TheSamba.com :: View topic - Simplified TDI electronics for AHU conversion ?

Mon Dec 06, 2010 8:38 pm

After driving my AHU conversion with a 1.6 turbo pump setup for some month now I was lucky to find and inexpensive AHU wiring harness and AHU ECU. I dissected and stripped down the wiring harness. This process was pretty straight forward using the Bentley manual but very sticky as the wrapping tape was held by some nasty semi dissolved glue.

In order to simplify the electronic setup I like to the use only what is absolutely necessary:
So what can I eliminate without throwing the ECU in limp home mode?

1.Can MAF and EGR be eliminated? I have an AAZ manifold without EGR and I do not have an MAF sensor. (not connecting Pin 13, 19, 25)
2.The ECU gets 3 temperatures: 1 Coolant temp , 2 Fuel temp , 3 intake air temp.
Is the intake air temp part of the EGR system and can it be eliminated? (Pin 64)
3.Can I use the Vanagon glow setup without ECU control (Pin 50,48)
4.Does the ECU need a speed signal to run the IP correctly? I assume this input is only for cruise control (Pin 43)
5. further more I like to go without:
5.1 Cruise control (Pin 17, 20, 34,35, 43,44,65,66)
5.2 Air conditioning (Pin 37, 28)
5.3 Coolant heater glow plugs (Pin 6, 26)
5.4 Coolant pump ( pin 3)
5.5 Alternator / ECU connection (pin 39)
6.What does Pin 68 do ( Still cannot figure out where this goes in the TDI dash)

If all above could be eliminated it would leave:
-Pump control and shut off (Pin 4,5,7,29,49,51,52,53,63)
-Crank position ( Pin8)
-Injector #3 stroke (pin 11,12)
-Boost regulator (pin 47)
-Ignition power (pin 38)
-TPS pedal ( 62,65,55,57,15)

7. Has anyone tried to actuate the TPS with the Vanagon throttle cable and placed it in the in the engine compartment?

Mon Dec 06, 2010 11:23 pm

You will get a CEL from getting rid of just about any one of those, but not limp mode, I think. Where you want to remove so many inputs though, hard to say what will happen, no MAF and no IAT (intake air temp, not part of the EGR) might make it limp. The speed signal is just for the cruise control and can be eliminated.

vintagemotion wrote:
So what can I eliminate without throwing the ECU in limp home mode?

1.Can MAF and EGR be eliminated? I have an AAZ manifold without EGR and I do not have an MAF sensor. (not connecting Pin 13, 19, 25)
2.The ECU gets 3 temperatures: 1 Coolant temp , 2 Fuel temp , 3 intake air temp.
Is the intake air temp part of the EGR system and can it be eliminated? (Pin 64)
3.Can I use the Vanagon glow setup without ECU control (Pin 50,48)
4.Does the ECU need a speed signal to run the IP correctly? I assume this input is only for cruise control (Pin 43)
5. further more I like to go without:
5.1 Cruise control (Pin 17, 20, 34,35, 43,44,65,66)
5.2 Air conditioning (Pin 37, 28)
5.3 Coolant heater glow plugs (Pin 6, 26)
5.4 Coolant pump ( pin 3)
5.5 Alternator / ECU connection (pin 39)
6.What does Pin 68 do ( Still cannot figure out where this goes in the TDI dash)

If all above could be eliminated it would leave:
-Pump control and shut off (Pin 4,5,7,29,49,51,52,53,63)
-Crank position ( Pin8)
-Injector #3 stroke (pin 11,12)
-Boost regulator (pin 47)
-Ignition power (pin 38)
-TPS pedal ( 62,65,55,57,15)

7. Has anyone tried to actuate the TPS with the Vanagon throttle cable and placed it in the in the engine compartment?

Tue Dec 07, 2010 12:14 am

generally the engine functions and emissions codes will cause a limp mode, or trans codes if automatic. depending on the year.
my project states 17 codes that will do that, which tells you how to orchestrate the wires.
get the vw tech diagnosis manual for that model and year and read the injection operation section. it will define what everything in the system does at what voltages. if your donor is a lot later than the van, you stand a good chance of having more info than the van bentley.
good hunting

Tue Dec 07, 2010 7:40 am

thummmper wrote: generally the engine functions and emissions codes will cause a limp mode...

You don't mean CEL instead of limp mode? Lots of things will give you a CEL but the engine will still run "normally", that is, not in limp mode.

Tue Dec 07, 2010 8:05 am

Having seen what the EGR did to the intake system on my Passat tdi and Mercedes diesels, I've been operating under the assumption that the tdi tuner guys have found work-arounds for the ECU feedback loops. There must be some way to trick the ECU into thinking that the EGR is functioning correctly. If not, then there's yet another strong argument in favor of going the M-tdi route.

EGR is evil:
http://tinyurl.com/23muorv

Tue Dec 07, 2010 8:27 am

Zeitgeist 13 wrote: There must be some way to trick the ECU into thinking that the EGR is functioning correctly.

Any of the TDI chip tuners can modify the tuning so you won't get a CEL with the EGR system removed. BUT to be totally clear here, a CEL is NOT limp mode, and removal of the EGR system will NOT cause limp mode,s o you really don't have to do anything to remove the EGR.

Zeitgeist 13 wrote: If not, then there's yet another strong argument in favor of going the M-tdi route.

But that assumes there is one argument to start with :lol:

CEL stands for Check Engine Light, fwiw.

Tue Dec 07, 2010 11:19 am

FWIW I believe David Marshall @ Hasenwerk (ex fast forward) sells ready to go harnesses. I'd be wary of wiring it so it is always throwing a CEL, it'll drive you nutz & mask any real issues.

Tue Dec 07, 2010 4:27 pm

Any recommendations on a tuner that could delete the EGR, MAF, IAT, function from the ECU?

It is my understanding that information from the MAF and IAT is used to trigger EGR activation.

Tue Dec 07, 2010 10:03 pm

BlackDogVan wrote: Same mileage...

Your van is an M-TDI, my van is an E-TDI, and my van typically weighs about 800 pounds more than your van, and has has worse aerodynamics, yet it gets a bit better MPGs than yours. I'm sure your van is really nice, but I don't see how you can claim the same MPGs as an E-TDI when the numbers don't support it.

BlackDogVan wrote: I'd be wary of wiring it so it is always throwing a CEL, it'll drive you nutz & mask any real issues.

The CEL only alerts you of things that are pretty inconsequential, so if the CEL is on all the time it doesn't matter much. If there is a "real problem" the van will go into limp mode and you'll know.

vintagemotion wrote: Any recommendations on a tuner that could delete the EGR, MAF, IAT, function from the ECU?

It is my understanding that information from the MAF and IAT is used to trigger EGR activation.

EGR deletes are pretty common, and MAF deletes are done as well, but not to often, I hear you lose a little efficiency with a MAF delete, but an IAT delete? Its probably possible, but I've never heard of it being done.

EGR is adjusted mostly (entirely?) by throttle position, the ECU does "look" for a drop in the MAF reading based on how far the EGR valve is open, if the ECU does not see a corresponding drop in MAF reading when the EGR valve is supposed to open the CEL comes on. The 2 are related, but the MAF does not "trigger" the EGR. The IAT could play a bit of a role in the amount of exhaust that is recirculated, but I've never read of a relationship between the two, and my bet would be on "no".

http://malonetuning.com/ can set you up with whatever custom tune that is possible, or http://www.tdtuning.com/wp/ or, http://rocketchip.com/

Mon Aug 22, 2011 7:54 pm

Finally I was able o test my wiring experiment on an extra AHU engine I have. I was able to get this setup running in my shed using a bell housing and starter. The motor runs well and response to the throttle even only being connected the pump, RPM and number 3 Injector sensor. I'm very happy that everything works but I'm I’m sure it threw all kinds of codes :-)

Here are some concerns about the things I still have to do:

1. Placing Throttle sensor
I have 3 sensors: original AHU, VW VR6, and Mercedes E320
I like the Mercedes sensor the best since it is made to be placed in the engine compartment and is actuated by a wire and a conventional foot paddle. This way I could leave Vanagon pedal and cable original.
I’m not sure yet if the Gasoline sensors could work.
2. Where would be the best location for the ECU?

Here are some pictures of my experiment:

https://picasaweb.google.com/102818215803434008541/VanagonTDI

storing the extra Motor :-)

Mon Aug 22, 2011 9:01 pm

Here is a chart I made to compare the signal for 3 different Throttle sensors.
Has anyone ever tried to use a VW gasoline throttle sensor for an AHU?

Mercedes sensor would be great to place in the engine compartment - even the ball connector for the throttle cable fits!!

Tue Aug 23, 2011 5:16 pm

Nice work man, love the setup you've got rigged in the garage! Its the ultimate tdi mobile! Keep us posted - the more tdi stuff the better :twisted:

Tue Aug 30, 2011 9:50 am

The TDI Vanagon is back on the road and here more questions:

1. Does anyone know by own experience if the absence of the Mass Airflow Sensor would get the motor in a Limb mode? I drove the Van the first time with Turbo installed and it runs good. It accelerated easily to 65MPH but I’m not sure what to expect since I have never driven a proper TDI. (it may already be in limb mode)
I like to take a longer trip this weekend and have not being able to place the MAS and now wonder if the ECU will go into a limb mode and how limb that would be?
So far I have only driven some 30 miles and all seems OK.

2. Another question regards the placement of the intake air temperature. Where should sensor be positioned (never saw the donor car for this engine)

3. ECU placement. At this point the ECU sits temporary behind the battery (my Vanagon is a Diesel with Battery in engine compartment). I could only find one post with a picture of the ECU under rear bench. I wonder what the best or typical ECU location on TDI Vanagon would be.

For now I used the original AHU Throttle sensor and placed it in the engine compartment. It is actuated by the original Diesel Vanagon throttle cable.

Tue Aug 30, 2011 10:35 am

vintagemotion wrote: (it may already be in limb mode)
You should have a computer watching to see what is going on. Just use a netbook, the cheap USB adaptor and the free version of the Ross Tech software. I use that setup with success on my TDIs.

vintagemotion wrote: 2. Another question regards the placement of the intake air temperature. Where should sensor be positioned (never saw the donor car for this engine)
I would be hanging resistors to simulate all these signals you keep wanting to ditch. keep the ECU happy!

vintagemotion wrote: 3. ECU placement. At this point the ECU sits temporary behind the battery (my Vanagon is a Diesel with Battery in engine compartment). I could only find one post with a picture of the ECU under rear bench. I wonder what the best or typical ECU location on TDI Vanagon would be.
Many engine conversions park the ECU under the rear seat by left side to keep it out of the way and safe. That is the location I choose for my Subaru conversion. It is where the factory had the ECUs in the later gas vans. It is a safe spot. PLUS you can hook up lots of stuff from the corner to keep the ECU happy.

Wed Sep 07, 2011 11:59 am

The first camping trip and almost 1000 miles on my E-TDI went well. Fully loaded with people, water and food some long hills were taken with 65 MPH where before I had to down shift at 55PMPH. The fuel economy on this trip was similar to what it was before.
75MPH can be reached easily on a road without incline.

As it can be seen on the pictures above I’m using an AAZ intake / exhaust manifold without intercooler. No EGR system, no MAF sensor, (The computer did not go into limp mode)

The over all level of noise is still too much, even though the Turbo cut down on the Intake and Exhaust noises. The next thing I will try is a different Engine mount.

Wed Sep 07, 2011 12:07 pm

I have a TDI in my bus and the noise is a little bit too high, specially in the rear seat. I know I have a lot of noise from the intake, I'm using an open filter at the moment. I think I'll make a new filter box with a snorkel going up the vent, something like the original construction.

I also think that the vibrations going through the surfaces covering the compartment itself is a lot of my problem. My plan is to add another layer of dampening in the coupé and I was recommended to buy a dampening material called "Dynamat". I will not buy it though, it's way too expensive. I'll try to find something similar.

Just my two cents. :)

Fri Sep 09, 2011 5:51 am

try megamat, it's 4x cheaper for a similar product.

GSB