General (read dumb) ? about a MPFI system.

5

59flatbedford

Well-known member
ok so im new here but figured id jump right in and get started. so im going to build a 300 that i have out of a 79 ford f250. I want to build a multi port fuel injection system for it using megasquirt electronics and a mix of other custom parts. so im still pretty new to the EFI stuff so im still researching and have some questions.

Ok from what ive read the megasquirt systems are set up to use map sensors (right?) which according to fordfuelinjection.com is ran off the temp and rpm so obviously i will need sensors for that, and from the megasquirt manual they have a list of sensors and components i will need.
1. coolant and air temp sensors(what kind do i need and where are good places to mount them on the 300?)
2.oxygen sensor (In the exhaust pipe right?)
3.wiring and connectors
4.Intake manifold(How do the stock one flow? I was thinking of making my own just for fun(Any ideals welcome)
5.Injectors(about 21# or so right?)
6.throttle body(what a good size to get and what ones work good?)
7.hp fuel pump and lines and stuff(how many gallon an hour and what pressure (close to 45#?))
8.fuel pressure regulator

Well thats most of the questions im educated enough to ask right now but any useful info is welcome and ill keep researching so i can ask a little more intelligent questions.
 
Easiest thing for a 300 would be to get an intake from one that had factory injection. You could then use all the original ford sensors if you wanted to. The megasquirt manual lists part numbers for GM sensors just because they are cheap, readily available, and reliable. You can pretty much calibrate the MS to work with anything. Building an intake would be cool but I think for a first project most people would be better off working with as many known and proven parts as possible. After you get the hang of stuff you can then start getting into the unique custom stuff. If you are building a new motor you for sure dont want to start it up and do the break in on a un proven fuel system. If you start with a known running engine and a known working intake/ throttle body / injector setup and it dont run you know its something in your implementation of the Megasquirt. If you did custom and new on everything and it does not work you will have too many places to look for problems. Megasquirt is not plug and play. There is quite a learning curve but in the end you will understand what you have and know how to tune it. That experience will give you a great base of knowledge for your next more custom build. Get the MS and put it on an extra car or truck that you dont have to depend on to get to work just to get the hang of the system.
 
yea i had thought about the problem of break in on a unsure fuel system. I might just throw a factory carb intake and rebuilt carb as i know those would work for the break in (20 min at 2000rpm?) then once i do that i can go about figuring out the EFI. I was also thinking if i could find a throttle body that contained all the sensors i could adapt it to a aftermarket 2barrel carb intake and then drill and bung the runners. I have heard of this before but how well would it work.
 
59flatbedford":1fx9cdnz said:
ok so im new here but figured id jump right in and get started. so im going to build a 300 that i have out of a 79 ford f250. I want to build a multi port fuel injection system for it using megasquirt electronics and a mix of other custom parts. so im still pretty new to the EFI stuff so im still researching and have some questions.

Ok from what ive read the megasquirt systems are set up to use map sensors (right?) which according to fordfuelinjection.com is ran off the temp and rpm so obviously i will need sensors for that, and from the megasquirt manual they have a list of sensors and components i will need.
1. coolant and air temp sensors(what kind do i need and where are good places to mount them on the 300?)
2.oxygen sensor (In the exhaust pipe right?)
3.wiring and connectors
4.Intake manifold(How do the stock one flow? I was thinking of making my own just for fun(Any ideals welcome)
5.Injectors(about 21# or so right?)
6.throttle body(what a good size to get and what ones work good?)
7.hp fuel pump and lines and stuff(how many gallon an hour and what pressure (close to 45#?))
8.fuel pressure regulator

Well thats most of the questions im educated enough to ask right now but any useful info is welcome and ill keep researching so i can ask a little more intelligent questions.
Click to expand...

1. Coolant sensor, either drill and tap the T-stat housing or use your stock one. I'm pretty sure you can just tap into it and it won't affect it. IAT sensor goes in the intake tract. You can probably just leave it hanging.

2. Exhaust pipe, at least a foot from the manifold to protect it from heat.

3. Custom. For megasquirt, I recommend building the relay board as well, because it provides an easy place to hook things up.

4. Stock one will work, along with the throttle bodies. Or a TBI from a mid 80's 3.8 or non-HO 5.0.

5. That's a good place to start for a stock engine. I believe they have 19# stock, but I could be wrong. The stock injectors are barely adequate.

6. The TB from a 5.0, 5.8, 3.8, 4.0 will all be fine. They'll supply more air than you can use.

7-8. I have a BBK inline pump that flows 255lph, enough for 500 hp. It cost $40 on ebay. You'll need an external regulator unless you use a TBI, then they are integral. Holley, BBK, Vortech, Aeromotive all make good quality adjustable regulators. You'll have to calculate the fuelling demands and flow rate of your injectors at a certain psi to know what you should set the FPR at.
 
2. Exhaust pipe, at least a foot from the manifold to protect it from heat.

i mounted mine in the center of the exhaust manifold in one of the emission holes.i know gm mounts them in the exhaust manifold on thier v8s.do i need to move mine into the pipe?
 
hey thanks for the info that helps a lot. so do i only need one o2 sensor for the megasquirt system? the stock one uses two or three dont it? Im planning on building the megasquirt myself so ill go ahead and do the relay board. Now i have a really big question, What megasquirt system would fill my needs, Im want to control both fuel and spark and it would be nice to have a little room for expansion if i ever decide i wanna make it all sort of complicated. So does this mean that the MS-2 V3.0 would be the best kit to get and assemble?
 
The newer style T-stats have a coolant port in them, so I purchased one to eliminate putting the sensor inline the heater hose outlet. The problem is that the port is BEFORE the t-stat and it won't warm up until the t-stat opens up causing the engine to run poorly until the t-stat opens up. I found the best way is to adapt some pipe fitting with a T fitting in the heater hose outlet from the cylinder head on the t-stat.

The stock injectors are 13# lb/hr, but the stock Ford regulator runs 58 psi instead of the standard 40 that all the V8's run, so that runs the throughput of the injectors back up to 19 or so. The stock ford regulator and fuel rail with lower intake plenum works well.

If you want an adjustable fuel pressure regulator, a nice clean way to install one from an older 5.0L engine with 2 bolt mount is the get the 300 fuel rail with the 2 bolt regulator. I think it was the later one, but not sure. They made a 2 bolt and a 3 bolt. You have to elongate the holes of the aftermarket regulator to fit the stock fuel rail, but it works nicely with the original bolts.

If you get the stock intake stuff, get the throttle cable and bracket as well for easy cable setup. Even possibly the stock air cleaner assembly with hoses if you want since finding a Y pipe to adapt a single to dual 2 inch to the throttle body is kinda hard to find. K&N makes a kit wit ha Y pipe and filter if you want. The stocker works just fine though.

Only one will be fine, but MS is capable of 2. They tell you how to setup 2 somewhere.

Yes, the MSII V3.0 is the one you want. You can run the fuel first if you want (recommended), then run the ignition after you get the fuel dialed in on the distributor setup. There is probably more room than you need for expansion. They have I/O CAN capabilities for turning on electric fans among other things. It will handle just about anything you throw at it, except for advanced diagnostic capabilities.

I have actually been running my O2 sensor through the holes in the manifold without a problem yet. I'm testing it to see how well it works. So far no problems. We will see how long it lasts though.
 
For O2 sensors it depends on the sensor you use. The GM 1 wire sensors are narrow band and have to be close to the manifold to stay warm and work. There are narrow band sensors that are heated and those can be anywhere in the system before the cat. The wide bands tend to be heated so they can also be anywhere. You also want them pointed down so if they get condensation on them it will drip off rather than drip into it.

If you have a known working carb system I would get it broke in and even drive it a bit on that to make sure its all good then do the swap. If you are going wideband get that on there two so you get used to that and get a feel for what the readings should be vs. your perception of power and drivability. I wish I would have done that with mine. I ended up putting the wideband on another car for a few weeks to get an idea what I was trying to tune for.

Another tip that would have saved me many hours of frustration: At first ignore the O2 sensor readings, miss fires mess up the readings . Just tune by feel and ear. Get the engine to idle smooth. Get it to rev smooth. If you are not sure error on the rich side (especially on a new motor). Pop it in gear with foot on the brake and see if it feels like it has some power. If it does then take it for a careful ride around the block and if it basically runs then you should be able to start looking at the readings.

If you are used to doing circuit board repairs on fairly recent stuff building one will be no problem. If you got the Weller gun and fixed a lamp cord yourself you may have a problem. I would recommend buying the stim and building that first before you order the MS2. The stim has the 37 pin connector and a couple of transistors that are as small and close together as it gets on the MS. If you build that and think it was easy then you may be fine with the MS. If you thought that was hard dont even think about trying the MS board. If you are building yourself the Stim should be required so you can do the step by step tests. Its also handy after its built to test new setups or narrow down issues in the car vs. ecu. I likely average having to make one repair to some sort of circuit board a week for my day job so I solder more than most people and have an assortment of tools. Back in the 70's I used to build a lot of electronics kits. I found the MS to be a bit of a challenge. Next one I will likely buy it built. Luckily mine worked first time and has been working for 3 years now. I did have a few workmanship issues in my harnesses. Im not saying you will have problems two, just throwing out there what my experience level is with electronics and what I thought of the project.
 
well i have built one circuit board from a kit before and i can solder good. Im not to worried about building the thing as even if it is challengeing thats what makes it fun for me. I enjoy trying new projects and seeing what i can do and i would like to learn more about circuit boards, also im a cheapo and refuse to pay someone else for something i could build. Thanks for the info and keep any pertinent info coming.
 
59flatbedford":1o6k3pn0 said:
hey thanks for the info that helps a lot. so do i only need one o2 sensor for the megasquirt system? the stock one uses two or three dont it? Im planning on building the megasquirt myself so ill go ahead and do the relay board. Now i have a really big question, What megasquirt system would fill my needs, Im want to control both fuel and spark and it would be nice to have a little room for expansion if i ever decide i wanna make it all sort of complicated. So does this mean that the MS-2 V3.0 would be the best kit to get and assemble?
Click to expand...


Stock system uses O2 sensors in two places to check for catalytic efficiency. MS only needs one. I recommend wideband, they are more expensive but well-worth it in the amount of data they offer vs. a narrowband. It's like the difference between a stock oil pressure gauge and an aftermarket mechanical one.

I have the 3.0 board, but I bought it assembled 'cause I wanted the 3.57 board with SMT, and they are pretty much impossible to solder at home.
 
ok so ill make sure and get a wide band o2 sensor and mount it down the pipe a ways. So right now my shopping list is as follows.
Megasquirt 2-3.0 kit
Megasquirt relay board
magasquirt stimulator (for testing my work)
custom wiring and plugs,(where can i get factory style plugs to make the wiring look good and clean)
injectors(21-23#)
both intakes off a EFI 300
throttle body (probably just stock three hundred(it will flow enough for some performance right)
Stock replacement sensors(how accurate are these)
Fuel pump and system(and a regulator(about what psi should i run))
well thats all i can think of right now but im sure im forgetting stuff so chime in and remind me lol.
 
so did you just get all the sensor plugs and connected wiring and run it straight to the relay board (it just has screw connectors right?) ill make sure and get that stuff then. and one more thing to add to the list is the wiring between the megasquirt and the relay board. and a tuning cable.
 
I made the cable to go between the relay board and main box, and the data cable is a regular console cable with two DB9 ends.

I realize that not everybody has access to pin crimpers and 12-pair cable, though 8). It's just a straight-through DB25. Buy it from diyautotune or a wiring company.
 
Yes the sensor connections to the relay board are screw terminals. Its a 37 pin connector between the main board and relay board. If you have room to get the connector through the firewall I would just buy the connector made up. DIY also sells a bundle of wire that is labeled if you want to make your under hood harness. I was thinking of using that next time because most of us can only afford so many colors and eventually things get confusing.

If you buy sensors from DIY they come with connectors. I think they also sell some of the other connectors. Napa lists most of them also.
 
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