since i replaced everything else on my APS ST kit that i thought might be contributing to my boost drop past 4500 rpms, i thought it only right to look deeper into my exhaust. i knew a single 3" exhaust was plenty enough to flow 500hp, i just knew it, despite others objections. so i called JIC and asked what the inside diameter of the resonator was, and they replied, "it has an ID of 3", just like the exhaust", and i believed them, since the resonator had quite a large bulge. but after dropping my downpipe and looking in there with a flashlight, i saw a terrible sight. the resonator tapered down very, very small. LESS THAN 2 INCHES . i bought my JIC used, and i think its an older model. im thinking since some people have the exhaust and arent dropping boost, that JIC changed the resonator sometime, and went to a bigger ID one.

today my exhaust shop cut out the resonator and welded in a straight 3" ss pipe in its place. i thought it was gonna be loud, but it really isnt much louder. you can actually hear the turbine spooling from the exhuast, its pretty cool when standing behind the car.

its a totally different car now, boost builds faster and holds. finally, the car is running like it should be, with the new JWT clutch/flywheel setup and a free flowing exhaust. below are some pics of the resonator.

 

I think all JIC singles come in this size.. mine is the same, dropped the exhaust for the exact same reason when going TT

 

omg thats horrible. You wouldve been better off w/ stock exhaust

 

I dropped my JIC too. It's for sale now.

 

its all good now, its truly a 3" exhaust

 

Wow-good thing I ordered the non resonated version. You pansys ordering the quiet ones deserve less boost....











.....j/k, glad you figured it out, Ive never seen an exhaust system taper down like that, thats horrible.

 

yeah thats pretty bad. less than 2 inches is smaller than the stock exhaust. and they told me it was for turbo applications, yeah right.

 

OT but Im curious as we have the same clutch/fw and diff ST kits. How much boost do you see in 1st gear?

 

not exactly sure, but probably around 7-7.5, im about to go do some datalogging with the new stuff, ill let you know when i get back.

 

Ok cool, cuz I only see 5-6psi...but I was spinning a little so prolly less load on the motor than catching traction? I know we dont see full boost in 1st gear usually just wanted to see what the APS ST's were doing....

 

yeah its not full boost.

 

tig, I almost fell out of my chair when I saw that pic. Unfuggenbelievable is all I have to say.

 

I'm pretty sure I see full boost in 1st gear...

Tig - it's good to see your problems are hopefully coming to an end!

I'd like to see what's on the inside of my exhaust muffler in the same way. I'm pretty sure it's not very restrictive though, as I haven't seemed to have any issues with backpressure.

 

thanks guys, just got back from doing some logs, boost drops about .75psi now, im still trying to figure out this blitz ebc so that isnt helping matters much. im gonna give the actuator rod a turn or 2 and see what happens.

 

Awesome then thats gotta be my problem too! I also have the JIC, good thing my new resonator-less exhaust will be here this week. Good job Tig I could friggin kiss you!!! <--- (not really)

 

i can't even believe i'm going to say this........




peter was right




ARRRRGHHHH!

ahm

 

hmm... maybe. But Tig says he is still getting a slight taper even now (.75psi) which is still more taper than he SHOULD be seeing. Also, I remember he took his exhaust off and ran the car just off the downpipe and it still tapered. Plus there are others I have heard from that have had the same tapering boost issue wiht other aftermarket exhausts.

APS has still changed their tune a few times, saying it is due to a safety feature programmed into the unichip, and then relating it to backpressure.

Am I right about this, or am I just crazy?

 

good problem solving, and an important contrib to the fi database.

 

Glad to hear everything is running smoothly!!

 

I thought way back you tried with NO exhaust and still had the boost taper issue???
In any case glad to hear that your car is running better.