Corsa Indy H-Pipe Fix vs. X-Pipe for C5
ADB
loose the motorboat idle and full throttle acceleration/deceleration popping
and harshness without installing an X-Pipe, then this might be of interest.
I was on the fence for a long time whether to install an X-Pipe to try and
mellow out the sound the Corsa Indy exhaust system on my '99 C5. When I
originally installed the exhaust system and heard the idle I thought it was
OK but not great. Even though Corsa does extensive boat applications my
exhaust is on a GM smallblock car and should sound like it. At the other end
of the rev scale, I was not too crazy about the harshness and quantity of
the popping during heavy deceleration, though I had no problem with the
volume after I got used to it compared to the stock exhaust. After reading
numerous posts concerning the exhaust note and X-Pipe solution, I decided to
I needed try something. Since I like to keep my modifications as bolt-on and
reversible as possible and I personally do not believe that the X-Pipe will
increase HP, welding on an X-Pipe was a last resort, but that is just my
personal preference.
I decided to call Corsa and see what their take on the matter was. They were
very aware of the concerns about the sound of their Indy exhaust system.
Corsa said the problem stemmed from the GM H-Pipe having very small holes in
the exhaust pipes inside the H-Pipe. The H-Pipe is 2 ½ inches in diameter
while the holes drilled into the exhaust pipes at each end of the H-Pipe are
well under an inch in diameter. This does not allow sufficient pressure
equalization, thus the system does not sound as it was originally designed.
Corsa used a '97 C5 as it's test vehicle and did not have the motorboat idle
or popping at high RPM problems. Evidently the 97 had larger openings.
Anyway, the Corsa solution would be to cut the H-Pipe in the center and
drill out the holes in the exhaust tubes to the full 2 ½ inch diameter of
the H-Pipe. Corsa has wanted to try the fix for a while, but their car is on
the road for shows and hasn't been in the shop long enough to try the H-Pipe
modification. Their idea was that the X-Pipe works so the enlarged H-Pipe
should also. After talking for a while longer, I decided I would give it a
try. I figured the labor would be about the same as installing an X-Pipe and
would save me the price of an X-Pipe so I took the gamble. I am glad I did
it worked beautifully. Installation still looks stock, only a small weld
around the center of the H-Pipe and small welds on the brackets to give it
away.
The idle is a little more throaty with only a slight blurble, but doesn't
sound like a wet stack inboard boat. It still pops infrequently, but IMO
that is unavoidable due to the lean nature of the LS-1. It does not sound as
if I lit a string of firecrackers every time I decelerate as it did prior to
the mod. Overall it just sounds great. More throaty, less harsh, it seems as
if the high-end revs are at a lower frequency, not quieter, just better and
smoother sounding, hard to describe exactly. At cruising speeds the sound is
still great, no resonance at RPMs in the 1500 - 2500 range.
I am glad I took the chance and tried the H-Pipe mod. This is the exhaust
note I was looking for when I purchased the system last summer and now I
finally have it. Not to mention saving the cost of an X-Pipe.
It would be interesting to hear 3 C5s with Corsa Indys next to each other
for comparison. One with a modified H-Pipe, one with an X-Pipe installed and
one with only the stock intermediate pipe. I would bet the H-Pipe mod and
X-Pipe cars would sound the same and to my ears much better than the stock
intermediate pipe version, YMMV.
Sorry for the long post, but hopefully it gives an alternative solution to
the situation.
-Alan
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Change "mapson" to "bellsouth" to reply
C5Phil
I know a guy that works as a welder who did the same thing. I don't know
where he found out about the hole size, wonder what the 97 vs 98 vs... are
anyway? He put down a bead at the inside of the crossover pipe then cut out
the center with the torch then ground it down pretty smooth he said. His
comments were almost identical to yours on the Corsa improvement in sound,
don't know which set he had. Sounds like a good bang for the buck. I'm to
give him a call tomorrow and see what he thinks a muffler shop would charge
to do it. A cut, a couple of burn outs, a little welding, might be a real
cheap fix for the the guys that are a bit unhappy with their Corsa sound.
regards,
C5Phil
Chris Faucher
same way about the popping sounds. It just doesn't sounds right on a vette. So
maybe ill try the same with respect with the H-pipe. Ill let you know how it
turned out....as soon as i get my rear lower control arm replaced (the mechanic
noticed it was cracked wide open at the pivot point when he was installing my
exhaust).
--Fauch