Severe detonation up hill Harley Tuner & High Performance Discuss Severe detonation up hill in the Harley Tech & Harley How-to forums; Hey 03 Just a post-script here.. First off,, I have a sneaky feeling you're trying to walk toooo fine a line between what "They say is correct A/F" and real ...

[frisco-rigid]

Hey 03

Just a post-script here..

First off,, I have a sneaky feeling you're trying to walk toooo fine a line between what "They say is correct A/F" and real world running..

Even though Bosch says that 14.7 is Optimal (they call it stoichiometric value 1,,,,whatever the heck that means) and the Gov wants 14.7 Or Leaner,,,, it is Not a healthy A/FM for these devil machines..

I have a bud that about 3 years ago built 2 motors that set about 9 or 10 world land speed records at Bonneville.. He also built my 93" and 120"..
Anyway, when these guys are trying to set records they DO attempt to find that Perfect A/F which is actually fairly lean.. BUT THAT is Not going to do you or me any good at all..

I strongly sugg that when you decide on what carb you are going run you jet it so that a high-spd plug run as well as a low-spd run gives you tan to Med-Gray porcelain & electrodes..
That should give you about the mid to high 13's of A/F..

As far as Voes-- I don't ever use them.. If your IGN. has a NO VOES setting switch to it, re-time and try it.. If you don't like it simply switch back..
Time to experiment a wee bit..

Something else--
I have run 5 diff electronic Ign.'s, Dual-Fire and Single-Fire,, and burned out all 5 in this Phoenix Valley summer heat.. Each time I temp went back to points before re-installing a new IGN.. Bottom line-- I never felt any diff at all between them.. Daul-fire, Single-Fire, or points..
No more power or smoothness, mileage, ease of starting,,,,, Nothing diff..
I now run points in the 120".. I figured, why run something that gives me No more benefits but Much Less reliability.. However, they were just fine in the Bay Area climates..
In fact I do seem to have a wee bit of easier kicking the 120" with points..
The Ultima Ign that came with the 127" ran absolutely horrid, partly cuz it's lowest time at idle was about 16*.. I installed a DynaS set to Dual Fire and it runs great..
The DynaS in the shovel is still running so I let it be, when it dies, it'll be points again..
Now, I am Not sugg you go to points, partly cuz they are a real pain without a kicker, but perhaps an Ign. that is Not quite as fancy,,, one that will allow you to re-tard to a more reasonable 5-8* at idle.. That's why I use the DynaS..

Hey,, just something to consider..

[Wrightturn]

Hey Tommy,

Frisco`s advice on mid to high 13`s would be the same as mine. On flat ground with steady load 14.2 won`t cause a major malfunction until you slow down and need to pull a hill on ahot day. My A/F meter has verified that I can run 13.8 in the Fla heat in moderate traffic. Getting EFI away from the EPA mandate is what makes things difficult.

In the early 70`s I would ride my CH Sportster to the strip and lean out and advance the timing. Might have cut .1 to .2sec off the e.t. Cooked the rear piston. After each run the bike would keep running with the key off. Had to stall it and try to cool it down. Carb bikes will never control the mixture like EFI. Control of the EFI is a greater challenge and expensive. Some days it would nice to have breaker points. I have only had one ECM fail. I have replaced coils on my own Twin Cams and a few others. I think they fail due to heat and poor ground connections.

[tommyglide]

Wrightturn, thanks. I can adjust the afr on my ecm, that's why I was asking about the 14.2, just to get a few more mpg, which may or may not happen from 13.7 which is the current target afr. When I get better weather I can strap the laptop on the scooter and hit the "road test dyno" and It will show me the target afr and actual afr at different tps. I like riding in the 1 hot day we get so I may just leave afr alone.

Frisco, good ignition lesson. I looked at my own ignition map to see how it compared to yours, and wouldn'cha know, fairly close. I have 1 question though, when you say finish at 2200 to 2400 is that when you are at 28 or 30 degrees? My set up arrives at 28d at 3584 rpm and 30 at 4352.
Thanks both a youse.

[03fxst]

Tanks guys
I think I will shoot for a richer mixture. I just aimed for that red dotted line on the Dynojet chart and figured all was good when I hit it. Before I begin I will have to make the carb upgrade decision. I'll arm wrestle with that this week. Maybe I should have kept this as one post but I figured the pinging was more a timing problem so I posted the carb question seperately.

Tommy have fun with that rolling Dyno mode on your EFI. The only thing I can do with a laptop to improve my performance is check in on the advice here. I think it is time well spent.

My igniton is a Dyna TC88 digital with three pre-programmed curves for a total of sixteen available selections.
http://www.mpsracing.com/instruction...tek/TC88-1.pdf will show you the instructions and maps of the curves available.
No Voes selector though. I ran it back to the 26 degree curve in the B grouoping today and did a fourth gear roll on test along the same road. The top end ping on is gone. The idle is also back in a close to stock range.

03FXST

[frisco-rigid]

Hi Tommy

Yes, I am Full Advance on any/either motor at about 2200 - 2400 R's..
It starts at 7*+- and ends at 28* or 30* exact,,, at 2200 +-..
Remember,, I run from 10-1 to 10.5 to 1 in all my motors..

I tune (includes all tuning) until I get the most "seat-of-my pants" perfomance, with whatever motor, then lock-it down.. I don't dyno.. I could care Less what a dyno run says, that is Not the street.. However, I have done a few gear runs, kinda duplicating simply runnin normal through the gears on the street,, to confirm my A/F mix..
My concern is performance & Long Reliability.. I accept whatever Fuel mileage comes with that.. Motors are waaay more expensive than gas..!

I have found, in my motors, that re-pressing the timing for tooo long I lose power/performance..

I think one reason the Co. and the Ign. manuf's for instance, program a slower advance like yours, is because they know that lota guys won't/don't/can't get a fatter A/F mix.. With a lean "street" mix a wee retard/slower advance might Not encourage detonation as readily as a more old-style normal rate of advance might..

You gotta remember,, the older HD's were full advance @35* by about 1800 R's or less.. That's why in all the older sickle manuals they instructed to rev to 2000rpm's to time it..

Have a ball

[tommyglide]

Hi frisco, it might be relatively safe to have my advance hit 28 or 30 at 2400 IF I can be certain the afr stays fat enough, if I'm understanding you correctly. According to the afr graph that should happen, providing the timing doesn't alter the afr, which I can't see it doing. At what rpm do you suggest altering the timing, just above idle? Now, what exactly does that accomplish, having the advance finish at a lower rpm? This scooter has 10:1 compression also, if that helps, and yes, I guess its considerably better to live with a safer afr than chance one more mpg.
Thanks again for your hep.

[frisco-rigid]

Hi Tommy

From my fights with the Bosch EFI over the years I learned that the computer will strive to achieve whatever value it is told to hold and the 02 sensor is a tattle-tale,,,, bastrds..!!!
So, I would rekon that whatever range you adjust the timing to, the computer will hold that line..

I'm not sure what you mean---"At what rpm do you suggest altering the timing, just above idle?"
I would try to get my idle to about 5-8* and finish at 30*+-.. That's me..!!! Pardon me Tommy, I don't remember what motor you run..

Now,,, I would ask the Co.'s what advantage there is to running such a slow rate of advance..
First off, we gotta remember why we have "advanced" ignition..
We gotta give the spark time to ignite the charge and for the charge to complete the burn a * or two before or at TDC..
Here's an extreme example.. If the motors final advance is 32* and at 4000 rpm it's only 20* the burn is still working long past TDC,, heat & loss of power will result.. Now, some would sugg that is a good reason to just keep advancing as long as the motor is gaining R's,,,,,, well, you know, that could be a ligitimate topic but for some reason all our motors, car, sickles, etc have a final point of advance..
The HI4 ends at about 38* with voes.. The Compufire at 35* with voes.. Etc Etc..

So, if it ends at a final point or continues to advance--- it still has to be "ahead" of the piston..
That would be my reason for a quicker (more normal to me) rate of advance..
Heck Tommy,,,,,, you know,,, it used to be that we had to convince guys to slow Down their Ign.'s rate of advance to stop detonation and bucking,, some guys would adjust in 35* or more soon off idle,,,, just the opposite prob huh..

I hope I understood your question correctly and I assisted a wee bit..

[tommyglide]

My interest is sparked.
Frisco, I understand what your getting at so I'm going to try an adjustment when it quits snowing.
"alter timing just above idle" What I meant by that is I'm looking at my Timing vs Engine Speed graph, and able to change the degrees of advance at any point in the rpm scale, making it a nice smooth line or an abrupt line. From your post I'm understanding that I can start the alteration where the scoot no longer sits at idle.
The engine is a 96 TC, flows a lot of atmosphere and has a cam change, whereas the timing map was built for a relatively stock motor.
You assisted more than a wee bit.

[cntrhub]

They say that, 10° ATDC, the fuels should be spent, because on the 11th degree begins the power stroke. If you do not pressure up all that atmosphere you sucked in... The 02 is going to be sprayed wet in the face, cool down that fat-ness and lean you out.

That tuning window is narrow. It's all about that feed in degree and how much is going to be eaten up to make the max pressure to push the piston down.

Too much cold rich will cool the pressure down. Too lean like a restrictor plate is you just suck in air and not lean out is run out of air [speed in time] is that chase to the fuel to air ratio = Most Pressure made over that piston dome.

[Wrightturn]

Hey Cntrhub,

The cam is not stock. Longer duration cams will lower comp at lower rpm. Thats why milled heads and thin gaskets are used to recover the bottom end.
When you increase comp but have a longer than stock duration all bets are off. Changing the advance curve is needed because com pressure will be moved up in the rpm range with the diff cam.

I don`t know if you remember Sunoco 260 or ever mixed Amoco with aviation gas but it would solve all these problems. The EPA won`t let us have it anymore.