'74 Spider conversion to FI

[prodigalson]

I’d like to convert my ’74 Spider to fuel injection for multiple reasons, not the least of which is that I work for Bosch, but also I'm much more familiar with FI and it makes good powa!

I have a few questions:

-Does the Euro version of the fuel injection system differ from the North American version? (a friend from work is giving me a compete FI system from a Euro Spider. I'm asking because he said that the engine that the FI system came from was 122hp. Maybe because it was 9.8:1 CR and tuned for it?).

-Can the conversion be done with a 1756cc engine block/heads?
-Assuming that it can be done with a 1756cc block/heads, how much HP would I be giving up?
-Any other undesirable consequences of using the 1756cc block/heads?

-Sounds like the Bosch ECU cannot be easily be tuned to accept HP modifications (CR increase, bigger valves, bigger cams, etc). If I went with an aftermarket ECU like Megasquirt I should be able to dial in the necessary fueling, correct?

If the original air flow meter is removed, how does the ECU (Megasquirt) calculate air flow? Air density tuning? Modern MAF?

[RRoller123]

TTBOMK, the only real tuning that you can do easily with the stock system is air flow: by fiddling with the bypasses (AAV, Idle Screw, AFM Bypass) or fiddling with the fuel mixture a little bit by playing around with the tension on the AFM flap. Some folks have changed injectors to change fuel flow for AFR mixture and top end power reasons as well. I am no expert, but I would think that the stock FI system would have one heck of a time working well on one of the older motors with smaller displacement, as so many parameters are fixed. There is no customer accessible tuning on the ECU, you would literally have to start changing resistors, etc.

[AndyVAS]

The stock system doesn't adjust very much. There isn't any reprogramming. Conversion to MAP hasn't been done on this Bosch system that I'm aware of.

As for putting it on the smaller motors, it's great. The stock systems run a bit on the lean side at higher RPMs and WOT but when you drop the demand the system keeps up. Having put the system on both a 1756 and 1608, I highly recommend it.

You should make more power with Bosch EFI than a single carb. Dual carbs make about equal peek power but not as much average power.

[kmead]

Actually I believe it would likely work just fine.

Basically the system is reading the amount of air going in and then releasing a given amount of fuel as a percentage of the amount of air. Given this even though an early engine may not pump the maximum amount of air the system is capable of applying fuel to, it will still provide the right amount of fuel in ratio to the actual air pulled into the engine.

What the stock injection system doesn't deal well with is cams with signficant overlap as they push some of the air back into the intake, particularly at idle. This causes the system to not meter the air properly causing fuel issues.

The system does rely on certain parts to be in the right places, particularly the coolant temperature sensor, so you will need the late style neck from the head to the two coolant hoses.

Getting the entire wiring harness, which is completely separate from the rest of the engine compartment and the rest of the car, is critical to you being successful in your install. You will need to make good use of the Fuel Injection Troubleshooting Guide after you complete your install as you will likely find a few errors in your work or in some of the old parts you are transferring.

The engine will make good power and most importantly will be much more consistent when running. It won't make as much power as a well tuned set of IDFs but it will surpass the standard carb and manifold. You will want to go to the later header with two outlets and two into one downpipe if you don't already have one.

Good luck and please let us know how it goes.

[RRoller123]

This will be fun to watch, I am looking forward to it!

[FiatMac]

Actually I believe it would likely work just fine.

Basically the system is reading the amount of air going in and then releasing a given amount of fuel as a percentage of the amount of air. Given this even though an early engine may not pump the maximum amount of air the system is capable of applying fuel to, it will still provide the right amount of fuel in ratio to the actual air pulled into the engine.

Agreed. Where the stock fuel injection runs into trouble is when the air flow exceeds the the capacity of the air flow meter(AFM).

[So Cal Mark]

we've done several conversions on 1800 motors and the system works fine, even with mild performance cams.

[prodigalson]

Thanks for the feedback fellas! I'm sure I'll have plenty of questions as I move forward with this!

[85redpini]

if would be cheaper to buy a fi spider considering what they are selling for on ebay. usa version had no where that horsepower. it would be simple enough to check a European bosch catalog versus a usa bosch cat to see if the bosch part numbers were different.

I’d like to convert my ’74 Spider to fuel injection for multiple reasons, not the least of which is that I work for Bosch, but also I'm much more familiar with FI and it makes good powa!

I have a few questions:

-Does the Euro version of the fuel injection system differ from the North American version? (a friend from work is giving me a compete FI system from a Euro Spider. I'm asking because he said that the engine that the FI system came from was 122hp. Maybe because it was 9.8:1 CR and tuned for it?).

-Can the conversion be done with a 1756cc engine block/heads?
-Assuming that it can be done with a 1756cc block/heads, how much HP would I be giving up?
-Any other undesirable consequences of using the 1756cc block/heads?

-Sounds like the Bosch ECU cannot be easily be tuned to accept HP modifications (CR increase, bigger valves, bigger cams, etc). If I went with an aftermarket ECU like Megasquirt I should be able to dial in the necessary fueling, correct?

If the original air flow meter is removed, how does the ECU (Megasquirt) calculate air flow? Air density tuning? Modern MAF?