ECU modification w/3.9L to 4.6L Conversion - Defender Source
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  #1  
Old March 18th, 2010, 03:05 PM
severson
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Lisa and Charles Severson
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Exclamation ECU modification w/3.9L to 4.6L Conversion

I have just replaced the 3.9L engine in my D90 with a 4.6L. The 3.9L fuel injection sytems was transfered over to the 4.6L engine. It starts and runs fine, but I have not driven it yet. Does any body know if I should change of re-chip the ECU that was originally with the 3.9L engine, or will the original unit work with the new 4.6L engine? Will any damage occur to the new engine if I use the old ECU.

Thanks
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  #2  
Old March 18th, 2010, 03:17 PM
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evilfij
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It will work, but I recommend getting an ECU (or just the chip) out of a 1993-1995 Range Rover LWB. Many folks have used 4.2 ECU with success with a 4.6. There are other more expensive options that might even give more performance.

PS welcome to D-90.com and please post pics of your truck
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  #3  
Old March 18th, 2010, 03:27 PM
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Robert Klima
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What ecu is installed on your truck? Lucas 14CUX? It should run at idle but you might get problems at higher revs and load as the ecu normally adjusts the injection rate according to the maps and ignores Lambda. I'm not 100% sure with the 3.9 but is the problem when you go from a 4.0 to a 4.6
The 4.6 as all Rover V8 (except the 3.5) are at risk getting cracks in the block when running on the lean side. Therefore I would either use an ecu for the 4.6 or go to a custom solution - e.g. MegaSquirt

Robert
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  #4  
Old March 18th, 2010, 03:44 PM
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Dennis Yard
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Charles,

I just completed my 3.9 to 4.6 conversion and have a couple of hundred miles on it so far.
I used a Mark Adams NAS 110 chip from RPI. Big $$.

Truck seems to run fine, once I replaced the plug wires which were bad, and gives 10 mpg to date.
Only noticable issue is that at cold start up it seems to idle quite high until warmed up.

This weekend it gets a longer trip to the desert, so I'll have a better gauge of performance on mountain roads out to the desert.

Biggest test will be when i go for CA smog testing next month.

Dennis Yard
San Diego, CA
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  #5  
Old March 18th, 2010, 04:57 PM
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Phillip
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those Mark Adams chips are crazy expensive.



Blocks crack from overheating and lack of attention to the cooling system.
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  #6  
Old March 18th, 2010, 06:46 PM
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Bill Adams
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ECU will be just fine.
The only difference is in the LUT burned into the PROM. Else wise, all same guts. If you had any idea how rudimentary the Rover EFI is, you'd toss it in the can. Bank fire, non adaptive, prone to losing one bank....

A high quality alternative is the Ford EFI as found in 89-93 mustangs. This is a leap forward in performance due to the fact that it is sequential and is also Mass Air. It will also tune itself as you drive. Your standard issue A9L Ford ECU can be had for mere tens of dollars. You need only splice the Rover wires into the Ford harness (which are unfortunately wrapped in sticky goo and electrical tape). The GM systems of the time were throttle body (TBI) and not as adaptable as the Ford. There are also tons of chip options for Fords. Later Ford ECUs are possible but they are OBD III and IV. The A9L is OBD II.

Another way to go is with Megasquirt. This is a home built ECU which you can program and tune yourself with a laptop. It's about 350 for a full kit with accessories needed for the Rover. There are several case studies and success stories about Rover conversion on the MS website.

I do not recommend throwing bad money at rePROMed Rover chips which will deliver only small to minimal gains in performance.
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  #7  
Old March 18th, 2010, 06:58 PM
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John B.
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There is a place in Australia that makes replacement ECUs that are fully programmable through a computer. I forget the name. They are around $1000 AUD. Seems like a much better way to go, if it were me.
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  #8  
Old March 18th, 2010, 07:32 PM
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Hey to you guys who did the 3.9 to 4.6 swaqp, did any of you have to switch to an adjustable fuel pressure regulator and did you have to adjust your base idle screw?
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  #9  
Old March 18th, 2010, 08:23 PM
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Chris Davis
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I did the 3.9 to 4.6 and it ran fine on the 3.9 ECU which I then upgraded with the 4.2 chip and again it ran fine. No issues with the fuel pressure regulator or base idle although I have tuned my base idle as a mater of course when assembling everything since it is so easy to do. Just because it runs fine does not mean it is optimized for the 4.6 and I "hear" that the Adams chip and Tornado are great but have no basis of comparison. You should not have any issues as far as I know, but certainly check things like your plugs to see how you are running.

Interesting thing about the FORD ECU's--can I retain my current MAF and sensors or does it look for "Ford" sensors yeilding different values? I doubt I will cut up my harness, but I certainly may make an adapter to go from one to the other--take the female plug from a spare ECU and the mail plug from the harness of the Ford and make a quick little adapter....

Bill--are you running the Ford ECU? Please expound! ;-)
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  #10  
Old March 18th, 2010, 08:40 PM
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jim pendleton
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I have chips I can sell for 150.00 that were setup for this type of engine conversion. Had them custom burned in UK by some kit car guys. This PROM would go into your ECU just like one of the 4.2 PROMS

JP
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  #11  
Old March 18th, 2010, 08:50 PM
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I'm interested Pendy, how many you got? I only need one right now.
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  #12  
Old March 18th, 2010, 09:07 PM
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jim pendleton
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I have four of them here now I can let go of. Have you changed a PROM before? Just need to make sure you do not install it backwards. These are a little different to look at from a stock one.

You can PM me and I will give you a Pay Pal email address. I will pick up shipping as long as US postal is okay.

JP
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  #13  
Old March 18th, 2010, 09:09 PM
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Bill Adams
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Naw, using reg'lr Rover on the Lawib. For the 109 project however, the engine will certainly be megasquirted. Or Forded, as I have harnesses and stuff for both systems. I have an extra Megasqirt from the boat that I ended up plopping a carb on (yes, lazy) but the MS wouldn't read the temp sensors. I guess I had the wrong kind....

Anyway the only major difference with the Ford is the use of an additional atmospheric pressure sensor that mounts on the bulkhead. Like 19 bucks at NAPA. You know they used to run the Ford Indy cars with the self same A9L ECU. Many many millions of bucks went into the development of that system.

I think the Ford sensors do indeed look for different voltages than the Rover. Easy enough to swap out the Ford ones and they are dirt cheap. The Ford MAF sensor sits in the intake hose just like Mr Rover's. Not saying it would be a weekend change over. Certainly there will be some differences. The only thing is the Ford ignition timing comes from the TFI sensor on the distributor. Not sure if the Rover IGN module has the proper IGN OUT signal for the Ford, but a solution can't be too troublesome.

I know TeriAnn used a Ford engine in her EFI powered Series 2A Dormobile. Maybe a Mercruiser Thunderbolt diz will be the ticket for the Rover.
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  #14  
Old March 19th, 2010, 11:15 AM
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Lisa and Charles Severson
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I am interested

Quote:
Originally Posted by pendy View Post
I have chips I can sell for 150.00 that were setup for this type of engine conversion. Had them custom burned in UK by some kit car guys. This PROM would go into your ECU just like one of the 4.2 PROMS

JP
I am interested in one of your chips, how can we work out you sending it to me?

Charles

------ Follow up post added March 19th, 2010 07:18 AM ------

I am interested in one of your chips. How can we arrange for you to send it?
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  #15  
Old March 19th, 2010, 03:56 PM
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jim pendleton
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I will PM you severson. Click on the private messages in your upper right hand corner if you have not used the feature before.

That is it. I do not have any more to spare. Unless Neil changes his mind. All four of my extras are spoken for.

If something changes short term I will report it here. As far as more in the future it usually takes me a few months to get them sent to me. So you can PM me to reserve one at no cost until it is ready to ship from me.

Jim Pendleton
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