ratta tat tat
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Muffler advice
Hi, I'm a bit unsure about the system that's in my car at present. Mild pinto into 4-2-1 extractors, 2" outlet, 2" system with triflow muffler before the diff.
A guy I've dealt with at the muffler shop advised against anything bigger than 2 1/4 because I'll lose back pressure. He made a HUGE point about this but from what I see on the forums, bigger seems better. The triflow definitley keeps the car quiet, sounds fantastic at idle (crow cam), relatively quiet on throttle but makes popping ang gurgling noises when decelerating, the main reason I'm looking for other options.
I have a feeling the 2" system with straight through muffler after the diff will offer better performance. The engine is MUCH quiter than the xflow, so straight through might be ok. Otherwise chambered???
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gazz
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Re:Muffler advice
2013/01/12 21:29:32
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sounds like the guy at the muffler shop is an idiot. why would you want to restrict the exhaust from coming out of your engine? i had a 2.5inch system with 1 muffler in it and i went back to a 2.25inch with 1 muffler before the diff because the 2.5 was too loud for my liking. i didnt have the car dynoed to see the difference between the systems but it felt like i lost a little bit of performance from going back to the 2.25. i did gain the ability to hear things a lot clearer in the car though 
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Noono
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Re:Muffler advice
2013/01/13 11:06:08
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The muffler shop guy may well be right concerning the exhaust size.
Sure you want minimal back pressure, which a larger pipe gives.
But the LARGER an exhaust, the SLOWER the gases travel.
The faster the exhaust pulse travels, the better it scavenges out the spent engine gases.
It's a compromise.
Cheers Gregg
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Wozzah
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Re:Muffler advice
2013/01/13 13:56:01
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ratta tat tat
Hi, I'm a bit unsure about the system that's in my car at present. Mild pinto into 4-2-1 extractors, 2" outlet, 2" system with triflow muffler before the diff.
A guy I've dealt with at the muffler shop advised against anything bigger than 2 1/4 because I'll lose back pressure. He made a HUGE point about this but from what I see on the forums, bigger seems better. The triflow definitley keeps the car quiet, sounds fantastic at idle (crow cam), relatively quiet on throttle but makes popping ang gurgling noises when decelerating, the main reason I'm looking for other options.
I have a feeling the 2" system with straight through muffler after the diff will offer better performance. The engine is MUCH quiter than the xflow, so straight through might be ok. Otherwise chambered???
2" done right is ample for a mild Pinto. Not a fan of triflow mufflers though, they flow like crap. I just use a basic straight through glass packed muffler and resonator (no step downs or baffles). This keeps it quiet with a good note. Woz
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ratta tat tat
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Re:Muffler advice
2013/01/14 00:28:18
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Woz, are you referring to the resonator when you say "no step downs or baffles?? This would just be a hollow hot dog, no glass or perforations? And do you put the resonator before diff, muffler after diff? Or vica versa? Thanks
post edited by ratta tat tat - 2013/01/14 00:31:24
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Wozzah
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Re:Muffler advice
2013/01/14 13:33:21
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ratta tat tat
Woz, are you referring to the resonator when you say "no step downs or baffles?? This would just be a hollow hot dog, no glass or perforations?
And do you put the resonator before diff, muffler after diff? Or vica versa?
Thanks
Some hotdogs step down in internal diameter, you dont want this. I use the ones with no internal baffles or chambers, you can see straight through them and with no perforations (just holes, or perforations facing in, not out). Muffler usually mounted in the OE place, resonator under boot floor at the rear. Cheers Woz
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ratta tat tat
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Re:Muffler advice
2013/01/14 13:45:49
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ratta tat tat
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Re:Muffler advice
2013/03/11 21:27:53
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Wozzah Muffler usually mounted in the OE place, resonator under boot floor at the rear.
Cheers Woz
Hi Woz I've been reading Scott D's MK1 build on RSM. http://www.rsmotorsport.com.au/forums/viewtopic.php?f=27&t=3100&start=100 Danny recommends having the muffler under the boot floor, says it will go better. I like the look of it too, seems popular in europe.  Is there any reason not to do it this way? Muffer under boot, resonator before diff.
post edited by ratta tat tat - 2013/03/11 22:07:03
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martymexico
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Re:Muffler advice
2013/03/12 14:36:37
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This is the way I've done all my cars since the late 80s (teenager yrs ). For some reason running a back box(under boot) creates better sound and performance, tho my zetec mk1 has 2x boxes due to noise and both are same type and size. For a 1600 run a max of 2in zorst and 2.0 run a 2.25in. Fit a back box 1st try it for sound levels etc and if too loud(?) Fit a rezzy before the diff ..
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spigot
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Re:Muffler advice
2013/03/12 18:59:05
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Mounting mufflers and resonators as far back as possible gives the gases the opportunity to become more laminar in flow as opposed to turbulent. This is a major reason why cats and mounting right mufflers etc on the end of extractors is bad.
On the flip side some mufflers are actually designed to have a minimum pipe length after.
Laminar flow is not only more efficient but easier to noise suppress.
In theory the system needs to be optimised to work with the reduced back pressure of a larger pipe. In reality it just gets too noisy to suppress.
Please do not every use top fuel zoomies as an example. That is a totally different application with zero scavanging occurring in the design.
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ratta tat tat
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Re:Muffler advice
2013/03/19 22:14:00
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All done. Big thanks to FAT PIPES in Kallangur! Decel pop is still there but very muffled. Overall the system is quiter than what it was with the triflow.
post edited by ratta tat tat - 2013/03/20 00:50:59
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Matt75
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Re:Muffler advice
2013/03/19 22:50:21
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TheBrownHornet
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Re:Muffler advice
2013/03/20 11:59:03
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Just a thought to add on the "deceleration popping"
I've found that it can be caused by the carbs going way too lean on throttle shut off.
My very non-technical understanding is that the lean mixture wont ignite in the cylinder, but eventually builds up enough to ignite in the exhaust causing the popping.
You could have a play with idle mixture screws or crack open the butterfly a little more to test the theory.
Hope that helps,
Graham
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ratta tat tat
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Re:Muffler advice
2013/03/20 15:44:55
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Matt75
Look'n good mate.
Matt
Cheers Matt TheBrownHornet
Just a thought to add on the "deceleration popping"
I've found that it can be caused by the carbs going way too lean on throttle shut off.
My very non-technical understanding is that the lean mixture wont ignite in the cylinder, but eventually builds up enough to ignite in the exhaust causing the popping.
You could have a play with idle mixture screws or crack open the butterfly a little more to test the theory.
Hope that helps,
Graham
Thanks Graham I've started a new thread here
post edited by ratta tat tat - 2013/03/20 22:42:07
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spigot
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Re:Muffler advice
2013/03/20 19:55:45
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Leaner fuel mixtures are easier to ignite, eg. Lean mixtures at WOT can cause detonation.
The farting is caused by fuel being ignited post combustion chamber. This can be caused by rich mixtures or retarded ignition timing.
In gear deceleration induces high vacuum under the throttle plates. This can draw more fuel than normal from the idle and transition/progression circuits. The farting can be reduced through careful tuning of the carby and ignition timing.
In reality I would worry too much about it.
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