supercoupe exhaust backpressure q's- how do I fix it? - TCCoA Forums
 
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post #1 of 8 (permalink) Old 06-17-2006, 05:35 AM Thread Starter
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supercoupe exhaust backpressure q's- how do I fix it?

Hi there, I just bought a 1990 Supercoupe 5-speed, kind of high mileage.

From what I understand, it appears that the stock SuperCoupe exhaust is extremely restrictive and the 15psi of backpressure it creates can cause headgasket failure.
My SC has 187 or 189k, I can't remember which, miles on it and it runs very smoothly, and feels quite strong. I've been babying it, as did the previous owner and have been shifting at 3k in an effort to make sure the headgaskets don't fail.

Since I am on a limited budget and since I have to go to Pick-Your-Part anyways, I want to know if I can't put the V8's duals on as a means by which to reduce backpressure while still remaining smog legal.

One, are the v8's duals usable cat-back on a 3.8SC?
Two, if the V8's duals are unusable, what is another cost-effective solution to the backpressure problem?
Three, are there any other junkyardable inexpensive items that can be added to extend engine life and promote reliability/durability?

Thanks very much!
The Ghost

96 Laser Red 4.6L - Custom
Custom Nascar-Inspired Bodykit - 55* Rear Spoiler - J-modded Trans - 80mm MAF - One-Off Diablosport Chipmaster Revolution Chip/Tune W/Toggle - ScanGaugeII Diagnostics & Data Readout - PBR Brakes - Drilled/Slotted Rotors - SC Wheels & Springs - Falken Tires - KYB GR-1 Shocks/Struts - FSTB - RSTB - RTLB - LECB - 60/40 Split Rear - SC Seats - SC Vac/Boost Gauge
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post #2 of 8 (permalink) Old 06-17-2006, 09:54 AM
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I can't really speak for the SC's, as I've never had one (not for lack of wanting to. You're lucky!) Anyway I don't think the V8's duals are any less restrictive than the SC's. I do know that a couple of company's make cat-back kits for the T-bird. Or you can go with a true dual system that has gained popularity here. It utilizes a dual in/dual out Magnaflow muffler. For pics you can go here.

http://www.tccoa.com/gallery/exhaust/index.html

Here are some shots of my Dual set up, it's a fairly common around here:

http://members.tccoa.com/traveler/exhaust.html

If you haven't already, you might go to www.sccoa.com and ask there (after doing a search). Those guys are as knowledgeable about the SC's as the folks here are about the T-bird in general!

And welcome to the club.


1997 Thunderbird Sport
Low Miles
Wifes Car
destined to remain stock

1997 T-Bird GT 4.6
80 MM Mustang GT MAF - P&P'd Mustang GT TB and Intake Plenum - PI Intake manifold - PI Heads
Mark VIII Torque Converter - J-Modded 4R70W transmission - Mark VIII Aluminum Driveshaft - 3.73 gears
PBR Brake Calipers - Eibach Springs - KYB Shocks
'89 SuperCoupe front and rear sway bars
SCT Chip programmed by Lonnie Doll
255/50/16 Falken Ziex ZE-512's
True Dual exhaust with Magnaflow DI/DO muffler
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post #3 of 8 (permalink) Old 06-17-2006, 10:02 AM
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There is a resonator that causes a lot of backpressure it looks kinda like a muffeler and if you remove it or replace it that should help a lot. Ford put this there so you would loose 10 or so hp so the SC wouldn't be faster tnan the mustang. One thing to note the sound might be different.

1996 sport 4.6 130k and still strong.
1991 SC 3.8 project and toy.
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post #4 of 8 (permalink) Old 06-17-2006, 10:10 AM
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Yep, the Resonator is (was ) right where my Magnaflow muffler is now, except on the V8's it isn't a resonator, its a third Catalytic Converter.


1997 Thunderbird Sport
Low Miles
Wifes Car
destined to remain stock

1997 T-Bird GT 4.6
80 MM Mustang GT MAF - P&P'd Mustang GT TB and Intake Plenum - PI Intake manifold - PI Heads
Mark VIII Torque Converter - J-Modded 4R70W transmission - Mark VIII Aluminum Driveshaft - 3.73 gears
PBR Brake Calipers - Eibach Springs - KYB Shocks
'89 SuperCoupe front and rear sway bars
SCT Chip programmed by Lonnie Doll
255/50/16 Falken Ziex ZE-512's
True Dual exhaust with Magnaflow DI/DO muffler
<<< SOLD >>>
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post #5 of 8 (permalink) Old 06-17-2006, 03:02 PM
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First of all you have a 90, so you have the old style gas tank. You will want to switch over to the 92+ tank if you plan on running any sort of true duals on it.

I highly doubt that a V8 exhaust would just bolt right up to an SC and fact is, they don't flow much better. All MN12's got the crappy bends and small piping. Stock exhausts on any MN12 is one big bottleneck....lol.

Here is an article I suggest reading through:

http://www.mn12performance.com/mn12-...st/exhaust.htm

I'd recommend going with some high flow cats and running some good piping from there back however you want it.

Here is a popular setup for the SC's:
http://www.supercoupeperformance.com...spx?PartID=145

It is pricey but, you could always print out a picture and take it to a local shop and have them mock something up for you.

Just some thoughts....


Sold - 1997 Ford Thunderbird 4.6 Sport - Full bolt on, PI stuff, gears, converter, exhaust, full suspension & many other things.

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post #6 of 8 (permalink) Old 06-17-2006, 08:19 PM Thread Starter
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I was thinking more along the lines of $100 or LESS to fix it.

96 Laser Red 4.6L - Custom
Custom Nascar-Inspired Bodykit - 55* Rear Spoiler - J-modded Trans - 80mm MAF - One-Off Diablosport Chipmaster Revolution Chip/Tune W/Toggle - ScanGaugeII Diagnostics & Data Readout - PBR Brakes - Drilled/Slotted Rotors - SC Wheels & Springs - Falken Tires - KYB GR-1 Shocks/Struts - FSTB - RSTB - RTLB - LECB - 60/40 Split Rear - SC Seats - SC Vac/Boost Gauge
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post #7 of 8 (permalink) Old 06-17-2006, 09:42 PM
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try removing that resonator it will also increase the life on your headgaskets keep it so that you can put it back though you might not like the sound but you will gain 10 or so hp from that. should cost very little and lower backpressure by a few pounds.

1996 sport 4.6 130k and still strong.
1991 SC 3.8 project and toy.
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post #8 of 8 (permalink) Old 06-25-2006, 04:18 AM Thread Starter
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gonna have the resonator yanked I think.

96 Laser Red 4.6L - Custom
Custom Nascar-Inspired Bodykit - 55* Rear Spoiler - J-modded Trans - 80mm MAF - One-Off Diablosport Chipmaster Revolution Chip/Tune W/Toggle - ScanGaugeII Diagnostics & Data Readout - PBR Brakes - Drilled/Slotted Rotors - SC Wheels & Springs - Falken Tires - KYB GR-1 Shocks/Struts - FSTB - RSTB - RTLB - LECB - 60/40 Split Rear - SC Seats - SC Vac/Boost Gauge
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