Ignition on FI

[diethelm]

I have been noticing a lot of cars with FI that are running distributors. What am I missing? All of the FI systems we run on sand cars use coil packs which can be mounted in any place within the engine bay. What is the purpose of keeping the distributor and limiting the timing options?

[philminotti]

Several reasons, IMO.
1. Distributorless doesn't look right.
2. Cost. Also, you need an oil pump drive distributor plug that also generates a cam sync signal (for sequential efi)
3. See #1.
4. Distributors work just fine.

[Ronbo]

Like Phil said, unless you go dry-sump you don't eliminate the biggest failure point which is the pump drive (cam gear). If your distributor is set up right it will not cause problems with timing, but it should checked for index.

To do it right your looking at $3k minimum, I can buy a lot of spare distributors for that kind of money. Not to mention I'll probably not notice the difference between 634hp and 640hp.

And it looks right for what that's worth...

[RICK LAKE]

diethelm It depends on which FI system you are looking at. I run a F.A.S.T older system. I have 60 degrees of timing. How much more do you want? 90% of the FI systems need a crank trigger and a cam sensor. Cam sensor tells the motor when to fire the injectors either in batch or the start of sequential order. The crank sensor is for the timing of the motor. My crank timing is 55 degrees before TDC. Others may vary. Unless you are a dry sump motor, you will still fine it easier to go with the distributor firing the plugs. Moldec has the 4 coils. I don't know alot about this FI system but like every system there are limits and extra bells and whistles. My system has timing and fuel control for each cylinder. Most don't. This helps the weaker cylinders to balance out the motor better. 4 coils make more spark and also wasted spark to each cylinder. My HVC coil works harder. Bottom line, it's what look you are looking for. Rick L. Ps I left out the price range from $1,000.00- $9,000.00 depending on intake, injectors,sensors, throttlebody, or throttlebodies, ( like TWM setup ) ECU and wiring for the car. If you go FI, make sure you are going with a wide range O2 sensor setup.

[diethelm]

Interesting responses. On the sand cars we run a crank trigger but do not use a cam sensor. You can run the crank trigger off the dampner in the front. Also, once we tune on the dyno, we pull and plug the o2 sensor as it is not used. Most everyone used to run electromotive and has now moved to Fast. A long time ago we used Haltec with distributors but found on the same engine, significant hp and torque pick up with coil packs. I still need to understand how you can have as much control with a distributor over coil packs especially when it comes to limiting rpm and shutting down the engine in cases of temp, oil pressure and other issues.

With respect to looks, I suspect FI in no way looks like an original carb setup and the coil packs can be hidden. A set of 8 coil packs is 180 bucks so I am not sure how that is more expensive than an MSD spark box and a distributor set up.

In any event, thanks for the input, I am thinking of building a car but need to do more research.

[Ronbo]

With respect to looks, I suspect FI in no way looks like an original carb setup and the coil packs can be hidden. A set of 8 coil packs is 180 bucks so I am not sure how that is more expensive than an MSD spark box and a distributor set up.

Depends on the system:

www.mass-floefi.com

Can't do much to hide the fuel rails though...

[RICK LAKE]

diethelm It sounds like a basic system you are running like the old Accell FI system when it came out. 4 injectors in the top of the throttle body that look like a carb. It had 4-6 adjuster for the system, cold start, low rpm, medium rpm, high rpm and ilde. It was an open loop system. They added a O2 sensor the next year and the system got alot better. It was a batch fire system and worked good as long as no water got on or near the ECU. It only had limited controls. If you go back about 40 years there where mechanicial fuel injection system like the Vette's. As far as the timing between a single coil and multi ones, it's all in the soft ware. You will make a hotter spark with the 4 pack over a single. As for duration of the spark, msd has a 15-20 degree long spark. The coil packs are less but hotter for a shorter time. For shutting down a motor, a low oil pressure sensor would kill the motor is less than 20 psi was in the system. You need a bypass to start the car. Knock sensors can be added to retard timing under load. Coolant sensor can work like the oil pressure and turn off the fuel pump if a certain temp it reached. You can hook up to either a fuel system or ignition system to save the motor. Fuel is better with an FI system. You are basicly looking at the has thing as what a MSD box does with timing control and a rev limiter chip. Rick