quote Originally posted by lateFormula: As an end note - Dobey I'm not trying to start a flame war with you, I'm trying to help people view exhaust design a wee bit differently. So many people think "bigger must be better", but that is not true. An engine is nothing more than an air pump. If you have dyno'd an engine and know what kind of power it makes, then there are lots of resources that have published tables of exhaust pipe diameter VS engine HP. If you stick to those guidelines, you will get the most out of your build.

You seem to keep implying that We are telling people that "bigger is better" in this. We have not done that at all. Rather, We have been constantly pointing out the fact that it is not the case. The pipe diameter vs. engine HP is old-thinking. It will get you an exhaust that works, but it won't be the optimal solution for your engine. HP is not equal to air volume by any means. If you want an optimal exhaust system, you need to do the math, and not make guesses based on HP.

We were simply telling redraif that his exhaust is too big for his 3.4, and given the jaggedness, and very steep downward slope for torque after about 2700 RPM of his dyno chart, and the raspiness of the exhaust note in the upper end, that should seem obvious.

quote Originally posted by dobey: were simply telling redraif that his exhaust is too big for his 3.4, and given the jaggedness, and very steep downward slope for torque after about 2700 RPM of his dyno chart, and the raspiness of the exhaust note in the upper end, that should seem obvious.

a lot of that drop off is due to the stall on the torque converter, even more is due to the long runners with the lack of air volume getting in. I think the end solution of a turbo will be the best fix for the lack of HP and drop in power at higher rpms. But that is down the road a bit.

What has still got me baffled is the fact that you say its too big, but why was I still seeing HP and tq increases... Decent ones at that? This inquirey has yet to be addressed.

quote Originally posted by dobey: Ah, yes they do. We were looking at the Banks exhaust for Our 5.3L Silverado.

their systems have a nice note for sure

[This message has been edited by redraif (edited 10-10-2011).]

Why do people insist on doing multiple QUOTE blocks in a single reply? It makes the "Quote" button on the post not work.

Anyway, yes you are getting some gains from the big exhaust system, because there is still less restriction. But because your exhaust is too big, the exhaust gas is not moving out of the system fast enough. As it expands in the piping, the gas slows down, cools, and condenses, becoming heavier and harder for the engine to "push" it out of the system.

Your primaries should probably be about 1.25" and each primary should be about 35 inches long, and collect into a 2" system. What RPM is your valvetrain built to handle?

quote Originally posted by kikinz24: i dont know i might contemplate it after this set is done and i know exactly how i need to build them, i already have $175 in materials and thats just the mandrel bends and exhaust flanges. still havent done collectors yet... i knwo the guy in tipaei who made those headers told me he would make another set but it was going to run 900. plus international shipping... i wasnt looking to spend 1100 bux on just an exhaust that could possibly hurt my performance and just sound cool.. i will try and get these done im sooo curious to see if i can accomplish the tone...

Keep me posted on your progress. If you can duplicate this exhaust sound, I am in for a set if you make them.

quote Originally posted by dobey: Why do people insist on doing multiple QUOTE blocks in a single reply? It makes the "Quote" button on the post not work. Anyway, yes you are getting some gains from the big exhaust system, because there is still less restriction. But because your exhaust is too big, the exhaust gas is not moving out of the system fast enough. As it expands in the piping, the gas slows down, cools, and condenses, becoming heavier and harder for the engine to "push" it out of the system. Your primaries should probably be about 1.25" and each primary should be about 35 inches long, and collect into a 2" system. What RPM is your valvetrain built to handle?

Oh and sorry on the multi quote.... I used to get slammed for posting with one quote per reply and have a ton of replies grouped together.

Not sure we ever came up with the RPM abilities of the set up... You are asking the questions that were all in the theory stages... I was learning the mechanical end as we went and my partner in crime was a v-8 guy. We were doing alot of paving back then in the f-body v-6 group. Too much NEW uncharted teritorry. 3.4 block was out of a 50,000 mile car and left as is.

This was the latest combo we were working on after I found I had a cracked head. Replaced the heads (iron 2.8/3.4 rwd heads) and ported & polished the new ones more extreme then the originals (need to bench flow them) & ported the lower intake more to match. The car was choking & needed more air!

Valve train is this...
Car has new lifters & rods
Comp Cams 1.6 Roller tip rocker arms
Comp Cams 986-16 Springs
Multi Angle Valve Job retained stock valves
Reed Cam: TM276/282H12A2 (223/228 w/ 471/480 lift on 112 int C/L is 108)

Never tested it all together sadly... botched paint job in the engine bay and getting a shop to fix it has been holding things back

With an air /fuel ratio of 11...Last dyno run (added Truleo and 65mm Ford TB) on the cracked ported head had the car putting down
Max Power = 143.3 @ rear wheels (+20% for automatic tranny losses) = 171.6hp @ the fly wheel
171.6hp compared to 160hp from the factory. HP hits 140 from 4700 and holds pretty level through 5700. 143 peak is 5000-5300
Max Torque = 258.1 @ rear wheels (+20% for automatic tranny losses) = 309.72ft-lbs @ the fly wheel
309.72 compared to 200 from the factory... TQ peak is 2500 with an extreme drop due to stall...

TQ and HP cross at 52-5300
So with no other changes then the intake and TB swap I gained 36.8Ft lbs or TQ at the wheels = 44.16Ft/lbs @ the flywheel.

Oh and as far as how quick the exhaust could exit the system... the cut out was located like so (this was a pic of the old 2.25 system, but in the same place none the less)

[This message has been edited by redraif (edited 10-11-2011).]

quote Originally posted by Rick 88: Keep me posted on your progress. If you can duplicate this exhaust sound, I am in for a set if you make them.

rick if i accomplish it you will be the first to know i believe the two of us together have been after this a little over a year now.

Sound is important to lots of people. So much so in my case, that I like to drive my 87 norm asp 2.8 as much if not more than my 86 turbo 2.8 even though both cars have our intakes, headers and Y pips; whereas the turbo acts like a muffler to some extent. BTW: the turbo car has a gutted cat and the norm asp has no cat. I just the love rumble and popping when I back off the throttle. I can't wait to get the 87 back on the road with all the new engine mods including a wild cam; its built for mid-high rpm and should sound assume!

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