tailgatewagon Posted October 21, 2004 Share Posted October 21, 2004 if it was going to be for comp use or with total disreguard to laws and the enviroment:brow: is there a best size for staight pipe an ea82t, i know that back pressure isnt needed because of it being turbo (no scavangeing needed) so i was thinking 3in or so, anyone running 2.5 straight or 3in? my last car an 87 carb wagon had 2.5 straight back from a gutted cat. it had lost some of its low low end but had way more from about 4500 to 7000ish(where ever the valves start to float), any thoughts. Link to comment Share on other sites More sharing options...
garner Posted October 21, 2004 Share Posted October 21, 2004 If I remember correctly, mudrat's rally-x jalopy (RX sedan) is running 2.5" from the turbo, with a divorced waste gate dump pipe. At about the point that the exhaust clears the tranny mounts, it goes up to 3", no cats, no mufflers, all boxer!!! It's a monster It's not too loud unless you're really on the gas hard. Nice thing about turbos is that they "chop up" the exhaust into smaller pulses so not as loud as NA motor Back pressure is not as much an issue with turbo motors but if you look at high performance exhausts for WRX's 3" is as big as they get. garner Link to comment Share on other sites More sharing options...
tailgatewagon Posted October 21, 2004 Author Share Posted October 21, 2004 what would be the reason for the devorced waste gate pipe.? whats the effect of having it that way instead of all one pipe. ? where would be the best place to put the o2 senssor??? same distace from the turbo as it is now? Link to comment Share on other sites More sharing options...
NorthWet Posted October 21, 2004 Share Posted October 21, 2004 ... i know that back pressure isnt needed because of it being turbo (no scavangeing needed)... The following rant is NOT directed at the poster, but rather at some commonly held beliefs, which, I feel, the poster is wisely trying to disregard. WARNING! Heresy follows: Maybe I am ignorant (probably ) or decades behind the times (certainly! ), but why do so many people think that back pressure is needed for anything, or that what is done beyind the firewall has anything to do with scavenging? Literally been decades since I ran the formulas, but as I recall any exhaust pulse effects reflected to the valve pretty much become a non-issue at lengths greater than about 3 feet. (Unless we are talking industrial (SLOW) engines). The first turn or change of pipe diameter muddies up the effect, as does every subsequent one. Hit a turbo or cat or muffler, and that is it. After that, anything that is not more restrictive should be fine. WWII V12 plane engines usually ran with 18"-ish exhaust stacks... And backpressure is not essential, other than a given design expects a certain level of backpressure to work with it. Change the backpressure and some other aspect of engine tuning should be addressed (e.g. cam timing or fuel mixture). So, IMHO , run port-sized pipe to the first major reflection point or 3 ft, whichever comes first, and then as big as you want back to the rear. I like things quiet in my senility, so I would want a good quality, LARGE VOLUME muffler, with 2 or more smaller outlets. End of rant. Thank you for not burning me alive. Please??? Link to comment Share on other sites More sharing options...
garner Posted October 21, 2004 Share Posted October 21, 2004 what would be the reason for the devorced waste gate pipe.? whats the effect of having it that way instead of all one pipe. ? where would be the best place to put the o2 senssor??? same distace from the turbo as it is now? The divorced waste gate dump pipe helps keep the main exhaust moving smoothly. In the stock DP, when the waste gate dumps, turbulence is generated and can lead to slowing down the turbo (in theory anyhow) Check out some of the WRX after market DPs like the one made by Perrin:slobber: http://www.perrinperformance.com/products/downpipe/downpipe.htm I'd keep the 02 sensor as close to the turbo as it is now, keep it hot so it reads... garner Link to comment Share on other sites More sharing options...
archemitis Posted October 21, 2004 Share Posted October 21, 2004 that wastegate dump works better with a boost contorller, so the exhaust only gets super loud, when you hit full boost. it sounds mean as hell. id go with 2.5 if nothing else just so it wont scrape on the ground. 3 inch piping is freakin huge! and on the no back pressure thing. if you run a na subaru with no back pressure, you will be hating life, wespecially if you like low end torqe and offorading. Link to comment Share on other sites More sharing options...
oddcomp Posted October 21, 2004 Share Posted October 21, 2004 uh remote wastegate is more efficient at maintaining boost levels and usually remote gates have the little bolt you turn in to bring up the boost but like integral wastegates they still suffer from the effects of cracking pressure where before the boost psi can overcome the spring tension fully they sorta "crack" open a bit electronic boost controllers overcome that annoyance resulting in faster max boost better response even with out electronic boost controls a remote waste gate is far better than stock integral type.. i mean you don't see any formula 1 cars with a tiny stock integral wastegate do you.... ? Link to comment Share on other sites More sharing options...
Subi81 Posted October 21, 2004 Share Posted October 21, 2004 My brother had a 2.5 downpipe to 2.5 straight pipe to a flowmaster and it spooled rather nicely, but it was a little loud, incase you say wanted to sneek away from your girlfriends house or something unnoticed. Link to comment Share on other sites More sharing options...
archemitis Posted October 21, 2004 Share Posted October 21, 2004 an external wastegate is something different than im talking about. you still use the internal wastegate, but you weld a seperator into your turbo... seperates the wastegate from the exhaust. then you weld seperate pipes, for the two seperate passages, on the same flange. the wastegate gets like a 1.5 inch pipe, and the other gets 2.5 inch. but external wastegates rule, know where i can get one cheap? Link to comment Share on other sites More sharing options...
NorthWet Posted October 21, 2004 Share Posted October 21, 2004 ... i mean you don't see any formula 1 cars with a tiny stock integral wastegate do you.... ? I'll have to check around town... As far as mufflers, loud does not equal power and vice versa. You can still get reasonable quiet and good flow. Just requires good engineering and the desire to be quiet. (Quiet does not sell to the go fast crowd.) Good design, large internal volume small multiple outlets. Check out a muffler on a Mercedes, Lexus, or similar vehicle. Link to comment Share on other sites More sharing options...
rallyruss Posted October 21, 2004 Share Posted October 21, 2004 I made a seperate wategate exit tube on a down pipe before. I dont know if it helped much. not exactly the same thing as an actual external waste gate. if you run cats you dont need much in the way of mufflers. as long as you run it all the way out the back. if it ends under the car it is a bit anoying. now why would you need to sneak away from the GFs house? Link to comment Share on other sites More sharing options...
stngllhm Posted October 21, 2004 Share Posted October 21, 2004 i'm running 2.5" from the turbo back. had it straight for a while than i got tired of the noise so i got a turbo muffler from autozone for like $16 it is not much louder than stock and i didn't seem to lose any power after putting the muffler on. it accully made it quieter than i wanted<G> Link to comment Share on other sites More sharing options...
NorthWet Posted October 22, 2004 Share Posted October 22, 2004 ...if you run cats you dont need much in the way of mufflers. as long as you run it all the way out the back. if it ends under the car it is a bit anoying... I'd put SOMETHING on the end just to cut down on the "farting in a sewer pipe" sound of a straight pipe. ...now why would you need to sneak away from the GFs house? Don't know... I'lll have to ask the wife when she gets home. Link to comment Share on other sites More sharing options...
subarubrat Posted October 22, 2004 Share Posted October 22, 2004 I ran a 3 inch turbo back straight pipe on my RS-turbo for 4 years and I am currently setting up the same thing on the STI. I would see no reason why the 82T would not work fine with the same setup. Link to comment Share on other sites More sharing options...
mitch184 Posted October 22, 2004 Share Posted October 22, 2004 i just finished putting my exhaust my 87 turbo wagon. I have 2 in. downpipe and 2 in. exhuast all the way back. No cats or muffler anywhere. The spool up time is crazy. I get 10 psi around 2000 rpm. Full boost 12 psi. around 2100. Boost starts coming in good around 1600. Its awesome. I do get boost creep up to about 14 psi though. It is not terribly loud. Sounds great at a low 600 rpm idle. Only downside is compression braking. It is quite loud and filled with popping, cracking, and a few backfires. All in all it is a liveable sound and the performance difference is great. Link to comment Share on other sites More sharing options...
rallyruss Posted October 22, 2004 Share Posted October 22, 2004 I'd put SOMETHING on the end just to cut down on the "farting in a sewer pipe" sound of a straight pipe. Don't know... I'lll have to ask the wife when she gets home. the turbo and then cats really quiet it down. I do run a muffler now but the RX that is now my cousins is not all that loud with no muffler( it does have cats) Link to comment Share on other sites More sharing options...
NorthWet Posted October 22, 2004 Share Posted October 22, 2004 the turbo and then cats really quiet it down. I do run a muffler now but the RX that is now my cousins is not all that loud with no muffler( it does have cats) Not talking about volume of noise so much as quality of noise... Sound passing down a pipe creates dissonant sounds that personally annoys me. Yet another personal quirk. Link to comment Share on other sites More sharing options...
jazzician Posted October 22, 2004 Share Posted October 22, 2004 i just finished putting my exhaust my 87 turbo wagon. I have 2 in. downpipe and 2 in. exhuast all the way back. No cats or muffler anywhere. The spool up time is crazy. I get 10 psi around 2000 rpm. Full boost 12 psi. around 2100. Boost starts coming in good around 1600. Its awesome. I do get boost creep up to about 14 psi though. It is not terribly loud. Sounds great at a low 600 rpm idle. Only downside is compression braking. It is quite loud and filled with popping, cracking, and a few backfires. All in all it is a liveable sound and the performance difference is great. I'm putting an exhaust setup on my 89 GL10 Turbo tomorrow. It's an MSL 2" in and dual 1 1/2" out. I've had a 2 1/2 " straight pipe also with no cat/muffler and it's freakin loud and pop, farts, belches and backfires all the time and I also found that I got compression braking. If I had to have my back seats down for some reason or other my ear drums paid the price.I'm looking forward to hearing the turbo spool up. Past all of that, I will miss the grumble of the engine as it sits idling. Oh well. Hopefully with the new setup, I shouldn't miss out on too much flow. Simon Link to comment Share on other sites More sharing options...
baccaruda Posted October 22, 2004 Share Posted October 22, 2004 here's mine... I have 2" straight down from the turbo, then 2.5 grafted on (you can see the seam in this picture) with no cats and a straight thru muffler. the graft is a little ugly as the DP was sort of a "whatcha got?" job. sounds nice and angry though Link to comment Share on other sites More sharing options...
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