• Will opening up an exhaust cause power loss?
  • Will opening up an exhaust cause power loss?
  • Will opening up an exhaust cause power loss?
  • Will opening up an exhaust cause power loss?

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  1. #31
    Will opening up an exhaust cause power loss? TedC's Avatar
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    This is always an interesting debate. When researching dyno shops in my area, I was surprised how many cars are messed up by their owners who think bigger exhausts are always better. Specific to a stock L98, an ECM reprogram is required if you open up the exhaust too much. At WOT the L98 goes into a power mode and depends mostly on preset calibrations. Dropping the rear y-pipe and mufflers caused a lean condition on my 1989 when measured using an attached diagnostic tool. On my 1988, just installing muffler eliminators caused a lean condition. Here is quote that closely matches what my local dyno shop has been sharing with me.

    "High velocities, that don't incur pumping losses are the rule!!! Just changing backpressure is a bogus way of trying to create the "ideal" pressure in the system. The exhaust system should work like a correctly conceived header. It should extract the exhaust from the header, to minimize pumping pressures. The only way to create a system that will serve as an extractor is to properly size the tubing to allow the flow velocity to create a sort of "vacuum" behind it. Just as with headers, creating a system that will provide the best of all worlds at all throttle positions and rpm ranges is impossible. It's all going to be a trade-off. You can tune for the throttle positions and rpm ranges where you desire the greatest performance, but you'll sacrifice performance at the other end of the rpm range."

  2. #32
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    the above is a very well put statement . do your homework before you change things and you will only spend money once

  3. #33
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    Here is what I did on the 90, a stock L98.

    1. bought a chip ( to offset any problems with the ECM)
    2. removed the entire exhaust system( It had Noise Masters and an after market Y pipe, the pre cats had been removed the repair leaked and looked like crap).

    Bought a true duall sytem with an H pipe, then I replaced the mufflers with the stock type.

    Runs great.


    Some of you may not be able to do this because of State inspections.

  4. #34
    Member 84Turbo's Avatar
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    Quote Originally Posted by jonszr1 View Post
    both systems are true duals. we didnt put any sensors in either systems . to us the proof is in the et and mph reductions. Proof, not really. ET and MPH doesn't tell you anything about what actually was happening in the exhaust system. One system was certainly more efficient than the other, but the reason why still needs to be explained. the mph is the real key sometimes the sience gets in the way of what is the reality of the deal to go faster from point a to b . I disagree. I think science keeps you from wasting time following after old wives' tales that get passed down over the years. which is what we are after . the money to install sensors for4 the results you seek costs about 10-12 k ???? and just not worth it unless we were trying to develope a system for sale which we are not . just some good friends who have been building exhausts for many years sharing their knowledge to help me out . bottem line it worked very well in my opinion .choose carefully or you will be spending money again to achieve the results you want
    Your 2.5 inch system is not a true dual as most people define them. Your X pipe causes the exhaust from one bank to traverse both pipes. It does not stay on the same side as the engine bank it originated from. True duals, as most guys describe them, would restrict the odd number cylinders to the left exhaust pipe, and the even number cylinders to the right exhaust, with no "cross talk". An X pipe increases the downstream pipe volume seen by the exhaust flow. An increase in pipe volume will reduce the backpressure/restriction that the outgoing gas (from the cylinder) sees.
    The sensors to do this test cost about 25 dollars. I mentioned earlier that you haven't posted any data regarding the backpressure that you insist is necessary. It's strictly anecdotal data you've supplied. A low pressure gauge (0-5 psig) plumbed into each bank will tell you which exhaust system is causing less restriction to the exhaust flow.

  5. #35
    Will opening up an exhaust cause power loss? TedC's Avatar
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    When I owned my 1988 vette with 50K on it, I tried several different cat back systems. The stock GM exhaust on an auto 1988 with 2.59 had only one working muffler tip per side. Using an adapter that plugs first into the O2 port, we were able to take back pressure readings. At shift points, the stock setup reading was ~6 PSI. No catback, it dropped to ~3 PSI. Muffler eliminators ~4 PSI, Dynomax ~4 PSI, and GM stock muffler with 3.08 (all tips open) ~4 PSI. The L98 is rated 5 more HP by GM when using the 3.08 axle because of the 4 open tips. The ECM was showing lean conditions when using no catback and with muffler eliminators. I loved the sound of the Dynomax, but the interior noise was really bad, even using a balanced y-pipe. Balance y-pipe did not change PSIs. The conclusion I made (maybe wrong) was that the converters had to go if I required a PSI better than the 3-4 PSI. A reprogramed chip would also be required.

  6. #36
    New Member rickreeves1's Avatar
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    Quote Originally Posted by jonszr1 View Post
    all i was doing was offering to share the experiences of 35 years of drag racing and building hot rods. believe what you want . if you do some homework on the subject you will find what i am telling you is true .


    Quote Originally Posted by jonszr1 View Post
    you will lose power if you take away all the back pressure .
    This statement is spreading false information.

    Quote Originally Posted by jonszr1 View Post
    they shared that too big a pipe causes the exhaust to lose velocity.
    This one makes more sense.


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  7. #37
    Member JimBobC4's Avatar
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    i've been reading this thread since it started and wanted make one point

    I think it depends on how you define the word "power"

    are we talking horse power ?

    or torque in this thread?

  8. #38
    Member 84Turbo's Avatar
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    Quote Originally Posted by JimBobC4 View Post
    i've been reading this thread since it started and wanted make one point

    I think it depends on how you define the word "power"

    are we talking horse power ?

    or torque in this thread?
    Doesn't matter. Cylinder pressure makes torque. And you can't make horsepower without torque.

  9. #39
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    Cut outs are junk, and a waste of MY time. I have manual cut outs on my 76 Vette, I disconnect them to impress my friends in my driveway and I would never drive with them like that! On my 92 vette, I have no mufflers, and I can't hear while on a cell phone, not to mention it's loud all the time.

    I recommend to pick a situation:

    1.) Loud Sound
    2.) Mild Sound
    3.) Quiet Sound

    If I heard a C4 come up next to my 92 at a red light, and I heard them hit a cut out switch my GF and I would point at you and hope you also had a spoiler/wing installed.....

  10. #40
    Member ZumZum's Avatar
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    Quote Originally Posted by 92BlackVette View Post
    Cut outs are junk, and a waste of MY time. I have manual cut outs on my 76 Vette, I disconnect them to impress my friends in my driveway and I would never drive with them like that! On my 92 vette, I have no mufflers, and I can't hear while on a cell phone, not to mention it's loud all the time.

    I recommend to pick a situation:

    1.) Loud Sound
    2.) Mild Sound
    3.) Quiet Sound

    If I heard a C4 come up next to my 92 at a red light, and I heard them hit a cut out switch my GF and I would point at you and hope you also had a spoiler/wing installed.....

    Cutouts are really mainly for the weekend racer. If you drive your car to the track it's a helluva lot easier to open up the cutouts then to unbolt and drop the exhaust.

  11. #41
    New Member rickreeves1's Avatar
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    Quote Originally Posted by 92BlackVette View Post
    Cut outs are junk, and a waste of MY time. I have manual cut outs on my 76 Vette, I disconnect them to impress my friends in my driveway and I would never drive with them like that!
    Impressing friends with exhaust? Do you have a big wing to go with that?



    Some people are waxers and some like to go fast. It's not always about the sound or looks. IMO

  12. #42
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    Nooooo! No big wing, no wing at all!!!!
    All I want is to have the car sound louder and good on demand. It is my daily driver to school and I want to make it quiet when I need it quiet.I dont race, but I want to keep the same performance or make it a little better. An exhaust system is going to cost at least $800 if I get a good one while cutouts cost $300. I was just asking for suggestions bc for a college student $300 is a lot and might be next weeks gas money!

  13. #43
    Member 92BlackVette's Avatar
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    I am a college student too, and I drive my no-cell-phone-hearing-no-muffler-daily-driver every day. I recommend to do it right or don't do it at all. By the way unless you are driving a C5-R there shouldn't be a wing installed on a Corvette. I am anti-Greenwood Aero Kits too. <--Correction

  14. #44
    Member 84Turbo's Avatar
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    Quote Originally Posted by 92BlackVette View Post
    I am a college student too, and I drive my no-cell-phone-hearing-no-muffler-daily-driver every day. I recommend to do it right or don't do it at all. By the way unless you are driving a C5-R there shouldn't be a wing installed on a Corvette. I am anti-Greenwood too.

    If you knew anything about Corvettes, you wouldn't say something that silly.

  15. #45
    Member nickyg's Avatar
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    Quote Originally Posted by dogfish246 View Post
    Nooooo! No big wing, no wing at all!!!!
    All I want is to have the car sound louder and good on demand. It is my daily driver to school and I want to make it quiet when I need it quiet.I dont race, but I want to keep the same performance or make it a little better. An exhaust system is going to cost at least $800 if I get a good one while cutouts cost $300. I was just asking for suggestions bc for a college student $300 is a lot and might be next weeks gas money!
    Hey dogdish, I got chambered muffler eliminators and they sound great. Especially if I get on it. The best part is that I fly through state inspection with no problems or questions.

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