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AXD to BNZ engine

24K views 21 replies 8 participants last post by  bobley 
#1 ·
Hi All,
I have just installed a BNZ into my VW caravelle, in place of the original AXD engine (don't ask) and apart from the turbo being different, everything has gone in no problem. Got it fired up, very smooth and very refined, but flat as a pancake!

on the flat it really struggles to get past 80mph, and according to the instruments its doing 21mpg - will verify this bit later. I have had my vag com on it and there are no error codes at all, everything is happy on the engine. I measured the boost and according to vagcom its producing the right amount of boost too, spiking just over 1bar, dropping back to 0.9bar and holding through.

Its got me a little baffled. If its boosting, and it doing 21mpg (ie chucking loads of fuel in) then it should be flying ?

any ideas anyone?

I had driven the van the BNZ engine came out of and it was much much quicker in there. something is a miss. The cam timing marks arent different on the BNZ engines are they?

Thanks for you help guys

Ian
 
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#3 ·
I am using the axd engine management system, otherwise I would have to be swapping looms as the BNZ managment uses a lambda probe which the AXD one doesnt.

Not sure a standard remap will help much. I need to know why its not working properly before I do that.
 
#4 ·
A restriction in the intake maybe? The AXD has a vacuum operated changeover valve (flap) as part of the EGR valve but I'm sure the BNZ has an electrically operated EGR valve so if that is different I wonder if the changover valve is too. It's worth checking it is fully open once the engine is running.

Do the MAF expected and actual figures match up pretty well on VCDS?
 
#5 ·
thanks for the replies, I have not checked the maf yet, and you are right about the intake flap, I swapped the older vacuum operated axd flap back onto my engine when I did the swap. it sits in the open position as default and i tested it by disconnecting the vacuum so it could never actuate. no different.

I think I may have found the problem though - the brake switch. I have read on the measuring blocks that 2 bits should change when I press the brake switch, only one changes, so I am going to check that the other one is permanently on then go from there.

I think that may be the issue.

will let you all know when I test it

thanks for your help

Ian
 
#6 ·
bah! no cigar, both the brake and clutch switches appear to be working perfectly.

its boosting up to 1.1bar, and settling back down to 1 bar through the rev range.

the MAF appears to be working correctly going off the measuring blocks.

Not sure what else is left? its got to be fueling. Not sure where else to look?
 
#8 ·
So you running lambda in this vehicle or not?

Its a simple fix either way, as within the software there is a switch telling the ecu what smokemap based map to use, there is a few options

Smokemap MAF
Smokemap MAP

or Lambda Based Smokemap.

Any no vagcom cannot switch these, you will need to get someone who can read the original software out, know within the software how to switch these and them write the modified software back in.

If you need anymore help just ask.

Regards
Martin
 
#9 ·
Just one question - who can read these cos I cant! I think I have pretty much exhaust all component failures, I am going to swap the map and the maf sensors this afternoon see if that helps. if not its got to be differences in the injectors?

point to note I get no smoke what so ever from the motor. its as if its just not putting anywhere near enough fuel in.

Must be mega lean.
 
#10 ·
What happened to the original engine? If the exhaust it full of oil it could have blocked it. Same with the intercooler. The Map overshooting the requested boost by a bit is fairly normal. I think the map is part of the ECU so you won't be able to change it separately anyway.

You said the donor engine had a lamda right? Your engine is supposed to work with a lambda but your ECU isn't. The correct way to go is what Martin says (and he should know!) fit a lambda and get the ECU re-mapped. But there are costs involved.

You are in new territory with your new 'hybrid' van but you have done pretty well to get this far! I'd say make sure that you really have exhausted all the possibilities of intake, fuel or exhaust system restriction then take up Martin's kind offer of help.
 
#11 ·
no blockages beforehand, so I doubt there would be any now. if anything it will be much freer flowing give the bypass pipe I have on mine now.

did some logs and found something interesting. The first is measuring block 5 - shows inj. quantity. it doesnt change at all, and I would expect it too.
the next is the injector correction values on measuring block 13. It shows 2 of them with very negative values, and 2 with quite high positive ones. Now I have changed the injection loom in this head and had a right faff on getting that stupid twist lock working. Could it be possible I have got the injections loom 180 degrees out?

I guess it would still run as its mechanically operated. but the timing would be way out. the engine still runs quite smoothly so I would have expected not. but i am going to check anyway. nightmare.

No fault codes anywhere, this is the only thing left!
 
#12 ·
Please understand its nothing to do with blockages or anything else wrote in here, changing the maf, map, lambda etc etc etc will give no difference...

Its to do with how the control unit is controlling the system and this is why its holding fuelling back.

You could do a simple test of disconnecting the Lambda Sensor (and I mean leave it disconnected at the socket) and then driving while logging blocks 001 which is the injection quantity.

All this vehicle needs it setting up correctly inside the engine control unit.

Regards
Martin
 
#14 ·
If you give a 100% full parts list that has and hasn't been changed on this vehicle I will be able to give you the info why its doing what its doing.

You see these engine control units are very complex and if they are not getting the signal back they expect it will cut fuel or stick it in limp mode, this isn't going into limp mode as there are no fault codes.

If you are in our area at all pop in and we will run some diagnostics FREE for you.

Regards
Martin
PendlePerformance
 
#15 ·
ok then here goes.

I have 2 vehicles, 1 an 08 transporter with a BNZ engine code, and another an 04 caravelle with an AXD engine code.

I have swapped the blocks over so the newer BNZ engine now sits in the caravelle and the AXD engine in the transporter.

I have retained all the original sensors on the caravelle, and the same for the transporter. The caravelle has no lambda control. the transporter has.

so the only thing that could be causing me problems is the injectors, which must be different, although I was led to believe they were the same. maybe same size but fire on different signals or something?

Just add something else into the mix, I have removed the DPF from the 08 vehicle, so as well as any possible running issues that will have (I haven't finished building it yet) I am going to have to have that removed too.
 
#16 ·
Hi, did you manage to get you bus to perform. Mine does the same as yours and iv'e tried changing everthing except injectors. Its a 55 plate axd with high millage and i'm starting to think someone might have changed the motor for a bnz. do you know where the engine number is. all the best
 
#18 ·
Hi.
A little help from Denmark.

I have made the same change from a axd to bnz Engine.
No particle filter ( sorry for my english), and blocked Egr system.

With same result as you. Irs totally dead.
Allmost cant get past 120 km/h, and no torque.

Well today i had it ón a dyno run, and it produced 97hp, and 265nm torque.
So something was wrong.

We Them compared how much fuel the axd and bnz enginecontroller was putting in for each cylinder.
And there is a huge difference there.
The axd used a lot less, Them the bnz, so we copied the data fron bnz into the axd controller ón the car, and i now have 177hp, and 485nm.

So get your enginecontroller updated with data from a bnz controller, and you should be flying :)
 
#21 ·
hi Onlynumber1, here form italy milano, i hope everythings it's ok in your covid lockdown moment.

i would like to I would like to replace my bnz engine with an axd. the opposit of the topic.
Reading this post I did not understand if it is a feasible thing or not. so you say that everything works, just copy the data for the flow of diesel from one control unit to another and everything will work better than before? quite right?
can you advise me to take this road?
thank you
carlo
 
#19 ·
Good post mate and your english is good. I have a AXD T5 and i have change so many parts to fix my under powered van with no joy, feels like i'm only getting half throttle. do you know where the engine number is stamped on the block to see if the engine has been changed to a BNZ
 
#22 ·
Basically the injectors in a bnz are very low flow by comparison to axd. The injection system is designed to work very differently. To make the changeover work effectively you need to have the ecu custom mapped to make up for the change. It's not really something you can do at home.
 
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