Twiss' supercharger+EFI

[Rhinoman]

250kPa = 2.5bar.

[twiss]

Yeah it should be fine for boosting in that case, don't think I will ever be running 36 psi of boost

[Rhinoman]

Its not 36psi of boost, consider these three statements:

MAP = Manifold Absolute Pressure
Atmospheric pressure varies around 1bar
The intake manifold is subject to engine vacuum.

On a normally aspirated engine:
At idle there is a large vacuum so the absolute pressure is atmospheric pressure - engine vacuum.
At WOT there is no vacuum and absolute pressure is atmospheric pressure

On a turbo on boost absolute pressure is atmospheric pressure + boost

so a 2.5bar sensor can measure 1.5bar of boost when atmospheric pressure is exactly one bar.

[Edweird]

don't think I will ever be running 36 psi of boost

Who are you and what have you done with Twiss?

[twiss]

OK well Im not looking at running more than 6 psi of boost at the minute (otherwise lots of internal engine work required) so 20 psi is plenty...

[Rhinoman]

turbo pressure is gauge pressure its measured relative to atmospheric pressure where 0 = atmos. Absolute pressure is measured from a perfect vacuum. Internally the ECU calculates gauge pressure as absolute pressure - baro pressure.
This is where it goes awry with a stock sensor, which is capable of measuring to 1.3bar, and boost. The ECU knows that under high load/WOT the pressure in the manifold is atmospheric pressure so it updates the baro reading. The reading is checked to ensure that its valid, usually it must be between 0.9 bar and 1.1bar, if it isn't then it can't be atmospheric so the MAP sensor must be faulty and it adopts fail-safe mode until the ignition is turned off and back on again.

[ScottieJ]

Who are you and what have you done with Twiss?

I agree since when did Twiss start to sound like he was clever?

[Edweird]

Who are you and what have you done with Twiss?

I agree since when did Twiss start to sound like he was clever?

Or reserved and not approaching everything flat out, upside down, backwards and on fire.

[twiss]

I always approach everything flat out

I will probably end up upside down one day, I will probably end up wiring the whole thing backwards and set the garage on fire.

Happy now?

Rhinoman... the MS ecu doesn't even have a fail safe mode but it can definitely handle the 2.5 bar sensor
Do you think its worth setting the ECU to adjust for ambient air pressure changes every now and again or just on start up? I can understand this if you are driving up a mountain, but I can't imagine the air pressure going up and down enough to cause much of a problem...

I think the most annoying part of the thing will be getting it to start in the first place, apparently it can take a little bit of playing around with the injector open time to get it right!

[ScottieJ]

Hang on all Twiss does flat out is drive....everything else takes forever

I'll be impressed if this engine is done by 2015