Replacement exhaust pipework, boost concern

[The-Plethora]

This is turning into an expensive month! I had the HKS super drager exhaust repaired today (rust mild steel) just in time as one of the mounts fell off 2 days before I was booked in.

 

Cash is a bit tight with car stuff lately and I would happily get a new stainless exhaust system but it seemed wasteful as the back box was in great condition so I took the decesion to repair it.

 

All the pipework from the cat all the way to the backbox (perfect condition) was replaced with stainless steel so I 'should' now have a fully stainless HKS exhaust with no rust prone mild steel in it.

 

I had a chat with the guy who did it briefly and he mentioned there was a silencer in the old bit (before the back box) we took out before the back box that "did very little quieting" and so it wouldnt be replaced, I am fine with that and wouldnt say no to the car being a little louder anyway. I am happy with the work the guy did.

 

My problem is that my HKS boost guage is showing boost up to 1.3 now regardless if I set the controller on 0.7 (low) or 1.0 (high).

 

Being a bit new to this I have heard about the dark art of restrictor rings and such but I understood they were attatched to the 1st cat way up front? so shouldn't have been cut out and replaced and cant see how this would effect the boost anyway?

I can try and get some pictures of the underside tomorrow but can anyone make a quick diagnosis as to if this would likely have changed anything or if the guy has simply changed something elsewhere?

 

Crappy quality pic below close enough to it from the web is what came off (note the in-line silencer))

 

https://www.evo-parts.co.uk/eshop/images/products/hipower409.gif

 

Cheers for any help, I dont want to risk damage to the car

[Homer]

That's a resonator, not a silencer, however removing it and putting in a straight peice will marginly increase exhaust flow and therefore have a knock-on effect of raising your base level boost.

 

It should only be a very small increase though, what was your minimum boost level at WOT prior to the change? Was the diameter of the pipe increased? IIRC the HKS normally used 3 inch pipe.

[The-Plethora]

99% of the time I run it at 0.7, previously I guess it hovered a little higher than I set it, maybe 0.8-9 at very most when giving it the beans. I will have a read of some of the guides etc and learn a bit, I presumed when it had passed the cats that was basically it but I guess this has the effect that it can get more throughput faster.

Sorry if I am being a bit vague, IT is more my forte, when it comes to manifolds and restrictor rings I am more a ask the teacher sort .

 

I will see if changing the controller settings to compensate tomorrow works out.

[Homer]

No worries, IT is my forte too, cars are just a hobby

 

Just to be clear, did you make any changes to the cat pipe? If you already had a decat in, which one was it - the 1st, 2nd or both?

[JODY T]

I recently removed my superdragger2. With a double decat and 1.2 bar RR,the car was running .9bar max.. I then fitted a NurspecR with no other exhaust changes and the boost rose to 1.1bar..

 

THe Nur is much straighter than the HKS design and freeier flowing.. This has probably happened to yours with the new pipework, only gone to unacceptable boost levels

 

Check yours has a RR, if it does try a 1bar one and readjust your boost controller

[jim]

If you don't mind me asking, how much did it cost to have the pipework made? Did you go to an exhaust specialist or a machinists?

[The-Plethora]

Jody I think you are right it is deffinately straighter than what I had before. I checked everything over today before I took it out and...back to normal maybe the guy had been playing a bit, notice my turbo timer was off.

I didn't make any cat changes Homer (still in), plenty of pics below so hopefully someone can say if anything looks amiss.

Jim I was initially quoted £100 to replace the piping from the joint (1st pic where the oval bit is) but asked if the rest was mild steel also, yup, so I asked them to replace the lot for £160 all in, very happy with that price. I got it sorted at Infinity Exhausts in Bristol (Yate) if this is helpful to anyone else...

 

http://www.infinity-exhausts.co.uk/

 

The ground is like a roasting dish today but managed to jack it up and take a few pics

 

Joint to backbox

 

Joint to cat (erm 2nd cat is it?)

 

Pipework to backbox

 

Overview pic (quite straight as Jody mentions)

 

One of the mounts

 

Pipework (this is the second cat I guess?)

 

Cheers for any pointers, oh yeah where abouts would a restrictor ring fit in with an exhaust system?

Edited April 10, 2010 by The-Plethora (see edit history)

[JODY T]

Infinity Exhaust are really Good, Martin is a seriously good welder.. he modified my Ukspec Double decat to fit my VVTI a week or so ago. Top job!

[The-Plethora]

Aha! Yes Jody he did say "I had one of these in the other day"

[Scott]

Does it definitely have the 1st cat in? Just thinking that maybe they took out the 1bar RR?