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237-inlet restrictions with turbo restrictors

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Hi guys,

I'm in the process of building a turbo 13b race motor possibly with a gtx3582 for the improved production category in Australia, and we will have to run close to a 36mm pre turbo restrictor about 50mm from the compressor wheel

As I understand this will create a vacuum pre-turbo and thus result in needing a higher pressure ratio to maintain the same boost/power levels; similar to a higher altitude

Is there a way to accurately log or track the restrictors effective barometric pressure to see what changes to the design are beneficial and get a better idea on where the turbo is on the compressor map without using a wheel speed sensor?

Also is there any way to calculate the maximum flow that such a restrictor will allow?

Thanks for any assistance

why don't you just plumb in an absolute pressure sensor to the turbo inlet area (post restrictor). That would allow you to log the pressure. Why wouldn't you want a turbo speed sensor as well. Info is good. More info is better...

I'm really new to all of this so this might sound dumb but would a map sensor that close to the compressor wheel be a reliable source? I would have imagined that the pressure should be a constant depending on the wheel speed but could It possibly create a false vacuum as it is so close to the compressor?

And the speed sensor: we will likelly be using a gtx35 chra but not in original housings, coz I do everything possible myself and still learning I'm trying to keep it as simple as possible. I think the speed sensor would be the best option as I would then be able to accurately map the p.r. based on speed and hp/air consumption

Hey Mathew,

I agree with David, running a speed sensor is (Imho) critical when running with restrictors.

I haven't had my morning coffee to comment on turbo sizing but, choke points are always an issue with a restrictor, this is why a speed sensor is a must as when you reach choke the air flow can not increase but the turbo speed can which in turn let's the turbo over speed which can cause damage!

Fitting a pre compressor pressure sensor can be useful information as well as you say a map sensor or again a more accurate pressure sensor as David says also.

Excuse the UK site but this is the type of sensor we are taking about:-


I hope this helps, keep us up to date on how your getting on!

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