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View Full Version : Exhaust rasp. opinions and help



55EXX
08-01-2009, 10:10 PM
Who likes the bit of rasp to an exhaust note?

i think it sounds cool in some cases. like a buzzy 4 cyl toy car. i hate the sound of a hollow resonator rasp tho like those cheap cannons on stock exhausts. rasp with balls. deep with some lower notes. like the typical booooooBAAAHH but with rasp with the bahhhh part like its really screaming.

I have rasp in my current exhaust - d series twin cam stock header and cat then 2.25" press bent with only shallow angles to avoid too much pipe squish with 15" hotdog mid mounted and a 8x4x14" rear chambered muffler. the chambered rear gives a very deep note and at about 4500rpm when power kicks in and the rasp emerges. what i want to do is make the system quieter (well quieter at static cruising speeds don't care about heavy on or off throttle) but not lose these sounds characteristics. i want deep sound down low and a bit of rasp over 5k rpm i have got it booked in to get another hotdog put in tuesday but where in the system will be better to put it? straight after the cat/before the other hotdog or just bfore the axle back part. my demo pic black lines current red proposed spot for new resonator

http://img187.imageshack.us/img187/4145/exhaustmb2.png

i have a small understanding of exhaust note tuning but want other peoples educated input not guesses please.

VTECMACHINE
09-01-2009, 01:40 PM
Titanium exhaust is the only way if you want a real good rasp noise. :D

lolwuut
09-01-2009, 04:12 PM
can you explain more about how to get the "raspiness" in teh exhaust?? ie. exhaust tuning

at the moment ive got a 2" press bent exhuast with no centre resonator/hot dog, and a single 8x4x15 at the rear. header back, with stock headers ready to go on my d15 carby.

but people who want the "raspiness" tend to go for two or so resonators. why so?

T-onedc2
09-01-2009, 07:16 PM
I could never drive a raspy sounding car, but a system with no resonators and straight through muffler will achieve it. Adding 1 hotdog resonator will relieve it somewhat.

55EXX
10-01-2009, 07:38 PM
i'm just going to add a resonator in position 2 and see what happens.

the rasp attracts a bit too much attention in addition to the screaming engine and roar of the exhaust already. read somewhere a long time a ago in a car book the resos at the front help knock out the low pitch notes and the rear the higher pitched ones. with the best quieting being a achieved with one in both of these sections. so adding one just after the cat would help keep rasp up but to help rid it one at the rear position 2 would achieve this better. this is what i am now going to do. i might even go both and have a stock sounding ride. this sleeper status has always been appealing but my car is no sleeper power wise ;)

i'm seriously considering both position one and two combined besides a very slight increase in flow resistance/back pressure and subsequent flow velocity any other down sides to this?

car at the moment has a huge gain from 5500 to 7500 rpm will this drop to lower rpm or overall power decrease across the board due to more flow pressure disturbances in mufflers decreasing the actual pumping effect?