Electronic Fuel Injection aftermarket and retrofit

Howard Jones

Gold Supporter
#1
Holley EFI 550-406 Terminator EFI 4bbl Throttle Body Fuel Injection System - Hard Core Gray

I am seriously considering a Holley FI system for my SLC. No matter who I ask I can't find anyone who has done one of these with a radical cam, 300 degrees of duration and more than .550 lift, AND it worked as it learned the system WITHOUT a chassis dyno tune by a high proficiency tuner.

I know I can install the system and make the necessary mods to my fuel system to get it all on the car but I don't really want to spend 6 months taking it from tuner to tuner trying to get it to work BETTER than the 750 double pumper I have on the car now. I can tune them myself pretty well and use the car as I do it but these FI systems all say that they are self learning but time after time I find instances where the car had to be tuned by hand AND by a very knowledgeable and experienced tuner.

So what I propose is we use this thread to document our builds, their engine parameters, such as compression ratio, head type, and cam specs , along with FI type system and tuning experience.

We should really be able to produce a valuable resource that I haven't been able to find anywhere else.
 
#4
I've installed one multi-port EFI system and it works well....right out of the box.

That said, I took extreeeeeeeeme care to install the system properly with all the recommendations and instructions followed. These systems are not easy to install properly, they require relatively high levels of mechanical and engineering know-how.

Honestly, my sense (my guess...) is that when these systems don't run right it's often because the DIY installer just hasn't followed the instructions or didn't pay attention to the details. For a multi-port (8 injector) system there are a TON of details and variables - things like:

1. is the fuel pressure right, and consistent?
2. right choice of injector?
3. is the vacuum signal correct and consistent?
4. is the 02 sensor installed properly and getting the right signal?
5. is the TPI reading properly?
6. is the ECU and associated wiring properly grounded and shielded from interference?
7. are all the sensors properly selected and installed?

The list goes on and on. A more simple 4barrel system such as the Holley system eliminates some of these variables but it's still not easy.....not as easy as putting a new Holley carb on your engine.

The devil is in the details in my view.

Great thread by the way Howard - should be some healthy debate.
 

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Howard Jones

Gold Supporter
#5
The Holley tech was very specific about vacuum. He said that 10 inch's of vac. was a absolute minimum for the Terminator system. The reason for this was that with a low vac. sig. raw fuel would condense on the floor of the intake manifold and cause the system to run rich at low engine speeds. This issue was the main reason that the self learning software had such a hard time with low vac.

The Terminator system could be tuned to work but the self learning option would need to be disabled and the system fuel table would be have to manually tuned.

On the other hand the port injection system didn't have this problem because the fuel was directly injected into the intake port. He said that the self learning option could be left to itself with the port injection system and it would be OK.

BUT if you look at the cost it very clear that I would have $4000 into it before I was done. That's a lot of dollars only to make just about the same power and run nearly the same lap times. I think I will be changing my intake manifold and working on my Holley for a while longer.

If the price point would come down 25-30% I might reconsider.
 
#8
I would highly recommend calling Dave Erlich at Autotrend EFI (530 642 0999).
He has extensive experience as a tech rep and installer with several brands from
The beginning of EFI. He has a wealth of experience with this subject. And with Holley EFI.
 

Randy V

Administrator
#9
Interesting thread...
I’ve been giving stack style injection a look for my latest project car.
My only concerns are that IR intake manifolds generally don’t have a shared plenum - therefore can’t provide a good single point reference to MAP and also can’t take advantage of a single IAC.
I’m curious as to the work-arounds for these and just what has to be compromised..
 

Ron Earp

Administrator
Staff member
#10
Did a lot of research on this topic eight months ago. Went with the Holley Sniper for my mild 302 in my daughter's car. So far so good.
 
#11
So why would a carburetor, allowing fuel into the plenum at low vacuum be any different that the 4bbl throttle body in terms of fuel condensation? Could this be run under Speed Density verses other methods of management?

I'm using Holley's port injection system, which had a steep learning curve, but I think I've got a handle on it now. It does work well.
 
#12
Interesting thread...
I’ve been giving stack style injection a look for my latest project car.
My only concerns are that IR intake manifolds generally don’t have a shared plenum - therefore can’t provide a good single point reference to MAP and also can’t take advantage of a single IAC.
I’m curious as to the work-arounds for these and just what has to be compromised..
Randy, see my post (#7) on "8 stack injection". But you've got to have vaccum ports on the throttle bodies.
 
#13
For those running a gen1 chevy small block like the one in my 1980 Corvette there is a OEM LS1 type of fuel injection conversion available that is pretty trick.

You swap the front timing cover to a Vortec cover. It has a crank sensor.

You remove the balancer and then install a custom made reluctor wheel. Then you remove the same thickness as the reluctor from the snout of the balancer before pushing it back on.

You remove your distributor and install a Vortec distributor. It has a cam sensor built in. You get rid of the cap and install a blanking cap in it's place. You are no longer using it as a distributor. It's only function is to provide a cam sensor signal and to spin the oil pump.

You install 8 coils like the LS engines have. You can use A LS2 type of throttle body and DBW pedal setup. You will be using a LS1 type of ECM. The firing order for LS engines is slightly different but it can be changed in the tune.

You can use a single plane intake and a elbow for the throttle body. There are a few choices out there for ready made intakes that have fuel rails. The one I used in the picture was made by Accel. The elbow is made by Edelbrock. The elbow can be mounted in different directions for those using a mid engine layout.


You get a mail order tune and then load it into the LS1 ECM with HP Tuners or send them your ECM and they will load it for you. This lets you start it up and run it. You then take it to a dyno tuner to have it dialed in.

EFI Connection is the website for further info if you are interested. They will build the harness for you. EFI 24x™ Product Line - EFI Connection, LLC

This is system is superior to most of the after market setups. It is sequential multiport injection, it uses 8 injectors, 8 coil packs and has control of the timing, it uses both a MAP and MAF sensor and best of all uses all OEM sensors and ECM.
 

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#14
You can further upgrade the above system to a LS3 level with their 58X system.

The system I described in the previous post is their 24X system which is from a LS1

The difference is finer resolution and newer ECM that can handle the more complex calculations.
 
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#16
Interesting thread....
My only concerns are that IR intake manifolds generally don’t have a shared plenum - therefore can’t provide a good single point reference to MAP and also can’t take advantage of a single IAC.
I’m curious as to the work-arounds for these and just what has to be compromised..
Hey Randy, the Borla Induction manifolds (Both the throttle body or Weber-Style) employ a manifold that has cast-in plenum facilities for the MAP sensor and the Idle Air Control. My IAC and vacuum plenums are hidden under the manifold and work very well using the GM sensors and IAC stepper motor. This is the same architecture that Roush uses with their IR series...
 
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#18
I think the difference in intake manifold fuel pooling between the throttle body FI and a carb is that the carb will supply fuel demand directly related to the vacuum signal. At low vacuum, mid range rpms and opening throttle (more power) the carb will add fuel via the power valve and additionally the accelerator pump covers the period directly after the throttle is cracked wide open .There is way too much going on in a carb to get into here but the above is how a carb deals with different fuel requirements as related to vacuum signal.

However I think what the Holley tech was saying was that the self learning software needed a wider range of vacuum so that it could calculate correctly the fuel to be delivered during this period.

Both systems need to deal with the fact that under high vacuum the fuel remains atomized in the intake manifold but as vacuum decreases to near zero the fuel droplets drop out of suspension (atomized) and fall to the floor of the intake runners. This causes a lean condition. The carb system just squirts a bunch of fuel into the intake right at this point with the Accelerator pump. The TB FI self learning systems doesn't know to do this because It is having a hard time telling the difference between high and low vacuum in a engine that doesn't make very much vacuum to begin with. So you have the same problem as the carb does without a way to compensate for it.

The direct injection system fuel map can be manually modified to correct this issue and the issue itself is much less pronounced because the fuel is being directly injected into the intake runner right inform of the valve. There just isn't any fuel in the common plenum of the intake manifold to pool up.

Hell I hope that helps a bit but in Ron's case he has the engine spec the TB FI is made for. They do work well with a street to light performance cam and good vacuum.

Good read on how carbs work,

Techtips - Holley Carburetor Operating Principles
 
#19
I think the difference in intake manifold fuel pooling between the throttle body FI and a carb is that the carb will supply fuel demand directly related to the vacuum signal. At low vacuum, mid range rpms and opening throttle (more power) the carb will add fuel via the power valve and additionally the accelerator pump covers the period directly after the throttle is cracked wide open .There is way too much going on in a carb to get into here but the above is how a carb deals with different fuel requirements as related to vacuum signal.

However I think what the Holley tech was saying was that the self learning software needed a wider range of vacuum so that it could calculate correctly the fuel to be delivered during this period.

Both systems need to deal with the fact that under high vacuum the fuel remains atomized in the intake manifold but as vacuum decreases to near zero the fuel droplets drop out of suspension (atomized) and fall to the floor of the intake runners. This causes a lean condition. The carb system just squirts a bunch of fuel into the intake right at this point with the Accelerator valve. The TB FI systems doesn't know to do this because It is having a hard time telling the difference between high and low vacuum in a engine that doesn't make very much vacuum to begin with. So you have the same problem as the carb does without a way to compensate for it.

On the other hand the port injection system fuel map can be manually modified to correct this issue and the issue itself is much less pronounced because the fuel is being directly injected into the intake runner right in front of the intake valve. There just isn't any fuel in the common plenum of the intake manifold to pool up.

The self learning TBFI system's fuel map can be manually input just like the port type to compensate for this but in can only be done with the self learn toggled off. This sort of defeats the point of buying a self learning system in the first place.

Hell I hope that helps a bit but in Ron's case he has the engine spec the TB FI is made for. They do work well with a street to light performance cam and good vacuum.
 
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