Myths and fairy tails about the VM TD

[drgn1708erin]

deezelweazel, thanks for the info on th thermo, thanks for the start of this thread.I weekly look over the xj, looking for anything that looks out of place. I actually like doing that, tht way I get total mission reliability.
Im thinking of fitting the tj 6 speed in to the xj. what do u think?
Also why do the engines get oil in the intercoolers?

[Deezelweazel]

a 6 spped tranny:
You won't gain any benefits from that
- no better mpg
- no higher top speed

engine max efficiency is calculated at 93Km/h-95km/h, any higher speed will consume to much fuel with the 3.73 gearing.( stock tires, max 235/75R15)

Oil in the inintercooler
This happens (and is normal!) when boost pressure isn't high enough to seal the compressor wheel against the turbo housing. A small amount of oil will find its way into the intercooler.
Another possible way is the crankcase ventilation. You shouln't be worry about this if it is less than some drops and as long as you will not recognize an oil level loss.
To much oil in the PCV is an alarm signal!! Either your turbo oil drain is plugged or restricted or blow-by is too high. Time to check the air filter too!
A lot of blow-by indicates worn pistons rings and neglected oilchanges in the past as already mentioned in the begining.

This crankcase ventilation oil is used as an example in early VW Turbo Diesel engines to lube the intake valve( a diesel has no intake valve lubrication otherwise)
not a bad idea at all. It becomes worse in combination with the EGR! Oil and soot builds up a sticky goey glue in the intake.
Just have a look at this intake ellbow:



Soot and oil as a combination are terrible there is a layer 3-5mm thick.
You can imagine what that does to your engine performance. The engine starves for air. Air starving does mean high EGT's. High EGT's aren't good for your head at all.
What can you do to avoid oil in the intake?
Avoid extended idle or city stop-n-go.
Or install an oil trap can into the PCV tubing. You won't be able to supress oil leaking from the turbo- it won't matter at all, if it gets into the chamber it will be burned safely.
I do worry about EGR soot. An EGR delete is the thing to do.
Don't worry about higher combustion temperatures. EGR is only active during partial load.
It dillutes the intake air with 7% exhaust gasses. This will take out( yes, you read correct!!) combustion heat of the combustion process and reducing emissons.

Closing EGR is not allowed due to environment protection...think of that what you want to think about it.
We have a strict emisson control called safety inspection and the emissons reader does not get the delete.
Don't worry about a engine failure light. It has no connection to the delete it if you do it without interfere electronics.

What are the benefits of EGR delete?
Some claim less fuel consumption, I didn't...
Some claim a better part throttle response. I didn't...
Some claim more power. I didn't...

No soot in the intake. YES! That's enough for me...
@dgrn1708erin:
I hope that answers your question, if you have further questions feel free to ask.
You can't get 100% reliabilty by a visual check. You need more like extra gauges, and checks like yearly compression and injector ( spray pattern, pressure build up, release pressure)
If you want more to know about that, take the time and begin to start to read the FSM manual for your model year. There are a lot of service procedures and tests in it to keep you busy.

[The Smiths]

What are your thoughts on water injection?

Where it is introduced as a mist into the air intake. Some claim an increase in economy and performance - plus cleaning effects (used quite extensively with vegetable oil on other engines - normaly direct injection where they can suffer from ring gumming with veg oi, but the water clears it)

With the soot/oil build up it is shocking how quick it builds up. I changed some exhaust gaskets and cleaned the intake, 2 weeks later (when head gasket was being changed as that had gone - as well as exhaust manifold gaskets) - it needed cleaning out again

and I would recommend cleaning the intercooler out - shocking what a difference it makes

[Deezelweazel]

I can tell you a bit:

It does work, but those tiny pumps are way overpriced. you need really good pressure- such as a pressure washer with about 1200psi or higher. I've seen such a build up, looks strange but works.
I will seek for some pictures( I still have them somwhere)
The more methanol you add, the more power you gain.

The difficulty is to reduce head temperature constantly. That can only be obtained with a different setup.

An increase in economy ? I doubt that, the unit istelf is way to expensive to get any savings back.

The use of Bio Diesel is strictly forbidden with an XJ.
I wouldn't risk the mixture of veggie.
An overhaul of a leaking pump is expensive. The VP 37 does not like it at all.
In the intercooler can't be any soot- only oil. A sharp ride cleans that out.
you are right- the difference can be noticed.

[The Smiths]

Originally Posted by Deezelweazel

I can tell you a bit:


The use of Bio Diesel is strictly forbidden with an XJ.
I wouldn't risk the mixture of veggie.
An overhaul of a leaking pump is expensive. The VP 37 does not like it at all.

I am surprised by this - as in the UK it is considered one of the best set ups to run veg oil on a single tank system - an IDI engine and the Bosch mechanical pump. It is rated the same as the old Merc engines and runs 90/100% veg in summer (about 80% winter).

I've done about 30K miles on veg - some freinds have done about 70K (in the UK you are allowed to use 2500L of veg without paying fuel duty - and there is no VAT as it is food)

The savings can be huge. Diesel has just been around £1.20/L, I've just stocked up on 480L of oil at £0.42/L (offer at a supermarket - buy one get one free).

[Deezelweazel]

It's all about the pump.
Resealing an injection pump is no fun at all. Loss of lubrication leads to burned, worn surfaces.You won't be able to reseal them.

Dirt accumulation inside the pump is a serious problem. I do not talk about dirt- that is trapped in the filter. I mean the fat inside the oil which starts to accumulate inside the pump.

The difficulty is the electronics in the IP, replacement for a mechanical pump is a lot cheaper.
I will not risk it.
If I can't afford the Diesel, I have the wrong vehicle.

[The Smiths]

I'm talking about using new veg oil - not used that will contain fats which may drop out as temperature drops.

Its clean (human consumption) and is lubricating


I can afford the diesel - but prefer to pay less tax - I pay enough as it is


I do understand that you will not want to go down this route - but many do run on it - some for the enviromental feel good - or like me - just to pay less tax


I can't be accused of being an enviromentalist - the wifes car only does around 25mpg on petrol