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Mad science exhaust Q


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22 replies to this topic

#1 shanonsf

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Posted 28 August 2003 - 11:38 AM

just for kicks,
has anyone ever done straight pipes from the heads to the rear or sides?, no cat, no H......maybe a cherry bomb on each side or not??

would it work or mess things up?

just curoius for a possible special day set up

:burnout:

rally on
shanonsf

#2 MilesFox

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Posted 28 August 2003 - 11:48 AM

had it on the sedan. worked pretty good, had good high end. although a cross pipe would help.

myoss feece has dual pipes with a x crossover, and cherry bombs towards the rear. idles quiet, but gets loud on the throttle, turns lots of heads. its on an spfi, somewhat falls flat, but it originally was on ro-neece's carbbed wagon.

you would want to have straight pipe to about the moddle of the car, or where the y pipe ends, cherry bombs, and then more pipe.

use 1 3/4 pipe off the heads, and the the 'bomb, and then 2" pipe after the bomb. the pipe before the bomb will do the scavenging, and the pipe after the bomb really doesnt matter, but fatter pipe will give you better top end and lower sound

go the cheap route and use the stock y pipe, which will do all your scavenging, then a 'bomb, and then 2" pipe the rest of the way back. makes good torque for a straight pipe

#3 Sweet82

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Posted 28 August 2003 - 12:06 PM

Miles,

You mention you got good high end and good torque. I'm building a buggy and I want low end Torque.

I have the y pipe and then 2" to a muffler. Would putting a cherry bomb like you suggest give better low end torque?

Are cherry bombs forest service approved? I don't wanna be throwin sparks.

Don't mean to steal your thread shanonsf but I was wondering the same thing.

Glenn,
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#4 MorganM

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Posted 28 August 2003 - 12:20 PM

IVe had lots of straight pipes on my EA82 SPFI. Nothing beats a good Y pipe on these guys in my opinion. With true duals they are just gutless on the lowend. With all the straight pipes ive had sure it breathed well on the top end but um... EA82s have no top end (N/A) :) The things just do not make power past 5k RPMs so all that free flow at high RPMs is just a waste. When I've had Y pipes on the difference in low end torque was considerable.

The only reason I keep straping on dual straight pipes is becuase its so damn cheap and easy. Its more of a crutch to get the thing on the road then a performance mod. Oh and dear Lord do these things sound MEAN with dual straight pipes! :brow: but belive me when you have to fly down the highway at 4k RPMs for an hour that gets old REAL fast :D

Currently I have on OEM headers, cut off and welded onto 1.75" with a slight bend just to make them hug the body. If you put on just straight pipes they will be touching the ground before they reach the rear floor boards so you gotta have that slight bend. It sounds very pissed off and works like crap. Suprisingly these are the better of the straight pipes ive put on her.

Needless to say I am trying to locate an OEM Y pipe to put back on. I built a Y pipe that worked OK but the left header flange wouldnt mate to the head flush so it leaked. Even with a leak RIGHT at the heads my low end was 2 times better then ANY of the straight pipes that had ever been on. I think a gutted OEM Y pipe woul be perfect. Everything after that would just be for show/sound :)

I remember reading a Proshe site that talked about this. And they were saying how a Y pipe is superior on boxers due to the fire order. On the EA82s the fire order is 1 3 2 4. So you are firing one head then the other. This creates a larger gap betwen 3 and 2 then betwehn 1 - 3 and 2 - 4. So if you true duals you are not promoting the scavanging effect on every fire, only on 1 to 3 and 2 to 4. This cuases performance issues on the low end due to a lower rate of pulses entering the pipes.

I dunno but I've rambled on long enough here.. just get a Y pipe and do whatever you want after the cat :)

#5 Adam N.D.J.

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Posted 28 August 2003 - 12:31 PM

I've run true 2" dual on an EA81 Brat with pretty good results. I had the heads ported out to 2" so it went 2" from the head into a 90 then 2 feet back into two 26" glasspacks, then 2 more feet of 2" pipe into a 90 pointing out. It was LOUD! above 3500, below 3K it was ohkay. Had lotsa good low end, but that may have been due to the other mods done to the engine (pistons, cam, ect.) Some glasspacks will throw sparks, also depends on how much pipe you have after them. If you get at least a 25" GP, with at LEAST 2' of pipe after it, you should be pretty safe.

#6 MorganM

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Posted 28 August 2003 - 12:43 PM

Adam: I have a feeling your engine mods do you alot of justice. You are actually utilizing 2" of flow plus dont you have a cross over tube? That helps alot also. The 90" bends prolly give you some good pressure also with the mufflers. Dont you have some pics of that system? I thought I seen some and it looked sick. If I was gonna go duals id prolly do a similar setup.

#7 Caboobaroo

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Posted 28 August 2003 - 01:57 PM

on my 79 wagon, I'm doing a dual exhaust setup. I figured out by talking to local muffler shops that putting an h-pipe in right behind the motor will help with the back pressure and help equal out the pressure in each bank making it produce more lower end power. unless you plan on straight piping it all the way to the rear, I suggest using glasspacks to help with the back pressure. But you should put in a crossover pipe in somewhere to help with the equalization of the pressure in each bank of cylinders.

#8 oobnuker

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Posted 28 August 2003 - 02:54 PM

This would REALLY be just for kicks, but what about taking an EA82T manifold and bolting on a pipe where the turbo used to sit. Punch a hole through the hood of the car and just put a friggen smoke stack on the thing! Hahahaha! Complete with little flapper thingy. I'm doing it - I swear I am doing it!

#9 MorganM

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Posted 28 August 2003 - 03:38 PM

oobnuker: I was going to do this a while back; but there are FAR more things that NEED to get done on it :( Plus someone needs it for their real EA82t since their manifold is hosed so I'm happy to give it a good home.

Of course I would have done it with a cast iron cut out so I could switch between smoke stack and something more subtle. I KNOW how loud dual straight pipes are... I dont even WANT to know how loud a smoke stack for both heads right in front of me would have sounded like! :brow:

#10 ramperf

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Posted 28 August 2003 - 06:29 PM

Shanonsf

I have tested many an exhaust on my dyno and the best way for resonance tuning an power is to make equal 33 1\2 primarys and to collect them with a 2" outlet. This system yeilded 6hp on the dyno.
Ron

#11 Adam N.D.J.

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Posted 28 August 2003 - 06:54 PM

My setup was two separate pipes. No crossovers or x's. I had about 1.5-3 psi of backpressure per pipe, depending on rpm. If you are going to do anything to the exhaust, I would highly recommend porting out the heads, this will make things soo much better. Two cylinders dumping into a 1.75" pipe isn't really that good, a good rule of thumb is about 1-1.5" per cylinder depending on displacement, but I don't like haveing less than 1" per. The turbo crossover is an ohkay idea, but only if you have a new pipe fabbed up, the stock one is way too small, and doesn't really flow good enough for an NA motor. There are about as many ways to do exhaust as there are to make a motor, many many different idea's, and even if you have 5 of the exact same motor, with the exact same components, built by the same person, all 5 of them will turn out different from each other, motors are like people, you jes have to experiment and see. It took me about 11 different combo's of trial and error to get a good setup on my 'Stang years ago. Although this may not be a good option for people that can't do their own exhaust, the gains are way good.

#12 shanonsf

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Posted 28 August 2003 - 07:21 PM

lot's of ideas here, all lean toward keeping the stock Y-pipe to the cat and then whatever back. currently I have a 1.75" pipe from the cat back into a turbo muffler. noticed a difference in pick-up and of course tone, a sweet rumble.

was curious if more could be done by ditching the cat and intersection but doesn't sound reccomended. I'm looking for low and mid range torque/power.

thx all :headbang:
shanonsf
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#13 oddcomp

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Posted 28 August 2003 - 08:09 PM

i was at a junk yard a while back looking at subes <what else>
and found a turbo wagon with a larger pipe and aftermarket cat on it
that was already unbolted and just sitting there someone hacked off the muffler from it and left the downpipe and cat....
needless to say it has a good home now and seems to work a hell of alot better than the stock restritive cat and downpipe..

#14 DoughtCom

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Posted 28 August 2003 - 11:28 PM

Yeah I'll back Morgan up, I bought it from him today, mine was dead. :(

#15 beauregaardhooligan

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Posted 28 August 2003 - 11:58 PM

Backpressure is where your torque comes from.
If you can find a good factory Y pipe, go for it. Otherwise a good muffler shop can make you a Y (not H) pipe in the stock diameter. I should think a good sized standard muffler at the back would be fine.
I was wondering the other day about using motorcycle mufflers on a crossed-over dual set-up. Their size would allow for rear mounting while retaining clearance.
Mid-mounted mufflers are the first thing to drag off-road.

#16 TomRhere

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Posted 29 August 2003 - 04:55 AM

I custom built my own 2" Dual exhaust for my '82, using electrical conduit of all things. Price was right, "Free". I have a pair of Xcelerator Turbo mufflers, ($30.00 each), on it. Mufflers are about mid-point of the doors, and the turn-outs exit just in front of the rear tires. No X or H pipe on this one, may try it on the '86 when I do that exhaust. Love to hear her "talk" as I run up thru the gears. Nice mellow "putt" at idle, and it's quiet at hiway speeds. Don't know if the lower end is affected by this set up, as I haven't driven a EA-82 powered 'Ru before this. I do know that she really starts pulling good as the engine hits 3500-4000 rpm's, and continues pulling right up to the "I had better shift now" point. Everybody that's rode in her loves the "sound" of the exhaust, and they usually want me to "get it on" when they do ride. Really sounds alot better than the cars running around here with those damned fart pipes on them. Definetly turns heads, when I nail the loud pedal. No problem with the local Police as of yet. I went with 2" piping, 'cause that's what matched the exhaust port size, and it just seemed the thing to do.......

#17 Skip

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Posted 29 August 2003 - 05:11 AM

Just one more idea.
I wanted my duel setup to sit tight against the body, most race set up use an anti reversion (balance tube, "H") so I used a Y infront of the indent in the cross member where the factory set up goes then another Y afterwards. The Ys where 2.25 the pipe is 2", I continued to the rear bumper with 2" and two free flow paks
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#18 ByTheSea

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Posted 29 August 2003 - 07:01 AM

Originally posted by ramperf
Shanonsf

I have tested many an exhaust on my dyno and the best way for resonance tuning an power is to make equal 33 1\2 primarys and to collect them with a 2" outlet. This system yeilded 6hp on the dyno.
Ron



I'm guessing that your tuning is aimed at making max Hp up in the higher RPM ranges for aircraft. Those of us running big tires and off roading usually spend a lot of time running under 3K RPM where torque is sadly lacking :( Do you have any configuration suggestions to maximize the low end, which would have been, I suppose, failures from an aviation standpoint.
Thanks, Brad

#19 ramperf

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Posted 29 August 2003 - 08:01 AM

Brad

The tuning of the exhaust is in direct relation to the intake, and for the rpm range. Aircraft props act just like a torque converter, or big tires, it stalls the engine at lower rpms therefore needing torque just like you. The exhuast tuning I was talking about is built for, torque, and the higher rpms(5700). Most primarys built are to big in relation to the intake inertia. I use 1.625 od stainless tubing and equalize the ports to flow the same this, to date, has made the best power throughout the rpm range (we test to 6300 rpms). I have made as much as 136 lbs torque @ 3300 rpms with a small cam (which is the limiting factor for aircraft).
If you read all the posts, you will see that most guys are using Y pipes,which is good. In order to make a tuned header, the primary lengths need to be exact (for equal pulse) and the diameter correct and tied with a collector.
Ron

#20 JonOfScio

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Posted 29 August 2003 - 08:02 AM

I'm looking at in the future, a dual of some sort. Probably making my own new exhaust as such...

exhaust flanges, welded to 90 degree mandrel bent pipe. I've measured it already. It'll drop 8" from the bottom of the engine to the bottom of the bend. Then immediate H pipe, haven't decided if I want a cat on both sides or not. (if so, Hi performance of course) tubing all the way back, to purple hornies, pipes exciting rear.

right now I have stock exhaust with a raptor muffler at the back with a chrome tip. A little lower than the normal sound, sounds good.

#21 beauregaardhooligan

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Posted 29 August 2003 - 09:24 AM

When I say h pipe I'm talking about what most quickie muffler shops do, a straight pipe on one side and a pipe running to it. It'll look like and *h* with a 90 degree connection, not good for performance.
A smooth flowing *Y* for a single exhaust or an *X* or double Y for duals is the way to go.

#22 MorganM

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Posted 29 August 2003 - 09:32 AM

I dig that setup Skip. How does your low end compare to the OEM Y pipe? And how upset would you be at me stealing that idea :brow: ? hehe

I just cant seem to get my hands on a "donated" used Y pipe. If the friggin EPA would back off of selling used cats I'd be fine :(

#23 Skip

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Posted 29 August 2003 - 05:11 PM

Morgan, although the pipe lengths are not equal as they should be.
The low end torque is great, (better than factory but I have a Weber also) the pipe size may be too big as it runs out of steam at about 5500 RPM. I think it is running fat in the seconday jet size as I get a loud roar when the secondaries are opened at lower RPM. I have an A/F meter just have not installed it.
The "Y" pipes (or "seat of pants" as I call em) are available from any good exhaust pipe manuf.
Hope this helps, I'll listen to Ron for my next attempt.




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