Turbo boosting question

Murv

Murv

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I have a problem that our Fairline holiday fitted with a Lancing marine 140bhp 2.5TDI engine won't achieve more than 8 knots, it won't rev to over 2500 rpm when in drive although revs round freely to max revs in neutral.
According to Lancing marine, the turbo should run at max boost of 15psi but it's only charging to 2.5psi at 2,500rpm.
The engineer thinks that it may be over propped, and that if the prop was smaller, it would obviously rev higher, then reaching full boost.
But, I always thought full boost was obtained far lower down in the rev range when the engine was under load hence the problem being the turbo not charging rather than the prop being the wrong size which isn't allowing the turbo to hit full pressure.
Who's right?

Cheers,
Chris

EDIT: Old thread, update on last page.
 
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The turbo on any engine running at 2500rpm and full throttle should be developing maximum boost so you are right to suspect a turbo problem. The turbo itself could be failing but that is usually accompanied by strange noises or lots of smoke so it's more likley a control problem. Wastegate jammed or some of the plumbing loose and leaking boost. Or the air filter could be blocked.
 
Thanks for that, there is no smoke or strange noises and the turbo appears to spin smoothly. The air filter is off and the plumbing appears ok, so I shall investigate the wastegate.

Cheers,
Chris
 
Murv said:
I have a problem that our Fairline holiday fitted with a Lancing marine 140bhp 2.5TDI engine won't achieve more than 8 knots, it won't rev to over 2500 rpm when in drive although revs round freely to max revs in neutral.
According to Lancing marine, the turbo should run at max boost of 15psi but it's only charging to 2.5psi at 2,500rpm.
The engineer thinks that it may be over propped, and that if the prop was smaller, it would obviously rev higher, then reaching full boost.
But, I always thought full boost was obtained far lower down in the rev range when the engine was under load hence the problem being the turbo not charging rather than the prop being the wrong size which isn't allowing the turbo to hit full pressure.
Who's right?

Cheers,
Chris
Click to expand...

The boost pressure also relies on adequate fuel so check fuel filters and throttle travel.
If the injection pump has a boost capsule on it, check the pipe from it to the turbo outlet.

What speed did you get at 2500rpm?

Ian
 
Thanks Ian, I'm assuming that the throttle travel is ok as it revs freely to max revs in neutral. I don't know if it has a boost capsule, I shall check.

It managed about 8.5knots at 2,500 rpm.
 
If the Turbo is not making any noises and air filter etc are in good order I would be looking at the fuelling. Is this engine common rail? What is the base engine?
 
Thanks both, I shall investigate those as well then!
I've no idea if it's common rail injection, but I would imagine so. The base engine is a transit 2.5 TDI badged as a FSD TI with the Lancing mods to it.
 
The reason I mentioned common rail was that some common rail engines experience the same symptoms as yours when the rail pressure fails to regulate. Toyota D4D engines for example have an issue with what they call fuel suction valves. This is basically two valves that regulate the fuel pressure in the rail. These started sticking due to design flaws and gave the exact same issues you mention. Toyota initially blamed the problem on Turbos and charged a lot of people a lot of money for new ones.
There must be a means of regulating the rail pressure in the same way on the Ford. Try checking Ford owners forums to see if rail pressure is a known issue.
 
Murv said:
Thanks Ian, I'm assuming that the throttle travel is ok as it revs freely to max revs in neutral. I don't know if it has a boost capsule, I shall check.

It managed about 8.5knots at 2,500 rpm.
Click to expand...

If you've only lost half a knot, it could just be a fouled hull and / or prop. Such an apparently big drop in boost would not just cause a loss of half a knot because torque is very reliant on boost pressure on a turbo engine. Also, as you are still achieving the same rpm, but the speed has dropped, then this shows its NOT the engine...

(when my hull and particularly, the prop, were badly fouled the max engine rpm was reduced from 2200 to 1600rpm with the resulting drastic drop in speed. I didn't believe the cause was this simple, and changed filters, lift pump, checked the timing etc, all to no available until I hauled her out and saw the reason!)
 
Pretty certain Murv had this out recently to fix the outdrive, so any fouling would have been seen.
Murv which marina are you at cuxton/elmhaven, as im just down from you and could always have a look, cant garuantee anything but looking is easy!
What size is the prop currently fitted?


Lynall
 
bikedaft said:
Worth doing a pressure test of inlet manifold pipework, to make sure no leak, that only shows up under positive pressure.
Click to expand...

Not sure how that would work as any pressure would be lost past one pr more cyl head valves that would be open.



Lynall
 
Either inlet or outlet valves will be shut - not both open

So you get some leakage down sides of pistons to sump, and some thru turbo seals

Which is why stay at low pressure eg 10-15psi

It works on my 30v v6 twin turbo anyway :-)
 
First replace fuel and air filter-once had the same problem with a Nissan Terrano I had just bought preowned -hardly any power up hills etc-replaced the fuel filter on the road side and no problem.
Turbo chargers dont suddenly fail they degenerate over a period.
Finally do not rely on those magic words"its been recently serviced"!unless you did it yourself or watched someone do it.
If you are unable to service yourself mark the filters to see if they have been changed or not!
 
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bikedaft said:
Either inlet or outlet valves will be shut - not both open, tis true, but you mentioned, inlet pipework and i replied the pressure would be lost, via the valves.

So you get some leakage down sides of pistons to sump, and some thru turbo seals, you are talking cylinder leakage test which is not testing the pipework at all, turbo seal leakage will be minimal.

Which is why stay at low pressure eg 10-15psi, not really enough for a cylinder leakage test, last one i did i used workshop pressure and basically the air escapes from every bloody where.

It works on my 30v v6 twin turbo anyway :-), pls show me some pics of said test kit in action.
Click to expand...

ffill, turbochargers can and do suddenly fail, we see it all the time at work, normally with explosive results!


Lynall
 
Has the boat ever done more than 2500rpm with the prop that is on it? I would suggest the marine version would need a few more revs to provide full boost pressure. Marine versions of this engine are normally set up to boost at the top end. My mates fairline with a volvo diesel does not boost fully until nearly 3000rpm so if it was held back by too big a prob it will never get up and go.

If its never revved with the prob that's on it your engineer is correct
 
lynall said:
ffill, turbochargers can and do suddenly fail, we see it all the time at work, normally with explosive results!


Lynall
Click to expand...

Not quite sure why you are quoting me with nonsense i never said, see my post #14

Will look for picsof kit later

It is not a cylinder test, that'sdifferent!

Yes the test doesrely on your bores/rings etc not being gubbed

But is a relatively easy, often overlooked test that really needs to be done first to check inlet pipework, if you have a leak there you lose boost, andput extra strain on the turbo

But i do agree that turbo'susually go phut quickly. Often with dentist drill noise, or bang
 
http://www.audizine.com/forum/showthread.php/425847-Question-on-pressure-test-on-2-7t-motor

Post 2, there's a pic

Pressure from a (mostly depressurised) tyre, via small bore pipe to somewhere in your inlet piping just after air filter. In cars often take MAF out, but doubt you have one?

So really the tricky bit is getting some flex pipe large dia that fits over your engine inlet piping.

Or you can use a side hose, tho you still need to blank inlet piping to stop air going back thru filter.

Most engines are different, the breather hose from top crankcase often vents into inlet side nowadays. Clearly you need to remove this and blank off for test or all air goes into crank cover area.

Have fun :-)
 
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