I've seen mine advance as high as 38* on Scangauge, at least while I was paying attention. What I don't understand is how it doesn't ping at 38*. I guess AFR is just right?
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No it is about RPM's the faster the engine spins the sooner before TDC you need to fire the spark plug to get things to burn before the valves open. If you tried to run 38* at 600rpm idle it probably won't work out to well, but if you are running 5000rpms the plug fires sooner to get the fuel burnt as the piston is moving faster to get the spent gases out.
And remember adding and removing timing kind of works backwards. When people talk about retarding timing it is removing degrees from top dead center. When adding timing it is adding degrees prior to top dead center.
For example if you are operating at high rpms and you are seeing 38* on your scan gauge and you have 3* timing you are firing the spark plug 41* of the crank before the piston is at top dead center.
So now if you advance the base timing to 12* + the 38* the computer dials in you are now firing the plug 50* of the crank before the piston is at top dead center.
So remembering that the actual ignition of the gas vapor and air does take "some time" you can clearly see that igniting it too soon will result in the explosion of the gas and air vapor while the piston is still traveling up in its stroke. This is knock.
And remember you might be thinking why are we igniting the gas so soon, but at 5000rpms
That is 84 revolutions of the crank per second.
360 degrees in a revolution
The crank moves 1 degree in 0.000033 seconds.
So a change in timing advance from 3* base or 41* total to 12* base or 50* total is only 0.0003 seconds difference.
And remember adding and removing timing kind of works backwards. When people talk about retarding timing it is removing degrees from top dead center. When adding timing it is adding degrees prior to top dead center.
For example if you are operating at high rpms and you are seeing 38* on your scan gauge and you have 3* timing you are firing the spark plug 41* of the crank before the piston is at top dead center.
So now if you advance the base timing to 12* + the 38* the computer dials in you are now firing the plug 50* of the crank before the piston is at top dead center.
So remembering that the actual ignition of the gas vapor and air does take "some time" you can clearly see that igniting it too soon will result in the explosion of the gas and air vapor while the piston is still traveling up in its stroke. This is knock.
And remember you might be thinking why are we igniting the gas so soon, but at 5000rpms
That is 84 revolutions of the crank per second.
360 degrees in a revolution
The crank moves 1 degree in 0.000033 seconds.
So a change in timing advance from 3* base or 41* total to 12* base or 50* total is only 0.0003 seconds difference.
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On any given engine? No such thing really.
Combustion ratio, quench area size/shape, roughness of the head casting, piston shape, etc all play a role in what your timing needs to be set to, to avoid knock.
When talking about an engine you may have heard the phrase, "Very knock resistant" that just means there are no hot spots in the chamber to cause fuel mixture to detonate early.
That is really why I suggested upping the timing in little increments but without the right tools and without being in the absolute worst conditions you will ever encounter you can't say your setup is safe. This is why you will hear or see, new cars being tested in death valley, or other harsh conditions, they are literally doing this type of work for you and that is the safety factor Toyota decided on. 3* base timing. If you never see hot temps, never have heavy load, never have a heat soaked engine compartment, never get a batch of bad gas, than yes you can push it up.
Combustion ratio, quench area size/shape, roughness of the head casting, piston shape, etc all play a role in what your timing needs to be set to, to avoid knock.
When talking about an engine you may have heard the phrase, "Very knock resistant" that just means there are no hot spots in the chamber to cause fuel mixture to detonate early.
That is really why I suggested upping the timing in little increments but without the right tools and without being in the absolute worst conditions you will ever encounter you can't say your setup is safe. This is why you will hear or see, new cars being tested in death valley, or other harsh conditions, they are literally doing this type of work for you and that is the safety factor Toyota decided on. 3* base timing. If you never see hot temps, never have heavy load, never have a heat soaked engine compartment, never get a batch of bad gas, than yes you can push it up.
But it appears that the timing being displayed by the scangauge is the total numbers of degrees advance, not just what the ECU is adding to the base setting. (See previous posts in this thread.) So if you are seeing 38* on your scan gauge and you have 3* base timing, then the ECU is adding 35* of advance. Of course this doesn't change the other points you made in your post, rather just what it is that OBD II is reporting.
No I don't agree with that. The scan gauge has no way of knowing what you set the base timing to.
I believe that people are confused that when they set their base timing and at 3* and the computer shows 3* that they are running a total timing of 6* degrees but just because the numbers are the same does not mean that they mean the same thing.
I believe that people are confused that when they set their base timing and at 3* and the computer shows 3* that they are running a total timing of 6* degrees but just because the numbers are the same does not mean that they mean the same thing.
Actually the ECU has the necessary sensors to know the approximate base timing. There's a crankshaft position sensor and the G1 and G2 sensors in the distributor, so it could determine how far the distributor has been rotated BTDC. To definitively say what the scangauge reports needs some more experimentation.
If that were the case, I would also expect that the computer could adjust to any timing it needs regardless of base timing but I know that isn't the case.
Just to clear this up:
prior to putting 'clip' in diag. portt my SG shows timing all over the place
the EXACT moment my 'clip' is inserted to the diag. port the SG reads exactly what my timing light says
I set my timing to 3* & SG reads a 100% constant 3*
I remove the 'clip' & my timing light still reads 3* but SG now reads a timing of 4+/38* throttle dependent.
Clear as MUD (IH8MUD)?
Gents, thanks in advance on any info... I'm not a cruiser expert yet but I'm learning.
I just completed a bunch of maintenance on a recently acquired 1995 FZJ80 with 214k on it. It took me a couple weeks working some nights here and there so it has been sitting. I finally got to firing it back up tonight and she starting without much hesitation, but ran rough. I didn't let it run for much more than a minute and then shut it down to go research some things. I then went back out to try again thinking that maybe it just needed to run for a while to get all the systems back to stable, but this time it wouldn't start. Battery is fine but it won't turn over.
The maintenance items I just completed:
- Oil change
- Drained the coolant system, currently has distilled water in it as I was about to perform the flush
- Replace main crank shaft seal
- Replace oil pump gasket
- Replaced the belts
- Change silicon grease in the fan clutch
- Replaced valve cover gasket
- Replaced valve plug seals
- Replaced dizzy O-ring
- Replace PCV valve and hose
- Cleaned the throttle body
- Replace the PHH
- Replaced the FHHs
My initial thought was timing, which I don't know a whole lot about it's symptoms. When I replaced the dizzy-O I was careful to turn the main crank such to align with the timing marks. I had the valve cover off so I was able to verify the timing dots as shown in the FSM. I then found the notch on the dizzy worm drive and aligned this as best I could. I could see it being 1-2 cogs off but not more. Would this produce my symptoms?
Any ideas would be much appreciated to help diagnose. My main thoughts are something with the timing or something connected to the throttle body, like the EGR or vacuum hoses.
Thanks,
Kyle
I just completed a bunch of maintenance on a recently acquired 1995 FZJ80 with 214k on it. It took me a couple weeks working some nights here and there so it has been sitting. I finally got to firing it back up tonight and she starting without much hesitation, but ran rough. I didn't let it run for much more than a minute and then shut it down to go research some things. I then went back out to try again thinking that maybe it just needed to run for a while to get all the systems back to stable, but this time it wouldn't start. Battery is fine but it won't turn over.
The maintenance items I just completed:
- Oil change
- Drained the coolant system, currently has distilled water in it as I was about to perform the flush
- Replace main crank shaft seal
- Replace oil pump gasket
- Replaced the belts
- Change silicon grease in the fan clutch
- Replaced valve cover gasket
- Replaced valve plug seals
- Replaced dizzy O-ring
- Replace PCV valve and hose
- Cleaned the throttle body
- Replace the PHH
- Replaced the FHHs
My initial thought was timing, which I don't know a whole lot about it's symptoms. When I replaced the dizzy-O I was careful to turn the main crank such to align with the timing marks. I had the valve cover off so I was able to verify the timing dots as shown in the FSM. I then found the notch on the dizzy worm drive and aligned this as best I could. I could see it being 1-2 cogs off but not more. Would this produce my symptoms?
Any ideas would be much appreciated to help diagnose. My main thoughts are something with the timing or something connected to the throttle body, like the EGR or vacuum hoses.
Thanks,
Kyle
You must now set it with a light.
Sent from my LG-LS970
Sent from my LG-LS970
I didn't move the TPS sensor at all. There's some loctight on the set screw so I know the position hasn't moved.
I inspected all the hoses this morning and couldn't find any vacuum issues, although I can't do any pressure testing when it's not running. I adjusted the throttle and accelerator cable a touch, but couldn't find much info on what the tension on those cables should be like. I adjusted the accelerator cable until the set screw had no clearance on the stop plate. This set screw also had locktight so I know it hasn't moved.
I was able to get it to start real briefly this morning and it died in about 3 seconds. Very low RPM.
I'm thinking the inability to start is not a timing issue. How far would the timing have to be off to result in a) won't start? b) runs noticably rough? How much would the timing be off if I was 1 cog off when I inserted the dizzy?
Thanks
I was able to get it to start real briefly this morning and it died in about 3 seconds. Very low RPM.
I'm thinking the inability to start is not a timing issue. How far would the timing have to be off to result in a) won't start? b) runs noticably rough? How much would the timing be off if I was 1 cog off when I inserted the dizzy?
Thanks
Locktite or marking paint?
Marking paint
Sooo, how do you adjust the timing on an FJ80? I have a '92, I live in Colorado, and would love to take this thing up to the mountains without feeling like I'm going to get smashed by a Semi
The timing mark is on the front of the flywheel, visible thru a small window on the front of the bell housing. Below and behind the dizzy.Sooo, how do you adjust the timing on an FJ80? I have a '92, I live in Colorado, and would love to take this thing up to the mountains without feeling like I'm going to get smashed by a Semi
Serious? Do I need a mirror or to get under the car or what? This sounds painful already. I looked back and under there, and am not seeing a window. Down by the starter?