Rear crossover?

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May 5, 2004 | 07:48 AM

ben73

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From: Oz

Rear crossover?

I know topics on resonance come up on nearly a daily basis :yesnod:
I have read thru most and haven't really found a situation exactly like mine....
I have headers, no cat, dual 2.5" mandrel bent system with an x-pipe just behind the transmission pan and straight thru mufflers almost exactly like the dynomax ultraflo in construction....
Like lots of other guys, it resonates badly at ~1500-2200rpm....
Has anyone had a similar setup and tried a rear crossover just before the mufflers, even tho there is already an x-pipe in the front 1/2 of the system?
Is this worth trying to reduce the resonance??
Has anyone with a front x/h pipe also put one in the rear to control resonance?
Thanks,Ben.

May 5, 2004 | 08:30 PM

ben73

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From: Oz

Re: Rear crossover? (ben73)

ttt, anyone got any thoughts on this?

May 5, 2004 | 10:43 PM

rsafier

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From: OH

Re: Rear crossover? (ben73)

I tried a cross-over Y-pipe on my 85, found it really didn't help that much, resonates at 1100rpm-1600rpm so really just lowered the range.

May 6, 2004 | 01:19 AM

ben73

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From: Oz

Re: Rear crossover? (rsafier)

If I could shift my resonance to occur under 1600rpm I would be happy with that!
Do you also have a front X or crossover?
Ben.

May 6, 2004 | 01:25 AM

BAM92

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From: Houston Texas

Re: Rear crossover? (ben73)

Some say going with longer tail pipes that extend beyond bumper helps.

May 10, 2004 | 11:36 AM

nonetooclose

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From: Lompoc CA

Re: Rear crossover? (ben73)

Quote:

I believe that you are still feeling resonsance due to the fact of the X pipe right at where the typical connection between the two pipes are for the vette. I will have to double check, but I think that you should double your resonance frequency (RPM) if you cut the length of individual pipe length in half. Think of each pipe generically as a string attached at one end to the wall. The longer the string, the larger the waves and the lower the frequency you can make. By shortening the effective individual pipe lengths you increase that frequency hopefully beyond normal driving conditions.

Thanks
Richard

May 10, 2004 | 02:57 PM

McShagger

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From: Orange County California

Re: Rear crossover? (nonetooclose)

I seriously do not think it will help at all. Your best bet is to replace what you have. Ive been following all this resonance stuff too and the consensus is that it is not really fixable. And thats the truth. Lots of people think or hope there is a solution, but the fact is there is none. Ive done a lot to try to fix it (even the crossover Y-pipe) and its still there. I would say the thing that worked the best was replacing the resonator with an X-pipe. This cut it down significantly, but I did not put the X-pipe on to try to reduce resonance. I put it on to solve low end torque deficiency, which it did.

May 10, 2004 | 04:54 PM

ben73

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From: Oz

Re: Rear crossover? (McShagger)

Today I installed a pair of 2-1/2" 'hotdog' type resonators in the rear, just before the diff. It has mellowed the note and the resonance quite a bit. The resonance still does exist, but not nearly as bad as before.
I still might try a rear crossover also.