Noob VEMS questions

Discuss VEMS and other standalone ECUs

Noob VEMS questions

Postby nmerrill » Fri Jan 15, 2016 11:38 am

Hello folks,
I recognize many characters here from another place and time, though I mostly lurked over there.
Anyway, I've built an engine (2.6 NA 5 cyl. 20V), and was planning on running it on a 034 1b unit (that I own), until I stumbled on a lot of chatter on VEMS...

I'm not changing plans just yet, and this engine will not need any fancy ECU trickery to make it run, but, apparently I'm still looking into VEMS.
Not the least because I'm local to VEMS USA and local support would be valuable, though an email sent there days ago has gone unanswered....

So, I was hoping y'all could clarify a few details for me.

1) Does VEMS require 2 trigger inputs? I see lots of references all over to crank triggers etc, but can it trigger from a 5 window dizzy ONLY?
From the support Doc, it appears the answer is yes:

Crank Trigger
The trigger is the engine management system's most fundamental sensor, without one VEMS
cannot calculate engine speed or crank angle. If you are connecting VEMS to an engine that has
an existing engine management system, if not then a triggering method will need to be put in
place.


(note the typo!)

The simplest type of trigger is to use the existing distributor to provide a pulse for each cylinder.
This type of trigger is more than adequate for driving ignition through a distributor and batch fire
injection


2. Are base maps available, particularly for an NA 5 cyl engine?

3. If you were building a long distance traveling machine (vanagon camper), where driveability and total reliability are more important than highest performance, would you favor one ECU over the other? Why?

Thanks!
Nat
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Re: Noob VEMS questions

Postby Marc » Fri Jan 15, 2016 12:14 pm

Hi Nat,

yes, vems can trigger off distributor only. your timing accuracy suffers a little bit but for an na 20v 2.6 it should be fine. you only need two trigger inputs for crank-fire 5 cylinder support. 5 window dizzy it is possible to run off that only (just shipped a vanagon pnp setup doing exactly that).

yes it can be reliable as a daily.

base maps is something you need to talk to your vems distributor about. we supply them, but its up to the individual vems dealer to supply them (or of course you can get support through places like this from the excellent vems community).

Jason is a good guy (vems.us) but is very busy. I'll mention to him you are trying to get some info.
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Re: Noob VEMS questions

Postby dana » Fri Jan 15, 2016 12:28 pm

local to VEMS eh? You must be local to myself a few others on here then too. Do I know you? I find it hard to believe i dont know all the local OG audi people. :D

Built motor 7a sounds cool. Whats your car/setup?
current:
-mk4 tdi wagon with some mods
-TDI b3 90q, holset turbo, be strong little connecting rods!
-the turbo tractor
past:
-11 second 90q junker
-20vt swapped 90q winter beater
-efi 10vt 4kq
-way too many other long gone urs's, 200's 4000's, b5's
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Re: Noob VEMS questions

Postby nmerrill » Fri Jan 15, 2016 1:20 pm

Dana, indeed. We have met - in fact the 20V head on my engine was bought from you if I recall correctly.
I had a 200 20V at the time, but this is an engine for my Vanagon syncro.

I've got a 2.6 eurospec bottom (from an MGer) with 9A pistons, 20V head, AAN intake, AAN acceessories (serp belt etc.), BOS header (at least for now).

Good news about the Distributor trigger. I'm using a flywheel from a South African 5 cylinder, and it has no trigger pins in it.

Considering this is for a Vanagon, and I won't be screaming around pulling 7K rpm, I'm guessing that it would not be worth it to put a crank pulley, or something (cam?) for better ignition resolution.
Or am I wrong?
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Re: Noob VEMS questions

Postby dana » Fri Jan 15, 2016 1:37 pm

nmerrill wrote:Dana, indeed. We have met - in fact the 20V head on my engine was bought from you if I recall correctly.
I had a 200 20V at the time, but this is an engine for my Vanagon syncro.


ah yes! I had completely forgotten about that. I thought your name sounded familiar. Welcome. If you've got time, it would be cool to see a project thread with some pictures of your swap.
current:
-mk4 tdi wagon with some mods
-TDI b3 90q, holset turbo, be strong little connecting rods!
-the turbo tractor
past:
-11 second 90q junker
-20vt swapped 90q winter beater
-efi 10vt 4kq
-way too many other long gone urs's, 200's 4000's, b5's
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Re: Noob VEMS questions

Postby nmerrill » Fri Jan 15, 2016 2:55 pm

I'll definitely throw some pics and details up when I get a chance.

Thinking about the Dist. trigger, I realized I don't know how that works -
spark is easy - ecu fires coil every stroke - the distributor, ahh.. distributes the spark to the correct plug, right?

But, how does ECU get cylinder # info for injector firing? Hall sender in Dist. with 5 window wheel doesn't provide different signal for #1

If I recall correctly, the 3B used Dist. Hall for #1 signal at start, then moved to crank signal for the rest.
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Re: Noob VEMS questions

Postby Marc » Fri Jan 15, 2016 5:01 pm

nmerrill wrote:I'll definitely throw some pics and details up when I get a chance.

Thinking about the Dist. trigger, I realized I don't know how that works -
spark is easy - ecu fires coil every stroke - the distributor, ahh.. distributes the spark to the correct plug, right?


yep.

But, how does ECU get cylinder # info for injector firing?


it doesn't. it fires "a cylinder's" fuel injector. its perfectly valid to fire an injector at a closed valve. consider that CIS back in the day is injecting fuel all the time to all cylinders (continuous injection system). its not ideal for emissions but has no real effect on power.
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Re: Noob VEMS questions

Postby nmerrill » Sat Jan 16, 2016 8:47 am

Right, of course. I.E. Non-sequential.

Thanks Marc
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Re: Noob VEMS questions

Postby nmerrill » Sat Jan 16, 2016 11:39 am

New question;
are folks mostly running harnesses direct from engine to ECU, or are they putting plug (s) in between - like the firewall plug group seen on many older Audis?

Pros/ cons?
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Re: Noob VEMS questions

Postby nmerrill » Sun Jan 17, 2016 1:08 pm

Another thing I can't seem to find a definitive answer to, is Vems compatible with LSU 4.2, or 4.9 sensors? Both?
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Re: Noob VEMS questions

Postby Marc » Sun Jan 17, 2016 4:31 pm

both. although the PnP is wired to one or the other (the connector is different).
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Re: Noob VEMS questions

Postby nmerrill » Thu Jan 21, 2016 10:27 am

Anyone have any input on my earlier question?

..are folks mostly running harnesses direct from engine to ECU, or are they putting plug (s) in between - like the firewall plug group seen on many older Audis?

Pros/ cons?

I'm wondering if the extra connections may be a source of issues?
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Re: Noob VEMS questions

Postby loxxrider » Thu Jan 21, 2016 11:48 am

It shouldn't be an issue as long as the area is weather tight. Many of us run plug and play ECUs which use a stock connection near the firewall. It's not a common source of problems at all.
-Chris

'91 Audi 200 20v - Revver/BAT project
'91 Audi 200 20v Avant
'01 Anthracite M5
'90 M3
'85 Euro 635csi
'12 X3
E34 530i (maybe rear-mount soon)
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Re: Noob VEMS questions

Postby carl » Sat Jan 23, 2016 5:18 pm

PNP is nice and no problem connector wise here either with stock engine harness. If you're doing a custom build imo it might be more practical for you to do your own harness, route wires where you have room, hide them properly and such.
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Re: Noob VEMS questions

Postby nmerrill » Mon Jan 25, 2016 12:11 pm

Yes, I'll be making my own harness - nothing to PNP with!

I was thinking that I would build an engine side harness that terminated on the firewall, or something, a few plugs dedicated to particular systems, like the Audi A6 (etc.) cars. O2, temp sensors, Dizzy Hall, etc.

Then that plug group would connect though the body to the ECU plug inside the van.
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