john banks

Having gone back to a MY99 ECU (AE801) before other mods are performed (Tek 3 ++) and not able to get the restrictors just right I dug the Dawes out again. I could not get the boost to go below 18 PSI. It seems that the culprit was not the spring or any other problem, but the bleed hole at 2mm was too big. Even with the spring removed it still ran 18 PSI. I filled in the bleed hole with solder and redrilled to 1.3mm and it is normal again. So don't bother going over 1.5mm or you end up with a bleed valve and this is what I was running before! Notably the Dawes is smoother with a fuel cut lifter as it seems that the Prodrive ECU was getting occasionally upset and hesitating a bit as it was seeing all the boost - I don't know the mechanism though. I have regapped the spark plugs which helped too.

Now running 18-19 PSI with the Dawes and AE801 and it all seems OK. No Delta Dash until I get my laptop on Tuesday though

ozzy

John,

You just couldn't leave it alone could you. Some people would be happy with 14psi.

Many thanks for the PPP ECU, the cars running superb now. Unfortunately my fuel economy seems to have suffered since we fitted the ECU on Friday evening

One question for you - I noticed yesterday after a good blast (30min+), when I pulled up to traffic lights the car would rev from 100rpm up to 1000rpm a couple of times before settling down to idle at a steady 800rpm.

Did you get that when the ECU was on your car?

Stefan

john banks

No couldn't live with 14 PSI. Standard idle speed is 850 RPM +- 50 IIRC. Idle control should be just like an AE801 ECU, but I've noticed occasionally the idle speed does vary now and again on any car - depending on fans, alternator loads, loads of factors - idle is a complex issue. Basically when it is hot if the speed is between 800 and 1000 I would not worry - at steady idle for a few minutes (when warm) it should settle though with tiny glitches as the fans come in. I think idle speed is an MOT requirement. Maybe you are just watching it a bit more. If there is a consistent problem bring it over when I get the Delta Dash up and running and I'll check it out for you - idle speed can be adjusted. Did you have the A/C on? I would just give it time to settle in though. I did reset the ECU a few hours before you came with Delta Dash, but then needed one last run before I let her go (sentimental fool) so it would've learnt my car again

[Edited by john banks - 4/21/2002 8:10:47 PM]

Scotsman

iTrader: (3)

I just could not imagine you running on 14 PSI mate

John - excuse the basic question - but is the difference between the dawes and a bleed value is that the dawes can vary the amount of boost whilst the bleed value is set?

Richard.

[Edited by Scotsman - 4/21/2002 8:44:15 PM]

john banks

Both are variable. The Dawes is effectively a wide open bleed valve that closes to the equivalent position of a bleed valve in effectively a feedback fashion as boost target approaches. Trouble is on a small turbo you have to dumb it down by adding a bleed after it as it does not know throttle position and always tries to make target boost which is undesirable and arguably harmful to your turbo and in-cylinder temps.

Scotsman

iTrader: (3)

Ah - thanks John.

Richard.

ozzy

Yeah, you looked like you had a tear in your eye when I drove away

No air-con, but I was running late, so just a blast along the motorway for about 20miles or so.

When I came off the motorway junction, there were about 4 roundabouts and another 6 miles or so before I hit any traffic lights.

I pulled up and notice the cars revs build up to 1000rpm, then immediately drop back to just above 200. It then went back up and straight back down again once more before it settled down and idled quiet happily at around 800rpm.

Another blast to the next set of lights and it did it again. I let the car cool down for a few minutes once I reached where I was headed and drove normally back home.

To be honest it's the first really hard blast in ages, so perhaps it did it before and I just never noticed. I tend to go out on the country roads, so you don't come across any lights were your coming to a halt, usually it's a slow cool-down drive back home.

Stefan

john banks

Honestly don't know. See if it is repeated I suppose. If not ignore. Mine never dropped below 800 RPM except when my wife drove it (and then it never went over 2500 either and then she complained it made a whooshing sound and took off out of roundabouts )

mutant_matt

John,

I've got a 2mm bleed on my Dawes (smallest drill bit I had and couldn't be bothered to find a 1.5mm one ) and I don't know if you remember but I had this same problem when setting up my Dawes?

I solved it by cutting down the length of the spring by about 3-4mm. The Dawes is now nearly fully extended but with enough adjustability (not that I need it 'cos since I set it, it's not needed touching ). The spool up with a 2mm bleed I like as it's faster than standard but not much more - the part throttle behaviour is excellent.

Ozzy, just so you know, often, if a car is hunting on idle, it can be a sign that there is a problem with the MAF (or you've got a Link ). If your car was perfect with the old ECU and this is just since putting the new one in then it's probably not that but just bear it in mind....

Matt

ScoobyJawa

John,

You may remember I had a 2.0mm bleed on my MY99 (800 ecu) and all sorts of problems - went back to a 1.5 and all sorted, so your experience seems to agree with this too!! Strangely, Scotts MY00 802 ecu is happier with a 2.0mm bleed than the 1.5...........

Cheers
Neil

spence7

Also, about the idle speed thing as soon as you stop the engine cooling fans come on automatically for a while which can cause the revs to dip a little for a short while...

Quick question though whilst on the Dawes subject If I fit an AFR gauge before fitting a Dawes, monitor the AFR levels, then fit the Dawes and try to achieve similar levels so as not to run unsafe /lean, will I get anything out of it?

Also, I was wondering where the extra fuel comes from to feed the extra air to give more power? Is it just using the rich mixture / unburnt fuel that's already present?

And if I increase the boost level with Dawes, how do I know what is a 'safe' AFR ? I mean more boost means leaner mixture, but does anyone know a safe lean cut off point which I could use?

Cheers
Alex

john banks

Fuelling is MAF based and will compensate - it will probably if anything be richer the more boost you add. The top light on a Dawes will invariably be on before and after fitting. This still gives a large margin for error - a lot of cars seem to be running over 910 mV (>>>10% CO)

spence7

OK cheers John, I was a little confused before, I forgot the ECU uses MAF sensor to get the right AFR not a fixed map. For some reason I thought fuel pulse width was all mapped out and fixed like for any rpm doh!

Cool, so it will still try to maintain a rich setting (to keep temps down I presume) during open loop control under hard acceleration.

So the AFR meter is something I'd just need to double check that this was the case I guess

Hmmm, sounds like I should get only the Dawes AFR gauge !

john banks

Or a digital voltmeter wired in when you are setting up - arguably a permanent solution is not required.

spence7

OK so if I got hold of a digivoltmeter an maintained >910mV (which is v.rich side I guess) on boost then I wouldn't be upsetting the mixture at least.

So only limitation to increasing boost would be hitting the fuel cut out then

I dunno, I just get the feeling that subaru would have used this higher boost if the internals were capable of taking it. I dunno ! I mean ok mixture stays the same, heat to be absorbed by block must increase with the extra fuel, as will oil temp levels I imagine (I'm guessing) and no.3 cyclinder more likely to fail? But then again there's no strict link between no.3 failure and upped boost levels it seems...it just happens so people say even on standard cars. So arguably because my 93wrx has around 90K miles, it would have maybe done it by now if was going to. I'm tryin got convince myself here...

john banks

I thought you had a UK. On a WRX you probably want to set it up with a select monitor so you can make sure the timing is OK as well - on MY99/00 we know them well and that there is a good reserve of fuelling for a Dawes.

Subaru seem to build in a considerable safety margin ON UK MODELS IN PARTICULAR. Some Jap cars det even on SUL so more caution is required!

spence7

noooo ! Select Monitor = pure expense I hear what you're saying though, that detting is close anyway (though no probs yet I always use 98 optimax touch wood) so any requirement given to ECU to retard the timing as a result of the mod will not be executed because of limitations of how much it can retard by. Damn is the word.

OK so I hear that because the combustion pressures will be increased, retarding of the timing would be necessary to maintain correct combustion point. And if my ecu struggles with this anyway, then I'm scuppered really aren't I. Only way is to get it remapped for UK fuel by the sounds of it? OR, monitor ignition timing during the process.

john banks

Having gone from working on cars with boost gauges and AFR to the amount of stuff I now get with Delta Dash I am now and engine info junkie and would feel in the dark without it. Sadly not for your model year hence the select mon. People get silly power out of WRX's with TD05, but some have ***** of steel and hope

spence7

Hmmm if I had a steel head gasket I'd have more steely *****

I think I;ll stick a new post out to see if anyone's done a Dawes mod to an otherwise standard (ish) 93 WRX...

I'm intent on getting this cheap mod done but I don't want to be scared to use it !