TBI Thoughts

That's a great price, if you can do it. You can hardly buy the material for that much.

 

I will be jumping ALL over this when finished!! Might be a good winter project...

 

Maybe there is enough technical content here that the mods would like to move it to the early CJ-5 forum? (and avoid the automatic thread extinction here?)

 

My bad on terminology, thanks for informing. I believe the word I was looking for was dual port, the intake manifold that you can bolt a four barrel to..


lots of stuff to research before even thinking about adapting TBI.

 

Let's see a pic of the 3.7L throttle body. Any throttle body should work, as long as the injectors can deliver enough fuel for the amount of power the engine makes.

The main issues will be 1) idle air control (IAC). Different throttle bodies have different ways of controlling idle air (fast throttle) for engine warmup. The Rochester (GM) TB has a separate passage that is opened by moving a pintle in the TB. The Ford 3.8L TB has a stepper motor, but the 5.0L Ford TB uses a thermal/vacuum system. You'll need to analyze what your TB has and adapt the Megasquirt programming to accommodate your TB. 2) throttle position sensor (TPS) - this is basically a potentiometer attached to the throttle shaft. Different TBs could have different ranges of resistance. Measure and adapt the programming. 3) injector size - measured in lbs of fuel per hour (pph) typically. The injector is an on-off device, and pulse width modulated (PWM). The higher the rating, the shorter the open time for a given amount of fuel. Theoretically you could use Mike's fuel maps for the 4.3L TB (2 x 45 pph) if you change the scaling of the maps to match your injector sizes. 4) fuel pressure regulator - typically there is a fuel pressure regulator on the throttle body. Changing the fuel pressure changes the pph rating of the injectors.

That's pretty much it for the throttle body. There are other inputs to the computer (MAP, air temp, coolant temp, spark control, knock sensor) but they do not involve fuel delivery.

 

I am very interested if it can easily be done. I have yet to see anyone come up with a setup that beats a Holley 8007 390 cfm carb on a dual-plane intake-for less then $1500. Very hard to justify $1500-2000 on a fuel delivery system on a Jeep that is typically is worth $2500.

 

Suspected that, after I wrote about 100 words.

Fortunately the words come easy on a topic like this.

Apparently there was TBI on the 318 and 360 back around 1989. Few references to it though.

 

You need to orient the bung so there is room for the O2 sensor, and so that exhaust condensate (water) does not collect on the end of the O2 sensor. So ideally pointing up, but sideways if there is no room.

This is the GM narrow band O2 sensor -



Larger picture - https://www.nmr.mgh.harvard.edu/~reese/O2sensorLarge.jpg

This is the narrow band sensor that GM cars and trucks use. You can buy the pigtail shown here from Standard to neatly tie the sensor in to your wiring. Supposedly it's a M18 thread, and you should thread a bolt into the bung while its welded so it won't warp. Supposedly you can cut down a non-fouler and that will work. Then plug it with a spark plug? http://www.dormanproducts.com/p-15635-42009.aspx?origin=keyword

Note that it's harder to tune with the narrow band sensor (vs an aftermarket wide ban sensor) but the narrow band sensor is way less expensive, and if you are going to use Mike's fuel maps, you shouldn't need the ranging of the aftermarket sensor to determine a map.

 

Mike I'm running a GM TBI on my 67 225 at first I built an aluminum adapter like Tim's for the stock 2bl intake but ended up picking up an Offy dual plane intake and made a steel adapter, it runs great with the Offy intake. Never used the stock intake but there is no reason why it should not work. just my opinion I like aluminum for the adapter. Good luck

 

The GM 1 wire o2 sensor as you noted are relatively inexpensive and are quite reliable. If you are installing the sensor on a vehicle with headers or locating the sensor quite a ways down stream of the exhaust manifold, a better choice is a 3 or 4 wire heated narrow band sensor. With a heated sensor, the system will go into closed loop much quicker which can help with fuel economy. If you are doing any wide open throttle (WOT) tuning you are generally consider to be a fool if not using a wideband sensor. A narrowband sensor and WOT tuning can be a fast track to a melted mess.

 

No issue with the stock 2 barrel manifold. I built one using 6061 a Dremel and hand drill. Works fine. If I remember right I blocked off the heater tube passages. I can send you a basic tune if you like with all the parameters as my setup uses the 4.3 with stock injectors. Ryan

 

Good to see you on this thread, Ryan. I thought you'd fallen off the planet.

 

The difference between using a wideband o2 sensor and a narrow band o2 sensor for tuning is huge. Wideband sensors tell you exactly what your fuel richness/ratio is and a narrow band only tells if the fuel ratio is either above or below 14.7(complete fuel burn). It is possible to tune with a narrow band, but much easier for first timers with a wideband. I use an LC-1 which 5plus years ago was around $200, there is more wiring involved in addition to the megasquirt fuel injection wiring. For those of you who will be tuning the 225, it likes a rich idle at 12-12.5.