nickwrx

i want to fit an adjustable boost controller,the ones you can buy for about £70,the hks ones are to expensive, could anyone tell me the pipes that you connect it to, and is it an easy job, and would the chip need upgrading,i've only had my 95 scooby for two weeks now and i'm well impressed,great message board by the way, any help would be grateful, thanx.

AlexM

Nick,

For about £70 I would guess that you are talking about a cabin adjustable bleed valve. In a word - don't!.

As you may have read, you can cause severe engine damage by turning up the boost beyond the range that the ECU would normally manage. The reason is that your fuelling and ignition timing must be altered to suit the increased boost levels to prevent detonation and/or lean running.

I also remember reading that 'dial a boost' remotely mounted bleed valves allow big overboost peaks because of the length of the tube to the bleed valve - again a very bad thing.

Now you know about the caveats, I can tell you that it is possible to get a safe, cost effective boost increase with a bleed valve but you have to be very careful not to over do it, and keep you peak boost within the standard overboost cutout level (depends on your model) to keep things safe.

Lee Christie has tried this on his MY99 UK model with good results, but moderation is the watchword of the day. His bleed valve wasn't the cabin-adjustable type though - steer clear of them. Try contacting Lee for more info, or search for related threads.

The HKS boost controller you mention is electronic and people have used them effectively, but again the same restrictions apply with the peak boost levels assuming no other add-ons which provide fuelling/ignition timing correction. Don't be tempted to defeat the overboost cutout safety mechanism or your engine will suffer very quickly.

To go further you would be looking at either a suite of HKS boxes (££££££), a remapped ECU (a lá PE Phase 1 conversion), or an aftermarket ECU (Possumlink, Motec).

I'm not trying to put you off, but be aware that it is very easy to cause yourself expensive problems with bleed valves, and sometimes a higher initial outlay proves more economical in the long run.
Rgds,

Alex

Lee

I would disagree with some of that, although good advice in general.

point 1. you can only up the boost to approx 18psi on a MY99 before you hit the fuel-cut defence mechanism of the ECU. Therefore provided you don't fiddle with any MAP outputs 18psi will be a safe limit.

point 2. provided you follow point1 !! And stay to 18psi fuelling and ignition is OK.

the only problem I can forsee is that setting the valve too high causes the cut-out to occur frequently and makes for a bad drive.

apart from that, its £20 and offers a gain. I have now moved onto the possumlink..I didnt even consider the elec.boost controllers cos it isnt the boost which is a problem its the cut-out, fuelling and ignition above 18psi.

AlexM

Thanks for the correction Lee - I meant what you said, i.e. the fuelling/ingition map for the ECU obviously doesn't extend beyond the overboost cut-out (1.1bar?).

I'm not sure that it is proven that any boost inside this limit is safe with the standard map of the unmodified ECU. Don't forget that the overboost fuel cutout is a safety net, and no unmodified UK car would normally get anywhere near 1.1bar, transients possibly excepted.

What I mean is that the ECU isn't necessarily properly mapped up to this limit, and the FCD is designed as a defence against abnormal operation i.e. stuck wastegates, pipework leaks etc, rather than indication of the safe limits for normal conditions. Maybe it is safe, maybe it isn't - all I'm saying is that you can't necessarily make that inference.

All IHMO of course.. Please feel free to correct my understanding if you disagree.

Cheers,

Alex

AlexM

One other point..

With an electronic boost controller, even though they don't allow you to boost higher than would be safe with a bleed valve, they do offer some other benefits, although they are obviously nowhere near as cost effective (you can't argue against 20bhp for £20 ).

Firstly, they hold the boost control solenoid closed until they are close to their target boost setting which means that boost builds more quickly

Secondly, because they offer closed loop boost control, the level of boost should remain more consistent across a wide temperature range, wheras the car will generate more boost with a bleed valve when it is cold due to changes in air density (tell us more about your experiences of this Lee?).

I don't have an EBC, so this is all IHMO once again. Some people have used the HKS/APEXi and other electronic boost controllers with good results, so I'll leave further specific commentaries to them. I do know that they aren't cheap, so their value compared to a full remap or aftermarket ECU is questionable when you consider the additional flexibility they may offer. As Lee mentions, with an EBC you are still stuck with the default fuel & ignition maps. You pays your money....

Cheers,

Alex

Lee

questions , questions
>>>>>>
Firstly, they hold the boost control solenoid closed until they are close to their target boost setting which means that boost builds more quickly
<<<<<<

yep, this also creates more overboost I'm told and thus more likely to hit the cut-out ?

>>>>>
Secondly, because they offer closed loop boost control, the level of boost should remain more consistent across a wide temperature range, wheras the car will generate more boost with a bleed valve when it is cold due to changes in air density (tell us more about your experiences of this Lee?).
<<<<<<

my experiences show that the bleedin-valve (Moray) "adds" a couple of psi across the range, but retains the normal profile. I had to turn it down slightly when it was very very cold.

nickwrx

You guys certainly know your stuff, what i got from that is its ok to us a underbonnet bleed valve,so do you know where i can get one from and where do you fit it , cheers

GavinP

Nick,

Take a look at Lee's web site for more info -

Wreckleford

Lee,
If you calibrate your Electronic boost controller properly, you should't get any overboost. That's the whoe point of the all the elECtro-trickery. To keep the wastegate shut until the last minute and then slam it open at the correct point so that boost rockets up to the set value and stays there.

Some controllers are easier to calibrate than others, but once you set it up you shouldn't have any problems.

Lee

Thats why I put "so I'm told" I have no personal experience of an ebc.

I just don't know why people would buy them for the scoob..in order to get the real benefit you have to go the superchips defender route, and by the time you've paid £350 for the ebc and £200 for the superchips you are very nearly at replacement ECU cash levels..

Matt S

Guys, without getting into the debate of MBC vs EBC, there is an MBC that works in much of the same way as an EBC works in that it will hold the wastegate shut until the last possible second then will open it all at once. It is not a bleed valve. I run one on an older Legacy Turbo and have been quite pleased with it so far. Have a look at

Wreckleford

I mentioned this controller earlier when Lee first posted his results when he installed the bleed valve. There was a little discussion about it. You might want to do a search for it to get more info. on the pros/cons.