On a good day my MY00 boosts to just over 15psi if I really plant it tailing off to 13-14 for most of rev range.

I've now changed my route home from work and spend maybe 10mins sat in heavy traffic before a quick blast around duel carriageway. When hitting dual carriage way initially max boost is only 13psi. After maybe 5 mins peak is almost back to 15.

Is this because everything is sat getting warm in traffic and takes a while to get back to normal running temp ?

Or is there something I need to worry about

Cheers

Mark

Probably the heat soak, intercooler will be seeing nearly 60 deg C from sitting in traffic especially if the cooling fans trip in.

Bob, not doubting what you say is true, but I wonder if there is not another factor to this ...

When I do my normal commuting, I normally drive quite slowly... lots of start stops etc...

When I then take it out at night or in the weekend, after warming it up carefully, and booting it, I see about 1.2 bar of boost in 3rd ... when I repeat this a few times, and really go for it, it slowly creeps up to about 1.25 bar boost max.

I've seen this time and time again, and when mapping the Unichip we made sure we really drove it hard before adjusting things.

I used to think it was a compensation feature in the standard ECU, but I still see the same phenomena with the Unichip/Dastek boost controller.

I'm pretty sure I'm not making up stuff on this one, I can repeat it time & time again.

Wonder if it has to do with carbon build-up or something similar ?

I get that too Theo, with my Blitz DSBC (boost controller) and standard ECU. In traffic or on hot days I'll only get 1.15bar or even less and on cooler days or on cooler nights or when doing higher speeds which brings in more air I'll get up to 1.23 bar. Well it's not exactly bar but Kg cm2 or whatever it is. I think it's to do with the car running cooler. Cooler at night and the car cooling down once you start doing higher speeds.

Cheers,

Wrexy.

[This message has been edited by WREXY (edited 28 September 2001).]

I think it could also be from that while your engine may be warmer, your sparks are actually COOLER as a result of sitting in traffic for so long at low RPMs. Crap builds up on them, and takes a few minutes to burn off. While they're a little tarnished, your combustion won;t be as complete, so you won't get as much exhaust flow. this will drop your boost. If it was the intercooler or something like that, it would only take about 20 sec to get back to temp with cold air running over it. those things are made to exchange heat. It wouldn't take minutes. I could be wrong on this one. I was wrong once back in '83. It was terrible. Clean record since then though.

-IggDawg

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by IggDawg:
<B>...it would only take about 20 sec to get back to temp with cold air running over it. those things are made to exchange heat. It wouldn't take minutes....[/quote]

Mr Dawg http://bbs.scoobynet.co.uk/wink.gif, I'm afraid that I have to disagree, it can take a couple of minutes for the inlet temps to come down. Many times I've been sitting in traffic and seeing inlet temps of around 60DegC +, get to some empty roads and at speeds of approx 60-90mph (running at max boost), it takes a good couple of minutes for the inlet temps to hit 38-45DegC (usual max boost inlet temps for me).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR><B>I could be wrong on this one. I was wrong once back in '83. It was terrible. Clean record since then though.
[/quote]

Shame but your record is now in tatters!!! http://bbs.scoobynet.co.uk/biggrin.gif http://bbs.scoobynet.co.uk/biggrin.gif http://bbs.scoobynet.co.uk/wink.gif http://bbs.scoobynet.co.uk/wink.gif http://bbs.scoobynet.co.uk/wink.gif

BTW - Mark, Hi and hope this helps.... http://bbs.scoobynet.co.uk/smile.gif

Matt http://bbs.scoobynet.co.uk/smile.gif



[This message has been edited by mutant_matt (edited 30 September 2001).]

I can get similar on PPP. On a really good open road blast see 18PSI peak 16.5PSI held.

Otherwise might see 16peak/held.

Doesn't help that I keep changing the wastegate restrictor to get it just right though.

I would think that the mass of air is probably causing this - a bleed valve or manual boost controller shows similar behaviour.

Not a bad thing IMHO as it is safer to have the boost level drop a bit when the car and/or ambient temperature is higher.

Treat it as a "safety feature"... http://bbs.scoobynet.co.uk/wink.gif

Thanks

Gavin

Since Unichip is a piggy back item then the ecu will still react as necessary, oem ecu can react to excess engine temp and reduce boost, no piggy back chip will be able to over ride that afaik.
So a slowish crawl with the fans tripping in will send temps high.

Bob, I use the Dastek boost controller with the Unichip... unless I am completely ill-informed, the standard ECU can do nothing at all about the boost control... It could only retard ignition, but that would be a bit daft.

Theo