Ok so I'm trying to take a few db out of the 202.
it has 2.5" exhaust with 1 straight through muffler at the back with twin pipe outlet (xu1 style muffler, but slightly larger)
As you could imagin it is rather load, I love it but I don't fancy running the gauntlet everytime I drive the thing.
I had a gonzo Spiral muffler put on about halfway down the system and yes it did make the car a whole lot quieter but I may as well be driving a stock V6 commy.... It has completely killed the mid + top end power (from 3,500 onwards).
I'm going to get the exhaust shop to cut it out and just to fit straight through resinator.
questions for everyone.
what do you guy's do to keep a worked 6 resonably quiet?
thanks,
Adam
Spiral Mufflers
Started by
_Inj gtr202_
, Jul 28 2012 08:37 AM
42 replies to this topic
#2
_oldjohnno_
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Posted 28 July 2012 - 09:29 AM
I went through a similar exercise recently with a mild 202 that was inexplicably several tenths slower than it should have been. The trick seems to be in making the engine think that there is nothing downstream of the collector. What worked best for me was an empty chamber or terminator box immediately downstream of the collector, and this was simply a 2-1/2" hotdog with a 4" OD and about 24" long. I cut the ends off it so I could remove the centre tube and the packing, leaving about 2" of the entry tube protruding in. The idea of this was to minimise reversion but to be honest I don't think it really matters and there was never any sign of reversion anyway. The outlet was welded and ground a bit to make a nice radiused exit. You could make the whole thing from scratch using 4" or 5" tube but you need to maintain a nice exit profile and plenty of internal volume. To keep the noise down I used a 2-1/2" turbo thrush at the very end of the side exit pipe. Don't use a straight-thru here, it'll just be noisy and won't make more power. Dynamax turbos flow better than the old Thrush but for a 200 - 250hp 202 its academic. I've been using the Thrushes on street cars for decades and they are pretty quiet with a nice sound. I also run a 1/2" vac-u-pan tube into the tailpipe downstream of the muffler and it provides some degree of suction at any speed or throttle opening, even at idle. Noise-wise it's pretty reasonable, certainly not what you'd call obnoxious.
#3
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Posted 28 July 2012 - 10:42 AM
^ Sounds good to me. The expansion chambers seem to work a treat from what I've seen, the problem you seem to encounter on most old Holdens (when they are as low as I like them to be) is ground clearance.
#4
_oldjohnno_
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Posted 28 July 2012 - 10:59 AM
They don't need to be round in cross-section so if clearance was an issue you'd just make it oval or rectangular. I just like round (if it will fit) because it doesn't have any flat sides to "drum" and eventually crack. But whatever shape you used you'd want to make sure it had a nicely shaped exit.
#5
rodomo
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Posted 28 July 2012 - 11:00 AM
RoDoMo's mega-muff, scroll down to the bottom of the page.
http://www.gmh-toran...t/page__st__525
http://www.gmh-toran...t/page__st__525
Edited by rodomo, 28 July 2012 - 11:02 AM.
#6
_stretchlc_
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Posted 28 July 2012 - 11:15 AM
Whats all this chat about "mega Muffs" and "thrush" then hey??
#7
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Posted 28 July 2012 - 11:21 AM
Whats all this chat about "mega Muffs" and "thrush" then hey??
Dunno. But I'm itching to find out...
Keep in mind that once you get the exhaust working you'll probably find it wants a couple of numbers less jet (or pulse width) for best power.
#8
_Inj gtr202_
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Posted 28 July 2012 - 03:03 PM
Keep in mind that once you get the exhaust working you'll probably find it wants a couple of numbers less jet (or pulse width) for best power.
That did occure to me when I was ringing the neck out of it and getting nowhere fast.
I figured if the muffler was going to cause me to change the tune THAT much then it must be causing one hell of a restriction.
It's booked back in next Sat to swap the spiral with the resinator at no cost.
In my case the exhaust must do a few turns straight after the last collector due to the sway bar and cross member.
Looks like I have a bit of reading to do.... there where a few terms in the above replys which I have no idea what you are talking about. (apart from the megga muffs and thrush)
cheers
Edited by Inj gtr202, 28 July 2012 - 03:04 PM.
#9
_Inj gtr202_
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Posted 29 July 2012 - 09:53 AM
worked it all out except for Vac u pan tube??
what is it for and how does it work?
what is it for and how does it work?
#10
_oldjohnno_
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Posted 29 July 2012 - 10:25 AM
It's just a tube (like a pitot tube) that runs into the exhaust for crankcase ventilation, works a bit like a venturi. Seeing as PCVs never work properly with much cam overlap the vacupan is a simple way of ventilating the bottom end. I just use some 1/2" steel tube into the tailpipe then run some braided teflon hose back to a big separator on one of the sideplates. The stuff that comes in the kits (eg Milodon) is way too big and the supplied filter/separator is hopeless so its better to just make your own. It works really well, even from idle, and you can set it up so that it maintains a bit of vacuum all the time. Stops the dripping from the rear main if nothing else 
. I also run a small orifice instead of a PCV and this is a handy way of fine tuning the amount of transfer slot showing at idle and/or the a/f when cruising on a cracked throttle. It's remarkable how much smoother it will run with small throttle openings compared to a PCV with a bit of cam overlap.
But back to the exhaust. Don't be surprised if the car still runs a bit slower with the resonator in place. They don't behave as you'd expect them to, even the smooth bore ones (though they aren't as bad as the louvred cores). I know you're basically getting the work done for nothing but I'd be really trying hard to get a biggish terminator box fitted around 18" from the last junction and then a proper muffler at the back to keep it quiet. The little sixes can be pretty fussy about the exhaust, and the more cam you run the fussier they seem to be. You could well find that it runs quicker (and more quietly) than it did originally. But again, if you change it keep an eye on the a/f, especially at the top end.
. I also run a small orifice instead of a PCV and this is a handy way of fine tuning the amount of transfer slot showing at idle and/or the a/f when cruising on a cracked throttle. It's remarkable how much smoother it will run with small throttle openings compared to a PCV with a bit of cam overlap.But back to the exhaust. Don't be surprised if the car still runs a bit slower with the resonator in place. They don't behave as you'd expect them to, even the smooth bore ones (though they aren't as bad as the louvred cores). I know you're basically getting the work done for nothing but I'd be really trying hard to get a biggish terminator box fitted around 18" from the last junction and then a proper muffler at the back to keep it quiet. The little sixes can be pretty fussy about the exhaust, and the more cam you run the fussier they seem to be. You could well find that it runs quicker (and more quietly) than it did originally. But again, if you change it keep an eye on the a/f, especially at the top end.
#11
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Posted 29 July 2012 - 03:39 PM
It's just a tube (like a pitot tube) that runs into the exhaust for crankcase ventilation, works a bit like a venturi. Seeing as PCVs never work properly with much cam overlap the vacupan is a simple way of ventilating the bottom end. I just use some 1/2" steel tube into the tailpipe then run some braided teflon hose back to a big separator on one of the sideplates.
Do you run it from there to reduce the amount of oil sucked and burnt?
#12
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Posted 29 July 2012 - 04:32 PM
Do you run it from there to reduce the amount of oil sucked and burnt?
It's good practice to not pull the fumes through the same holes through which the oil is trying to drain back to the sump. So with that in mind the rocker cover is probably the worst place to vent from, the best place being the left side of the sump. The sideplates are OK but not ideal as all the oil from upstairs still has to drain through the holes in the lifter gallery and a fair bit of oil can build up in there. The front plate is a better choice than the rear as it has 3 drain holes compared to only 2 for the rear.
#13
_Inj gtr202_
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Posted 30 July 2012 - 12:20 AM
found some light reading....
http://www.superchev...xh/viewall.html
So the termination box is essentially an open chamber box mounted as close as possible to the last collector to try and let the motor think the exhaust finishes there?
The resonator is going to be put in the first available straight section of pipe after the collector. (just after the cross member) Would hollowing out the res be essentially turning it into a terminator box (although it won't be overly large)?
Starting to think I should have just left it as an obnoxious screamer.
http://www.superchev...xh/viewall.html
So the termination box is essentially an open chamber box mounted as close as possible to the last collector to try and let the motor think the exhaust finishes there?
The resonator is going to be put in the first available straight section of pipe after the collector. (just after the cross member) Would hollowing out the res be essentially turning it into a terminator box (although it won't be overly large)?
Starting to think I should have just left it as an obnoxious screamer.
#14
_Inj gtr202_
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Posted 30 July 2012 - 01:40 AM
Re-read all the reply's..
Hollowing out the Resi is what was described at the top... guess I just understand a little better now.
I'll see if I can get I nice long one put on which is flanged at both ends. That way I can take it off and modify it, (or remove it when I wanna be a propper hoon).
I'll let you know the results.
BTW. I finally took some in car footage of the car being driven.
Is there somewhere I can post it where I won't get in trouble with the boy's in blue?
Hollowing out the Resi is what was described at the top... guess I just understand a little better now.
I'll see if I can get I nice long one put on which is flanged at both ends. That way I can take it off and modify it, (or remove it when I wanna be a propper hoon).
I'll let you know the results.
BTW. I finally took some in car footage of the car being driven.
Is there somewhere I can post it where I won't get in trouble with the boy's in blue?
#15
_oldjohnno_
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Posted 30 July 2012 - 07:33 AM
Try to have about 18" to 24" of pipe between the last collector "Y" piece and the empty resi (technically this short length of pipe is part of the collector). Ideally you'd test at the strip or on a dyno with an open exhaust to find the optimum length but 18" to 24" should work ok. Also make sure the empty resi has enough volume to work - I think 4" x 24" would be around the minumum, so if you can't find a resi at least that big you might have to make it from scratch. But realistically that wouldn't take any longer to do than gutting a hotdog anyway.
#16
orangeLJ
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Posted 30 July 2012 - 09:33 AM
Re-read all the reply's..
Hollowing out the Resi is what was described at the top... guess I just understand a little better now.
I'll see if I can get I nice long one put on which is flanged at both ends. That way I can take it off and modify it, (or remove it when I wanna be a propper hoon).
I'll let you know the results.
BTW. I finally took some in car footage of the car being driven.
Is there somewhere I can post it where I won't get in trouble with the boy's in blue?
In car footage, no plates in view..... could be any torana video....
Make a youtube or photobucket account and throw it up there with no description
#17
_Inj gtr202_
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Posted 30 July 2012 - 01:10 PM
Try to have about 18" to 24" of pipe between the last collector "Y" piece and the empty resi (technically this short length of pipe is part of the collector). Ideally you'd test at the strip or on a dyno with an open exhaust to find the optimum length but 18" to 24" should work ok. Also make sure the empty resi has enough volume to work - I think 4" x 24" would be around the minumum, so if you can't find a resi at least that big you might have to make it from scratch. But realistically that wouldn't take any longer to do than gutting a hotdog anyway.
Cheers,
I'll see how much the exhaust shop is willing to do for me. Damn shame I went and got the Spiral fitted, now I kinda have to get it replaced with something off the shelf from their shop.
live and learn...
I'll have a got at the video, the link will most likely be in the 12 port thread in the fab section.
#18
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Posted 30 July 2012 - 01:46 PM
It's good practice to not pull the fumes through the same holes through which the oil is trying to drain back to the sump. So with that in mind the rocker cover is probably the worst place to vent from, the best place being the left side of the sump. The sideplates are OK but not ideal as all the oil from upstairs still has to drain through the holes in the lifter gallery and a fair bit of oil can build up in there. The front plate is a better choice than the rear as it has 3 drain holes compared to only 2 for the rear.
So this then also has the side benefit of helping the oil return to the sump then?
#19
_oldjohnno_
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Posted 30 July 2012 - 04:44 PM
So this then also has the side benefit of helping the oil return to the sump then?
Yep.
#20
Stinga
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Posted 30 July 2012 - 05:48 PM
what do you use for a separator on the sideplate Johnno? is it something you make yourself or an off the shelf type part?
#21
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Posted 30 July 2012 - 06:56 PM
Its big and ugly but it works... just an exhaust bend. I cut the bend in the middle so when its welded onto the sideplate the straight leg sticks up at about 45* or so. It probably sticks up about 6 or 8" and I perforate the sideplate with holes where it's attached. I used to fill the tube with mesh but found that if its big enough you don't need mesh, just a baffle near the top. I weld a cap on it with a male JIC thread to take the hose. I'm sure you could make something much more elegant that works but meh, I'm past caring about looks...
#22
_Inj gtr202_
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Posted 30 July 2012 - 08:08 PM
exhaust pics....
As you can see chances of fitting anything much larger than 3.5" diam and 13" long are slim to none
As you can see chances of fitting anything much larger than 3.5" diam and 13" long are slim to none
#23
_Inj gtr202_
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Posted 30 July 2012 - 08:13 PM
Its big and ugly but it works... just an exhaust bend. I cut the bend in the middle so when its welded onto the sideplate the straight leg sticks up at about 45* or so. It probably sticks up about 6 or 8" and I perforate the sideplate with holes where it's attached. I used to fill the tube with mesh but found that if its big enough you don't need mesh, just a baffle near the top. I weld a cap on it with a male JIC thread to take the hose. I'm sure you could make something much more elegant that works but meh, I'm past caring about looks...
Are you talking about venting the crank case from the side valve covers or the sump when you are describing the above?.... and yes after a good flogging the rear main seal does weap a little. All that is currently installed is a PCV in the rocker cover with a hose to the inlet Plenum. Guess I'll be adding crank breathing to the list of jobs to do.
Edited by Inj gtr202, 30 July 2012 - 08:15 PM.
#24
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Posted 30 July 2012 - 08:22 PM
In car footage, no plates in view..... could be any torana video....
Make a youtube or photobucket account and throw it up there with no description
Photobucket doesn't seem to like me trying to upload a .mp4??
and I tried youtube and it was goign to take 40 min???
the file is 550MB..
#25
_oldjohnno_
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Posted 30 July 2012 - 08:35 PM
Photobucket doesn't seem to like me trying to upload a .mp4??
and I tried youtube and it was goign to take 40 min???
the file is 550MB..
550mb????? I've got feature length
Might pay to try to reduce it to a lower resolution maybe?
Edited by oldjohnno, 30 July 2012 - 08:35 PM.
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