TB: converted carb or proper TB?

[65looter]

Hi,

I am new to MegaSquirt, I am planning to convert my 342 stroker to use EFI.
I am stuck between doing a sleeper look under the hood (using a converted Holley carb under a big oval air cleaner) or using an elbow with a proper throttle body.

What would you do

[PSIG]

Consider that some doing the conversion just shut fuel off to the carb - no mods necessary. Just resupply fuel to it to convert back. I've heard sowmobile jockeys do this to be sure they can get home from the wilderness. It might take some of the stress out of the project knowing you can switch back to carb control real easy - then go to a TB when you're confident.

The only irritant to this simple route is the placement of a TPS somewhere between the gas pedal and the throttle blades. Many have done it many ways. Although MS doesn't HAVE to have one it's a good option.

David

[65looter]

Although MS doesn't HAVE to have one it's a good option.

MegaSquirt does not need a TPS
how does MS knows about the throttle position?

[PSIG]

As a speed-density system, MS does not need to know the throttle position to run. You can add air by drilling a hole in the manifold and it will just run faster Seriously, the only functions MS needs TPS for are for Flood Clear where it allows you to stop fuel flow for flooded startup by flooring it, and Accel Enrichment where it measures the rate of travel (not true position) for adding fuel when you punch it - known as TPSdot.

The first one is easy - if flooded, pull the fuse on your fuel pump and get it going. For the second issue - the AE is now optionally handled by change in the MAP signal, known as MAPdot. Not all cars can use either the TPS or MAP AE systems or a blend. Read up on the issue in the MegaManual for your application.

David

[bcal]

What would you do

This (you'll need to log in for the pic)
http://www.msefi.com/viewtopic.php?t=13335
With the air cleaner on no-one can pick it.

I had the same dilemma and chose to go this way for looks, simplicity and cost.
Am very happy with the end result.

[snillet]

On thing is tricky with TB injection though, especially on my car.

Have Magneti Marelli G5 S0 system as "stock" and i´m using that TB with Msns-e right now.

So, it´s like this:

The PWM idle air control takes air from the air filter box and puts into the manifold. So far so well, but the injector is in the throttle body....

Anyone staring to follow the problem here ? , yes...when the PWM valve opens it passes intake air OUTSIDE the injector..... which makes the A/F mixture VERY weird as soon as the PWM valve opens. The stock injection HAVE problems with keeping this running ok.

Do i have to mention i´ve found it a Horses a.. ,to make it work ok together with closed loop ego correction ?

So i´m planning the solution to THAT problem to just ignore the factory TBI setup and use the throttle stop screw to adjust a basic idle speed and let the PWM valve stay SHUT at warm engine and idle.

Further down the road i´ll switch to port injection and that problem wount be no more.

[65looter]

I am going for port injected so a TBI is no what I need.

I am torned between converting an old carb I have or getting that throttle body from auto-nomics.

[bcal]

I am torned between converting an old carb I have or getting that throttle body from auto-nomics.

Or use a TBI unit without the injector pod and fuel reg. $50 from ebay and for that you also get IAC and TPS and you can use a stock air cleaner. What more could you want.

Not worth gutting out an old carb IMO. Too many ports to plug, things to adapt and venturies to remove.

[65looter]

choice has been made now: a TB from auto-nomics.