Topic: Shout-out to Ignitech ignition systems

[scottly]

The full advance hash marks on the stock 750 are at 34 and 36 degrees, for a nominal advance of 35 degrees, all in at around 2500 RPM.

Are you sure?

I have this info:

Yes, I am sure. This is from the Honda manual:

[scottly]

You guy's have a long way to go as there is a whole new world that is untapped when you continue following the norm and staying with 2D. This is what has been discussed the postings to date and on this thread other than being mentioned very briefly in the very first post (TPS).  This is absolutely fine and the way to go for drag racing but for any street or track use then you are leaving part throttle performance on the table unless you adopt 3D. 

The discussion thus far has been related to WFO throttle in a racing application. If by "3D" you mean using manifold vacuum to increase timing at part throttle, cruising situations, it's been used for decades on automobiles before they had computers. 44 degrees advance is not out of line in these conditions. Who knows, maybe my 836 with Weber carbs could exceed the 60+ MPG it has regularly recorded at 55-60 MPH part throttle conditions with a manifold pressure referenced ignition advance?
Captain Weber. 

[seanbarney41]

You guy's have a long way to go as there is a whole new world that is untapped when you continue following the norm and staying with 2D. This is what has been discussed the postings to date and on this thread other than being mentioned very briefly in the very first post (TPS).  This is absolutely fine and the way to go for drag racing but for any street or track use then you are leaving part throttle performance on the table unless you adopt 3D. 

The discussion thus far has been related to WFO throttle in a racing application. If by "3D" you mean using manifold vacuum to increase timing at part throttle, cruising situations, it's been used for decades on automobiles before they had computers. 44 degrees advance is not out of line in these conditions. Who knows, maybe my 836 with Weber carbs could exceed the 60+ MPG it has regularly recorded at 55-60 MPH part throttle conditions with a manifold pressure referenced ignition advance?
Captain Weber. 

lol, Chevy small block HEI distributor...a whole new world!

[Captain]

Yes the discussion has been (until now) about WFO throttle but there is more time spent at positions other than that.  Manifold vacuum was one very crude way of doing this as there was no other practical way of doing it and long before electronics arrived........Also what I am talking about has nothing to do with Chevy HEI distributors.  Forget for a minute the increases in mileage and concentrate on the other aspects, more part throttle power and lower waste heat. These you feel as an increase in torque at any given part throttle position.  The bike feels and is more powerful than one without it.............. Plain and simple.   
 The problem with vacuum was it cannot react fast enough nor with anything approaching accuracy in a fast moving engine and could be best described as taking a mallet to the problem as although it is an answer it is very crude unlike the input from a TPS (Throttle Position Sensor) 
With the development of fast acting ECU's and the speeds that could be processed then 3D became a very valuable tool in the total mapping of all positions and conditions.
 None of this was around when these bikes were manufactured and didn't really start appearing until the late 90's early 2000's in motorcycles. The thing is that when you apply this tech back to these 70-80's era of bikes then a whole new area of part throttle performance appears.
 I have done this with our 82 roadrace Superbike and the positive changes were too good to dismiss and dramatically so in some areas and as a result of this I would never build another without including this feature.

 Captain

[livefast_dieold]

The full advance hash marks on the stock 750 are at 34 and 36 degrees, for a nominal advance of 35 degrees, all in at around 2500 RPM.

Are you sure?

I have this info:

Yes, I am sure. This is from the Honda manual:

Interesting, my reference is from an Honda manual too...
Your figure makes more sense though.

[livefast_dieold]

Yes the discussion has been (until now) about WFO throttle but there is more time spent at positions other than that.  Manifold vacuum was one very crude way of doing this as there was no other practical way of doing it and long before electronics arrived........Also what I am talking about has nothing to do with Chevy HEI distributors.  Forget for a minute the increases in mileage and concentrate on the other aspects, more part throttle power and lower waste heat. These you feel as an increase in torque at any given part throttle position.  The bike feels and is more powerful than one without it.............. Plain and simple.   
 The problem with vacuum was it cannot react fast enough nor with anything approaching accuracy in a fast moving engine and could be best described as taking a mallet to the problem as although it is an answer it is very crude unlike the input from a TPS (Throttle Position Sensor) 
With the development of fast acting ECU's and the speeds that could be processed then 3D became a very valuable tool in the total mapping of all positions and conditions.
 None of this was around when these bikes were manufactured and didn't really start appearing until the late 90's early 2000's in motorcycles. The thing is that when you apply this tech back to these 70-80's era of bikes then a whole new area of part throttle performance appears.
 I have done this with our 82 roadrace Superbike and the positive changes were too good to dismiss and dramatically so in some areas and as a result of this I would never build another without including this feature.

 Captain

Hey Captain,

the ignition can handle 3D, the only problem is that in the class I'm competing, you can't use any other information to determine advance but engine rpm; so no TPS and no intake pressure sensors. Basically 3D advance is prohibited; that's why I was not even mentioning it.

[PeWe]

Advance need to come earlier on a street bike? I have std advancer with tightened springs, full advance around 2600-2700 rpm.
I have another advancer to use with std springs. 1005cc, DP315 cam, ported head, TMR32 etc.

It stumbles a little between 2000-3000 rpm, after that good torque.
Edit: The other advancer did not remove it.That was too rich needles, lowered 1 step more fixed it.

[HondaMan]

Pewe, that link you provided had some erroneous information about the heat range of a spark-plug being related to the heat dissipation of the ground strap through the plug body and then the cylinder head. The heat range of a spark plug is related to the heat dissipation of the ceramic around the center electrode through the plug body.
The old technique of advancing until pinging was heard, then backing it off a bit was called "power timing"; if the motor pings at any point, you're losing power, as well as risking damage. Some drag racers back in the day of dual-point distributors found that their cars went slightly faster when they retarded the timing a bit near the end of the quarter mile. The theory was that in high gear with more wind resistance, the load and cylinder pressures were much greater than at the start of the race in 1st gear and zero wind resistance.
Today, the best way to determine optimum advance would be on a dyno, with a bit of trial and error.
Riccardo, what kind of fuel are you using?       

You're right-on, Scottly...
Way back when, we discovered the 750 can indeed run 14000 RPM, with little more than lightening the retainers, sandblasting the OEM springs (i.e., the early straight-wound ones, not the post-1972 progressive-wound ones), adding some guide clearance (0.0004" extra over Honda's max, or 0.0020") and glass-polishing the stems, and then make the spark advancer "slow down" about 4-5 degrees between about 11,500 and 12,000 RPM. Above that, it seemed like the only thing stopping it was loss of compression. The guys doing this were using the engine, sans transmission, in midget-racer cars. The spark advancer was a marvel, 2 levels of spring advancers, with 2 little tapered (wasp-waisted) shafts on the upper one that pushed down through the lower one, to push the weights backward those few degrees while the engine ran past the 'stall point', as they called it then. One guy was running to 16000 RPM, but he didn't seem to have any more power than the others who were reaching to 14,000.

Of course, there were some other mods, but the guys who ran to "only" 12,000 RPM were doing it with the OEM K0 cams, retarded by their own magical number of degrees. The other ones (14k+ RPM) were making their own cams, so I don't know their dwell numbers. All of the 12k racers used stock round-top carbs that were bored 2mm thru the middle, removing the wasp-waist in the throat. The 16k guy had a 4bbl Weber with his own manifold. The 14k guys used Mikunis or Honda 450 CV carbs.

[MRieck]

Yes the discussion has been (until now) about WFO throttle but there is more time spent at positions other than that.  Manifold vacuum was one very crude way of doing this as there was no other practical way of doing it and long before electronics arrived........Also what I am talking about has nothing to do with Chevy HEI distributors.  Forget for a minute the increases in mileage and concentrate on the other aspects, more part throttle power and lower waste heat. These you feel as an increase in torque at any given part throttle position.  The bike feels and is more powerful than one without it.............. Plain and simple.   
 The problem with vacuum was it cannot react fast enough nor with anything approaching accuracy in a fast moving engine and could be best described as taking a mallet to the problem as although it is an answer it is very crude unlike the input from a TPS (Throttle Position Sensor) 
With the development of fast acting ECU's and the speeds that could be processed then 3D became a very valuable tool in the total mapping of all positions and conditions.
 None of this was around when these bikes were manufactured and didn't really start appearing until the late 90's early 2000's in motorcycles. The thing is that when you apply this tech back to these 70-80's era of bikes then a whole new area of part throttle performance appears.
 I have done this with our 82 roadrace Superbike and the positive changes were too good to dismiss and dramatically so in some areas and as a result of this I would never build another without including this feature.

 Captain

Do you make your own TPS or use a unit like on Keihin FCR's? Or something off an EFI bike and modify it?

[Captain]

 Store brought $20  and self made mounting bracket. As pictured with the red arrow.


 Captain

[livefast_dieold]

Pewe, that link you provided had some erroneous information about the heat range of a spark-plug being related to the heat dissipation of the ground strap through the plug body and then the cylinder head. The heat range of a spark plug is related to the heat dissipation of the ceramic around the center electrode through the plug body.
The old technique of advancing until pinging was heard, then backing it off a bit was called "power timing"; if the motor pings at any point, you're losing power, as well as risking damage. Some drag racers back in the day of dual-point distributors found that their cars went slightly faster when they retarded the timing a bit near the end of the quarter mile. The theory was that in high gear with more wind resistance, the load and cylinder pressures were much greater than at the start of the race in 1st gear and zero wind resistance.
Today, the best way to determine optimum advance would be on a dyno, with a bit of trial and error.
Riccardo, what kind of fuel are you using?       

You're right-on, Scottly...
Way back when, we discovered the 750 can indeed run 14000 RPM, with little more than lightening the retainers, sandblasting the OEM springs (i.e., the early straight-wound ones, not the post-1972 progressive-wound ones), adding some guide clearance (0.0004" extra over Honda's max, or 0.0020") and glass-polishing the stems, and then make the spark advancer "slow down" about 4-5 degrees between about 11,500 and 12,000 RPM. Above that, it seemed like the only thing stopping it was loss of compression. The guys doing this were using the engine, sans transmission, in midget-racer cars. The spark advancer was a marvel, 2 levels of spring advancers, with 2 little tapered (wasp-waisted) shafts on the upper one that pushed down through the lower one, to push the weights backward those few degrees while the engine ran past the 'stall point', as they called it then. One guy was running to 16000 RPM, but he didn't seem to have any more power than the others who were reaching to 14,000.

Of course, there were some other mods, but the guys who ran to "only" 12,000 RPM were doing it with the OEM K0 cams, retarded by their own magical number of degrees. The other ones (14k+ RPM) were making their own cams, so I don't know their dwell numbers. All of the 12k racers used stock round-top carbs that were bored 2mm thru the middle, removing the wasp-waist in the throat. The 16k guy had a 4bbl Weber with his own manifold. The 14k guys used Mikunis or Honda 450 CV carbs.

Interesting, what was the maximum advance before the stall point?

[PeWe]

The full advance hash marks on the stock 750 are at 34 and 36 degrees, for a nominal advance of 35 degrees, all in at around 2500 RPM.

Are you sure?

I have this info:

Yes, I am sure. This is from the Honda manual:

Interesting, my reference is from an Honda manual too...
Your figure makes more sense though.

I opened my Honda CB750 shop manual to verify the piston ring gap for the std 61mm pistons (K2 project has started)
I found the same ignition data: 6°@ 1000rpm, 40° @2500 rpm. I checked both my from Internet downloaded copy and the new printed paper version I have.
I'll check and adjust my ignition @2500 rpm next time = max advance. Need to do before dyno and hopefully get some more ponies after 8000 rpm.

[MRieck]

Store brought $20  and self made mounting bracket. As pictured with the red arrow.


 Captain

My condolences on having to use CR carbs. Is that a quick fill valve for oil? i see MSD wires, O2 sensor, the old AHM cover....memories right there. I have stories of AHM buying a lot of Del West valves etc and pissing through Honda money.....funny.

[scottly]

I mounted a K7 advance plate on a rotary table and verified the marks: the F mark is 10* from the T mark, the first full advance hash mark is 33.5* from the T mark, the second hash mark is 36.5*, and in the middle of the hash marks is 35*. I also compared the mark spacing on an installed K1 unit, and found them to be the same. Was there a specific year for the 40* spec, like the "K0"?
 

[PeWe]

Hondaman where are you?!
Anyone that can lit the batman lamp?
The different CB750 advancers and ignition timings is a part of his expertise.
I think I have read that earlier CB750 had more advanced timing.

Then came EPA and cut the balls of the CB750.....right?

Found one thread where different advancers and timing are discussed. Scroll down a little and find another Hondaman post
http://forums.sohc4.net/index.php/topic,113338.msg1275351.html#msg1275351

Edit: I read more in the same manual. The later bikes got 10° vs 35° in Supplement to K7, K8, F2.

[HondaMan]

Was there a specific year for the 40* spec, like the "K0"?
 

Yes, exactly.
There are as many advance angles in the 750 as advancers made for the engine, I'm afraid...My K2 is 6 x 32 degrees, according to my crank degree wheel. My original K1 was 6 x 35 degrees, and my friend Jim's K0 sandcast was 6 x 41 degrees, in between the 2 advance marks. The 10-degree starting point first appeared, IIRC, in the K4 engines that ran on Regular gas instead of Premium. They may have been in some of the K3, but I didn't catch any of those in my own notes, if they did.

The one thing I did also notice was: the advancers with larger backing plates (usually TEC) all started at 10 degrees. These were on the bikes that idled at 1100 RPM, instead of the earlier 950-1000 of the K0-K1 engines. The K2 (like mine) would not idle below 1050 (unless I put my [old] transistor ignition on it). By the K3, I was setting idle at whatever speed they would steadily idle at for 2 full minutes in my shop. This ranged form 1000-1200 on some of them.

[RAFster122s]

From my understanding you cannot detect detonation wholely by ear.  When you can hear it is when it is doing the most damage.  It is only by detectors which hear it starting beyond the range of human hearing are you going to be able to detect detonation / knock and then the electronic controls to retard timing to lower the detonation until it is gone.  Thus the reason for knock sensors on gas motors since the early 80s or before.

Ignitech make a nice CDI box used by the CX500 s but they basically do not utilize even 1/10 th their capability as the default curve and basic functions perform better than what it replaced and it eliminated the need for the stock pulser coils.
David

[Ilja]

I have an ignitech ignition with MAP sensor on my turbo cb750!
A while back I posted a topic about his ignition system somewhere on this forum with some examples.

This way I retard timing based on measured plenum pressure by the map sensor. Works like a treat!
Around 200 euros with cables and including the MAP sensor.

You can also connect it to a TPS sensor and advance timing at part throttle for non-blown bikes. (just click an option)

The ignition can also control a servo motor so you can control a valve in your exhaust or movable velocity stacks.

[Ilja]

From my understanding you cannot detect detonation wholely by ear.  When you can hear it is when it is doing the most damage.  It is only by detectors which hear it starting beyond the range of human hearing are you going to be able to detect detonation / knock and then the electronic controls to retard timing to lower the detonation until it is gone.  Thus the reason for knock sensors on gas motors since the early 80s or before.

Ignitech make a nice CDI box used by the CX500 s but they basically do not utilize even 1/10 th their capability as the default curve and basic functions perform better than what it replaced and it eliminated the need for the stock pulser coils.
David

You can hear it, except when you have maybe a loud open exhaust...
In cars its hard to hear because the engine is enclosed... and they ping more easily because they operate at lower rpms and have bigger cylinder bores.
Thats why they absolutely need knock sensors.
Good motorcycle engines sometimes cant even be brought to ping, even when advancing to 40 degrees at max torque.. because rpm is higher and bores are smaller so less time for pressure to rise when the piston is coming up after spark.

I had pinging issues with the CB turbo in the beginning and I also destroyed a set of pistons with it.. (broken ringlands).

It not a big fat rattle like many people think, its more like a small ball bearing in a rattle can which starts in midrange when opening the throttle more then 50%.

Then I reduced compression a bit more and installed the Ignitech IC with Map sensor so I can retard under boost... (to around 24-25 degrees at 15psi) in the max torque area between 5000-7000 rpm.

Pinging gone.


Pre-ignition is a different story... that happens when you are lean, overheat and then you just pop a hole in the center of your piston. 

[PeWe]

Hole like this?  Back then I thought is was too lean only, later I got idea about too advanced 2-3.
Piston 2 with hole, 3 softer melt. Rods bluish

[Ilja]

Hole like this?  Back then I thought is was too lean only, later I got idea about too advanced 2-3.
Piston 2 with hole, 3 softer melt. Rods bluish

That definitly looks like overheating...
The wrist pins also dont look too good and have not been getting good oil or overheated oil.
I think lean mixture, 10.5 compression, hot grade spark plug, bit too advanced and someone who likes to go fast twisting the throttle.. :-) :-)

[PeWe]

Not that much twisting that time, only around 160 kph.  Carbs were not lean jetted, maybe leaking carb boots which should not affect that much at that speed?
The overheating might have been ongoing for a while, the hole was the last drop.

[Bill/BentON Racing]

What he said...not where it starts, but where it finishes! Thanks Captain,  great read.

[Captain]

What he said...not where it starts, but where it finishes! Thanks Captain,  great read.

Finally someone understands. When one starts to look at the event in this way then the rest of what I was talking about should follow.
Captain

[livefast_dieold]

Store brought $20  and self made mounting bracket. As pictured with the red arrow.


 Captain

TPS is not allowed in my class, but it would be interesting to test the difference. How do you install it on the carburetors? Did you simply removed the cap that seals the throttle shaft?