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Thread: Rob's New Exhaust

  1. #1
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    Rob's New Exhaust

    Fuel went up tiday by a few cents...

    but being stupid,

    I installed the two mufflers behind the 5.7 LS1 yesterday, which has rendered the car exhaust 'just audible' from outside the car.
    2 x 4-1 cast iron extractors --> 2 x 2.5" pipes with balance pipe --> 2 x resonator-style fibreglass 'mufflers' --> 2 x 2.5" >-- 1 x 3" -> single large resonator --> largish oval factory tailpipe tip.

    Sounds quite good; not much 'crackle' and there's no 'drone'... which afflicts these cars with many aftermarket systems.
    I'm not sure if the factory ECU or some other factor is involved, but it doesn't feel quite so responsive at low throttle/revs as in everyday off-idle acceleration [warm]. It might even be something as arcane as gas flow and combustion at idle without any backpressure to speak of..

    At least it doesn't rattle on startup [factory mufflers after removing the cats].
    And the computer suggests that in everyday travelling on our open roads at 90-105km/hr it uses between 8 and 9 litres/100kms which I THINK is over 30 miles per Imperial gallon. It is averaging 9.4 l/100kms after two drives including acceleration cruising and suburban.

    Maybe an aftermarket chip next, with more aggressive timing at low-med throttle and mid-range revs...?

    Or should I keep the car stock and build the Mini engines in my workshop?

  2. #2
    Senior Member misterdecibel's Avatar
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    Re: Rob's New Exhaust

    I think the Holden is too heavy for a Mini engine.

  3. #3
    Vulture of The Western World Eric's Avatar
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    Re: Rob's New Exhaust

    Quote Originally Posted by robmcg
    Fuel went up tiday by a few cents...

    but being stupid,

    I installed the two mufflers behind the 5.7 LS1 yesterday, which has rendered the car exhaust 'just audible' from outside the car.
    2 x 4-1 cast iron extractors --> 2 x 2.5" pipes with balance pipe --> 2 x resonator-style fibreglass 'mufflers' --> 2 x 2.5" >-- 1 x 3" -> single large resonator --> largish oval factory tailpipe tip.

    Sounds quite good; not much 'crackle' and there's no 'drone'... which afflicts these cars with many aftermarket systems.
    I'm not sure if the factory ECU or some other factor is involved, but it doesn't feel quite so responsive at low throttle/revs as in everyday off-idle acceleration [warm]. It might even be something as arcane as gas flow and combustion at idle without any backpressure to speak of..

    At least it doesn't rattle on startup [factory mufflers after removing the cats].
    And the computer suggests that in everyday travelling on our open roads at 90-105km/hr it uses between 8 and 9 litres/100kms which I THINK is over 30 miles per Imperial gallon. It is averaging 9.4 l/100kms after two drives including acceleration cruising and suburban.

    Maybe an aftermarket chip next, with more aggressive timing at low-med throttle and mid-range revs...?

    Or should I keep the car stock and build the Mini engines in my workshop?
    Maybe this is "just me" - but a car that sounds fast also feels a little bit faster than it would if quieted-down, as you've done. Have you actually timed the acceleration to see whether there's a difference?

    I am in a difficult situation. There isn't a single engine that needs rebuilding (or even a major tune) in my inventory. Nothing mechanical to fiddle with... and I can't paint worth a damn!

  4. #4
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    Re: Rob's New Exhaust

    The car has no cats, a single large rear single resonator [straight through with fibreglass], and the two silencers mounted just above the independent rear have been changed from factory to 'free-flow' with smallish ovals and straight trough with fibreglass.

    It is very low on low-rev back pressure, but makes a low 'moan' or soft 'howl' under load.

    I don't like it nearly as much as my 3.8 thriple carb Jag ran.

  5. #5
    Vulture of The Western World Eric's Avatar
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    Re: Rob's New Exhaust

    Quote Originally Posted by robmcg
    The car has no cats, a single large rear single resonator [straight through with fibreglass], and the two silencers mounted just above the independent rear have been changed from factory to 'free-flow' with smallish ovals and straight trough with fibreglass.

    It is very low on low-rev back pressure, but makes a low 'moan' or soft 'howl' under load.

    I don't like it nearly as much as my 3.8 thriple carb Jag ran.
    Me neither!

    The jag has a very distinctive sound; this is even more true today because you so rarely hear one. Ditto old/out of production engines like my Pontiac 455.

    The GM LS1s sound nice enough; but they are everywhere.

    Did you see the video I posted in "Classics" on that '72 Dodge wagon with the 440?

  6. #6
    Senior Member Kwozzie1's Avatar
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    Re: Rob's New Exhaust

    Quote Originally Posted by robmcg




    At least it doesn't rattle on startup [factory mufflers after removing the cats].

    Or should I keep the car stock and build the Mini engines in my workshop?
    The RSPCA will be after you for having cats live in yer muffler

    I suggest the simplicity of the Mini
    Rex
    On the Sunshine Coast, in the Sunshine State Queensland (QLD), Australia

  7. #7
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    Re: Rob's New Exhaust

    Quote Originally Posted by Kwozzie1

    I suggest the simplicity of the Mini
    Driving V8s is detrimental to the future of the planet, too. Should be a law against it.

  8. #8
    MikeHalloran
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    Re: Rob's New Exhaust

    Quote Originally Posted by Eric

    The GM LS1s sound nice enough; but they are everywhere.
    I don't miss replacing the damn waterpumps, but I do miss the sound of my LT1.

    My LS1 is stronger, and more civilized, but you have to actually listen to hear it.




  9. #9
    Vulture of The Western World Eric's Avatar
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    Re: Rob's New Exhaust

    Quote Originally Posted by MikeHalloran
    Quote Originally Posted by Eric

    The GM LS1s sound nice enough; but they are everywhere.
    I don't miss replacing the damn waterpumps, but I do miss the sound of my LT1.

    My LS1 is stronger, and more civilized, but you have to actually listen to hear it.

    Exactly.

    A new Corvette's mill makes probably 100 horsepower more than the 455 in my Trans-Am; but my Trans-Am sounds so much better! The rumpety-rump idle, the clackety-clack of the variable duration lifters; the audible sound of the double roller timing chain.... ;D ;D

  10. #10
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    Re: Rob's New Exhaust

    Quote Originally Posted by MikeHalloran

    I don't miss replacing the damn waterpumps, but I do miss the sound of my LT1.

    My LS1 is stronger, and more civilized, but you have to actually listen to hear it.
    Allay your fears, Mike, there is a place for irrigation pumps.
    The LS1 firing sequence compared to recent Fords is such that irrigation pumps sound better. The LS-series is not good for sound.

    Today I was mortified to hear that after six years and 65,000 miles my LS1 GM car is making a belt or waterpump or something noise on startup, having been silent two days ago. Also, it had been parked in calm covered carport where spring tweety-birds are about, and bumblebees are inclined to investigate my kitchen..

    In any event, where people actually travel around production is done, here on the Canterbury Plains, the transport of choice on long open two-lanes is mostly practical stuff like Terranos and various anodyne 4WD boxes... no wonder the sports cars come out for 20-mile straights, yet, oddly, they don't.
    Bikes appear in the rear-view the sensible ones pick the best spots to go fast. But I digress, because none of it is remotely close to keeping an Irish Mail on time 6 minutes late at Crewe after signals and late departure, fireman has a brand new engine,
    1959... this was the very best, outshopped from Crewe.. when the driver picked-up on the steaming and the boiler was fresh and he kept putting small water in beyond, came over and yelled in my ear

  11. #11
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    Re: Rob's New Exhaust

    because I was an unkown lad from Kittymaster he yelled ,
    "light fire," as we accelerated from Crewe, and he watched as the light train of only nine carriages was worked up to 80mph and when he reduced the cutoff, even so, at the signals were 'on' he fed the throttle as if he was touching gently something, and by Bangor we were running sweet I could see the fire was good.
    Three weeks later I got my ticket for mainline running.

    It was in light freezing rain when I got my my first 'express' turn.

    A 'King' class had bought eleven cars including full restuarant in the big snow of 1963, incredibly, on time, [video vailable] and it was still sleet and snow, with the odd idea that this was the only way north from London. *I* was on a 'Castle' with a driver with an old GWR driver, who with standing on the backshunt had an easy road to Birmingham ... swore under his breath when he pulled the reversing lever and backed-up and I more-or-less took over.

    You don't want to know, Christmas-New Year 1963.

    I was promoted. Then with all the shiftwork...

  12. #12
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    Re: Rob's New Exhaust

    I'll ignore the train stuff.

    I was outraged to hear a noise when I started my 2001 LS1 sedan 60,000miles factory-maintained.

    I drove the trousers off it and the noise went away. Can this be real? Sounded like a belt or pump.
    What's the best way to deal with it? Sell the POS?

    Oh I ought to mention that is a very nice 'sleeper' with the most genteel way of going fast... almost as much fun as a BMC Mini.


  13. #13
    Vulture of The Western World Eric's Avatar
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    Re: Rob's New Exhaust

    Quote Originally Posted by robmcg
    I'll ignore the train stuff.

    I was outraged to hear a noise when I started my 2001 LS1 sedan 60,000miles factory-maintained.

    I drove the trousers off it and the noise went away. Can this be real? Sounded like a belt or pump.
    What's the best way to deal with it? Sell the POS?

    Oh I ought to mention that is a very nice 'sleeper' with the most genteel way of going fast... almost as much fun as a BMC Mini.

    Rob,

    Check out the right-side-drive Trans Am video I posted in "Car-toons"... thought it might be you!

  14. #14
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    Re: Rob's New Exhaust

    I was expecting to see exhaust pics!!


    Chip H.

    Former owner: 2012 Honda Civic LX, 2006 Honda Ridgeline RTL, 2000 Honda CR-V EX, 2003 MINI Cooper S, 1992 Honda Accord LX, 1999 Mercedes ML-320, 1995 VW Jetta GLX, 1991 Mercury Capri XR2, 1981 Mercury Zephyr, 1975 Chevrolet Impala

  15. #15
    MikeHalloran
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    Re: Rob's New Exhaust

    Quote Originally Posted by robmcg
    I was outraged to hear a noise when I started my 2001 LS1 sedan 60,000miles factory-maintained.

    I drove the trousers off it and the noise went away. Can this be real? Sounded like a belt or pump.
    What's the best way to deal with it? Sell the POS?
    Well, _I_ wouldn't sell the car just because of a transient noise.

    But I would open the bonnet and investigate.

    I know that's not a trivial undertaking to you.


  16. #16
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    Re: Rob's New Exhaust

    Rob's pretty innovative.
    He'll probably have it out on a engine hoist in an afternoon.

    All for a glazed pulley that just needed some wire-brushing and a new belt.
    :-)

    Chip H.

    Former owner: 2012 Honda Civic LX, 2006 Honda Ridgeline RTL, 2000 Honda CR-V EX, 2003 MINI Cooper S, 1992 Honda Accord LX, 1999 Mercedes ML-320, 1995 VW Jetta GLX, 1991 Mercury Capri XR2, 1981 Mercury Zephyr, 1975 Chevrolet Impala

  17. #17
    MikeHalloran
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    Re: Rob's New Exhaust

    Pulleys for poly-v belts may glaze, but I don't think it would make a difference.

    What would make a difference, and is usually the first thing to go, is the spring- loaded belt tensioner, which may have frozen or broken the spring.


  18. #18
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    Re: Rob's New Exhaust

    Quote Originally Posted by MikeHalloran
    Pulleys for poly-v belts may glaze, but I don't think it would make a difference.

    What would make a difference, and is usually the first thing to go, is the spring- loaded belt tensioner, which may have frozen or broken the spring.

    Yes I just took a close look and it's the belt tensioner pulley which is making the noise... cold only.. quiet when hot. Is this repairable? Should I turn the nut on the front to reduce tension temporarily? It's due for an oil change tomorrow regardless [2001 LS1 standard spec 5.7]. Belt tension looks and feels good to the extent a visual/tension check offers. Belt is clean-looking and runs without fuss.

    Thanks for the info.

    As to the new exhaust, there is STILL a slight rattle on startup... I think the double-skin section at the mouth of the factory 4-1 manifolds is a bit loose. It runs very well.
    One thing I've noticed is a fairly lazy 3-4 shift in the 4L60E auto on light-med throttle accelerating. I understand this is tuneable. Otherwise everything is very strong and good. I'd like to find a chip or a way of tuning the thing for slightly more aggressive timing and part throttle response, since WOT number are already good. I tend to drive mostly in closed loop [doesn't everyone except Janel Poller?] and by nature tend not to floor the throttle.. open loop at around 70%+ would be my preference, but I think that is approx how the factory has set mine up [if indeed it IS original factory...] 195kW @ 5,500 rear wheel cutout 6,300.

    Of course an LS2 would be better ... with a 6 speed.
    In a light 2-door...

    but GM don't do things like that .

  19. #19
    MikeHalloran
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    Re: Rob's New Exhaust

    Belt tensioners are not adjustable, and not repairable.

    You just replace them; usually not more than two bolts.

    Snaking a new belt around the pulleys takes more time than replacing the tensioner. If you don't know how old the belt is, or if you know it's older than ~15,000 miles, replace it, too.


  20. #20
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    Re: Rob's New Exhaust

    Thanks Mike.

    Dunno why it's noisy cold not hot, will replace.

    I googled some sites [LS1 belt tensioner] and it gets very tight at high revs!

    It's a chh chhh chhh noise cold doesn't look like slipping. Do you think the tensioner spring maybe or belt or both. It was rather sudden after a normal open road drive. Or does the internal bearing die? Or the spring 'lock'?

    Yours,

    Lucas is easy...

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