Steve Weiner-Rennsport Systems

Randy:

First my apologies,...I reread this thread and accidently overlooked your question about dyno testing 3.6's with SSI's and GHL/B&B exhausts.

We tested two 3.6's with SSI's and a Monty single outlet sport muffler: one was a 964 engine and one came from a non-Varioram 993 (95 MY). Both engines gave up 20-25 HP above 5200 RPM, compared to a GHL heat exchanger/muffler system.

The 1.5" primaries truly penalize anything over 3.4 litres. These things need 1 5/8" to 1 3/4", depending on displacement and RPM range.

mjmoran

Thanks Steve,


Kind of funny since they say they take the "res" out of resonance. I have heard that I have the later type of header. It has a wider set-up than the SSIs. If I try to match a stock exhaust off a 74 Carerra to it, the exhaust inlets are about 4" too close. Im guessing they could go with a larger muffler because of this. Maybe I could have a Monty made to fit?! I will keep everyone posted. Check post: "GHLs on my Carrera"

Carrera51

My dad has the full B&B setup on his 964. In 5 years, the muffler has not cracked once. The resonance is a nuisance because of the dual outlets. The mechanic fabricated a device to cap off the left side outlet for when he drives it on the street. Bye bye resonance. It takes less than five minutes to remove it when he takes the car to a DE.

mjmoran

I had that same thought of capping off the muffler -- a-la Fabspeed. Maybe Ill try that.

r911

Thanks Steve. Those engines were stock? That's a lot.


re caps -- It might be fun to rig up a cutout actuated by the throttel lever in the cabin.

JackOlsen

Regarding the B&B mufflers, you can also reduce down the outlets to eliminate the skull-grinding resonance. I run both outlets all the time, but don't have any resonance at all, since this mod. The motor (a 1993 964 with headers and a chip) also dyno'd at 286 crank hp, so I don't think the mod is costing me any ponies.



Now, I still maintain that the construction of the thing is terrible. We welded it back up, but it's clear that it's going to start to split apart again.

Steve W

Exhaust resonance comes from the mufflers, not from the headers or heat exchangers. I spent a couple of days dialing in a 3.4 conversion for TRE which was built with larger diameter GHL heat exchangers and a modified Dansk muffler. It was internally modified with an extra tailpipe added to the right side and a removeable cap. Absolutely no resonance/droning, or wierd noises in any rpm range or load with either the right side tailpipe capped or not. With it capped, it sounded more like a stock Carrera than a set of SSIs with a factory banana muffler. With the second outlet uncapped, it was just a bit louder, but not obnoxiously so, and really let the motor scream above 5000 rpm.

mjmoran

Just talked to Brian at GHL. He has made a reducing insert (resonator) that sounds like it may go into the tip itself to reduce the droning affect. He is sending this along with a new single out muffler and a muffler cap for my dual to make the dual into a single. My guess is that the droneing is from the harmonic distortion from the two outlet pipes being different lenths. Maybe a reducer in the longer of the two will fix it...kind of like the narrows brige accident??? I sure like the looks of the dual, but if the sound is going to persist, its goin bye bye. Those pipes on your RSR Jack look great!

Chris M.

How about with no muffler? Will the SSIs still provide the power people claim on my 82 Euro SC? I still run the cat but eventually (when I start trailering) won't.

Steve Weiner-Rennsport Systems

If you run SSI's without a muffler (or even individual ones) you can watch your low & mid-range performance disappear,......

With SC cams and the CIS intake, you don't have any upper-end performance either and so its a big net loss.

These engines are particular about exhaust systems and its easy to make regressive changes,...

Chris M.

Thanks for the info Steve. With a muffler can I expect the same gains as on the USA engines? Right now the car has the cat installed because the PO lived in CA. Will running the cat bypass effect anything as long as I still use a muffler?

LaughaC

Best, and most useful, thread I've read in a while.

Rennlisters are great for anecdotal opinions. Add to that the clear, concise info from Steve and Peter and we have action steps to achieve our goals without wasting resources.

JV911

SSI's and Monty - see sig

Naitove

SSI and M&K Gen 4. 1 or 2 out, your choice.

Chris M.

Could the same be said for running stock heat exchangers with no muffler or cat? Reduced performance?