Subaru Impreza STi Version 5 1998

[rob@vems.co.uk]

So heres my new project.

Dyno figures: 291.9BHP@6569RPM  276.6lb/ft@4706RPM

Uprated shocks and springs, HKS headers and exhaust and a free flowing airfilter.

Mods I'm planning to make:
Aquamist water injection.
VEMS ECU - on a plug and play harness.

[gunni]

Reason for the water injection?
Can it not run MBT without it?

[rob@vems.co.uk]

Anti-detonation insurance for running high boost - plus I have an Aquamist setup - so its silly not to fit it.
I can use the v1.1.4x warning trigger to fire the water if the EGT or IAT rises too much.

[Denmark]

Nice Impreza you got your self there 


I look forward to hear if the pnp harness is going to work


/Skassa

[Sprockets]

Agreed, nice car there!  That would be the only Impreza I would own, and the prices have fallen enough to be able to have one as a 'toy'.  I got fed up with them a while back as it seemed every week I was building an engine for a customer that had knocked number 3 big end out, or melted the piston due to too much boost and not enough fuel!  Amazing how cheap the bottom ends from subaru became because of it!!  Was cheaper to do that, than rebuild lol.  Although, I built a few 2.5 litre STi lumps.  Very nice with a good turbo behind it.  Anyhow, I'm rambling.

Enjoy your new toy!  Gonna do any events/racing with it?

-Gav

[Denmark]

 

I´m also up to my ears, in broken Impreza´s, building engines all the time....

[rob@vems.co.uk]

What breaks on them?  Why does big end number 3 go?

[Denmark]

The ringlands on the pistons break on the slidest det, but not so much on a sti model,
I belive it´´s knock the kills the bigends, and that it´s closely related to lean fueling, caused by both failing maf sensor,
or to lean afr´s when mapping, becourse of bieng used to map toyta and nissan, which can run leaner, without trooble......


/Skassa

[rob@vems.co.uk]

It got a new MAF element before I bought it - I was amazed to see that they go bad as quickly as they do...
Still a nice Speed Density system will cure that nonsense

Rob

[Sprockets]

Sorry for the late reply, but yes, Denmark was right.  Det is the root of all evil   Number 3 is the hottest cylinder on the scoobys so is the first to cry enough! Allied to the fact super unleaded is not normally the owners first choice at the pumps either, recipe for disaster! The STi's are better as they have tougher internals and the bigger intercooler.  Not many people do it, but I believe front mount intercooler on these is a one of the first things that should be done, but as you say, you have an aquamist kit anyway, so all good

-Gavin

[Denmark]

My vote for a first upgrade , would be the fuelpump a nice and cheap Walbro pump

And a lesson to the owner, that you newer ever beats the car from a stilstand, were the IC can be heatsoaked, as the cooler works really great, but gets heatsoaked, when waiting for the greenlight,
Its nice to try to measure the temp in the ic, so you get a feeling how long/fast the ic if heatsoak free


/Skassa

[dnb]

The STi need not be so bad for heatsoak making det - there is an air temperature sensor in the intake intended to pull out timing when things get warm...

Agree that a walbro 255 l/hr pump is a good (almost mandatory) first step.

Also, you'll need to consider getting rid of the 2 port boost control solenoid - it's a nasty way to do boost control, and the Subaru solenoids are quite slow acting.

[GintsK]

Newest firmwares have ability to reduce boost when IAT cross defined margin.

[Denmark]

Rob,

Did you get any futher with the impreza?

I have decided to give the vems with oe trigger a new try with the Type R i picked up,
 but this time, knowing that the vems software cant work in a car, we will make a adaptor stick in board to make the vems run 4+1 trigger setup,
That is still using the oe trigger wheels, but make some electronic that make the vems see a 4thooth primary wheel and a 1tooth secondery trigger wheel.

and the have the software run it like a 4+1 instead of the subarutrigger,that doesn´t work when cranking.

I allready have a small board that does this,
2 trigger input, 12v suply ,ground, and 2 trigger outputs,
Then we hope this can be made to work, so the VEMS can be used in a Impreza without the need for :
full moon, planet mars needs to be a special place, and no lower then 15 degrees, and a big chunk of luck, for the car to be able to start 
 

/Skassa

[rob@vems.co.uk]

I've done nothing with the car and am considering selling it.
I'll be interested to see how you get on with you trigger setup.
I still have a load of the Subaru ECU connectors