EMPI 44's tuning

[brainsboy]

http://www.youtube.com/watch?v=j1ZIIVsUV3U


Hi guys, Im new here. I dont have a VW but I have a 91 miata with a V12. I'm having some problems getting these crappy empi's tuned in, wish I never bought them but I have to live with it since I have 6 of them now. The motor is 441CC per cylinder and I'm running 200air 135jets, .57 idles stock vents (36mm I think havent checked). I was getting a horrible mid stumble also crusing just off idle I get constant backfiring from too lean. I kept moving up to larger jets several times, now Im at 165jets which helped 85% of the mid stumble but now feels like its running to rich at 3000rpm cruising. The richness is liveable but I still have something that doesnt feel right during cruise. I also get a big bog when I jump on the throttle.. For some reason accelerator pumps work perfect when the carbs are cold, but after everything heats up and I look down the carb the accelerator pumps arent working for whatever reason. Carb pulls harder at 50% throttle than full throttle. Im wondering if I need to start all over with maybe 32mm vents.

Thanks in advance.

[mharney]

We talked in email, I believe.

Those carbs are too big for that engine, unless the cam and heads are crazy.

32 vents oughta help some. The floats are the most important thing before you do much else.

As far as the accelerator pumps not working well when warm, it may be the crummy diaphragms or bad pump exhaust valves. I have also seen these carbs have the bleed plugs in the housings just out and laying in the pump housing. The plug closes a hole that is between the pump chamber and the float bowl.

6 HPMXs on one engine, you're bound to have a challenge. Check the floats and make sure they're set right for starters.. if they're wrong you're bound to get a flat spot. Lazy pumps will surely cause it to nose dive when you put your foot in it quickly as well.

[DarthWeber]

A Miata with a V12?? I'd love to see that, can you post some pics? I've seen a Miata with a 5.0 liter Mustang engine but never a V12.

[brainsboy]

How do you set the float height on an empi? The floats have a ball that compesses when the float rises, so what do I set the height to and do I compress the ball and spring when I check height or just as the float touches it?

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[mharney]

Just as the float touches it. 10mm.

[Art Thraen]

Im not sure if I want to post on this, but I will.

The carbs are in need of set up prior to installation. They all need to be calibrated together and the vents MAY need changed.

If you had WEBER, Dellorto, solex you might just have the same problems. Approach this with a detailed list of events, like fuel pressure, float height, Check the size of ea Jet, timing, Advance curve, ETC Make a check list and go step by step.

HECK, I had a 914 in the shop this year that had the same tuning Problems you have, The owner was blaming the carbs, (Because the engine was just rebuilt) by a shop in the area, but the other shop was "NOT A CARB GUY" they brought it to me, They had the timing off 20 degree, the floats were off and they had the wrong spark plugs in the engine.
After 4 hours of tuning the car ran better then it had in 10 years!

APPROACH this slow, and hold back the blame, The HPMXs will work.

[brainsboy]

[pdub]

Well, Mark, are you going to enlighten this gentleman to EMPI and what you found when you took a couple of these carbs apart? Nothing from China works right out of the box and that is especially true if it is an EMPI product. Buena seurte con estos...oh wait thats Spanish, not Italian, close enough. Chao for now.

[Scott Novak]

Even Webers made back in the 70's needed to be cleaned and setup by someone before using them.

There is also the possibility of incorrectly marked jets, or jets that have been drilled.

You can also test your jets by running water or some fluid through them and measuring what kind of volume will flow in a given time period to make sure the jets are all matched.

Scott Novak

[junior55]

Your project is outrageous !

And well worth the time and effort you are putting into it
because its so mind blowing.

Not to be a wet blanket but I would have gone with a simple form of fuel injection and throttle bodies in place of your carbs.
The look would be the same or even better with a hi-pressure fuel rail going around to 12 injectors!

Anyway, good luck with the carb tuning!

[mharney]

[Scott Novak]

[junior55]

Bail on the carbs and call CB., redline.. megasquirt etc for v12??
CB had V8 kits running simple batch injection on their early FI.
Probably just a little more than you've got invested in carbs that may never be too impressive in the fuel management department.

I will bugg-off on the FI as of now.

[MURZI]

I would bet the 32 vents would make that engine alot more responsive. 130 mains with 52.5 idles would be a good starting point.
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[brainsboy]

I took 3 of the 6 carbs apart. Main gaskets ripped apart so Im down for the weekend now. Are you sure .390" 10mm is the right setting for empi floats? All the carbs have the same setting which is right at .500". I just set them all to .390" but when fully compresed (ball down) the top of the floats come about .025" from hitting the bottom of the main gasket.
In your notes you show a section of the carb (not sure what its called) that pops loose with a spring behind it. I took mine out with a screw driver and removed the spring, looked inside and it was full of metal. Each carb had 2 of these, I had 3 of the 6 with thrash sitting in the bottom of them.

So Im going to take all the carbs down and start from scratch. Probably buy one of those gallon carb soaker kits unless you plan on letting me know your secret formula for cleaning carbs.

Thanks for the help so far guys.

[Viande]

Mark's words are as true today as they were when I was working with Italian Webers 20 years ago. Damn I'm getting old. Disassemble, Clean, Inspect and Set before you ever bolt on a carb. All the low grade Chinese parts have added an additional step to the mix. Repair. Good luck with your project.

[brainsboy]

Special thanks to mark too, he spent alot of time prior sending me e-mails on these carbs.

Its kind of funny, I can build holleys all day long even blind folded and with my toes only. These are my first webers and I have 6 of them linked together so its makes for a new experience.

While were on topic of empi 44's. I havent seen anything that really explains what the air-jets do. Can someone explain? Once I get things closer to being correct with jets and all, and I have 200 air jets, what would happen if I put 180's in? or went the other way with 220's?

Alot of these questions are because I dont have one carb. If I had one carb I could do all my own experiments to learn on my own. But It costs me about 65$ just to change the jets once.

[DSF]

bigger air hole (220) = leaner.
smaller air hole (190) = richer.

Awesome project!

[brainsboy]

My throttle shafts are loose as MARK said above. He mentioned that the outside bearing areas can be fixed however the inside portion can not be. I was thinking about putting the throttle shaft in my lathe and cutting two spots to run rubber seals. Any thoughts on this?

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