The ZF4HP22 box as fitted to the oil burners is barely able to handle the standard output....chip it and the box will eat itself in short order!
 
Get your car performing correctly first properly set up and running well. DO NOT use a chip to mask a sick motor.
 
The ZF4HP22 box as fitted to the oil burners is barely able to handle the standard output....chip it and the box will eat itself in short order!

It seems to handle the more powerful and higher torque 4.0 litre petrol engine without to many problems. If you fit a chip to one that has done a few miles has had the gearbox neglected or done a lot of towing to boot then you start towing with it odds on it will fail. But fitted to one with a good gearbox that has been looked after and you don't do a lot of towing there should be little problem. ;);)
 
You have to desolder the chip and put a new one in. They don't clip in/out unless someone has been in there already.
 
It seems to handle the more powerful and higher torque 4.0 litre petrol engine without to many problems. If you fit a chip to one that has done a few miles has had the gearbox neglected or done a lot of towing to boot then you start towing with it odds on it will fail. But fitted to one with a good gearbox that has been looked after and you don't do a lot of towing there should be little problem. ;);)

So a silly question for the diesel god... I was surprised that the diesel produced less torque than the 4.0, having had a look at the internet to see what the numbers were lead me to notice that the original M51D25 producedd 190lbft but the M51D25TU made 210lbft. Did the TU ever make it into the P38? And if so what was the update? A friend of mine is considering an oil burner and I told him that the engine was essentially unchanged through the life of the P38 (apart from addition of egr, is that a problem?) but it looks like I might have been telling fibs!
 
So a silly question for the diesel god... I was surprised that the diesel produced less torque than the 4.0, having had a look at the internet to see what the numbers were lead me to notice that the original M51D25 producedd 190lbft but the M51D25TU made 210lbft. Did the TU ever make it into the P38? And if so what was the update? A friend of mine is considering an oil burner and I told him that the engine was essentially unchanged through the life of the P38 (apart from addition of egr, is that a problem?) but it looks like I might have been telling fibs!

BMW made various versions of the M51 for their cars some were quite nippy. The version of the M51 fitted to the P38 is adapted for that use. After all you don't see many BMW cars that weigh 2.5 tons and pull 3.5 ton trailers. The main difference from what i can see being the ECU and a slightly larger capacity turbo on some of the car versions. Obviously the ECU on the P38 changed on the introduction of EGR with the addition of a MAF sensor to read differences in air flow so that the ECU knew how much EGR modulation was needed to control exhaust gas/air mixture and reduce NOX production. But the power output remained the same. With a good chip the P38 diesel can be given around 170 BHP and about the same torque as the 4.0 litre petrol. As the torque comes earlier on the diesel the 4.0 litre petrol even though it has 18 or so more BHP might struggle to get away from a chipped diesel is some cases. Fitting a chip to one that has not been looked after does cause problems with the gearbox in some instances.
 
I used to have a P38 diesel with the BMW version.
It ran just fine, but I got it chipped to help tow my big twin axle caravan.
It had more power, but began to overheat on long hills.
I concluded that the extra power gain came with the downside of more heat that the cooling system was unable to deal with.
The gearbox and transfer box had to be rebuilt during the period after fitting the chip and doing some long distance towing - there's no such thing as a coincidence!
Don't do it if you need to tow anything heavy.
 
My chipped one got hot going up long hills with my large caravan, changed viscous fan and not had a problem since.
 

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