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The mkiv Supra Owners Club

Restrictor ring.


Chris Bailey
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Just a quick question :)

 

We out with dad the other day for a drive in the supra the car was on low boost but i noticed the boost controller was beeping so i had a look at it and it hit 1.26 bar. Bearing in mind they are stock j-spec turbos, the car is suppost to have a whifbitz restrictor ring fitted but how can it have if its boosting that high on low boost :blink:? Do you reckon its worth fitting a restrictor ring because i dont think the turbos will hold for too much longer if its hitting that sort of bar. Also my dad does have a heavy right foot so that doesnt help the matter.

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Was it a particularly cold day? Air density changes when it is colder which can lead to higher boost levels/spikes. :)

 

Also, if it is a 1.2 bar restrictor ring, it will probably hit a bit over that as the consistency is not always super precise. Fit a 1.0 bar if so :)

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Was it a particularly cold day? Air density changes when it is colder which can lead to higher boost levels/spikes. :)

 

Also, if it is a 1.2 bar restrictor ring, it will probably hit a bit over that as the consistency is not always super precise. Fit a 1.0 bar if so :)

 

No mate it was quite warm - Dad put his foot down on a slight bend then put his foot down again very quickly, Maybe that would have something to do with it.

 

Because when he puts his foot down on a motorway straight it beeps but only hits 1.17 - 1.19 bar on low boost aswell.

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Im not to sure its a whifbitz one, I thought i would off been 1 bar because its a j-spec.

 

Hmmm, prehaps it could possibly be a 1.25bar restrictor ring from who ever had the car previously or was this fitted whilst in your ownership? Is there anyway to tell what it is?

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It may be nothing to do with the restrictor ring. The boost controller will be controlling the amount of boost. You can still get 1.2 bar with a 1 bar restrictor ring. With boost controller off it would / should limit you to 1 bar.

 

Has anyone been playing with the BC settings? Sounds like you have low and high set the same. Likewise you can play with the amount of boost you get.

 

What make of BC is it?

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Paul, and a few other will never sell a 1.2 Bar restrictor ring. There are too many variables in each engine/outside temperature/gear/etc etc.

 

You will have a restrictor ring, that is all, it will/should keep the boost well below 1.2 bar, and the boost controller will raise the boost to the desired level, the b/c cannot lower the boost, so the minimum you can make is what is at the r/r.

 

That should be just enough backslashes for a Wednesday night.

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It may be nothing to do with the restrictor ring. The boost controller will be controlling the amount of boost. You can still get 1.2 bar with a 1 bar restrictor ring. With boost controller off it would / should limit you to 1 bar.

 

Has anyone been playing with the BC settings? Sounds like you have low and high set the same. Likewise you can play with the amount of boost you get.

 

What make of BC is it?

 

We had Adi (letmeshowyou) do the settings for us - Our boostcontroller is very sensitive, Maybe it just needs sorting out again :)

 

The BC is a Greddy profec spec b

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If you have removed the catalytic convertors then you have to fit a restrictor ring, without one you will have no control over the boost and the turbos will peak at 1.5bar+

 

As already said there is no such thing as a 1bar, 1.1bar 1.2bar, etc. restrictor ring, it is simply a gasket shaped plate with a hole in it, the diameter of hole needed to restrict the boost pressure to a certain level will vary from car to car and also with the ambient temps ie. in the winter the car may boost to 1.2bar, in the summer it may only reach 1bar.

 

Try turning the boost controller off and seeing what the boost pressure is peaking at, if it's below 1.2bar then fine just adjust the boost controller so it raises the pressure to the desired amount. If it's boosting above 1.2bar with the BC turned off then you'll need to fit a restrictor ring with a smaller diameter hole.

Edited by Nic (see edit history)
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If you're looking at a peak value stored on the BC's display, i.e. you give it some boot and ease off and then look, remember it is simply a peak. Probably what the boost went up to just as the BC was kicking in to control it. It's a feature of how boost control works.

 

Boost control is an analogue feedback control system, not a digital thing. The displays are dampened and averaged out to make it look accurate and smooth, but really it's fluctuating significantly behind the scenes. You'll easily see +/- a psi or two several times a second. It's really nothing to worry about.

 

If you are consistently hitting over 1.2bar during a pull, i.e. you're observing it while your Dad boots it, then it's just a change in atmospherics and conditions. There is no such thing, as people have said, as a "1.xbar restrictor ring", and your boost controller might have self-learning logic to adapt eventually, but it'll take a few goes.

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