manual boost control on 1997 DSE auto

Bix said:

But in conditions like that you're not going to be changing gears, so if you can lock in 4th with no slip, you'll use just as much if not less fuel. You're not making more power, you're only simulating more throttle.

A better fuel saving device would be buttons to lock the box into a specific gear. At times round here I find it is too eager to drop into 2nd, could do with the ability to lock into 3rd. That'd save more fuel than any powerbox.

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Think that's what i said. Lots of people say you don't get the same drop down gear changes with a Powerbox. As the engine ECU signals the box to change down, think there maybe something in the Powerbox that damps that signal holding the gear under load.

wammers said:

Think that's what i said. Lots of people say you don't get the same drop down gear changes with a Powerbox. As the engine ECU signals the box to change down, think there maybe something in the Powerbox that damps that signal holding the gear under load.

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What I meant was if you're doing a steady 50mph, on a flat open road with no traffic, then you won't need a powerbox to use little to no fuel. A normal vehicle should do that quite happily.

I've not toyed with a Powerbox to know how they run, but if they can hold gear it'd be nice to have one that just holds gear, rather than dicking with fuel too. But selectable. So some conditions have it turned on to hold gear but able to turn it off normally.

Bix said:

What I meant was if you're doing a steady 50mph, on a flat open road with no traffic, then you won't need a powerbox to use little to no fuel. A normal vehicle should do that quite happily.

I've not toyed with a Powerbox to know how they run, but if they can hold gear it'd be nice to have one that just holds gear, rather than dicking with fuel too. But selectable. So some conditions have it turned on to hold gear but able to turn it off normally.

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Yes exactly, but as the Powerbox mapping maybe a little tighter than the BMW mapping you may get a slight improvement over unchipped in that situation. But it won't be as remarkable as some would have us believe. Mine has chip in the ECU and flies if you want it to. But drinks fuel around town IF you use the power. On a motorway i can get 26-28 MPG at 60-70 MPH. Best MPG i get is if i use cruise as much as possible.

Datatek said:

Any torque boost will eat the gearbox

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is the torque of the diesel more than the v8's

I guess a manual box would be ok right?

I have owned my diesel p38 for about 10 years now and I first chipped it about 8 years ago. I will tell you it transformed the car.

I think we need to make the distinction between a Powerbox add on, which to me is just a bodge, and a full remap which alters the fuel maps in the ECU.

The Bosch MSA11 ECU actually contains 16 separate maps that control the fuelling and other things. As well as maps for the injection quantity and duration there are maps for torque limiter and smoke limiter to name a few. It is an old ECU and does not control the boost directly like more modern ECUs. Boost control on the M51 engine is just mechanical. The boost pressure is however one of the inputs to the chip from the MAP sensor. Re writing the chip involves mainly altering the fuel quantity and also duration/ angular timing but it also involves altering the various map limiters by raising the limits. There is considerably more power to be had out of the engine.

Without the chip my car was awful to drive. Totally gutless. When towing a heavy caravan it was up and down the box all the time. Climbing an incline it used to drop down from 4th straight into 2nd then back up again. I fitted a genuine Superchip which gave about 160bhp, up by 25% but more importantly about 33% more torque. I will tell you it transformed the car. Much nicer to drive, mpg also improved by about 2 mpg to about 26mpg overall. Why you may ask? since it injects more fuel. I can only say it must be because it pulls better and is not up and down the box as much.

I have more recently fitted a JFearne chip and a larger Allisport intercooler and again both of these mods gave another significant boost. I think it is now putting out 180-190bhp. The JFearne chip has more aggressive maps I think, particularly what is called "driver wish" vs fuel quantity at small throttle openings. It takes off when I touch the throttle. The larger intercooler also gave a boost. I think because of the increased charge density.

I have plans to up the boost to 1.3 bars. It should be nudging 200bhp then. Any more will involve changing the turbo. The M57 turbo - a Garrett gt2256v has the same exhaust 3 bolt flange size.

If you are thinking of doing it I would say definitely chip it.

ccrdave wrote:

is the torque of the diesel more than the v8's

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The torque is more than the 4.0L particularly at low revs.
It really needs the 4.6L auto ZF 4HP24 gearbox fitting. I can tell you howto do it.
I wouldn't fit a manual box.

Bix said:

What I meant was if you're doing a steady 50mph, on a flat open road with no traffic, then you won't need a powerbox to use little to no fuel. A normal vehicle should do that quite happily.

I've not toyed with a Powerbox to know how they run, but if they can hold gear it'd be nice to have one that just holds gear, rather than dicking with fuel too. But selectable. So some conditions have it turned on to hold gear but able to turn it off normally.

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Gear shifts at constant speed are controlled by throttle position and revs. With a power box the throttle is open less for a given speed which with the lower drop off in revs fools the auto ECU into not downshifting on an incline, that's where the fuel saving comes in.
The auto is more economical in some conditions held in third gear with the torque convertor locked rather than running in top with torque convertor unlocked. A 40 mph speed restricted incline up or down in a typical example, in third the torque convertor is locked at 40mph, going up this eliminates torque convertor losses, going down torque convertor locked holds the revs up and operates the over run fuel shut off, in top the revs drop to idle which requires fuel to maintain.
I make a lot of use of the gear lever

I agree, I would not include a remap in with a Powerbox. A Powerbox is a poor way to increase power as it just makes the car think it is colder than it really is. A remap is the correct way to increase power (if you do it properly with each new piece of hardware you should update the software to best make use of it). However, I wouldn't do it on the ZF4HP22. As that isn't going to end well. If you're spending the money to get a remap then spend a bit extra for the HP24.

Datatek said:

Gear shifts at constant speed are controlled by throttle position and revs. With a power box the throttle is open less for a given speed which with the lower drop off in revs fools the auto ECU into not downshifting on an incline, that's where the fuel saving comes in.
The auto is more economical in some conditions held in third gear with the torque convertor locked rather than running in top with torque convertor unlocked. A 40 mph speed restricted incline up or down in a typical example, in third the torque convertor is locked at 40mph, going up this eliminates torque convertor losses, going down torque convertor locked holds the revs up and operates the over run fuel shut off, in top the revs drop to idle which requires fuel to maintain.
I make a lot of use of the gear lever

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Ah, I had wondered how the PB locks it in gear. Makes sense.

I use the selector a lot too. There are many situations where I'd like to be able to lock into a specific gear though as it quite often I will have it in the gear I want when the computer goes "what are you doing? STHAP!" Like going down hill, one hill near work is quite steep but with a 30 limit. It'd be nice if when I put it in 2nd it doesn't clutch in, but it does and I end up hitting 40 before engine brake kicks in again. 1st is far too low for the hill and requires throttle input to keep above 20. Not to mention loud as hell.

dave4x4 said:

ccrdave wrote:


The torque is more than the 4.0L particularly at low revs.
It really needs the 4.6L auto ZF 4HP24 gearbox fitting. I can tell you howto do it.
I wouldn't fit a manual box.

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Hmm! the car I am interested in has a manual box fitted I assumed the manual boxes were r380's which take a good bit of torque, Is that not the case?

I have just learnt something new. The torque converter lockup can come on if the gearbox is locked in 3rd.

ccrdave said:

Hmm! the car I am interested in has a manual box fitted I assumed the manual boxes were r380's which take a good bit of torque, Is that not the case?

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Turbo lag is a nightmare with the manual. Until 2,500rpm or there abouts you have nothing but clutch torture. The autobox does a lot to mask the lack of low end power.

Bix said:

Turbo lag is a nightmare with the manual. Until 2,500rpm or there abouts you have nothing but clutch torture. The autobox does a lot to mask the lack of low end power.

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Yes I had heard that, thats why I want to fit A VNT turbo

I have never had a manual p38 though I once had a manual classic.
An auto box will put 10 years on your life. It is also a buyers market for p38's.

My 13 year old diesel had the original HP22 box fitted and I was running with it chipped for the last 8 years. It was really only the last 6 months it started playing up and I changed it for a HP24.

I wouldn't fit a larger turbo until all the other mods are completed. An oversized turbo will give even more lag.

dave4x4 said:

I have never had a manual p38 though I once had a manual classic.
An auto box will put 10 years on your life. It is a buyers market for p38's.
I ran my chipped diesel with a HP22 box for about 10 years. It was only the last 6 months it started playing up.
I wouldn't fit a larger turbo until all the other mods are completed. An oversized turbo will give even more lag.

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not a vnt one wont, the idea is to remove (almost) turbo lag not increase it
the one fitted to my 300 tdi disco comes on boost at about 1100rpm and stays on all the way up to 4000+ it makes a world of difference from the standard turbo.
as you probably know vnt turbos are designed to minimise turbo lag at all rpm

Yes, I have got a Garrett VNT turbo to go on - once I rebuild it.
With an unmodded diesel engine I would think it too big and would be slow spooling up.
Don't know.

Before then I am fitting an external boost controller which should eliminate wastegate creep. It should keep the wastegate completely closed until it reaches maximum boost.

I want to maximise torque at low revs.

Existing Mitsubishi turbo gives about 0.8 bars at 2000 rpm. It reaches 1.0 bars from 2500 rpm onwards but then drops off over 3000 rpm. Not very good, it won't hold boost. It is undersized for my engine.

dave4x4 said:

Yes, I have got a Garrett VNT turbo to go on - once I rebuild it.
With an unmodded diesel engine I would think it too big and would be slow spooling up.
Don't know.

Before then I am fitting an external boost controller which should eliminate wastegate creep. It should keep the wastegate completely closed until it reaches maximum boost.

I want to maximise torque at low revs.

Existing Mitsubishi turbo gives about 0.8 bars at 2000 rpm. It reaches 1.0 bars from 2500 rpm onwards but then drops off over 3000 rpm. Not very good, it won't hold boost. It is undersized for my engine.

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Yes sounds like it same as for the 300 tdi standard turbo raising the boost just takes it out of its design parameters and it becomes very inefficient

My understanding of increasing diesel engine performance, and I assume its more or less the same for all diesels, to get more power you need to put in more fuel and more air (boost) either one on its own wont do much. Most diesels have plenty of air so in practice increasing fueling will increase performance a bit but it will also increase egt so bigger intercoolers and more boost is needed to bring it back down.
on a 300tdi with a mechanical pump its easy, bigger intercooler, turn up the fueling will give good results and boost will come in at slightly lower revs make the engine more flexible.
Now I dont know the bmw unit in the p38's but im guessing the principle is the same except it has electronic fuel control so it needs remapping to increase fueling (not add-on resister boxes!) a bigger intercooler to get more cold air in and hopefully a vnt turbo to flatten out the boost curve.
I am capable of doing this but now I need to consider the gearbox to take the extra power and I was looking at manual p38s cos I assumed the box would be stronger and it would be easier to put a different power curve through rather than the autobox changing up and down when it shouldnt

Any way I am going to try and see what happen, I like a chalenge

The same principles apply to the p38 diesel. It is a good engine but very underpowered.

If you have the capability you can do a lot of this on the cheap.
I bought a chip on Ebay from a guy in eastern europe for £20. Writes his own chips. It runs very well !
If you are capable of opening up the ECU and unsoldering the old chip you can save a lot.

A s/h auto box out of a 4.6L can be had for £350 or less. Then find a 4 post lift and fit it yourself with a few mates to help. The HP24 is designed to handle up to 450Nm so should be OK with the diesel. Also fit an uprated torque converter.

Larger intercoolers for the p38 are expensive but with a bit of welding I am sure one for another car can be made to fit.

dave4x4 said:

The same principles apply to the p38 diesel. It is a good engine but very underpowered.

If you have the capability you can do a lot of this on the cheap.
I bought a chip on Ebay from a guy in eastern europe for £20. It runs very well !
If you are capable of opening up the ECU and unsoldering the old chip you can save a lot.

A s/h auto box out of a 4.6L can be had for £350 or less. Then find a 4 post lift and fit it yourself. The HP24 is designed to handle up to 450Nm so should be OK with the diesel. Also fit an uprated torque converter.

Larger intercoolers for the p38 are expensive but with a bit of welding I am sure one for another car can be made to fit.

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ok good info, does the 4.6 box have a different gearchange curve to the diesel?
I put a 300 tdi into a classic RR with the 3.9v8 box and the gearchange was a bit weird!

If I buy an auto I think I will just run it until the box goes bang and then fit the 4.6 one. do you know what the max torque the diesel box will take?

Bix said:

I agree, I would not include a remap in with a Powerbox. A Powerbox is a poor way to increase power as it just makes the car think it is colder than it really is. A remap is the correct way to increase power (if you do it properly with each new piece of hardware you should update the software to best make use of it). However, I wouldn't do it on the ZF4HP22. As that isn't going to end well. If you're spending the money to get a remap then spend a bit extra for the HP24.

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Rubbish, that's a hot start fix you are thinking of. The power box extends the injector timing to provide more fuel, it's also takes into account manifold pressure to prevent overfueling and excess smoke.

ccrdave said:

ok good info, does the 4.6 box have a different gearchange curve to the diesel?
I put a 300 tdi into a classic RR with the 3.9v8 box and the gearchange was a bit weird!

If I buy an auto I think I will just run it until the box goes bang and then fit the 4.6 one. do you know what the max torque the diesel box will take?

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The gearbox shift pattern is ECU dependent. You keep the diesel ECU with the HP24 so the shift pattern will be the same as the HP22. The 4.6 auto ECU is totally different.
Absolute torque limit of the HP22 is 300Nm, the HP24 is 450NM