Exhaust silencer back pressure bad?
10-04-09, 02:13 PM
#1
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Exhaust silencer back pressure bad?
Im running a gt35r and straight through 3" exhaust with an HKS high power. With the street port I have, my car is pretty loud. For long distances, I have an additional exhaust sliencer which fits into the end of the HKS that works nicely but before I start using it, I would like your views on whether this will have any negative side effects on my car? (Heat, Pressure??) I don't plan to use it all the time of course.
Last edited by STIXTC; 10-04-09 at 02:29 PM. Reason: Not very clear
10-04-09, 02:21 PM
#2
Turd Ferguson
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is the "plug" the same as the "silencer"? just confusing when you interchange the two terms - which makes me think there are two different items you put in the exhaust.
if it's the silencer in the picture, then you'll be ok. you might lose a small amount of ponies but it'll be fine.
if it's the silencer in the picture, then you'll be ok. you might lose a small amount of ponies but it'll be fine.
10-04-09, 02:25 PM
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is the "plug" the same as the "silencer"? just confusing when you interchange the two terms - which makes me think there are two different items you put in the exhaust.
if it's the silencer in the picture, then you'll be ok. you might lose a small amount of ponies but it'll be fine.
if it's the silencer in the picture, then you'll be ok. you might lose a small amount of ponies but it'll be fine.
10-05-09, 02:01 AM
#6
Plug is the operative word as that silencer will severely restrict the exhuast to the tune of about 1/10th of what it would otherwise flow. More than a few ponies here. IMO, I wouldn't boost too much for too long due to the heat and pressure that will build in the engine and exhaust. If you have to run it with that plug for any substantial period of time then I would suggest building an exhaust that is relatively quieter and free flowing.
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10-05-09, 08:07 AM
#9
Original Gangster/Rotary!
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An option is to switch to an Apexi N1 or GT Spec catback and get the Apex'i ATS made specifically for it. I run one occasionally, it's basically a spring-loaded silencer and works very well:
http://www.apexi-usa.com/products/?id=5327
http://www.apexi-usa.com/products/?id=5327
10-05-09, 11:17 AM
#10
+1 on the resonator, if you still aren't happy with that change catbacks.
I have a GT35R as well but I have a resonated midpipe and a racingbeat dual tip catback. At cruise the car is pretty darn quiet, it needs to be since we have have noise and smog laws that are aggressively inforced here in cali.
I have a GT35R as well but I have a resonated midpipe and a racingbeat dual tip catback. At cruise the car is pretty darn quiet, it needs to be since we have have noise and smog laws that are aggressively inforced here in cali.
10-05-09, 07:50 PM
#11
The flow number was derived from my flow bench testing of restrictor plates: A 30mm orifice placed in a 3" pipe resulted in about 113 cfm of flow (@ 20.3" H2O); about 1/20 of what a short straight piece of 3" will flow at that pressure drop AND about 1/10 of what a good, straight-through, resonated 3" cat-back might flow.
With the restrictor, you've reduced the effective area of the pipe to < 1/7 of what it originally was AND increased pressure (for a given flow) by a factor of about 100. (Yes, you read that correctly; pressure changes exponentially relative to the change in volume flow, i.e., CFM.)
As an example: To get 1000 cfm through a good straight through 3” catback should result in a back pressure of 1 PSI or less; by contrast, to get that same 1000cfm flow through that 30mm orifice will take on the order of 57 PSI.
Depending on engine efficiencies, etc.., our 13B's might produce on the order of 500 to 700 exhaust CFM at 1bar of boost. At 500ish CFM, the back pressure resulting from the 30mm orifice will be on the order of 15 PSI; at 700 CFM it will near 30 PSI.
Hope this illustrates the situation.
10-05-09, 09:20 PM
#12
Plug is the operative word as that silencer will severely restrict the exhuast to the tune of about 1/10th of what it would otherwise flow. More than a few ponies here. IMO, I wouldn't boost too much for too long due to the heat and pressure that will build in the engine and exhaust. If you have to run it with that plug for any substantial period of time then I would suggest building an exhaust that is relatively quieter and free flowing.
BUT!!!! on your silencer deal... I cracked my header boosting with it in..... So.....i'll never do it again and I would advise everyone not to... Exhaust leaks are definitely not good on fd's..... Talk about loud......
10-06-09, 02:04 AM
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Thanks alot guys, I have decided not to use it and I think Im going to order the Apexi catback. Yesterday I decided to take it out for a trip to the gym and good thing I did becoz I picked up a race with an STI on the way home. Man, I would have been P*off if I had the plug in. RX - 1 STI - 0
10-06-09, 11:43 AM
#14
Original Gangster/Rotary!
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+1 i'm building a 3 in free flowing quieter exhaust with a flow-master bullet resonator in the position of my cat and a borla twin tip muffler for quietness. I dont want to lose too much power but I know nothing will give me as much power as I have with it straight through... I'm at 463 to the wheels and I might re-tune depending on how the car runs afterwards.
BUT!!!! on your silencer deal... I cracked my header boosting with it in..... So.....i'll never do it again and I would advise everyone not to... Exhaust leaks are definitely not good on fd's..... Talk about loud......
BUT!!!! on your silencer deal... I cracked my header boosting with it in..... So.....i'll never do it again and I would advise everyone not to... Exhaust leaks are definitely not good on fd's..... Talk about loud......
Also, what header are you running
You cracked your downpipe from running a silencer
10-06-09, 07:26 PM
#16
but not the down-pipe..... A silencer is very restricting, and the pressure along with some other contributing factors could cause the header to crack.... Well it was that and the fact that there was only one exhaust hanger on the whole system towards the muffler. So everytime the car was under a load or shifted the whole mass of the exhaust would be weighted on the header... So both of those things were most likely contributing factors. I'll most likely get it re-tuned after we build my new system.
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