The Mitsubishi Pajero Owners Club®

Chris Skocc · Posted: Wed Jan 13, 2021 19:45 Post subject: Over boosting pajero 2.8td

Hi Guys I’m a new member to this forum. I have a Mk2 Pajero 2.8td 1994 fitted with a 4m40 engine

Recently I have replaced my Td04 turbo with a Tf035 since I was experiencing loss of power due to turbo failure. I’ve installed the brand new turbo and now I believe that i have an over-boost issue. A couple of seconds after I accelerate a loud hushing sound can be heard and a great loss of power can be felt, I believe its relief valve, I was advised to seal the relief valve but I believe that can damage my cylinder head. Do you guys have any idea what I should do ?
Ps: I didn’t touch the waste gate setting, since I left it how it came from the factory. I think a factory setting is ideal.

It’s also a great pain to set the waste gate setting as I’ll have to remove the whole turbo for that. Or do you have other methods which this can be done ?

NB ive also cleaned my EGR valve and increased a little my boost compensation but minor effects were felt.

Google · Sponsor

chrishigh80 · Posted: Thu Feb 11, 2021 16:24 Post subject: Re: Over boosting pajero 2.8td

[quote="Chris Skocc"]Hi Guys I’m a new member to this forum. I have a Mk2 Pajero 2.8td 1994 fitted with a 4m40 engine

Recently I have replaced my Td04 turbo with a Tf035 since I was experiencing loss of power due to turbo failure. I’ve installed the brand new turbo and now I believe that i have an over-boost issue. A couple of seconds after I accelerate a loud hushing sound can be heard and a great loss of power can be felt, I believe its relief valve, I was advised to seal the relief valve but I believe that can damage my cylinder head. Do you guys have any idea what I should do ?
Ps: I didn’t touch the waste gate setting, since I left it how it came from the factory. I think a factory setting is ideal.

It’s also a great pain to set the waste gate setting as I’ll have to remove the whole turbo for that. Or do you have other methods which this can be done ?

NB ive Ialso cleaned my EGR valve and increased a little my boost compensation but minor effects were felt.[/quote

i have the exact same problem,same vehicle also after having the turbo replaced, it had done this if i hit the gas hard , at a loss how to resolve it,,

chrishigh80 · Posted: Thu Feb 11, 2021 16:25 Post subject: Re: Over boosting pajero 2.8td

[quote="chrishigh80"][quote="Chris Skocc"]Hi Guys I’m a new member to this forum. I have a Mk2 Pajero 2.8td 1994 fitted with a 4m40 engine

Recently I have replaced my Td04 turbo with a Tf035 since I was experiencing loss of power due to turbo failure. I’ve installed the brand new turbo and now I believe that i have an over-boost issue. A couple of seconds after I accelerate a loud hushing sound can be heard and a great loss of power can be felt, I believe its relief valve, I was advised to seal the relief valve but I believe that can damage my cylinder head. Do you guys have any idea what I should do ?
Ps: I didn’t touch the waste gate setting, since I left it how it came from the factory. I think a factory setting is ideal.

It’s also a great pain to set the waste gate setting as I’ll have to remove the whole turbo for that. Or do you have other methods which this can be done ?

NB ive Ialso cleaned my EGR valve and increased a little my boost compensation but minor effects were felt.[/quote

chrishigh80 · Posted: Thu Feb 11, 2021 16:25 Post subject: hissing on load

i have the exact same problem,same vehicle also after having the turbo replaced, it had done this if i hit the gas hard , at a loss how to resolve it,,

chrishigh80 · Posted: Thu Feb 11, 2021 16:55 Post subject: Re: Over boosting pajero 2.8td

i have the exact same problem,same vehicle also after having the turbo replaced, it had done this if i hit the gas hard , at a loss how to resolve it,,[/quote]

Mark3 · Posted: Fri Feb 12, 2021 10:22 Post subject:

In both instances its highly likely your new turbo is producing more boost than the old stock turbo which is why the overboost valve is letting off excess boost pressure.

You can alter the spring rate in the overboost valve or just remove it and blank it off completely BUT first you really need to know what your dealing with in the way of boost pressure when doing this.

I think the overboost valve lets off at around 15psi so its safe to say you both have more than this, i ran my Paj at 20psi and had no issues for the 2 years i had it for before selling it on so that was a safe number for me and it maybe for you IF the rest of the engine is good, clean coolant in a well maintained cooling system and regular oil changes on a nice sounding engine, if the engine is a bit "old" or "tappy" then upping its power output is a sure way of ending its life a lot quicker.

If it was me i would fit a boost gauge then remove and block off the over boost valve temporarily (there are details of what size plug and thread type on here somewhere) then go for a drive you so see just how much boost you are producing, if more than 20psi then alter the waste gate actuator linkage to reduce it and if you want extra protection of the over boost valve you can alter the spring rate so it chirps at around the same max boost and refit it.

chrishigh80 · Posted: Fri Feb 12, 2021 10:40 Post subject:

Thanks for that Mark, explains it now,
it was replaced around 15.000 mils back along withe the engine i had rebuilt . just never got round to addressing the issue,just kept my foot off the floor whilst out and about. will get round to having a play with it once the weather picks up.along with a phew other bits that need sorting out on it that ive put off. for now it is hardly used with isolating .
great help
cheers pal,,

ryan1000 · Posted: Tue May 04, 2021 0:12 Post subject:

I've got the same issue, got my turbo from ebay, maxspeedingrods oil only fed, it was great for the first week or so then started setting off the pressure relief valve on the inlet manifold, I temporarily plumbed in a boost gauge and I'm boosting at 15-16 psi, maybe more but can't tell due to valve opening, so I'm planning on removing the turbo then when off, ill extend the rod to hopefully lower the boost, I've read the best way to do this is by using a pump like a bike pump and a boost gauge and I'm hoping to get it down to 12/13 psi, sounds good if it works but I'm not happy with leaving it as it is as I've just put a brand new head on

emax · Posted: Tue May 04, 2021 19:24 Post subject:

Mark3 did a how to adjust the blow off valve, the pics are missing but you can probably figure it out from his description

http://www.pocuk.com/forums/viewtopic.php?t=134895

ryan1000 · Posted: Wed May 05, 2021 1:30 Post subject:

All sorted, had to take the turbo back off to access the rod adjustment, once off the vehicle i rigged up the turbo to my boost valve and an electric pump and found that the wastegate wasn't opening till around 15/16 psi, backed the rod off 1.5 turns, couldn't do any more as I would have had no pre load, but the wastegate was opening around 12 psi, now its running sweat with plenty of pull and no relief valve blowing off