924Board.org

kaffine · Joined: 13 Jun 2003 Posts: 644 Location: Las Vegas

Well I'm getting tiered of breaking fuel lines every time I work on the engine so I'm thinking of switching over to EFI.

If you have converted over to EFI what system are you using? What are you using for TPS and CPS? Did you use a fuel rail from another car or make your own? Thanks.
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80 924
80 931

The best desciption of an atom boils down to something unknown is doing we don't know what.
Sir Arthur Eddington

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

The megasquirt DIY seems like the best way to go. Couldn't be too tough (yeah right!). I presume the basic setup would be to use a manifold air flow (MAF) sensor, electronic injectors (obviously), and the computer to control the injectors. That's the basic circuit at least, then you need temp sensors, throttle position sensors, lower pressure fuel pump, etc. I'd love to see someone go through with it.

-nick

Racing · Joined: 27 Apr 2004 Posts: 374

Have converted more engines over the yrs then i care to remember.

The Mega comes with a MAP built in(on circuit board)
TPS is normally of the Ford variety,cheapest i know of to pick those up is Haltech-even cheaper than Ford these days.

Then you need an IAT and well as a coolant sensor.
More often then not these are GM.

Conns for injectors are OEM Bosch.

Most of this can be found at your local scrap yard.

As far as hardline for the 924 engine..dunno...i for one would check one out for a Volvo 4 cyl.
Also a fairly "large" 4 banger.

When it comes to system pressure regulator,just be easy and cheap and use the one already on the hardline.

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

I fired mine on Mega Squirt a couple weeks ago. I haven't had time to finish tuning but so far I am VERY pleased. Throttle response is excellent and full throttle power is much better. As far as simplicity goes, it all depends on your abilities. I don't pretend to be a master fabicator but I do have a few tools so overall it wasn't difficult but it was definitly time consuming. I ended up building my own fuel rail from 3\4" square tubing. I tried several other approaches before going this route. I also machined inserts to mount the injectors in the head so I didn't have to build an intake with bungs. Mounting the rail so it held the injectors tight was a little difficult also. Building the MS controler and relay box was more fun than difficult. I never did anything like it before and it was very gratifing to hear the engine actually fire up! I probably have about $400 or so wrapped up in the whole thing including the laptop to program it with. It was much more involved than I first figured but it seems to be working out well. Now I'll be ready to mount up my "freebie" Whipplecharger next year!

Todd

Lizard · Posted: Sun Jul 11, 2004 5:27 am Post subject:

Hey Todd, you are saying that in parts you have only spent about $400, where did you find those parts and what prices?
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3 928s,

kaffine · Joined: 13 Jun 2003 Posts: 644 Location: Las Vegas

How did you connect the TPS to the throttle? Thanks.
_________________
80 924
80 931

The best desciption of an atom boils down to something unknown is doing we don't know what.
Sir Arthur Eddington

Lizard · Posted: Sun Jul 11, 2004 1:40 pm Post subject:

Kaffine he probably attached by the use of an adapter plate a ford 5.0L throttle body and used its factory TPS
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3 928s,

u000533 · Joined: 30 Sep 2003 Posts: 17 Location: Bristol, UK

Todd, any chance of some photos of the installation, just discovered the megasquirt site and really interested to see how it all fits together under the hood.

regards

Mike.
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1981 931 turbo - sadly sold

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Just got back from a fishing\camping trip. Lizard, as far as parts used everything was used out of a couple different junk yards. My first intention was to convert to a turbo so pulled an entire setup off an early\mid 80's Mopar 2.2 from a station wagon. I used the injectors (27lbs) and the TPS from this ($75) The MS and relay board ($150) Laptop off E-bay ($75) Used IAT and ECT sensors ($15) Metal for fuel rail and misc. ($15) Wire, ties, solder, connectors etc. ($20) Cold air intake ($35) New O2 sensor ($30) OK, so this adds up to $415 plus there is some other stuff I am sure I haven't thought of so lets say $500 for the works.

Kaffine, as stated above I used the TPS from a Turbo 2.2 Mopar. This worked well but mounting it was one of the trickier things I had to do on this project. I used the stock throttlebody and it is mounted on the under side. Absolutely no room on the topside. I figured this one out the hard way!

I'll try to get some pictures put together within the next couple days. Like I said I can't seem to find time to even tune it and I plan to race an autocross on the 1st!

Todd

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Here is a quick shot of my engine with MS-EFI intalled. Note I still have a lot of cleanup and tikering to do yet. Should be a fairly clean setup when finished.

That electrical box on the left is actually a relay and fuse board, not the computer. It is in the cab mounted under the glovebox where I can watch the LED lights. I'll post some pictures of my TPS mount when I remove the throttle body to finish the mounting.

Todd

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Thought i'd post a better picture of the fuel rail. I gas welded everthing. this is before welding the mounting tabs wich were also a pain to locate.

Just for kicks this is the Mega Squirt "Kit"

A little daunting for a neophite like me

Todd

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

So what was involved in plotting the fuel maps?
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'81 931 in various states of assembly

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

The intructions for plotting your "fuel maps" are extremely detailed but quite confusing until you start actually doing it. Then it becomes much more intuitive. I started with the default values that come programmed in the chip for a hot late model Corvette 350 TPI. It actually started and ran on this!

MS uses "Volumetric Efficiancy" tables to plot the fuel curve. I still don't completly understand the concept but it will basically follow your torque curve if you should be so lucky as to have a dyno read-out. If you know (or can guess) your peak HP and torque rpm then you can use an on-line programm to plot a rough map. This is what I did. Worked pretty well. I then used the O2 sensor to get even closer. I did this on friday, so my next step is to download "MegaTweak" wich will help me fine tune the whole thing using data-logs.

Along with all this is a page full of "enrichments" you need to programm. Most of these are by the seat of your pants. Things like priming pulsewidth, acceleration tables, cold enrichment tables, O2 switching voltage etc. This all sounds a little complex and it is at first but I beleive I will be able to do my next one in 1\10th the time this took. If you are interested in looking at the software to tune go here:

http://autos.groups.yahoo.com/group/megasquirt/files/MegaTune/

You'll have to create a Yahoo account to get in but the whole thing is free including the tuning software. Just looking at it will answer a lot of questions.

Todd

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

I think I will give this a try on my 924, that way I'll be familiar with it when I want to swap in the KL... Speaking of that, looks like I've gotten my hands on a KL engine for free, so that project might be on the go sooner than I had planned.

So do you plot actual pulsewidth for the injectors, or does it automatically calculate the fuel delivery based on the volumetric efficiency?

Also, I see Megasquirt has set up forums

http://www.msefi.com/index.php?c=2
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'81 931 in various states of assembly

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Yes, It uses VE plus the size of your injectors plus RPM plus MAP load plus temp plus TPS plus several other things to calculate pulsewidth of the injectors. Most of these things are known upfront and only need to be inputed once. The VE table is your only unknown but can be roughly calculated with a few guesses. You use your O2 sensor input to plot your map. There are many tools available on the net to help with this.

I have mine pretty well roughed in and running well. I will continue to fine tune when I have a chance in order to increase my fuel milage plus fix a couple quirks.

Can't wait to see that engine swap. Sounds like it should be a very interesting endevor.

Todd