, if the torque and power come on big time at higher rpm's it might feel like it doesn't have as much torque down low, but it really does, it just doesn't have as much compared to how big it pulls at the higher rpm's...
If you compare stock for stock the C5 is in a different time zone than a C4. If you look at a street prepared Solo II C4, prepared to the limit of the rules, it will have about the same power and about the same lap time as an SS C5Z. That is, with 315's all around, huge springs and shocks, and poly bushings all around the AC yanked and everything done that can be done, they will run about the same. In short, you had to do a heck of a lot to a C4 to get it to run like a C5Z. So can it be done, sure, and if you spend enough you can make a C5Z run like a C6Z, so what's the point?
I would also bet that your C4 IT car sure doesn't have an L98 in it if it is going to run like any C5. An LS4 can be blueprinted to get about 400 hp at the flywheel, or about the same as a LS6, so if the weight is close, you can probably get similar lap times out of each car...
The C4 was a world class car in its time, but time has passed it by.
