8V Turbo Fuel Cut On Overboost?

[peter 20]

does this actually happen? ive wired my fuel pump to an ignition live but yet a few seconds after 1.1bar of boost it feels like you hit a brick wall?

 

This must be the ignition getting cut by the ecu?

 

Does anyone know what actually happens when the ecu 'sees' too much boost?

 

Even with the map sensor in the ecu discnnected it still does it, or maybe there is another sensor that causes it to kill the ignition?

 

id love to read and understand whats going on in the ecu!

[luke1987 5]

The knock sensor will adjust the ignition when it senses the engine going lean which is what it sounds like is happening as the ecu has no idea of the boost with the map disconected.

[peter 20]

that sounds reasonable, but if the engine wasnt lean and therefore not 'knocking' would it still kill the ignition?

 

 

ill try disconnecting it

[peter 20]

Well either way its just melted the pistons

 

So experts what causes the ecu to spit its dummy out at anything over 1.1bar? infact what does it actually detect and then what does it do to stop the engine melting the pistons?

[luke1987 5]

The ecu cuts fuel at anything over a bar as the map sensor is only a 1bar sensor so any pressure over that cannot be read by the ecu. So when the ecu sees this pressure achieved it cuts the fuel at the injectors and may cut the ignition which is why it feels like you hit a brick wall.

 

 

 

 

 

[peter 20]

That would make sense but it still does it with the map sensor unplugged.

 

Ive tried it just to see what happens, it apears to just come on boost then constantly misfire and wont pull, but on light load and little boost it will.

 

So im guessing that the ignition is too advanced when the ecu doesnt see boost so it cant cope and probably detonates

[Tom Fenton 1,542]

I'd say it is more likely that it is detonating due to being far too lean. The ECU relies on the MAP sensor to get the enrichment right for boost. Ignition timing will also play a part but it is fuel (too lean) that is the main cause of det under load/boost.

 

I also doubt that the overboost function cuts fuel, this is a dangerous place to be as you are at over 1 bar and all of a sudden the ECU removes fuel to go mega lean? More likely is an ignition cut in my mind, and having driven one, the way it very suddenly hits a wall seems like ignition to me.

[peter 20]

but how can it do that with the MAP sensor unplugged?

 

what are the 3 sensors on the throttle body? air flow meter, tps, and?

[welshpug 1,661]

these engine management systems don't have an air flow meter.

 

on the throttle body you have the yellow plug which is the throttle heater,

 

grey or white 2 pin, inlet air temperature,

 

and the 3 pin on the end of the spindle is the throttle position sensor.

 

as well as those you have a Map sensor inside the ecu, a knock sensor bolted to the front of the block, Coolant temperature sensor in the thermostat housing, and the boost solenoids.

[peter 20]

what does the throttle heater do? i though that was the maf

 

How does it know how much fuel to put in then? just from the map sensor, throttle position, rpm? and temp obviously

[welshpug 1,661]

it heats the throttle body.

[peter 20]

why?

 

To stop 'carb iceing'?

[Henry Yorke 269 3 Cars]

It sounds like you are doing the classic "wind the boost up on a 2.0T to more than the ECU can handle and then wonder why it isn't running right and goes bang". It is an expensive way to discover what works and doesn't!!

 

The standard 2.0T ECU can give you a lot of readings on temperatures etc if you plug it into a diagnostics system.

 

If you want to run more than 1 bar boost on a 2.0T then you need a proper ECU. Unplugging things to try and fool the ECU will just cause it to flag up an error and go onto a basic mode. If it didn't make a difference, Peugeot will not have fitted it. You can run 0.8 bar pretty reliably on the standard ECU with a remap, but this changes lots of settings in the map to enable this.

 

If you want to understand what is going on in the ECU, then this is a good book, though it can be a hard slog http://www.amazon.co...41873129&sr=8-1

 

Don't forget the boost is often dependent on the condition of your turbo too. I would not like to run higher boost through a 130k miles turbo as they are often a bit tired.

[Miles 331 1 Cars]

As said without a MAP sensor the engine will run like a bag of *****, I should be right in saying that all Petrol Turbo's run one, Think of it like this, Block your nose off and go for a run, you won't get very far