Supertrapp muffler

[perucho]

Anyone here using one? I'm thinking about getting one for my BP swap (with a turbo tube muffler for resonator). Has anyone has had good/bad experience with them?

[fastivaca]

Jay Leno has two on his Festiva

[blkfordsedan]

I had one of the first ones back in the early '90s. I had it on my '79 Fiesta which had a 1.6L OHV with a Pacesetter header and re-jetted progressive Weber carb. My opinion, based on experience, is as follows:

PROS

* looks cool
* supposedly "tunable" back pressure
* supposedly rebuild-able design w/removable core wrapped in fiberglass packing

CONS:

* expensive
* made my car sound like an 8N Ford tractor
* entire internal core rusted out after 1 year (making a rebuild impossible)
* no discernible difference in power between using all the discs and using only 2 discs
* cut my shins on the end discs every time I went to get in the rear hatch.

I think they are now available in Stainless to solve the rust issues. My guess is that the muffler being on the end of the exhaust never gets hot enough to evaporate the moisture inside it. Plus, the cone shape & large open end acts like a big rain gauge. Then the fiberglass absorbs and holds all the moisture inside. As for the science behind the tunable back pressure feature, that can be debated. I personally don't think ANY back pressure in an exhaust is desirable. The farther back in the exhaust system you get, the cooler the exhaust gas becomes and the less important (and less effective) component flow becomes. When you think about it, trying to tune an exhaust system by changing the outlet size of the tailpipe by a small percentage doesn't make sense. Increasing it any larger than the first 99.9% of the system is pointless because it's not a restriction. Would you expect noticeable HP gains by putting a 4" chrome tip on a 2.5" exhaust? Decreasing it smaller than the first 99.9% of the system is only adding a restriction (albeit a minuscule amount)which defeats the whole purpose. In other words, by the time it gets back to the tailpipe outlet, the "fat lady" has already sung. The key is to have flow velocity. When you have too large of an exhaust pipe (or none) you kill the low end torque. That's not from TOO LITTLE back pressure, but from low gas velocity. Many people think that when they put on a smaller factory exhaust and gain low end torque it's due to increased back pressure, when actually it's from increased gas velocity. I think of "flow" as a maximum capacity of a component (port, runner, tube, etc.) when you have an unlimited amount of air available. When you have a finite amount of air (as determined by engine displacement, rpm, cam profile, carb CFM, etc.) you need the port, runner, exhaust pipe, or whatever, to be properly sized for optimum velocity which results in optimum flow. Same reason heads with hogged out ports kill low RPM and only make power at higher RPM levels. They may flow 2X the volume on a flow bench, but can't fill the cylinders efficiently at low RPM on the engine given the air volume required.

Sorry for the lengthy reply. My suggestion is 2" exhaust with a Walker Super Turbo and a resonator tip. It will cost less, be quieter, sound like a Ferrari and last a long time. Just my opinion!

[sc72]

Another Great write up,can you give us some advice on selection of headers-street vs competition equal length tubes etc. Thanks

[perucho]

...When you have too large of an exhaust pipe (or none) you kill the low end torque. That's not from TOO LITTLE back pressure, but from low gas velocity....

Sorry for the lengthy reply. My suggestion is 2" exhaust with a Walker Super Turbo and a resonator tip. It will cost less, be quieter, sound like a Ferrari and last a long time. Just my opinion!

Actually, thanks for the lengthy reply. I completely agree with your assessment of flow, pressure, and velocity. It's been a long time since I've had thermodynamics and fluid mechanics but still remember some I'm planning on using a 2.25" exhaust pipe which may be a bit too much. And the muffler is 4" in outer diameter but the inner diameter is 2.25". The plates are 4" plates but you know how they work.

So you think 2" would work better? And no, it won't sound like a Ferrari no matter what muffler I (or anyone else) use

[blkfordsedan]

Another Great write up,can you give us some advice on selection of headers-street vs competition equal length tubes etc. Thanks

Thanks, but actually, I'm really not the best person to answer your question. There are several others on here that can give you better advice. If your talking headers for a Festiva, take what you can get. Header design is an art all it's own. My basic understanding is that there is an optimum primary tube diameter and length. That length is dependent on the RPM range where exhaust pulse waves are tuned to actually help draw the intake charge in to help fill the cylinder. The diameter is determined by mechanical characteristics of the engine such as displacement, camshaft profile, etc.. There is also a consideration in matching or pairing of cylinders based on firing order. In theory, you want the cylinders that fire 180 degrees (on the distributor) apart from each other paired up. On V8's, these cylinders are on opposite banks of the engine. This requires the headers to cross over the top of the engine or underneath it, which for obvious reasons is impractical for anything but a race car. The next best thing would be to pair up as close as you can get to 180 degrees on each side. This results in the "tri-Y" design or 4-2-1. The 4-into1 header design (most common today) has no secondary tubes but has a similar (but different) design criteria. Most shorty headers, like those popularized by the Mustang crowd, offer little improvement in performance over stock manifolds. I assume this is because their primary tube lengths are just not long enough and their design is compromised by the same fitment restrictions as stock manifolds. Full length headers are the best way to go.
Also, wrap them to keep the heat in the exhaust gas which will aid in gas velocity. Equal length is preferred, since anything you can do to equalize cylinders on an engine builds power. (this goes for piston weights, valve spring pressure, chamber volume, intake & port flow.......everything) The closest you can get an engine to being perfectly symmetrical the better. A well designed set of long tube headers will add torque over the entire RPM range, not just at upper RPM.

Here is a link to a really good article on the subject:

http://www.popularhotrodding.com/tech/0310phr_jack_burns_exhaust_manifold_header_tech/index.html

[ghosthunter242]

i have seen supertraps on lots of things but never a festiva. but, i am new to the field.
but, mine has a harley davidson exaust pipe and it flows free without the pop pop pop of no backpressure. it sounds super quiet with only a whooshing sound. if you are in the portland oregon area, i will be happy to show my exhaust to you. it is funny but it works very well.

[perucho]

Thanks for the offer but I'm in Sacramento, CA. How about some posting some photos or a short video?

[blkfordsedan]

Actually, thanks for the lengthy reply. I completely agree with your assessment of flow, pressure, and velocity. It's been a long time since I've had thermodynamics and fluid mechanics but still remember some I'm planning on using a 2.25" exhaust pipe which may be a bit too much. And the muffler is 4" in outer diameter but the inner diameter is 2.25". The plates are 4" plates but you know how they work.

So you think 2" would work better? And no, it won't sound like a Ferrari no matter what muffler I (or anyone else) use

Check out this link, I think it has a lot of good info:

http://www.magnaflow.com/05news/magazine/05sportc.asp

I don't know that I'm 100% correct on the technicalities, but it makes sense to me.
O.K., so maybe it won't sound like a Ferrari, but my 'Trapp sounded like an 8N tractor and I hated it. The best sound I ever got was with a header, no cat, 1.75" pipe, no muffler and a dual resonator tip. It had that sexy European sports car sound and wasn't that terribly loud.