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Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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callahanoffroad
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Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by callahanoffroad » Thu Jul 25, 2019 6:35 pm

Like the title says is it possible to go from Jetronic to Motronic?

This theoretical discussion is going to use my 1995 Volvo 850 with a 2.4L 20V Engine, engine code B5254F(S?) with a manual transmission.

I've been reading up on this idea for a few days but I haven't found anything that shows if anyone actually did it. The documentation on ECU's is so heavily focused on Turbos it can be overwhelming to sort through.

To me, it looks like the the NA motors are all roughly the same until the introduction of coil packs. All the electronic parts seem the same, sensors are the same, etc. Aside from the VVIS of course (which of course I have), and the changing of the timing belt system.

So far I've figured out that you of course need a Motronic ECU, and engine wiring harness. Possibly the wiring harness from the ignition key back. If I upgraded to 4.3/4 I'd lose VVIS, but I might be able to get it back by tracking down an old Yitsbox, or fabricating my own electronic actuator.

I'm looking for links, and opinions that anyone has. Then I'll be trying to track down the parts to make this work.

I know you're going to ask why. Here's the why, my old '96 wagon got better gas mileage and had an OBD2 port that I could run diagnostics off of. It'd be nice to have that back and the 6 extra MPG wouldn't hurt either. :lol:

Thanks in advance Brain Trust. :D


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

Ozark Lee
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Re: Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by Ozark Lee » Thu Jul 25, 2019 8:30 pm

With enough time and money anything is possible. The question becomes is it practical?

IMHO, not really. In the end it will wind up costing you more than the price of buying a Motronic car and there are little things that interface with the ECU other than the engine like the climate unit for sure and they are different between the two ECUs. There may be others things as well.

...Lee


'94 850 N/A 5 speed
'96 Platinum Edition Turbo
Previous:
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

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callahanoffroad
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Re: Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by callahanoffroad » Fri Jul 26, 2019 5:50 am

Ozark Lee wrote:
Thu Jul 25, 2019 8:30 pm
With enough time and money anything is possible. The question becomes is it practical?

IMHO, not really. In the end it will wind up costing you more than the price of buying a Motronic car and there are little things that interface with the ECU other than the engine like the climate unit for sure and they are different between the two ECUs. There may be others things as well.

...Lee
Okay, just purely from an academic stand point what are the differences?

I know the climate control is different between a 4.3 and 4.4 (mostly how the AC compressor works iirc).

Let's throw 4.4 out the window. What are the differences between 3.2 and 4.3 setups?

Also I have Manual Climate Control. Not sure if that'd make a difference.

Maybe the solution is to wire the motronic unit like a piggyback/standalone ecu and have it only run the engine systems.

Again purely academic.


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

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misha
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Re: Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by misha » Fri Jul 26, 2019 3:27 pm

M 4.3 & M 4.4 are pretty much the same system management with minor differencies...Jetronic 3.2 is TOTALLY different management and NOT compatible with Motronic.
Sensors are totally different...from Maf to o2...wiring harness,ecu box and slots...etc.


'97 850 2.5 20v /fully equipped/ Motronic 4.4 / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

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callahanoffroad
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callahanoffroad

Re: Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by callahanoffroad » Fri Jul 26, 2019 6:57 pm

misha wrote:
Fri Jul 26, 2019 3:27 pm
M 4.3 & M 4.4 are pretty much the same system management with minor differencies...Jetronic 3.2 is TOTALLY different management and NOT compatible with Motronic.
Sensors are totally different...from Maf to o2...wiring harness,ecu box and slots...etc.
Well if that's true then it would be too much effort. :lol:


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

Ozark Lee
MVS Moderator
Posts: 14796
Joined: Thu Sep 07, 2006 8:24 am
Year and Model: Many Volvos
Location: USA Midwest
Has thanked: 4 times
Been thanked: 47 times
United States of America
Ozark Lee

Re: Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by Ozark Lee » Sat Jul 27, 2019 10:17 am

It is true.

...Lee
These users thanked the author Ozark Lee for the post:
misha


'94 850 N/A 5 speed
'96 Platinum Edition Turbo
Previous:
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

User avatar
callahanoffroad
Posts: 299
Joined: Mon Jun 30, 2014 5:25 pm
Year and Model: 1995 850
Location: St. Louis Missouri
Has thanked: 16 times
Been thanked: 25 times
United States of America
callahanoffroad

Re: Conversion from Jetronic LH 3.2 to Motronic 4.3/4.4 Is it Possible?

Post by callahanoffroad » Sun Jul 28, 2019 5:27 am

Ozark Lee wrote:
Sat Jul 27, 2019 10:17 am
It is true.

...Lee
I wasn't saying I didn't believe you guys, it was a figure of speech. :-)

Also I double checked the part #'s are you guys are totally correct. Crazy.


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

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