Where should I set the timing at with Holley Pro-Jection?

[gwinn]

Yeah, that's my question. I can't find it anywhere in the install/operation manual. First we set it at 0, but it's ran like crap. It seems to run better at +3, but still crappy. What is the best setting?

[Josh D]

From what I understand is that you can get away with more initial advance with fuel injection due to the cooling effect of a better atomized air/fuel mixture. I would start at about 10* initial (vacuum advance disconnected) and work from there. The lower elevation and ambient temps of Phoenix will dictate how much advance you will be able to get away with. Are you running a relatively mild cam (i.e. one without much overlap)? Is your compression ratio stock? These will also play a factor as they determine how much cylinder pressure your building at low revs and timing is critical to prevent detonation. My motor being stock cammed, stock compression, and running above 6000 ft elev., I can run as much as 15* initial with no ping. I'd try starting at 10* initial and see if it pings. If it does, back down to 8*, etc. If it doesn't, go up 2* and see if it pings. Again, ambient temp plays a role so you might have to back of the timing a few degrees in the summer. Also, are you running closed or open loop FI? Running a lean condition contributes to detonation as well, so tuning the right fuel mixture for your application will also need to be done. Let us know how it goes.

[gwinn]

Compression is: 9.5:1

Cam is:
Specifications:
* Advertised duration: 272 intake/284 exhaust
* Duration at .050 in. cam lift: 216 intake/228 exhaust
* Gross valve lift: .484 in. intake/.512 in. exhaust
* Lobe separation: 112 degrees
* Basic rpm range: 2,000 to 5,000
* Good idle, daily usage and off-road, towing, performance, and fuel efficiency
* Cruise rpm: 2,600 to 3,000
* Recommended compression ratio: 8.75:1 to 10.5:1

I'm running the open loop FI.

Thanks!

[Josh D]

Ok, your cam/compression combo looks ideal and will definetely want some timing advance for better bottom end. The kick is that you'll need your fuel mixture right to prevent a lean condition under load that could cause detonation or worse, burn an exhaust valve (higher octane fuel will help as well). Now, I've never dialed in an open loop FI before, but the principles should be the same as carburation except you just have to adjust knobs. On air cooled aircraft engines, the way we would dial in fuel mixture was to run up the engine to a given rpm, then adjust the fuel mixture towards lean. The rpm would start to rise and the cylinder head temp (cht) would start to rise as well. When adjusted towards rich, cht would drop and so would rpm's. To rich and rpm's would really start to drop off (loosing power). Because aircraft engines operated at sea level to 13,000+, they have to be able to compensate fuel mixture to maintain power and not lean out and overheat. Anyway, if you understand that principle, it should help you dial in your FI. Now, back to your timing. I still think 10* is a good starting point, however, make sure your air/fuel ratio is ok, or even on the rich side. The idea is to run as much intial advance as your engine can handle without detonation or having to run so rich that your loosing power from incomplete combustion. It's really a balancing act. The factory timing specs for your Wag were very conservative, based on a low compression, mild cam, restrictive exhaust, tall gears, lean carbed, low rpm motor in a heavy vehicle. It just no longer applies to your combination now. I hope this makes sense. BTW, looks like I'll be moving back to the Phoenix valley sometime this fall and look forward to meeting and wheelin' with the AZ group.

[gwinn]

Thanks Josh! smile.gif We tried everything from +3* to +15* and I've definately got a problem! :( I've set it back to 10*. It still runs crappy, but I think I/m running rich. I'm gonna take it to Chuck's Speed Center and have them got thru it next week. I know it will be a chunk of change, but this Jeep contols my attitude, and it ain't been good lately! :D

[Joe Guilbeau]

Read this first...

I been running an Analog TBI Holley 502 for almost 10 years, and here is how I set mine, and it has worked for the past three three engines.

Make sure that the pots on the ECU are set to mid range.

1. Ensure that you have correct voltage and grounds, this means that during cranking the voltage to the Electronic Control Unit is at least 10-11Vdc, preferrable feed it with a Relay.

2. Make sure that the wiring and grounds are good on the Jeep, that the alternator is not "iffy" and that the battery is fully charged.

3. Back out the Idle adjust screw on the front of the TBI until the Throttle Plates close completely.

4. Turn ignition key to "Run", but not start.

5. Measure voltage to Throttle Position Sensor, it should be 5Vdc.

6. With the Throttle Plates closed all the way, adjust the TPS to send a 0.60Vdc signal back to the ECU. Now open the Throttle Plates all the way, that voltage should go to 4.75Vdc to 5Vdc, while you are there, slowly open the throttle plates and close them, whatch for a linear voltage progression while both opening and closing the throttle plates.

7. Now, with a 7/32 allen wrench and a long nose Number 2 screwdriver, adjust the idle adjust screw so that the engine runs, now let her warm up.

8. You are killing yourself of you do not have a Fuel Pressure Guage installed to the supply side of the TBI at the just in front of the firewall.
Insure that the Fuel Pressure is 14 PSI for starters. If you do not have a fuel pressure guage, then you look at the "conical spray pattern" of the injectors. If the fuel pressure is set right, and the TPS is set right, and the idle adjust screw is set right, and the Fast Idle Solenoid is not engaged on a warm engine, you will have a hard time seeing the spray pattern.

9. Now, play with the fuel pressure until you can blip the throttle and no smoke appears, set the idle adjust screw so that she idles fine, and the Fast Idle Solenoid will have to wait for adjustment until the engine is cold, just go out one morning and adjust it until the engine warms up, and she drops off.

Hope that this procedure helps, it all lies with the Throttle Positioner Sensor, both the Fast idle solenoid, and the idle adjust screw, along with your foot.

The exhaust should not smell rich, pull the plugs after some idle time, if they are black and sooty, you are running too rich.

JAG

[Josh D]

BTT

Thanks, JAG, hopefully gwinn will see this. Great info for those attempting open loop Holley FI.

[gwinn]

I've determined that something is wrong with the ECU. The installer was having a hard time making it work with the Jacobs Ignition and likely fried something with his trial and error technique. I'm taking the whole thing in to Chucks Speed Center and having it combed thru and basically reinstalled next week. Mine is the digital model 2D and I've been told it doesn't have much tolerance for electical abuse. Anyway, thanks guys!