conrad

After recently purchasing a UK 96 Scooby I have done a few mods. I have bought a new downpipe, centre section, back box and panel filter.

I was considering buying a Dawes Device and turning the boost up to a safe but faster level. In the mean time I have bought a boost gauge to see what boost I'm currently running. After fitting it last night and taking it for a quick spin I have discovered that I'm already running 15 PSI. I had been told that I'm supposed to have a fuel cut at 1 bar (14.5) and wouldn't be able to raise it above this.

Is this true and should I be running such high boost from just de-cating the car and putting a panel filter in?? I'm a little worried that I'm running too high a boost and could damage my car.

Does anyone know if it's safe to run the car at 15 PSI and if possible safe to run it even higher should I get the Dawes device.??

Any advice appreciated

iain atkins

You boost gauge will probably be over reading a little IMHO.

Either that or the person who owned it before you may have tweaked the fuel cut and boost.

But i thought boost cut was at 15.5psi on the older WRX's - maybe i'm wrong

Cheers



Iain

conrad

Thanks Iain

As far as I know the car was definitly standard - nothing had been done to it like that. Also, my car's a UK car so I'm not sure if the fuel cut is lower than on the WRX.

Is there a way to check if the gauge is over reading and if so how do i stop this??

Thanks - Conrad

iain atkins

Sorry Conrad, misread the UK bit

Gauges either over read a bit or under read a bit - there's no exact science with it.

I can't remember where the orignial fuel cut was on my UK97, i think around 16psi (or there abouts).

Also there is no real science as to what is considered 'safe boost increases'. Before you consider a dawes, you are best off getting an air/fuel ratio meter, and get hold of some det cans / knock link - to see how the standard car is fuelling, and make sure there is no hint of det, this may sound overkill, but the fuel pumps on some cars can be a bit weak at even standard boost.

Cheers



Iain

conrad

Thanks Iain

I was going to get an air/fuel ratio meter as you suggested because I'm a little worried as to what boost to up it to (if turning it up at all).

The last thing I want to do is cause any det/damage. I'll look into what you suggested and see how it's running

Cheers - Conrad

ademid

I also have an MY96 and have done very similar mods to yourself (although I have also fitted a uprated fuel pump and hope to fit an uprated regulator soon) And I am aiming for about 16psi. Anything else on our age of car and everything snowballs ie different injectors need different ecu then to get the benefit from those you need different turbo or front entry mod then you need better intercooler to get the best from that etc etc etc

Thats what I have been led to believe and that's what I'm aiming for (that's not to say I'm right so don't take my word as gospel!)

Ade

conrad

Cheers Ade,

Have you turned your boost up already or do you plan to once you have finished your mods??

Might sound daft (not much of a mechanic) but whats a regulator?? Do you recomend I get this as well?

Leslie

As far as I can find out your fuel cut is 15.65 PSI. You would be better off to fit a Knock Link and AFR if you wish to increase your boost to make sure your engine remains safe. Your increased boost will come from your improved exhaust system. I have done similar improvements to my car, MY94, and am seeing the same kind of thing.

Les

[Edited by Leslie - 5/23/2003 11:52:59 AM]

conrad

Cheers Les,

Daft question again - what's a Knock link and where can I get one from??

I'm still learning when it comes to this kind of thing....

SiHethers

Conrad

A knocklink is a module which you connect to a knock sensor, which is like a microphone bolted to your engine block. Knock (aka pinking, pinging, det) is the noise made when unburnt charge spontaneously ignites in an uncontrolled fashion ahead of the flamefront in the combustion chamber. It causes a marked increase in temp in the cylinder and a shockwave through the piston/conrods etc. It's self sustaining too,i.e. some det leads to more det leads to melted/cracked pistons/rings etc.

If you up the boost you make det more likely due to higher cylinder temps and higher dynamic compression ratio at least. Then you have to consider whether your ECU will supply enough fuel and appropriate timing when you increase the boost over standard. The Knocklink will warn you whenknock is occuring so you can lift off the throttle and investigate why it's happened.

Your standard ecu has its own knock sensor, but these are notoriously unreliable at picking up transient det, especially when boost spikes, and at high revs when engine noise is greater.

Hope this helps and isn't too technical

Simon

Edited to say- you can get a knock link and sensor from BR Developments

[Edited by SiHethers - 5/23/2003 1:21:31 PM]

conrad

Thanks Si,

I'm slowly learning,

I don't suppose you know how mucj a knock link is and where I can get one from??

SiHethers

Conrad, no probs

Try here

Simon

NM

Something to think about!!!!!

I have a UK MY98 and hit the fuel cut on many occassions before modding my car. I have fitted a boost gauge which reads different values when the fuel cut comes in from 15.5 PSI to 17 PSI.

Surely the fuel cut is a ECU defense system that saves the engine from the big bang. Therefore keeping the boost below this level should save your engine. But as the air changes and most noticably before it rains the car feels more eagar and produces more boost due to density of the air. The ECU is designed to cope with this by adding more fuel etc but only up to the fuel cut/overboost level.

I also noticed adding a full decat zaust increases your boost levels.

My last rolling road showed 262BHP peaking at 16.5PSI (gauge showed 16PSI) though this is switchable as I run a Blitz boost controller which you can set a limit of boost. When it reaches your set limit it reduces power by a predetermined %. Most of the time it is swiched off and only turned up when its time for some fun !

Conclusion !

Therefore using this information raising your boost from standard 14PSI to say 16PSI (using a calibrated boost guage) should be safe as long as you havent moved the fuel cut level and you dont keep bouncing off the fuel cut. Also I had a chat with a dealer who said off the record that 15.5PSI was safe for a UK classic turbo.

I could be wrong but it all seems to make sense as the Impreza ECU is designed to work from Scorching heat to freezing blizards.

Cheers

Neal

conrad

Cheers Neil,

your advice is much appreciated....

Conrad

NM

Conrad

Why not come over to our next Coventry area Meet on Sunday 8th June.

Venue is the Bulls Head Pub in Meriden, just off A45 between Coventry and Birmingham

See this link for all the info

conrad

Thanks Neal (spelt it right this time)

I just might do that, thanks for the invite

Conrad

SiHethers

Neal

I think the real issue with increasing the boost is running inappropriate ignition timing. This is largely based around mass air flow, but is modulated by MAP signal. I currently run 18psi in the midrange dropping to 14.5psi at 5800rpm and 13.5 at 6500rpm (the limit of the TD04L turbo). Conrad is in a different situation because he has a TD05 turbo, which will happily hold 22psi at 6000rpm.

On an early model, if you set say a Dawes MBC to 15.5psi, it will hold that to the redline,so I think you need to be a bit more careful, and monitoring with a knocklink a must. Scoobs run very rich so fuelling may not be a prob (so long as the fuel pump can supply it), but AFAIK the earlier models run even more advance than MY98/99/00, so that they can achieve similar power/torque with lower boost.

Im not sure what I'm trying to say here Probably that you don't have as much flexibility with the phase 1 engines straight out of the box, for the above reasons.

That's not to say you can't do it though because there is plenty people on here who have

Simon

Edited to say - Just realised Ade has said all this already, but more succinctly

[Edited by SiHethers - 5/23/2003 7:36:05 PM]

StanS

iTrader: (3)

Just to add my 2p worth !
I ran my UK 98 for 18 months (before upgrading) with a pp ecu (which must have had a much higher cut) decat, 1.7:1 rising rate fuel reg, K&N filter and smaller wastegate orifice (£1.29) so it ran at peak boost 21-22 psi @ 3K but the pp ecu reduced that to about 14psi @ about 6K rpm. Rest was std.
Did 278 BHP and 265 ft-lbs at Well Lane (in Jap Performance Car July/Aug 2001 - typical comment at that time - "must be mad running sky high boost with std internals" ) - behind P1 that did 289 BHP. Drove well and when stripped down no piston melt or other probs. Had it select monitor checked every 6 months to check det, and ran octane booster.
Stan

Leslie

I can confirm what Simon said about ignition timing, boost levels,fueling, and knock, on earlier cars with the TD05 turbo. My MY94 STI is currently running just over 15 psi, the fueling is rich at WOT in 4th and top gear. My fuel cut is at 15.65 psi. There is no sign of knock using straight Optimax.

Thanks for the earlier advice Simon. I had to reduce the size of the hole in the s/h Dawes which was at 1.5mm. Too big I think with the TD05. I filled it with solder and then drilled it out-eventually to 0.7mm. The spool up is quicker and the engine feels sharper. I set the boost to below the fuel cut, it would reach this before I fitted the Dawes. I hope to get a chance to try the ScoobyEcu map eventually when I have fitted the ported headers.

Les