[Mk2] [Turbo] Rev3 Turbo fuel cut

[rob6539]

Hi there guys

Does anyone know the psi boost limit that the ECU will initiate the fuel cut, in order to protect from over boosting, on a rev 3 turbo?

Second question is probably a little bit trickier! At that magic psi level, does anyone know what voltage the boost sensor will be sending to the ECU? I've heard it's 4.4 volts, but I tested it over the weekend and I was sending around 18 psi to the sensor (with an air line, not whilst driving!!!) and the voltage I measured was just below 4 volts.

The reason I ask, is that I'm setting the engine up to be fitted with a boost controller and want to try and avoid hitting the fuel cut wall people often mention. I'm not looking for large boost levels, possibly 15psi.

As ever, any advise or knowledge would be very much appreciated.

Thank you

[Ryan S]

Hi there guys

Does anyone know the psi boost limit that the ECU will initiate the fuel cut, in order to protect from over boosting, on a rev 3 turbo?

Second question is probably a little bit trickier! At that magic psi level, does anyone know what voltage the boost sensor will be sending to the ECU? I've heard it's 4.4 volts, but I tested it over the weekend and I was sending around 18 psi to the sensor (with an air line, not whilst driving!!!) and the voltage I measured was just below 4 volts.

The reason I ask, is that I'm setting the engine up to be fitted with a boost controller and want to try and avoid hitting the fuel cut wall people often mention. I'm not looking for large boost levels, possibly 15psi.

As ever, any advise or knowledge would be very much appreciated.

Thank you

you can run 17.5PSI safely, I think (i'm sure i'll be corrected) that fuel cut is 19PSI on a rev3+

[rob6539]

you can run 17.5PSI safely, I think (i'm sure i'll be corrected) that fuel cut is 19PSI on a rev3+

Oh right, that's a lot higher than I anticipated. My engine and turbo are stock, but I've got a larger Greddy style intercooler and free flowing air filter and exhaust system. Will be fitting a set of cold grade spark plugs as well, in anticipation of the boost increase.

Thanks for such quick response

[Peter Gidden]

Hi there guys

Does anyone know the psi boost limit that the ECU will initiate the fuel cut, in order to protect from over boosting, on a rev 3 turbo?

Second question is probably a little bit trickier! At that magic psi level, does anyone know what voltage the boost sensor will be sending to the ECU? I've heard it's 4.4 volts, but I tested it over the weekend and I was sending around 18 psi to the sensor (with an air line, not whilst driving!!!) and the voltage I measured was just below 4 volts.

The reason I ask, is that I'm setting the engine up to be fitted with a boost controller and want to try and avoid hitting the fuel cut wall people often mention. I'm not looking for large boost levels, possibly 15psi.

As ever, any advise or knowledge would be very much appreciated.

Thank you

you can run 17.5PSI safely, I think (i'm sure i'll be corrected) that fuel cut is 19PSI on a rev3+

I would rephrase that to "many people run 17.5 psi".

[Ryan S]

Hi there guys

Does anyone know the psi boost limit that the ECU will initiate the fuel cut, in order to protect from over boosting, on a rev 3 turbo?

Second question is probably a little bit trickier! At that magic psi level, does anyone know what voltage the boost sensor will be sending to the ECU? I've heard it's 4.4 volts, but I tested it over the weekend and I was sending around 18 psi to the sensor (with an air line, not whilst driving!!!) and the voltage I measured was just below 4 volts.

The reason I ask, is that I'm setting the engine up to be fitted with a boost controller and want to try and avoid hitting the fuel cut wall people often mention. I'm not looking for large boost levels, possibly 15psi.

As ever, any advise or knowledge would be very much appreciated.

Thank you

you can run 17.5PSI safely, I think (i'm sure i'll be corrected) that fuel cut is 19PSI on a rev3+

I would rephrase that to "many people run 17.5 psi".

Peter is correct, these engines are 20+ years old now so realistically anything could happen at any level of boost, but many people (myself included) run 17PSI without issue.

[jon]

http://gtfour.supras.org.nz/mapsensor.htm shows the relationship between manifold pressure and voltage.

[rob6539]

http://gtfour.supras.org.nz/mapsensor.htm shows the relationship between manifold pressure and voltage.

That is spot on Jon, thank you.

Can anyone confirm at what pressure my ECU will initiate fuel cut? As I've been reading some pretty conflicting answers online?

Thanks again all

[Peter Gidden]

As I've been reading some pretty conflicting answers online?

As already stated on this thread, 18psi ish. It is quite normal for exact manifold pressure needed to vary slightly from car to car as sensors etc. age.

[rob6539]

As already stated on this thread, 18psi ish. It is quite normal for exact manifold pressure needed to vary slightly from car to car as sensors etc. age.

Cheers Peter; and thanks Sheppy for giving me this value earlier. I made the mistake venturing out onto google, when I should have known by now all the info I'll ever need on 3SGTE's should come here!!!

Thanks again all, I feel that I'm pretty well armed to continue the built.

[jimGTS]

Fuel cut doesn't hit on mine until over 1.3bar

1.33ish last time.

[jon]

Fuel cut only occurs if the manifold pressure exceeds the ~18psi limit for 400ms or more.

So depending on how quickly pressure is rising during the 400ms, fuel cut can occur at pressures quite a bit higher than the nominal 18psi limit.