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There are general rules of thumb but typically a single 3.5" exhaust should support N/A 350 to 450 rwhp. It would likely support more in a forced induction set-up.
My setup should make around 700-715 FWHP. Based on your answer, not enough. Really didn't like single outlet anyway. Had to ask.
A 4" single still won't be enough. You might get by though if your forced induction, as the exhaust is pressurized more. If I were you I would be looking into the 3" duals and the necessary fab work that will come with it.
I know for a fact he ran it through the muffler being it was raced in true street which requires mufflers.
Interesting. I am sure he is leaving power on the table. Boosted cars can get away with a smaller exhaust due to the increase in scavenging and increased exhaust pressure.
We run 600 HP with forced induction through 3" single exhaust all the time. It's not a problem according to my dyno.
GD
Also interesting. Did you ever dyno it with a larger exhaust to see if you were leaving power on the table? FWIW, For N/A setups Holley says their dual 2.5" blackheart set-up is suited for 450rwhp or less.
Also interesting. Did you ever dyno it with a larger exhaust to see if you were leaving power on the table? FWIW, For N/A setups Holley says their dual 2.5" blackheart set-up is suited for 450rwhp or less.
Sounds more like a muffler issue they are using more so than the exhaust size to me. I have seem better results with dual 2.5".
In the sport compact world, pretty much everyone runs 3". Plenty of people running 800-1000 HP through 3" exhaust. The turbine inlet of the turbocharger is usually 3" or smaller. The engine is an air pump with typically smaller exhaust valves than intake valves so if a 3" inlet will make that much power, then you really are never going to use a 3" exhaust. Of course you have to have 3" straight through from the turbo all the way to the muffler. But we really don't run into exhaust restriction problems and virtually no one even makes anything larger than 3".
A 3" exhaust will make a LOT of power. Larger than 3" is really hard to work with also. 3" is about 30% more flow than 2.5". Also consider that the further you get from the engine as the gasses cool they condense. So 2.5" collectors feeding a 3" isn't a huge deal.
The largest we see on cars making well over 1000 wheel HP, is 3.5" transitioning to 4" at the muffler.....
I have that 3.5" exhaust system. Tailpipe is a turn down that is hidden behind the bumper.
My car makes 480 RWHP on a mustang dyno and that exhaust doesn't hold it back at all. The engine actually lost mid-range torque without the muffler, and lost even more mid-range torque with 3" dual open pipes that dumped behind the tranny. The best torque curve was full exhaust.
This spring I'll be dyno tuning a new naturally-aspirated combo that is proven to easily eclipse 600 RWHP with 3 inch dual exhaust. it's going to be easy to see how much the single 3.5 exhaust holds it back because I already know what the number should be.
I have a 400 sbc with 1.75" headers 3" Y pipe and 3.5" out the back with a SW Muffler. My car made close to 700rwhp on 175 shot through the muffler. I do have a cutout but never opened it on the dyno, but based on my track experience there isn't much difference. On a different motor previously but still 400 sbc with SLP shorty headers with 2.25" Y pipe to 3" exhaust it made 620rwhp with 150 shot through muffler. based on my experience you can go very far with smaller diameter pipe . Before I was just replying what I knew about that specific system vs I am sure my system is different especially header primary size. Here is a pic of my custom Y pipe for reference.
Last edited by firebrdo88; Jan 17, 2019 at 09:45 AM.
I have a 400 sbc with 1.75" headers 3" Y pipe and 3.5" out the back with a SW Muffler. My car made close to 700rwhp on 175 shot through the muffler. I do have a cutout but never opened it on the dyno, but based on my track experience there isn't much difference. On a different motor previously but still 400 sbc with SLP shorty headers with 2.25" Y pipe to 3" exhaust it made 620rwhp with 150 shot through muffler. based on my experience you can go very far with smaller diameter pipe . Before I was just replying what I knew about that specific system vs I am sure my system is different especially header primary size. Here is a pic of my custom Y pipe for reference.
Any forced induction will allow you to get away with small exhaust due to how much greater the energy is in the exhaust cycle. I'm more worried about N/A power which is more sensitive to exhaust sizing. Maybe I will reconsider the blackheart system or the mufflex 3.5 (500rwhp).
I have a 400 sbc with 1.75" headers 3" Y pipe and 3.5" out the back with a SW Muffler. My car made close to 700rwhp on 175 shot through the muffler. I do have a cutout but never opened it on the dyno, but based on my track experience there isn't much difference. On a different motor previously but still 400 sbc with SLP shorty headers with 2.25" Y pipe to 3" exhaust it made 620rwhp with 150 shot through muffler. based on my experience you can go very far with smaller diameter pipe . Before I was just replying what I knew about that specific system vs I am sure my system is different especially header primary size. Here is a pic of my custom Y pipe for reference.
Do you have more pics of your exhaust? Looks nice from what I can see in this pic. Looking to go with an exhaust that looks similar to yours since I have long tubes with my LS1 swap, and I have a custom dual exhaust with terrible ground clearance now.
hmm, glad I came upon this thread. Next winter I will be dropping in a 525 hp engine from Nyes performance link: http://nyesautomotive.net/406_525hp_EFI.html I also plan on running a 200 wet shot of nitrous on it, since my car already has nitrous in it, i'll just simply need to run two new lines from the solenoids to a carb style plate. the nitrous will probably just be for the track, since I am sure the 525 hp will be just fine on the street. I was hoping to re-use as much of my current exhaust .. at least for the first year.. since I will be spending big $ on the engine itself.
currently its a DynoDon's 1 5/8ths/ (i think 1 5/8, I'll measure, but I doubt they are 1 3/4) to a DynoDon's y pipe ending with a hollowed out 3" magnaflow cat. then a 3" hooker cat-back system, with an electric cutout that dumps before the axle.
I know it is unlikely I will have another $1,000 for headers/exhaust during the engine install, so I was hoping to run this setup for about a year or so.
what do you guys think? will these dynodons headers, y-pipe, 3" hooker cat back with a cutout be good/safe/proper enough for the 525 flywheel hp on the street and then also with a 200 shot at the track (cutout open probably).
Well I'm in the teardown stage of the car getting it ready for the paint shop. The engine is a N/A 440LSX. I like the fact that the Stainless Works/Hawks setup is all bolt together but again, just hope it works well with my setup. I'll continue to examine others systems and appreciate your input. Thanks.
I have a 400 sbc with 1.75" headers 3" Y pipe and 3.5" out the back with a SW Muffler. My car made close to 700rwhp on 175 shot through the muffler. I do have a cutout but never opened it on the dyno, but based on my track experience there isn't much difference. On a different motor previously but still 400 sbc with SLP shorty headers with 2.25" Y pipe to 3" exhaust it made 620rwhp with 150 shot through muffler. based on my experience you can go very far with smaller diameter pipe . Before I was just replying what I knew about that specific system vs I am sure my system is different especially header primary size. Here is a pic of my custom Y pipe for reference.
Bud can you post pics of your trans crossmember. Or if you have blue prints?
this is exactly what my car needs.
i see you have the mid mount torque arm. How do you like it? Any mounting issues with the exhaust or sub frame connectors?
