jshuberg

I've got an '84 US 928S with Euro cams. Possible future upgrades would be Euro heads and/or supercharger. Currently the exhaust is stock, and is likely choking the full potential of the cams.

I'm thinking of MSDS Headers to a Y pipe with 3" outlet to a Random Technology 141-30000 CAT. From there a Magnaflow muffler and/or resonator. I have no idea which combo would sound/perform best, so please chime in with your opinions. Nothing is set in stone at this point, so any suggestions are welcomed.

Thanks much!!

Ducman82

that sounds good to me. i have MSDS headers, 3" stainless single after Y.. to a magna flow 14" out back... sounds great

Richards 928

I have exhaust envy. My exhaust plan is very similar. Your proposed system will sound great. I don't think there is downside.

Were you planning a pre/post dyno test to confirm power levels?

Richard

jshuberg

Glad to hear! Do you have the model# of the muffler you used, and where was it installed, back by the cat or at the tips? Would you recommend a resonator with this setup?

Absolutely!! I have dyno results from last week after the cams went in, and I'll have another run done after the new exhaust is in. It was suggested to have a dyno run with the new exhaust and the stock manifolds, followed by another after the headers are installed, but I think someone else is going to have to be that guinea pig. I'm just planning on doing it all at once and then see what that does for me.

Thanks much!

Dave928S

That'll liven it up!!

What you have planned sounds great, and I think you'll see a nice increase.

ptuomov

If you're making your own exhaust, you should buy a copy of PipeMax software. It's cheap, and synthesizes all the conventional wisdom you can get from internet forums.

According to that program, a hot-rodded, normally aspirated 928 engine is going to like something like a 1.5"-1.65" ID primary pipes with a total length of about 28". If you put in a step in the primary, it's going to want that step to a larger pipe at the mid point at about 14". The collector will terminate to a x-pipe or y-pipe a at about 18" from the pipe ends. From the middle of the x or y, you might want to try running another 18" to a terminator box or a big catalytic converter?

In terms of sound, I have an idea that I've wanted to test (but I am lazy and/or incompetent fabricator.) I want to run a single pipe in the center section, then divorce the flow to two mufflers, and then merge the unequal length pipes again to a rear muffler. The theory here is that there will not be long or equal length sections in the exhaust that will prevent drone. In particular, the unequal length pipes to the rear muffler should phase shift the pulses slightly and kill off any unwanted peaks. Don't know if it'll work, since I haven't tried it for the above documented reasons.

Here are some of the pieces I already have, it's 4" to dual 3" which is too big for you:

The Forgotten On

Stick with a 3 inch pipe and you can do what ever you want after that. I have a 3 inch with a mid muffler and a tip where the rear muffler was.

It sounds really low and burbly and more like a muscle car than a 928 but is quiet while cruising.

That is one thing you should look out for is to have a good sound but not too much noise or else you will get tired of it on longer drives.

FBIII

Here is what I am putting together for my 81 Euro S. So far I have: MSDS headers, two 3 inch 100 cell cats into a flowmaster Y pipe. The Y pipe is two 3 inch pipes in and a 3 1/2 pipe out. I'm leaning torwards a muffler after the y and a second at the rear of the car. I don't want it too loud. Any suggestions for mufflers would be appreciated.

ptuomov

Here's a post on how important it is to get the pipe length _after_ the headers right. http://speedtalk.com/forum/viewtopic.php?t=7870

The so called collector length is measured from the primary pipe ends. The end of the distance is where the wave terminates, which means any large expansion of cross sectional area. Pipe in the open air, a cross-over, chamber muffler, or a terminator/resonator box will all act as an end to the collector. Glass pack or other non-open-chamber muffler doesn't end the collector, instead the wave think it just a pipe. All mufflers are not created equal.

Here's a test of open headers that have just a stub vs. a longer collector pipe added to the end of the headers. The data are from Car Craft which is one of the more sensible hot-rodding magazines:





All this exhaust stuff really starts making a difference when the cams have significant overlap and compression is high. Since the original poster has "euro" cams, I think the exhaust might have some ponies hidden in it.

Now, the caveat: I don't know what I am talking about. Just thinking about it out loud.

FBIII

I read that a way to determine where to place the crossover pipe, x or Y pipe is to paint the exhaust system below/beyond the collectors and where the paint burns off is where the pipe should be placed.

hacker-pschorr

Here is what a stock US 79 sounds like with MSDS headers, y-pipe and straight through (no muffler) 3" exhaust:

123quattro

I have MSDS headers merged into a single 3" running to a Magnaflow 14" muffler that sits beside the transmission and no cat. This one: http://www.magnaflow.com/02product/s...=main&id=11523

I have zero drone. It sounds really nice to me, but it's loud. Link to video of 272whp dyno pull.

https://www.flickr.com/photos/871304...57618821493278

jshuberg

If I'm reading this correctly, to maximize low end torque the total length of the collectors (header and extensions) should be at least 24" long before dumping into the Y. I believe that the collector outlet for the MSDS headers is 3", so should the collector extensions also then be 3" or should they restrict down to 2.5" or 2.75"?

Any recommendation how far down from the Y pipe the cat should be located? Do I need another unrestricted length of pipe for the turbulence from the Y to settle before entering the cat, or is the location of the cat not a factor?

123quattro

Put that catalyst as close to the engine as possible. Like directly after the Y pipe. MSDS headers have 3" collectors. Do yourself a favor and cut them off and weld V-bands on. I wish I would have done that.

hacker-pschorr

+1

I have a set sitting on the floor next to me and I did just that. The flange on the stock MSDS headers is a bit thin, I've seen more than a few warp and leak.

I should really sell these..... I doubt I'll ever use them.