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Discussion Starter #1
have you replaced the exhaust system on your corvette ?

have you replaced the exhaust system on your c-4 corvette ?
many of you may not be aware that just as the stock TPI intake is restrictive so is the STOCK 2.25"/2.5" exhaust system, IN fact swapping it out for a 3" full length exhaust makes almost all other engine mods work better. with no other changes at all ive seen several corvettes pick up two tenths to a full five tenths in one case in the 1/4 mile by installing full length headers and a full 3" exhaust with free flowing mufflers, all the fancy engine parts in the world won,t help if the engine can,t breath!
while its technically illegal to remove the exhaust , emmision equipment , you can install the larger 3" exhaust anf free flowing cat(S) and an (X) or (Y) pipe as necessary if the old system is rusted out/damaged and by now most C-4 corvettes are pass due!
HERES SOME IDEAS

http://vsholley.vwh.net/HiOctn/ProdLine/Products/ES/ESHHA/SplitFlow.html



http://www.burnsstainless.com/Transitions/transitions.html

http://www.racerpartswholesale.com/flomstr1e.htm


http://www.burnsstainless.com/Crossovers/crossovers.html
 

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Official Forklift Driver
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grumpyvette,

I have one concern regarding my exhaust system that maybe you could address. I have Hedman non-emission headers with the stock front y-pipe slightly modified to fit the headers going into a Catco cat and Dynomax cat back. The question is could the modified front y hurt my performance. I try to tell myself that I don't really see it as a hp killer but a torque gainer. Would a matching diameter front y-pipe help performance greatly or should I not bother with it?


TIA,

John
 

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Discussion Starter #6 (Edited)
let me ask you this, "if opening up the headers at the track normally produces more hp and tq, what makes you think that going from a 3" header collector down to a 2.25" stock (Y) can do anything but RESTRICT exhaust flow?"
to answer your question even more directly, getting a 3" (Y) installed from the header collectors to the cat normally shows a gain in BOTH hp and TQ
look at it this way a 2.25 inch exhaust pipe with 14 ga wall thickness has about 3.8 sq inchs of flow area a 3" has about 6.5 sq" of flow area or about 70% less restriction, (thats per side, but at the (Y) its even less at the point they join, what do you think the results will be at high rpms where the exhaust volume increases a great deal? on my vette there was a very noticable increase in hp and no loss of tq after the swap to a full 3" exhaust!
 

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DC Crew
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Hey Grumpy will true 2.5" dual exhaust like the one offered by MAD show any gains? They offer it in stainless stell for $299 or should I wait and upgrade to 3"?
As always thanks for all the info.
 

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Discussion Starter #8
will true 2.5" dual exhaust like the one offered by MAD show any gains?
yes but why do a half A$$ job, a good muffler install shop can custom build a 3" full length exhaust for less money if you shop around
 

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Discussion Starter #10

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those are some good links to fab somethin up.
Im runnin tpis long tube headers, 3in Y to a high flow cat, out thru flowmaster 3 chamber 50 series mufflers. Im happy with the sound and the performance. (for now)
 

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I have B&B Tri-Flo 3". When I was looking to buy, I compared the B&B to the Borla. They "claim" the same hp/trq increase. Borla is 2.5" and B&B is 3". So how can the hp gain be similar?

I don't think size has to do with hp as much as it has to do with backpressure. More (smaller pipe diameter) backpressure better take of of the line...
Less backpressure (biger pipe) more top end...

The exhaust will make your vette "breath" better and as a result will feel like an hp/trq gain.
Actually the more hp a motor makes, the bigger the exhaust needs to be...wasn't there an HP vs. Pipe Diameter chart I remember reading a while back?
 

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Discussion Starter #16
a good amount of resonance in the exhaust can be canceled with (X) pipe installed close to the header collectors and a REAR (H) before the mufflers plus the cones in the exhaust tips
the CORRECT WAY is to install these, it does not effectively block the flow but does effectively alter the frequency of the resonance, lowering the noise a great deal with effecting the engines power output. on some systems installing one per side works on others it takes both exits with one installed but they do work quite well on most corvettes (they install in the exhaust tip)
http://www.secureperformanceorder.com/dynatechdragstore/vortex.cfm

 

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I compared the B&B to the Borla. They "claim" the same hp/trq increase. Borla is 2.5" and B&B is 3". So how can the hp gain be similar?

Per Corsa's site all cat-back systems result in about the same gains because quickly the cats become the controlling restriction.

I too have the B&B and ear plugs are mandatory for road trips.

Anyone have any before/after comparisons when changing cats only??
 

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Yep, Watson 409 Stainless headers into Corsa Stainless System. Sounds civilised at small throttle openings and rips your ears off (outside) at wide open. What I liked was the bolt on from headers to Corsa, no adapters required. //Dave
 

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3" exhaust

Great info grumpy , Question i have a stock 96 lt1 and am looking to do some Mild mods. A slp cold air intake, an 80mm mass air flow from midamerica, i want to do a True 3" dual exhaust using flowmasters no cats, i live in fla with no emmissions.but the guy at 1 muffler shop said it would make it run either rich or to lean without the O2 sensor.? And what flowmaster mufflers should i use? Any info would be great.
 

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Discussion Starter #20
Great info grumpy , Question i have a stock 96 lt1 and am looking to do some Mild mods. A slp cold air intake, an 80mm mass air flow from midamerica, i want to do a True 3" dual exhaust using flowmasters no cats, i live in fla with no emmissions.but the guy at 1 muffler shop said it would make it run either rich or to lean without the O2 sensor.? And what flowmaster mufflers should i use? Any info would be great.
your 1996 corvette uses (4) O2 sensors, theres one before and one after both cats,in the system, youll need to retain all four O2 sensors or youll throw trouble codes, bungs are easily welded into the exhaust system with or without the cats in the system.
 
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