Turbo misfire

[robwright]

I am quite competent with turbo plumbing mate after having installed a Tial DPW myself. Give us a shout if you need fella.

 

[GPF]

There is no way that the cv, an mbc and the single port wastegate can work properly together.

If it really does have this combination, at 1 bar, it is obviously wrong so there's no point looking further straight away (eg draining the tank etc) - it's most likely the dme airflow based overboost protection cutting in as it sees too high an AFM voltage. (yes I know you said MAF but the DME won't know that).

As has already been said, you need to find out what chips it has, how the MAF has been implemented and tuned and check exactly how the plumbing has been configured.

I presume the misfire is real violent - like hitting the rev limiter?

Initially, turning the boost back down would seem the smart thing to do......

If it actually doesn't have this combination, then plugs/gaps would be my first suggestion, followed by coil, leads, cap, rotor arm. Then pump & filter.

Let us know how it goes?

 

[robwright]

I second that mate. Al the MBC as it is called is simply a pressure regulator unless it is a boost enhancer (which i am not too familiar with) in which case it still shouldn't be used with standard chips. You can set the MBC on a bench. All you need is a regulated air supply, which I believe you have. Set your air supply to 0.8 bar then feed it to the input of the regulator. Adjust the regulator until it just starts passing air. That should get you back to stock boost levels and in my opinion is a good place to start any diagnosis.

 

[sulzeruk]

Thanks for all the suggestions guys, I thought the combo was a bit odd, will let you know how I get on,
Alasdair

 

[GPF]

ORIGINAL: robwright

I second that mate.  Al the MBC as it is called is simply a pressure regulator unless it is a boost enhancer (which i am not too familiar with) in which case it still shouldn't be used with standard chips.

The boost enhancer (BE) is almost the opposite to an MBC.

As you say, an MBC is simply a pressure regulator so it passes full air pressure straight through up to it's set point after which it mimits the amount of air through to this set maximum pressure. This can therefore be used with a dual port wastegate to supplement the wastegate spring and set a higher boost level.

A boost enhancer lets NO air through until the pressure reaches the set point after which it lets the full air pressure through.

So the BE is supposed to be used to block the signal to the standard wastegate, thus preventing it gradually opening and enhancing the build up of boost. Setting the BE higher than standard will result in a boost spike and then fluctuating boost. Of course, if the WG spring is weak the BE will be less effective as the exhaust gasses themselves will push the wastegate open anyway by acting directly on the back of the valve.

Hope that helps?

 

[Hilux]

I presume the misfire is real violent - like hitting the rev limiter?

Initially, turning the boost back down would seem the smart thing to do......

If it actually doesn't have this combination, then plugs/gaps would be my first suggestion, followed by coil, leads, cap, rotor arm. Then pump & filter.

The soft cut is a misfire - Overboosting is like putting the brakes on.

Is it a misfire or like turning the engine off at full chat?

If its a misfire on the red line its the soft cut if its lower but on boost I`ll wager the plugs but as above it all needs to be top notch.

 

[sulzeruk]

As per the other thread, turned out to be the pressure pipe for the KLR ECU was crimped after an AFM gauage had been installed, I wonder if that was why the car had been sold???
Alasdair

 

[barks944]

The car will run fine with the KLR line disconnected assuming there is some external boost control such as MBC or EBC. Was the pressure line to the KLR completely blocked?

 

[sulzeruk]

It was bent at about 90 degrees so probably. I disconnected it from the banjo on the KLR and it was a struggle getting up from the back of the mounting cradle for the ecus,
Alasdair

 

[barks944]

By AFM gauge do you mean Boost gauge? Does the car still missfire with the boost line installed correctly?

As the KLR is blocked and the boost wasn't going crazy I'm guessing boost control is via a single port wastegate and manual boost controller. It's probably just bleeding off a bit of the boost pressure in the line to the wastegate to regulate boost. Can you trace the pressure line from the top of the wastegate?