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The mkiv Supra Owners Club

Fitting a blow off valve???


RussVVTi6Speed

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Not a good idea on a VVTi as they run MAF, as opposed to speed/density (MAP/MAT) for air metering.

 

If you let air in through the MAF meter and then blow a proportion of it out, the ECU will get confused over how much fuel it should be delivering. This is explained more fully in the link that magically appears every time the words Blow Off Valve occurs in a post :)

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I dont suppose you have a picture at least of it installed foodfreak that we/i can refer to if need be . This is my first turbo car and although i'm trying to learn as much as i can some write ups are hard to follow if you dont know what each pipe/hose is for/named .

Thanks.

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How complicated is it?

 

I want to fit a Blow off valve to my VVTi TT its a SARD r2d2, where do I start anyone??

 

Do you have a Supra specific kit or just the universal BOV?

 

If you have the Supra specific kit then it should be fairly straight forward, as the kit includes everything needed for the install.

 

If it is just a universal BOV, then you will also need an aluminium intercooler hard pipe and a boss welded onto the hardpipe to attach the BOV too.

 

Very good advice from Digsy above, fitting a vent to atmosphere BOV on a VVTi is a bad idea, as it WILL cause fueling issues. If you must fit an aftermarket BOV, then make sure it recirculates the air, rather than releasing the air.

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It causes the fuelling issues no matter what gearbox you are using - it's just more apparent on the autobox as it is a bigger load on the almost-stalling engine. If you've got an atmo BOV, a MAF system, and a manual box I can guarantee you I can stall your car ;)

 

-Ian

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There is one other option if you do want to fit a vent to atmosphere BOV on a VVTi. HKS do what the call the EIDS, this is an electronic gizmo that is suppose to fool the ECU on cars with a MAF sensor, to prevent fueling issues. How it works and how effective it is I have no idea.

 

http://www.hks-power.co.jp/products/blow_off/sqv/img/option5.jpg

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The E-Manages have a function to do that but it's unfortunately poorly implemented on the Blue - I haven't tried it on the Ultimate. It detects a throttle close and clamps the airflow signal to a user-set value. If you make the value just above the amount of airflow signal you get at idle, it clips the signal at that when you lift off, stopping the ECU seeing a huge airflow signal when the air gets vented, so it fuels for the idle amount instead.

 

Alas it doesn't clip it at that value, it *fixes* it at that value so the car idles like a bag of shite as it sees one constant airflow signal no matter what the engine is up to. What a clanger :(

 

I'm guessing that's how this HKS one works except it clips instead of fixes.

 

-Ian

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This fueling issue does it do any damage or does it just mean the car will not run as well as it should for acceleration/

 

There is potential for damage on a VVTi/Uk Supra due to the MAF sensor, when the BOV discharges the air it will initially run rich, the ECU will then compensate for this and cause it to run too lean.

 

I'd either leave the stock BOV on or fit a recirculating BOV.

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Whats an example of a recirculating BOV, and I dont understand why it has one already but fitting an r2d2 instead will damage it, what is the difference betweeen r2d2 and the stock BOV?

 

Cheers

 

 

The Sard R2D2 BOV vents the pressurised air to atmosphere, a recirculating BOV, recirculates the air back into the intake system.

 

With a MAF (mass air flow) sensor, the ECU knows the amount of air flowing into the engine and so adjusts fueling to suit. If this air is then vented to atmosphere, the ECU thinks there is more air than is actually going into the engine, so you get a rich mixture. The oxygen sensor in the exhaust will then detect this rich mixture and the ECU will lean out the mixture.

 

There is a recirculation attachment available for the HKS SSQV BOV.

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Hi Russ,

 

Just to add my bit (this was my old car)...

 

The R2D2 was taken off by Thor as they were tracing a detonation problem and went back to basics. The problem was a fault FCD in the end. The R2D2 made no difference to power, so it wasn't put back on.

 

When it was on the car, there wasn't any stalling issues or other problems that I could say of. It was purely left off as all it gave the car was a (rather large) noise.

 

Foodfreak once described a stock motor with an R2D2 as sounding like a "mouse farting". On BPU, it is more like an elephant!

 

Anyway Russ, I hope you are still enjoying the car as much as I did, it was a pleasure selling her to another enthusiast.

 

Take care and post up some pics in your garage!

 

nigel

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