Exhaust replacement and sound difference.
12-30-2017, 09:03 AM
#21
Burning Brakes
Thread Starter
Thank you all for the information!!!
Do you guys know if there is a difference in sound between a stainless steel and a normal steel exhaust pipe? Will the diameter (2,25 vs 2,5) have an impact?
Will my ears notice any difference?
Do you guys know if there is a difference in sound between a stainless steel and a normal steel exhaust pipe? Will the diameter (2,25 vs 2,5) have an impact?
Will my ears notice any difference?
12-30-2017, 11:26 AM
#22
Burning Brakes
From my earlier response
As for the sound, SS pipes tend to have a slightly more raspy or 'tinny' sound, mostly because the SS pipe is a thinner wall construction vs mild steel however it is very difficult to notice. Your muffler choice will have a much larger overall effect on the sound of your exhaust. I would go stainless steel simply because I would not want my exhaust to rust out so quickly.
With a mild build, either exhaust will be fine. The only reason to go to a 2.5" system (in my mind) is if you eventually plan on adding more power where you would need the larger exhaust.
Last edited by PainfullySlow; 12-30-2017 at 11:39 AM.
12-30-2017, 02:49 PM
#23
Le Mans Master
Stainless will have more of a "ring" to the sound vs. alz steel. As far as size, it's not so much about backpressure as it is about flow velocity. If you take the OP stock small block & run dual 3" exhaust with either straight through or very free-flowing mufflers, you will lose some bottom end & midrange performance. Personally, I would run either a 2.25" or 2.5" setup. I would NOT run a dual 2" pipe system on any V8, unless it is something really small in displacement. Sidepipe mufflers like Hooker quiet flows or stock GM originals will rob HP because they have such restrictive (small dia.) internals & they impede flow pretty bad.
01-01-2018, 03:23 PM
#24
Im not going to go to deep on this. But backpressure is something you want. You dont want too much or too little. Same as exhaust lenght tuning as well. In F1 they even had automatic resizing exhaust pipes wich quickly got banned.
01-01-2018, 04:32 PM
#26
Melting Slicks
Exhaust tuning is actually very complex. You have velocity, heat, pressure waves and reversion to deal with. Now if you also have to deal with db level and maintain peak performance, you have quite a job to tackle.
As far as the OP's original question, I would go 2.5" as there is no downside and you can go up in HP later without having to redo the exhaust.
Mike
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PainfullySlow (01-02-2018)
01-01-2018, 06:29 PM
#27
You are confusing velocity and wave tuning used to produce the greatest output of power at a given rpm for backpressure. Backpressure is always detrimental to power output, as others have already said.
Exhaust tuning is actually very complex. You have velocity, heat, pressure waves and reversion to deal with. Now if you also have to deal with db level and maintain peak performance, you have quite a job to tackle.
As far as the OP's original question, I would go 2.5" as there is no downside and you can go up in HP later without having to redo the exhaust.
Mike
Exhaust tuning is actually very complex. You have velocity, heat, pressure waves and reversion to deal with. Now if you also have to deal with db level and maintain peak performance, you have quite a job to tackle.
As far as the OP's original question, I would go 2.5" as there is no downside and you can go up in HP later without having to redo the exhaust.
Mike
Id love for you guys to do the same and write books about it. Ill surely buy them.
01-02-2018, 02:22 AM
#28
Melting Slicks
Actually I have been designing performance and racing parts for decades. It is what I have done for a living my entire adult life. I've won many races and set many world records myself and with partners. I have also had many customers use my parts or services to win races, set records and win championships in drag, road racing and land speed racing. I've done extensive exhaust testing and design. I've spent huge amounts of time on the dyno, the street and the track, as well as many hours of computer wave simulation.
Back pressure is never desirable. Many times I have seen people putting baffles in a straight pipe thinking the back pressure is helping power and the power curve, but it is the reversion waves getting broken up by the baffle that is helping, not back pressure. Reversion waves travel as a positive wave back up the pipe, and if timed during overlap, will cause the air fuel mixture to be forced backwards out of the chamber into the intake track killing power.
Mike
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PainfullySlow (01-05-2018)
01-02-2018, 09:20 AM
#29
01-02-2018, 09:59 AM
#31
Burning Brakes
How to stop propagating ridiculous exhaust myths, by Painfully Slow.
Backpressure and velocity is determined by the headers. By the time the exhaust gasses get out of the collector and into the pipe it will not significantly affect either as long as the pipe is of sufficient diameter. Too small can affect both velocity and back pressure, too large does neither.
The end!
You can paypal me the $10 for this. Thanks.
01-04-2018, 04:53 PM
#32
Tech Contributor
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I've read most of Vizard's books, but don't recall reading that. Can you point me to which book that was, and what page?
01-04-2018, 05:23 PM
#33
Tuning the A series engine, difference between a 1.75" , 1.7/8 and 2" pipe. Quite a significant difference ( looking at the % of difference ofcourse). Page depends on your book, blue or yellow version.
01-04-2018, 06:19 PM
#34
Race Director
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I'm puzzled, as to why you would say this. WAY back, in the fall of 1976, I bought a brand new, 1977 Pontiac T/A. It had a low compression 400 cu/in engine, backed by a 4 speed transmission, and a single exhaust with a catalytic converter (just as the OP said his car currently is equipped).
Shortly after I brought the car out of hibernation, in the spring of 1977, I removed the OE exhaust system, and installed a Hooker "side mount" header set-up....4 tube headers off the engine, merging into 4" sidepipes, with the glass pack muffler inserts.
Installing that system was like taking a cork out of the exhaust. Even before I re-tuned the carburetor, to compensate for the difference in exhaust capability, the car was SIGNIFICANTLY quicker......like "night and day" quicker.
Sadly, the headers rusted out, where the primary tubes met the collectors, after only 2 summers of driving. Fun while they lasted, but the worst waste of money I ever encountered.
Shortly after I brought the car out of hibernation, in the spring of 1977, I removed the OE exhaust system, and installed a Hooker "side mount" header set-up....4 tube headers off the engine, merging into 4" sidepipes, with the glass pack muffler inserts.
Installing that system was like taking a cork out of the exhaust. Even before I re-tuned the carburetor, to compensate for the difference in exhaust capability, the car was SIGNIFICANTLY quicker......like "night and day" quicker.
Sadly, the headers rusted out, where the primary tubes met the collectors, after only 2 summers of driving. Fun while they lasted, but the worst waste of money I ever encountered.
Significantly night and day faster? You make it seem like your 77 ta when from 16s to 12s with just a set of hookers and carb tune,
If very well may have but what i saw in cases like that was a car that made more noise and made the car seem so much faster,
Do you happen to have dyno papers or time slips which seems to be the only proof some here accept
I said what i did orginally because its a fact on my 69 with a 454 built for low end torque, the long larger header tubes are more for high rpm hp builds so i could get more of what my engine is built for with a different header,
And no, i do not have paperwork, dyno slips nor have i witten any books to back up my opinions,
but feel free to go wild on google and prove me right or wrong....
01-04-2018, 06:42 PM
#35
Melting Slicks
Mike
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PainfullySlow (01-05-2018)
01-04-2018, 07:47 PM
#36
Burning Brakes
Thread Starter
Again this is talking the primary tubing size (header size). This would affect velocity and wave tuning, not back pressure. The velocity and pressure waves affect scavenging the exhaust and volumetric efficiency. Back pressure adversely affects scavenging and volumetric efficiency.
Mike
Mike
I am going for a 2.25" inch exhaust pipe, because I think it won't do that mush in HP for an L48...
The things I'm going to do extra are: an open element cleaner, Edelbrock alu RPM intake, recurve distributer and set a 'better' timing.
What HP gain will that give me? From 180HP to ...?
01-05-2018, 06:39 AM
#37
Team Owner
01-05-2018, 12:06 PM
#38
Again this is talking the primary tubing size (header size). This would affect velocity and wave tuning, not back pressure. The velocity and pressure waves affect scavenging the exhaust and volumetric efficiency. Back pressure adversely affects scavenging and volumetric efficiency.
Mike
Mike
01-05-2018, 01:01 PM
#39
Melting Slicks
Jeez! The OP wanted to know how to get a better sound and a few more ponies out of his car and now we're in some esoteric discussion "scavenging, flow, back pressure, etc". 
You guys are going to compare organ size forever! I don't think the OP is taking his car to Le Mans any time soon. And Mr, Newbie - probably not scoring any points picking a fight first time out of box! Good luck in your future posts.
You guys are going to compare organ size forever! I don't think the OP is taking his car to Le Mans any time soon. And Mr, Newbie - probably not scoring any points picking a fight first time out of box! Good luck in your future posts.
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jr73 (01-12-2018)
