Twin Turbo L98 C4 - looking for advice
03-16-2016, 09:23 AM
#1
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Twin Turbo L98 C4 - looking for advice
I've been thinking about this for a long time and I think it could finally be my next project. I'm looking for a semi-low budget daily-driven capable twin turbo L98 setup for a C4. Seeing as I still don't even have the base car, I'm hoping to avoid unnecessery mistakes.
Plan would be to first convert TPI to Megasquirt3 with EDIS8 and get the car running like that N/A. Then I would fabricate headers and pipework and fit compact twin turbos to run ~5-6 PSI with all stock internals. The stock bottom end should be able to take 5 PSI properly tuned and intercooled, right?
Even in the long run I'm not after big hp, the idea would be to maximise driveability and mid-range torque. Stock intake and cam should work so long as I don't intend on getting power past 5k rpm? Stronger internals could be considered later on.
I guess I have two big questions to start with. The stock bottom end; I see many cars with supercharged L98s and they seem to hold up at least with low pressure setups. Is it doable to go for Callaway numbers (350-400 flywheel hp) without forged pistons? And how far do the stock crank and rods take you?
The second question is the ancillaries/serp belt setup. I would like to fit the turbos up front, next to the front corners of the rocker covers, but there's the alternator and A/C compressor in the way. Any way these could both be relocated on a C4 to allow room for the turbos? I've also seen someone fitting turbos right alongside the heads, headers pointing straight up. I can see this is doable but how do you then deal with the A/C pipework which sits right where your right side turbo would be?
Now before anyone starts selling me a C5 or an LS swap, a turbo C4 is my dream and I'm a turbo nut anyway so that's what I want to do.
BTW, the car has to be an '85-'86 because of local legislation considering performance modifications. And even though the Doug Nash has a bad rep I still want a manual. At least it has the stronger diff and a Tremec swap is easier...
Plan would be to first convert TPI to Megasquirt3 with EDIS8 and get the car running like that N/A. Then I would fabricate headers and pipework and fit compact twin turbos to run ~5-6 PSI with all stock internals. The stock bottom end should be able to take 5 PSI properly tuned and intercooled, right?
Even in the long run I'm not after big hp, the idea would be to maximise driveability and mid-range torque. Stock intake and cam should work so long as I don't intend on getting power past 5k rpm? Stronger internals could be considered later on.
I guess I have two big questions to start with. The stock bottom end; I see many cars with supercharged L98s and they seem to hold up at least with low pressure setups. Is it doable to go for Callaway numbers (350-400 flywheel hp) without forged pistons? And how far do the stock crank and rods take you?
The second question is the ancillaries/serp belt setup. I would like to fit the turbos up front, next to the front corners of the rocker covers, but there's the alternator and A/C compressor in the way. Any way these could both be relocated on a C4 to allow room for the turbos? I've also seen someone fitting turbos right alongside the heads, headers pointing straight up. I can see this is doable but how do you then deal with the A/C pipework which sits right where your right side turbo would be?
Now before anyone starts selling me a C5 or an LS swap, a turbo C4 is my dream and I'm a turbo nut anyway so that's what I want to do.
BTW, the car has to be an '85-'86 because of local legislation considering performance modifications. And even though the Doug Nash has a bad rep I still want a manual. At least it has the stronger diff and a Tremec swap is easier...
Last edited by TurboJ81; 03-16-2016 at 12:17 PM.
03-28-2016, 07:34 PM
#2
Melting Slicks
I chose a single turbo for the reasons you mentioned. Mostly wanting to keep my AC. I relocated the alternator and PS pump. I'm still having belt slip issues. If you find a good way to relocate, please let me know. There are some really small AC compressors out now. If you want to see an exceptionally well done setup, look
.