stevekoz

iTrader: (1)

Hi - wondering if anyone can offer a helping hand.

I have developed the following issue -

1. The Car - Subaru Impreza 2000 UK MY00 (V reg) 92380 miles

2. The Modifications - Decat Downpipe. Straight through s/s 1 piece centre section with 200 cell sports cat (metal not porcelain so won't break down). Afterburner Panel Filter (dry not oiled)

3. Recent Problems - Dodgy service - bad plugs n leads. Rescued by Mark at Thwaite Developments - swapped out 02 sensor, new plugs.

4. The Problem - Yesterday morning accelerating past 60mph had slight teeth chattering jolt at about 4.5k revs. Dissappeared almsot immediately after backing off a bit. On teh way home, car seemed to drive fine - in fact seemed v.responsive. Got home no issues at all. Took her out later thaqt night to fill up (99ron) and on way back from accelerated hard and another far more teeth shattering jolt. Backed off, accelerated a little less hard, same problem again at roughly 4.5k revs. Car felt lurchy not as smooth either even on softer acceleration. Felt lurchy this morning also (daily driver and only car so can't not be in use)

5. The causes? Well this is where i need your help - i get that its probably over boosting and causing the fuel cut off defense to kick in. But i wonder why? Could the modificaiton of a decat downpipe be causing it despite the fact i still have a cat in place on the mid section?

I've also heard it could be the cold weather (how?) but is there anyway to stop it happening asides paying for an expensive remap i can ill afford? Would putting the car back to standard(ish) ie swapping out the exhaust for a standard downpipe and then catless centre section - would that stop her from doing it, if thats what it is? Any other ideas to help - quick fixes etc?

cheers

Steve

scoobyride

iTrader: (8)

most, of us will be having similar problem with overboost this time of the year due to the cold weather its normal for subaru's! hitting the fuel saftey cut isnt a bad thing at least u know the car is safe and its doing what is designed to in these cases! As for ur decat downpipe you will have overboost after fitting this thats why you really should have it mapped for it! you can put the decat centre pipe on without an issue, although there is many running a full decat without issue! You could just be unlucky in this case. imho i would remove the decat downpipe and refit the standard 1 asap! cause if you cant afford a remap for it then ul not be able to afford the engine rebuild when it happens

Glowplug

iTrader: (8)

Contradictive post!


Decat is the cause, remap is the solution

You could fit a MBC to cap the boost until you get the remap done

Do you have a boost gauge fitted, what is it boosting to?

stevekoz

iTrader: (1)

I don't have a manual boost controller fitted no, i could get a dawes one for about 40 quid i think, but to be honest until i can afford the remap may be best to put it back on the hold catted system yes? better safe than sorry?

I understand as its an MY00 i can only really get a standalone ecu or an ecutek remap so between about 650 and 1700 depending on which option i go for yes? Any recommendations there?

Cheers for the replies lads.

steve

Glowplug

iTrader: (8)

Personally i would and have fitted a Dawes to cap the boost on my MY93 due to the same-ish mods and overboost problems as yourself and all is well, the another advantage of the Dawes is that it holds the boost back better than the OE BCS so giving a quicker spool up and holds the peak better

Perhaps get the fueling checked after fitting the Dawes just to make sure it's ok.

Splitpin

It isn't relevant to your problem as 99 and 00 are effectively the same under the bonnet, but for the sake of factual accuracy, if your car was registered on a V-plate, it is unlikely you have an MY00. If it is a GC8G... applied model code you have an MY99.

The bit in bold there is a bit of a warning sign so caution needed here. Can you describe the jolt in more detail? Was it one distinct and sudden power loss that appeared without any warning and immediately remedied, or...?

As the others have said, this is probably the combination of cold weather and the decat. However you should not take that assumption as fact without checking out a couple of other potential explanations/contributing factors.

Colder inlet air temperatures make your turbo develop boost quicker and more efficiently. The UK specification ECUs don't have an inlet air temp sensor and therefore are unable to modulate their boost control to keep it consistent through changes of air temp.

Yes. If this is simple overboost, you can solve it very simply by drilling out the restrictor pill in the boost control pipe between the turbo compressor bleed outlet and the t-piece. This will cost you a handful of quid for some small drills and a pin vice to hold them (assuming you're not already equipped).

However, all that said, the emergency fuel cut threshold on the standard grade MY99-00 UK ECUs is 1.22 bar, as against a boost target of 0.94 bar. If you are hitting cut you are overboosting by some 30%, which would be unusual, even with a full decat in cold weather, so it'd be well worth having a look for any other influencing factors before assuming the cause has been identified.

If that's what it is, the best way forward is to drill out the restrictor as outlined above. You get to keep the decat and get your boost back under control.

Manual boost controllers are tuning devices, not problem solving devices, and fitting one when you know you have a problem (but are not 100% sure what the cause is) is often a recipe for tears further down the road. Ideally you want the ECU in charge of setting boost, as at least then it has the ability to shut things down if it thinks there are problems.

You really need to establish right now whether there are any other potential causes for the symptoms, other than the "decat + cold weather". The one you really need to rule out is an under-reading airflow sensor - and that's why I flagged your comment earlier about it feeling "v. responsive". If you don't have any onboard monitoring devices, it would be well worth you popping back to Thwaites and asking them to take a quick look at it, in particular monitoring the air flow meter output under load.

Would also be well worth visually examining or pressure testing the boost control pipework to make sure there are no splits. While doing that I'd have a look at the pipe that runs between the inlet manifold and the fuel pressure reg as well, as I've seen one or two that have split where they bend at the top.

The one thing that is certain right now is that you don't need an aftermarket ECU or a remap to solve this problem. If it's just overboost, then the fix is drilling the restrictor a little, with the tools probably costing you less than a fiver. If it's being influenced by a degrading airflow sensor, then a new one will cost you about £100, but that's a hell of a lot cheaper than fixing a blown engine.

stevekoz

iTrader: (1)

Hey thanks for the really involved reply - appreciate the time and effort you've taken. cheers.

As you say the model number is really irrelevant , i thought it best to give as indepth explanation as i could so thought some people may question what car it is. To be honest she is on a private plate, i think i got the reg wrong as its definitely logged as a 2000 on the v5.

Anyway.

To your points - the jolt was a very distinct and short lived loss of power. like when you stall a car violently. No warning at all. No engine warning lights and was running fine before then.

As i say she did seem to be running very well before - which as i understand your reply could be bad and to be honest, having replaced my last Maf (August). Thought it may be wishful thinking the maf would last a bit longer than 4ish months. But as i understand it is possible definitely.

I do get that there may be other contributing factors as i can't believe im overboosting by 30% that is a hell of a lot really considering the only mod is the decat!

As you recommend i will be trying to get the car to mark as soon as possible and i've emailed him . When i speak to him i'll be asking him to test as you have recommended.

If it is indeed any of those causing the problems then like you say an expensive rebuild is something i definitely want to avoid which is why i thought it relevant to ask people and put a post up in the first place - thought it best toask those more in the know than myself having only had a scoob for 6 months but i'm certainly learning fast!

In respect of the boost controller - would it be wise to fit one once the problem is fixed- as a safety measure perhaps? I really don't understand how they work so if perhaps you could explain that would be a good help - i like to be fully armed of the facts before i tend to try anything on any car i own.

Cheers once again guys - appreciate the help!

Splitpin

Not totally. If this troubleshooting process gets a bit more involved we may be wanting to know which ECU you have, and in this area the 99 and 00MY cars are different.

The "2000" on the V5 will almost certainly to do with the car's model name, which is "Impreza Turbo 2000", as opposed to the reg. Anyway...

That does sound like fuel cut.

It can be a bad sign, but isn't always so be aware of, rather than worried by it.

Oh hell yes. Assuming you have a genuine Subaru supplied sensor and you haven't got anything that will degrade it overly quickly (induction kit, dumpvalve delete etc) then it should be fine. However it's better to know than assume.

Question: Are you sure you have a standard car, or is it possible (if you bought it secondhand) that you have a PPP? These can be easily upset simply with a decat. If there's any doubt have a look at your ECU and tell us what colour the label is.

Not as a safety measure no. The safest way to control the boost is to let the ECU do it.

The cheap mechanical ones are usually nothing more than a valve consisting of a ball bearing with a spring pressing against it, and a method of adjusting the preload on the spring. Boost pressure bears on the ball bearing, and when it exceeds the pressure of the spring, will open the valve and supply air to the wastegate.

Very simple and can be very effective, but also lacking the finesse and adjustability that an electronic method of boost regulation can offer.

stevekoz

iTrader: (1)

I wll check the type of ecu tomorrow in the light and the V5 but i was referring to the section on being first registered, i believe it may state the year there, and having looked at the previous old MOT's it states 2000 too as the year registered.

Ah right ok - thanks for that explanation of the boost controllers. I understand more now. So an electronic one is always better in that instance.

I did buy the car second hand and i wasn't made aware that it could be a PPP. If it is a PPP will the ECU label be a different colour im assuming?

Let us assume its not a PPP for the moment (only an assumption). What could cause her to overboost so much - i mean basing on the figures of the boost, 30% would be one hell of a lot, what could cause it - any ideas?

Splitpin

Does it have body colour mirrors and doorhandles, and a pair of map lights in the roof lining behind the mirror? If so, MY2000.

It probably isn't - as under normal circumstances the seller would advertise the fact as it increases value. However, it's worth a look as if it was, you've probably got an explanation for the overboost right there.

Yes, PPP is pink, standard are black, brown or green.

Range of things. Common one would be boost control pipework full of oil secondary to overfill. Beyond that, sticking solenoid. Would be handy to run a boost gauge in the car so you can get a better idea what's going on.

stevekoz

iTrader: (1)

This may be highly likely. THe reason i had to go and see Mark @ TD in the first place was because i got a CEL light caused by a faulty 02 sensor. The 02 sensor was knackered we thinking by dodgely gapped unsuitable plugs by the garage that did the last service - the also changed the leads which aren't that great (swapping out this weekend) and changed the oil. Now i know for afact that they filled it up with about 5ltrs of oil so if they did indeed overfill it then this could explain the the boost issue.

Obviously its just a theory at this stage but its somehting i can start with and clean the pipework - understand its an easy enough clean, just connecting the green connectors under the steering column and turning car to full ignition without starting - disconnecting the pipework and sprayin with brake cleaner or similar?

stevekoz

iTrader: (1)

ECU is standard not PPP and green so no issues there.

I have cleaned out the boost solenoid and so far no issues with overboost - however, it was already and intermittant fault so no real way of knowing if thats cured it or not.

I think what i may do is lengthen the actuator arm so that its making that liittle bit less boost during this colder period and then can change it back again come summer time. This has been some advice given from a very trusted source. So will be doing that this weekend.

I have also been reading that drilling out the current restrictor pill by abotu .5mm at a time may help stabilise boost without any other adjustments. I have ordered a few pills from my local dealer so i have spares just incase and i'll give that a go at the weekend.

As for MAF - i swapped this out again over the weekend with one i know was absolutely knackered. Ran really rough just on idle and then replaced my current MAF back in and its fine - also cleaned this at the same time as the solenoid and it seems a bit healthier. I think i'll order a new one to come too just incase mine is beginning to degrade as its hard to tell when it first starts going wrong i understand and better safe than sorry.

Thanks for your help all on this issue - will let you know how the results go once i've tried all the suggestions.

Splitpin

If you've cleaned all the pipework out, the most sensible next step is either to simply leave it and see if the problem recurs (and take action if and when it does), or to fit a boost gauge and therefore be able to see what's going on (and hence know what the boost is doing).

I wouldn't do that, certainly not at this point. Aside from anything else, lengthening the actuator arm won't help under a wide range of error circumstances, and also, lengthening it doesn't directly reduce the boost target, which is the basis you seem to be working on. Plus if you don't have a boost gauge you'll have no idea whether your adjustments are making any difference.

Yes - this was mentioned further up.

No! Order of magnitude error there. Drill it out by 0.05mm at a time. Go straight from 1.2 to 1.7 and you'll be down to actuator pressure.

This is worth trying - certainly moreso than the actuator arm thing. But, you can't do either properly without a boost gauge as you have no idea of the scale of the problem and how much of a difference your changes are making. Given what you said up top about the problem not having recurred, it would be folly to take any further steps to try and control the issue until you know whether it's still there.

This doesn't unfortunately tell you that much, other than what you already knew about the old sensor. Just because the car idles okay on the newer one, that doesn't guarantee that it is reading correctly under high flow.

Define "healthier". If you mean the car feels livelier or faster, in the absence of the ability to monitor the sensor directly, it's safer to assume that's a bad sign rather than a good one. Cleaning the sensor shouldn't be necessary and shouldn't make make any difference at all if you have a good air filter, as it should prevent the passage of anything significant enough to coat the sensor.

Ordering a new one is the safest way forward, because, as you say, it's much better to be safe than sorry.

stevekoz

iTrader: (1)

wow 0.05mm - how the hell do i get a drill bit that small, lol, smallest i've seen is 0.5mm and thats a modelling drill bit from maplins, i haven't seen any with a 0.05mm size - wondered where you could one that small (should i decide to go down this route)

In terms of the MAF yes, your probably right it does probably point to very little other than i've proven the original MAF was knackered. However, like i say, law of averages i'm ordering a new one just incase mine is currently starting to degrade. That said, i thought it best that whilst it was out i would clean it - very fine light spray of fluid and like i say, on resetting the ecu and refitting the MAf it doesn't feel like its "too Healthy" if you get my meaning - it feels normal again, but that could be down to the fact i've cleaned out the boost pipework and that was having an adverse affect. Anyhow spare is ready and waiting in the wings should i need to bring it off the bench.

In terms of lengthening the arm - i trust the person whom gave me the advice as he's well known in the scooby maintenance and tuning in the West Mids if not further afield. However, your right without a boost gauge i'm tinkering with no idea of what is working and what isn't.

So come Saturday i'll be having my gauges finished so i'll have a fully functioning boost gauge to help me out come Sunday in fiddling with these few things should i choose too.

Back to the pill - well I picked up the restrictor pills at lunch, not bad at £2.94 each. However like i say how is it possible to add 0.05mm to it at a time - thats almost unmeasurable to the naked eye surely and as i say where can you get that small a drill bit from? Have you tried this yourself and if so how did you manage it?

I suppose in essence your right, doing anything further would perhaps be unnessecary if the problem hasn't reoccured, but that said, its difficult to know as i've not really given her the beans since the fuel cut simply as i really didn't like the feeling it left me with - so i've been more cautious and that may inturn be giving me the false positives of it not reoccurring. I suppose i'll have to bite the bullet and give her some throttle at some point and see what happens. Fingers crossed no fuel cut and if so then i'll try the restrictor pill mod as the next stage and go from there..

Again thanks mate on being so helpful and talking through these issues - good that someone is willing to help out so thoroughly, i mean if this helps fix my problems then its going to undoubtedly help others in the same situation.

Splitpin

Not sure we're understanding each other properly there, but so there's no doubt, you don't get a "0.05mm drill", you enlarge the orifice by 0.05mm at a time. So, you start with a 1.20mm, drill it out to 1.25mm and try it. If it's still overboosting, you drill it out again to 1.30mm and repeat as necessary.

Buying small drills like that should be no problem - think Maplin used to do a set that went from 1 to 1.6mm in .05 steps. That'll do you fine.

There's no point doing anything else until you have a boost gauge fitted. Otherwise you're mucking about in the dark.

Not a bad profit margin for about a penny's worth of brass! You shouldn't really need more than one (standard) fallback spare anyway. If you start small and drill out a bit at a time, you just stick with the same one until you get the size right.

If cars were built with tolerances that could be measured by the naked eye we'd never have got beyond the Model T! You can measure small drills with a micrometer easily enough. By going from 1.2 to 1.25mm you will be allowing over 8% more air into the boost control system. By the time you get to 1.35 you have increased the flow by 27%. You have to make small changes otherwise you'll go too far, waste all your restrictors and still won't get it right.

If you can't find the right drills at Maplin, try a local model shop or engineering supplies place (see if there's a Monks and Crane in your area).

The answer to that is simple. Wait until you have your boost gauge fitted and then give it full tread. If you can see it's only boosting to a bar or just under, you know it's now right, and can stop worrying. If it isn't you can go forward from there. Either way, knowledge is your friend.

stevekoz

iTrader: (1)

Well its been nearly over a 10days since last posts.

Preceeding that i had cleaned out the boost solenoid its definitely helped.

However, i have gone ahead and widened one of the restrictor pills i got from my local scooby dealer.

One set of micro drill bits from Maplins at a cost of 10.99

The standard restrictor diameter i believe is 1.2mm, I had a 1.2mm drill bit and to be honest the fit was really really tight, i had to push to get it through so i'd say diameter was more like 1.18 ish. I used that 1.2mm drill to widen it out a little, id say to no more than 1.23mm - we are in finite amounts here and refitted it and took her out and gave her the beans. Much much better. No overboost or fuelcut and car feels smoother.

I have orderd a new MAF as i think it could be a contributing factor to the hesitation i felt and the moments of "really good" running - as it may be under reading.

So fingers crossed. Overboost issue solved.