Overboosting and ecu cutting (video inc)

[GrahamS]

Firstly it's a DCi, not in the title to lure you petrol turbo people in too! It's almost the same thing

Since I've had the car the coil light has always come on when flat out on the motorway. I fitted a boost guage a couple of days ago and have now been able to witness what happens. Always happens when on a steep incline and you can see the boost climb until it reaches a rather high level. The engine management kicks in to drop it down as you can see at the end of the video (I also take my foot off the accelerator). The ecu normally cuts boost back to a bar and then it build again and the ecu steps in. Under normal pedal to the metal action it sits at 1 bar which is what the standard renault map is meant to do and this only occurs when tanking it.

If anyone can help me solve that would be great as I'm going for a very long trip in the summer.

Thanks chaps.

 

[sburrell93]

My first thoughts are that the wastegate isn't opening properly. So the car is overboosting, then when it climbs above a certain point, the ECU goes "woah f**k that!" cuts back fuel (bringing the coil light on), and so the boost drops back. Does that sound remotely plausible? Lol.

 

[GrahamS]

My first thoughts are that the wastegate isn't opening properly. So the car is overboosting, then when it climbs above a certain point, the ECU goes "woah f**k that!" cuts back fuel (bringing the coil light on), and so the boost drops back. Does that sound remotely plausible? Lol.

That was my thoughts as well so makes total sense! I couldn't quite work out why it wouldn't have this problem lower down in the gear range but guess it's injecting a lot more fuel in to achieve the same revs when at speed so the gas volume is much bigger. I'll swap the wastegate this weekend. It's been doing it for 40k but the boost gauge has made it obvious I need to sort it. I think "woah f**k that!" before the ECU is, I'm a pussy.

Any other ideas floating about?

 

[sburrell93]

Lol! Better safe than sorry I guess :tongueout:

I can't remember on the 65's, is the wastegate controlled with an adjustable rod type thing (worst description ever) coming from an actuator? I'm just thinking if that's the case, maybe someone's adjusted it in the past to try and up the boost like what could be done on older diesels (Pug 306 D turbo springs to mind), without altering the mapping to suit, so the ECU isn't liking it.

 

[GrahamS]

Lol! Better safe than sorry I guess :tongueout:

I can't remember on the 65's, is the wastegate controlled with an adjustable rod type thing (worst description ever) coming from an actuator? I'm just thinking if that's the case, maybe someone's adjusted it in the past to try and up the boost like what could be done on older diesels (Pug 306 D turbo springs to mind), without altering the mapping to suit, so the ECU isn't liking it.

a rod type thing is what it is. I went to adjust it last weekend and it's got all the original Renault red thread mark on it. Look at the first page of my project thread. Noone would try and up the boost on that piece of crap

 

[scooby-93]

It's over boosting, if there is a light comes on when you hit the cut get a code reader or clip on it, it's boosting over what the ecu wants it to, is it worse in higher gears and under heavier load?

 

[GrahamS]

It's over boosting, if there is a light comes on when you hit the cut get a code reader or clip on it, it's boosting over what the ecu wants it to, is it worse in higher gears and under heavier load?

will plug into clip tomorrow although it's never yielded a code in the past. Yeah, as above, it only happens when going flat out on the motorway.

 

[scooby-93]

Yeah sorry just re read it after posting? It's boosting above what the ecu can handle, if it's been mapped it has had the target boost set to high, beyond what the ecu can control that's why it's hitting a cut

 

[GrahamS]

@scooby-93 it hasn't been mapped mate. Completely factory ecu unfortunately! The only mods it has is a DCI 80 intercooler and decat which actually made the point at which it does this a little later.

Just found this on a WRX forum which does add up "Sounds like you either have a manual boost controller, or a wastegate that won't open."

 

[AlexW]

Make sure you can move the wastegate by hand. Although as its only sometimes its odd, too much fuel would cause the same issue tooo....

Bit of live data needs to be checked really.

 

[Dr HMS Derv Destroyer]

Little coil light will be the ecu backing the fueling off, it's not a major issue so it won't fault code.

I've had it for a long time but mapping it sorted it until the point I'm at now where the demand for fuel is not acceptable.

Most of this will be down to the map sensor can't read anymore than it's made for ( don't quote me wrong never actaully looked at what it's ratings are )

I've found a thicker hose for the actuator has helped a lot on some of the 1.5s I've seen through this garage.

Standard pipe is shocking and in a stupid route that restricts it a little

 

[AlexW]

Map sensor maxes out at 1.25 bar in my experiance IIRC.

 

[GrahamS]

Right chaps. 2 things I'm thinking of doing. First is replacing the actuator as it's clearly now disposing of enough gas, especially when load on the engine is at its highest.

Is there a difference between the two map sensors fitted to these. I currently have this map sensor http://www.ebay.co.uk/itm/MAP-PRESS...777?pt=LH_DefaultDomain_3&hash=item5ae54139f1 but have a spare http://www.ebay.co.uk/itm/Renault-K...arts_Vehicles_CarParts_SM&hash=item339d079457

Second is . Is it the map which stops at 1.25 bar or the map sensor as I believe the second sensor is a higher pressure rating? I will swap the sensor for this new one if it's the sensor.

 

[sburrell93]

Yep, that second sensor looks identical to the one on my dci 100, so I'd bet it has a higher pressure rating (they run 1.25 bar standard).

 

[AlexW]

They don't swap either as plugs are different, think they are wired up in a different order too (don't quote me on that).

I wouldn't replace the actuator if it moves, theres also a poss of the penny gate in the turbo being at fault rather than the external actuator.

 

[GrahamS]

Yep, that second sensor looks identical to the one on my dci 100, so I'd bet it has a higher pressure rating (they run 1.25 bar standard).

Ahh perfect. I believe the other one is maybe rated higher but worth trying.

They don't swap either as plugs are different, think they are wired up in a different order too (don't quote me on that).

I wouldn't replace the actuator if it moves, theres also a poss of the penny gate in the turbo being at fault rather than the external actuator.

Yeah I know mate. I snipped the plug when I had that 80 for a while. The kangoo runs one so I'll check the connections before plugging it in. Will check if it moves before replacing it, the gate obviously isn't working correctly to have excessive pressure build up. Turbo needs replacing really but house>clio

 

[AlexW]

Fuel can effect boost pressure aswell.

 

[GrahamS]

To finish this thread off. It was the wastgate. New wastegate and no problems at all now.