Hey guys i wanna do a custom exhaust on my infiniti j30 which basically has the same motor as a 300zx n/a the vg30de v6 but i was wondering should i go with 2.25 or 2.5 piping? I dont have any other mods on the car and dont really plan on adding anymore i just want to put a exhaust system on it for now but i dont wanna go with the wrong size and cause problems.
2.25 or 2.5" Exhaust?
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I've gotta believe 2.25 is good. what mufflers do you intend to use?
My Neon's was 2.25" stock, and most modded motors didn't need an upgrade, but 200hp was about as much as anyone got NA out of them. I don't think you'll have any problems with 2.5" being to big or 2.25" being terribly small. You can't go wrong with stock size though, it won't be sized to lose any hp in a car like that.
2.25" mandrel bent pipes can probably equate to 2.5" crush bent exhaust pipes.
yea they wont be mandrel bent so should i go with 2.5"? Im getting them done at a muffler shop.
Once the mod addiction hits, you will be glad you have 2.5" pipes.
there arent really anymore mods that can be done to this car besides custom exhaust and air intake. The parts on the 300zx do not match up because of clearance issues etc but the motors are both the same.
I thought it was the same on my CRV. Who, in their right mind would modify a CRV? I started with a larger K&N air intake and more recently installed a custom throttle body and larger injectors.
OVERKILL
$100 Site Donor 2021
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
Originally Posted By: OVERKILL
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
SRT has said their exhaust on the SRT8 can support 600 hp. Obviously they were wrong! It seems to support more like 700.
Almost any modern car is very difficult to get any real improvement with less restrictive exhausts. Many times you just move the torque peak to even higher in the rev range, which can actually make some cars slower than stock.
But the noise...
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
SRT has said their exhaust on the SRT8 can support 600 hp. Obviously they were wrong! It seems to support more like 700.
Almost any modern car is very difficult to get any real improvement with less restrictive exhausts. Many times you just move the torque peak to even higher in the rev range, which can actually make some cars slower than stock.
But the noise...
You would have to make MAJOR mods to need a bigger diameter exhaust than stock. I've known a lot of people who have installed a K&N intake, did their exhaust, and only had 10-15 h.p.. Hardly any justification for going bigger on exhaust. Read this part of this website for the "Little back pressure is good" myth. "Many people mistakenly believe that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this idea would be appealing - as wider pipes have the capability to flow more than narrower pipes. However, this omits the concept of exhaust VELOCITY. Here is an analogy...a garden hose without a spray nozzle on it. If you let the water just run unrestricted out of the hose it flows out limply at a rather slow rate. However, if you take your finger and cover part of the opening, the water will spray out at a much much faster rate.
The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. (see below ) If you have two exhaust pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be travelling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you also want make sure the pipe is wide enough so that there is as LITTLE BACK PRESSURE as possible while maintaining suitable exhaust gas velocity." Here is the website; http://www.gomog.com/allmorgan/exhaustbackpressure.html
The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. (see below ) If you have two exhaust pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be travelling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you also want make sure the pipe is wide enough so that there is as LITTLE BACK PRESSURE as possible while maintaining suitable exhaust gas velocity." Here is the website; http://www.gomog.com/allmorgan/exhaustbackpressure.html
Originally Posted By: SteveSRT8
Originally Posted By: OVERKILL
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
SRT has said their exhaust on the SRT8 can support 600 hp. Obviously they were wrong! It seems to support more like 700.
Almost any modern car is very difficult to get any real improvement with less restrictive exhausts. Many times you just move the torque peak to even higher in the rev range, which can actually make some cars slower than stock.
But the noise...
Yet...a better-flowing exhaust on an SRT8 Magnum was worth noticeable power.
Originally Posted By: OVERKILL
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
SRT has said their exhaust on the SRT8 can support 600 hp. Obviously they were wrong! It seems to support more like 700.
Almost any modern car is very difficult to get any real improvement with less restrictive exhausts. Many times you just move the torque peak to even higher in the rev range, which can actually make some cars slower than stock.
But the noise...
Yet...a better-flowing exhaust on an SRT8 Magnum was worth noticeable power.
gathermewool
Site Donor 2023
If you have cats, the diameter of your cat-back is nearly meaningless. If you're not tuned, you may also be wasting your money. If you want an expensive, possibly cool-sounding noise-maker, then go for it! The bigger the better!
I'm in the bigger is better camp, up to 3-3.5 inches where possible.
Back in the day, I bought into the small diameter primary tube headers magazine writers were championing, with no personal experience of their own.
Now, keeping the heat in and exhaust velocity up is my goal. That is not achieved by reducing pipe size in most cases.
When everything is working well, you can pull some cam duration out of the exhaust side.
Back in the day, I bought into the small diameter primary tube headers magazine writers were championing, with no personal experience of their own.
Now, keeping the heat in and exhaust velocity up is my goal. That is not achieved by reducing pipe size in most cases.
When everything is working well, you can pull some cam duration out of the exhaust side.
OVERKILL
$100 Site Donor 2021
Originally Posted By: Jarlaxle
Originally Posted By: SteveSRT8
Originally Posted By: OVERKILL
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
SRT has said their exhaust on the SRT8 can support 600 hp. Obviously they were wrong! It seems to support more like 700.
Almost any modern car is very difficult to get any real improvement with less restrictive exhausts. Many times you just move the torque peak to even higher in the rev range, which can actually make some cars slower than stock.
But the noise...
Yet...a better-flowing exhaust on an SRT8 Magnum was worth noticeable power.
The Magnum SRT-8 had 2.5" exhaust that necked down to 2.25" in a couple of places. The newer cars have much better exhaust from the factory.
Originally Posted By: SteveSRT8
Originally Posted By: OVERKILL
FWIW, my SRT has 2.75" exhaust, as does the 707HP SRT Hellcat. I believe the exhaust on my former M5 was 2.5" (400HP). Depending on your power level, stock pipe sizing is probably more than adequate.
SRT has said their exhaust on the SRT8 can support 600 hp. Obviously they were wrong! It seems to support more like 700.
Almost any modern car is very difficult to get any real improvement with less restrictive exhausts. Many times you just move the torque peak to even higher in the rev range, which can actually make some cars slower than stock.
But the noise...
Yet...a better-flowing exhaust on an SRT8 Magnum was worth noticeable power.
The Magnum SRT-8 had 2.5" exhaust that necked down to 2.25" in a couple of places. The newer cars have much better exhaust from the factory.
We have a "breakfast club" here locally that meet at a private road and race each other on Sundays. We had a member with a new Charger SRT8 in 08 who had a great running car stock. Then he added a noisy intake and a huge bore exhaust. Totally transformed the car.
After the mods he had a significantly SLOWER ride, big difference in torque. The power was there, but it was moved up in the rev range to a point where you were waiting on it.
Add to that the droning noise from exhaust and the honk from his intake and IMO it was a poor trade off...
After the mods he had a significantly SLOWER ride, big difference in torque. The power was there, but it was moved up in the rev range to a point where you were waiting on it.
Add to that the droning noise from exhaust and the honk from his intake and IMO it was a poor trade off...
In order to get mandrel bent pipes on a custom exhaust system, you can buy pre-bent sections of tubing and pay someone to weld them all. I did that for my 2003 Saturn ION so that I could have a larger resonator and a huge Dynomax Super Turbo muffler. All the mass produced exhaust systems for this car would have been noisy.
I bought a few of these:
https://www.summitracing.com/parts/vpe-2609/overview/
And some straight sections of pipe
Then paid the exhaust guy to cut those pipes to make a perfect mandrel bent system.
I bought a few of these:
https://www.summitracing.com/parts/vpe-2609/overview/
And some straight sections of pipe
Then paid the exhaust guy to cut those pipes to make a perfect mandrel bent system.
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