BPU/CAT - boost question

Right im having major issues with my boost at the moment hitting 1.4 bar easily on full chat, the exhaust im using is very free flowing and I also have a 1.2bar restrictor ring a 3" apexi 1st decat and CW 2nd decat.

My question is what sort of boost are people hitting with the first cat out but second cat in and vice versa at BPU?

Is there much benifit in having the first out and second in over the first in and second out etc?

One of them has to go back in as the boost im hitting is quite frankly silly and im almost certain a smaller restrictor will not help

Mikey

You may go back to stock boost but putting one the cats back in.

Is the restrictor ring properly sized? Personally I would buy a 1 bar RR and use a boost controlloer to up the boost.

You may go back to stock boost but putting one the cats back in.

 

Is the restrictor ring properly sized? Personally I would buy a 1 bar RR and use a boost controlloer to up the boost.

can you up the boost beyond 1 bar with this then?

im not convinced a 1bar restrictor ring will drop it enough to be honest, the restriction on the 1.2 one is small enough and if its boosting to 1.4 I cant see how a smaller one will help it to 1.2, does anyone have a 1bar/1.2bar side by side for comparison?

ps it used to hit 1 sometimes 1.1 with the 2nd out and first in

The first cat is the most restrictive of the 2, so that is the one you want out. Just fit another restrictor ring with a smaller hole in it.

Is the restrictor ring properly sized? Personally I would buy a 1 bar RR and use a boost controlloer to up the boost.

That is the recommended route

im not convinced a 1bar restrictor ring will drop it enough to be honest, the restriction on the 1.2 one is small enough and if its boosting to 1.4 I cant see how a smaller one will help it to 1.2, does anyone have a 1bar/1.2bar side by side for comparison?

 

ps it used to hit 1 sometimes 1.1 with the 2nd out and first in

I had a 1.2bar and a 1 bar RR, and the hole is quite a bit different alas I have not got a picture to prove.

As mentioned by myself and Nic and Mr Rob downgrade the RR to 1 bar and use a BC to up the boost. Chris Wilson is your man for a 1 bar RR.

See what you're getting first with the 1 bar RR.

Remember in winter you can get boost spikes, was it the same in the summer or have you just went full decat?

I had a 1.2bar and a 1 bar RR, and the hole is quite a bit different alas I have not got a picture to prove.

 

As mentioned by myself and Nic and Mr Rob downgrade the RR to 1 bar and use a BC to up the boost. Chris Wilson is your man for a 1 bar RR.

 

See what you're getting first with the 1 bar RR.

 

Remember in winter you can get boost spikes, was it the same in the summer or have you just went full decat?

Just gone full decat, the summer months I was hitting 1/1.1 with the first still in but second out which makes me think a 1 bar ring might not work I only suggested putting the cat back in as its annoying me a bit pissing about with it and I know I could hit 1/1.1 before with no bother + cant afford a new set of turbos at the mo if they go pop

I can give you some info regarding the first one.

I had a full 3" free flow exhaust with only the first cat in. That made 353hp with a smooth delivery hitting aprox. 0,85 bar. Having nocked a aprox. 50mm hole through the 1st cat its now going to a max of 1,25 bar when its cold and that makes 393hp @ 20 degree C with a very BPU (doh!) delivery pushing hard when the 2nd turbo comes online

I can give you some info regarding the first one.

 

I had a full 3" free flow exhaust with only the first cat in. That made 353hp with a smooth delivery hitting aprox. 0,85 bar. Having nocked a aprox. 50mm hole through the 1st cat its now going to a max of 1,25 bar when its cold and that makes 393hp @ 20 degree C with a very BPU (doh!) delivery pushing hard when the 2nd turbo comes online

393 BHP from a BPU car, that is a bit ambitious. Unless you have a UK/Euro spec car then possible but not on a J-spec iirc, could be wrong though.

Just gone full decat, the summer months I was hitting 1/1.1 with the first still in but second out which makes me think a 1 bar ring might not work I only suggested putting the cat back in as its annoying me a bit pissing about with it and I know I could hit 1/1.1 before with no bother + cant afford a new set of turbos at the mo if they go pop

Go for a 1 bar RR they only cost about £14 from CW, put it this way you have to take the exhaust apart anyway to fit another cat. What would be the harm in trying?

393 BHP from a BPU car, that is a bit ambitious. Unless you have a UK/Euro spec car then possible but not on a J-spec iirc, could be wrong though.

Its a J-spec none the less. Could be off on the dyno though, but I've always heard a bit under 400hps (at flywheel though) is about right @ 1,2 bar.

J-spec or UK doesnt really matter as far as I know. As long as it is backed by enough fuel and you dont pass the aprox 430hps limited by the injectors, but that would probably need a FMIC and/or new cams as well as a mapping.

393 BHP from a BPU car, that is a bit ambitious. Unless you have a UK/Euro spec car then possible but not on a J-spec iirc, could be wrong though.

Both Homer & TerribleTurner pissed 390bhp in their BPU j-specs.

Both Homer & TerribleTurner pissed 390bhp in their BPU j-specs.

I stand corrected.

Theoretical max fly for Jspec is 410ish iirc, taking into account 440cc injectors, but they would be at or near 100% duty at such a power level.

UK spec iirc is closer to 500 ish, to be honest though i dont read up much on the UKs as im Jspec

Checked all boost pressure hoses are in excellent condition, Ryan sorted a BPU car today which was overboosting by spotting a boost hose (compressor to actuator) that was perishing & leaking

Checked all boost pressure hoses are in excellent condition, Ryan sorted a BPU car today which was overboosting by spotting a boost hose (compressor to actuator) that was perishing & leaking

surely a leak would reduce boost pressure no??

Will take a look tomorrow none the less

Not this particular pipe, a leak here will result in uncontrollable boost as your wastegate won't open

Not this particular pipe, a leak here will result in uncontrollable boost as your wastegate won't open

ahh I see so its the actual wastegate actuators then?

will have a look tomorrow

UK spec iirc is closer to 500 ish, to be honest though i dont read up much on the UKs as im Jspec

Really? Does anyone run that with stock tubbies? I know the fuel system is up to 500ish but I would think you would need more boost than the 1.3-1,4 I think is the max for the UK tubbies before they just blow hot air.

I have *heard* about 450rwhp from US cars

Really? Does anyone run that with stock tubbies? I know the fuel system is up to 500ish but I would think you would need more boost than the 1.3-1,4 I think is the max for the UK tubbies before they just blow hot air.

 

I have *heard* about 450rwhp from US cars

Im honestly not sure, i was talking from a fuel point of view. Iv not taken the time to look into the UK turbos because i dont have any, nor have i at any time decided to get any!

On a good setup hybrid car you can expect around 450 Bhp.

When my car was BPU it dynoed at 429hp (est. flywheel), that was with new short block, rebuilt/mildy tuned head, HKS cams, emanage, bigger injectors and with the turbos running in parallel.

When i had mine done last my UK spec was boosting to 1.3 bar. No boost controller

383.7 BHP at the flywheel,

303.3 BHP at the wheels,

514.5 Nm Torque

http://www.japmids.co.uk/forum/garage.php?mode=view_gallery_item&image_id=649

When i had mine done last my UK spec was boosting to 1.3 bar. No boost controller

383.7 BHP at the flywheel,

303.3 BHP at the wheels,

514.5 Nm Torque

 

Sounds about right then. Mine was as mentioned 393 @ flywhell, but that can easily be differences at dynos or vehicles. Good stuff to know