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VR engine into VN, ECU?

vn3.8L

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So basically I have to put another new motor into my vn again.
I have picked up what was supposed to be a Vn S2 motor, but looking at it now it seems to be a VR motor.
I'm going to go ahead and put it in. Using the VN trans and I will swap the engine loom over from the vr to the vn loom, only differences is the cam angle sensor will not be plugged in.
So doing this I suspect that everything should work fine. However I know that a VR engine has a bit more compression than the VN S2's and I am now getting a little worried about the engine possibly running a little bit lean.

This is where I don't really know what I am doing. I was thinking the best way to overcome this would be to re write the ecu. (note, I have two Vn ecu's). I have done a little bit of research but I am a bit confused about the whole re writing process, everyone seems to buy different stuff, but I Just want to know the easiest way to go about fixing the problem. I have done a little bit of basic computer programming once before. Basically I'm not really concerned about extra horsepower, I just would like the engine to run correctly. It's almost like the time the injectors open need to be altered to that of what it would be for a VR tune.

Thanks
 

Jxfwsf

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It'll run fine on the VN ecu and memcal, it won't run lean/rich the ecu controls all that, the small compression ratio increase is not going cause an issue.

As you said no cam angle sensor isn't going to worry it as that is only used on a VR auto (that being said i have seen s2 VN & VP engine with it in the timing cover obviously not connected to anything, pop the oil filler cap off and have a look at the rocker gear, VR rockers have bearings on the pivot point and VN/VP don't).

If you really wanted to worry about changing the tune what you need is a VR manual tuned memcal with VATS disabled (this is a must or it won't start) and it'll run fine in the VN 808 ecu & will suit either manual or auto without a problem, the only problem with this is that a tech1 scantool will no longer work on it but you can still get fault codes with the paper clip method and count the cel flashes.
 

codwalop

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the vr engine has the same injectors as vn-s2 and vp.. and everything will line up and fit exactly as it was, except the thermostat housing. you can either leave the cam sensor unplugged, or fit your old timing cover if you can be bothered.

as Jxw mentioned, the rockers on the vr engine have a roller fulcrum (although not roller tipped), and the compression difference is so minimal it won't be an issue. you will find that the vr engine will rev higher and more freely.

the vn-vp 808 ecu has some cheap hardware mods that can be added to get better diagnostics, allow data logging and even program in realtime. the software & website that Circlotron mentioned will be all you need, the hardware mods are available through some of the guys on that site as well. the delco ecu is very flexible but there's alot to learn and you're not going to have any issues running the older ecu anyway, so it's upto you whether you can be bothered.
 
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vn3.8L

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Thanks guys for all the above information.
Sorry about the late replay but basically I only got the engine in a couple of days ago. At first the engine made some ugly sounds but it warmed up and went away and hasn't made the noise since. It's from the wreckers so i think it may have been sitting for a while, as it sounded like dud lifters, but soon went away.
Im having a bit of a problem though. Its very smooth and revs nice but every now and then when at idle it seems to stumble a bit, like its gonna stall. Also when the thermo fan turns OFF, it get's super close to stalling. And when going from drive to park or drive to neutral it does the same thing, and on one occasion actually did stall. Does anyone have and idea what this might be. As it warms up the problem becomes more so apparent, the idle in general seems a lot lower than that of my old engine but this could just be me. I have a few idea's but it's a funny problem as it only seems to stall when the engines going from a load to no load.
Thanks again
 

Cheap6

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TB clean?

You can also try swapping the IAC valve from the old motor.

That's assuming that it is still a problem. The ECM has to relearn the idle valve position after the battery has been disconnected.

If none of that fixes it or it doesn't go away then you can try resetting the base idle speed. Break the plastic cover off the throttle stop screw and mark the current position of the screw (so you can get back to where you started from if it all goes wrong).

With the engine at operating temp. and all accessories off (including the cooling fan - you may have to wait for it to cycle off) and the intake air duct removed, block the inlet port for the IAC in the TB with a finger or thumb (you need asbestos fingers, a cloth or rubber strip). The engine may stall if you do that so either crack the throttle open by hand or vary the amount of blockage to prevent that. Then, with the IAC port still blocked, adjust the throttle stop to achieve an idle speed of ~500-550rpm. Basically the minimum speed the engine will continue to run at. That's it.

If you really want to you can idle the car in gear and a out of gear with the A/C on and off for the ECM to relearn the IAC valve position but it will do it anyway if you just drive the car.
 

Jxfwsf

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fault code check?

didn't miss something with the swap? dodgy perished/missing vacuum line? forgot to plug a sensor in?
 

vn3.8L

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Ok somewhere I have a spare gasket for the throttle body, I will swap the throttle body off the old engine into the new engine. Also I should add that the car cranks for a while before starting when its hot.
There was one line that has an apparent crack in it where the clamp goes but when i inspected my other engine the line also looked rather perished with similarish cracks. Its a brownish looking tube going directly from under the throttle body to the inlet manifold.
I checked the leads and they were in the resistance specs, when i changed the engine i replaced all plugs bar one that shattered when I dropped it on the ground. I also used the whole coil pack setup from the old engine that worked fine. So I don't think there are to many other things that it could be.

Do you think that it could be that brown tube I have noticed?
 

Jxfwsf

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If that tube is cracked then replace it but i doubt it'll be causing the issue, it's part of the pcv breather setup, it's before the butterfly so it shouldn't be affecting it to much though... problem is oil gets sucked in through it and over time hardens and deteriorates (can't do much about it due to the design)

Try changing the injectors and rail from the old engine as you know they were good.
Try changing the entire TB and iac over from the old engine also (this will also include the tps but with the other symptoms i don't think it'll be the tps)


I've had pretty much the same issue but it was a dud ecu that i'd swapped in.Did you do a fault code check yet? might show something rather than replacing random things.....
 

vn3.8L

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Now I have pulled it apart and forgot to check for faults. I think I have found the problem. I noticed that there was some fuel residue in the tb. Then when I pulled the tb off. I have noticed if you look in the inlet manifold its full of fuel. Now what could make this happen. The only thing I could see linking is the vacuum from the reg to the tb. But it doesn't really seem like theres fuel in it. Im gonna replace it with my old one anyway. But is there anything else that could explain this.
 
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