Fixing the overboost issues with the MN 2.5HP

Fixing the overboost issues with the MN 2.5HP

Postby Tony on Sat Sep 22, 2012 7:09 pm

Hi everyone, I have taken it upon myself to start a new topic for this as will hopefully help people in the future should this issue arise.

This problem is rare, but does occur with a small percentage of electronic solenoid over vacuum variable geometry turbo systems such as the 2.5HP MN Triton.

I have personally come across a few people (including some dealers) that are at a loss with this over boost condition that some of these Variable Geometry Turbo equipped vehicles can experience so want to bring the use of a pneumatic control valve to light as many of the Nissan ZD30 hand grenade engine owners have in place now. They tend to blow up at a sniff of boost over 18psi as in detonate. :shock: Also many other reasons, such as EGR blanking which raises the EGT's with the vehicles ECU software as it now cant draw the air though the EGR valve and EGR cooler. The air fuel ratio drops to dangerous levels. This happens with the MN's too, only the engine is tough enough to tolerate it for a long time. 8-)

Back on topic, the overboost issue often crops up with a mix of stock vehicles, big bore exhaust systems, EGR blanking and ramping up the fuel by chip or tune with no map sensor clamping. On that topic, I have found it is not possible to totally clamp the MAP sensor voltage below 22psi on the MN's as this may cause the turbo to remain in attack and run away before the ECU can catch it. :!:

The symptoms are bought on by a very long and hard higher RPM run (over eight seconds) usually towing or when overtaking then the vehicle will go into limp mode showing a CEL. Most scan tools wont read or clear this particular fault. Code is MN triton specific P1298 (VGT system over pressure.)

What we are seeing is a large boost spike as the turbo spools up much quicker than the ECU can control the actuator via the electronic over vacuum solenoid. The said solenoids main purpose is to control ramp up of the turbo and assist with new strict emission laws by dropping the pressure whilst the EGR is active and TB is partially closed etc..

This modification I'm showing in this particular thread has no effect on the way the electronic solenoid works or emission control except simply pushes positive boost into the vacuum side of the VGT actuator should it ever over boost hence brings the boost back to target till the electronic over vacuum solenoid catches up.

The said modification is fitting a "Dawes" type valve to the vacuum line between the electronic over vacuum solenoid (after the damper) and the VGT actuator and feeding positive boost pressure to the valve from a tee in the MAP sensor line. (Closer to the inlet manifold the better)

The valve is specific for this application as has a tee on the bleed side and single barb on the boost side, it works with a ball and spring as some other pneumatic boost controllers only has no air bleed holes in the valve body on the turbo actuator side. They wont work in this application as will allow the vacuum to escape. This is a closed system, not vented. (we do not use a bleed when backing up the electronic solenoid.)

I hope this diagram makes sense.
Dawes backup.jpg

What you can see is, it runs stock until the valve bleeds pressure in to prevent boost spikes or turbo runaway at the users setting. This mod works on stock, chipped and tuned vehicles.

dawes type valve mod 2.5.jpg


Dawes type valve map in.jpg


These valves will soon be available though Chipit NTN amongst other items on special request.

I will add, this valve can be used with out the Electronic over vacuum solenoid with many advantages if you wish, but requires a damper and bleed valve to work nicely. There is a bit in the platinum area on this. 8-)

Regards Tony
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Re: Fixing the overboost issues with the MN 2.5HP

Postby daryn on Sat Sep 22, 2012 7:54 pm

I presume this would work if needed for Vgt pajeros too Dave ?

Good post mate. :D
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Tony on Sat Sep 22, 2012 8:10 pm

Yes, works on the Pajero.

Works on any vehicle fitted with a vacuum operated VGT actuator. 8-)
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Re: Fixing the overboost issues with the MN 2.5HP

Postby snowman on Sat Sep 22, 2012 8:49 pm

Nice post :D Dave :? :? :lol:
This car is like a bad drug habit. It is taking all my money and time, my family are concerned, but new mods just feel sooooooo good.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby JoanTheSpark on Sun Sep 23, 2012 1:43 am

Wouldn't the effect of that mod be to shut down the VGT suddenly (and hard) once the pressure goes slightly above xy psi at the MAP line?
Is that good/tolerable (*)?

*) I'm just imaging a ute going for an overtaking maneuver.. admittedly, a limp/CEL isn't that cool for this either

PS: in the end it only tells me one thing.. if one mods/blocks the EGR system + tries to push more fuel/air into the engine one is responsible for the MAP too.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby LJOS on Sun Sep 23, 2012 6:13 am

And the minute the stealers see this on your vehicle they are gonna shout 'VOID WARRANTY' aren't they?
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Tony on Sun Sep 23, 2012 9:22 am

JoanTheSpark wrote:Wouldn't the effect of that mod be to shut down the VGT suddenly (and hard) once the pressure goes slightly above xy psi at the MAP line?

Is that good/tolerable (*)? The dawes valve is a ball and spring so in effect leaks the positive pressure back when hitting the xy pressure point. The boost curve is much more linear and does not fall off suddenly at any point. .

*) I'm just imaging a ute going for an overtaking maneuver.. admittedly, a limp/CEL isn't that cool for this either
This mod is 100% fail safe for overtaking etc.

PS: in the end it only tells me one thing.. if one mods/blocks the EGR system + tries to push more fuel/air into the engine one is responsible for the MAP too.


This one is hard to explain, blanking the EGR has two major effects other than the obvious. :roll:
When the egr kicks in, the TB cranks partially closed, the ECU ramps the boost back via the electronic solenoid (Why some see EGTs rise under light loads) This all helps the engine ingest cooled exhaust gas, Blanking the EGR now means the gas has to all come past the TB and now low psi turbo hence EGTS must rise and fuel usage goes up. This kills the Nissan engines very quickly. :lol: This mod in this thread does not fix the EGR over fuel issue as the electronic solenoid is still in place.
Blanking the EGR also seems to have the tendency of triggering the overboost CEL on some MN's. If you look at the fixes for this, one does suggest not enough EGR.

Pushing more fuel in and larger exhaust etc does increase the air flow as the turbo spools harder at the same nozzle angle, this can upset the software that manages the VGT causing turbo over shoot. Its possible to adjust the actuator arm to help compensate this issue.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Tony on Sun Sep 23, 2012 9:40 am

LJOS wrote:And the minute the stealers see this on your vehicle they are gonna shout 'VOID WARRANTY' aren't they?


So long as the electronic solenoid is left in place, there is no way this mod can do any harm, if anything, it's safer for the engine.

On that note, there are two tritons in my area that have this overboost issue that the dealers nor MMAL have been able to fix with software updates which is why I have taken it upon my self to make this work.
It can not harm the engine as 100% fail safe with the electronic solenoid still in place. The valve just backs it up. does not increase pressure of stress on the engine in any way.

This mod is here for those that come across the overboost issue that dealers or MMAL can not fix for you in some cases.

I know of one vehicle in the Mudgee area was bought back off the customer as the issue could not be resolved.
The others just get sent back out there. :roll:
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Mitstech2936 on Sun Sep 23, 2012 7:51 pm

The dealer ecu update that they are trying to fix that with is for p1299 (under boosting @ high altitude) not overboosting, I'm pretty sure the max parameters that there meant to be at is 237mpa and I have seen them up round the 260mpa mark,
Top write mate good to see a fix to the problem
As some of you would know I wrote a remark previously about steering away from
Chipping vehicles whilst under warranty due to the vgt system freaking out!
If only mitsu warranty could see it with your mind and hope that could be an avenue to go down so customers can do mods
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Re: Fixing the overboost issues with the MN 2.5HP

Postby tritonmal on Sat Nov 17, 2012 4:18 pm

HELP!

dont know where to stick this one , but here seams ok....
had EGR blank and oil catch can done on nm 2010 triton diesel.... so far so good.... :D

but
on a long ish run sitting on 100kph in top gear pulling 2000 rpm im starting to get engine surging :| .... sounds like the engine is trying to accelerate about 200 rpm but the computer/system/whatever it is thingy is doing its job ad catching it and maintaining 2000 rpm.... i get the feeling its trying to run away rpm wise and self detonate. :shock: ... ideas???
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Cowboy Dave on Sat Nov 17, 2012 6:42 pm

Not all Tritons will run with a blank in without throwing codes and stuff. If you don't have a chip it, or haven't done other mods to get around the problem, having the blank in could cause you strange engine behaviour.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby hvac guy on Sat Nov 17, 2012 7:59 pm

Pull the blank out and see if the surging is still there.
U might have an underlying problem, eg scv or maf dirty.
Have a search on mn surging there is heaps of info.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby tritonmal on Mon Nov 19, 2012 8:14 pm

Pulled blank out of EGR. No surging. Dealer reckons it was a valve thingy to do with fuel delivery when ya stick the boot in. Fixed under warranty. blank can stay out for the moment tho. I was getting shocking fuel economy. Like about 250 km to half tank with blank in. Was getting 450 km of half tank. .....
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Cowboy Dave on Mon Nov 19, 2012 8:18 pm

Sounds like the suction control valve. That can stuff your economy too as I understand it.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby tritonmal on Mon Nov 19, 2012 8:23 pm

Yeah that's it. Getting old. Stealership did new fuel filter too. Now need to blank up again the EGR and sees what happens.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby tritonmal on Mon Nov 19, 2012 8:39 pm

My probs maybe also related to tony's first post here in this topic especially the first 3 paragraphs of his post.....
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Re: Fixing the overboost issues with the MN 2.5HP

Postby jamesb_bau on Wed Nov 21, 2012 7:52 pm

Any idea were to purchase a 'dawes valve' in sydney ??

Rob
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Re: Fixing the overboost issues with the MN 2.5HP

Postby srb on Wed Nov 21, 2012 8:09 pm

Chipit sell them but there're set up for the nissan's. Tony may chime in and explain better. ;)
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Tony on Wed Nov 21, 2012 8:46 pm

Be best get it from me as I have to set them up correctly for the triton.
The mass produced item will only max around 16psi as primarily designed for the nissan ZD30 and is very good at what its designed to do with idiot proof safety in mind, srew the thing down to the max and it cant oveboost and blow the engine as ZD30's can if overboosted or if run with an EGR blank with out this mod done stand alone with the boost solenoid removed. Any of you know ZD30 drivers running EGR blanks, share the knowledge before its too late. :lol:

I have asked chipit to send a few over for me to set up as a kit but not come though as yet, I can (Already have) build a few one off's here in house (I call it the "T" valve) that will do the job in the mean time if absolutely needed, but I'm not going into production nor competition with the mainstream item, so when it appears, that will be it.
I'll shout out when the chipit items finally appear and are developed as a proper kit. My aim is to get between 18 and 30psi adjustment and set them at around 25psi depending on the tune.

I'm also working on a new design never seen before with an adjustable vacuum bleed integrated for those that wish to run it stand alone as a simple plumb in with no extras needed. Be a long while off as too busy at late. ;) I may even drop the concept as there is other alternatives such as a precision needle valve.

For those who feel they really need a dawes type valve soon, please PM tony on the chipit log on so we keep things together and legit.
SRB, I hope to have something for you very soon as you have a genuine need. ;) (I'll take it to PM)
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Re: Fixing the overboost issues with the MN 2.5HP

Postby tritonmal on Wed Nov 21, 2012 9:13 pm

I'm thinking of the Dawes valve arrangement for my nm 2010 diesel triton 2.5 hp.... Apparently they run 19 psi or so.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby srb on Wed Nov 21, 2012 9:36 pm

Thanks Tony. ;)
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Re: Fixing the overboost issues with the MN 2.5HP

Postby jamesb_bau on Fri Nov 23, 2012 7:25 pm

Thanks Tony and Srb...

I'll contact you Tony and go down the dawes valve avenue..
Currently running blank/ one-way valve 'T' in MAP line & boost guage...

Rob
Last edited by jamesb_bau on Wed Dec 12, 2012 7:53 pm, edited 1 time in total.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby alan_blue on Tue Dec 11, 2012 8:11 pm

interesting post thanks tony, guess it all adds flavour to the thought of is t really worth blanking the egr for these associated problems? I currently just have a catch can and am in 65 minds whether to do a blank or not lol
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Re: Fixing the overboost issues with the MN 2.5HP

Postby Tony on Tue Dec 11, 2012 8:30 pm

The blank will not always cause issues, its usually a combination of things.

The dawes type valve application as shown above just prevents turbo overshoot.
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Re: Fixing the overboost issues with the MN 2.5HP

Postby alan_blue on Wed Dec 12, 2012 7:52 am

im assuming you only need a dawes if you have an egr blank then?
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