406hdi 110hp - Voltages on MAP, 406hdi, 2004.

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Thu 20 Jan 2011 14:37
406hdi 110hp - Voltages on MAP, 406hdi, 2004. - Brlja

Greetings,

Looking back a few months i have some problems with my 406hdi 110hp. It simply isnt strong as it used to be. There were some troubles with MAF before that but i cleaned it with carbcleaner and it works just fine, but when i start the engine, "check engine" lamp stays on for a few secs and then goes off.

Few weeks ago i found a MAP graph showing dependancy voltage-pressure so i decided to give it a go as i suspected that it might be air related. So i conected it to a voltmeter, drove around observing results.

At idle, its on 2,39V.

At 2000 rpm its around 2,49V and it hits 3V at 3500rpm.

Looking at graph, even 3V matches absolute pressure of 1,4bar. Im not 100% sure but he should be filling 2bar from 2000rpm on. Am i right about this?

Could it be boost leak, i do hear some cricket sound when accelerating but ppl that drive with me say im crazy, but then...only a car owner hear those little squeks and irregularities.

Basically im just wondering about those MAP values.

Tnx.

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Sun 23 Jan 2011 19:39
406hdi 110hp - Voltages on MAP, 406hdi, 2004. - Brlja
Fixed. Was a small split in vacuum tube leading to wastegate actuator, quite hard one to see as well. Whistles and goes like new now.

Funny how such a small thing can cause that much trouble.

Edited by Brlja on 23/01/2011 at 19:40

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Sun 23 Jan 2011 21:38
406hdi 110hp - Voltages on MAP, 406hdi, 2004. - unthrottled
Yup. So many of these 'my turbo has failed, the dealer wants £1400 for a new one' boil down to a problem of turbo control, rather than the turbo itself. The turbo itself only has one moving part, and providing it is kept lubricated and cooled, it seldom fails. I don't know why turbos always seem to be the first thing people blame when a diesel engine doesn't behave correctly. Turbos are feedback loops; they can only spool if the engine provides sufficient fuelling to heat the exhaust gas sufficiently. Normally, 'lack of boost', is a symptom rather than the cause of loss of power.

I guess the turbo has replaced the carburetter as the whipping boy of choice. In the old days, everyone was convinced that a malfunctioning engine was due to the carb providing the 'wrong mixture'. As soon as an engine started misfiring, the first thing people did was to fiddle with the mixture control, usually ending up with an overly rich mixture, because that masked the true cause of the fault.
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