can someone explain...

[Cambridge_pulsar]

I've been doing a boost leak test to try and solve a long running lack of power problem and this is what i've found... I couldn't get the boost above .17 kg/cm on my avcr, there are no obvious leaks, no hissing or signs of air escaping anywhere and I have by-passed the boost solenoid valve. I have removed most of the breather pipes and have a catch tank joined to the pipe on the right rear of the rocker cover venting to atmosphere. I tried blocking off the pipe going to the catch tank and tried again, this time it managed 0.3 but wouldn't go any higher, again with no obvious leaks. Now i'm assuming when you pressurise the intake system like this the throttle butterflys should be closed and no air should be going past? If not then it can't be right that I am effectively losing boost through the breather pipe on the rocker cover?

 

[youngsyp]

You're not losing any boost through the breather pipe, unless you've got a really strange issue with the inlet and exhaust valves !
By blocking the breather pipe off, you're pressurising the sump and bottom end, under the pistons. This could force the gasses past the piston rings etc...

I'd say that your actuator has had it, It's either jammed open, and therefore keeping the wastegate open or, the diaphragm inside has a large hole in it and won't hold the wastegate shut.

Paul

 

[Cambridge_pulsar]

I see, it holds boost ok, and with the avcr off it holds at about .65. If the actuator is stuck open where does the boost go (stupid question I know) Is there anyway to test your theory without removing the turbo?
cheers

 

[youngsyp]

I see, it holds boost ok, and with the avcr off it holds at about .65. If the actuator is stuck open where does the boost go (stupid question I know) Is there anyway to test your theory without removing the turbo?
cheers

I thought you said you couldn't get the boost above 0.17 kg/cm ?!

If the wastegate is jammed open, there is no boost to 'go' anywhere. The turbine in the turbo will only spin up to a very low speed and not be able to build boost on the compressor side !

As for testing, you could try and move the actuator arm in and out. If it moves, the wastegate isn't jammed.

To test if the diaphragm inside has a hole in it, put a short length of vacuum hose on the actuator vacuum port, suck on it and see if the actuator rod moves. Or, suck on it, keep the pressure in the pipe with your tongue and feel if there is any pressure 'sucking' on your tongue from the pipe !

If it holds 0.65 kg/cm with the AVCR off though, your wastegate and actuator are fine !

Paul

 

[Animaldaz]

if you pressurise the vac line going to the actuator then you should be able to see it open.

 

[pulsarboby]

To test if the diaphragm inside has a hole in it, put a short length of vacuum hose on the actuator vacuum port, suck on it and see if the actuator rod moves. Or, suck on it, keep the pressure in the pipe with your tongue and feel if there is any pressure 'sucking' on your tongue from the pipe !

If it holds 0.65 kg/cm with the AVCR off though, your wastegate and actuator are fine !

Paul

sorry paul but thats not true as the actuator works on positive pressure to open and not vacuum.
you would have to pressurise the pipe as opposed to sucking it!

 

[youngsyp]

you would have to pressurise the pipe as opposed to sucking it!

True, if you wanted to make the actuator rod move. You could still find a hole in the diaphragm by sucking on a hose attached to it though as, no pressure would build up between one side of the diaphragm and the other if it had a hole in it! ;-)

Paul

 

[Cambridge_pulsar]

Thanks for the replies, it holds boost ok when driving, it was when trying to pressurise the intake system that I couldn't get it above 0.17. Could it be that the wastegate isn't fully closed so when i'm trying to slowly pressurise the system it won't work but when driving it's not enough to stop it making boost...?

 

[youngsyp]

Thanks for the replies, it holds boost ok when driving, it was when trying to pressurise the intake system that I couldn't get it above 0.17. Could it be that the wastegate isn't fully closed so when i'm trying to slowly pressurise the system it won't work but when driving it's not enough to stop it making boost...?

Oh right, gotcha !

There are all manner of things that could prevent you pressurising the intake system, depending on how and what you're trying to pressurise.

Personally, I tried it a few years ago and gave up. I now understand why it didn't work the way I was trying it but, as I don't have any issues with the car, I've not tried again !

It might be quicker if you just told us what your symptoms are, for the problem you're having ?!

What is your vacuum reading at idle, when the engine is fully warm ?

What rpm level does the engine sit at when idling, when fully warm ?

Paul

 

[Cambridge_pulsar]

Ok here goes... for a long while it hasn't been running quite right, holding back slightly from about 5-6.5k kinda like the power curve flattens out instead of climbing up to peak power. Over the months i have replaced various parts and sorted a couple of small boost leaks which have improved it bit by bit but it's still not quite right. It makes and holds boost ok, doesn't hesitate or stutter. It feels pretty much the same whether on the 1.1 setting or standard boost.
Vacuum reading on start up is about 250mm/hg (think that's the measurement) rising to about 350 when warm. It idles pretty much perfectly at about 950 rpm

 

[Cambridge_pulsar]

I've done a compression test in the past which was fine, there's no play in the shaft of the turbo, doesn't smoke apart from the occasional puff on gear changes, doesn't use much oil, fault code check is 55 all clear.
I'm sure a half decent tuner could narrow it down by monitoring afr etc but I want the satisfaction of sorting it myself and am sure it's something simple...

cheers

 

[youngsyp]

That's great mate, just what I was looking for.

Firstly, I'd say your idle vacuum when warm is a bit high (not enough vacuum) as, mine sits at about 425-430 mm/hg.
With my recent exploits, I wonder if your AAC valve is sticking or playing up ?!

Do you know anyone with DataScan and the necesary cable ?

That won't affect boost and general running though.

Does the boost gauge actually get to 1.1bar when your peak boost level is set at that target ?

When was the last time your fuel filter was changed ?

Have you checked your TPS voltage when it's closed ? Just changing that by 0.05 volts made a noticable difference on my car. It smoothed out the entire rev range and made the throttle response slightly more aggressive along with the pull !

Paul

 

[Cambridge_pulsar]

I think the aac valve is definitely sticking as it runs rich when cold and can be quite hesitant but improves once its warmed up but like you say it shouldn't affect general running.
It normally spikes a bit but overall holds boost fairly well.
Fuel filter has been changed fairly recently with no difference.
I have set the tps using the avcr to measure it and it's set at a tad over 0.45v, I believe that to be correct?

 

[youngsyp]

I have set the tps using the avcr to measure it and it's set at a tad over 0.45v, I believe that to be correct?

That's one of your problems there !

I set mine to 0.50v, using a multi meter as described in the service manual. That was a real pain to set as, even the very slightest movements changed the reading.
Anyway.... I checked the AVCR afterwards as, I know the two measurements have never agreed, and it was showing something like 0.39v. Way off the actual reading at the TPS sub harness plug !

Have you tried a known good MAF, in place of your one ? I know Ant had a long running issue that was solved by changing his MAF iirc !

Paul

 

[Cambridge_pulsar]

Ok i'll try setting it with a multi meter tomorrow.
I have swapped the maf a while back with my mates old one that was happily running about 315bhp. I have since cleaned the contacts on the plug, re-earthed it and opened it up and cleaned the sensors so i'm happy that's not the problem.
The thing that confuses me is that the symptoms are the same on standard boost, if say the injectors were maxing out at peak revs on the 1.1 setting you would expect the symptoms to be lesser or non existant on standard boost.
Btw I have changed the ecu (for a mines unit), dizzy, cap, rotor arm, cleaned various earths and probably a fair few other things. Your help is appreciated.

 

[youngsyp]

Ok i'll try setting it with a multi meter tomorrow.
I have swapped the maf a while back with my mates old one that was happily running about 315bhp. I have since cleaned the contacts on the plug, re-earthed it and opened it up and cleaned the sensors so i'm happy that's not the problem.
The thing that confuses me is that the symptoms are the same on standard boost, if say the injectors were maxing out at peak revs on the 1.1 setting you would expect the symptoms to be lesser or non existant on standard boost.
Btw I have changed the ecu (for a mines unit), dizzy, cap, rotor arm, cleaned various earths and probably a fair few other things. Your help is appreciated.

It definitely sounds like a fuelling issue.

Is the ecu on the car now, the Mines unit ? If so, could you change back to the stock unit as a few people have mentioned rough running with Mines ecu's recently !

Do you have a high flow fuel pump ? If you do, is it on the same loom as the stock one ? Or has it been rewired to get full alternator voltage ?

Your injectors won't be maxxed out at 1.1 bar..... When I say that, I mean that they maybe at 100% duty because the ecu has gone off the fuelling load map but, they'll be supplying enough fuel for the engines needs.
That's my take on it anyway and I'm sure some will disagree !

My car was putting out 318 bhp when it was last dynoed at 1.1 bar (and supposedly running lean although, it was on the original, 95k miles old stock fuel pump).
With everything 100% now, it runs a dream. That's with basic mods and still running the stock TMIC.
I had a niggling problem like yours so, know how it feels !

I'm not that far from you, if you're still in Cambridge so, if you run out of ideas, please feel free to come over and I'll plug the DataScan into it and see if anything comes up !

Paul

I'm sure you

 

[Animaldaz]

Sorry for the hijack, Paul did you set your TPS with the TMIC insitu? And the engine running?

 

[youngsyp]

Sorry for the hijack, Paul did you set your TPS with the TMIC insitu? And the engine running?

No matey I had to remove the TMIC. It's not possible to set the TPS unless you remove a bracket that supports the power transistor for the ignition, that would be a pain to remove with the TMIC in place.

You don't need the engine running either. You just need the ignition set to 'on', so the TPS has power going to it !

Paul

 

[Animaldaz]

Cool thanks Paul, think i read somewhere it was better to have the engine idling but as you say i shouldnt matter.
Next time the ARC is off ill check this.

 

[Cambridge_pulsar]

I do agree with what you're saying, it sounds like a fuelling issue. I have an uprated fuel pump and have re-wired it direct to the battery. I was just using the injectors as an example, if one component is struggling on standard boost I would expect the problem to be worse on a higher boost setting.
Swapping the ecu's hasn't changed anything, although i'd say it runs a bit better with the mines unit. Where abouts are you, I may take you up on that offer!