Ok I am working in the exhaust of my car for my SC setup. I have the idea to make progressive exhaust to retain some gasses velocity to improve high-end without losing too much torque in lower band of rpms.
My idea is to use an old RK Sport 4-1 header cut at 2.5" part, going to a pair of 16"x2.5" resonators and finishing in a 2.25" rear part to a Magnaflow 2.25" muffler. I think that can loose some low-end with a complete 2.5" custom mandrel bend cat-back.
What do you think friends? ideas and suggestions are welcome.
Thanks,
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Man, i've also thought about doing that also, but i kinda started thinking, maybe i'm wrong, but once your exhaust really builds up at high rpms, it would pretty much be like having it at 2.25 all the way anyways. Like i said, i could be wrong, but it's not a bad idea bro, i haqd the same idea....hell, i still maybe do it?!
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With a supercharger (or any sort of boost really) there's a whole lot more exhaust coming out of the engine over a NA setup, so you'll benefit from larger piping to begin with.
So if you're going to do a progressive set up, have it start smaller and get larger towards the back, otherwise like brian mooney said, it'll be like having the smaller piping the whole way back. Start at the header with 2.5", run 2.5" through a cat and straight through resonator, then enlarge it to 2.75" (or even 3" depending on how much power you're pushing) to bend over the axle and out a straight through 2.75" (or 3") muffler.
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I thought that in the case of try to maintain high exhaust velocity over whole cat-back should be better to have a pipe size near the engine and a small one at the back.
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Ok friends. After some research I found some facts that indicate me that a progessive exhaust design should be as Spilner521 said.
The fact is the a compressed gas tends to go from a high prerssure area to a low pressure, that produce some kind of suction and maintain high velocity exhaust gas column. Headers works in the same way trying to scavenge as much as exhaust gas as it can, going from a long and small diameter pipe to bigger diameter one. In fact I think that exist some brands of headers, FlowTech, Heddman, etc.... and other that uses this torque-step design. This is nothing more than a small pipe going to bigger pipe.
All this story inclusive follows the idea that the whole exhaust diameter will be of the biggest pipe in the system. Also the exhaust system works different than the intakes systems. If you seen an AEM V2 or an Iceman intake, the air is under suction from the ambient to the engine (low pressure to a high pressure), then you see that the intake have a bigger pipe near the filter is smaller near the TB to add velocity an a column push effect. Exhausts works exactly in the opposite way, the air is pushed.
Also I found some empirical info for 4 cyl engines that indicate me that a 2" can support 150BHp, 2-1/8" 175BHp, 2-1/4" 200BHp, 2-3/8" 225BHp, 2-1/2" 250BHp, 2-5/8" 275BHp, 2-3/4" 300BHp and 3" 350Bhp. If you can uses the desired diameter, go one step smaller to retain torque in the powerband or goes one step bigger for more HP.
Well my dilema is that I can't find mandrel-bent bends in my country and I would have to import from USA. That means almost 3 weeks, due to the size, weight of the package and price of the shipping. Thinks that I already have 2 resonators and one big muffler in 2-1/2".
Finally my idea will be to make a 2-1/4" pipe section from the header downpipe, going through the resonators and a 2-11/2" compressed-bent to the Muffler.
What do you think friends? Do you think that I am crazy or the idea is good? I realñy appreciate your comments.
Thanks,
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i got on my s/c set up.
isuzuperformance header- 45inch 2.5inch glass pack, rk single exhuat cat back 2.25 inch piping over the axle, then a 2.5inch dynomax muffler. i love it.
your idea sounds good and u are on the right track.
Team GREEN
Jake that idea sounds excelent but remember that I am talking about compressed bends.
My idea could be: a RK Sport 4-1 header, 2.25" downpipe and flex pipe, 2.5" resonator, O2 simulator in a 2.25" pipe, 2.5" resonator, 2.25" straight pipe up to the rear crossmember, 2.5" compressed bent pipe, 2.5" muffler and 4" Tip. That is what I mean going from 2.25" to 2.5". Sometime ago I remember that Lenko says that a compressed bend could be 1/4" less than the normal diameter. Then a 2.5" compressed pipe above the rear crossmember, could be equal to a 2.25" mandrel bent but with some turbulence.
The other option will be forget the whole story and make all cat-back 2.5" compressed bend.
Have you notice that the fastest SC cars in JBO are using 2.25" cat-backs not 2.5"?.
Of course using stock 2.8" or 2.7" pullies.
Maybe I am drowning in a glass of water, but I will to do the things right.
Thanks again for your patience.
Regards,
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then go 2.5 compression bent. it aint going to make that much of a difference.
Team GREEN
I was thinkin about doing a 2.25 downpipe to a 2.5 resonator, 2.5 mandrel bends 3 inch muffler
then I got a free exhaust.... IDK, probably still gonna do it.
Scott
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You've displayed wayyy too many acts of pushing people to their limits.
It's never cool to tear people down for what they want to do.
NEJBODY is a team. We're not the same as JBO where everyone bashes on eachother.
I'm surprised you show up to our meets after half of the things you say on here.
if your gonna bottle neck to 2.25 just run a 2.25 inch exhaust the whole way, itll flow bwtter ans be less turbulent.
if anything step it up from 2.25 to 2.5 or 2.5 to 3.
This exhaust is not for a turbo car, so 3inch would probably not gain you any HP over a 2.25 setup. All you would do is loose torque
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After some research, finally I can conclude that a progressive exhaust will be done by going from a small pipe to a bigger one.
Check out this email answer:
The proper way to work progressive piping is to go from smaller to larger. However, most people do this based on space limitations underneath the vehicle. If you car only allows for smaller piping at the beginning of your exhaust, but larger piping can fit towards the end of the exhaust, then, progressive piping will work to your advantage for maximum exhaust flow.
Feel free to contact me should you have any other questions.
Best Regards,
Deryck Griffith
Inside Sales / Customer Service
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Vibrant Performance
www.vibrantperformance.com
For my needs my best option will be going with a 2.25" cat-back, maybe a RK Sport Single cat-back exhaust.
Regards,
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