nissan patrol gq turbo

Maybe I've just been brain-washed over the past 15 years, but I firmly believe that this is one area that can quite rightly be described as a "black art". Getting the air/fuel mix right, injectors set properly etc is, to me, something that needs to be left to the experts.
The use of EGT could be one way of telling if you've got it wrong (eg: if you start to see extremely high temps you could deduce that the air fuel mix is too rich), but by and large it'd be too hit & miss to be of any value.
Just my opinion, YMMV (:--))
Roachie

Just fitted a MTQ kit to my 94 Coil Cab, back a few months ago. I fitted the kit myself, including a pyrometer. On advice from the MTQ technician, I bought the vehicle back to them for fuel pump adjustment. They adjust the pump to suit the appropriate Air Fuel Ratio setting recommended. Some fitters use a dyno to adjust the pump. For peace for mind, and $100 extra in my case, take your vehicle to the experts.

Regards
Dicko1980

The screw is on the back of the pump with a lock nut on it, screwing it in is rich out is lean,warning1/8 of a turn in is all you should need anymore than a 1/4 is usually to much.

after 12 mths of overheating, running like bleep etc, get the pump setup properly. dont waste your money or time.

>>> The way I see it if I monitor my temperatures I should be able to adjust the fuel pump myself
Yes.. 4 diesel places tried that with mine, did nothing.

Andy,
When you add a turbo to an engine (diesel or petrol) you are adding a compressor, you are pumping more air (oxigen) into it, air by itself does nothing, they need to adjust the fuel accordinly, however (here is the catch)...
To do it properly the pump needs to be modified with the installation of an aneroid, without that they can get half way there but nowhere near the optimum.
An aneroid is a diafragm with a tappered end which, as the turbo boosts, pushes the plunger down and adjusts the fuel on the fly (the turbo provides more oxigen, the pump increases the fuel accordingly), and it decreases fuel metering when not on boost.
Diesel is not a black art, far from it, very simple as long as you know what you are doing.
Adjusting the pump, aneroid etc without measuring EGT is not accurate because the internal combustion temperatures cannot be measured.
Because they operate on excess air diesels can be overfueled but the internal loads and temperatures can be exceeded beyond what the manufacturer intended.

Andy,
I was discussing this sort of thing with a Marine Engineer mate of mine just recently, the whole concept of over and under-fuelling diesel engines.
You should see the engines Pete works on, turbo's 2 metres in diameter, cylinders you can stand up in.
His take was over and under fuelling a diesel can both cause overheating. Under fuelling is exactly the same concept as a petrol.
Overfuelling from what he said causes incomplete combustion, carbon build up etc. Carbon causes hot spots on valves, pistons, combustion chambers etc.

His advice, by all means turbo your vehicle, his Landcruiser has an MTQ kit on it. But have the fuel system setup by someone who knows what they are doing.

Geoff.

Hi Andrew,

Wish I'd spotted your post earlier before so many 'diesel myths' had surfaced again.

With deference to Geoff's marine engineer mate, I'll try to dispel a common myth - it is impossible to run a diesel 'too lean'. They always run with air/fuel ratios on the 'lean' side of stoichiometric. At idle, the ratio is hugely 'lean' - just a tiny squirt of fuel is injected into a cylinder full of air. At full throttle, the ratio is closer to stoichiometric but will never actually get there without generating damagingly high exhaust gas temperatures (EGT). So it is actually 'rich' ratios (overfuelling)that cause trouble in diesels. [Geoff, if you can provide any documentation to support your claim that "Under fuelling is exactly the same concept as a petrol.", I'd be interested to read it.]

Please note, I've used the term 'ratio' rather than 'mixture' as diesels never actually have an air/fuel 'mixture' in the way petrol engines do. The only time a 'mixture' exists is in the instant between the beginning of injection and the beginning of combustion - an matter of milliseconds at most. Enough diesel theory - back to the subject at hand...

Non-factory-turboed engines have injection pumps without a manifold pressure compensator (otherwise know as a boost compensator or, somewhat erroneously, as an 'aneroid'). Putting a turbo onto a 'normally-asphyxiated' diesel with a non-compensated injection pump will always be a compromise. Without a manifold pressure compensator, the pump can never deliver the optimum quantity of fuel in both off/low-boost and full boost conditions. BUT, the results can still be quite acceptable and reliable, as long as the engine is not heavily over-fuelled at full load.

It is certainly possible to fit change the injection pump for one which has a manifold pressure compensator, but I doubt it's worth the expense on an aftermarket turbo installation with moderate (say, 6 to 10 psig) boost levels.

Contrary to popular opinion, manifold pressure compensators do not actually increase fuelling at high boost. Rather, they the restrict the fuelling when boost is less than maximum, by limiting the range of movement of the internal governor mechanism when manifold pressure is low.

On Andrew's NA diesel injection pump, the only external adjustment available is the maximum fuel delivery screw on the back of the pump. This will usually have either a lead-sealed wire or other anti-tamper device because, as mentioned by another correspondent, it is a sensitive adjustment and twiddling in ignorance can easily lead to a 'cooked' diesel. After fitting the turbo kit, this will need to be adjusted to increased the full load fuelling in line with the increased air charge. It is critical that this be done while monitoring EGT, either with a temporary gauge or after installing a permanent gauge kit.

In Andrew's situation (non-compensated pump with moderate boost) it is generally possible to find a maximum delivery adjustment setting which gives satisfactory performance without excessive EGT (or smoke) at full boost AND not too much smoke (overfuelling) during low boost acceleration.

If you are confident with your mechanical abilities, I'd recommend you fit an EGT gauge and monitor your engine under 'real world' conditions. [Yes, I do sell them but I really believe any non-standard turbo diesel should have one. If you don't like mine, get another brand - but do get one!]

If you find your maximum EGT is well within acceptable limits when under heavy load at full throttle (say, less than 650 C upstream/450 C downstream), you probably have some scope to increase the maximum delivery adjustment. Conversely, if your EGT is reaching high levels (700+ upstream/500+ downstream) within a short period at high load, your max. fuel delivery may already be a bit too high.

But also remember, pump delivery adjustment is only part of the story. The entire fuel system needs to be in good order to get reliable performance. General maintenance items like valve clearance adjustment needs to be correct. If the engine already has high kms (say, >200,000), it's probably advisable to have the pump and injectors checked and re-calibrated/reconditioned/replaced by a reputable specialist. Also the injection timing needs to be spot-on. This is another area where the accumulated experience of specialists like Denco comes in. Any competent 'home mechanic' should be able to check the timing to factory spec but experienced specialists will know whether non-standard timing is required on different engines after adding a turbo, different boost levels, with or without EGR, etc.

Hope this helps.