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The mkiv Supra Owners Club

BPU (Basic Performance Upgrade)


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Up to you my friend, but as a couple of members have already stated - they have/do run cars with the 2nd cat in place, and their cars are making around 0.9 bar

 

I think you may be getting a little hung up on this magic 0.9 bar figure. Think you should either drop both cats, fit a 1 bar ring, and a decent EBC as many many people have done before.... or, lose the 1st cat and run a decent boost gauge just to monitor whats happening in your manifold - if you're finding that the boost is creeping past what you're happy with, then look at fitting a RR

 

The FMIC is a step in the right direction though

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Kamal my opinion is you should go full BPU.

 

1.2 bar giving it the beans. Far more fun and what owning these cars is all about.

 

If you do it you will never look back. :)

 

thanks matt, I guess I'll have to think this through once I have all the parts off you :)

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  • 3 months later...

Is there any benefit or drawback fitting 650cc injectors to a j-spec bpu supra?

 

I know this question might be a bit silly, but I have a set of 650cc injectors with me, and not sure if I should use them or try and sell them. Any advice is much appreciated!

 

Thanks!

 

SJ

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Is there any benefit or drawback fitting 650cc injectors to a j-spec bpu supra?

 

I know this question might be a bit silly, but I have a set of 650cc injectors with me, and not sure if I should use them or try and sell them. Any advice is much appreciated!

 

Thanks!

 

SJ

 

will need mapping...

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  • 9 months later...

is there such a thing as a midpipe for the supra? i have the autobahn88 3" downpipe for mine but i'm pressuming this only removes the first cat. i would like to be able to remove the second set of cats but cant really afford to buy a decent full exhaust system right now, and dont want to bother with a crappy cheap system that i then have to replace again at a later date.

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  • 2 weeks later...
Would it be wise to fit bigger injectors to my j-spec before going full bpu?

 

Not necessary - there's too much fuel available even at BPU, there are gains to be had by being able to trim out fuel mapping wise. For safety you want to be retarding timing in places at BPU level rather than adding more fuel than is available with the standard injectors.

 

Spend your cash on a decent piggyback or ideally standalone ECU rather than larger injectors out of the block.

 

Cheers,

 

Brian.

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Not necessary - there's too much fuel available even at BPU, there are gains to be had by being able to trim out fuel mapping wise. For safety you want to be retarding timing in places at BPU level rather than adding more fuel than is available with the standard injectors.

 

Spend your cash on a decent piggyback or ideally standalone ECU rather than larger injectors out of the block.

 

Cheers,

 

Brian.

 

 

My local tuner tells me the injectors will be around 80% duty cycle at bpu, roughly 400bhp, 16psi on my jdm

2jz?

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My local tuner tells me the injectors will be around 80% duty cycle at bpu, roughly 400bhp, 16psi on my jdm

2jz?

 

I vaguely remember it being observed (Ian C?) that above a set boost pressure point, which may be 15 or 17psi, the Ecu runs the injectors at 100% DC just to be on the safe side.

Edited by carl0s (see edit history)
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I vaguely remember it being observed (Ian C?) that above a set boost pressure point, which may be 15 or 17psi, the Ecu runs the injectors at 100% DC just to be on the safe side.

 

Correct - stock JDM ECU opens the taps 100% just before fuel cut, when the stock MAP sensor sees pressure equating to a voltage above ~ 4v. Hence you use a mappable ECU to never let these things happen until unsafe boost levels where you can still have safety cuts.

 

An FCD is cruder though is effective - it just caps the voltage the stock ECU sees.

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Correct - stock JDM ECU opens the taps 100% just before fuel cut, when the stock MAP sensor sees pressure equating to a voltage above ~ 4v. Hence you use a mappable ECU to never let these things happen until unsafe boost levels where you can still have safety cuts.

 

An FCD is cruder though is effective - it just caps the voltage the stock ECU sees.

 

but the point at which the FCD caps the voltage, is the point at which the taps are open 100%, right?

So, a typical BPU car which uses an FCD, would generally be running 100% duty cycle at high rpm WOT?

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but the point at which the FCD caps the voltage, is the point at which the taps are open 100%, right?

So, a typical BPU car which uses an FCD, would generally be running 100% duty cycle at high rpm WOT?

 

Typically yes, although there is adjustment in some I've seen - GReddy BCC for example. The lower the voltage you set them to clamp at, the less fuel your injectors will put out as a maximum.

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Should I worry at top boost at WOT?

 

Like I said, the real concern is detonation with increased boost. The only way to fix that is with a mappable piggyback or standalone ECU. This will lower the risk you run of engine damage. That said, most BPU cars run for many miles without lunching their engines. How hard they are driven is anyone's guess.

 

The most common failure with increased boost is the Turbos themselves.

 

As a side note - if you're still on your original fuel pump it's worth replacing to ensure a consistent fuel supply. Typically people switch to a higher flow item like that on the UK MKIV Supra or a Walbro 255 LPH job.

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As tDR says: BPU itself generally comprises of: walbro pump (if existing is jdm), decat, suitable restrictor, colder plugs, thor FCD. Basically just raise boost and sort the fuel pump.

ECU modifications aren't normally done and it's not normal for the engines to break.

I'm sure somewhere in this 10 page thread entitled "BPU (Basic Performance Upgrade)" it will explain what the general BPU practice is.

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  • 9 months later...

I have a J-spec model and I'm wondering if there's any thing that I can change that makes it possible to remove the restrictor ring without having any problems or overspeeding turbos?

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Guest Budz86
I have a J-spec model and I'm wondering if there's any thing that I can change that makes it possible to remove the restrictor ring without having any problems or overspeeding turbos?

 

Depends on your boost controller really (assuming you have one) - most will cut the boost pressure by a set amount if it detects the pressure exceeding a set limit. If you've not got a BC then don't remove the ring as they will spin way too fast! Generally it's not advisable to remove it at all; best thing would be to get it drilled out a touch more if it's too restrictive. Remember you also need some back pressure to keep the turbo's spinning. Why do you want to remove it completely?

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Leave the ring in and up the boost with the controller, a boost controler can only make boost not make it less and needs a marging to work correctly,

If you have a piggy back ecu get it mapped for 1.2 boost and enjoy

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I run with 1st cat out, 2nd cat in and found mine hit fuel cut easily (in the colder winter period) and have since put an RR in - all good now and still lots of grunt plus the tubbies are safe.

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