Mazda actually did something similar with the RX7's where they had both a pea-shooter exhaust and a big monster exhaust system on the same car, and there was a lever or a switch in the cabin that let you change between the two, so you could have great economy with crap performance, or crap economy with awesome performance.
As an offshoot, mazda were also tinkering with variable length tuned inlet runners on their racecars, the inlets were two pipes one inside the other that slid in and out to make the runners long at low rpm and as the revs climbed the runners got shorter and shorter. This gave them some fantastic torque capability right thru the rev range. Very clever stuff at the time, but I think it got outlawed because of some stupid rule or another. There's a lot to be said on the subject of variable lengths and tube sizes both inlet and exhaust. Unless you have a few million dollars backing you with scientific testing, you can only do what we all do and settle on a happy medium. ----- Original Message ----- From: "Richard Webb" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, April 27, 2004 6:15 PM Subject: Re: exhausts questions > > > > > I'm sure I read on autospeed or somewhere about flanges to make your > exhaust effectively smaller. It was something to do with noise but if > Geordies theory is correct this would be great to have to progressively > open as the rpm's increase. Anyone know of such a system? or would the > complexity of it outweigh (literally) the benefits? > > > > > From: [EMAIL PROTECTED]@datascribe.com.au on 27/04/2004 16:48 > ZE10 > > Please respond to [EMAIL PROTECTED] > > Sent by: [EMAIL PROTECTED] > > > > To: <[EMAIL PROTECTED]> > > > cc: > > > > > > > Subjec Re: exhausts questions > t: > > > > > > > > > No scientific basis here, but I am under the impression there is an optimum > pipe size for flow > too small and it's restrictive, too large and you don't get the air speed > you need. > > Ideally, you would have a small pipe for low rpm and a larger pipe for > higher rpm when more gas needs to flow. and everything inbetween but we all > know that pipes can not change size all by themselves :D > > So a typical exhaust system is a compromise of some sort, whether it is > midrange pipe size optimised for midrange power or larger pipe size > optimised for high end power. > > ----- Original Message ----- > From: maldat > To: [EMAIL PROTECTED] > Sent: Tuesday, April 27, 2004 4:12 PM > Subject: Re: exhausts questions > > I use 4-1 headers that are quite long, the 4-1 collector is just about > under the seat. > I also use a exhast thats one size down from 2"..everyone else had 2+" and > my car was faster..?? > > Malcolm > "new theory, you can move more air quicker thru a smaller pi[pe than a big > one.... what do you guys think of that?. > > ----- Original Message ----- > From: Jeff Oldham > To: [EMAIL PROTECTED] > Sent: Tuesday, April 27, 2004 1:51 PM > Subject: RE: exhausts questions > > There is some debate about exhausts being too big & not providing enough > back pressure. > But i think its only the first part of your exhaust (the headers) that > affect this. > that why some new exhaust systems run variable exhaust manifolds as it > affects your torque at various revs. > > go to about halfway down on this web page for some info. > > http://www.autospeed.com/cms/A_46/article.html > > > I am running 4-2-1 motivator extractors into 2 1/2 with 3" tail pipe & > turbo muffler. > the 4-2-1 (or "y" extractors) give a slightly more spread torque range > than 4-1 > I think 2 1/2 inches is biggest that will fit in the rear cross member of > a 510 > without enlarging the hole :) > > When i got rid of the bit of curtain rod that was on my car i noticed not > more power > but that the engine felt like it could rev out further easier. > > BUT i could have it all wrong so ask some professionals :-) > cheers Jeff > > > > > > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of kla > Sent: Sunday, April 25, 2004 12:47 AM > To: [EMAIL PROTECTED] > Subject: exhausts questions > > I've been wondering about sports exhausts, as i was thinking of > getting a system installed (extractors to the back) > and i was wandering. as a general rule. sizes. obviously too small > means not enough flow, but what about big? > what happens when you get too big, and what is generally the best > size for a 1.5litre (standard, non-turbo etc.) > if its too big do you get a dead space effect where it cant move > enough of the air or what? > cheers. > > --membersozdat---------------------------------------------------- --- > > OZDAT Mailing List Please Note:- > Send (un)subscribe requests to [EMAIL PROTECTED] > Send submissions to [EMAIL PROTECTED] > No unauthorised redistribution of this email > http://www.ozdat.com/ozdatonline/index.htm > http://www.ozdat.com/ozdatonline/listindex.html > http://www.mail-archive.com/[EMAIL PROTECTED]/ > ------------------------------------------------------------------ --- > > --membersozdat------------------------------------------------------- > OZDAT Mailing List Please Note:- > Send (un)subscribe requests to [EMAIL PROTECTED] > Send submissions to [EMAIL PROTECTED] > No unauthorised redistribution of this email > http://www.ozdat.com/ozdatonline/index.htm > http://www.ozdat.com/ozdatonline/listindex.html > http://www.mail-archive.com/[EMAIL PROTECTED]/ > --------------------------------------------------------------------- > > --membersozdat------------------------------------------------------- > OZDAT Mailing List Please Note:- > Send (un)subscribe requests to [EMAIL PROTECTED] > Send submissions to [EMAIL PROTECTED] > No unauthorised redistribution of this email > http://www.ozdat.com/ozdatonline/index.htm > http://www.ozdat.com/ozdatonline/listindex.html > http://www.mail-archive.com/[EMAIL PROTECTED]/ > --------------------------------------------------------------------- > > --membersozdat------------------------------------------------------- > OZDAT Mailing List Please Note:- > Send (un)subscribe requests to [EMAIL PROTECTED] > Send submissions to [EMAIL PROTECTED] > No unauthorised redistribution of this email > http://www.ozdat.com/ozdatonline/index.htm > http://www.ozdat.com/ozdatonline/listindex.html > http://www.mail-archive.com/[EMAIL PROTECTED]/ > --------------------------------------------------------------------- > > > > > > > --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/[EMAIL PROTECTED]/ ---------------------------------------------------------------------
