plug reading when running alcohol

Switched to e85, need to read plug to get it tuned in?

Here's some info I found.

From here and here

Reading a alcohol tune-up using spark plugs is a very different than reading a gasoline tune-up on spark plugs. First major difference for alcohol is that you do not read the color off the porcelain around the center electrode. Air to fuel ratios within the combustion chamber are going to be read by the appearance of the metal base ring at the end of the threaded area of the plugs and the color of the first three threads of the spark plugs. The amount of ignition advance is still read as with gasoline plugs by the blue line on the plugs ground strap or sometimes referred to as the ground electrode.

An important note is that the spark plugs only reflect the tune-up that was in the motor just prior to finish line engine shutdown.

The fuel mixture and the ignition timing are totally intertwined as to the effecting the appearance of the spark plug ring at the of the threads and the EGT values. Changing the fuel to air ratio and changing the ignition will both change the combustion chamber temperature. The leaner the mixture or the more advanced the ignition the higher the combustion chamber temperature and the richer the mixture or the more retarded the ignition the lower the combustion chamber temperature. Remember the EGT sensor is outside the combustion chamber so it is only reading the exhaust gas/flame temperature. The more the ignition advance the lower the EGT and more the ignition is retarded the higher the EGT. This opposite effect is caused moving the heat or the flame out of the chamber into the exhaust with a retarded ignition and raising the temperature of the EGT. So having a high EGT because of retarded ignition can and will show less heat in the spark plugs.

It is highly recommended to pick a maximum ignition timing point that is known to be good for your particular engine setup and tune the mixture for that point. This way the tune-up is safe and you can retard the ignition to pull out power without drastically changing your fuel tune-up. You can always go back to the maximum power ignition point without damaging the engine.

Reading For Air Fuel Mixture

An important step first is to degrease the plugs by spraying the threaded end with brake cleaner to remove any deposits of oil that may have been put on the plug during shutdown or when the plug was removed from the head. Most of the spark plug manufactures that make plugs used for racing plate the spark plug shell with cadmium or zinc which oxidizes at a temperatures that corresponds to the correct operating range of the temperatures within the combustion chamber of a racing engine.

As one is tuning the motor and leaning the fuel system out the first part of the plating to start oxidizing will be the ground strap. This oxidation (burning) is uneven in progression around the ring at the end of the threaded part of the plug because the side of the plug ring that was closest to the exhaust gets hotter faster than the side of the plug ring that is closest to the intake . The result is a crescent of unburned cadmium that gets smaller as the engine is leaned out. When the cadmium is oxidized and has turned white across the entire face of the plug ring or countersink area just inside the ring the increased temperature then progresses down the side of the plug into the threaded area.

The peak performance is at the point where the cadmium or zinc plating oxidizes and turns white over about 90% of the plug ring and a small crescent of unburned plating is left on the ring. Burning 100% of the plating off the ring all the way down to the first thread will not result in any damage but will also not result in any increase in engine performance. There is a fairly large tuning range between the burned area being at 90% and being burned all the way down to the first thread. Using this large area will ensure that no damage is done to the engine. The next stage from this safe appearance is when the cadmium is burned down to the second thread and the ring loses its white appearance and picks up a greenish tint with small visible bubbles and the ground strap picks up rainbow colors (blues and green when held in the bright sunlight). The strap getting hot enough to exhibit rainbow colors is hot enough to start igniting the fuel mixture too soon and causes pre-ignition/detonation. As the plug gets hotter then sooner the mixture will ignite and this will result in the melting of the ground strap and possible breaking of the plugs porcelain and damage to the upper rod bearings.

By keeping good records of actual performance this peak performance point should be readily seen and matched to the indication on the spark plug ring. When the 90% white ring is obtained with the fastest MPH noted you are now ready to move on to adjusting the ignition timing.

Reading for Ignition Timing

Once the fuel mixture has been adjusted so that 90% of the plug ring is white and all the cylinders have been adjusted so that the white area are the same on all plugs the ignition timing can be now checked by reading the blue line on the ground strap of the plug.

Ignition timing is also directly responsible for the heat in the combustion chamber and therefore the color of the plug's ground strap is a tattletale sign of this temperature because it is thinner than anything else on the plugs and sits right out in the combustion chamber. The ignition timing can be checked by looking at the color of the plug's ground strap and the position of the "blue line" on the strap. The blue line really indicates the point at which the strap has reached annealing temperature of the metal. To help to understand this think of a bar of steel (ground strap) on a table that is being super heated with an acetylene torch at one of the tip ends. As the end heats up and the heat starts moving down the bar you will see a blue line across the bar at some point down the bar away from tip with the torch. This blue line reflects the temperature that is the annealing point of the metal. As the temperature increases the blue line moves further down the bar away from the torch. Similarly, the blue line moves down the spark plug ground strap as you put more heat in the engine.

Assuming that you have adjusted the alcohol fuel mixture correctly and if you are using gold colored ground strap like with an NGK spark plug then not enough timing will show the ground strap as still gold or going light gray maybe with a few bubbles on it after a run. As you advance the ignition and put heat in the engine the plug ground strap will turn darker gray. As the metal turns medium to dark gray you should start looking for the blue line (band) around the ground strap. Ideally, you want this blue line to be just above where the ground strap makes the sharp bend and above the weld. If you advance the ignition too far the blue will disappear off the strap and the strap will pick up rainbow colors (blues and greens). The next step beyond that is to start melting the strap from the tip end and detonation. When you are close to the correct timing then only change the timing by half a degree at a time. If you ignition system has the capability of adjusting the timing of each cylinder independently (ICT) then you can use that feature to have the blue line in the same position on all the plugs. First, adjust the basic timing to get as many of the plugs to have the blue line just at the sharp bend in the strap. Now adjust the ICT to move the blue line to the same point on the remaining plugs. Once all the plugs read the same you can advance the ignition a little at a time to put the blue line just above the weld on the strap or whatever point gives you the best performance.

If your timing is too far retarded then it maybe necessary as you adjust the timing to add a little more fuel to keep the crescent on the end of the plugs white for 90% of the area. Be very careful on adjusting timing because it does not take much change to make a lot of difference. I recommend limiting the changes to half a degree at a time. It is easier to set the timing at a known good degree for the type of engine and adjust and individual cylinder timing (MSD ICT) to balance out all the cylinders and then adjust the mixture to show the correct amount of white area on the metal ring of the plugs as explained above.

This pic will give you a good idea of what you are looking for. You can see where the black is. It is where it has burnt the strap and an ideal plug will have that burn to 3 and 9 o clock on the plug. As you can see, this one is more like 4 and 11 but you get the idea. No need to cut the plug. Unless you are almost too lean, you won't show heat after just one pass. I generally use 3 full throttle runs and then check the plug. If you build heat to 3 and 9 after about 3 runs you are spot on. If you want to hot lap the motor you should prolly richen it up a little from there.

Re: plug reading when running alcohol

care to add how heat range of the plug affects the grounding strap bluing?

when do i include that with timing and jetting adjustments?

Re: plug reading when running alcohol

Alex Degnes /

I'm new to this, had first testride on e85 today, so don't know, yet...

Re: plug reading when running alcohol

Glenn Kuehn Wrote:


> care to add how heat range of the plug affects the

> grounding strap bluing?

> when do i include that with timing and jetting

> adjustments?

IMO, if you don't pre-ignite or foul. Plug heat range is good. Donezo.

Re: plug reading when running alcohol

This can be applied to all fuels, great useful info. Thanks for sharing. As far as cars go E85 has proven itself to be less efficient than dino juice in both latent energy (more fuel for same output) and curbing emissions. Only benefit (assuming natural aspiration) is higher octane/ slower burn rate allowing higher CRs and more advanced timing. Adding toluene or xeylene in the 10-20% range to premium gas will push ROM over 100 while returning better mileage vs e85. Unless you live in the corn belt, better options are out there in my opinion.

Re: plug reading when running alcohol

Ah, but you've forgotten something very important, friend

air cooled bikes suddenly become as temperature stable as water cooled bikes, because on E85, they are fuel cooled. You can tune so much more on the ragged edge on a drunken bike that's air cooled as opposed to gasoline because of the latent heat of vaporisation being such a great cooling addition to the engine system

Re: plug reading when running alcohol

Alex Degnes /

I'm starting to get really excited about this fuel, promising results so far.

Some propaganda for the non-believers:

About turboed cars, but much of the same aplies to a piped two stroke.

"Since i have not seen any real concrete info on E85 Air/Fuel ratios on this forum, i figured i would throw up what i know so that some of you can make more educated decisions on what AFR you should tune for on E85. I will only discuss E85 AFRs in this thread and will start a thread regarding ignition timing in the near future, as i don't have the time to do it currently.

I have been tuning many years and have a lot of experience tuning all of the exotic race fuels, along with pump gas. This was actually my first attempt at tuning E85(due to just getting it in my area), but before i attempted to tune the "Corn Juice" i did a TON of research on this amazing alternative fuel. Some things about E85 i already knew, but i found there was a lot i didn't. I want to share what i have learned while tuning my own car on E85.

Despite E85 having been around for a several years now, there is still a vacuum of info on the fuel and some of the info i found was completely incorrect. Most of your pro tuners out there know that E85 is probably one of the best fuels on the market at any price, but they aren't so quick to give up what they know on the subject.

First we're gonna start off with Air/Fuel Ratios and what they mean with reference to E85.

E85 has a stoichiometric fuel mixture of roughly 9.78-9.8:1 in E85's purest form (Class 1 85% Ethanol summer blend). As the fuel's Ethanol content goes up the stoich range goes down. For instance, 100% Ethanol's stoich is about 9.0:1.

E85 will maintain max brake torque much richer than stoich than gasoline will. But, because of it's excellent detonation threshold(due to lower combustion temps, lower peak cylinder pressures..etc), it can be run much closer to stoich than gasoline safer. E85 reaches max thermal efficiency at about 13% richer than stoich, whereas gasoline is about 16% richer than stoich(with pump gas being even richer). But again, E85 can maintain Max Brake Torque well into the 30% richer than stoich range, unlike gasoline which is limited to about 18% rich of stoich. DISCLAIMER: Just because E85 itself will still make power at super rich AFRs, doesn't mean it's a good idea or even recommened. A whole host of issues come with running super rich AFRs, that you need to be aware of, but i will cover later.

Therefore Max Rich Torque of E85 is 7.1:1- 8.5:1

With that being said, here is what i would consider a very safe and conservative fuel tune on E85. *AFR's listed in bold are for widebands o2s that are calibrated for gasoline, AFR's in ( ) are actual E85 AFR:

Part Throttle lean (max eco) AFR of 16.5:1(11.0:1) 12.4% leaner than STOICH

Part Throttle rich AFR of 14.7:1(9.8:1)

Spool up... AFR of 13.5:1(9.00:1)

WOT... AFR of 12.1:1(8.06:1) 17.7% richer than STOICH

*If you're using a wideband that is calibrated for gasoline(14.7:1) and cannot change the calibration of the wideband, take your gasoline AFR and divide it by 1.5 to get actual e85 AFR or use the wideband in lambda mode. 1 lambda is 9.8:1

Here are some common AFR conversions(Gas AFR on left, e85 on right):
















Of course, all engines are different and there is still a lot of trial and error when tuning any setup. Having the ability to measure torque output is a must for tuning both fuel and ignition timing with E85. We are only talking about E85's fuel properties in this thread and not taking into consideration ignition timing, boost pressures, different E85 fuel mixtures..etc. Care must be taken when combining all the aspects of the tune and setup, to assure proper limits and safety.

Now that we have that out of the way, let's compare E85 with pump 93 octane.

As you can see, the lean side of max rich torque for E85 is 8.5:1, which is 13% rich of stoich. We know gasoline's max rich torque is about 12.5-13.0:1, but because of pump gas' low detonation threshold, we must run AFR's much richer with forced induction. Therefore, AFR's of 22+% rich of stoich must be used to combat detonation, while running E85 13-15% rich of stoich results in no detonation. Why is this, you ask?

Here are the reasons why:

1. Lower EGT's. E85 will typically see EGT's 200c below pump gas at the same relative AFR (for instance 12.5:1 pump, 8.33:1 E85)

2. Octane rating of 105 with class 1 e85(raises detonation threshold)

3. Very high vaporization cooling, much more than gasoline, which lowers mixture temps, thus increasing detonation threshold, along with increasing VE

4. Peak cylinder pressure are lower while maintaining a higher and longer overall cylinder pressure, thus raising detonation threshold and making more power due to increase in crank angle

5. E85 burns much more efficiently than gasoline, 27% more efficient

6. despite lower EGT's, E85 creates more exhaust gas volume, which helps with spool without added EGTs

So, we know that E85 has a very high detonation resistance, one thing E85 does not have much tolerance for, is pre-ignition. This is where E85 starts to wander from exotic race fuels. E85 cannot withstand pre-ignition as well as it can detonation. I believe this is due to the fact that it actually burns much faster than gasoline(pump or race fuels), among other things. While it's very tolerant to lean mixtures(detonation), over-advanced ignition timing takes a toll quickly on E85. While E85 will take more ignition timing than pump gas overall, it will not allow a lot of ignition advance at peak VE, but will want more and more advance as RPMs rise, this ending up with much higher peak timing numbers. We'll get into that in the timing thread i will start."

Re: plug reading when running alcohol

not a Baron Asshole /

The majority of the issues are: that its pretty hard to come by in much of the country, you need to run massive jetting and plug reading will be out the window. SO yes awesome and i'd like to try some different fuels to see what can be done.

let us know how it goes

Re: plug reading when running alcohol

Alex Degnes /

There's very few places to get it here in Norway to, like 15 stations throughout the whole country... But I live under a mile from the swedish border, and in Sweden it's as common as normal unleaded.

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