Anyone using this exhaust? - Page 2

Zeke · 04:06 PM

Pelican has been selling a version of this since the beginning. Apparently, the Manta system doesn't offer any increase in HP, but the idea is not lost on me.

Everything after the merge is junk, IMHO.

I guess they no longer have it in the 911 version. The catalogue confuses me. and, I don't know why the pic doesn't show. I posted this exhaust many times over the years as I had on once on a car I bought. The system was rotted out and not useable, but sounded awesome. Better than anything I've heard yet. too bad it didn't help the HP.

HarryD · 01-06-2007, 04:35 PM

Quote:

Originally posted by milt
Pelican has been selling a version of this since the beginning. Apparently, the Manta system doesn't offer any increase in HP, but the idea is not lost on me.

Everything after the merge is junk, IMHO.

I guess they no longer have it in the 911 version. The catalogue confuses me. and, I don't know why the pic doesn't show. I posted this exhaust many times over the years as I had on once on a car I bought. The system was rotted out and not useable, but sounded awesome. Better than anything I've heard yet. too bad it didn't help the HP.

Milt,

I agree that they sound great. On the car, they look kinda like this:

boxermania · 01-06-2007, 07:13 PM

The "crossover" allows the exhaust pulses of each bank to draw or "scavenge" the exhaust gases of the cylinder next in the firing order, the end result being the fattening of the mid range torque.

Remember that exhausts gasses are in essence a pulse that creates a sound wave in the exhaust. The wave has speed associated with it and when the valve closes that wave ceases to act on that cylinder but creates a slight vacuum on the next cylinder that the exhaust valve begins to open.

Since the exhaust pulses decrease as they travel down the pipes it is best to place the crossover as close as possible to the cylinder. In the case of headers, this is usually done immediately after the collector and before the muffler(s).

I haven't played with headers in eons, but if I remember correctly the pipe diameter for the crossoever should be .8 of the exhaust diameter. (Need to check what is the current practice) If pipes are the same diameter, a washer with the reduced diameter is welded inside the crossover pipe.

Hope this helps clear some of the crossover issues.

boxermania · 01-06-2007, 07:15 PM

Milt.....many moons ago Sebring used to make that exhaust you depicted. Don't know who makes it now.

randywebb · 01-06-2007, 09:08 PM

good explanation

sithot · 01-06-2007, 09:16 PM

http://www.***************/productpage.aspx?pid=103962&name=manta+exhaust

I had an Ansa "back in the day". Same thing or at least the design is. The sound is quite nice.

Best,

Tom

HarryD · 10:55 PM

Quote:

Originally posted by sithot
http://www.***************/productpage.aspx?pid=103962&name=manta+exhaust

I had an Ansa "back in the day". Same thing or at least the design is. The sound is quite nice.

Best,

Tom

Tom,

Thanks for refreshing my memory, that is the exhaust that is shown on my car.

Peter Bull · Peter Bull's Garage

The crossover pipe has been shown to work very good on a V8 with a 90 degree crank, but does that mean that it will work on a boxer 6? As it is said in the Dr Gas article; the gas pulses collide in the header collector because the firing order of a V8 with a 90 degree crank is uneven. That is not the case with a boxer 6, there the firing order is even and the gas pulses does not collide in the header collector. If the primaries are of even length, that is.

In the eighties there was a Lancia Thema called 8.32 which had the same engine as a Ferrari 328. The engine in the Thema had 215 hp, whereas the engine in the 328 had 270 hp. The big difference between the two engines was that the Thema had a 90 degree crank and the 328 had a flat, or 180 degree crank. A V8 with a flat crank has an even firing order which easily lends itself to tuning by using equal length headers. That is very difficult on a V8 with a 90 degree crank. You need one of those plumbers nightmares that are fitted to the Ford GT40 to achieve the same effect. Or you can aparently use a crossover pipe.

My point is; the gas pulses from a boxer 6 is similar to those from V8 with a flat crank, so the effect of a crossover pipe will not be the same as for a V8 with a 90 degree crank. Does anybody have some dyno results to support that there is a difference in power? If so, how big is it?

/Peter

AES · 01-07-2007, 06:27 AM

I took my own advice and did a search, sure enough
this thread coincidentally from about this time last year has a lot of god info

Bill V's description makes sense to me, it is pretty much what Peter B just posted.

My Cliff notes version,
A flat 6 is not the same as a V8 and has different needs

Zeke · 01-07-2007, 10:58 AM

Peter, my thoughts exactly. I was just showing a version of the idea. I have been seeing flat six race cars the last couple of years use a merged system at the exit rather than the individual megaphones. A very trick open exhaust featured on Dennis Aase's restored early 911 racer now owned by Carl Thompson has a 3-2-1 system. No muffler whatsoever. Awesome sound. Like a Kirker on a six. Can't tell you what it does for performance, but guys like Carl don't waste money on bling.

Apparently there is something to this. RacerChris on the 914 bbs has been building 4-2-1 systems for 4 years and has proven claims of gain. There is some science as to the secondary pulse. All performance exhaust works in a narrow band of optimum benefit is what I'm told.

911pcars · 01-07-2007, 11:15 AM

Soon after completing design and fabrication of this exhaust system, Hans realized he joined both sides. He then admitted himself to a rest home in the Bavarian mountains.

Sherwood

randywebb · 01-07-2007, 11:56 AM

"All performance exhaust works in a narrow band of optimum benefit... "

Yup - that's cuz race motors are tuned for a narrow band of hp production rather than lower hp over a broader band - the latter is more streetable but cannot give as much peak power

the whole thing is based on the cams and flow rate of the air pump under hood (aka motor)

AES · 01-07-2007, 12:37 PM

Bill called this setup, 3 to 2 to 1 a "Tri-Y"
Pic from Bill"s post

safe · safe's Garage

Quote:

Originally posted by 911pcars
Soon after completing design and fabrication of this exhaust system, Hans realized he joined both sides. He then admitted himself to a rest home in the Bavarian mountains.

Sherwood

That engine looks strange, what is it?

boba · 01-07-2007, 12:55 PM

Here is a 3 into 2 into 1 during trial assembly.

Steve@Rennsport · 01:06 PM

Al Morales offered a good explanation of what a crossover, aka balance tube does.

From 28 yrs of dynoing 911 race & street motors, these make a big difference on these cars, without a doubt. Further, placement of these pipes is critical as are primary & secondary (post collector) lengths.

Crossovers help mild street engines as well as highly-strung race engines build more bottom & mid-range torque and make a huge difference in the AFR curves.

These can be done using a single, dual-inlet muffler or by adding a balance tube as in the picture you see if Sherwood's post off our website. That particular system used a pair of special Flowmasters so the extra plumbing was required.

Now, we use either a Flowmaster Series 80 or similar Magnaflow for race engines and a factory style muffler (Monty or Dansk) for street cars. Both incorporate the balance tube in the muffler itself for effect.

Adding a crossover is worth anywhere from 10 to 25 lbs-ft depending on the engine and a MUCH smoother AFR's. The latter is very important if you are carbureted or MFI'ed.

Cox Motorsports as well as others make that 3-2-1 system and it looks very good. We have not tested one on our engine dyno so I cannot offer anything in the way of comparisons. Due to local and regional noise regulations, we must conform to a 96 db limit and that precludes any open exhausts.

Peter Bull · Peter Bull's Garage

Quote:

Originally posted by safe
That engine looks strange, what is it?

A 908 engine?

After some leafing through a book by Smith and Morrison called "Scientific design of exhaust and intake sysems" it seems that the crossover as used by Steve @ Rennsport works in a little different way than the crossover pipe Dr Gas describes. The latter lets the gas that collides in the collector on one side expand into the other side, whereas the former works like a resonator. If I understood it right, that is. If it works as a resonator its effect would depend on the length of the crossover tube.

Have you tried with different lengths, Steve? And why does it affect the AFR? I thought that was governed by the parts on the intake side

/Peter

AES · 01-07-2007, 01:41 PM

Quote:

From 28 yrs of dynoing 911 race & street motors, these make a big difference on these cars, without a doubt. Further, placement of these pipes is critical as are primary & secondary (post collector) lengths.

So you must have some back to back dyno charts?

911pcars · 01-07-2007, 04:45 PM

Quote:

Originally posted by safe
That engine looks strange, what is it?

Wayne can answer with more detail. It was one of the V. Polak engines auctioned last year. I believe it was an experimental flat 8.

Sherwood

dd74 · 01-07-2007, 05:08 PM

Crossover pipe - Hmmm...when I had Ben's Stingers on my car (little pipes that come right off the exchangers), I had no crossover pipe, and noticed no appreciable lack of torque.

Now I have an M&K two/one muffler, and it seems torque is about the same as when I had the Stingers. This, of course, is non-dynoed information, and just an observation. YMMV