quick exhaust question....

What would a stock exhaust system with the Nur spec back box be like?? Much different to stock?? (performance wise)...

Also what difference would it be with a double de-cat too?? Is the rest of the stock piping still gonna be quite restrictive and cause problems??

thanks

It might not give you that much of a noticable difference but it will be louder, quite a bit compared to stock.

Double decat is a whole new world and will be very loud and give you good performance as long as the double decat is done correctly with all other parts to go with a double de cat

so the stock piping between the back box and the de-cat isn't gonna cause any problems?? ... with it not being 3" like most aftermarket exhausts.

Well I put a Kakimoto cat back on stock piping and no problems, you might need to get exhaust gasket made as I had too.

Plus when my stock exhaust came off my 2nd cat had either been gutted out or had broken away as there was no 2nd cat, probably had a chisel taken to it as its a cheap way to get a 2nd de cat

so the stock piping between the back box and the de-cat isn't gonna cause any problems?? ... with it not being 3" like most aftermarket exhausts.

I think Jim is looking to fit the Nur spec that retains the middle section of the stock exhaust. This stock pipework will be more restrictive than the 2.5" or 3" cat back systems and may not allow the boost to increase up to 1.1 or 1.2bar but i doubt it will cause serious problems like raising EGT's dangerously high, which can happen if you decat and then raise the boost whilst retaining the stock pipe.

Yeah, you're right mate, would be keeping the middle section of the stock exhaust.

If i did de-cat, then I suppose I could simply get a middle section made up?? (between the back box and de-cat pipes). Might sound stupid, but what prob would high EGT's cause??

Yeah, you're right mate, would be keeping the middle section of the stock exhaust.

 

If i did de-cat, then I suppose I could simply get a middle section made up?? (between the back box and de-cat pipes). Might sound stupid, but what prob would high EGT's cause??

Basically extremely high EGT's can melt spark plug tips (with bad consequences for turbo and poss engine) or even pistons ie very bad for the engine!

EGT's rise (i think) by running lean ie running high duty cycles and restricting air flow out of the engine.

Having a more restrictive exhaust means that as you run higher boost your EGT's will be higher than if you had a more free flowing one.

As to hard and fast rules on what is ok and what is not ok, is difficult.

You may find the restrictive exhaust naturally limits the boost and its probably fine like this, the problem can come if you then make adjustments elsewhere to raise the boost further without changing the exhaust.

eg decat a Jspec and leave the stock exhaust on and you may only see a boost rise to 0.9 form 0.8 and therefore no EGT problems will result.

Dissapointed with this the owner fits a bleed valve to run 1.2-1.3bar and EGT's (and injector duty cycles) may become a problem.

BTW a middle section would probably be expensive to make up, might as well sell the back box type Nur and get a cat back one.

I know a man who'd like a backbox type Nur!!!

you'll have problems fitting the mid section afterwards. As your gnna have to find a pipe with a twin exits. I had a nur spec back box for a while nd when i wanted the whole cat back i just bought a whole new single pipe exhaust.

don't have the back box... was just thinking about possible buying one.

Could I get away with double de-cat ... stock mid section and the nur back box ??