I just test fit an old bus muffler (from a '72-'74) on my Porsche 2.0L motor that's been transplanted into my type-3. The fit is fantastic and gives a nice factory look. The problem is that i an planning to run MS EFI with a wide band O2 sensor and the only place I could get even flow for the sensor would be after the muffler at the base of the tail pipe. Do you all think I will get good readings in that location?? Here's a photo of a mock-up muffler identicle to the one I would use on the motor:
I could just cut and modify a Thunderbird style 4into1 to fit and put a bung just after the collector, but if I can run a new muffler like this and still get the readings necessary for proper operation of the MS EFI, I would rather just do that. What say you??
NO. That location during deceleration and some small opening part throttle sucks tons of air back at that point. You can get wildly innacurate readings at that joint.
The only way to fix that would be to install a small chamber with an inverted V shaped anti reversion baffle in it.
That being said....there is a better location for it. You can drill a hole dead center in the side toward the front of the car...close to the rear hanger... though that will be scorching hot and a b*tch to reach....or you can drill a hole and install a bung on the back side...dead center on the back side center weld line. In your photo...this would be right on teh case centerline and tilted down toward the street.
Question.....Have you ever seen the inside of one of these? I mean do you know the exhaust flow pattern? Its totally differnt from what you might think just glancing at it. I have three of them...a leistritz, an Ernst and a Dansk sliced open. They are all basically identical inside save for some variances in technical dimensions.
I love and hate these mufflers. Love them because VW did an admirable job of putting something together in a very small space. Nice package.
Hate them because their volume is too small and they run hot. Very very hot. The only brand I would use is Ernst. Built far and away better and cleaner than all the others....and about 15% bigger in internal volume with larger perforations, and slightly larger tubing inside for better flow.
Simply put...the exhaust from the 1 and 2 side are joined together in a single pipe that runs end to end. This pipe has perforations along its length and an open end. It spreads exhaust evenly through the muffler body in a pattern wide pattern. the 3 and 4 side does the same and runs in the opposite direction towards the right. they are stacked one above the other with slight spacing. Toward the lower back....you have the center tube/pipe....that is attached to the exhaust pipe. It runs full length and may or may not be open at the opposite end...depends on the make and year.
These three tubes are essentially stacked in a pyramid if you take a slice in cross section with the central exit ube of larger bore with larger perforations taking up the point farthest to the rear at the bottom.
So basically the two 2-into-1 pipes spread gasses out evenly where they make their way into the perforated center pipe and exit.
Because 1 and 2 and 3 and 4 are hooked together like a pair of old dual buggy exhausts....this muffler will NEVER "MAKE" power for you like a header. But if you could get the flow clean enough and keep back pressure from happening....it can keep you from at least losing HP on a stockish motor.
If you wanted to spli one of these open and make a design change that would help.....you would stack two center tubes. One exits to the right, one to the left. Perforate them slightly larger than what you see on stock....and bisect the entire muffler with a sheet of welded metal. In this way...the 1 and 2 side pipe will be the same as the 3 and 4 side which exits to the left...and has gasses at least moving toward the left exit tail pipe. Putting a seperated right side exit center pipe with aright exit f or 1 and 2...will greatly improve this type of muffler. That...and the fact that the whole muffler would need to come up about 40% in internal volume.
Bear in mind....even the Ernst model being about 15% larger....is only adequate for a hot 1.7L....with a lot of injection tuning and a better breathing cam. Put these on anything of higher displacement.....and you risk running hot.
From this description and the way thegasses mix inside...you can see why putting a bung dead center in the back will be good.
There are at least four major brands out there and they are not all equal. Ray
Ray, you are a master of linguistic visualization!! I definitely don't want to risk running hot with this motor since it's still running the stock cam which aren't known for shedding heat from the motor. While it could be made to work, I'll just mod the new Thunderbird style 4into1 I have and make that fit. I knew the performance wouldn't be as good, but man,. . .it fit sooooo nice and looked soooo factory!! Performance IS what I'm after so I know what I have to do. . . Thanks for all the info!!
I hear ya. It is really a neat package...and not a hideous design. In my opinion...its really just undersized in internal volume and in perforation size.
this is why I eventually cut a few open after finding out that some were so much better than others. In order....these are the best to worst by brand.
Ernst
Leistritz and starla or starleiter
Wagner and VW branded OEM
Dansk.
If you used an air chisle or a cutter to open the seam on the muffler...then redrilled to larger..say...double...all of the perforations....it would be better.
A twin exit model woul be best
Even better....take a piece of say.....8" diameter stainless tube. have six pipes inside. Each exhaust outlet has a seperate tube stacked on top of each outher. 3a nd 4 to the right and 1 and 2 to the left. Decent size perforations spraying toward the center and rear of car...open ends.....and a larger diameter pair of center tubes with an exit right and left....with larger perfs. You could build a factory style muffler...decently quiet too....that was about 50% better than stock. Ray
Yeah I had the same thought about spark arrestors. The issue on the type 3...is the same as my 412. The stock muffler "just" fits. Add anything between muffler and tailpipe and it no longer fits....and is really a pain to do anything with. Ray
Jadewombat: Adding a spark arrestor is a really good idea!! I can get a 2" clamp-on type that could easily be welded to the end of the tail pipe. I would really rather prefer to use the stock muffler due to simplicity, perfect fit and looks (it just looks like it belongs on the car).
I don't want to have to completely reinvent the wheel to get this on the road, but if I have to, I will. The Thunderbird system hits the rear apron by about 3/4". To use it w/o cutting the apron I would have to shorten the 3/4 tubes w/o making the bends tighter. Doable, but call my lazy. . .
See if you can find one of the Ernst brand mufflers. The best out there by far. Heavier, thicker, better welds and larger and better flow in all respects. Ray
I definitely don't want to risk running hot with this motor since it's still running the stock cam which aren't known for shedding heat from the motor. While it could be made to work, I'll just mod the new Thunderbird style 4into1 I have and make that fit. I knew the performance wouldn't be as good, but man,. . .it fit sooooo nice and looked soooo factory!! Performance IS what I'm after so I know what I have to do. . . Thanks for all the info!!
The Thunderbird system hits the rear apron by about 3/4". To use it w/o cutting the apron I would have to shorten the 3/4 tubes w/o making the bends tighter. Doable, but call my lazy. . .