C4 Corvette classification?

[JeffYoung]

The car will be classed as fairly as possible. Just as an update as to where we tentatively are:

1. We will use the 205 stock hp, with a 25% gain since there isn't any real data on an IT build.

2. Car will get the ITR torque adder. The 350 makes torque.

3. We do not consider CG or stock tire width when classing.

4. The only real open item is whether double wishbones in ITR get an adder or not. Records are a bit unclear on this (the Ops Manual says they do but I agree with those who have told me this was not done on other cars in R).

I see this car as having a lot of pluses, and a lot of minuses. There's one under construction -- a good, exciting thing -- and I look forward to seeing how it does.

 

[lateapex911]

I don't recall adding for DW in ITR.

If I were king, and adding my 2 cents I'd try to keep the tq adder reasonable. IIRC there are levels, it isn't 150 or nothing, is it?

 

[Ron Earp]

I don't recall adding for DW in ITR.

If I were king, and adding my 2 cents I'd try to keep the tq adder reasonable. IIRC there are levels, it isn't 150 or nothing, is it?

It should get at least as much of a torque adder as the 5L V8s in ITR. I can't remember what they got but it sure shouldn't be less.

 

[JeffYoung]

The car has the largest displacement motor in IT and 290 ft lbs of torque.

I am pretty sure the pony cars got the 150 lb adder; I can't imagine why this car wouldn't either.

No one does recall adding for DW in ITR but the Ops Manual says it applies. We are trying to sort that out.

 

[Andy Bettencourt]

No one does recall adding for DW in ITR but the Ops Manual says it applies. We are trying to sort that out.

And don't forget that the FWD strut cars in ITR got a subtractor in addition to the FWD number further supporting that no cars in ITR got a DW adder.

The theory being that the cars are very advanced that are in there. Keeping the already escalating weight in check was a concern so instead of an 'adder' you would do a subtractor for those that needed it. "Outliers' they were called.

History Lesson for some: The concept of an 'adder' was to compensate for a characteristic that is 'out of the ordinary' for the cars in class. Obviously, those characteristics are different when you roll up from ITC to ITR.

 

[Knestis]

... History Lesson for some: The concept of an 'adder' was to compensate for a characteristic that is 'out of the ordinary' for the cars in class. Obviously, those characteristics are different when you roll up from ITC to ITR.

Quoted for emphasication. We had pretty substantial discussions about this. One implication was that ITR cars tended to have "good" suspension designs, and ITC and ITB cars tended to have crap non-driven-end suspension. Car manufacturing economics at work.

K

 

[Z3_GoCar]

Except that some ITA/ITB cars share the exact same strut front suspenstion as some ITR cars, down to even sharing the same front and rear suspension arms. Lower these suspensions and you get into the negitive camber gain. That's why these strut-suspensions were used in World Challenge with relocated/eleminated ball joint attachment at the bottom of the spindle.

 

[quadzjr]

That's why these strut-suspensions were used in World Challenge with relocated/eleminated ball joint attachment at the bottom of the spindle.

I don't think we can relocate/eliminate ball joints in IT. I would love to modify mine. Lowering the car can creates some really bad suspension juju. The offer fixes for this but they are not IT legal. One exception to this is I believe is the RX-7.

Ever driven a short wheel base car that toes out fairly drastically in bump? It can be a bit hairy.

 

[Z3_GoCar]

Ever driven a short wheel base car that toes out fairly drastically in bump? It can be a bit hairy.

Yes, yes I have

Now that this thread has taken this tangent...

Thus my point about not ITR cars have double wishbone front suspension. Yet we all get lumped in as if we all do, and I hope to remind some people that we don't.

 

[lateapex911]

But most do. Thats the point, ...in general, ITR cars do. So certain genres get a break. Now, there are some that fall thru the carack, and have something crappy, yet don't get a break weightwise. Maybe they have great power or something, like animals, that make up for a weakness with a good defense ...like a skunk.

Or maybe not. Don't race those!

 

[CRallo]

Yes, the pony cars (at least the GM's) got 150 lbs or torque adder :/

Torque adder has three levels... apparently it's very easy to quantify.

Which reminds me, the torque adder is BS, its about area under the HP curve... If anything the torquey engines that can't rev and have to shift sooner, to a lower mechanical advantage should get help. That said, I'm such a nice guy, I'd be happy to call it a wash....

The GM pony cars were processed at 30% IIRC

AND they used the wrong stock HP... (no offense guys involved, it IS confusing) I need to stop talking about it and write some letters!

 

[Knestis]

Yes, the pony cars (at least the GM's) got 150 lbs or torque adder :/

Torque adder has three levels... apparently it's very easy to quantify.

Which reminds me, the torque adder is BS, its about area under the HP curve... If anything the torquey engines that can't rev and have to shift sooner, to a lower mechanical advantage should get help. That said, I'm such a nice guy, I'd be happy to call it a wash....

The GM pony cars were processed at 30% IIRC

AND they used the wrong stock HP... (no offense guys involved, it IS confusing) I need to stop talking about it and write some letters!

We've been down that road, bought the T-shirt and mug, came home, broke the mug, wore out the shirt, then went and did the whole trip again the next summer.

Short version: The IT world wasn't ready for the complexity necessary to do it Right, so we ended up with a compromise that (1) got it kind of right (lowercase 'r'), and (2) is consistent with the preconceived notions that most racers hold on the subject.

K

 

[Knestis]

Yes, yes I have

Now that this thread has taken this tangent...

Thus my point about not ITR cars have double wishbone front suspension. Yet we all get lumped in as if we all do, and I hope to remind some people that we don't.

We never said they do.

What we said is that comparisons get made within each class, relative to what TENDS to be the case.

K

 

[Bob Roth]

I think you have made some interesting points. I looked at comparables and the car its closest to is the 944 S2. Its stock weight is 2888 so making a so subtract savings but add driver and cage and assume it 2850. The vette weighs 3184 so using the same logic, lets assume 3100pounds. So advantage S2 by being 250 pounds lighter.

Both cars have 50/50 weight balance, and they have the same size brakes. dead heat there.

The vette's advantages are 5" stock ride height, 3 inches shorter total height, 2 inches wider track, and an engine that will have a near flat hp curve if you shift at say 1/3 over hp peak, 2/3 under. (but that's what the v8 adder is for). The Grand sport has 315 -355 tires, so I asume it can fit 17" R6 Hoosier 315 front and 335 rear tires. I believe I have seen the S2 with 245's.

I think the thing that will hurt this car (as mentioned before) is the transmission. Its basically a 4 speed with overdrive but I doubt that the overdrive can be used as you would need to shift from 4th to 3rd overdrive to take adventage. It would be hard to keep track of. Essentially if you look at it, with a 4 speed its 33% drop of RPM with the shift. Ouch.

So, at 3100 pounds compared to a 2800 pound S2, I don't think, the C4 vette has an advantage. Good job. The wild card will be if people uncork the potential of the V8. The S2 doesn't have much up side, the vette could. Here are some links I found C4 Vette
1988 S2

ps the transmission looks like is a nightmare link

cheers!

 

[Andy Bettencourt]

The Grand sport has 315 -355 tires, so I asume it can fit 17" R6 Hoosier 315 front and 335 rear tires. I believe I have seen the S2 with 245's.

But the Grand Sport really has nothing to do with this situation. Having #651 in my garage I can tell you that the wheels on that car are 17x9.5 F and 17x11 R. 275's up front and 315's in the rear. This car had special rear fender flares to pay tribute to the original GS's and to accommodate the larger-than your regular LT-4 Vette's wheels and tires. The ZR-1 had similar sizes but used a wider rear section to accomodate. So now that we can put this car to bed as irrelevant to a 1984 ONLY classification:

This car, like all the others in ITR is limited to 8.5" wheels. I think legitimately, a 275 will work. Decision will be stock 16's or custom 17's.

 

[JeffYoung]

I don't agree the tranny will be the negative for the reasons you list.

It's a Doug Nash unit and pretty robust. I agree you probably won't use teh OD, except in top.

The ratios aren't terribly spaced for a 4 speed and the torque curve helps alleviate that. Top for MOST tracks will be 1:1 in 4th which is an advantage.

I think the car has potential. Comes down to power, I think everything else is there and there are a number of factors not considered in the IT process (CG, aero, etc.) that weigh in favor of the car.

I think you have made some interesting points. I looked at comparables and the car its closest to is the 944 S2. Its stock weight is 2888 so making a so subtract savings but add driver and cage and assume it 2850. The vette weighs 3184 so using the same logic, lets assume 3100pounds. So advantage S2 by being 250 pounds lighter.

Both cars have 50/50 weight balance, and they have the same size brakes. dead heat there.

The vette's advantages are 5" stock ride height, 3 inches shorter total height, 2 inches wider track, and an engine that will have a near flat hp curve if you shift at say 1/3 over hp peak, 2/3 under. (but that's what the v8 adder is for). The Grand sport has 315 -355 tires, so I asume it can fit 17" R6 Hoosier 315 front and 335 rear tires. I believe I have seen the S2 with 245's.

I think the thing that will hurt this car (as mentioned before) is the transmission. Its basically a 4 speed with overdrive but I doubt that the overdrive can be used as you would need to shift from 4th to 3rd overdrive to take adventage. It would be hard to keep track of. Essentially if you look at it, with a 4 speed its 33% drop of RPM with the shift. Ouch.

So, at 3100 pounds compared to a 2800 pound S2, I don't think, the C4 vette has an advantage. Good job. The wild card will be if people uncork the potential of the V8. The S2 doesn't have much up side, the vette could. Here are some links I found C4 Vette
1988 S2

ps the transmission looks like is a nightmare link

cheers!

 

[Andy Bettencourt]

I think the car has good potential. It's all going to be about the power however. Everything you read about the intake and injection is stupid-bad and really limiting but we shall see!

 

[Ron Earp]

I think the car has good potential. It's all going to be about the power however. Everything you read about the intake and injection is stupid-bad and really limiting but we shall see!

I believe you'll be pleasantly surprised. I faced the exact same challenge with the Mustang. All of the "people in the know" said you couldn't make power with the motor because of the intake - intake was too small, intake wouldn't breathe, etc. and so on.

Lo and behold, when the intake was actually flowed it matched the heads pretty well. And, when the heads got a valve job and the intake was carefully matched (and properly chosen based on casting date/location/suppliers and proper year gasket selection) some nice gains were realized.

The Mustang crowd on the boards were never faced with performing such an experiment. They can just slap a Ford Windstar intake on the engine, or one of the drag racing bread-box sheet metal intakes, and make good power from the engine; no R&D needed. As a result false information was circulated as knowledge - my pet peeve in the racing world. I absolutely can't stand it when someone states "if you use XYZ you'll experience ABC and go faster" and then when asked for the data they point to anecdotal evidence or on track results consisting of one lap, one race, or one testing session. Useless.

Anyway, I bet you'll find that those two throttle bodies have pretty good well. More than enough to handle the heads/cam/ports of that engine in the 3000-5400 RPM range. But you'll find out for sure when you start analyzing and investigating the engine in detail in the shop.

I like it, wish you guys would post up a build thread so we can follow along!

 

[Andy Bettencourt]

I hope we are surprised. The intake ports are 2/3rds the size of the heads. Yes some porting is allowed but it's limited. So many dyno sheets on these things that make 20-25% all have stuff done you can't do in IT. Hoping a full racing intake and exhaust with some really detailed ECU work will net what we need.

 

[Ron Earp]

I hope we are surprised. The intake ports are 2/3rds the size of the heads. Yes some porting is allowed but it's limited. So many dyno sheets on these things that make 20-25% all have stuff done you can't do in IT. Hoping a full racing intake and exhaust with some really detailed ECU work will net what we need.

You could go hog wild with gaskets and porting I suppose, but you definitely don't want to end up with the snake-that-swallowed-the-egg effect. Ending up with drastic changes in velocity in the intake, particularly in your case where the flow is carrying the fuel too, is not a good idea.

I hope it'll work out and kick ass. I'm all for more Domestic Terror and mullets in the paddock.