HerrSavage

Trying to figure a way to get the exhaust out the side of my DM-1, without having to cut half the left side of the body off.. I have a silicone exhaust deflector thing, that aesthetically anyway would do the trick nicely. Also, because it's an onroad car, I assume it's more important to deflect the oily exhaust away from the rear left wheel??..

Do they inhibit performance?

Argess

Well....first off....I don't know. But I did read a test once where the exhaust was restricted in steps, and there was no loss in perfomance until it was almost completely shut off. This was after the exhaust, not before, so the tuned pipe effect was basically unchanged. I could see a minor tuning adjustment being required, but unless you are doing timed drag racing, everything indicates no change.

They must restrict to some extent, as people have seen improvements with half-tank-lean issues by adding an extension. Builds the pipe pressure a bit and makes the gravity effect less significant. Since the pressure is changing, and air/exhaust is flowing more from the pipe to the tank, more energy is being used, and that takes away from the crankshaft power, but apparently it is insignificant.

......remember I said I don't know?

Seems easy enough to find out. Do some testing with the body off, with and without the extension. If you can't notice it, is it worth worrying about?

Anyway....hopefully someone who knows should chime in with the answer.

HerrSavage

Really just a question of to drill a hole in the bod now or not.. Prob won't be able to test til spring..

PrjctStrtFrce

My Feedback: (10)

I have them on my Savages and there is no difference that I have seen....BUT, when I first put one on my X4.6 that I ran before, it threw the tune off a little, so I had to adjust it, but performance is still there.

proanti1

My Feedback: (2)

Exhaust deflectors move your power band way back since they increase your stinger length. I have always cut a little notch from the body, just for the stinger.

Argess

I wonder if it increased the exhaust pressure, and therefore the fuel tank pressure and made the engine run a tad rich. Do you remember if you leaned it to restore the tune?

That's interesting. I wouldn't have thought the stinger had anything to do with the tuned part of the exhaust, as the tuning theory usually only deals with the convergent cone, divrgent cone, and header length. Well, that may not be true, but I don't remember anything written about stinger length....LOL.

So when you say "way back" how significant a change do you mean? Can you throw out some hypothetical numbers? Nothing exact, .....a best guess is fine....just something to help define the change a little bit.

2-stroke tuned exhaust......darned interesting subject at times

Anthoop

A longer stinger will increase back pressure, increased back pressure will increase the temperature in the pipe (and the engine). The increased temperature will increase wave speed which will effectively shorten the tuned length of the pipe.
Of course it is a little more in-depth than that but that is the basics, there is plenty of information on the web about tuned pipe theory and calculations etc. some of it is free and some of it is not.

proanti1

My Feedback: (2)

Depends on how matched your pipe is to your engine. your power band would kick in later, then drop off later. Probably less than 500rpm difference. Doing ANYTHING that requires a slight tune will effect your power band, and deflectors do require a little tune to compensate for the back pressure.

If this is a question about a stock pipe, and a stock motor... the power band is probably already non-existent, so a deflector wouldn't change much.