I work on very complex fuel systems for a living. For fun I enjoy building EFI systems for myself and clients. I have had some inquiries about how to DIY a system. So here anre some pics and a few words... I'll break it down for those not up to speed.

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You will see my current project. Don't worry about the wiring. It's still in test phase and I have a shorter harness I'm working on.
This is a TBI (Throttle Body Injection system. The easyest way by far to add EFI to your engine.
Here's a list of sensors needed for most EFI setups...
TPS (Throttle Position Sensor) The TPS measures how far open your throttle is. 1-5 volts in mots cases.
MAP (Manifold Absolute Pressure sensor) Measures manifold vacuum 1-5 volts.
AIT (Air Intake Temp sensor) Measures intake ait temp. Used for TPI or sequencial systems. Not needed for TBI.
Water Temp. Most aftermarket system use a GM sensor.
O2 sensor (measures the ammount of oxygen in the burned exhaust. ECU will adjust fuel level based on this signal)
Oil Pressure Switch. Some systems like the TBI use this switch to shut off fuel with a loss of oil pressure.
MAF (Mass Air Flow sensor) Measures the amount of air going into the engine. Used on high performance systems.
Crank Trigger. Used by the ECU to determine engine speed and adjust the fuel map to suit the engine requirements.
Cam Trigger. Used buy the ECU for a sequencial injection system.
ECU (Electronic Control Unit, the brain of the system)

The TBI system has the injectors mounted in the throttle body on top of the engine. It mounts similar to a carb. These systems can be used on a stock manifold with the correct adapter flange. The TBI is for a mild cam setup but the ECU can be re-flashed for more performance. In the picture above is a Crossfire Injection system from an 80's Corvette. It uses two 400 CFM TB's instead of one. I had to down size the injectors for my 283. The GM computer will learn how the car drives and re-write the fuel map to suit the engine (Closed Loop) using the engine sensors as a referance. During warm up and WOT, the system will run in "Open Loop" mode and use engine speed and TPS signal to adjust the fuel map. This system was used and purchased from Ebay. Total installed price $500.

A sequencial injection system uses both the Crank and Cam signals to determine when each cylinder is at its intake stroke. The injector will fire only during this point of the cycle. A sequencial system has better off idle performance and slightly better fuel economy. The two most common ways to access a Cam signal are to use an Accel Dizzy with a cam output or machine a magnet into the cam gear to use an inductive pickup on the timing cover.


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This Picture Is a sequencial system using a F.A.S.T. ECU, GM sensors, Ford dual throttle bodies and Bosch Injectors. For This setup everything was custom fabricated. I used a dual quad manifold and welded injector bungs to it. This system was all new parts. Total installed price $4000. Plus dozens of days of seat time with my lap top writing fuel maps.

I've also used Megasquirt with great results. MS has a great fourm with helpful people just like this site. MS does not need a cam signal because it does not do sequencial injection. MS uses "Bank to Bank" injection. This means to toggles between the right and left cylinders back and forth. There will be slightly lesss performance at low RPM's but at mid to high rpm the difference is neglegable. The really nice thing about the MS forum is that there will be someonr there with a setup similar to yours and they will share their fuel maps. You then use their map as the starting point for yours.

Most aftermarket EFI systems will allow the use of a wide band O2 sensor. A wide band O2 will allow you to run in Closed Loop mode and have the ECU learn how you drive in conjunction with the engine needs. This makes fine tuning of the system very easy.

Most early GM EFI systems can be adapted to any engine. You just need the GM sensors and wire it up correctly. Factory EFI systems are really cheap at junk yards or on the web. Make sure you buy a system as complete as possible. Painless Wiring makes harnesses for most GM and Ford systems.

I hope this helps people understand a little about EFI.

If I missed anything please chime in. Correct me if I made any mistakes.

Bottom line... EFI is easy. Everyone should do it!

Glad to see an Electrician on this site, my father was less electroincs but a union local president.. I bet you can build a crazy audio system for the 914 in your sleep..

IBEW Local 595

I've done a few stereo's in my time. I'm a former IASCA judge (International Auto Sound Challenge Association)

Cool, looks like the '82 corvette cross fire injection. And there are quite a few of us on here running megasquirt 1 and 2. My brother does a lot of tuned port stuff in dallas for show cars. I love FI !

Great reading. THX. A good terminology reference for FI imbeciles such as myself. You know what would be neat? An DIY article on which GM junkyard FI fits our basic T4's e.g. 1.7, 1.8, 2.0 and a step by step article on how to install and dial one of these units in. With our antiquated FI systems wearing out every day, we would enshrine you. Especially if we coud do this on the cheap!

Can be done for less than a set of new carbs, but you would really need to DIY. My install cost me less than 300 for the megasquirt. I was able to get free sensors though. If you did a real diy and bought new sensors, still less than 500. DIY injection is not for people that don't like to tinker or learn. If your in the latter group, pay someone like kg6dxn to do it!

If I had a T4 engine, I could do it. The best EFI to use would be a TBI setup and operate it as a bank to bank system. Connecting the TBI's injector outputs to the T4's injectors. It's been a while since I had an air cooled engine. not sure what the oil temp is at operating temperature. If it is around 190, the GM water temp sensor could be taped into the bottom of the block in the oil sump. A TPS cam would need to be fabbed on the throttle body. any 3 wire TPS that would fit would work.
If we were crazy enough to run Nitrous Oxide, the ECU can be programmed to increase fuel delivery automatically. And... if you run a spark controller with the ECU, it can retard the timing at the same time. I love technology.

oil temps around 225, but thats not what you want to monitor. Its head temp, the oil takes way to long to come up to temp, so you would be in cold start mode too long.

I was able to use stock plenum, and TB (new 53MM GM waiting to go in) with stock injectors and head temp sensor. What I got was...

MS2 V3.0 diy kit in black 254.00
GM throttle position sensor, modified throttle body shaft to accept it. about 30.00
GM air temp sensor about 12.00
Universal 4 wire heated Bosch O2 sensor about 55.00
Welded in O2 sensor bung 8.00

Lots of wire or buy the harness available for the MS about 50.00

This is all fuel only, ignition requires a little more work, but not terrible. If you want to go crank trigger with a coil pack that adds more $$$


What does all this do for you?
No more antique map/pressure sensor
No more expensive throttle position switches
No more expensive trigger points
Modern programable ECU that you can test/monitor/tune through your laptop

Here is he big one though. My time in assembling the MS2 8 or so hours
Wire harness fab 4 hours
sensor fitment/adaptation 5 hours
tuning first start up 2 hours

READING THE MEGAMANUAL 30+hours !

Keep in mind I make full CNC panels and do board level repair at work, so i'm probably a little faster than most.

[quote

Keep in mind I make full CNC panels and do board level repair at work, so i'm probably a little faster than most.
[/quote]

I'm a licensed FCC technician, went through solder school, electronics school etc, etc...
I used to build the MS myself but now I pay a little more and have one built for me. I do the board mods myself. Like MAF and WB O2.

I just don't have the time or paitence to solder all that crap anymore.

[quote name='kg6dxn' date='Jan 27 2010, 09:29 PM' post='1266545']
[quote

Keep in mind I make full CNC panels and do board level repair at work, so i'm probably a little faster than most.
[/quote]

I'm a licensed FCC technician, went through solder school, electronics school etc, etc...
I used to build the MS myself but now I pay a little more and have one built for me. I do the board mods myself. Like MAF and WB O2.

I just don't have the time or paitence to solder all that crap anymore.
[/quote]


I don't blame you ! For a one time thing it was kinda fun, but not more than one !

I like that, but TBI is obsolete since you can get a batch fire system so cheap now, especially for a fuelie type IV.

Really, with gas where it is and going higher, I would only do sequential stuff from now on.

Batch sucks ass too when you hit the injector wall, it is hard getting large injectors to do well on batch systems, then there is wasted fuel, more oil changes more often due to gas contaminated oil which can wipe rings, etc etc.

[quote name='kg6dxn' date='Jan 27 2010, 09:29 PM' post='1266545']
[quote

Keep in mind I make full CNC panels and do board level repair at work, so i'm probably a little faster than most.
[/quote]

I'm a licensed FCC technician, went through solder school, electronics school etc, etc...
I used to build the MS myself but now I pay a little more and have one built for me. I do the board mods myself. Like MAF and WB O2.

I just don't have the time or paitence to solder all that crap anymore.
[/quote]


[quote name='underthetire' date='Jan 27 2010, 09:50 PM' post='1266559']
[quote name='kg6dxn' date='Jan 27 2010, 09:29 PM' post='1266545']
[quote

Keep in mind I make full CNC panels and do board level repair at work, so i'm probably a little faster than most.
[/quote]

I'm a licensed FCC technician, went through solder school, electronics school etc, etc...
I used to build the MS myself but now I pay a little more and have one built for me. I do the board mods myself. Like MAF and WB O2.

I just don't have the time or paitence to solder all that crap anymore.
[/quote]


I don't blame you ! For a one time thing it was kinda fun, but not more than one !
[/quote]


Can either one of you guy's do trouble shooting?

I am having a prob. with my MS not switching the fast idle selonoid on and off.

TBI on a 914 engine (in my opinion) is not practical due to the fact that they where injected from the factory. parts are easily obtainable.

Although, a MS retro fit is a great solution for the aging stock parts.

I love FI and messing around with the MS system. I did a full retorofit with crank fire using Ford escort parts.

Soon I will be converting a 32hp twin cylinder engine from carbs to FI. I'm going to use microsquirt for the controller.

Is it drivable yet? If you are using a fast idle solenoid not the stock aar valve, then it would have to be one of the aux ports on the ECU. I can meet you at work next week. Should be at 801 if you know what I mean.

I agree there are better systems to ues as a custom 914 replacement.

The challenge was to use a GM junk yard EFI system. A TBI ECU can be used to batch fire the 14's injectors. I was not thinking of using the TBI's throttle body, just the injector outputs. If the impedance is high enough on the 914 injectors, you can simply use two per TBI injector output. Mainly you would need the ECU and harness from the junk yard. A few misc sensors too.

Sequencial is a little tricky for any custom setup due to the need of a cam signal to sync the injector fire. The 914 dizzy does not sync with the intake valves opening. It only give an on/off signal the the ECU that matches mechanical engine speed.

I'm rather new to the whole custom EFI relm and am still in the tuning phase of an MS2 w/ EDIS conversion, so please excuse the possibly dumb questions. . .

If you're running a crank fired ignition like EDIS, where you would normally omit the dizzy and plug the hole, why could you not use the un-used ignition points (not the trigger points for the D-jet EFI) as your cam position sensor?? The rotor can be positioned in any position by moving the drive gear, underneath it, a tooth or two back and then fine tune the exact moment of fire like you would when setting the timing on a motor. . . You would effectively have now a sensor that gives you one pulse per intake opening event that is tunable (well in my mind anyway ).

Does that sound like a possible solution or have I just sniffed too much fuel??

Very cool

I look forward to doing this to my corvair engine some day I was thinking CIS, but I like to program.

I'm thinking you should weld some injector bungs on and use a Ford 5.0 Throttle body in place of that carb. If you look at my dual throttle body pic you will see a 90 degree adapter to go from a 4 barrel manifold to the 5.0 TB. They cost about $50 each. I would also recomend a lamda wide band O2 so you can have the system fine toue you fuel map automatically. Having the engine run at stoich at all rpms is amazing. ..vroom

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I currently have a WB O2 sensor setup for the electrically adjustable jet kit in the 390cfm carb. Would a 5.0 part not be too big for my 3.1L engine?

The size of the throttle body does not matter as long as the fuel mixture is stoich. If you use one that is too small, you will have performance problems. I could fab four 50mm TB's, one to each cylinder as long as I size the injector and pulse width correctly.

So you think I could put together a good working EFI system for my 305 SBC for around $500? Vortec Heads, roller rockers, mild cam, Eldebrock torquer manifold.

So what should I look for at the junkyard?
Interested in putting together a plugnplay system if I scrounge the parts?

The easyest way will be a TBI from a 1990's GM truck. Almost all of them had TBI. It is not the most high end FI system but it is much better than a carb. Remove the Dizzy, intake and components. Find the ECU onder the dash take it and the harness.(usually right side kick panel) remove ALL engine electronics. Such as: MAP sensor, Spark control, any thing attached to the ECU. The ECU will have other wires to it: Fuel pump output power, starter input signal, battery 12V+, ground, ignition and maybe a transmission input and a VSS (vehicle speed sensor). The transmission input will be from the neutral safety switch. There is also a brake light input. ONLY the stuff in the engine bay will you need. You will also need a water temp sensor and oil pressure switch. These will be on the engine. finally you will need the O2 sensor. for this, buy a new one. It is a single wire O2 sensor and new ones are about $20. You will need a bung on your exhaust collector (right or left) Bungs are about $7 plus welding.

If you butcher the harness, Painless Preformance has them available. Not all wiring is required to run the system. VSS is not needed but can make it run "cleaner" and is required for smog. The Tranny stuff should be left disconnected. The fuel pump output wires go to a relay and not directly to the pump. Painless also has wiring diagrams to help you.

If anyone wants some PDF's with wiring info just PM me.

Actually, i disagree here. Too big of throttle body can make driving difficult. If your on and off the gas, fine. Too big tends to make constant throttle hard to maintain, as it get very snappy and violent with a manual trans.

Lets take my 283 FI conversion.

If I were picking a carb I would calculate like this...

CFM=CIDxRPMxVE/3456

CID=283
RPM=max 6000
VE=Volumetric Efficiency 80% (maybe, mild cam, 9.5 comp ratio)

This calculates to a max CFM of 393

So I would look for a carb around 400CFM to be a match for this engine.

The TB setup has dual 400's. 800CFM total. Twice what this engine should need. with the fuel ratio matched to the air this engine runs great. Cruising at speed with little throttle input creates no surging or jerking. If I were to double the CFM again it is concievable that surging could accur. This can be compensated for by "camming" the throttle. Similar to the throttle cam on the 944. This would be done to make the throttle pedal action Non Linear. So at crusing, the pedal opens slightly, when the pedal is pushed to the WOT position the throttle will open at an exponential rate. instead of a 1 to 1 ratio on a linear pedal. No matter how large the throttle body is, the engine is limited mechanically to how much air it can take in.

Very interesting

Thanks for the ideas and tips. I'll have to take a trip to the local pick a part and see how available a mostly complete 90's truck EFI system would be and how much they would want....just for a starting point. I know last summer I read and read about adding FI on my motor and the more I did, the more I realized I needed help.

Originally, I thought I was going to get a TPI system off a vette or camaro, but later found because of my Vortec heads, it became much more complicated of an adventure...and costly.

Then I started looking at the TBI systems from Holley. It appeared new plug and play complete kits were around $1100. Their systems appealed to me because they had directions and would be tailored for my motor (somewhat). I just couldn't get myself to spend that kind of money when my car runs great as it is and gets 24mpg on the highway, which isn't too bad. Anyway, not really understanding all the parts well enough, I didn't feel confident enough to purchase used systems or go to the junk yard and pull a system. Heck, I 'm not entirely sure I could find all the related parts you have mentioned that I would need. It would be like "looking for waldo." Anyone have a "looking for waldo" book but with pictures of what all the EFI parts looks like and where their normally located?

Here is a site showing a GM EFI on a Corvair engine:
http://www.corvairnut.com/corvairTBI.htm

Bad ass, Jacob! Thanks