eddhead

Hello all,

I would like to know what the ECU is doing when the boost gets to high (i.e. on over boost after modifying the boost restrictor).

My modified 1999MY oscillates 2-3 times between 0.9 and 1.2 bar boost before settling at a constant 1.1 bar when flooring the throttle in 5th gear @ 3000RPM.

Bottom line:
Is this behaviour just annoying or will is cause any damage?

P.S. What does the MAP sensor do and where is it connected?

Thanks

Edd.

john banks

Boost spiking is a contributor to detonation, but at this level of boost it is more likely to be a PITA to drive rather than harmful.

The MY99 ECU has a 13.7 PSI boost target and has a look up table for +3, +1.7, +0.8 and +0.3 PSI and will reduce the solenoid duty cycle by up to 12% to bring the boost into line. Therefore altering the restrictor does little except giving you a peak unless you are not running enough boost to start with.

The MAP sensor is mounted near the offside suspension tower with a switching solenoid before it to read atmospheric pressure. The feed is from the manifold. Unplugging and sealing the manifold feed will disable fuel cut, but it is not safe.

The best solution is an HKS FCD which can raise your fuel cut or if you are handy with a soldering iron you can build your own - I and others described circuits in the drivetrain forum.

A Dawes manual boost controller will allow you to boost up to theh 17.6 PSI cutoff - best to install it to 16.5 PSI so that you don't get a fuel cut surprise in a high gear on a cold day.

Best of all, really is a remap where you can also gain from adjustments to fuelling and timing. This means not going silly with the boost but hitting the sweet efficient areas of the turbo compressor map and making use of appropriate fuelling and advanced timing to develop safe power with good thermal management. See my profile for more info.

Since this is not a commercial board, I should also mention that there are other excellent remapping products which I do not have a commercial interest in - Link ECU in particular is nice because you might like to map it yourself.

Iain P

Hi, John,
what would you consider a reasonable level to increase the fuel-cut to on standard ECU with Dawes and SUL?

john banks

Fuel cut 19.6 like the PPP and Tek2, but run 2 less than that.