Absolute Shower

Any of you tech guys out there know what the max boost a new age WRx will read with std sensor? What happens to boost if it goes over that reading...fuel and injector pulse stays the same? I'm taking upwards of 25 psi once water injection fitted.

Does the STi7 boost sensor read higher and if so, okay to fit WRX - but will ECU need remap for different readings?

john banks

Don't know if this helps, but the 99/00 clips at 25 PSI but if you set the fuel cut to $FF it doesn't fuel cut over this. You can use a Dawes to get higher.

The fuelling and timing are based on "load" which is based on airflow.

The ECUs have a load or flow limit. However, you can always rescale the MAF sensor scaling so that this is not reached until you hit 5V on the MAF sensor, which could be quite high if you use a larger MAF tube or alternatively calibrated sensor. However, you would need to rescale all the maps.

Absolute Shower

Thanks John...I'm running a dawes at the moment, set to just under 1.6 bar, under a Tek3 map set for max boost 1.45 bar. Once, water injection fitted, I want to up fuel cut (using HKS item) and run 1.7/1.8 bar using dawes. The secs monitor at 1.6 bar still shows fuel ratio off the scale but then I'd expect that.

john banks

Beware of the accuracy of the pseudowideband, especially at this level of boost as the consequences of getting it lean will not be funny.

Also if on original pistons, the bore clearance is quite tight and you don't want to nip the bore.

Try to avoid all detonation events at this level. Only advance a degree at a time, and pull back a good margin.

Also unless your turbo is very large at the boost level you are talking about you are likely to have passed the point where you get best performance if you are holding to the top of the RPM range.

If you max out the load reading the injector pulse width will not increase and the timing will not retard.

If you hit the last column on the map the injector pulse width will still increase but the timing will not retard.

Which you hit first depends on the load headings on your map.

It is quite funky to raise the boost by 1 or 2 PSI and then find you have the same IPW and timing. It can produce some quite spectacular detonation events You think you have just upped the boost and the timing will retard and the fuelling will richen when in fact they have clipped.

On the 99/00 there is no obvious warning when this happens unless you log MY99/00 engine load and it will clip at about 52 IIRC. Mine is doing this at the moment through the midrange.

[Edited by john banks - 12/2/2003 2:06:38 PM]

Absolute Shower

Okay John, thanks.

I'll be checking with det cans and knocklink for safety and up the boost slowly.

I've had it run 1.7 bar already in lower gears but not at very high revs...knocklink was okay with that - not over 5,500 revs but the clutch didn't like it!

john banks

The timing you can run in the lower gears can be far more than the higher gears once you get load and heat into it so beware. Just edge it up slowly.

Also measure the power and torque at each step so you can see when you are losing rather than gaining.

It is easy to think you are gaining because the torque keeps increasing well after you have topped out on power. In fact you need to taper the boost or improve the octane.

Also see edited comments in my above post.

Absolute Shower

Thanks John...read extra comments from last...

I've got 3 bar turbo so no problems there - still within performance capacity - it's good for 450 bhp no probs. I'm thinking along the lines of the Aquamist 2D waterinjection - gives same as 3D but runs inline with injector signal - I hope this will control det and allow the boost I want.

I will also monitor inlet temps using accurate probe (within +/- 1 deg) and AFR, etc.

I'll prob head down the road to engine internals but that's not the job for the coming year due to funds.

john banks

Your hand may be forced if you try to run that level of boost, and unless you have changed your gearbox it is on borrowed time.

The WRX heads have small ports with unexciting cams, and you may find it is all boost and no airflow.

You should also measure EGT and be very careful if it goes over 850 with your cast pistons IMHO.

I hope to get away with making this sort of power on an EJ257, but I also have good heads/cams, and only need to use trivial boost to achieve it. Plus the pistons in my engine may be stronger.

I thought I was brave

Absolute Shower

Already have plans for new organic clutch...prob Lateral Performance. Then 6 speed gearbox and rear diff change - the clutch is first as it just wont take the torque and the gearbox already feels like "ruff gears" when driving normally.

What boost do you think the std ports are good for with a large turbo? I'm maybe thinking of getting the 2.5l engine, but that's not next year...maybe the year after.