914-6 Exhaust Questions Options

[PeeGreen 914]

I have seen my share of different exhausts on 6's and am curious as to what you guys feel is the best by way of performance. I see cars that have stingers, Triads, stock, and others.

I guess I am confussed as to why people say you need to bring all pipes together for balance and such. I don't understand this all that well. So do the exhausts that go straight back with out connecting each side not do as well? (IMG:style_emoticons/default/confused24.gif)

[messix]

scavenging!

[charliew]

Most multiple cylinder motors run better when the exhaust pulses help scavange the exhaust. Also a balance tube between the two cylinder banks help gets the drone of the exhaust to a minimum. The high tech cones (super trap) with changeable diffuser disks are probably the most tuneable. As you add the disks the exhaust gets louder. As you remove the disk the backpressure increases and improves low speed torque.

[SirAndy]

I guess I am confussed as to why people say you need to bring all pipes together for balance and such. I don't understand this all that well. So do the exhausts that go straight back with out connecting each side not do as well? (IMG:style_emoticons/default/confused24.gif)

It's less of an issue on a /6.


Backpressure baby!
On a /4, you'll kill your HP if you don't do a 4 in 1 (Or 4 in 2 in 1) ...
(IMG:style_emoticons/default/popcorn[1].gif) Andy

[PeeGreen 914]

So from a performance stand point would what T.C. has on his car be better than JP's triad.

[messix]

back pressure is never good.

there is a science for building exhaust. you have to have the diameter and length of the whole system right to get the best performance.

the key of the whole is to keep the exhaust from choking [backpressure] the engine while still maintaining velocity in the system to help "pull" [scavenge] the exhaust gasses from the cylinders.

[SirAndy]

back pressure is never good.

there is a science for building exhaust. you have to have the diameter and length of the whole system right to get the best performance.

the key of the whole is to keep the exhaust from choking [backpressure] the engine while still maintaining velocity in the system to help "pull" [scavenge] the exhaust gasses from the cylinders.

Not quite true. On a motor with an overlap cam, too much scavenging (Or not enough backpressure) can actually suck out fresh gasoline during the end of the exhaust cycle ...

It's all in the combo!
(IMG:style_emoticons/default/shades.gif) Andy

[messix]

back pressure is never good.

there is a science for building exhaust. you have to have the diameter and length of the whole system right to get the best performance.

the key of the whole is to keep the exhaust from choking [backpressure] the engine while still maintaining velocity in the system to help "pull" [scavenge] the exhaust gasses from the cylinders.

Not quite true. On a motor with an overlap cam, too much scavenging (Or not enough backpressure) can actually suck out fresh gasoline during the end of the exhaust cycle ...

It's all in the combo!
(IMG:style_emoticons/default/shades.gif) Andy

that cam would be a crutch solution to a ineficient exhaust, and that engine would not make it's best power on either side [with good cam and backpressure/ high overlap cam and good exhaust] like you said it's in the combo. so if you can chose your cam and exhaust and have the heads and intake that can breath your best off with no back pressure.

[jt914-6]

Here's my choice: 18" Supertrapps W/18 discs each, European Racing headers Jet Hot coated. 3.0, Cosworth pistons (10:1 compression), "S" cams, 40 Weber carbs. Very quiet for that many discs. No crossover tube.

[dflesburg]

I run headers and megaphones on my 3.2

I also have a sport muffler that I got from b&b - I like that too but will keep the meagphones on till the cops around here give me shit.

So far so good.

[carr914]

I don't have a cross-over tube, even though I have thought of making one. I haven't had a problem with the donut-munchers yet, of course I dump the clutch & the rpms anytime I see one (IMG:style_emoticons/default/laugh.gif)

T.C.

[ArtechnikA]

I guess I am confussed as to why people say you need to bring all pipes together for balance...

You have to look at the firing order.

on a 911 it's 1-6-2-4-3-5 which means exactly the same timing between firing events on each bank. it's basically two 3-cylinder engines 180º out of phase. 911 engines actually run pretty well on only one bank...

a VW Boxer engine, however, has consecutive firing events on adjacent cylinders. so on each bank, it's bang-bang-(nothing)-(nothing).

Scavenging exhausts work best when the pulses -leave- with equal interval.

I read an interview with Jim Busby who ran a crossover on his 911RSR's and he said it was in large part so if he backed into something or got hit in the back and it closed up one side, he could still carry on -- and mentioned twice when that exact thing happened. So there's that, which may be not as good a reason to have them on the street.

Once upon a time, the general rule of thumb was that they were unnecessary below 2,7 and of marginal utility up to 3,0. You get to factor in the weight, cost, and complexity, plus the reliability issue of Porsche's 8mm exhaust studs.

This is one thing Subaru learned - their exhaust studs are 10mm...

[carr914]

Real 914-6GT

[carr914]

One of my old cars. Got these from GT Racing

[PeeGreen 914]

Why do you use that hanger T.C.? Can't you just use the stock hanger?

[IronHillRestorations]

The stock HE's are hard to beat for a 3.0 or smaller engine. Bruce Anerson's much storied 215hp 3.0 with backdated exhaust was a carb'd 3.0 with stock 914-6 he's (Bruce told me that). You might give up a little hp on the top end, but not a lot. It really depends on the application and the rpm range that the engine will be living in. For a street car, a little too small is better than too big.

[J P Stein]

My motor is tuned for mid range grunt. Jon knows what type of balance tube muffler I run......it's not an accident. It may give up some top end vs stingers....big deal. Ya'll listen to your gurus, I'll listen to mine.

[PeeGreen 914]

AX car with no heat. Looking to see what the lightest exhaust is while giving the best performance.I already have a big Triad, JP Stein Triad, and am curious about the megaphones. I am thinkinng of seeing how they do on the dyno but don't really know whn I can. That and I don't have any megaphones (IMG:style_emoticons/default/blink.gif)

[PeeGreen 914]

My motor is tuned for mid range grunt. Jon knows what type of balance tube muffler I run......it's not an accident. It may give up some top end vs stingers....big deal. Ya'll listen to your gurus, I'll listen to mine.

There's really only one guru I will really be listening to as he is the engine man (IMG:style_emoticons/default/beerchug.gif) . However, it may be fun to see what I see.

[carr914]

Why do you use that hanger T.C.? Can't you just use the stock hanger?

I suppose you could use a stock hanger. That would attach at the connection point between the headers & Megas. But the Megas hang out the back quite a bit and this hanger really has a grip on them.

T.C.