3.2 Di-D Fuel economy saving at last. A/T Line Pressure Mod

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4ePikanini
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3.2 Di-D Fuel economy saving at last. A/T Line Pressure Mod

Thu Jul 26, 2012 8:57 am

I don't want to jump the gun but I think I finally found something on my pajero to alter in order to save on fuel economy.

I have tried the following methods with no success in saving fuel.

Full length bash plate for improved airflow
Cleaned out intercooler
Blocked EGR
Wastegate spacers to add a bit of boost
Advanced the diesel pump
Full fluid change of autobox, transfer and diffs
Checked rotating parts for binding
Swirly thing in intake removed
Pumped tyres a bit harder
Drive slower
Drive faster
Torque converter LockUp kit (helped a tiny bit)
Cleaned intake manifold
Free flow exhast
Catalytic converter delete

But a few weeks ago I upped the automatic gearbox's line pressure by about 14psi. (2.75 turns Anti Clockwise)

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I have now done 426km and the needle sits here.
Image

These miles include a morning's dune work and some light off roading valuating a farm. It usually was at 300km when halfway doing mostly highway work.
Image

I believe the reason for this is that the clutches are pretty old (nearly 300'000km) and may have some excessive slippage that wastes energy and creates heat and wears the clutches even further. The pump may also not put out the pressure required due to age and the previous owner neglected the auto fluid which was brownish. Upping the line pressure makes the clutches engage firmly again. I have noticed since upping the line pressure that the gearchanges are more pronounced when accelerating hard but none of the smoothness has been lost. The factory torque converter lockup occurs easier now as well - I presume due to more power reaching the wheels and not being lost in slippage in the box.

I realise that my box may have seen better days but with 2 flushes in the last year and the line pressure upped a bit now I should get good life out of it. Some tow with it for thousands of miles without issues so I guess it's a tough box. The last time I dropped the sump the magnets in the sump were pretty clean so I'm not too stressed.

I'll try to give more feedback here as time moves on or just note today's date and check my fuelly in a few months time.
Last edited by 4ePikanini on Thu Jul 26, 2012 10:07 am, edited 1 time in total.
Marius Fourie
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 9:52 am

How is on pulling away? When you suit at a robot and you put your foot on the accelerator?

Did you notice a difference?

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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 9:53 am

How do you increase the pressure?
Gerhard Fourie
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4ePikanini
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 10:06 am

Nismo wrote:How is on pulling away? When you suit at a robot and you put your foot on the accelerator?

Did you notice a difference?



The creep is slightly more or it could be my imagination. Pull away is a bit stronger and Full throttle gear changes are slightly firmer. Normal driving feels the same and the smoothness under medium to light throttle hasn't changed at all.

4ePajero wrote:How do you increase the pressure?


The main line pressure is mechanically controlled by a spring. This spring pressure can be adjusted (spring compressed or relaxed) by turning a bolt on the side of the valve body. The A/T sump has to be dropped for access.

Turning it anticlockwise increases the line pressure by approximately 5.1psi per turn. Doing some research most said that turning it for increased pressure all the way won't hurt but I went conservative and only did 2 and 3/4 turns giving me just over 14 psi increase. If I went 14 psi over recommended pressure I would only be over by 10% or so, so I'm sure I'm in safe limits.

Then the rest of the clutch packs are controlled by their own solenoids sending pressure and using the PWM system to smoothen/harden gear changes.
Marius Fourie
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 10:42 am

Jis, I wish you were closer, I had few people that said it feels that mine its sluggish on pull away.

Wonder who can do it for me.

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4ePikanini
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 10:54 am

I'd recommend printing out this page and giving it to your local gearbox specialist. They can test the line pressure and the adjust appropriately - I don't have the tools to measure so just guessed - not really recommended but worked for me as I went conservatively.

The steps are as follows.

Support gearbox with jack stands
Remove gearbox crossmember (4x 14 bolts on the side plus 2x 14mm gearbox mount nuts and 2x 14mm gearbox mount bolts)
Drain and catch gearbox fluid (17mm bolt) - it might be a good idea to buy some new fluid and replace the drained fluid with new fluid - easy to measure and just fill up.
Remove gearbox sump (plenty 10mm bolts)
Look at front left of the valvebody for a 8mm bolt
Turn anti clockwise to increase pressure (1 turn = 5.1 psi increase)
Clean magnets in sump
Clean sump and gearbox mating surfaces thoroughly and use solvent to degrease
re-assemble with gasket maker. Tighten very very very lightly, wait 15 min. Hand tighten. wait 15 min. Tighten to spec. I used this procedure and have no leaks.

NB : sump bolts go into aluminium so tightening torque is 11NM. DO NOT overtighten as they can strip VERY easily!
Marius Fourie
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 2:52 pm

Phoned a few places and they think I'm crazy, according to them this won't make change in fuel consumption and some dont even know what I'm talking about.

Is there Anybody on the forum from Pretoria that can maybe help me..?

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4ePikanini
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 3:00 pm

Nismo wrote:Phoned a few places and they think I'm crazy, according to them this won't make change in fuel consumption and some dont even know what I'm talking about.

Is there Anybody on the forum from Pretoria that can maybe help me..?

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Before you go and spend money, let me rack up some miles and confirm first. Also : what works for me might not work for you.

But if you are hell bent on ;) trying it your dealer will should be more than willing to perform a pressure test at least in exchange for some funds. :twisted:

I'm driving up to JHB Mid-end September so will be able to give feedback on long distance fuel consumption.
Marius Fourie
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 4:01 pm

I'm hell bent to get my consumption right.

My wife filled up on Friday and got 6.5km/l. And thats just town driving. I really didnt budget for these consumption.

I bassically tried eveything you tried except the pump advance.

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2009 Pajero 3.2 LWB GLX
OME Suspension
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4ePikanini
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Re: 3.2 Di-D Fuel economy saving at last. A/T Line Pressure

Thu Jul 26, 2012 4:11 pm

I'm hoping this helps me a bit. I have been browsing around for Touareg R5s. :twisted:
Marius Fourie
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