VenkmanP

Quite a few people here who need to pay more attention to the world around them. All of the skeptical questions about the STS rear-mounted systems have been asked and answered years ago.

Rear-mounted STS turbos on LT1 F-bodies are old-hat by now. A C4 LT1 system should not be much different performance-wise. The F-body system also gives you a lower limit estimate on the cost of the C4 system.

doug_dayson

In CA many C4's are getting to the age where they have to go to "test only" stations, so it's harder to have a friend look the other way etc.

That said, since most of it's behind the CAT it seems to me that one could merely disconnect the Turbo Discharge tube, reconnect the factory Air Bridge, and swap in a tune that'll pass smog (that'll hopefully pass with big injectors etc)?

To my mind, it's a CAT BACK

doug_dayson

Is this going to run a Intercooler?

Even if no CA EO is in the works, to my mind it's a CAT BACK device and thus exempt if the Turbo's Discharge Tube is diconnected and the stock Air Bridge reconnected, and the tune swapped out etc?

L98 should be easier as it's really a single exhaust anyway!

Great, looking forward to this

86VX1

hey RH, how much space is between that muffler and the gas tank?

tobijohn

FYI, the price on the STS web site for the 94-97 LT1 F-body system is just about $4,000...

rhanselman

You will have the option. Both test cars have the intercooler.

rhanselman

Please read the first post, there will not be a muffler. The tail pipe will Y into duel outlets... Picture is of the initial setup...

rhanselman

This is correct and is what we're shooting for... Also take a look at the performance specs. You will be impressed...

The amount of boost we will run is still up in the air... More to follow...


http://ststurbo.com/lt1_camaro_dyno

Boost: 7 psi
Rear Wheel Horsepower: 394
%'d increase: 44%

Rear Wheel Torque: 449
%'d increase: 48%

Boost: 12 psi
Rear Wheel Horsepower: 598
Rear Wheel Torque: 637

Dyno testing was completed at Phantom Motorsports in Murray, Utah. Elevation: 4226 ft

tobijohn

OK, now we need to know what drivetrain upgrades are necessary to handle all of this...

rhanselman

Leave the stock tires on and you won't need any

95wht6spd

There are plenty of these on C5's, and from all that I have read, lag is not an issue, plus it's a V8, not a little 4 banger that needs to wind up.

These are easier to install, have less heat issues, and the weight is in the back. Everyone has been wishing for a C4 turbo system for years, it's about time someone actually did it!

Kurac

I checked out the STS site, looks like the options can really get pricey and add up quick once going to a bigger turbo and other mods...

Eitherway, I wonder how much extra oomph the base kit would provide to my forged 383 I should have by spring....

JD'S WHITE 93

I am very interested in this, however I have a couple of questions.
How would you launch a C4 with a rear mounted turbo ? I've seen the turbo Buicks build boost at the line and leave on the boost but I'd be very afraid to try it with a halfshaft Corvette. I have a 2800 stahl converter and 3.73's and wonder if the turbo would make my car considerably quicker or if it would just boil the tires worse than it already does.

marksp

Hey what about us L83 guys?

I know its a stretch, but really, how much different are the l98 & l83 cars from the headers back. I have a setup off a previously supercharged l83 on the way. It includes an offy intake, bored throttle bodies. and a custom air lid.

Check this site, it belongs to guy how created this setup.

http://www.joby.se/corvette/mods/2001-0X05_air_box/


Mark

neat

The extra volume of the charge pipe is less than an average intercooler volume, so from that stand point the turbo in the rear has less volume to fill than the front mount system.

If you think about how much air your engine moves (350 cubic inches every rotation, volumetric efficiency aside) that's a staggering amount of air to move through a 3 inch pipe.

At idle, you are moving 262,500 cubic inches of air per minute assuming a 750 RPM idle. That's 4,375 cubic inches of air per second, which breaks down to roughly 2.5 cubic feet of air per second. If your exhaust system is equal to 13 feet of 3 inch tubing, that is also roughly 2.5 cubic feet of volume. So, at idle, you are completely changing the exhaust system gasses once a second.

At 3000 RPM's, assuming everything is equal, you are moving roughly 10 cubic feet of air per second, or completely exchanging exhaust gasses every .25 of a second.

At 6000 RPM's you are moving roughly 20 cubic feet of air per second, so you are changing exhaust gasses once every .125 of a second.

It's almost difficult to comprehend how fast the exhaust gasses are moving through the system. Even if you cut the exhaust volume in half by moving the turbo up front and somehow cut the lag to 1/2 of what it is in the rear mount, you are kind of splitting hairs. Half of .125 of a second is pretty quick.

Not that .0625 or .125 of a second doesn't matter, but it's not nearly the horrible abyss of lag that people make these kits out to be.

SurfnSun

I hear ya Larry, but if you put an LT1/4 in 6th gear at 30mph its not going to pull either.

Lag is when you're actually in the proper gear and you give it the gas and not much happens...and then BANG youre off.

I was extremely skeptical of the STS systems when I first saw them. I still think a front mount is way better but not practical for C4s. I have yet to drive or ride in an STS car but everything Ive read says they are performing pretty well.

I look forward to seeing what kind of numbers these cars will put out.

5abivt

Please if you can design this system well. Not a no expense spared setup but at least decent enough for those of us with enough of a budget to build a real serious car. I had plans for a no expense spared small block but if this turns out nice i will be building the motor around a high boost setup from you


I've had enough of watching the aftermarket grow for even the pos GTO and not the c4.

5abivt

Now im wanting to know how much hp is even possible for a fairly mild solid roller 383 LT4 fully forged everything running maximum boost possible....

BrianCunningham

If the pipe to the turbo was heat wrapped, it would perform better.

They make a Universal system, $3000, but a kit specifically for the C4 is going to rock.

If you can keep the boost up, may need bigger pipes and turbo, then roughly the same multiplier 44%

rhanselman

I talked with STS tonight and the F-Body LT1 under 12 PSI (posted above) was stroked to 383... They also said a stock bump stick would be best unless you go for a turbo specific grind.

RH