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Spiral Mufflers

Started by _Inj gtr202_ , Jul 28 2012 08:37 AM

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42 replies to this topic

#26 _oldjohnno_

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Posted 30 July 2012 - 08:43 PM

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.

A side cover. A PCV won't know what it's supposed to be doing with a bit of cam overlap at cruise, so a good vent with a fixed orifice can make light throttle cruising smoother. Won't make any more power though...

BTW Adam I'm sure with your proven fabrication skills you can squeeze some sort of hi volume box in there. The shape doesn't matter and the entry and exit pipes dont have to be centred or in line. You can do it.

Edited by oldjohnno, 30 July 2012 - 08:46 PM.

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#27 warrenm

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Posted 31 July 2012 - 08:07 AM

exhaust pics....

As you can see chances of fitting anything much larger than 3.5" diam and 13" long are slim to none

Maybe something with a shape like an oval muffler, like Rodomo used.

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#28 _Ned Loh_

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Posted 31 July 2012 - 08:22 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.

Oldjohnno, are you sure the rest of the exhaust wasn't holding it back or effecting it (both in terms of flow and/or design)? I also wonder if the hotdog in gtr202's pictures was back just before the diff there might be less issues? At the upper end of the 200-250hp you mention I think you need some pretty reasonable flow not to hold it back. Any ideas on what the Thrush flows? GTR202 any ideas on what the hotdog and muffler flow?

I must admit that someone I trust did mention good results from a 'terminator box' to me about 10 years ago but something I've never got around to trying. I see the word expansion chamber being used above, but also you mention leaving some pipe to stop reversion. Just so we are clear, are we talking about tuning using the wave dynamcis (like two stroke exhausts), or using the abrupt change so the engine effectively thinks it has reached atmosphere (not that there wouldn't be wave dynamics going on but your not trying to use them in the way you do in a two stroke expansion chamber)?

Edited by Ned Loh, 31 July 2012 - 08:32 AM.

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#29 _Ned Loh_

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Posted 31 July 2012 - 08:28 AM

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?

At the risk of sounding like a nana, join a car club and get off the street. Careful though, it can be addictive.

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#30 _Inj gtr202_

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Posted 31 July 2012 - 08:40 AM

550mb????? I've got feature length ~~pornos~~ Christian Inspirational movies smaller than that....

Might pay to try to reduce it to a lower resolution maybe?

still new to the video game. I'll see what I can do

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#31 _Inj gtr202_

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Posted 31 July 2012 - 08:47 AM

At the risk of sounding like a nana, join a car club and get off the street. Careful though, it can be addictive.

Yeah most of the heavy driving gets done at Mallala.
The video mainly shows light cruising, acceleration in 4th from 1,200 RPM to 3,500.
2nd and 3rd gear flat out from 50km/h to about 120.
and flat in first and second.

no "hooning" as a such

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#32 _Ned Loh_

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Posted 31 July 2012 - 10:30 AM

Cool.

WOT from 1,200RPM - Nice.

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#33 _oldjohnno_

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Posted 31 July 2012 - 11:55 AM

Oldjohnno, are you sure the rest of the exhaust wasn't holding it back or effecting it (both in terms of flow and/or design)? I also wonder if the hotdog in gtr202's pictures was back just before the diff there might be less issues? At the upper end of the 200-250hp you mention I think you need some pretty reasonable flow not to hold it back. Any ideas on what the Thrush flows? GTR202 any ideas on what the hotdog and muffler flow?

I must admit that someone I trust did mention good results from a 'terminator box' to me about 10 years ago but something I've never got around to trying. I see the word expansion chamber being used above, but also you mention leaving some pipe to stop reversion. Just so we are clear, are we talking about tuning using the wave dynamcis (like two stroke exhausts), or using the abrupt change so the engine effectively thinks it has reached atmosphere (not that there wouldn't be wave dynamics going on but your not trying to use them in the way you do in a two stroke expansion chamber)?

Ned, I'm sure the rest of the system wasn't too much of a problem because the only thing I changed was gutting the resi, everything else stayed the same. It immediately picked up 3 or 4 mph and wanted 2 numbers less jet so it was a pretty marked improvement. I should mention though that this is only a mild 200 odd hp motor, and I wouldn't be surprised if something a bit warmer improved even more. The couple of inches of protrusion of the inlet pipe was just to try to dissuade any reversion but seeing as there wasn't any to start with I doubt it did anything useful.

The Thrush turbos only flow about 295cfm, which seems ok on a mild engine but for something hotter you'd probably want to use something that flows more yet is still quiet, like a Hooker perhaps...

The chamber is there just to trick the engine into thinking it has come to the end of the collector, there's no fancy stuff happening as in a two-stroke. Years ago I played around with balance pipes on a big-block and found it liked a big H pipe situated right where you'd end the collector. Looking back now makes me wonder whether the benefit was more from it's function as a big volume collector terminator than as a crossover...

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#34 _Inj gtr202_

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Posted 31 July 2012 - 02:42 PM

Oldjohnno, are you sure the rest of the exhaust wasn't holding it back or effecting it (both in terms of flow and/or design)? I also wonder if the hotdog in gtr202's pictures was back just before the diff there might be less issues? At the upper end of the 200-250hp you mention I think you need some pretty reasonable flow not to hold it back. Any ideas on what the Thrush flows? GTR202 any ideas on what the hotdog and muffler flow?

I'm not sure what the "hotdog" would flow.. the thing that is installed at the moment is more like a cork screw. What I'm guessing is happening is the gases are hitting the corkscrew and bouncing back or getting bottle necked.
The rear muffler is pretty much an open box with one inlet hole and 2 out, I can't see that having much restriction.

Once the new straight through "hotdog" is installed I guess I'll be playing with welders and grinders to turn it into a Terminator Box

Posted Image

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#35 _oldjohnno_

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Posted 01 August 2012 - 07:05 AM

I'm not sure what the "hotdog" would flow.. the thing that is installed at the moment is more like a cork screw.

Straight through units like hotdogs flow very very well on a flow bench (figures of around 1000cfm aren't unusual) but they behave very differently on a running engine. As I said before, they don't work as you'd expect them to. They don't seem to cause any problems when used as the final muffler, but then they aren't very quiet either...

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#36 _Ned Loh_

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Posted 01 August 2012 - 11:08 AM

IIRC Vizard says 2.2cfm per hp to ensure zero loss from back pressure. That chev article gtr202 linked to (looks like Vizard) says same.

Would type more but I'm on my phone and it gives me the willies.

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#37 biga064

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Posted 02 August 2012 - 05:03 PM

Are you guys here talking about spiral mufflers like the vortex power muffler which has a spiral in it that is supposed to draw the exhaust gases out creating a beneficial hp torque gain ???

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#38 _Inj gtr202_

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Posted 03 August 2012 - 07:29 AM

Are you guys here talking about spiral mufflers like the vortex power muffler which has a spiral in it that is supposed to draw the exhaust gases out creating a beneficial hp torque gain ???

thats the one

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#39 biga064

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Posted 03 August 2012 - 04:44 PM

I ve got one on my car dont know if it works or its snake oil ??? Bought it a couple of years back from a fellow in Qld . He was the manufacturer and claimed all these gains , who knows ???????

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#40 _Inj gtr202_

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Posted 05 August 2012 - 09:18 AM

I ve got one on my car dont know if it works or its snake oil ??? Bought it a couple of years back from a fellow in Qld . He was the manufacturer and claimed all these gains , who knows ???????

Since I'm now an expert on exhaust systems :stirpot:

. I would say it's not so much a dud muffler but rather poor placement. After the advice from the previous posts and a fair amount of reading, it seems that if the spiral muffler was placed after a large termination box and could handle the required CFM (which I'd say it would comforttably) it would not have been a problem. Yes this muffler I'm refering to is made by Gonzo exhausts in Queensland.

I took the car in yesterday back to the place that installed the muffler. The plan now is to order a hotdog to suite a 3" pipe, gutt it and fit it where the spiral currently fits. It will have an OD of around 4" but unfortunately a length of only about 13". Any extra volume that I can squeeze out of it will have to be done by me at home with the angle grinder.

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#41 _Inj gtr202_

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Posted 20 August 2012 - 01:22 PM

Spiral muffler is out, Gutted hotdog in.

power back to normal and noise levels back to a little on the loud side.
was an expensive lesson in exhausts.

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#42 Dave6179

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Posted 27 August 2012 - 11:22 AM

Mate had an exhaust (till the missus did the dirty) He played with muffler design, as he built and raced (very successfully) 'Modifieds'... the dirt car with the big wing on the roof.
I was using a Walker Super Turbo. He had made this large square box of a muffler, fitted it to my car. The noise was louder, and I lost most of the power over 3000rpm. Tried different timing to no avail. Eventually I checked the mixtures on the SU's (with my Colourtune), and they were all white. I fattened them up till blue again, and then I found out how good the muffler was. Now I'm on the 'Mk 3' muffler... smaller, quieter, more powerful again. Oh... mileage went up from 22mpg to 26.4mpg. I used to do a LOT of long trips when younger (and richer).
Another zorst shop I had a connection with reckoned Holdens needed backpressure. They have since been proved well wrong.
The wife has a VN V6, I fitted an off the shelf 'Mercury' muffler. I figured if you can see through it, it must be good. Then... I fitted an 'M&H' muffler from an Auckland speedshop. Same diameter, same physical size. The sound inside dropped, the sound outside dropped (it's the going away car so has to be quiet) and now you only have to breathe on the loud pedal and it's gone! It went from 31mpg to 34mpg. Then I fitted an HSV chip and... well you get the picture. Now gets 38.
In my opinion, an exhaust system will work on one car but not another (head, cam, manifold, etc). Unfortunately it's time and money to get your own 'right' for you. Horsepower doesn't have to be loud.

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#43 Dave6179

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Posted 05 September 2012 - 09:23 AM

Mate had an exhaust (till the missus did the dirty) He played with muffler design, as he built and raced (very successfully) 'Modifieds'... the dirt car with the big wing on the roof.
I was using a Walker Super Turbo. He had made this large square box of a muffler, fitted it to my car. The noise was louder, and I lost most of the power over 3000rpm. Tried different timing to no avail. Eventually I checked the mixtures on the SU's (with my Colourtune), and they were all white. I fattened them up till blue again, and then I found out how good the muffler was. Now I'm on the 'Mk 3' muffler... smaller, quieter, more powerful again. Oh... mileage went up from 22mpg to 26.4mpg. I used to do a LOT of long trips when younger (and richer).
Another zorst shop I had a connection with reckoned Holdens needed backpressure. They have since been proved well wrong.
The wife has a VN V6, I fitted an off the shelf 'Mercury' muffler. I figured if you can see through it, it must be good. Then... I fitted an 'M&H' muffler from an Auckland speedshop. Same diameter, same physical size. The sound inside dropped, the sound outside dropped (it's the going away car so has to be quiet) and now you only have to breathe on the loud pedal and it's gone! It went from 31mpg to 34mpg. Then I fitted an HSV chip and... well you get the picture. Now gets 38.
In my opinion, an exhaust system will work on one car but not another (head, cam, manifold, etc). Unfortunately it's time and money to get your own 'right' for you. Horsepower doesn't have to be loud.

Sorry, mate had an exhaust SHOP! As you were....