I have an Apex N1 single side. Wasn't too loud when the motor was stock. I got a rebuild with a good port job, 62-1, injectors, haltech, the whole deal. After that it was unbearably loud. So I goto the RX7 site and order me a slip in silencer. Sounded much better, I was breaking the motor in at the time so I never got on the gas at all and never came on boost. So I take the car in to get tuned out and remove the silencer (it was a pain to get out, had to hammer it in, in the first place) SO it get's tuned out, running great, I hammer the silencer back in and put a bolt in. Get on the hwy and go a few miles before getting on it and then in 3rd gear about 4k rpm's I stomp it. Turbo starts to spool up then it kicks and bucks and spits and farts and smokes at about 5.5k rpm, oh **** what is going on.

I pull over and check it out. Oil is pooling under the car. Ends up I cracked a front housing, didn't know the cause till we got it back to the shop. Then noticed the silencer was pushed out ALOT at teh top the bottom was still bolted in. It was actually bent to be able to come out that far on top and be still inside at the bottom where the bolt was holding it in. So, apparently the backpressure was too much for it.

Verdict, New front housing and seals. The rotor housings looked ok. I have a J&S retard on it so that probably saved the motor.

Beware if you wanna add a silencer to your N1 Pipe. It might be ok for a stock car with a stock turbo but man it sucks on a well flowing engine.

Anyone used a Greddy S2 Muffler? I may tray it, heard it cuts the noise down a bit.

 

That sux man thx for the warning.

 

hmmmmmmmm................

 

I think you're trying to blame backpressure for blowing your engine. That would be very, very wrong...

IMO plugging up your exhaust with "silencer" is just plain dumb anyway. They drop the noise level by being very restrictive, which it exactly what your free stock mufflers did.

The reason Mazda used a dual muffler exhaust was so it could reduce backpressure and noise. If you wanted a reasonable exhaust noise level, sticking to that design would've been a much smarter route to take for your aftermarket exhaust than simply plugging it up.

 

I like my apex n1 duals. loud but not too loud. if you want to tone it down a bit, get a resonator or a presilencer...that is if you dont already have one.

Ben

 

resonator is definitly the way to go, silencer "works" but it works in the exact wrong way

 

The silencers work great if you're just trying to quiet it down as you're going through town, and then removing them when you're out to do whatever/at the track. However, permanently using them to silence the exhaust is rather dumb. Regradless, the backpressure from the silencer more than likely wasn't what caused this to happen.

 

How much to fix all this?

 

I wonder why it was running so well before I stuck the silencer in. It was reving fine and even with the silencer in it would rev fine with the clutch in. Under load when the turbo started spooling up is when it wouldn't wind up past 5.5k and was backfiring and surging. It would wind up under load before I put the silencer in just fine. I'm running 3" all the way from the turbo on back with a resonator (basically a glasspack looking deal), no converter and the N1 can. The silencer was about 1.5 inches, maybe a little less. It really choked it down. but it never clicked that would be bad.

Any ideas then if you don't think it was the silencer?

 

When I put my silencers in on my duel N1's I think I get more low end power. When I take them out it feels like I have more top end power. I could be wrong but that is what it feels like.

 

I'm afraid to ask. Already have well over 13k in this motor, too late to turn back now.

 

Obviously something was done wrong during tuning and the owner of the shop doesn't want to take responsibility for it, so he tells you it was your silencer's fault. Backpressure didn't blow up your engine. If you were getting that much, the engine would have stalled out long before that. BTW...who the hell tunes with the silencer out? Thats like tuning a car then putting on a totally different, much more restrictive exhaust.

-Joe

 

wouldn't you wanna tune your car with the same setup you'd be driving it with??

 

i highly doubt back pressure blew your engine. infact, this is the first post i have ever read where someone blamed their exuast system for choking their engine to death.

 

Ummm no. Think about it, wouldn't you want your car tuned for optimal performance at it's best? If you tuned it with the silencer in you wouldn't be getting your best performance when you took it out. The retarded idea is tuning the car with the silencer in.

 

I'm with these guys.

Also since you have a haltec can't you have 2 maps? Why not tune it with open exhaust and then make another map with the silencer in so your AFR'S and everything are poerfect either way.

Anyways I highly doubt it's the silencer. Get a different engine builder to tear it apart and inspect exactly what went wrong. Then you can have a 3rd party confirm if the engine wasn't done right.

 

since our cars have the tendency to throw flames when running rich. I wonder how much damage could occur when the flame doesn't have enough to flow out the exhaust since its silenced up. any thoughts on that?

 

13k?
Whats is got a guru eshaft, all new housings/irons/seals, balanced, cryo'd, extra dowel pins, bigger T bolts, pport etc...

 

Ummm...no back to you. With a more restrictive exhaust, all kinds of things change that affect the tuning. The amount of boost you produce is a big one for starters. There is no advantage in "tuning it for optimal performance" then downgrading the exhaust unless he would be regularly removing the silencer for racing. He obviously was not planning to take the silencer out of the car, so there is no need to tune it that way.

-Joe

 

New rotors, new housings, new turbo, injectors, rail, FMIC, haltech, fuel pump, regulator, gauges, porting, machine for 3mm seals. custom built exhaust manifold and dp, polishing upper and lower intake, profec b, tial bov, tial wastegate, knocksensor, Fluidyne radiator, elec fan, ignition coils, cornerseal springs, side seal springs, seals, 3rd gen front counter weight, clutch, aluminum flywheel, 3 window bearings, oil pan baffle plate, oil seal sets, inner oil seal o rings and springs, outter", 93 rear oil pressure regulator, machine oil groove in stationary gears, oil pump porting, 3 bar map sensor, all the hoses and oil lines, turbo water fittings, pulsation dampner, tuning and installation of haltech.

It all adds up.

I had intended to not run the silencer at all is why they tuned it without it. I just put it in for the 400 mile drive back home.

Why would the car run fine up to 8k rpms and at 14psi without the silencer and then not want to rev passed 5.5k after I installed it under load? Like I said it wouls rev up just fine with the clutch in but when the turbo would start spooling under load it just wouldn't wind up and started poping and surging and smoked like mad. Also remember my silencer was bent out as if the pressure was trying to push it out. This engine flows really well and breaths fire like mad. It did before I stuck the silencer in anyway. I assume the front housing cracking was due to detonation, would a really restrictive exhaust cause detonation or maybe exhaust pushing back into the cylinders?

 

Because of the massive exhaust restriction. What did you expect would happen?

Those things shouldn't be called silencers; they should be called restrictors, because that's what they do. The lower noise is purely because of the reduced flow.

 

So your saying the restriction caused by the silencer did or did not cause the problem? I gathered from your first post that it was not to blame but I don't see any other reason.

 

You got any pictures of the engine and exhaust? Also where is the car now? have you had anyone tear it apart to make sure the engine wasnt to blame?

 

In my mind i can visualize the engine trying to turn but there's pressure on all 3 sides of the rotor, but for that to happen there would have to be A LOT of pressure. I mean, imagine how these engines are built! i would expect that the exhaust manifold (or headers) would blow off first which is sounds like it tried to do that with your pipe nearly ripped off.

The odd thing is that the engine did not die, normally back pressure of that kind would stall the engine out.

Assuming that, for whatever reason, the engine did not stall and kept trying to turn; i would expect it to start to run VERY rich VERY fast, added that to the boost...i suppose it could be enough to blow the front housing apart, but i would also think that maybe it wasn't installed very well. By any chance, or the dowel pins or long tension bolts damaged?

 

It's been taken apart and inspected. Looks fine. I let off the gas like within 2 seconds of this happening. I had to replace the front end piece, the rotor housing was ok, I replaced it with an S5 (thicker). I was only boosting half a bar or so. Went ahead and replaced the seals. Also found out I had a vaccume leak on the lower intake manifold. Oh well gonna see what happens I guess when I start it.