is there a way to add more back pressure?
07-15-2010, 12:43 PM
#26
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quite ethuggin it country boy, not your style. Go ahead drive your tractor up here... don't forget your cousin and half a deer... now please shut up and let us men talk about back pressure and how it is most likely essential for low end power. 16? lol. give me a break, rednecks make me giggle.
You made the decision to get the larger exhaust and "lost backpressure" (which you really dont want anyway). What you didnt know was that the significant difference would bother you. Unfortunately, you did things backwards. Now your at the point to where you need to change other things to make more airflow that would make the 3" useful.
Personally, if you stay with the standard supercharger, a 3"dp with a 2.5" exhaust worked well for me.
07-15-2010, 01:03 PM
#28
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Okay, so you jump ahead the first 1.5-2k rpm... then all that "back pressure" is going to let that other car pull you after you start choking the motor out.
You made the decision to get the larger exhaust and "lost backpressure" (which you really dont want anyway). What you didnt know was that the significant difference would bother you. Unfortunately, you did things backwards. Now your at the point to where you need to change other things to make more airflow that would make the 3" useful.
Personally, if you stay with the standard supercharger, a 3"dp with a 2.5" exhaust worked well for me.
You made the decision to get the larger exhaust and "lost backpressure" (which you really dont want anyway). What you didnt know was that the significant difference would bother you. Unfortunately, you did things backwards. Now your at the point to where you need to change other things to make more airflow that would make the 3" useful.
Personally, if you stay with the standard supercharger, a 3"dp with a 2.5" exhaust worked well for me.
and now i know to get my TVS *before* i get my 3"
07-15-2010, 01:37 PM
#30
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my best guess is w.hile o.n t.hrottle.
07-16-2010, 12:03 AM
#36
Goddamnit people...
Backpressure is BAD, always, no matter what. Exhaust VELOCITY is what you aim for. Exhaust scavenging effect is based on piping size vs. RPM. There is an ideal point for a scavenge effect based on the exhaust primary size and length, along with a ton of other smaller factors, like collector design, multiple merges, all change the effective point or make it a broader area, but it's only one place in the rpm range. Bigger pipe will raise your 'ideal' rpm. It's easy to move your ideal point out of the normal rev range.
As far as "my bigger exhaust made me lose power", no, it just moved the peak higher than you are capable of hitting.
In the LSJ case, you don't need a scavenge effect once you have positive intake manifold pressure, generally speaking. The very slight overlap of the cams lets the intake charge push the exhaust out. If you've lost a small bit of part-throttle torque at low rpms, you can either step down a little more on the gas or rev a little higher in each gear.
I hate these threads...
Backpressure is BAD, always, no matter what. Exhaust VELOCITY is what you aim for. Exhaust scavenging effect is based on piping size vs. RPM. There is an ideal point for a scavenge effect based on the exhaust primary size and length, along with a ton of other smaller factors, like collector design, multiple merges, all change the effective point or make it a broader area, but it's only one place in the rpm range. Bigger pipe will raise your 'ideal' rpm. It's easy to move your ideal point out of the normal rev range.
As far as "my bigger exhaust made me lose power", no, it just moved the peak higher than you are capable of hitting.
In the LSJ case, you don't need a scavenge effect once you have positive intake manifold pressure, generally speaking. The very slight overlap of the cams lets the intake charge push the exhaust out. If you've lost a small bit of part-throttle torque at low rpms, you can either step down a little more on the gas or rev a little higher in each gear.
I hate these threads...
07-16-2010, 12:12 AM
#38
heres exhaust 101 from two guys garage. i watched this on tv and had been waiting for one of these threads to come up.
http://www.youtube.com/watch?v=n8VlynaUVO8
watch it ALL THE WAY THROUGH
http://www.youtube.com/watch?v=n8VlynaUVO8
watch it ALL THE WAY THROUGH
Last edited by EXsoccer1921; 07-16-2010 at 12:12 AM. Reason: Automerged Doublepost
07-16-2010, 01:14 AM
#43
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Back pressure, no back pressure.... its been argued as long as I can remember. It really just depends on where you want your power. I lost so much low end when I went with an ORX and SLPs on my Mach, that I had flows welded in the same day. It regained low end immediately and IMO made the car more livable and suited me better on the track as well. Others may have preferred the slight gain in top end over the lost low end. The key is to open up the exhaust and even out the exhaust pulses without opening it up so much that you start to lose velocity, among other things. There is a point in which you are opening your exhaust too much.
Turbo cars are a totally different deal, of course.
Turbo cars are a totally different deal, of course.
07-16-2010, 01:15 AM
#44
He's also reaching on some of his ideas. Longtubes aren't getting a scavenge merge at the H pipe. Look into 180degree V8 headers. They make power over any other setup.
I'd suggest anyone seriously interested in this subject do a little research on exhaust tuning theory, it's not that hard to understand and you will realize just how many people out there have no ******* clue what they are talking about.
Video was a good starter for an uneducated viewer, glad to see he actually went into the technical aspect of how a header gains power.
07-16-2010, 02:14 PM
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It's an interesting video, but it doesn't apply to the conversation at hand. Stone's post sounds more along the lines of what the situation is.
Joe, got any good places to start for a SCed engine? Most exhaust tuning info is based on non-boosted cars.
Joe, got any good places to start for a SCed engine? Most exhaust tuning info is based on non-boosted cars.
07-16-2010, 02:24 PM
#46
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Wide open exhaust punch a hole in the hood and run straight pipes out of it. Very annoying not very efficient or astetically pleasing but is cheap and functional. J/K lol
07-16-2010, 02:51 PM
#49
no i'm not comparing numbers. just think its funny that people think i don't know what i'm talking about
people just keep beating a dead horse about you need this exhaust for this amount of power, etc..etc.. when the right setups are out there and have already been proven.
people just keep beating a dead horse about you need this exhaust for this amount of power, etc..etc.. when the right setups are out there and have already been proven.
Last edited by EXsoccer1921; 07-16-2010 at 02:52 PM. Reason: Automerged Doublepost
07-16-2010, 02:56 PM
#50
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looks to me like there was boasting about highest hp on blah blah...looks like comparing dyno #'s to me *shrug*
of course there's the chance it would open up the final number but do we really go for a nutswinging peak number too?
I know I don't, I'd rather have what makes the most throughout the whole powerband, call me crazy...
of course there's the chance it would open up the final number but do we really go for a nutswinging peak number too?
I know I don't, I'd rather have what makes the most throughout the whole powerband, call me crazy...