Another possibility is that he may have changed how he feels since he wrote that.
Timing
- Thread starter Ironmike
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I don't know. Seems plausible.
Mattax
Just the facts, ma'am
Exactly.
No.
Click on the link and read the rest of the post.
racingfuelsystems-Too much advance at light throttle?
What happens if there is too much timing advance under cruise or engine braking? Will there still be detonation? Will it simply misfire? I ask because
www.tapatalk.com
and then go to post 45 referring back to the 4440 cid A134 timing specs I post and graph in posts 42-44.
A couple of points to remember here. I started that thread asking about vacuum advance setup. We then sidetracked into the race distributor, which was a drag race setup. A drag race only engine is never heat soaked like a sports car, circle track or street engine will get. Furthermore when just tooling around, on and off the trailer, return road, or even street driven, the engine is not going to be heavily loaded at 2000 or 2500 rpm. This is why we can generally get away with so much mechanical advance in this rpm range when there is no vacuum advance.
Swinger 340
Well-Known Member
I always did my timing set by ear on my van. I installed a 69' 340 in the 72' van and used all the 72' items on the motor, to look like a stock motor. The problem was, I lost the timing marks, due to the water pump was opposite and hid the timing cover marks. It was easy to set that way because I could adjust with the cover off the motor and me sitting inside to adjust the sweet spot.
Will do.
lol it’s funny you mention the cut down oil pumps. I have one I saved from the first W2 engine I bought.
It had what I suspect was the oiling system most SS guys were using back in the day.
If I was going to turn one of these engines 8500 plus again, I would go back to exactly how that engine was plumbed.
I hit 9k many times and never got a bearing from lack of oil.
That’s possible. I need to call him so I’ll ask him.
I may do it tonight but probably tomorrow.
I’ve felt like crap so I haven’t talked to him in a few weeks.
I have to have my thinking cap on when talking to Tuner.
And I usually take notes.
Mattax
Just the facts, ma'am
Sometimes we can't get that very slow increase in ignition advance from mid to high rpm. The question is how much effort (and sometimes $$$) is someone willing to put in to get the last bit of performance.
The top green line with black dots is what the Dynomation 5 spit out as the 'ideal' timing for a 340 with a cam that has roughly 223/230 duration .505 lift.
The lower green line I developed by reducing the timing every 500 rpm until the power at that rpm was about 5% less than Dynomation showed as 'ideal". Then I ploted it on the graph and repeated for the next higher rpm.
Red lines are timing measured on the real engine that pinged mid rpm under some conditions (not drag strip). The underlying issue was a tighter torque converter. Another way to look at it is the lower stall rpm revealed the flaws in the timing and fuel tuning.
Dynomation was created by Larry Atherthorn based on lots of dyno information. I don't know what else went into it, but I suspect the Fill and Empty model may be based more on emperical data and the flow model may be more fluid dynamics and physics. My version is 5.0 and there are newer versions available. On a street car or endurance racer I would sneak up on any timing numbers suggested as 'ideal' by a program based mostly on dyno and drag strip.
Along the same lines, here's simulations of a stock 340 (maybe with headers, I forget) using flat timing versus am 'ideal' curve.
Advance altered so its 30* at 2900 rpm increasing to 36* at 4000 rpm, then flat through redline.
This is the sort of linear advance one might have to do with distributor that can't be shaped like a Chrysler can be.
The top green line with black dots is what the Dynomation 5 spit out as the 'ideal' timing for a 340 with a cam that has roughly 223/230 duration .505 lift.
The lower green line I developed by reducing the timing every 500 rpm until the power at that rpm was about 5% less than Dynomation showed as 'ideal". Then I ploted it on the graph and repeated for the next higher rpm.
Red lines are timing measured on the real engine that pinged mid rpm under some conditions (not drag strip). The underlying issue was a tighter torque converter. Another way to look at it is the lower stall rpm revealed the flaws in the timing and fuel tuning.
Dynomation was created by Larry Atherthorn based on lots of dyno information. I don't know what else went into it, but I suspect the Fill and Empty model may be based more on emperical data and the flow model may be more fluid dynamics and physics. My version is 5.0 and there are newer versions available. On a street car or endurance racer I would sneak up on any timing numbers suggested as 'ideal' by a program based mostly on dyno and drag strip.
Along the same lines, here's simulations of a stock 340 (maybe with headers, I forget) using flat timing versus am 'ideal' curve.
Advance altered so its 30* at 2900 rpm increasing to 36* at 4000 rpm, then flat through redline.
This is the sort of linear advance one might have to do with distributor that can't be shaped like a Chrysler can be.
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That looks like about 21 degrees at idle and then the curve increases timing well past 6k.
I can buy a curve like that one. It may be a bit quick if you are going above 7500 but that’s a nice curve.
Well I hope you get to feelin better. You look like crap too though and nothing can help you "THERE".
I'm going to try this curve in my MSD grid next season. Could you plot a curve for different CI and compression with your software or is that something in "Larry's" wheelhouse?
Mattax
Just the facts, ma'am
Thanks! I can that.
It can be hard to get good digital photos of printed material.
It says pretty much as suspected. The upper line is what they were measuring on the Sun or Allen. At the time they attributed the difference between the timing machine and perhaps what they what they measured on the engine to the timing chain. Compared to the vacuum advance distributor, they were going from a base timing to allow an easy start, and perhaps also using more timing at high rpm. Mechancial advance on the vac advance equiped distributor was intended to begin above idle rpm.
Mattax
Just the facts, ma'am
I don't know how sophistcated the program is. It will show a similar timing curve for a similar engine. Just looking at the two 340 examples we can see the 'ideal' timing is pretty similar. I recall trying to see if the model could adjust for different rod stroke and there was no change. Yet we know changing dwell time of the piston at the top should effect timing needs.
You could post up or e-mail (through my webpage) the specs and I could plug it in. it might not be today or tommorrow, but sometime in the next couple weeks.
@TT5.9mag has posted some timing tables for magnum 360s (5.9s) and for the B and RB engines I think the stuff Tuner posted in that other forum as well as the factory curves from the mid 60s are all good starting points.
We might not be on the same page. The chart below is what I'm referring to. The part of the chart I would call the curve in this case is from 500 rpm to 7000 rpm. The top part of the curve is what I would call the curve as seen on the distributor machine. To me the bottom flat curve represents what the top curve will look like when measured on the running engine with losses incurred from the timing chain etc. For the sake of this discussion I'm going to say this was originally intended for points distributor. I think most would agree 3 degrees over 7000 rpm would not be enough advance to cover up the loses incurred from a mopar electronic ignition system plus the mechanical losses. If it was then this chart doesn't make sense to me. That bottom flat curve is what I think tuner is referring to as a "flat static total." he goes on to say "or continue to advance all the way through the RPM range, however the engine likes it and you set it up.". I take that to mean if the engine wants more than a flat curve then give it what it wants. I think it's safe to say that this is a race curve intended for a race engine. If what you mean by all engines want a curve including points and you are referring to the top curve as seen on a distributor machine resulting in a flat curve as seen on the engine then I would likely agree with that. If you referring street cars when you say they all need a curve I would mostly agree to that. If what your saying is that if you have a flat timing curve as measured on the engine (race engine) it's always going to lose significant power compared to having a curve that is not flat I would disagree.
To me the flat “curve” isn’t a curve at all. It’s locked out for all intents and purposes.
So Im saying a “race” engine with the bottom curve will benefit from a curve like crazy.
And, when building the curve you have to account for the slew rate.
What you see in the car (or on the dyno) should be the exact SHAPE that you built into the distributor. The numbers may not be the same, but the SHAPE of the curve is always the shape of the curve.
I do not know how a race engine has different timing needs than any other engine needs. It’s physics.
Not all engines have the same timing needs. If they did then every engine would have the same curve. There are an infinite number of varibles that will ultimately determine what the engine wants for timing. Not all engines get what they want. Sometimes constraints such as rules, budget, patrs availability, fuel etc. Will force a safe real world compromise.
Mattax
Just the facts, ma'am
We are on exactly the same page. The graph is a later version of this one
It is in reference to breakerless distributors, which have been available from DC since at least 1975.
It says they are recommending a slow advance illustrated by the shaded area.
They are describing what they have been observing from their dyno work. That they don't seem to fully know why it is better than a flat line (the previous acccepted settup for racing) is clear by how they write it. They don't say just for electronic distributors. The engine doesn't care whether its electronic or points. It does care if the timing is diverging too far from ideal.
I show you that when the MP/DC race distributor is run on a Sun machine with a Sun convertor, or an engine of mine with an MSD 6T the timing is flat or nearly flat. It does not retard. The weights on that distributor are not hitting the end of the governer's slots at 2000, 3000 rpm, or 4000 rpm.
If the ECU has faster electronics, or has a circuit thats more predictive so it negates the slew, then the timing will slightly increase as shown in the shaded area. That's a good thing and will be to our advantage on a high rpm engine.
What is the 'real' curve if there was no 'slew'?
We don't know and I don't see why it matters.
The curve that matters is what the engine sees with whatever measurement tools we use to document it. If we use a Sun machine, that's fine. If there is a difference between the machine and our timing light, then we take that into account.
If I make a pass and think there is detonation and want to back off, what do I do? Besides looking at a couple plugs if there is time, I check the timing at some rpm, THEN turn the distributor and check the timing again at the same rpm as before. I'm not going to pick an unstable rpm to take that measurement. Right? I'm going to pick 2800 or 3000 rpm if possible. If I'm using a dialback instead of timing tape I'm going to use the same light before and after.
I care about timing at idle. So that's why I want to document the whole curve. I also think that we've advanced a bit since the mid-70s and having half decent idle can help even a dedicated race engine. No reason to have to wait to have an engine clean up when giving it throttle.
It is in reference to breakerless distributors, which have been available from DC since at least 1975.
It says they are recommending a slow advance illustrated by the shaded area.
They are describing what they have been observing from their dyno work. That they don't seem to fully know why it is better than a flat line (the previous acccepted settup for racing) is clear by how they write it. They don't say just for electronic distributors. The engine doesn't care whether its electronic or points. It does care if the timing is diverging too far from ideal.
I show you that when the MP/DC race distributor is run on a Sun machine with a Sun convertor, or an engine of mine with an MSD 6T the timing is flat or nearly flat. It does not retard. The weights on that distributor are not hitting the end of the governer's slots at 2000, 3000 rpm, or 4000 rpm.
If the ECU has faster electronics, or has a circuit thats more predictive so it negates the slew, then the timing will slightly increase as shown in the shaded area. That's a good thing and will be to our advantage on a high rpm engine.
What is the 'real' curve if there was no 'slew'?
We don't know and I don't see why it matters.
The curve that matters is what the engine sees with whatever measurement tools we use to document it. If we use a Sun machine, that's fine. If there is a difference between the machine and our timing light, then we take that into account.
If I make a pass and think there is detonation and want to back off, what do I do? Besides looking at a couple plugs if there is time, I check the timing at some rpm, THEN turn the distributor and check the timing again at the same rpm as before. I'm not going to pick an unstable rpm to take that measurement. Right? I'm going to pick 2800 or 3000 rpm if possible. If I'm using a dialback instead of timing tape I'm going to use the same light before and after.
I care about timing at idle. So that's why I want to document the whole curve. I also think that we've advanced a bit since the mid-70s and having half decent idle can help even a dedicated race engine. No reason to have to wait to have an engine clean up when giving it throttle.
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I didn’t say all engines need the same curve. I say they all need a curve.
Can you pick out one or two situations where maybe Thats not the case? Sure. But in any case a curve will not lose power.
Edit: I didn’t pay enough attention to it, but I’ve had several 408’s on the dyno and they don’t all take the same curve. The biggest difference is cam timing.
Since cam timing affects VE that would make sense.
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I find it hard to believe they didn’t understand slew rate back then.
I have not seen a timing chain or anything else like they say above cause retard.
Spark scatter? I see that like a mother. It’s nasty. In fact, it’s probably FAR worse spark scatter than we see with many timing lights that use suppression and digital stuff like that to clean up scatter.
The best thing to clean up spark scatter is a crank trigger. But, IMO it’s just as bad as locked out timing because you can’t do a curve with it unless you have a programmable ignition. A crank trigger and programmable ignition are the best bet to eliminate spark scatter.
The next best thing is a QUALITY gear drive. Many might be surprised at how much a good gear drive cleans up spark scatter.
I gave you an example of an engine with a flat curve that didn't need or want a curve that I dynoed.
Mattax
Just the facts, ma'am
Pretty much. A drag race engine will run colder than most others but other than that its the same.
Hmm. If the top line represents the timing curve as measured on the running engine. What does the bottom flat line represent?
Ok, there ONE. And I’d say it’s very rare.
Plus, I don’t Remember how you tested your curve or how you developed it. I’ve said it before but I’ll say it again.
Trying to develop a timing curve doing sweeps won’t cut it. I know you disagree with that statement but it’s a fact. You might get it close.
If you just pick a curve based on the same engine family and tune from there you have no idea what MBT timing really is.
Without that the curve is just a guess.
You’d be surprised (maybe not) at how many hard headed dudes there are out there. They claim they’ve tried every curve in the book and their **** is quicker and faster locked out or close to it.
That just flies in the face of known physics. It doesn’t work that way.
I’ve asked you to explain (in relatively simple terms) how an engine wants MORE timing at peak VE and LESS timing at peak power (lower VE) because that is the basis for the argument against a curve.
Physics says less timing at peak VE (torque) and more timing with less VE. That hasn’t changed.
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