Maximum boost

[Scorpio67aussie]

Hi I'm having trouble finding maximum boost pressures that the turbo runs standard, my transit is a mk6 2001 125 t350 high roof long wheel base my ford dealerships and head office have no clue apparently and what would the maximum boost you could increase to without engine problems and engine modifications sorry if this has been asked before but I can't find it with thanks Richard

[knobby1]

It's basically controlled by the PCM depending on load, throttle position & RPM....but others have had them remapped which usually helps greatly.

Not sure on the max boost for a Mk6 125 TDDi...but my Mk7 140 TDCi (remapped) is in excess of 23psig at the manifold on a full pull.

Lord Knobrot

[wojciech]

Hi I'm having trouble finding maximum boost pressures that the turbo runs standard, my transit is a mk6 2001 125 t350 high roof long wheel base my ford dealerships and head office have no clue apparently and what would the maximum boost you could increase to without engine problems and engine modifications sorry if this has been asked before but I can't find it with thanks Richard

During stabilized driving with full power, boost pressure should be about 1.0 - 1.1 bar (relative pressure).
During driving with variable power, boost pressure can jump for a moment to about 1.4 bar - because of inertia control system.

Readings can be different little bit, because of air temperature and IC temperature.

but my Mk7 140 TDCi (remapped) is in excess of 23psi at the manifold on a full pull.
Lord Knobrot

23 psi = 1.59 bar
In tdci turbo is VGT, so PCM can control pressure. In tddi turbo has Wastegate, it works independently to PCM on short feedback loop. Pressure correction is possible only on Wastegate tie-rod.

[Scorpio67aussie]

Thank you both very much

[knobby1]

23 psi = 1.59 bar In tdci turbo is VGT, so PCM can control pressure. In tddi turbo has Wastegate, it works independently to PCM on short feedback loop. Pressure correction is possible only on Wastegate tie-rod.

Not "all" Mk7 TDCi's are VNT, some have a wastegate...but yes, the PCM controls the boost pressure depending on the inputs from the various sensors etc...

Lord Knobrot

[ned]

It's basically controlled by the PCM depending on load, throttle position & RPM....but others have had them remapped which usually helps greatly.

Not sure on the max boost for a Mk6 125 TDDi...but my Mk7 140 TDCi (remapped) is in excess of 23psig at the manifold on a full pull.

Lord Knobrot

I get about the same as you your lordship, foot down I can see 25 psi of boost, normal driving is around 10 - 15 psi (granny driving ) but I have my boost gauge take off pipe just after the resonator (think that's what that plastic thing is just after the turbo) not sure if it makes much difference N

[knobby1]

I get about the same as you your lordship, foot down I can see 25 psi of boost, normal driving is around 10 - 15 psi (granny driving ) but I have my boost gauge take off pipe just after the resonator (think that's what that plastic thing is just after the turbo) not sure if it makes much difference N

I have mine plumbed into a Festo fitting in the manifold only a couple of inches from the MAP sensor, so hopefully I get a "true indication" of what the engine sees...

Lord Knobrot

[wojciech]

23 psi = 1.59 bar In tdci turbo is VGT, so PCM can control pressure. In tddi turbo has Wastegate, it works independently to PCM on short feedback loop. Pressure correction is possible only on Wastegate tie-rod.

Not "all" Mk7 TDCi's are VNT, some have a wastegate...

Lord Knobrot

I know it, but Scorpio67aussie has Mk6 and wrote about Mk6 - so I also wrote (with an implied ) about Mk6.

[Scorpio67aussie]

Thank you everyone for the replies
mine has lost power I put a boost gauge on it and it was showing 15 psi and now has dropped to 13 psi it just doesn’t have the same excelleration and has lost economy

[wojciech]

Thank you everyone for the replies
mine has lost power I put a boost gauge on it and it was showing 15 psi and now has dropped to 13 psi it just doesn’t have the same excelleration and has lost economy

First look for intake pipes leakage - pipe between compressor and IC and between IC and inlet manifold. Look for oil traces on pipes - inside of pipes is always little bit of oil (because of engine breather)- it is good indication of leakage.
Look also for inlet manifold - it can be broken. Typical defect.

[APH]

blank egr valve if not already done, most boost leaks are from slightly stuck open egr valves, allowing the boost to go straight out the exhaust.

Andy