No power on full throttle

[timnutt]

Hi,
I thought I'd start a new thread rather than continuing the discussion on my MOT emissions thread.

My boost gauge is a little confusing (to me ). See picture. There are two scales of pressure mm/Hg (millimetres of mercury) and kg/cm2. From what I've read the lower one shows manifold vacuum pressure, which at tick-over is around 500mm/Hg (9.6 psi), and the upper one is the turbo boost which gets to around 0.7 kg/cm2 (10psi).

If I slowly increase my revs in 2nd gear the boost increases and the car starts to accelerate nicely. However, when I put my foot to the floor the revs stop increasing and there is no power.

To rule out a problem with the boost controller I by-passed it by connecting the turbo vac directly to the waste gate actuator - no difference to the power problem.

So, I'm guessing that when you floor it the ECU isn't keeping up and adding enough fuel so the mixture is so lean there is no power. Correct...? Before the engine rebuild everything was working fine, so not sure what has changed or how to troubleshoot/fix it.

Many thanks!
Tim

[notroubleclubber]

Id say there is a crack or vacumn leak.

Doesnt sound fuel related at all

[jimi]

The two scales measure the same thing - pressure, just in different units.
Your getting no boost, 9.6psi at idle to 10 psi when accelerating, so something is stopping the turbo building pressure which is why you have no power, the ECU will only add fuel in response to the increase in inlet pressure. Your only getting. 0.4 psi of an increase !

[timnutt]

OK gauge makes sense now.
So, could the turbo be knackered? When I take the air intake of the turbo, the compressor wheel spins fine with no play, but there is a little oil in the intake, which isn't good, but does that mean a dead turbo. I don't want to buy a new one or get it reconditioned just to find it something else.

Other posts I've read talk about fuel starvation and a dying fuel pump. I did change the fuel filter as part of the rebuild.

Arrrrgghhh. Just don't know where to start.
Thanks!

[Snorkie]

Hi, are you saying that at idle you are getting 500mm/hg vacuum and positive pressure of 10psi when you put your foot down, if so that's right and rules out the turbo.

One question, does it hold 10psi all the way to max revs or does the pressure drop as the revs rise.


I hate all these metric scales, I can use metric for most things but always end up converting back to imperial for pressures ( The fact that I'm 54 might have something to do with it).

[MR2DI4]

I presume you took the photo above with the car running and just at idle ?

With the car turned off and if you still have power to the gauge it will read zero ?

and then you get up to 10psi of boost, which is normal with the vac line from the turbo compressor straight to the wastegate actuator.

What sort of boost controller do you have ? doesn't sound like the vac line plumbing is right or its not adjusted, is it a manual boost controller ?

[timnutt]

Yes, the photo is taken at idle. When I turn off the ignition, the needle goes to Zero.
The boost controller is an Apexi solenoid, just like this one on ebay:
https://www.ebay.com/itm/Apexi-Electron ... 3689871423
It is controlled by the Apexi PowerController ECU. Maybe I need to reset the ECU.

I bypassed the solenoid, by connecting turbo compressor straight to the wastegate actuator, and get the same problem, so ruled out the boost controller.

I'm going to take it out again tomorrow and run it up the motorway - easier to keep an eye on the boost controller - might try and video it.
So close... but so far
Thanks
Tim

[MR2DI4]

I stuck to an MBC, it is a "Trust" rippoff made in China. Probably one of the better extreemly cheap things I have purchased from China.Looks like you can still buy the Genuine artical and its not that expensive.

https://www.ebay.com/itm/GReddy-Profec- ... Sw8zRcNWzq

Electronic sounds great but air pressure is quite hard to control, you need multiport solenoids and even then its quite hard to configure. Keeping it all analogue with a ball and spring or a bleeder type really makes it easy. I presume you have blocked off the second vac line from the wastegate actuator, or did what I did and simply cut the wire at the stock engine ECU that opened the stock bleeder valve ?

Electronic can potentially get you more midrange power by holding the wastegate closed longer but there is no difference at the top end.

[timnutt]

Hi,

I videoed the boost gauge. All in 2nd gear, first part is accelerating slowly up to 4000 revs, clearly very little boost and car runs fine.
2nd part is full throttle and as you can see the boost gauge shows 0.9kg/cm2 = 12.8 PSI, but there is no power, and the engine eventually gets up to 5000 revs

Video: https://youtu.be/K4LmRV-9rIA

So, it looks like the turbo is producing boost, but no power leads me to think the mixture is completely wrong... What can I check next to figure this out?

Thanks!
TimN

[notroubleclubber]

The second time u accelerate it looks like your getting boost fine?

[timnutt]

Yes, I know. But the speed and rev slowly creeps up with no power. Someone mentioned it might be fuel starvation from dodge fuel pump or incorrect fuel filter (pretty sure I bought a Toyota Filter when I replaced it.)
I'm not sure where to start troubleshooting. Fuel? Sparks? Vaccum? ECU?
Thanks

[MR2DI4]

Your doing a test with a cold engine.

You need an AFR gauge or your just guessing as to the fueling. A boost gauge actually tells you nothing other than the Turbo is producing boost, its missing the other vital parameter, your fueling.

From my experience, its pretty hard getting boost in second gear even up hills the engine pulls so hard anyway and is reving so hard it doesn't seem to get the loading to require it.

Third gear is the best, it just snaps to full boost on acceleration and pulls like mad.

I guess its what your used to driving, I mean its not 500Hp is it ? if I owned more powerful cars perhaps my perspective would change.

If its making boost and the AFR's are okay then it is what it is. You can check the timing pretty easily with a strobe light and two pins in the diagnostic box shorted to get the "Static" timing right after that the ECU looks after it all.

These cars are getting pretty old and many of the engines are just plain worn out and also the heads in particular would need a clean and rebuild. The engine could be full of carbon buildup on the piston and head and crud all over the valves reducing the flow Severely. You would need to put it on a Dyno to sort out what its doing.

Even a good stock Rev 2 engine in good shape would only be at about 200Hp.

[Snorkie]

Check the cam timing is not a tooth out. It sounds right, just gutless.

[MR2DI4]

Check the cam timing is not a tooth out. It sounds right, just gutless.

Well put, not that easy to check on the 3S-GTE however. Those cams walk when you pull the old belt off so your mad not to mark the positions first with a permanent marker pen. I think there are factory cam marks but at the bottom of the cams so its really a pain to check with the engine in the car.

Probably even more likely than a bad fuel pump ? the engine would have probably gone bang by now if it was fuel starvation.