Masterful exhaust gurus.....I need your help.
- Thread starter Mr-Wolf
- Start date
julian.allard66
Been Around the Block
Yes to both questions, yes you can cut it down and yes it'll run like a bag of shite afterwards.
Tune-A-Fish
BOTM LOSER Proudly Deplorable
BS... Cut it fuckin Mack knows fuck all how it performs in the first place
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Tune-A-Fish
BOTM LOSER Proudly Deplorable
jimmer said:
Where are you getting this from? If he was whacking the head pipes to collector maybe that would not be good, the only reason Mack has 10 inches of mid pipe is to fit the stock layout of some sort... He might want to do some research when shortening the can but a seriously doubt the best dyno in the land would detect this whack job
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OK, so let's start with what we know and what we don't know.
Are any of us experts on that pipe and have any of us done any serious R&D on that particular pipe? That's probably a solid NO. So wer are dealing with what we believe to be a probable outcome and that's OK too. We know that typically a collector needs a merge section or mid pipe to stabilize flow and pulses, so chopping off all or most of a mid pipe is likely to hurt performance in some way.
Replacing a can is a simpler issue. The probability that the stock MAC can is dyno tuned and perfect for all engine applications is about the same as my odds of winning the lottery when I don't buy a ticket, but the probability of our new can being any more suited is about the same. We might get lucky. And then again, we might not.
Few of us use all the stock performance and even fewer of us can tell an actual improvement from a hole in the road or in a powerband, so if you like what you want to try, go ahead and give it a go. That pipe is steel and easy to weld bits back on if we don't like the results of our experiments.
Many pipe experiments result in more noise or a dip before it comes on the pipe and both can make a bike feel more powerful even when it's making less power than before. We call it character.
You could measure all the header lengths and work out what length you want them to be and then fabricate a suitable merge collector and transition and appropriate mid and tail pipes and so on, but you may end up having to make a few to test before you get one that really improves performance. For a street bike, go for it, just try to keep it quiet please.
Are any of us experts on that pipe and have any of us done any serious R&D on that particular pipe? That's probably a solid NO. So wer are dealing with what we believe to be a probable outcome and that's OK too. We know that typically a collector needs a merge section or mid pipe to stabilize flow and pulses, so chopping off all or most of a mid pipe is likely to hurt performance in some way.
Replacing a can is a simpler issue. The probability that the stock MAC can is dyno tuned and perfect for all engine applications is about the same as my odds of winning the lottery when I don't buy a ticket, but the probability of our new can being any more suited is about the same. We might get lucky. And then again, we might not.
Few of us use all the stock performance and even fewer of us can tell an actual improvement from a hole in the road or in a powerband, so if you like what you want to try, go ahead and give it a go. That pipe is steel and easy to weld bits back on if we don't like the results of our experiments.
Many pipe experiments result in more noise or a dip before it comes on the pipe and both can make a bike feel more powerful even when it's making less power than before. We call it character.
You could measure all the header lengths and work out what length you want them to be and then fabricate a suitable merge collector and transition and appropriate mid and tail pipes and so on, but you may end up having to make a few to test before you get one that really improves performance. For a street bike, go for it, just try to keep it quiet please.
Mr-Wolf
Been Around the Block
Really I just don't like the up and out jog in the mid pipe. So Taking into account all you guys have said, I think I will cut it just past the bend and leave around 6" of mid pipe. I'm not ditching the muffler, I'm not that guy (nothing against those guys, I just like a low growl not a loud bang), I plan on welding a cone onto the end of the muffler though.....
Seriously though, you guys are awesome. Thank you.
Question not related to this, but do I need to replace my head gasket if I remove my head? The gasket is like a month old and only 30mi on it...
Seriously though, you guys are awesome. Thank you.
Question not related to this, but do I need to replace my head gasket if I remove my head? The gasket is like a month old and only 30mi on it...
Tune-A-Fish
BOTM LOSER Proudly Deplorable
Meh... Standing next to all the techs listening to the jargon won't make you a scientist.
Nope im no guru cept maybe Bewbers, I have a PHD in Boobs and motorboating... This is no high tech race machine and no guru exists outside of maybe Terry Vance and Mr Yoshimura himself... everyone else pretty much relies on proven theory and testing... I have made exhaust for a few bikes and chopped a hell of a lot more and i will personally grantee the thing won't move the needle after that section is cut out... get it tuned with the section in then get the before after dyno runs and if it decreased perf Ill buy you a new header. Your chain and tire choice are likely robbing you more than that pipe modified ever will
Nope im no guru cept maybe Bewbers, I have a PHD in Boobs and motorboating... This is no high tech race machine and no guru exists outside of maybe Terry Vance and Mr Yoshimura himself... everyone else pretty much relies on proven theory and testing... I have made exhaust for a few bikes and chopped a hell of a lot more and i will personally grantee the thing won't move the needle after that section is cut out... get it tuned with the section in then get the before after dyno runs and if it decreased perf Ill buy you a new header. Your chain and tire choice are likely robbing you more than that pipe modified ever will
Mr-Wolf
Been Around the Block
Tune-A-Fish said:Meh... Standing next to all the techs listening to the jargon won't make you a scientist.
Nope im no guru cept maybe Bewbers, I have a PHD in Boobs and motorboating... This is no high tech race machine and no guru exists outside of maybe Terry Vance and Mr Yoshimura himself... everyone else pretty much relies on proven theory and testing... I have made exhaust for a few bikes and chopped a hell of a lot more and i will personally grantee the thing won't move the needle after that section is cut out... get it tuned with the section in then get the before after dyno runs and if it decreased perf Ill buy you a new header. Your chain and tire choice are likely robbing you more than that pipe modified ever will
Not even close to a race machine.....currently it's a no top end machine for the second time due to oil leak after rebuild.
Tune-A-Fish
BOTM LOSER Proudly Deplorable
Yeah I seen that Did the gasket fail or are you looking for some warpage?
Did the gasket fail or are you looking for some warpage?
Mr-Wolf
Been Around the Block
Tune-A-Fish said:Yeah I seen that
Hard to say, the base gasket was really hard to read. it was split at the back, but I'm not 100%sure I didn't do that while removing it. With everything being torqued properly I can only assume gasket failure............that's the cheap plan, take the gasket off cut my own gasket specifically for this bike from high quality and free material and put it back together and see what happens.
If the base gasket is ~1/64 thick should I get a gasket that is around ~1/32nd thick just to help or stay with stock size?
julian.allard66
Been Around the Block
Generally if you shorten the exhaust you lose mid range power, it won't make a massive difference to the top end power.
I know squiddly diddly about Mac exhausts but I doubt if it's been any where near a dyno.
I know squiddly diddly about Mac exhausts but I doubt if it's been any where near a dyno.
lostboy
Active Member
Tune-A-Fish said:Meh... Standing next to all the techs listening to the jargon won't make you a scientist.
Nope im no guru cept maybe Bewbers, I have a PHD in Boobs and motorboating... This is no high tech race machine and no guru exists outside of maybe Terry Vance and Mr Yoshimura himself... everyone else pretty much relies on proven theory and testing... I have made exhaust for a few bikes and chopped a hell of a lot more and i will personally grantee the thing won't move the needle after that section is cut out... get it tuned with the section in then get the before after dyno runs and if it decreased perf Ill buy you a new header. Your chain and tire choice are likely robbing you more than that pipe modified ever will
Exactly. We're talking old 4 stroke, there's probably less science in that pipe setup than in a Briggs engine.
Tune-A-Fish
BOTM LOSER Proudly Deplorable
hillsy said:
Now that is useful feedback... gonna have to cut the thing twice to save the kink and weld or have it welded back in. I would cut it so the weld will be all the way up to the collector just back a 1/4in... crank the welder up on high with fast wire feed, practice the weld several times on the scrap so you can weld half or more of a 360 without stopping, I have to hold the gun upright and use my thumb on the trigger... Or if you have a tig welder, then hell take all the time you want :
Mr-Wolf
Been Around the Block
hillsy said:
In my defense they are brand new and came with the bike... nothing I would purchase.
Tune-A-Fish said:Now that is useful feedback... gonna have to cut the thing twice to save the kink and weld or have it welded back in. I would cut it so the weld will be all the way up to the collector just back a 1/4in... crank the welder up on high with fast wire feed, practice the weld several times on the scrap so you can weld half or more of a 360 without stopping, I have to hold the gun upright and use my thumb on the trigger... Or if you have a tig welder, then hell take all the time you want :
Damn, I didn't think about that. I cant take the muffler off and see if it will fit till I get the top end back together later this week. Maybe the plan should be cut off and reduce the angle of the kink a bit, then cut off some mid pipe and re-weld the kink back on and the most upright angle I can get without hitting anything.
So side question. Can I double up the thickness of my base gasket or will that cause problems?
Mr-Wolf said:
It will probably mess with your cam timing as it will lift the head up a tad and the cam chain links will not correspond. You might get lucky and it's exactly one link out....or else you'll need to slot the cam sprocket and time it manually.
Anyway, why the double gasket?
