Mexi TB mods?

[Humpty]

Hey gang.... I am in the process (read: early stages) of tuning my recently installed MS1Extra setup in my Bus.... I have used the complete Mexi TB hardware setup I bought off Mario a few years back.

Whilst battling with the tune, trying to achieve an idle, get decent afr's and tidy ignition map (none of which I have achieved), I discovered that a nice'ish idle was produced when a folded piece of cardboard was lodged under the throttle stop... This has opened up the throttle plate a touch, which is letting air into the manifold.... As you would expect.... My afr reading settle down on the gauge and in the TunerStudio too.

So my question is this..... How the F^%k is air supposed to get in, if the throttle plate is closed at idle?

Is there supposed to be a bypass hole in the throttle plate?

How big?

[Chip Birks]

Do you have an idle valve? The intake is designed for one of those.

I had one.

I also ran a hose off of the larger of the 3 vacuum nipples to essentially free air, you could out it into your air cleaner. This helped with the early throttle use a lot.

[Humpty]

Having never seen a Mexi efi setup before (we never got them in Australia), I have no clue what to look for Chip.... All the ports in the manifold centre were capped, except for the two small vac ports the lhs... One I have capped, the other is my MAP signal.

What would this idle valve look like, and where is it situated?

[Humpty]

It's that black cylinder thing between the fan shroud and the TB right?

So the 'work around' is to vent the larger vac port to the intake, Chip?

[ps2375]

Not a "work around", you add an idle valve that is controlled by MS to meter air in. If using a 2 wire Bosch type valve, the board will need the "TIP120" mod kit to control it. When I had this setup on my water-cooled VW, I could reach in window and start car on a 0degree morning, and it would start and idle.

[Humpty]

Not a "work around", you add an idle valve that is controlled by MS to meter air in. If using a 2 wire Bosch type valve, the board will need the "TIP120" mod kit to control it. When I had this setup on my water-cooled VW, I could reach in window and start car on a 0degree morning, and it would start and idle.

Well that's put a spanner in the works...
Looks like I am going to have to go on a parts scrounge. VW of Mexico parts are just not available here.
Are there any known valves that can be adapted that don't require the board mod?

[Chip Birks]

I don't know if ms1 has great idle valve PWM control options as it is. Might not even be an option for you. The larger of the 3 vacuum ports is what I would connect to your air cleaner. It is not for the idle valve. If you look down the throat of your TB, at partial throttle you can see a hole in the wall. That is connected to that port. Make sure that your gasket under the TB has the hole as well. The huge port 19mm-ish behind the throttle body is where the idle valve goes.
I have never gotten mine from a Mexican beetle. Mine all came from other 80's or 90's water cooled VWs. Just make sure they are 2 wire. They are Bosch, and usually silver.
https://www.google.com/search?q=bosch+2 ... p-vJ2PM%3A

[ps2375]

Any two wire valve from a digifant car will work. And MS1 does not have good PWM for idle valve, at least to control idle speed (it will hunt up and down). I had mine setup as mainly as a warmup valve for aux air during such and it had a duty cycle of 0% when car was at temp. The TB I was using had an bypass adjust screw to allow some air past throttle plates when it they are closed. I simply set my warm idle as I needed/wanted it, tuned for that, then set enabled the warmup valve and the duty cycle and had TS tune the enrichment.

So, you may need to adjust your throttle stop screw a bit to allow some air past it when at closed throttle.

The current transistor on the board can control a relay to control the valve, but it is more of an ON/OFF control of the valve and works poorly in a PWM/duty cycle mode. The mod is taking out the standard transistor and installing the TIP120 transistor and mounting it on the case end for heat sink purposes. I've done it on both v2.2 and v3.0 boards.

[Humpty]

Status update:

Contacted Mario regarding this issue.... He suggested that I shouldn't need the valve. None of his previous customer installs did.

Also... Have determine that the base map that was installed on the ECU didn't port to the Mac when I plugged in, so I have kinda been flying blind in an attempt to build my tune from scratch... Kinda hard when I can't get an idle and my advance is most likely off.

Hopefully he will come up with a suitable base .msq and we can then go from there.

Here's hoping.

PS: if all else fails I have a MS2v3 sitting on the shelf I could chuck into the Bus...... Hhmmmmmm?

[Humpty]

Status update:

Contacted Mario regarding this issue.... He suggested that I shouldn't need the valve. None of his previous customer installs did.

Also... Have determine that the base map that was installed on the ECU didn't port to the Mac when I plugged in, so I have kinda been flying blind in an attempt to build my tune from scratch... Kinda hard when I can't get an idle and my advance is most likely off.

Hopefully he will come up with a suitable base .msq and we can then go from there.

Here's hoping.

PS: if all else fails I have a MS2v3 sitting on the shelf I could chuck into the Bus...... Hhmmmmmm?

[Chip Birks]

Idle valve is definitely not required. They sure don't suck to have though. As far as the needing a lot of throttle to get any response from the throttle body goes, that's where the big vacuum port on the side is useful. There are also a bunch of people that port the throttle body a bit. I think Mario did that back when he ran the Mexican TB.

[Humpty]

So it's time for an update....

Mario came through with a new .msq file.... Loaded it up, and the engine fired up pretty well, but still didn't idle... After a number messenger chats across this big blue planet, we had it working really well.... Think about that.... Mario is over the on the west coast US..... Im here on the west coast of Australia! That's a 15 hour time difference!

Anyway.... After a little fiddle with the throttle stop, I had it idling nicely.... Still the afr's were way too lean.
So I took a punt.... I hit the autotune button.... After a couple of minutes idling, the autotune function started to clean up the VE.... Amazing!

Haven't taken the Bus for a drive yet.... Still doing body work, but hopefully early next week and can begin the road tune.

Fun times ahead.

[Piledriver]

i ran a cis warm up air valve for extra warm up air for awhile, worked well for cold starts etc.
A lot of ljet and djet cars ran similar, a T3 with djet had one that bolted in where the fuel pump goes.

The control signal for those valves is 12v power off the ignition, runs a heat element.
I'm thinking the T3 version only used engine heat.

[gtmdriver]

The IACV is not essential but even running open loop it will give you the fast idle you need for cold starts (do you have them in Australia?).

I'm running with in this configuration so the idle valve opens up when the engine is cold then progressively closes as it warms up. Once the engine is up to temperature the idle valve is shut and it idles on the throttle plate.

If you go to full closed loop the throttle plate can be completely shut and the idle valve will control the idle speed regardless of engine temperature. It can also compensate for additional loads such as AC etc.

If your system has no IACV provision it is possible to fit one using a remote body from DIY Autotune.

https://www.diyautotune.com/product/cus ... iac-valve/

This connects from the air filter to a point downstream of the throttle valve.