Fixing the overboost issues with the MN 2.5HP

[hogdogger]

So after reading though this thread I am guess I'm in the same boat as most of you. Over boosting. Just got my mn back from having the head done quickly threw my 3" exhaust back on drove it no more than 100k dropped the boot in up a hill heading home pulling about 120 in 4th then I heard a slight pop sound ( the same as when ur intercooler hose comes off) lost all power had traction control lights come on and some other light like a square lookin box thing. Had no choice but to pull over flicked the motor off rang the dealership for them to send out a tow truck. Out of curiosity I started it up again and noticed I only had the 1 light on drove it another 100m and it was giving me boost as such but I wasn't game enough to risk the rest of the trip home so I waited for the tow truck. I'm guessing it over boosted and went into "limp mode " please not that I haven't owned this POS no more than 3 months and so far it's spent 1 month of that time in a work shop getting constant problems fixed. I guess I won't hear for a few days what they suppose is wrong with it but I'm putting it down to over boost causing it to go into limp mode! Anyone agree? Any other problems that may cause this?

[har05l]

Your exhaust caused it and nothing else mate, you'll probably get the same answer off the dealer if they know there product.


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[MilkmanDan]

I have a theory, how do the vgt actuators work on the 2.5? Ecu controlled?

[Cowboy Dave]

Yeah with vacuum I think it is.

[hogdogger]

My question is why? There are blokes here who have this trouble with a stock exhaust why does a 3" trigger it more frequently? I was always under the impression for instance if you running 10psi boost it's suppose to stay at 10psi no matter how big ur exhaust is or how much boot your dropping down. Why is it that triton can fluctuate with their boost output? Isn't that why the 3lt patrols blow up? Because something doesnt register how much boost their getting then they pop from too much boost? Correct me if I'm wrong just can't seem to understand why they over boost

[Cowboy Dave]

I'll preface what follows with this caveat, I'm a total amateur so don't assume this is gospel. But it will be closer than what you've said above.

The MN triton (unlike the ML) runs a Variable Geometry Turbo (VGT for short). This means in effect that the fan blades of the turbo can be made to spin at different rates according to how much boost the ECU demands. This is controlled with the actuator which is vacuum activated. You can see the actuator move up and down if you look from the driver's side and have someone rev the engine.

The ECU determines how much boost the turbo is providing via the MAP sensor (manifold absolute pressure) which is connected to the blue plug on the passenger side near the firewall.

The blades/impellers on the turbo are propelled by the force of moving exhaust gases. The flow rates are important and part of the design. By changing the exhaust you change the exhaust flow rates outside the design rates. In some cases the ECU can't deal with the fluctuations. If a VGT is allowed to go beyond its parameters I gather it can eventually self destruct. If the ECU thinks it has gone beyond what was asked then it shuts it down as a safety move - you wouldn't want to be stuck in a car that was boosting at a constant 30 PSI and couldn't be stopped I suppose.

Some exhaust manufacturers will tell you that a 200 cell cat or a certain muffler will prevent the problem. This may be true in some specific cases but testing and forum experience suggests that as a general proposition it is not true.

Yes it happens with some stock cars. You can't expect Mitsubishi to care about yours unless you put it back to stock and prove that yours is one that it happens to in stock form. At the moment it is not a warranty case at all, rather a problem created by an owner's modification. As to why it happens to stock cars, well I gather that is still a bit of a mystery. If you can come up with an answer you might well make some money out of it, especially if the answer comes with a fix for the problem.

There are aftermarket ways to decrease the risk of it occurring substantially - read up on the use of Dawes valves if you're headed in that direction.

[hvac guy]

I could be totally wrong here but i thought i seen the overboost looks at the maf and boost pressure. So if you increase the efficiency (less back pressure) of the turbo you get more cfm at the same boost levels.

[srb]

I could be totally wrong here but i thought i seen the overboost looks at the maf and boost pressure. So if you increase the efficiency (less back pressure) of the turbo you get more cfm at the same boost levels.

On the right track here.

[hogdogger]

So the question then is 8f the mn turbo waste gate is controlled by the ecu the would changing the turbo over to one that has a manual waste gate solve the problem? Just throwing ideas around seeing if I can think of a fix. There was a write up on a Pajero page they had over boost problem and fixed it by shortening the acuator arm. I would upload a photo of what they exactly did but cant figure out how. Seeing the Pajero and triton run the same donks it could be a solution

[L200Shogun]

MN are VGT no waste gate

So the question then is 8f the mn turbo waste gate is controlled by the ecu the would changing the turbo over to one that has a manual waste gate solve the problem? Just throwing ideas around seeing if I can think of a fix. There was a write up on a Pajero page they had over boost problem and fixed it by shortening the acuator arm. I would upload a photo of what they exactly did but cant figure out how. Seeing the Pajero and triton run the same donks it could be a solution

Page 1 or this is another way viewtopic.php?f=97&t=19507&hilit=roo+systems&start=50

[Cowboy Dave]

You could theoretically stuff around with the actuator in order to reduce your maximum boost, but you'd suffer a performance loss.

The ML had a 3.2 with a wastegate turbo. The pajeros you are probably reading about had a 3.2 with a vgt turbo and your MN has a 2.5 with a different vgt turbo.

So not really the same donks despite some similarities here and there.

[Cowboy Dave]

The Dawes valve is your best option as a first step. Unfortunately the best vendor of those won't be able to sell you one for a few weeks at least.

[hogdogger]

Would it be possible to run a 3.2 turn with manual waste gate on a 2.5 or another aftermarket turbo with manual waste gate. Not so much worried about a performance loss more worried about reliability being 1000k away from home which I normally am a few times a year could be a real pain if it over boosted and threw codes flat out. Who has a Dawes vavule set up and it stops it? I could swear I read of people who had them set up and it still over boosted

[Cowboy Dave]

There are some rare vehicles that don't behave but that is more often than not user error in the setup or an indication that there is something else wrong in the system - eg a faulty sensor.

The thing to remember is that it only happens with a constant throttle for a sustained length of time usually up a hill or towing and usually you have to be right up it. Somewhere among the 200 odd posts in this thread is a post where Tony explains the parameters in terms of how long it takes to hit. If during that time period you vary the throttle then 9 times out of 10 it won't overboost.

Your scenario where you get stuck just won't happen. Unless every time you restart you start going flat out up a hill again without remembering to drive around the issue.

There is some experimentation going on with different turbos but I can't tell you where that's up to. I can't see how you could go with a non-vgt turbo unless you find a way to lie to the ECU about what's going on because at the moment it is looking for certain input from certain sensors and that input just won't be there any more.

[Stoneman]

The Dawes valve is your best option as a first step. Unfortunately the best vendor of those won't be able to sell you one for a few weeks at least.

Or you can go direct to the supplier
http://3barracing.com
I brought mine from them and I have one with the upgraded ball in it

[hogdogger]

Thanks for that info Cowboy dave! It's under inspection to see what can be done about it but half the mechanics know sweet FA about these sort of problems hence why I joined this forum.and yes I was hard up it. Does it just come up with the CEL light after u switch it off n back on then drive normal? I wasn't game enough to risk it

Stoneman. Does it stop it from.over boosting? Does it make any difference at all?

[srb]

Yes, it would be possible to do that... but why would anyone want the pissy little turbo off the 3.2?

As CD has already said... Dawes valve from spvi is ya best bet and will go along way to fixing the issue on a stock vehicle. Although if you're running a 3" exhaust and chip then it won't always eliminate the limp mode. The ecu freaks out with the extra volume of air that is flowing.

Rumour has it that Spvi might be releasing some new chip that will incorporate a complete fix for the issue.

[Cowboy Dave]

SRB has had more time playing around with his Dawes setup than anyone. Don't forget I have that final link for the new turbo hose here for you Steve.

As to the other question, yeah you just get the check engine light and from memory it will go away eventually but most people just clear it with a scangauge or equivalent. It's safe to drive and the code will get stored in memory for the techs to see next time you take it to the dealers.

[Stoneman]

Thanks for that info Cowboy dave! It's under inspection to see what can be done about it but half the mechanics know sweet FA about these sort of problems hence why I joined this forum.and yes I was hard up it. Does it just come up with the CEL light after u switch it off n back on then drive normal? I wasn't game enough to risk it

Stoneman. Does it stop it from.over boosting? Does it make any difference at all?

Sorry hotdogger I've never had the problem and I run a 3" with a 200 cell cat by pacemaker exhausts

Well I think it's a 200 cell.

[Tony]

All a bit hit and miss, the finer 200 Cel cat does help as more restrictive and therefor reduces the overall CFM.


We have just opened up another channel on the power chips we use so can deal with this issue with out any compromise on the freak vehicles by unlocking the airflow and boost together. All plug and play too.
Two prototypes out in action now.

[OffRoadDave]

Just a quick question regarding the limp mode, does it show a engine light on the dash?

I was giving my stock Triton a bit of curry Friday night before backing off a pulling into the driveway, and it all appeared ok at the time but when I took off Saturday morning it's a gutless wonder, only see about 3-5 psi on the scangauge and it shows no codes.

Had a quick look under the bonnet for any hoses off or plugs undone but everything appears normal on that front.

Does this sound like limp mode and I just backed off around the same time it coded or something else?

[Stoneman]

It's been mentioned on the pajero forum that some dealers are pointing at the snorkel as the issue?

How many people that have the problem have snorkels?

[hogdogger]

Yep. Got a snorkle.

[borngeek]

Lol well the dealer selling that crap is a numpty. The person that believes it being a bigger one.

Just saying.

[Stoneman]

Lol well the dealer selling that crap is a numpty. The person that believes it being a bigger one.

Just saying.

Not saying I believe it but you seem pretty sure it couldn't be the issue, care to explain why any one that believes it is a numpty

If it was me with the issue I would want to know why it's happening before I go trying to bypass it....just saying.

I don't have the issue and I don't have a snorkel

From what tony has said unlocking the air flow it doesn't seem that far fetched