911

Have a Blitz boost controller set by Powerengineering @ 1.2 Bar. How much further can I go before getting the Fuel cut coming in?
I do know I will get cut at 1.6 bar as this car had that problem.
The motor is standard except for a turbo back Magnex system.
I'm getting 314 bhp @ 1.2, and need a bit more!
Graham

john banks

The V5/6/P1 cuts at 1.35 bar. Can't see the V3 being higher than this since it runs a larger exhaust housing so should make more torque at the same boost and the claimed outputs are similar.

If the fuel pressure is staying up, your AFR is OK and your injectors are not at silly high duty cycles, plus you are monitoring and controlling detonation by mapping the ignition, and the charge temps are sensible your car could run quite well at 1.3 bar. However, this will not happen by accident, and it will probably det otherwise if you haven't sorted these things out.

[Edited by john banks - 4/18/2003 8:14:08 PM]

911

Thanks John. When Power Eng set the Blitz Mervyn said the injectors were at the limit, 1.2Bar was about right and all will be safe.
I race the car in hill climbs so for a minute or so things are very frantic in race trim. Last year raced the car with the standard STi full cat system, no Blitz ans drove around the fuel cut at 4500 rpm. this was all at 1,6 bar and I presume the fuel was ok as the car went really well! No bangs rattles and detonation, just hard accelleration.
Better save than sorry...
Graham

WREXY

Also the VF23 turbo on your car ( standard on Version 3 STIs) will blow up at 1.6bar. The VF23 wont handle that much boost.

Anyone know what the actual limit for boost is with a VF23?

Cheers,

Wrexy.

john banks

I've not seen a plot of a VF23/24/28/29 compressor before with load lines on so I thought I would do it for an EJ20. I assume 90% VE from 3000 to 7000 RPM as a guess to be honest.

The lines are for each RPM and I put a black blob at the top of the map, so read off on the Y-axis the pressure ratio for each black blob and it tells you maximum pressure ratio across the turbo. Subtract one from this and you get boost in bar, but then knock off say 0.1 bar for losses in the system (mainly across the intercooler), this then gives you estimated maximum manifold pressure by RPM:

3000 1.35
4000 1.4
5000 1.3
6000 1.1
7000 0.85

If you change the assumptions with the spreadsheet I previously posted you obviously get different results.

Here is the VF22 BTW.

3000 1.55
4000 1.9
5000 1.75
6000 1.4
7000 1.0

[Edited by john banks - 4/20/2003 9:54:19 AM]

WREXY

Thanks for that John.

Does this mean I should be running under 1.1 bar after 6000 rpm for safety issues then?

Cheers,

Wrexy.

john banks

Depends on what VE you use On a VF23 the turbo is well setup so rolls off at the top end safely enough of its own accord. From what I hear the VF22 will just hold it quite easily and overspeed.

WREXY