Mexican throttle body anatomy!

[vwgillybilly]

Please could someone talk me through the anatomy of a Mexican throttle body?

I know which the TPS and IAT are, but what is the black valve to the rear of the TB and what is the white valve on the pipe running off the plenum to the left of the TB? What do they do? Are these needed for a Megasquirt applications?

Again my inexperience shines through here! Sorry for there not being an embedded image but photobucket doesn't want to play ball today. The link below should work.

http://i385.photobucket.com/albums/oo29 ... e93123.jpg

Thanks.

Gill.

[DRED]

hello,

the black one is use to regulate the idle, the white one is probably the canister for the fuel vapor recycling..

[vwgillybilly]

Thanks DRED.

Would it make sense to ditch these when using Megasquirt then? I'm pretty sure the white vapour recyling thing can go, just not sure about the black idle valve. Would this lead to erratic idle if I removed it?

Thanks.

Gill.

[Clonebug]

Megasquirt has cold idle control. Whether it is compatible with that valve or not is another question.

It is more than likely a Bosch valve and probably could be incorporated into the system.

Clonebug

[mach4]

I gave up attempting to use the Mexican throttle body. There is one big problem with it and that is it is designed in such a way that for the first third or so of throttle valve travel, there is virtually no additional air that enters the engine. The sequence of pictures below illustrates the problem (I apologize for not having better pics)

In the first image the throttle valve is in the closed position. If you look very closely you will see a sharpie line to mark that position. In the second image the throttle is open about 15% and you can see (if you look close) that there is no daylight between the throttle valve and the throttle body itself. In the third picture we're at about 30% and there is just a hint of daylight. The final picture shows the throttle valve mostly open and you can see that there is a curved area of the throttle body that essentially follows the arc of travel of the butterfly during the initial stages.



Somehow the Ralenty valve is supposed to supply additional air during this phase of throttle opening. If you run the throttle body without this valve you will have to create a stop at the edge and live with only 70% or so of actual throttle travel. If you run it with the valve, you will have to figure out how to configure it to work with Megasquirt.

While I was researching this, I found out that the larger of the three "vacuum" ports in the plenum (not the big one in the rear of the throttle body) is designed to go directly to the air cleaner.



Personally , I gave up trying to make this work and went with a Ford Escort throttle body and fabricated an adapter to mate the plenum to the TB, like this



There is more information here on my experience with the Mexican TB - http://www.mach4.com/ms-project/60-wont-idle

[yvre]

Mmmm sh!t....
Do some people have a positive experience with it?

[mach4]

Do some people have a positive experience with it?

I certainly think so, but I don't know how, without mods. I did a ton of research before I opted to go the Mexi-beetle route and didn't turn up anything really negative which led me to the conclusion that this was a great way to go for a relatively stock VW. There appear to be a ton of these set ups sold - some as a "starter kit" consisting of end castings, center tube/plenum and tb all the way through complete kits that cost $1500 and include the starter stuff, plus alt stand, fuel rails, Megasquirt, seosors, EDIS, cables, regulator and so forth.

As I started researching the problems I was having I began to discover that things like drilling the throttle plate and porting the throttle body were common paths to success. In stock form, I think it's also pretty safe to say that using the VW idle valve is pretty important. All of that having been said, I've never found a build thread that took a "mexi-project" project from start to finish. I've never even found a VR table to be used as a starting point.

The real advantage to using the Mexican TB is that it uses the stock throttle cable. But fabbing up a different throttle cable for the new throttle body and building the adapter turned to to be almost trivial.

I too, would love to hear from people that have made it work along with a narrative of their process. I'm taking good notes and plan to post the entire build once I've achieved success.

[mcmscott]

I am using the Mexican system complete, down to the ecu. Runs great, I did port the throttle body to get the off idle to work right. If you look inside the throttle body you can see what the other poster is refering to. What it was intended for was fuel evap stratagie(spelling?). I used all the fuel evap components and used my original charcoal cannister, still had to port the throttle body. Engine is a 1904,cnc ported heads( Los Panchetos from CB) CB's 2280 cam with straight cuts, 1.5 in. heater boxes and a 1.5 in. equal length header all match ported, in a 74 Thing,

[Chip Birks]

Mario has had very good results with that TB. It is the only part of the Mexican system that he has retained...

[Theo]

Mmmm sh!t....
Do some people have a positive experience with it?

Yep, Mine works fine. I ported our the lip in the throttle body. Got rid of the Ralento valve and drilled a hole in the butterfly to let in some air. Works great. Throttle is very linear. At 1/2 throttle you have 1/2 power. With Webbers 1/2 throttle is like 85% power. I could use a cold start valve.

I think the Mexi system uses the giant air valve to precisely meter air for low rpm smog. It's a weird feedback loop that makes it work.

The mexi throttle body makes it so you can go 15mph in a school zone with out having to feather the throttle.

I like it. I would not use the system on a drag car.

[vwgillybilly]

Well thanks for the useful info guys!

Had a close look down the tb yesterday and saw the lip that sits up to the butterfly. I take it I need to remove that & smooth things out? I could do with some accurate info on what do do here as I don't want to ruin it!!! Same with drilling holes in the butterfly. Just to say I will be running this with a turbo.

So could I ditch the valve to the rear of the tb with MS then?

Cheers.

Gill.

[Chip Birks]

I liked the valve with my turbo setup, and ms.

[Theo]

Looks Nice Chip!

How did you get the valve to work with MS? It would be great to see how you set it up. I would love to try it on my turbo setup. I could not find any info on how to set it up with MS. I'm building another one for a Baja bug and would love to try to set up the valve...

I liked the valve with my turbo setup, and ms.

[Clonebug]

I 'll bet the Volvo 940 turbo Throttle body would fit on that ... it is a three bolt setup like that.

I happen to have one in my garage if you need some measurements.

I will be gone in the morning for the holiday but can post tomorrow morning or when I get back and Tuesday.


Clonebug

[Chip Birks]

Thanks! Its all different now though... The idle valve mod was easy. I was running MS2extra but it should work fine with MSextra as well. http://msextra.com/doc/ms2extra/MS2-Ext ... .htm#Fidle I just did this simple mod. My valve was just a bosch 2 wire type. Super common. Good luck with your project.