I got the Spintech 331SC muffler installed with 2.5" in and dual 2" out. They had to leave the springs out around the muffler (no room to manuever around the inlet and outlet pipes). Instead, they added two addition hangers. This is the only difference from stock.

The sounds is somewhat louder than stock, but it's just a low burble in the back. There is no interior resonance anywhere. There is a peak resonance at 2500 RPM, but it's nothing really. You can still hear the wind noise while cruising along.

My boost dropped a bit (good). I will measure the backpressure tonight.

This was for a 3800 SC engine.

I'm happy.

how do you measure back pressure?

0-10 PSI gauge screwed in place of the O2 sensor. Take the car for a drive. Check it at cruise throttle and WOT.

On cars with air injection tubes, you can connect the gauge there.

Using the stock Fiero system and the 3800SC, I could peg the gauge. Bad, real bad.

>Using the stock Fiero system and the 3800SC, I could peg the gauge. Bad, real bad.

Hmmm. Yes, not good.
On the Ford turbo that I have, the wastegate opening pressure is fixed by the length of the rod that controls it. You can easily finesse that by using a threaded rod to adjust the wastegate opening pressure.

To be sure, any SC is fundementally different, but I thought that the peak boost was also controlled somehow as well.

I will incorporate this info into my project, as well.

In this case, less boost means more flow through the system. You're getting the same amount of air (if not more) with less restriction. That's good if you have a supercharger or a turbo.

>In this case, less boost means more flow through the system. You're getting the same amount of air (if not more) with less restriction. That's good if you have a supercharger or a turbo.

I understand, I just thought that the PCM would restrict peak overpressure via ignition or fuel feed in this engine.

The exhaust system does seem like an area for definate improvement here.

I suppose someone has already worked out some optimum header/collector lengths on a Dyno yet?

Now, where's that TIG welder ...

On Buick SC's, boost is limited by the pulley not the ECM.

I believe the 3800SC has an internal wastegate to control boost.

The bypass is there, but except during decel, idle, cruise and reverse, it's hard to get it to bypass the blower at WOT. Other stuff kicks in first.

>On Buick SC's, boost is limited by the pulley not the ECM.

I assume that would be the same for any non Roots type blower? Then in this blower the pulley would be the limiting factor... hmmm.

(Don't mind my going into 'student mode.')

Again; then the new muffler contributed positively, as in safety factors vs. performance??

And again; any info out there as to header & collector length for the 3800SC??
-g

Check the Thrasher site. The Buick Power Book has some detail too on headers. The fit is tight on a sideways motor.

Yes, the performance was very positive. The engine would just fall down in power about about 2500. I wanted to keep a stock routing and dual outlets.

Checked out the Thrasher site. What headers!

Shame they aren't for a Fiero ...

I did email a query re. dimensions, but I wouldn't blame them for not bothering to reply to someone they can't sell them to.

Interesting chip mods & shift kit for my trans, though.

Has anyone used the Thrasher/TEP components?

Tom from Thrasher had a look see at my car and didn't think there was any way their headers would fit.

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SC 3800

>didn't think there was any way their headers would fit.

Oh, I agree! but since they did all the dyno R&D on those headers, I wanted to get pipe & collector lengths & diameters.

I'm thinking of taking that data & then see if I can TIG weld up a set to fit.

There's a couple of shops down here that could use that set to measure & mandrel bend
up a set, & then I could go from there.

Well, maybe ...