3" exhaust and failing aux ports

mnrthrt · 08-10-2010, 01:46 AM

Im new to rotary theory and application. I have a chance to pick up an HKS Silent Hi-Power exhaust for VERY CHEAP! I have a 91 N/A with stock exhaust and no internal mods.

I heard anything more than 2" will keep the aux ports from opening because of back pressure issues? If i picked this exhaust up is there a way i can combat the backpressure issue? I plan on getting a racing beat or corksport header with this set up. If I street port or bridgeport would that help? Thanks for any help!

I plan on doing a t2 swap in a little less than a year so I figured that exhaust would be great with the downpipe they make for the future install. Would rather not waste money on a 2" cat back for a soon turbo'd rex as im already tossing money in the header. Again Thanks for the help.

Howru · 08-10-2010, 05:15 AM

S5's (89-91) activate the aux ports by the air pump, so you should be ok. It's the S4's that have to deal with the exhaust back pressure for aux ports to work.

mnrthrt · 08-10-2010, 05:52 AM

Oh. Thanks for the response. So I should go for it then? Will probably be loud as hell! ha

Silver86 · 08-10-2010, 09:14 AM

Quote:

Originally Posted by mnrthrt

Oh. Thanks for the response. So I should go for it then? Will probably be loud as hell! ha

i would... but youd be surprised... i have a corksport cat-back on my 86 N/a, and its actually surprisingly quiet. but whats loud to someone else might not be loud to me...

mnrthrt · 08-10-2010, 11:05 AM

i actually ordered the corksport header back system but it was back ordered, waited a month, dude never got back to me in time so it looks like im gonna grab the hks

found a 3 inch pre-silencer from racing beat i think i might couple with this.

josh18_2k · 08-11-2010, 09:09 AM

the stock manifold really quiets things down. With a header it will indeed be loud as shit. I had a greddy power extreme dual exhaust (two very big cans) and it was still intolerable. I would never put a header on a daily driver

Silver86 · 08-11-2010, 09:20 AM

Quote:

Originally Posted by josh18_2k

the stock manifold really quiets things down. With a header it will indeed be loud as shit. I had a greddy power extreme dual exhaust (two very big cans) and it was still intolerable. I would never put a header on a daily driver

this excites me.

My5ABaby · 08-12-2010, 08:20 AM

Quote:

Originally Posted by josh18_2k

the stock manifold really quiets things down. With a header it will indeed be loud as shit. I had a greddy power extreme dual exhaust (two very big cans) and it was still intolerable. I would never put a header on a daily driver

I disagree. I'm running the RB header, RB presilencer, stock y-pipe, and 2 cheap Midas mufflers and find it very tolerable. This includes not having a radio to cover up any of the noise.

project86 · 08-12-2010, 11:49 AM

Quote:

Originally Posted by My5ABaby

I disagree. I'm running the RB header, RB presilencer, stock y-pipe, and 2 cheap Midas mufflers and find it very tolerable. This includes not having a radio to cover up any of the noise.

+1 to this. I think alot of the noise has to do with muffler choice.

Phoenix7 · 08-12-2010, 11:38 PM

Quote:

Originally Posted by josh18_2k

the stock manifold really quiets things down. With a header it will indeed be loud as shit. I had a greddy power extreme dual exhaust (two very big cans) and it was still intolerable. I would never put a header on a daily driver

I have RB headers, midpipe and HKS old-school catback on our NA...we DDed that car until we got the bimmer. You CAN have straight pipes on your NA but you need to have a GOOD catback to quiet it down.

Before the HKS (52mm) catback we had Apex-i N1 Duals and they were definitely LOUD and intolerable...to the point that we bought earplugs. Maybe I'm just too old for the loud exhausts?

If you have an S4 you also have to make sure you get the S4 midpipe that incorporates the "split-air pipe" so you can actuate the Aux ports via backpressure.

My5ABaby · 08-12-2010, 11:43 PM

Quote:

Originally Posted by Phoenix7

Also make sure you get the S5 midpipe that incorporates the "split-air pipe" so you can actuate the Aux ports.

S4...

mnrthrt · 08-11-2010, 11:26 AM

josh: think i will have any problems with power loss with that 3" exhast?

josh18_2k · 08-11-2010, 02:16 PM

i dunno, i never dyno'd or anytting like that. there is definately a power gain on the top end (10-15hp maybe?), since the stock brick manifold thing doesnt flow very well. im sure you can find before/after dyno charts somewhere. my car was my daily at the time, and i got sick of it quick after putting on the header. i dreaded driving it.

NYsNumba1Man · 08-11-2010, 10:35 PM

I'm currently running an hks silent hi power exhaust..... Does that mean my aux ports aren't activating?

I have all stock cats and headers, i think i might have an exhaust leak somewhere near the headers though (sounds like an exhaust leak in the engine bay)

how can you test to see if your aux ports are working?

Nismo · 08-12-2010, 07:50 AM

Quote:

Originally Posted by NYsNumba1Man

I'm currently running an hks silent hi power exhaust..... Does that mean my aux ports aren't activating?

I have all stock cats and headers, i think i might have an exhaust leak somewhere near the headers though (sounds like an exhaust leak in the engine bay)

how can you test to see if your aux ports are working?

Put grease/Vaseline on the rods of the actuators, take the car for a rip and make sure to rev above 4k if the grease has moved your ports work.

08-10-2010, 01:46 AM	#1
mnrthrt cel=life story Join Date: Apr 2010 Location: blow iTrader: (0) Posts: 32 Rep Power: 0	3" exhaust and failing aux ports Im new to rotary theory and application. I have a chance to pick up an HKS Silent Hi-Power exhaust for VERY CHEAP! I have a 91 N/A with stock exhaust and no internal mods. I heard anything more than 2" will keep the aux ports from opening because of back pressure issues? If i picked this exhaust up is there a way i can combat the backpressure issue? I plan on getting a racing beat or corksport header with this set up. If I street port or bridgeport would that help? Thanks for any help! I plan on doing a t2 swap in a little less than a year so I figured that exhaust would be great with the downpipe they make for the future install. Would rather not waste money on a 2" cat back for a soon turbo'd rex as im already tossing money in the header. Again Thanks for the help. Last edited by mnrthrt; 08-10-2010 at 01:50 AM..

08-10-2010, 05:15 AM	#2
Howru Louvers! Join Date: Mar 2008 Location: Vallejo, CA iTrader: (3) Posts: 66 Rep Power: 17	S5's (89-91) activate the aux ports by the air pump, so you should be ok. It's the S4's that have to deal with the exhaust back pressure for aux ports to work. __________________ 88 GXL N/A -- Maybe I should've kept the exhaust diffusers...

08-11-2010, 09:09 AM	#6
josh18_2k Rotary Fanatic Join Date: Feb 2008 Location: Gresham, OR iTrader: (0) Posts: 473 Rep Power: 17	the stock manifold really quiets things down. With a header it will indeed be loud as shit. I had a greddy power extreme dual exhaust (two very big cans) and it was still intolerable. I would never put a header on a daily driver __________________

08-11-2010, 02:16 PM	#13
josh18_2k Rotary Fanatic Join Date: Feb 2008 Location: Gresham, OR iTrader: (0) Posts: 473 Rep Power: 17	i dunno, i never dyno'd or anytting like that. there is definately a power gain on the top end (10-15hp maybe?), since the stock brick manifold thing doesnt flow very well. im sure you can find before/after dyno charts somewhere. my car was my daily at the time, and i got sick of it quick after putting on the header. i dreaded driving it. __________________

08-10-2010, 05:52 AM	#3
mnrthrt cel=life story Join Date: Apr 2010 Location: blow iTrader: (0) Posts: 32 Rep Power: 0	Oh. Thanks for the response. So I should go for it then? Will probably be loud as hell! ha

08-10-2010, 11:05 AM	#5
mnrthrt cel=life story Join Date: Apr 2010 Location: blow iTrader: (0) Posts: 32 Rep Power: 0	i actually ordered the corksport header back system but it was back ordered, waited a month, dude never got back to me in time so it looks like im gonna grab the hks found a 3 inch pre-silencer from racing beat i think i might couple with this.

08-11-2010, 11:26 AM	#12
mnrthrt cel=life story Join Date: Apr 2010 Location: blow iTrader: (0) Posts: 32 Rep Power: 0	josh: think i will have any problems with power loss with that 3" exhast?