FJ62 ignition/ignition timing experiment & guinea pig thread

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
Rather than continue hijacking the pinging/knocking thread from @ChaserFJ60 (Pinging/knocking? in a FJ60 with a 2FE. DIZZY TIMING - https://forum.ih8mud.com/threads/pinging-knocking-in-a-fj60-with-a-2fe-dizzy-timing.1261140/) to detail the experimentation with my FJ62's ignition timing, I figured it'd be good to start a new thread for an ignition knowledge base and real world experience.

Yesterday I returned from a 400 mile round trip after setting my initial timing back to 7°. Idle smoothness was unchanged from before, but my performance overall and fuel economy were absolutely atrocious by comparison (this just now occurred to me just before hitting Post, but before I change anything else I'm going to double check and ensure that my E1 and TE1 were properly shorted when I set the timing last Thursday. Will edit this post once I do). If E1 and TE1 WERE properly shorted during the adjustment, then despite @Lead Head giving his explanation of the operation of the ignition portion of the 3FE's ECU (here: Pinging/knocking? in a FJ60 with a 2FE. DIZZY TIMING - https://forum.ih8mud.com/threads/pinging-knocking-in-a-fj60-with-a-2fe-dizzy-timing.1261140/page-5#post-14018058 and here: Pinging/knocking? in a FJ60 with a 2FE. DIZZY TIMING - https://forum.ih8mud.com/threads/pinging-knocking-in-a-fj60-with-a-2fe-dizzy-timing.1261140/page-5#post-14018536 which made enough sense to me to convince me to try going back to factory timing); given what I experienced on this trip, I'm back to my original presumption that the curve itself is controlled by the ECU, using the initial manually set timing as a baseline and increasing from there based on engine RPM and load. How it determines load, if this system does (I honestly doubt it does given how primitive our EFI system is with its lack of knock sensors and other sensors used in modern systems), I would love to find out. But it would involve much more digging on my part once I have the chance to do so.
To detail just how badly my performance was affected, a long steep grade in central WA known as the Orondo Spur that I consistently hold at or within 5 miles over the speed limit in 4th gear since the H55F conversion when climbing was spent with most of the time on this trip not even able to reach the speed limit, and having to downshift to 3rd just to reach the speed limit. Starting off from a level stop I would usually start in 2nd gear with no problem, even with a fully loaded truck and the A/C going. Not this time. The engine lugged bad when I would attempt it and led to me constantly having to start in 1st gear at all stops. This was with a brand new air filter put in just before the trip as well, given how bad the smoke was in my region from the wild fires this summer.

Before I do any more adjustments to the timing I'll fill my tank after work tomorrow and post what my actual fuel economy was.

To also add, I've been using a Mallory 6AL ignition box for I think about 15 years with a Promaster coil. This is triggered by my OEM igniter, which I've been intending to bypass and remove so that the ECU trigger signal would go directly to the Mallory box rather than from the ECU to the OEM igniter and then to the Mallory box. Just haven't gotten to it yet.
 
Last edited:
Joined
Jan 5, 2015
Messages
556
Location
Texas
Website
www.etsy.com
You'll know the TE1 and E1 ports are shorted when you see the CEL blinking. It will either start blinking the codes the ECU has stored or start blinking quickly nonstop.
 

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
You'll know the TE1 and E1 ports are shorted when you see the CEL blinking. It will either start blinking the codes the ECU has stored or start blinking quickly nonstop.
Exactly which occurred to me while posting that. I hadn't considered verifying that last Thursday when I dialed back the timing.

Edit: Just went out to look, and looking at where the dielectric grease was disturbed, it looks like I inadvertently plugged the wire into the terminal adjacent to E1 instead of E1!

Total "got ahead of myself" bonehead move that verifying via the CEL would've told me from the get-go, so now I at least know my timing is dialed WAY back. I'll readjust later this afternoon.

Let's all point and laugh at the big dummy :rolleyes:
 
Last edited:

OSS

SILVER Star
Joined
Jun 30, 2017
Messages
3,895
Location
Oblivion
Tee hee - but rest assured that we've all done something equally "doh" in the past, so join the club.
It's great that there's a forum here to bounce ideas & questions off of. When the FJ62 was unveiled in 1988, the Internet for the most part didn't even exist - we were all on our own w the FSM as our only bible.
 
Joined
Mar 18, 2020
Messages
252
Location
AL
Spook50 , Have you checked your cylinder psi ?

Be interesting to see the difference between you and chaserfj60. He was at 178psi I believe.
 

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
Tee hee - but rest assured that we've all done something equally "doh" in the past, so join the club.
It's great that there's a forum here to bounce ideas & questions off of. When the FJ62 was unveiled in 1988, the Internet for the most part didn't even exist - we were all on our own w the FSM as our only bible.
Haha right? Honestly I have no problem admitting to a mistake or goof, as long as the end result is better understanding overall of these trucks that'll help them last longer or run better. Even if it comes to a "learn from my mistake" scenario. Plus the more I learn the better, also. I did accomplish a couple other unrelated tests this weekend with my truck that I'll post up the results of, so some interesting (in a good way) findings with those.

@F226continental I haven't done a compression test in a few years. Was prepared to do a leakdown test last summer because of a suspected oil consumption issue that was solved before I got to doing the test. As it is there's been no problems with performance until this last weekend, and my fuel economy has been on the upper end of normal for an FJ62 with an H55F and 33x12" tires (average of 14 with the highest I've gotten being 16.5 over my Memorial Day trip to central WA this year) so I haven't felt the need to test compression or leakdown recently.
 
Joined
Jul 21, 2012
Messages
327
Location
Rhode Island USA
The only thing I was trying to say in that other thread is if you set the base timing without jumping TE and TE1 - you will be very retarded.

Setting the base timing just sets the computer's frame of reference. Imagine the exit of the parking garage of a high-rise building leads you into the 7th floor of the building, and you want to go to the 12th floor. None of the floors are marked, but you know that since you started out on the 7th floor, you need to walk up 5 flights of stairs to get to the 12th floor. If you want to go down to the 4th floor from the 7th, you need to walk down 3 flights of stairs. This works because you always know you are starting out on the 7th floor. The computer in your FJ62 is the same way. It's expecting to "start off" at 7°BTDC, so all of its calculations are in reference to that point.

Now, I'm not saying 7°BTDC will result in the best performance - just that it's the default frame of reference. The engine uses a "3D" mapped spark system based on load & RPM with modifiers for things like EGR on/off, intake air temp, coolant temp and a few other things. Load is calculated by comparing the measured air-flow vs engine RPM. When you turn the distributor housing, you're shifting that frame of reference. But the engine has no way of compensating if you "shift" that frame of reference. Imagine our high-rise scenario again. This time instead of starting off on the 7th floor, you get carried blind-folded to the 10th floor. Your blind-fold is removed, and they lie to you, telling you that you are on the 7th floor. Your first instruction is to go up to the 12th floor - so you, assuming that you are on the 7th floor - walk up 5 flights of stairs as per normal. You walk in the door way and immediately knock your head on a low hanging metal beam.

That's what's going on when you advance the distributor. You basically blind-fold the computer and carry it further forward than its expecting. All of its calculations are in reference to the assumption it's being timed at 7°BTDC. You crank the timing to full advance, and it's apt to start knocking because it has no idea where it is. It just *thinks* it knows where it is. There is where you can run into issues if you start doing mods to your engine that cause pinging/knocking. If you remove your EGR and your engine starts pinging and you retard your distributor to compensate - you are retarding your ignition timing across the entire 3D ignition map. You are giving up power everywhere. Now maybe your modification makes up for that - I don't know.

This timing thing has nothing to do with the 3FE's EFI being old. EFI was a quite mature technology by the late 80s, and the 3F's EFI system really isn't THAT primitive. The 3FE's EFI system isn't really much different than anything else up until the mid-90s. Really the only things anachronistic on it are the cold-start-injector and the AFM - but both were fairly contemporary in 1988. I mean shoot, GM was still using TBI up until '95...
 

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
The only thing I was trying to say in that other thread is if you set the base timing without jumping TE and TE1 - you will be very retarded.

Setting the base timing just sets the computer's frame of reference. Imagine the exit of the parking garage of a high-rise building leads you into the 7th floor of the building, and you want to go to the 12th floor. None of the floors are marked, but you know that since you started out on the 7th floor, you need to walk up 5 flights of stairs to get to the 12th floor. If you want to go down to the 4th floor from the 7th, you need to walk down 3 flights of stairs. This works because you always know you are starting out on the 7th floor. The computer in your FJ62 is the same way. It's expecting to "start off" at 7°BTDC, so all of its calculations are in reference to that point.

Now, I'm not saying 7°BTDC will result in the best performance - just that it's the default frame of reference. The engine uses a "3D" mapped spark system based on load & RPM with modifiers for things like EGR on/off, intake air temp, coolant temp and a few other things. Load is calculated by comparing the measured air-flow vs engine RPM. When you turn the distributor housing, you're shifting that frame of reference. But the engine has no way of compensating if you "shift" that frame of reference. Imagine our high-rise scenario again. This time instead of starting off on the 7th floor, you get carried blind-folded to the 10th floor. Your blind-fold is removed, and they lie to you, telling you that you are on the 7th floor. Your first instruction is to go up to the 12th floor - so you, assuming that you are on the 7th floor - walk up 5 flights of stairs as per normal. You walk in the door way and immediately knock your head on a low hanging metal beam.

That's what's going on when you advance the distributor. You basically blind-fold the computer and carry it further forward than its expecting. All of its calculations are in reference to the assumption it's being timed at 7°BTDC. You crank the timing to full advance, and it's apt to start knocking because it has no idea where it is. It just *thinks* it knows where it is. There is where you can run into issues if you start doing mods to your engine that cause pinging/knocking. If you remove your EGR and your engine starts pinging and you retard your distributor to compensate - you are retarding your ignition timing across the entire 3D ignition map. You are giving up power everywhere. Now maybe your modification makes up for that - I don't know.

This timing thing has nothing to do with the 3FE's EFI being old. EFI was a quite mature technology by the late 80s, and the 3F's EFI system really isn't THAT primitive. The 3FE's EFI system isn't really much different than anything else up until the mid-90s. Really the only things anachronistic on it are the cold-start-injector and the AFM - but both were fairly contemporary in 1988. I mean shoot, GM was still using TBI up until '95...
Good explanation! Still on par with how you described it in the previous thread, but after reading this it gives me a better understanding of what you were initially describing.

I didn't get out today to reset the timing, so tomorrow after work with my engine warm I'll do it PROPERLY per the FSM procedure. Something I noticed was that when I began last Thursday I noted it was at 13° (as it turns out, without the jumper wire properly installed), and the FSM says to verify that it's at 12° with the jumper wire removed. So on its face it would seem I was pretty close to stock by using the vacuum method I had been using before. I'll find out for sure after readjusting and going through a couple tanks of fuel.
 

Kleatus

GOLD Star
Joined
Jun 6, 2012
Messages
1,234
Location
Missouri
@Kleatus what were you saying about timing being affected by a delete that Joe had done? It was a campfire detail that stood out.
Basically same as @Lead Head says above. That you can adjust the base timing on a 3FE but the curve is set in ECU, and counts on EGR being operational. You can't "recurve" it for other changes like you can on older carb engines. EGR flow isn't called for at full power anyway, so people that think they're unlocking some magic 3FE power by getting rid of it are silly.
 

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
Basically same as @Lead Head says above. That you can adjust the base timing on a 3FE but the curve is set in ECU, and counts on EGR being operational. You can't "recurve" it for other changes like you can on older carb engines. EGR flow isn't called for at full power anyway, so people that think they're unlocking some magic 3FE power by getting rid of it are silly.
Yup. I realized a short time after deleting mine that losing the EGR is mainly for the purpose of losing non functioning parts that've worn out with age and use, increasing longevity once the carbon from it is cleaned from the intake manifold and valves, and freeing up some under hood real estate.
 

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
An update on my experimenting so far. After setting my timing back to 7º BTDC using the method in the FSM, performance is still a bit less than what I had when using the vacuum method (where I did NOT short E1 and TE1 on the diagnostic connector), and when coasting at zero throttle with the clutch fully engaged (pedal out), I notice a very slight sputter from the exhaust that I don't hear when going down a hill on compression or actual compression braking. Fuel economy is good though, especially for a 62 running 33x12" tires. In four tankfuls my average economy is 14.6 MPG. My next step will be upping my timing to 9º BTDC (again with the E! and TE1 terminals shorted). That I'll do in a few weeks though, since now that I know what my average economy is for driving around town and commuting to work, I want to see how my roof rack and new (to me) Yakima box will affect my economy for an upcoming trip across the state.
 

Spook50

Skål
Supporting Vendor
Joined
Feb 16, 2005
Messages
6,564
Location
Spokane, WA
A couple days ago I upped my timing (E1 and TE1 shorted per the FSM and using my timing light) to 10º BTDC. Haven't yet run through a full tank of gas, so no word on differences good or bad on fuel economy but overall performance is much improved. Getting up to speed on freeway onramps is much quicker, and going up a somewhat long grade just west of Spokane I make it all the way up the hill without even losing speed if I can hit it at 75 MPH and still don't have the pedal floored, though it is most of the way down.

A few weeks ago I made a 370-mile round trip with a fully loaded truck carrying a Yakima rooftop box (their SpaceBooster 11 that I bought from someone on Craigslist) that was also weighed down with scrap lumber to build target holders, and surprisingly even all that extra weight my fuel economy wasn't affected at ALL. No relation to timing (I was still at 7 for that trip), but just a comment on how much I love my H55F.

I'm making another trip this weekend with the timing at 10º, so it'll give me a good first impression of how my economy will be affected by advancing the initial timing farther. With more experimenting I want to find the ideal initial timing for my truck, then go back to square one and set it via the vacuum method (which will require E1 and TE1 to NOT be shorted), then afterward short E1 and TE1 and see where the vacuum method lands my initial timing compared to the optimum setting.

As a reminder again, I'm running 33x10.5" tires, an H55F, factory 4.11 gears and an unmodified (gear-wise) late 60 series transfer case.
 

Users who are viewing this thread

Top Bottom