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Intake restrictors tuning

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I have zero experience with them , is having a restrictor in the air intake before the turbo something to keep in mind while tuning ? or will it just perform like running out of turbo while on the dyno ?

i've had some thoughts about it but like i said never tuned one with it.

If you just tune it as it is, and don't worry about what it is, you should be about right. Just make sure the restrictors, filters, and everything else, that will be used are in place.

Depending on your turbo setup, there is no point in my experience to ask for to much boost once the choke point has been reached. I have seen guys running 100% DC on the boost solenoid at high RPM after the choke point and the dyno shows it was just not helping at all. As a matter of fact, the IAT's were too high and power was being lost.

If you got a turbo that is designed to be ran with a restrictor, you migh be able to keep the torque curve flat after the choke point. That will generally not happen with an OEM turbo that was fitted a restrictor.

thats something i was wondering about , dropping DC on the gate after the choke point.

Thinking about it i would assume you go downwards in the compressor map after the choke point ?

Hi Kenny,

if you have to use a restrictor in the system for regulations it’s a good idea to have at least one turbo speed sensor (2 ideally) to monitor the turbo as once you go into choke the turbine speed will shoot up! And this can cause a lot of damage if the turbo is span past it’s balance point and has the ability for the compressor or turbine blade to meet the sides of the housing.

Once you hit choke the point at which you do in the turbine efficiency map will stay pretty stationary (please someone correct me if I’m wrong - I’ve only worked with speed controlled systems)

No more air can pass through the choke point, this is the limit.

If your compressor housing doesn’t have anywhere to physically mount sensors you should be able to find a turbo rebuild company that can machine these sensors in for you; they are not the cheapest sensor to implement but when it comes to choke boost tuning I would personally say a must.

Hope this helps.

I have tuned many top rally cars in New Zealand where the restrictions are 36 and 32 mm as mentioned above don’t push or try to push past Choking point unless your prepared to change the turbo during a rally/race

an old tuner/ top nz driver many years ago came and used my dyno and taught me how to get the best out of my customers cars the best advise he gave me was don’t over try to make power don’t ramp the turbo in too hard first to finish you must finish. My customers went in to win national titles

Just as another random bit of info;

OEM manufacturers spend a lot of time looking at the restrictions in an intake system and on the dyno replicate and test different restrictions of systems. They start well clear of choke as the cars have to do over 150k miles to an engine (this is deemed lifed)

Ross out of interest; did your rally customer life his turbos and have them rebuilt/inspected? Did you run turbo speed strategies?

In wtcc we lifed the turbo around 1200km so went through a few of them each year; these ran different restrictors depending what championship the engine was running in.

Ah, sorry, I misunderstood the query.

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