sti_sambo

I recently fitted a Scott.T chip to MY '93 wrx (w9 ecu iirc), performance was disappointing but it ran ok. I then fitted an Sti 5 tmic, after much fiddling I got it sorted, aligned clearanced and looking sweeet. Taking it for a test drive it started being a funny bugger.

When I'm doing around 3-4000 revs and put my foot down taking a second or so to get it near the floor as the revs build (i'm used to carbed engines so my foot is trained into balancing mechanical enrichment pumps on carbs with engine revs) the engine will sometimes just cut at anything from 5-7000 revs for up to half a second or so, the rev counter drops to zero, but the ignition/dash/lights etc all stay on ok.


I noticed on my way home tonight that my boost in 5th gear was around 1.3bar (19psi) at 3/4 throttle and 5000 revs Does this mean I will be hitting the fuel cut? (which is supposedly at 18psi on this chip) I've heard that in order to run this boost level on a phase 1 i need to change the map sensor for a later impreza or a GM one; is this correct? and does anybody know which part number or model fitments they are?


I'm gonna remove the chip and get it mapped properley but would like to know what my problem is before I go on with further mods.

Ta peeps

dan83590

What does Scott say?

sti_sambo

I've not asked him, I suppose that would be the sensible thing to do.

dan83590

Give him a call. I expect the problem will have nothing to do with the chip. Scott will be able to explain what to check and in what order.

Tidgy

a generic map on an impreza causing probs? you dont say?

dan83590

Intelligent reply, nice one!

The map itself shouldn't be causing a problem. More than likely down to a faulty sensor or a poorly fitted aftermarket modification. A generic map assumes that everything functions correctly. A specific map would still highlight the exact same faults, the difference being that the mapper will fix the faults along the way and bill you for it.

Tidgy

lol, sorry couldn't resist, i have little time for the generic maps cos they are advertised as god gift (well cheap version) but they can cause major issues and in few cases i know of rebuilds

dan83590

Depends on the map and the mapper I agree. I've not heard of anyone having any major problems with Scott or Andy's chip.

Tidgy

all i can tell you is i know someone who went down that route and ended up with a rebuild due to AFR, and further to that my old ecu (with a tech 3 map)was placed on a identicle car, my00 with decat and panel filter and even though it ran rich on my car it was running lean on his.

dan83590

Again, that would be down to a faulty sensor.

steveorangewrx

i would look for air leaks on vac pipes or the intercooler piping, these are simple steps to do before anything else. i have not had any experience of these chips myself but i have read lots of praise about scotts so would be suprised if it was that?!

sti_sambo

The reason I'm leaning towards the chip is because the spec says fuel cut at 18 psi and I read 1.3 bar (19 psi) on my boost gauge.

The problem appears to be related to the way I apply the throttle as it cuses the boost to raise higher momentarily (I believe its known as spiking??)

My car shows no fault codes and runs faultlessly other than this.

I would not expect the rev counter to drop to 0 with an air leak, but would not expect the dash/lights/ignition to remain ok with an electrical fault.

dan83590

The ECU will need to learn the new settings, some spiking is normal for the first few hundred miles.

satancom

I have had mine spike a few times recently.. When I fitted mY new coolant pipes i snapped off the connector to the boost solenoid on the airbox.. doh. So i ran for a few days without it with no issues.

I reconnected the boost solenoid and it has cut on me once or twice at around 3000rpm full throttle.. but only when the air temp is cold (engine warm). Im guessing its overboosting and i need to just check the vacume pipes etc.. All time dependant though ug!

steveorangewrx

good point, the rev counter wouldnt drop! unfortunatly that doesnt mean i know what it is either. scott may have better advise.

sti_sambo

I've emailed Scott so I'll see what he reckons.

I'm pretty sure cold air and warm engine has a lot to do with it, my intercooler has been cold to the touch everytime it has happened (but engine was hot).

Scott.T@PolarPerformance

It sounds like fuel cut to me.
If you are bosting much beyond 1.2bar then it will hit fuel cut.
the map is set to fuelcut at approx 18psi but the map sensor is running right at the top of it's range so due to this and tolerances the fuelcut level can be a bit irratic at these boost levels.

it is only mapped to run ~1.1bar (16.11psi).
it is most likeley overbosting due to incorrect boost pipe plumbing and lack of the brass restrictor

see : Boost Solenoid

the rev gauge probably drops due to the ECU cutting both fuel and spark. without spark the ECU is probably un-able to send an Engine rpm signal to the speedo. I've never noticed this as am more concerned about keeping the car mvoing and peeling face off dashboard.

you can fit the later map sensor but this requirs the map to be resacled to suite the alternative map sensor output voltages and hence is something I only do to a live map.

sti 360

iTrader: (1)

hello scott
i was getting error code 45 so found out it was pressure sensor,just as a test i put a u8 in and it is not showing me a error code now but still not going over 0.7 in later gears
matt

sti_sambo

None of the piping from the boost solenoid has been moved/tampered with/adjusted, I'll check it but can't see there being a problem.

The car has only done about 100 miles since the intercooler was changed, is the ecu going to adjust the settings a certain amount to compensate for this? Someone suggested above that it takes 100odd miles to register changes..

Scott.T@PolarPerformance

A larger intercooler will make a minor difference to boost, but only minor.
It certainly won't make it hit 1.3bar if everything else is in place and correct.
Any adjustments will be done within the 1st drive if max boost is aimed at/hit a couple of times.

It's quite common for the restrictor in the boost control pipe to get removed (normally by those pesky Japs's) or even remove the pipe and vent to atmosphere.
This will allow a little more boost but once you decat/chip etc...it causes issues.

sti_sambo

I'll check it tonight.

Boost levels were as follows.

Day 1 slanty intercooler no mods, 0.8 bar

Slanty intercooler, decat, samcos 0.9 bar (samcos made the real difference)

Slanty ic, decat, samcos, chip, 1.1 to 1.2 bar

Sti 5 ic, decat, samcos, chip 1.2 to 1.3 bar

I've not looked at the boost guage too much while the chip has been on so can't give too much accurate info on boost levels.

I did put a small crack in the plastic casing of the throttle position sensor while fitting the samco's (instant gasket and gaffer taped up at the mo), will that make a difference? I've got a new sensor but haven't fitted it because of the adjustment potential on fitment. I assumed its not possible to guarantee the same reading from sensor to sensor so was gonna get it fitted when the car gets mapped for real.

Scott.T@PolarPerformance

It sounds like the combination of modifications you have made has caused the boost to creep upto 1.3bar, which will certainly cause fuel-cut to kick in and your injectors will be topping out.

The easiest solution to this would be to either reduce the tension on the actuator i.e lengthen it (if adjustable, as some are, some are not) or fit a restrictor in the boost control bottom hose that is slighlty smaller i.e 1.5mm instead of 2mm.

This is all assuming that the standard restrictor is still in place.

You mention you are getting another map. TBH with the mods you now have combined with 440cc injectors and a £40 >97 Map sensor it would be better togo for the live map option where you would then be able to run 1.35bar.

sti_sambo

Yeah, thats what I'm thinking. Got the ESL in mind.

Is it a post '97 wrx standard map sensor that I need?

Do you know what size piece of brass I need to make a different restrictor?

Actuator is non adjustable.

Its just the cost of the injectors, getting them flow tested and then getting it mapped thats putting me off. Oh, and I'm still running standard brakes which are insufficient at the best of times. F00kin scary at the worst

Time to empty my garage and have a sale methinks..

Scott.T@PolarPerformance

The brass would need to be just a little greater in diameter then the pipe to ensure a tight fit. Push the old one out and measure that, but probably about 6mm rod.

It needn't be brass anything will do as long as it fits in the pipe i.e nylon, plastic, ally etc....
I've even seen someone use a tyre valve cap with a hole in it, screwed onto the end of the solenoid nipple.

mcphilimey

Im having the same problem, with similar sort of mods. im also hitting 1.3 bar when the fuel cuts. have seen it as high as 1.5bar for a second in 4th gear. would changing the map sensor helkp if it is running at the top end of the range.
have checked i've got the restrictor fitted.