Testing the HiRev 7500
- Thread starter Newbomb Turk
- Start date
-
mopowers
Well-Known Member
Should combine this with the CDI thread. Good related info in both.
Please let's don't and say we did. It's be a clusterfrig at this point.
Keep mine as long as you need it. I have several.
Mattax
Just the facts, ma'am
My coworker and mentor on all things engine tested the 505BC and the MSD 6 with a paper tape running through a spark. From those burns created he was convinced the autotronics could be used with large spark plug gaps (.045 - .060). Now as far as I can recall, these were open air tests but everything was compared the same way. This is the same guy, also named John, that ran in Stock classes that I mentioned before. He's the guy that told me never remove the big secondary spring from the distributor, because he had learned the hard way that in the electronic distributor it was neccessary.
Mattax
Just the facts, ma'am
It's amazing the legs some of these old "rules of thumb" have had.
There was a time. A time when points distributors were the norm, dual points were king, when tossing the heavy spring and running fast advance to a limit, could be the hot ticket to a little more power in the quarter mile.
The fact is that most magazine writers and even some speed part pushers couldn't, wouldn't and won't learn from the top racers and the go-fast operations at the big 3, err 4.
Guys who actually need results at high rpm know better, sometimes from hard experience.
As two of you posted here:
I don't see a big issue setting up a curve when the same triggering device is used, but the importance of getting beyond setting timing at "idle" and "all in" can not be overstated.
I've posted these before it but it will be good to do so again.
For racing at higher rpm the right curve for an electronic ignition has to take into account the slew rate. As mentioned above, my coworker who had been running stock eliminator had learned this the hard way when he removed the secondary spring from the Direct Connection tach drive distributor.
Tuner described the same lesson except it was with a GM.
"A-B-A-B it was faster with the GM dual-points distributor, even though the spark energy was higher with the electronic, a GM Magna-Pulse, and the electronic had the same “curve” except for the retard after the “total” was reached at 2500. Jenkins book “The Small Block Chevrolet Racing Engine” details the high-RPM curve and explains his reasoning"
And for those who like to experiment with computer simulations, I posted some locked timing, vs. basic ramped timing power comparisons using Dynomation 5. lets revisit timing post 41
There was a time. A time when points distributors were the norm, dual points were king, when tossing the heavy spring and running fast advance to a limit, could be the hot ticket to a little more power in the quarter mile.
The fact is that most magazine writers and even some speed part pushers couldn't, wouldn't and won't learn from the top racers and the go-fast operations at the big 3, err 4.
Guys who actually need results at high rpm know better, sometimes from hard experience.
As two of you posted here:
lets revisit timing
@RustyRatRod @Mattax Exactly. Welding the inside , extending the springs into more tension.. ...wtf is he thinking.lol so we want a slow curve? Putting the spring under tension and into its max resistance..uh no thanks. The outside is where you would close it up. Tony is a pants shitter No. I...
www.forabodiesonly.com
I don't see a big issue setting up a curve when the same triggering device is used, but the importance of getting beyond setting timing at "idle" and "all in" can not be overstated.
I've posted these before it but it will be good to do so again.
MP setup their race distributors (aka tach drive distributors) for easy starting and to maintain high rpm timing flat or very slightly advancing. (graphed here) They basically accepted idle timing as somewhat unstable because they didn't think it was that important - at least relative to the other two goals (easy starting and top rpm performance).
The reasons to put a curve in the distributor are twofold.
1. It will likely allow the engine to run richer and stronger at idle. The better it runs at idle rpms then the less time for the carb to clear up when throttle is opened.
2. The top end should continue advancing mechanically so as to avoid the retard that comes naturally with most electronic ignitions. (If running dual points then not needed.)
As illustrated in the two videos posted here. lets revisit timing
Mallory Unilite timing issue
The delay is in the electronics themselves such as an msd box or the orange Mopar box Different brands have different delay. Example, pertronix has about a 2 degree delay @ 5,000 rpmMsd has a 4 degree delay @ 5,000 rpm so you can curve the distributor to counter act the delay.Orange Mopar ...board.moparts.org
For racing at higher rpm the right curve for an electronic ignition has to take into account the slew rate. As mentioned above, my coworker who had been running stock eliminator had learned this the hard way when he removed the secondary spring from the Direct Connection tach drive distributor.
Tuner described the same lesson except it was with a GM.
"A-B-A-B it was faster with the GM dual-points distributor, even though the spark energy was higher with the electronic, a GM Magna-Pulse, and the electronic had the same “curve” except for the retard after the “total” was reached at 2500. Jenkins book “The Small Block Chevrolet Racing Engine” details the high-RPM curve and explains his reasoning"
And for those who like to experiment with computer simulations, I posted some locked timing, vs. basic ramped timing power comparisons using Dynomation 5. lets revisit timing post 41
Mattax
Just the facts, ma'am
Bill Jones posted some of his tests of timing retard in this thread.
He's calling it hysterisis. The phenomenon is the same even if at that point he didn't know the full cause.
And here in the middle of hte page he describes how the factory (GM) compensated for slew in the distributor.
More discussions on slew.
and this one with some of the 'retard built in' history bubbling into the light.
He's calling it hysterisis. The phenomenon is the same even if at that point he didn't know the full cause.
And here in the middle of hte page he describes how the factory (GM) compensated for slew in the distributor.
More discussions on slew.
and this one with some of the 'retard built in' history bubbling into the light.
Lol, this gentleman tested my ignition system.
Took quick notes and figured out what we needed to do with weights and springs to make it work better with my ignition box.
Funny how people can do things and not do it how you said was the only way.
No, you need to post pictures from David vizards books and he'd understand you lol
We've literally talked about this on here for YEARS. It's been in nearbout every major magazine and publication at some point that these boxes do retard timing. I've seen several on a distributor machine do it myself. Now, I've never seen anyone test "just" a box, but from all the evidence, that's where it's coming from. I mean you can "see" a point ignition doesn't do it. That should tell you something.
He tested 3 different msd boxes of mine and 2 distributors and they all had varying degrees of retard. That says to me the tester isn't incorrect.
Right!
Newbomb Turk
Well-Known Member
Reading through those is amusing and sad.
This has been known for decades and there are people that argue this to the death and they still get it wrong.
In thinking about it today, the electronics in my machine have to be at least as fast or faster than any box I’ve tested because with points I see zero retard. At really high RPM I might see a degree of retard but I don’t know if you can blame the points for that retard, the machine or if it’s just the nature of the electronics.
If the electronics were slow it would show up in the points too wouldn’t you think?
It’s not cam walk. It can be an issue with timing but that’s a different symptom. And what about the Chrysler small block and the Fords that use a cam retaining plate? That’s a bit of a bugger there.
The shitty GM advance and the sloppy way they drive the distributor certainly contributes to spark scatter but that is not part of the equation on a test bench.
Timing chain slop is another phenomenon that gets thrown around when timing retard happens. Again, this contributes to spark scatter but there is no timing chain on the test bench so that’s a non factor as well.
Guys that use very light springs to get the all in timing as quick as they can exacerbate spark scatter all the more with those light springs.
At idle speed the pulsations of each cylinder firing actually causes the crank to slow down and speed up. This makes the timing jump around at idle. That’s why most clutch discs have springs in the hub. To absorb those pulses and eliminate or at least reduce what some call clutch chatter to a minimum.
Combine that with a timing chain, the shitty GM advance mechanism and the way GM drives the pump it’s no wonder spark scatter is real.
It’s time people start learning this and fixing the real issues so the engine they paid all that money is at least making the best power as it can.
Distributor were msd also
Okay, for us dummies who are struggling to understand this, tell me if this is correct. The timing retard on all these boxes doesn't really become significant until high rpms. 7,000, 7,500, etc. For a motor that only goes to 5500-6,000, it is not a significant problem.
Right? Or have I completely lost my way?
Right? Or have I completely lost my way?
I think it starts retarding much earlier = perhaps
3000 or 3500.
3000 or 3500.
That's about where mine would start.
I'm not saying that boxes don't retard but I have seen timing retard go from 6ish degrees of retard to 1ish degree with the same box and two different types of distributors. On running engines not a distributor machine. I don't know for sure but I think the results will be the same on a distributor machine. Most test including this one are done with the same type of distributor. Self generating ac signal.
Kind of the opposite in my experience. Most of the retard comes below 4000ish and less above that. I don't know why that is. It seems like it should be linear. I don't test very many engines above 7500 .
I absolutely agree 100% that with some cases, there's more than the box in play. No doubt about it. But the only way to know it to TEST!
It depends on the type box and how crappy it is. Some actually have high RPM retard designed it to help protect against detonation at high RPM.
Dave999
Well-Known Member
all very interesting
you weren't as shouty and angry as i expected
..... some might say "real life" affable.. in fact
probably explains why the advance curve set in a points distributor from the factory differs so from the curve in an electronic...
they chose which compromise they wanted to live with,
mechanical switch that wears out, burns out, limits current and involves some owner skill to replace and set up or 2 of them that takes even more skill to set up
or
an electronic switch where the timing varied in what was probably, with one manufacturer and a known supplier of parts, a predictable way, that could be masked by a different curve...on a system that involved less skill to set up.... 1 brass feeler gauge and a light.
after all doesn't matter what happens before as long as the spark arrives at the right time
cost of support and ease of ownership won out...
its all linked to the current in the primary and the coil used...higher current, the faster coil gets to max flux, the shorter dwell needed, the higher rpm or greater no of cylinders supported. trouble is you have to switch that current and too much will wreck your switch.
i remember arguing with a fella who insisted a coil with a primary made from solid copper would be great, think of the current said he...!....
A slight misunderstanding or transformer theory was leading him way way down the wrong path
Dave
you weren't as shouty and angry as i expected
..... some might say "real life" affable.. in factprobably explains why the advance curve set in a points distributor from the factory differs so from the curve in an electronic...
they chose which compromise they wanted to live with,
mechanical switch that wears out, burns out, limits current and involves some owner skill to replace and set up or 2 of them that takes even more skill to set up
or
an electronic switch where the timing varied in what was probably, with one manufacturer and a known supplier of parts, a predictable way, that could be masked by a different curve...on a system that involved less skill to set up.... 1 brass feeler gauge and a light.
after all doesn't matter what happens before as long as the spark arrives at the right time
cost of support and ease of ownership won out...
its all linked to the current in the primary and the coil used...higher current, the faster coil gets to max flux, the shorter dwell needed, the higher rpm or greater no of cylinders supported. trouble is you have to switch that current and too much will wreck your switch.
i remember arguing with a fella who insisted a coil with a primary made from solid copper would be great, think of the current said he...!....
A slight misunderstanding or transformer theory was leading him way way down the wrong path
Dave
Last edited:
The next test should be a Pertronix I.. I want to see no spark scatter at 11,000.all very interesting
you weren't as shouty and angry as i expected
probably explains why the advance curve set in a points distributor from the factory differs so from the curve in an electronic...
they chose which compromise they wanted to live with,
mechanical switch that wears out, burns out, limits current and involves some owner skill to replace and set up or 2 of them that takes even more skill to set up
or
an electronic switch where the timing varied in what was probably, with one manufacturer and a known supplier of parts, a predictable way, that could be masked by a different curve...on a system that involved less skill to set up.... 1 brass feeler gauge and a light.
after all doesn't matter what happens before as long as the spark arrives at the right time
cost of support and ease of ownership won out...
Dave
Dave999
Well-Known Member
well if thats just the magnetic collar and pickup styleThe next test should be a Pertronix I.. I want to see no spark scatter at 11,000.
you get you points based curve
with a different type of switch, it will indeed have a different switching speed. points do suffer from arching....
any variance at high RPM will probably be mechanical... vibration in the drive due to crank/cam flex or flapping timing chain. how much or little impact that has dunno.
distributor machine will be a nice environment, to work in, But with your distributor drive stuck into a motor, its not a nice environment what you see in test situation and what you get in real life could differ
With the basic petronix you are limited to a coil with a ballast resistor you are limited to approx 3 amps in the primary
is there enough time to "charge Up" that coil at a "points based" 3 amps to make a decent spark at that 11,000 RPM
probably not, 6000 yeah, 11000 not so sure. A spark at atmospheric pressure and just damp air, ain't necessarily a spark in a combustion chamber at 11:1. You'd have to rip the electrons off 11 times more molecules of air and fuel to get the spark to propagate across the gap. potentially 11 times harder than with a spark plug earthed to a testing rig....(although i bet its not a linear relationship, i dunno)
Last edited:
I thought it would be interesting to see what rpm it is capable of before it can't keep up. Points, magnetic, or optical triggered? Which is best for RPM? Any of those should work well for the majority of us up to 5,000 or may be 6.well if thats just the magnetic collar and pickup style
you get you points based curve
with a different type of switch, it will indeed have a different switching speed. points do suffer from arching....
any variance at high RPM will probably be mechanical... vibration in the drive due to crank/cam flex or flapping timing chain. how much or little impact that has dunno.
distributor machine will be a nice environment, to work in, But with your distributor drive stuck into a motor, its not a nice environment what you see in test situation and what you get in real life could differ
With the basic petronix you are limited to a coil with a ballast resistor you are limited to approx 3 amps in the primary
is there enough time to "charge Up" that coil at a "points based" 3 amps to make a decent spark at that 11,000 RPM
probably not, 6000 yeah, 11000 not so sure. A spark at atmospheric pressure and just damp air, ain't necessarily a spark in a combustion chamber at 11:1. You'd have to rip the electrons off 11 times more molecules of air and fuel to get the spark to propagate across the gap. potentially 11 times harder than with a spark plug earthed to a testing rig....(although i bet its not a linear relationship, i dunno)
-
