Login

cancunia · 29-12-2020, 05:27 PM

What's the Turbo Boost reading?

flanagaj · 29-12-2020, 06:38 PM

(29-12-2020, 11:58 AM)Zion Wrote: Without being able to measure boost, fuel pressure and airflow it will be hard to diagnose. Generic OBD readers can't do it on PSA cars but the Torque Pro app can, with a Bluetooth OBD adaptor.

There are other ways but more expensive.

Boost should get to just over 1 bar / 16psi and fuel pressure should hit something like 1200 bar at full load.

You might have a vacuum leak to the turbo boost control or a partly blocked DPF, lower fuel pressure than required or low readings from the MAF which would cause reduced fuelling to the injectors.

These may not be enough to trip a fault on the dash but reading live engine data is going to be the way to get to the bottom of it. Could even just be a clogging fuel filter.

(29-12-2020, 05:27 PM)cancunia Wrote: What's the Turbo Boost reading?

Sorry, but I don't think my OBDII scanner provides that data. Can that not be deduced by the manifold pressure? The manifold pressure seems to be extremely close to atmospheric pressure. I have tested the waste gate is holding vacuum as if I push the waste gate in and hold my finger over the hole it stays in place.

**Sol** · 29-12-2020, 06:47 PM

Intake manifold pressure at 14psi is boost. Just a smidge below 1 bar, not too bad. 95,000 psi fuel pressure however is 6500 bar! That's massive, can't be right. Max is 1500 bar or 21,600 psi. That should have thrown a fault code above 1750 bar.

Can't get my head round lbs/sec airflow, doesn't look right though. I'd try disconnecting the MAF - open the bonnet, switch off and close the doors, wait 3 minutes then unplug the MAF...then start it up and go for a drive, see if it pulls properly. If so, the MAF may be the issue.

**Sol** · 29-12-2020, 07:21 PM

Intake manifold, can't remember if it reads absolute or gauge. If it's absolute, then you have no boost. If it reads gauge, then that's 1 bar. (14.4 actually but close enough) so hard to say. What does intake manifold pressure read when the ignition is on, but the engine not running? If zero, then it's gauge - if still 14 psi, then you have no boost.

**saskak** · (This post was last modified: 30-12-2020, 10:19 AM by saskak.)

(29-12-2020, 06:38 PM)flanagaj Wrote: Sorry, but I don't think my OBDII scanner provides that data. Can that not be deduced by the manifold pressure? The manifold pressure seems to be extremely close to atmospheric pressure. I have tested the waste gate is holding vacuum as if I push the waste gate in and hold my finger over the hole it stays in place.

It could be the turbo solenoid at the back of the engine, although this would not explain the noise. The wastegate could be working, but no vacuum supplied to it from the turbo solenoid. Does the wastegate rod move on startup and stay there?
Any OBDII scanner should provide boost and it should get to at least 1.5bars under load. Disconnect the vacuum line from the wastegate and see if it is the same lack of power, then you would know it is the solenoid or the turbo itself or a crack in the vacuum line somewhere. All these should give an error code for underboost though.

flanagaj · 30-12-2020, 10:34 AM

(29-12-2020, 07:21 PM)Zion Wrote: Intake manifold, can't remember if it reads absolute or gauge. If it's absolute, then you have no boost. If it reads gauge, then that's 1 bar. (14.4 actually but close enough) so hard to say. What does intake manifold pressure read when the ignition is on, but the engine not running? If zero, then it's gauge - if still 14 psi, then you have no boost.

I have just done a record data with the engine not running and it is reading the same (14 PSI) as it was when I was driving the vehicle. So that would suggest that the turbo has gone.

flanagaj · 30-12-2020, 10:47 AM

(30-12-2020, 10:18 AM)saskak Wrote:
(29-12-2020, 06:38 PM)flanagaj Wrote: Sorry, but I don't think my OBDII scanner provides that data. Can that not be deduced by the manifold pressure? The manifold pressure seems to be extremely close to atmospheric pressure. I have tested the waste gate is holding vacuum as if I push the waste gate in and hold my finger over the hole it stays in place.

It could be the turbo solenoid at the back of the engine, although this would not explain the noise. The wastegate could be working, but no vacuum supplied to it from the turbo solenoid. Does the wastegate rod move on startup and stay there?
Any OBDII scanner should provide boost and it should get to at least 1.5bars under load. Disconnect the vacuum line from the wastegate and see if it is the same lack of power, then you would know it is the solenoid or the turbo itself or a crack in the vacuum line somewhere. All these should give an error code for underboost though.

Thanks for that. Just for my own understanding when you start the engine should the vacuum solenoid pull the rod and close the wastegate. I assume with the wastegate closed you get maximum boost pressure?

**saskak** · (This post was last modified: 30-12-2020, 11:00 AM by saskak.)

(30-12-2020, 10:47 AM)flanagaj Wrote: Thanks for that. Just for my own understanding when you start the engine should the vacuum solenoid pull the rod and close the wastegate. I assume with the wastegate closed you get maximum boost pressure?

Yes, the solenoid should pull the wastegate on startup and keep it there, 2-3mm of rod movement or so. This is not the maximum, so it is not full boost.

**Sol** · 30-12-2020, 11:21 AM

With the wastegate closed and under full load you should get full boost. Looks like you're not getting any boost. That would explain the gutless engine but not the noise.

jj9 · 30-12-2020, 11:26 AM

Post #4 would explain the noise.

.

Login
Username:
Password:	Lost Password?
	Remember me