Rev pipe and a DEK, couple of questions.

[canyncarvr]

If you get junk mail on tuesday, do you jet rich?

Only if it's a non-fee based home equity loan @ 4.00% fixed, in which case, rich it is!

I have extensive background in irritability/computer meltdown/engine destruction!

On a cearious note..your mention of MAF, inlet/outlet size and such..is there any reason to expect the pipes to be the same? Or different for that matter.

[TWMOODY]

There was no Xpectations of them being the same or different just
the fact that if X goes in and Y comes out equally with both pipes
the fuel needed would be near the same.

[Jeb]

I can't stand it........

This is not correct metaphorically, but does show the point.

Apply 2" of suck to a 1/2" straw (given liquid at a given temperature, air pressure and lift). Get 'a' volume.

Apply 2" of suck to a 1" straw (all the givens the same) and you will get 2 x 'a' volume.


But...apply 1" of suck to that 1" straw..and you won't get as much as you did with the 2"...even though the 'jet' (straw) is bigger.

Ahem . . .

I'm assuming volume implies flow rate: applying the same vacuum to either straw implies that the velocity through the straw remains the same (Bernoulli's principle). But if you've doubled the size of the straw you've effected the area or two dimensions of the straw and under these circumstances the volume (flow rate) would quadruple (4x).

But wait . . . pressure differential is related to the square of the flow. Halving the pressure implies that the flow is reduced by the square root of 0.5, i.e. the flow is reduced by about 30% for a given size straw. So . . .

1" of vacuum through the 1" straw will produce 2.8x more volume than 2" of vacuum through the 1/2" straw.



I couldn't stand it either . . .

[TWMOODY]

So what does all the sucking through different size straws have to do
with MAF in and out of an engine ??

[Jeb]

So what does all the sucking through different size straws have to do
with MAF in and out of an engine ??

Nothing as long as you rejet correctly if the MAF changes between pipe changes . . .

[Indawoods]

Ya know... put the pipe on.... jet it if needed. Done.

[Jeb]

. . . Does one pipe flow faster than the other ?
Woods pipe more restricted? . . .

I betcha the flow is different but quantifying it would be tough - better to use empirical data (plug chop). I wouldn't think the difference would be huge so jetting changes should be minor.

Your "gallon per second" guesstimate would indeed be a "somewhere in the neighborhood" figure. More accuracy would depend on a good knowledge of how the differences in chamber sizes (rev vs. woods) affected backpressure, turbulence, and frictional forces which relate DIRECTLY to MAF.

Again, I'd lay money they're different - not by much, but different.

[Jeb]

Ya know... put the pipe on.... jet it if needed. Done.

You can't be serious??!! Without the deliberation?? BAH!!!

[Indawoods]

Generally... I don't care why... I just know if it needs done.. I do it. Less time and useless thought spent... more time to ride!

[2001kdx]

Generally... I don't care why... I just know if it needs done.. I do it. Less time and useless thought spent... more time to ride!

That's what i'm talking about

I'll Let these fools jabber on about this and that, I'm goin for a ride!

[Indawoods]

I have been taking more of an organic approach to things of late....

Same type discussions happen at the Guitar Building forum I belong too...

I feel like saying... SHUT UP AND PLAY!!!!

They will talk a subject to death... but until they plug in...they will never prove any theory...

I must be getting old!

[fuzzy]

While fun to discuss things more often than not I'm of the 'hillbilly engineering' philosophy when it comes to actually doing things. One of the greatest engine builders (v-8's) I know can't even read. He can, however, outfit homeade mechanical fuel injection to just about any internal combustion engine....Even saw a RM125 he did once. Don't bother him with electronics or physics....Just give him a calculator for simple machine math, his shop, and stand back. Their is no subsitute for trial and error.....The ultimate R&D!

[AZRickD]

I'll post my 2cents.

I've been alternating between that rev and torque (CC's using "-30" and "-35" gives me a headache) on the track and trail. I keep the same jettting. During the hot months 110F at 6pm at the track and 85F at 5am, I was using 148/35/CEK-3.

Now that it has cooled down to 100F-ish (but higher humidity), I've gone to 150/40/CEK-3. Last season I used a 38 pilot but decided to go one richer. Takes a bit longer to warm up, but it pulls nicely. Maybe a bit rich, but I'll live with it until it gets cooler in September (if we're lucky).

The rev pipe definately "smooths" things out, becuase it has less on the bottom. I prefer the torque pipe for the rocky climbs I have to deal with.

Rick