How loud ?

I am toying with going BPU.

I already have an after market exhaust on with both cats in place.

When the cats are removed how much louder will it be, I know this will probably vary with different exhausts but as a rule of thumb how much difference can I expect.

I dont know what make mine is.

I would not want it to be REALLY loud, dont want to draw Too much attention from the law

It will be loud, some exhaust can be ear splitting loud.

What exhaust you got? it might help to mention it mate as there might be members with the same exhaust.

As mentioned already it depends on the cat back. The back box makes by far the biggest difference. I found no real sound difference when going to fully decatted with a quiet cat back. The performance increase is enormous though (provided you make the other required mods)!

The back box is large and the pipe is wide, not sure what make it is as it was on when I got the car.

I will have a good look around it on Friday when I get home and see if there are any names stamped on it anywhere.

I wasnt going to go bpu, but having read about it on here it seems to give a big advantage in performance.

Just need a double decat , restrictor ring FCD and cooler plugs.

Been told by a reliable source thats all thats required .

Whats the average power gain in BHP would you say can be achieved by this:search:

Size has nothing to do with sound, the larger boxes are usually the quietist (i.e. more silencing)

Check for stamps (PS - If you see Jasma, thats not a make, just a stamp to say its meets exhaust standards, kind of like an ISO stamp in the UK)

PS: The power and spool hike with BPU is enormous, unless you're used to 350bhp+ on a RWD car now might not be the best time of year to do this

Edit - you forgot fuel pump, fuel filter and proper induction... along with a decent service. Power gain could be up to 360rwhp if you have a 6spd, 340rwhp for an auto. Any more than that any you have fantasy rolling road figures

Size has nothing to do with sound, the larger boxes are usually the quietist (i.e. more silencing)

 

Check for stamps (PS - If you see Jasma, thats not a make, just a stamp to say its meets exhaust standards, kind of like an ISO stamp in the UK)

In that case it may not be too loud when decatted as the back box is really quite large.

The sound at the moment with both cats in is very quite, from the back of the car there a bit of a pulsing beat but when you rev it hard its not that loud at all, if anything it sounds subdued.I actaully dont think its much loader if any from the std exhaust

Dont quite understand it as you see these kids with Corsa knockig around and all they have done is put a SS back box on and they sound louder /throatier than mine

Size has nothing to do with sound, the larger boxes are usually the quietist (i.e. more silencing)

 

Check for stamps (PS - If you see Jasma, thats not a make, just a stamp to say its meets exhaust standards, kind of like an ISO stamp in the UK)

 

PS: The power and spool hike with BPU is enormous, unless you're used to 350bhp+ on a RWD car now might not be the best time of year to do this

 

Edit - you forgot fuel pump, fuel filter and proper induction... along with a decent service. Power gain could be up to 360rwhp if you have a 6spd, 340rwhp for an auto. Any more than that any you have fantasy rolling road figures

There seems alot of conflicting opinions on here re the induction , many folks say that the std induction/air filter is by FAR the best due to the heat.

Also I was told by a specialist that the std fuel pump was sufficient

How much extra bhp should I see then ??

In that case it may not be too loud when decatted as the back box is really quite large.

 

The sound at the moment with both cats in is very quite, from the back of the car there a bit of a pulsing beat but when you rev it hard its not that loud at all, if anything it sounds subdued.I actaully dont think its much loader if any from the std exhaust

 

Dont quite understand it as you see these kids with Corsa knocking around and all they have done is put a SS back box on and they sound louder /throatier than mine

If its quiet now, it won't be significantly different once decatted, though it will sound much nicer overall

The thing with the chav car is they have tiny CC and tiny pipes, this means high DB along with high pitched exhaust sound caused by the small size mid pipes and low silencing in the back box.

The Supra has 2-3 times the engine capacity of these shit boxes so even a straight pipe will sound much deeper and less "painful" than a little 4cyl.

Even with a big single and virtually un-silenced exhaust, it's still quieter than the noddy cars at lower revs. Once the turbo hits high boost and the wastegate opens its a different matter though

There seems alot of conflicting opinions on here re the induction , many folks say that the std induction/air filter is by FAR the best due to the heat.

 

Also I was told by a specialist that the std fuel pump was sufficient

 

How much extra bhp should I see then ??

The stock airbox IS by far the best , I don’t see how you can see any conflict in that? Everyone agrees on that (except the worthless chav elements, but they have no credence here)

Std fuel pump on the jspec may be sufficient, but these cars are getting on now. Who exactly was it that told you that information? Its good to know so that future members can be warned.

See this link for more details: bpu

Thanks for the advise , really getting tempted now to go BPU.

I am going to get the mileage check done on Friday, you would have seen it, the guy who checks the auction figures out in Japan for a tenner.

Mine had 68k kms on it when I got it. If it comes back with 100k miles on would you NOT recommend doing the bpu due to putting more strain on a worn engine.

Chris Wilson , when he drove my car, did say that the first turbo spooled up quicker than average for a std car, but he said it was a wee bit tappity, also if I start the car everday there is NO smoke on startup, if I leave it for 3-4 days there is a couple of seconds of light smoke that clear quickly.

Just trying to quantify how many miles it could have done...

Also I was told by a specialist that the std fuel pump was sufficient

If your car is a JDM, the pump will probably be past its best. If you remove both cats and fit a restrictor ring, you could run 1.1 to 1.2 bar of boost. An old JDM pump will struggle to provide enough fuel. Putting in a UK or Walbro pump should be more than adequate. It is not worth the risk of running an old pump at its limit. There are quite a few specialists who don't know what they are talking about. There are those who know exactly what they are talking about and hope that you will return to them for an engine rebuild when a piston melts due to running lean. Chris is not one of them.

The MKIV engine is very strong, there are many car with a lot more than 100,000 mile with much greater loads than you propose.

The start up smoke you describe is probably due to tired valve stem oil seals.

If your car is a JDM, the pump will probably be past its best. If you remove both cats and fit a restrictor ring, you could run 1.1 to 1.2 bar of boost. An old JDM pump will struggle to provide enough fuel. Putting in a UK or Walbro pump should be more than adequate. It is not worth the risk of running an old pump at its limit. There are quite a few specialists who don't know what they are talking about. There are those who know exactly what they are talking about and hope that you will return to them for an engine rebuild when a piston melts due to running lean.

The specialist who told me my info definatley knows his stuff

Size has nothing to do with sound, the larger boxes are usually the quietist (i.e. more silencing)

 

Check for stamps (PS - If you see Jasma, thats not a make, just a stamp to say its meets exhaust standards, kind of like an ISO stamp in the UK)

 

PS: The power and spool hike with BPU is enormous, unless you're used to 350bhp+ on a RWD car now might not be the best time of year to do this

 

Edit - you forgot fuel pump, fuel filter and proper induction... along with a decent service. Power gain could be up to 360rwhp if you have a 6spd, 340rwhp for an auto. Any more than that any you have fantasy rolling road figures

When you say proper induction what are you referring to changing

From what i've read people seem to think the proper airbox is best all round next would be an apexi in a good airbox with cold air feed (i cant say definatively whether the later would gain power, but they flow more air so i assume they(cones) would make a small gain, but they dont filter as well, i do think they sound much cooler though)

The specialist who told me my info definatley knows his stuff

I just find it surprising that any specialist, would recommend using a ten years old pump, when contemplating pushing the pump harder than it has every had to cope with before.

If it were my car I would put in a new pump.

Changing the fuel pump was one of the first things I did before all the other performance mods. However it is your engine not mine.

Have to agree, never heard an arguement regards the value of fitting a new pump.

The specialist who told me my info definatley knows his stuff

So who is he? Name and shame?

If you've already spoken to Chris Wilson then you are in good hands, but if the above advice is based on something he's said then you've misunderstood.

Have to agree, never heard an arguement regards the value of fitting a new pump.

You post isn't very clear, are you saying that fitting a new pump is beneficial or not necessary?

Have to agree, never heard an arguement regards the value of fitting a new pump.

How about running lean and needing a rebuild.

Hmmm new pump £69 engine rebuild £2000 minimum , no value at all really.