to bring up an old subject again...have spent weekend taking whole intake apart for cleaning etc. Looking at buildup and design and having read up on here about bad turbo control by Ecu, would it be right in saying that, at least in part, our Trolls tendency to grenade could be due to no Egr cooling and no intercooler fan on this model. The Egr goes round the back of the engine in the hottest area without cooling, blasting cylinders 3 and 4. Have just fitted a fan to the intercooler, and is amazing how the fins restrict air through them....cant be much thru put from top intake with a badly fitting rubber. Have had 630 degc from pyro gauge and cdve gone higher ( 4000 in 5th) and as pyros fitted to egt blank on exhaust, is a good indication of real time Egt temps. CRD and later trolls get cooled EGT so pleased mine blocked itself. Intercooler shroud is a bit heath Robinson but gives a good thru put....( pic to follow)
Behr
Grenade issue is due to bad design of fuel system and shyte material used in piston manufacturing.
Pistons are the weakest link, have no tolerance to adding heat due to injectors dribbling too much fuel or not enough air getting in cause badly designed induction system. Top end is simply too weak and any deviation from perfect will start the rot.
EGR is consequential (read accelerating) to the issue and really irrelevant if cooled or otherwise.
Intercooler fan makes no difference to the grenade either.
Cheers
Pistons are the weakest link, have no tolerance to adding heat due to injectors dribbling too much fuel or not enough air getting in cause badly designed induction system. Top end is simply too weak and any deviation from perfect will start the rot.
EGR is consequential (read accelerating) to the issue and really irrelevant if cooled or otherwise.
Intercooler fan makes no difference to the grenade either.
Cheers
Rumcajs, I agree with you about the pistons, fuel system and weak top end, particularly cracking issues between the gowplug hole and injector hole.
But I do think there is merit in anything that can reducing high EGTs which are a symptom of high comustion tempeartures and the cause of piston and head failures. So anything you can do to keep EGTs dow and keep the system more efficient and cool wil help. Reducing the build up of gunk in the intake from EGR and oil vapor blow by, improve cooling and intercooler flow, improve intake air flow, more boost / higher air to fuel ratio, water injection will all help to reduce combustion temperatures and reduce risks of the poor pistons and head from giving in.
But I do think there is merit in anything that can reducing high EGTs which are a symptom of high comustion tempeartures and the cause of piston and head failures. So anything you can do to keep EGTs dow and keep the system more efficient and cool wil help. Reducing the build up of gunk in the intake from EGR and oil vapor blow by, improve cooling and intercooler flow, improve intake air flow, more boost / higher air to fuel ratio, water injection will all help to reduce combustion temperatures and reduce risks of the poor pistons and head from giving in.
All these years down the track and we are still talking about it, and we are the home of the Grenade. There is no end to the discussion 
.
Having been there done that and got a T shirt to prove it. I agree with both Geordie and Rumcajs in part.
It's EGT that kills a DI, but the dodgy piston material was the weak link that brought many undone. Overboost had nothing to do with it, underboost was a big issue brought about by the stupid ECU controlled vacuum solenoid, hence why mine went 7 years ago.
So we rebuild the engine with new better pistons and a new head and set about making it last, EGR doesn't really have anything to do with the grenade, but we do know that over time the throttle body and manifold can be restricted and badly effect performance.
If in 2000, when I bought mine new, and I had known about this issue, I would have:
1. Put in an EGT gauge (knowing is half the problem) and driven accordingly.
2. Bypassed the Vacuum solenoid with the Dawes and Needle (so I knew the boost would remain where I wanted it not where the ECU wanted it), overboost and spoolup rate don't cause grenading.
3. Put in a glow plug timer to protect the head.
And then just maintained the engine as per normal. I am quite confident that this would have been enough to see my engine not explode as it did. I'm not sad it did because I have learned so much about these engines due to that occurence.
All the other stuff we do is just to add more security that in reality is not needed to just keep the engine going, it just makes them go better and a little more forgiving.
.Having been there done that and got a T shirt to prove it. I agree with both Geordie and Rumcajs in part.
It's EGT that kills a DI, but the dodgy piston material was the weak link that brought many undone. Overboost had nothing to do with it, underboost was a big issue brought about by the stupid ECU controlled vacuum solenoid, hence why mine went 7 years ago.
So we rebuild the engine with new better pistons and a new head and set about making it last, EGR doesn't really have anything to do with the grenade, but we do know that over time the throttle body and manifold can be restricted and badly effect performance.
If in 2000, when I bought mine new, and I had known about this issue, I would have:
1. Put in an EGT gauge (knowing is half the problem) and driven accordingly.
2. Bypassed the Vacuum solenoid with the Dawes and Needle (so I knew the boost would remain where I wanted it not where the ECU wanted it), overboost and spoolup rate don't cause grenading.
3. Put in a glow plug timer to protect the head.
And then just maintained the engine as per normal. I am quite confident that this would have been enough to see my engine not explode as it did. I'm not sad it did because I have learned so much about these engines due to that occurence.
All the other stuff we do is just to add more security that in reality is not needed to just keep the engine going, it just makes them go better and a little more forgiving
.
uncooled egr is not really the issue. cooled egr is simply used to increase the amount of exhaust gas recirculated.
Why? Its not like air, its inertness is used to lower flame front temp, so the cooler it is, the better its work, so the hotter it is....leads to higher combustion temp in conjunction with other factors eg turbo...sure its not the be all and end, but do we all block purely to stop marmite? My charge air is 16 degc and pyro shows 620degc if im gunning it...know which one i want going in!
Actually Tweak'e is correct. EGR is used to lower peak combustion temperature by displacing amount of available oxygen for burn. Lower peak temps lower the NOx. The diesel has become too efficient for fuel use and too polluting because of that. We're now going backwards to cripple the efficiency to lower emissions.
The issue with grenade is that retarding boost to get EGR in causes the combustion to go rich under the given engine load hence skyrocketing EGTs. Really bad implementation of induction and fuel control combined with weak hardware finishes the rest. The grenade is the result.
What needle vale/Dawes combo does is removing that air induction control inefficiency but doesn' t fix the overfuelling of faulty injection process. So if injectors are worn/fuel more at incorrect spray pattern, apparently those dual stage units are known to dribble fuel when closed.
650°C EGTs would be too much for my likings.
Regards
The issue with grenade is that retarding boost to get EGR in causes the combustion to go rich under the given engine load hence skyrocketing EGTs. Really bad implementation of induction and fuel control combined with weak hardware finishes the rest. The grenade is the result.
What needle vale/Dawes combo does is removing that air induction control inefficiency but doesn' t fix the overfuelling of faulty injection process. So if injectors are worn/fuel more at incorrect spray pattern, apparently those dual stage units are known to dribble fuel when closed.
650°C EGTs would be too much for my likings.
Regards
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