Corvette Suspension: Is it worth it?

[silicone boy]

I've been reading with interest the subframe reinforcements that several members have done (especially Pete). Since I get obsessed about things, I thought, heck why not a full tube frame (if I get around to it over the next couple of years). Then I saw someone who is doing a tube frame with a Corvette C4 suspension. I have done a full, maxed out suspension rebuild with coil overs, big brakes from Ross and Mike SCCA, tubular suspension arms from Mike Kelly, CV conversion from Ross, as well as a Quaife in an R200 (also from Ross-he has some great stuff and gives good service). It's pretty maxed out and hasn't even hit the street yet. A rolling Vette chassis may become available. Is there any major advantage to swapping my current setup out? I'm setting up my car as a performance street and track/autocross car. I know some have switched to the vette rear for drag racing. Ross told me that the Quaife has even held up well in modified Vipers, so I think my setup should hold up to the 400+ HP I'll be getting soon (I might sneak in an occasional squirt of nitrous ). It looks like it would be a fun project and I love the way a Vette handles. I'm not sure if a Z would handle any better with Corvette components front and rear, but I'd like your opinions. I'm just not sure that the gain, if any, would be worth the effort.

[Drax240z]

From the sounds of things, you haven't even driven your car with the new setup. DRIVE IT FIRST!

 

I think the benefits of the vette rear are: a) its a fair bit lighter you can get some really low (numerically) gear ratios. I believe that is the reason why most guys go with it, since its near impossible to get a R200 with anything lower than a 3.36:1 in it, and even finding those isn't easy.

 

It's a cool mod, but I don't think it is worth while unless you really need that lower gearing.

[Pop N Wood]

If you want a vette then why not buy a vette ?

 

I am not trying to be a smart ass or disrespect anyone, but this is something I struggle with in planning out some of my intended Z car mods. It seems like my list of "if I could only afford it" upgrades makes me wonder if I am just trying to build a vette. At which point I ask why not buy a damaged vette and strip off enough creature comforts to get the weight closer to what a Z with chassis reinforcements will weight.

 

And don't say "but then it wouldn't be a Z" because at some point grafting Z body panels on a vette chassis says the same thing.

 

Besides, most of the vette front and rear set ups look like they will add a good bit of weight. I will be very interested when some of the on going projects get complete enough to get on a scale.

[silicone boy]

Excuse my ignorance, but what is the real benefit of lower gearing. You would have a faster top end, right? But doesn't it hurt your acceleration (that's why drag cars use 4.11 gears, right?). As far as weight savings, Scottie said it only saved 80 pounds (not insignificant, but not like 200 pounds)

[silicone boy]

Jim,

 

You are exactly right. I'm probably going to pass on the rolling Vette chassis, cause I thought, if I want a Corvette suspended car, why not just get a Vette? It's too easy to get carried away with this stuff. I, too am interested in seeing how some of the ongoing projects turn out. I'm not sure if they will be an improvement, but then again, we'll never know until someone tries. In my line of work, they have a saying: "the enemy of good is better", and I've found that to be true time and time again.

[Drax240z]

I still don't understand "everyones" facination with the corvette. I must be missing something.

 

I believe I recall Scottie changed to the vette rear because he didn't want his 4 speed auto to shift into overdrive before the 1/4 mile finish. Normally you'd want higher (numerically) gearing when drag racing, as it multiplies your effective torque... However, there are cases when you don't want it, even in drag racing.

[DavyZ]

Excuse my ignorance, but what is the real benefit of lower gearing. You would have a faster top end, right? But doesn't it hurt your acceleration (that's why drag cars use 4.11 gears, right?). As far as weight savings, Scottie said it only saved 80 pounds (not insignificant, but not like 200 pounds)

 

I want to make sure I understand what you are asking: NUMERICALLY lower--meaning 'higher' gearing. 3.36 gears are higher but numerically lower then 4.11's. Correct? I think I understand...Scottie wants higher (numerically lower) gearing for his GN powered car since his engine produces the best power and goes through the traps with those gears. Otherwise his car won't get down the 1320 fast enough. Going to a 4.11 gear ratio doesn't work for his particular car. 4.11's work great for underpowered L6 powered Z cars or heavy American muscle cars, but when you get a V8 powered Z car....then the higher gears (lower numerical gears) are great. At least I hope I got that right...

 

 

Can we call you "Boob job boy?"

 

Davy

[CruxGNZ]

Can we call you "Boob job boy?"

 

Every time I see one of his posts since he revealed what he does for his day job, I don't know why but I kinda giggle knowing that he gets to umm, work over boobies What a life you have Silicone Boy, by day a woman enhancer, by night a Datsun enthusiast

 

!M!

[silicone boy]

I have to say I love my day job, and my night job. Big contrast though. I usually go to sleep obsessed with visions of the wiring diagrams I've been working on all night, then dreaming about the boob jobs I'll be doing in the morning. I love my life .

[Scottie-GNZ]

Let me start off by saying if the R230 was available with a ratio of around 3.00:1, that is probably what I would be running today.

 

Let me help clarify some confusion about gear ratios and why I run such a low-numerical ratio and the C4 IRS. A few of you hit on some of the points but let me tie it all together. As Drax said, typically drag racers run a higher numerical ratio to go quicker but that does not necessarily apply to turbo cars, especially turbo cars that make monster torque down low. DavyZ pointed out that the higher numerical ratio increases torque multiplication but that is not something a torque monster needs coming off the line. The lower numerical ratio will not hurt a high-torque turbo drag car off the line and turbo cars will perform better when given the chance to build boost not rev quickly through the gears. With turbo drag cars there is a tendency to think more about lag off the line than to think torque. However, a well setup turbo engine is probably going to have a peak torque of at least 40-50% more than an equivalent size NA and in my case I estimate between 550-575 lb/ft at low RPMs. Keep in mind that with forced induction, for every 1bar of boost, the engine is capable of doubling the volume of intake charge it can pack into its cylinder. IOW, a L28ET at 14.7psi is capable of ingesting 5.6L of intake charge into its 2.8L displacement. That makes for a big bang and helps explain why a turboZ running boost in the teens performs equally with a V-8 Z.

 

With an upper rev limit of about 5500+ and a .67:1 OD ratio, shifting into OD had too steep a drop-off in RPMs and hurt top-end acceleration. I had to find a ratio that would keep the car in 3rd gear when I cross the line at 130+. I costed out solving this with an R200 and needed a LSD, NISMO 3.0x R&P, R&P swapout, special axles (ask Stony how much his cost). An alternative was a SupraTT IRS with a 3.15 or the C4 with a 3.08. By luck, I landed the C4 cheap and then it turned into an engineering exercise .

 

Will a Z handle better with C4 IRS than with a stock IRS? I certainly would not make that swap just to get better handling. The Z IRS is proven in competition and the Z/C4 IRS setup is getting into dark territory. Personally I think my setup has the potential to handle better, what with camber, toe and bumpsteer adjustments, plus I replaced the C4 monoleaf spring and tube shock with a coilover/adj shocks that mount in the stock strut housing. However, I am obsessed with drag racing the Z and never have and probably will not explore that avenue. When I want to "carve canyons", I drive the other car. So why did I make all those mods? I just would not have done it any other way .

 

So, unless you have special gearing needs like I did or just want to delve into pioneering engineering exercises, you probably do not want or need a C4 IRS. BTW, to emphasize the point about lower numerical ratios and its effect on drag turbo cars, ponder this. I started the GNZ with a 3.90, then went to a 3.70, 3.54, 3.36 and now 3.08. The car now cuts mid-140s 60' and goes through the traps at about 132mph @ 5500+. So even with the 3.08 I am up against the same problem I started out with. I will end up going to a slightly taller tire (have 26.1" now) and you can bet the car will be quicker and faster and the icing on the cake, GET BETTER GAS MILEAGE!.

[Mike C]

2.73 are easy to get for the C4 diff as well, Scottie.

[Michael]

Well, one reason for mixing Corvette suspension components with Z sheet metal – instead of just modifying the Corvette itself – is the same as the reason for swapping a Chevy engine into a Z in the first place: you choose the best aspects of two entirely different vehicles, and build a combination vehicle – a.k.a. a hybrid – that is superior to both. That said, I am not impressed with the C4 suspension design, nor do I believe that a ladder frame designed to accept C4 front and rear suspension, plus the Z unibody, plus a roll cage, plus all the tabs and gussets and protuberances necessary to hold everything together, will weigh less than a Z unibody with aftermarket bolt in-type suspension components and a tube frame integrated into the unibody, without the ladder bar frame underneath. So even with “unlimited resources” I personally would not prefer grafting in a complete Corvette suspension. What I do daydream about is a true custom suspension, double A-arm on all four corners, with a Ford 9” differential, wrapped in custom body panels.