'75 EFI: Upgrade or not?

[Wolfman3002]

Hi,
I recently aquired an L-Jet EFI setup from a friends '75 Manta, and I have almost everything from the system, except for the distributor and the thermostat housing (which includes, of course, the sensors and Aux Air Valve). I have a source for the thermostat housing and sensors, thanks to Jim at USAOpel. This system is part of the pieces I'm collecting for a 2.0l engine build, hopefully for next summer (my budget and the US economy willing). But, as I was starting to take things apart, I found that the ECU circuit boards had a few components on them that were bad, including 2 resistors (that are corroded bad enough that I can't identify the values), and a transistor that looks like it may have blown (at least this one I think I can ID). So, my questions are these:

1. Is it worth it (and possible) to fix the ECU, and then get the stock system into running order, or will it be better to just trash the ECU, and go straight to a Megasquirt system?

2. If I do go w/ Megasquirt, will I still need the '75 Thermostat housing, or will the MS sensor requirements make it just as easy to keep my stock '73 thermostat housing? W/ the MS option, I plan on using a Nissan TB, and an aftermarket IAT sensor. I'm guessing I'll still need the '75 housing, for the cold start requirements, but I wanted to be sure before I bought one.

3. W/ the MS, can I get rid of the Air Flow Meter, and go straight from the Throttlebody to a cold air intake (probably a K&N cone filter)? If so, does MS have a way to handle the fuel pump shutoff, normally handled by the AFM, if it is removed?

I don't think these questions have been answered in previous threads, but I apologize if they already have been. I've spent hours nd hours using Search to try and learn as much as I can about the EFI system, to decide if I want to use EFI or carbs for my engine build, until my eyes were crossed.
My goal is to have a strong, streetable, reliable engine, w/ maybe 150HP, and I want to figure out if EFI can help me achieve it.
Randy

[guyopel]

All this depends if you are trying to get performance or just want the fuel injection sys.
The stock Opel fuel injection sys. was good for stock 1975
models but the injectors are not the best at todays standards nor is the fuel control with the Air Flow Meter if you do any performance work on your engine this sys. has it's limits .
HTH
John

[Wolfman3002]

John,
What I want out of an engine is solid performace for spirited driving in the twisties (the Pacific Coast Highway comes to mind). I don't so much care about top end speed, I mostly want to be able to put my foot into it at, say, 35-45MPH, and really feel the push. I guess that means low end torque?
I'm still in the planning stages, but the new engine will probably be something like this: 2.0l, 9.0:1 compression, ported head, a "Torquer" or "Combination" camshaft, EFI, Sprint manifold w/ 2" exhaust, Compufire ignition (this is already on my GT now and works great).
Randy

[jordan]

If you were to go with the megasquirt and you wanted to make full use of the system for tuning, economy and power a crank triggered ignition system cant be beat like the ford edis or some of the other hall effect systems.

[Wolfman3002]

Are the crank triggered ignitions very hard to set up?

[jordan]

Originally Posted by Wolfman3002 Are the crank triggered ignitions very hard to set up?

Not terribly difficult, I could not see any way around it without machining if that is a major draw back for you. I have some pictures of my set up in a thread somewhere, try searching for "ford edis" I know "markandson" "kma" "washout" along with myself have done this (my bracket is a copy of Gregg's) once it is all done it is definitely the way to go, you also lose the distributor so it makes a nice spot for a supercharger to go if that is the direction you're headed.

[wrench459]

Originally Posted by Wolfman3002 John, What I want out of an engine is solid performace for spirited driving in the twisties (the Pacific Coast Highway comes to mind). I don't so much care about top end speed, I mostly want to be able to put my foot into it at, say, 35-45MPH, and really feel the push. I guess that means low end torque? I'm still in the planning stages, but the new engine will probably be something like this: 2.0l, 9.0:1 compression, ported head, a "Torquer" or "Combination" camshaft, EFI, Sprint manifold w/ 2" exhaust, Compufire ignition (this is already on my GT now and works great). Randy

With the 95mm pistons you'll be pushing 9.7:1 Now thats seat of the pants power. All you'll need is the proper cam. The bad thing is you'll run out of air flow around the 115 gm/sec mark.

[Wolfman3002]

Originally Posted by wrench459 With the 95mm pistons you'll be pushing 9.7:1 Now thats seat of the pants power. All you'll need is the proper cam. The bad thing is you'll run out of air flow around the 115 gm/sec mark.

Wrench,
Does this airflow limitation have to do w/ either the stock throttlebody or the Air Flow Meter? If I go w/ the Megasquirt system, I'll use the slightly bigger Nissan Throttlebody (60mm vs 55mm for hte stock TB, I believe), and I'm hoping I can eliminate the Air Flow Meter altogether (if that's possible w/ the MS system).
Or, is the flow limitation a matter of valve size? I was also thinking about goping w/ the 2.0l valves to increase the breathing capability of the engine. Do you think that would help?
Randy

[RallyBob]

Originally Posted by Wolfman3002 Wrench, Does this airflow limitation have to do w/ either the stock throttlebody or the Air Flow Meter? If I go w/ the Megasquirt system, I'll use the slightly bigger Nissan Throttlebody (60mm vs 55mm for hte stock TB, I believe), and I'm hoping I can eliminate the Air Flow Meter altogether (if that's possible w/ the MS system). Or, is the flow limitation a matter of valve size? I was also thinking about goping w/ the 2.0l valves to increase the breathing capability of the engine. Do you think that would help? Randy

The air flow meter is the biggest limitation. Next would be the cylinder head and then the camshaft, then the intake manifold. But you needn't worry about the intake manifold until you're running a pretty honkin' big cam and only if you already have a very well ported big-valve head.

IMO, the best bang-for-the-buck in terms of building a big valve 1.9 head is to fit 2.2 intake valves (1.77") and 2.0 exhaust valves (1.42"). Opels have very good flowing exhaust ports in the stock configuration, it's the intake side that needs all the work. The nice part about using the factory Opel valves is it minimizes the amount of machine work and therefore $$$. Same size guides and you can use the stock springs and retainers, although for any decent cam you need better springs. Norris Cams has upgraded springs and I believe retainers as well. Simplifies the installation as there's no additional machining other than cutting the seats in the head larger.

You could also go with the tried and true Chevy valve installation, but this requires replacement of all the valvetrain parts and there is subsequently greater labor and machine work involved.

HTH,
Bob

[Wolfman3002]

Bob,
Thanks for the advice on the head upgrades. I probably will go w/ the 2.2l intake valves and the 2.0l exhaust valves. I don't want to go too wild on the cam, though, as I want to keep this thing a streetable, daily driver.
I can remove the AFM w/ the MS system, can't I? I believe the MS can accept just the tach, coolant and air temp and the TPS inputs, and it'll work fine?
Also, anyone have any answers for the questions in my first post of this thread?
Thanks all,
Randy

[Paul]

As an iriginal 75 FI owner, I can say the 75 FI CAN BE modifiied impressively. However there is a limit, but the limit, within the capabilities of the stock FI sytem, can still be quite impressive. With the proper head work, correct cam, etc, it will still HAUL ASS. I know it doesn' t sound like much, but100HP at the rear tires will suprise a lot more folks than you can amigine ...
I drive mine everyday, get great fuel milage and still dust off lots of folks that just can't bleieve a 70's ventage car just blew them off the road...

[markandson]

MegaSquirt ahh yes....after all is said and done, which I am not yet, the system is fantastic. My engine is beginning to purr and I am far from finishing tuning. Inlet Air Temp IAT, Coolant Temp CLT, Throttle Position TPS, Manifold Air Pressure MAP (this one is part of the MegaSquirt Board), Oxygen Sensor O2, EDIS4 with crank trigger (eliminates distributor) but you could leave the dizzy in, the beauty of taking it out is complete control over spark advance with the computer although I believe you could lock out the vacuum advance in the dizzy and get the same result. The EDIS system naturally also eliminates the rotor. I know the system very well at this point so I no longer have the "fear" that I had at the start. The most difficult part on the mechanical end is fitting the crank trigger wheel and its associated sensor. The EDIS system will run you about $400 in parts if you buy it new. You have to buy the coil, control module, VR sensor, 12 pin plug for the module and 3 pin plug for the coil, shielded wire for the signals between it and the MegaSquirt, Plug Wires, and the Trigger Wheel. I also had to build a small circuit board to run the tach. Good luck, I am a believer in MegaSquirt.

[Wolfman3002]

Boy, you guys can make a decision difficult. While I'm normally a traditionalist, and like to see what I can do w/ what I have on hand, I also don't mind upgrading if it makes sense.
I'd like to go w/ the EDIS ignition, but I may phase that in later, if possible.
I think I've learned that w/ Megasquirt, the thermo-time switch and the cold start injector are not needed, but I need an AAV or the Megasquirt solenoid equivalent. And I believe I don't need an AFM.
But what about the Thermostat housing? I know I need a CLT sensor, but could I just add one to the existing Thermostat housing?
Thanks, everyone, this is a great forum for fielding ideas.
Randy

[Gumby]

Hillsboro huh? You aren't too far away from me. I'm just down in Salem.

If you are willing to go to the expense a megasquirts setup is going to be better than the stock 75 EFI. Cranktriggers are awesome. If you need machining done for a custom setup let me know. If I can't do it myself I know the people who can.

When our cars are done we'll have do a comparison. I am interested in how a worked over 2.0 compares to a stock 2.4L.

[markandson]

Originally Posted by Wolfman3002 Boy, you guys can make a decision difficult. While I'm normally a traditionalist, and like to see what I can do w/ what I have on hand, I also don't mind upgrading if it makes sense. I'd like to go w/ the EDIS ignition, but I may phase that in later, if possible. I think I've learned that w/ Megasquirt, the thermo-time switch and the cold start injector are not needed, but I need an AAV or the Megasquirt solenoid equivalent. And I believe I don't need an AFM. But what about the Thermostat housing? I know I need a CLT sensor, but could I just add one to the existing Thermostat housing? Thanks, everyone, this is a great forum for fielding ideas. Randy

So I didn't know what an AAV was so I googled it and it is obviously a Assault Amphibian Vehicle which I am sure you don't need in your EFI system .

You either need an Aux Air Valve or a better choice is the stepper motor type IAC Idle Air Control that I forgot to mention above. The IAC is a variable device so you get warm up throttle control and idle control. MegaSquirt has a 10 point table that you fill in with 10 temperatures and 10 associated positions for the actuator inside the IAC which gives you the air flow control. Take a look at www.DIYautotune.com go to the MegaManual section of the software and start reading, be prepared to read A LOT and the same things over and over and over until it sinks in, at least that is what I had to do, but then again I'm not too smart . As far as the CLT temp goes you can put a sensor anywhere that it will pick up the coolant temp which would include an adapter that could go into one of the hoses or into the stat housing as you suggest.

[markandson]

Here is a link to the proper MegaManual

[Wolfman3002]

Well,
I think I've made the decision to go w/ the Megasquirt system, after reading the replies here and in other threads. I like the tunability of it, and it will clean up the stock injection system by eliminating several components, although it does mean I have to purchase several additional pieces (sensors, TB, etc).

Gumby,
I'll keep you in mind when I start building my engine and decide whether to go w/ the EDIS ignition or stay w/ the distributor.

Mark,
You may have answered this before in another thread, but what Throttle Body did you use, and how did you incorporate the IAC into it? Was it already part of the TB?

Finally, a general question about the Thermostat housing. Looking at the '75 Manual Supplement, it looks like the thermostat creates a variable valve for the water, so it varies the amount of water going into the radiator depending on the coolant temp. Is this correct? And if so, is there any advantage or difference to this setup over the traditional thermostat setup? I'm trying to find out if there's any reason to have the EFI Thermostat housing, when going to the Megasquirt system.
Thanks again everyone,
Randy

[Gumby]

I have a spare stock 2.4 throttle body which was used with an early motronic EFI. I am going to use a 3.0 CIH throttle body + cut down intake on my 2.4L, if you are interested in the 2.4 TB pm me. I also have a 2.4 intake manifold but it won't fit into a GT or Manta A without modification.