Turbo question

[Surf01]

Being a bit non mechanical thought I would ask the question anyway. It seems that the turbo on the truck drops out at about 53mph, but will kick in again if trucks drops down to about 48mph. On my last 3rd Gen Surf it was 50mph and could drop down to about 45mph before turbo kicked in. same road, same conditions.
Would a decent tune up resolve this issue or would the ECU have to be re-mapped? The only reason I am asking is that where we live no chance of getting to over 50mph due to speed restrictions and very careful of exceeding the 50mph as they trap a lot on the A449 which is near to us.
Not sure if it can be done but any advice welcome. Truck which is a 1996 3rd gen has done about 73798 miles.

[Rustinho]

I thought the turbo would be more likely to be linked to engine revs than actual speed of the truck...

[red barron]

Turbo

The fuel injection pump is controled through the ECU, The turbo is powered by the exhaust gas effectively its a compressor charging the cylinders with more air
dependent on the amount of fuel being introduced through the injectors from the pump to the combustion chamber/cylinder.It is possible that its fuel/ecu related.
But there are other possibilities to consider too. Interesting to see what Tony N may point out.

[shokenore]

Being a bit non mechanical thought I would ask the question anyway. It seems that the turbo on the truck drops out at about 53mph, but will kick in again if trucks drops down to about 48mph. On my last 3rd Gen Surf it was 50mph and could drop down to about 45mph before turbo kicked in. same road, same conditions.
Would a decent tune up resolve this issue or would the ECU have to be re-mapped? The only reason I am asking is that where we live no chance of getting to over 50mph due to speed restrictions and very careful of exceeding the 50mph as they trap a lot on the A449 which is near to us.
Not sure if it can be done but any advice welcome. Truck which is a 1996 3rd gen has done about 73798 miles.

M5 or Long Marston ?

[Kwakka666]

don't suppose it's an easy question and you've stuck some 33" tyres on it?

[biscuitthief]

Is it actually overdrive we are talking about here, rather than the turbo?

[NiftyNev]

Is it actually overdrive we are talking about here, rather than the turbo?

I'd suspect that as well.

Nev

[Predictable Bob]

Sounds normal to me - it's just dropping out of lock up !

[Surf01]

It was my thought that if I was able to have the revs reach their "peak" to drop out of the turbo operating at an earlier point with this being below 50mph. I don't feel comfortable with it dropping out at 53 -55mph especially if I get a ticket for speeding in a 50mph zone.
No issue obviously on a motorway but we seldom see a motorway. Probably less than several times a year unless it starts smoking too much on start up. LOL!

[TonyN]

The turbo dosn't noticably kick in or out unless it's under or overboosting, then you'd get a check light.
I think it's the gearbox doing its job.

[Wolfracer]

Can we confirm you are talking about THE GEARBOX and not the turbo please?

Go for a drive, somewhere you can do high speed, lets say the M5, now get it up to 60 and back off the throttle so you are crusing. now hit the OD button (light on D board) it should kick down, revs rise etc...

Now do it at 55.

again at 50.

again at 45.

Which of these is the same as your "turbo" problem?

[shokenore]

Can we confirm you are talking about THE GEARBOX and not the turbo please?

Go for a drive, somewhere you can do high speed, lets say the M5, now get it up to 60 and back off the throttle so you are crusing. now hit the OD button (light on D board) it should kick down, revs rise etc...

Now do it at 55.

again at 50.

again at 45.

Which of these is the same as your "turbo" problem?

Post #4