DIY Exhaust Mod – Gain of 10+ HP!!!

[edc]

Great comparison video chipmunk. The sound at idle and at lower revs is noticeable but there seems to be little difference at wider throttle openings and higher revs. Of course there is no load. Do you notice much difference when in the road at higher revs and wider throttle opening?

[JAAY]

Now someone needs to get the angle and get 2 1" holes (25mm) in that middle pipe. If my car wasn't behind 2 ft. of snow I would do it.

[jdlmodelt]

Originally Posted by JAAY

Now someone needs to get the angle and get 2 1" holes (25mm) in that middle pipe. If my car wasn't behind 2 ft. of snow I would do it.

I just drilled 3/8 holes in my tail pipe and couldn't tell the difference. My factory exhaust has always sounded like a Honda Civic from the driver's seat. Are my CATs plugged?

[chipmunk]

3/8 will be fairly quiet, however you should hear it when you start and at idle. You need to go a bit bigger to get an overall increase in sound. Just be careful going too big. Read the previous reports that I have given regarding the drone you may get at 1".

[chipmunk]

Originally Posted by edc

Great comparison video chipmunk. The sound at idle and at lower revs is noticeable but there seems to be little difference at wider throttle openings and higher revs. Of course there is no load. Do you notice much difference when in the road at higher revs and wider throttle opening?

I took my car down the motorway this morning to give it a proper test at different engine speeds and load conditions. The best way I can describe it is it's like a tame lion. It roars but doesn't necessarily follow through. When I had the Toyosports exhaust on I got a spine tingling racing car roar whenever I took the revs over 5000 rpm. You don't get that with this mod - you get the same type sound but in a much more subdued form. In fact I would describe my exhaust now as how I would expect a sports car exhaust to sound as standard - throaty but within acceptable norms.

What I will say is that there is a significant difference between 15mm and 25mm. At 15mm it's a bit raspy and you don't notice much difference except at idle. At 25mm it's much deeper (more like the sound of the SS free-flow systems) and has a nice purr to it at low and middle ranges, with just enough at high revs to let you know it's there.

Interestingly, while there is no resonance as such, there is a definite peak in sound volume in the car at 2800rpm. I have a feeling that if you went bigger than 25mm holes that you might end up back with the resonance issue, without the performance benefits of the free-flow system. This makes me wonder whether the resonance is more related to intensity of sound causing the car to vibrate, rather than the design of the exhaust - I'd be interested to hear whether anyone that has fitted one of the more expensive performance exhausts also has the resonance problem. My advise therefore to anyone thinking of trying this mod is - go to a max of 1 inch / 25mm. Bigger than that and you may regret it.

[chipmunk]

Update on my last post. I took my car for a long drive on Sunday and unfortunately, when under load on a slow incline, there is a drone. Certainly not as extreme as with the performance exhaust however a drone none the less.

My advice to anyone that is planning on doing this mod is stop at 15mm - possibly go to 18 or 20mm but 25mm is maybe too far.

Unfortunately in my enthusiasm I went from 15mm to 25mm without road testing so I can't say whether a middle point might have been better. What I can say is that I am now about to change my exhaust for the third time. Anyone passing through Kent this weekend is welcome to stop by and offer their moral support

[JAAY]

Really? Drone? What other exhausts have you had on the car? I have had many and yes there is a tone/sound (you can hear the exhaust) but not drone. I'm just curious as to what you are comparing it too.

[chipmunk]

well - I'm certainly not any expert on exhausts however my comparison is the Toyosport stainless system that I had on before. Currently, the exhaust sound is fine but at 2500 to 2800 it becomes more acute - what I would call a low grade drone. When the holes were 15mm this was hardly noticeable however now I have taken them to 25mm is has become annoying. Certainly not extreme like before however I guess it depends how fussy you are It may also vary between different cars / engines / models / etc.