Don Terrill’s Speed-Talk

Hello,
I was wondering if anyone has any pictures of what a methanol plug looks like on a well tuned race engine. What does it look like when it is too lean and what does it look like when your too rich. Trying to tune without any egt. or AFR gear so I need to rely on plug reading. I am no expert at this and would like to know as much possible. Any input would be appreciated.
Thank you for all your considerations and leads.. Craig

No picture but you need to monitor chamber temps by looking at the color change / cad burn on the plug threads. You should not see anything but clean white porcelin. Depending on spark plug cooling characteristics of your head, a thread down of burn should be safe, two threads getting close to the edge of too hot. You can have sky high egt's and still have cad on the face of the plug. All the egt's show in that instance is the fuel is burning in the pipe instead of in the chamber. Never rely on only one source of info when tuning. Always look at a second source to back up what you THINK you are seeing. Keep in mind different plug makes have different temp thresholds for the cad burn. That is where experiance comes into play.

Stevespeed,
Thanks for your reply. Any info you can think off feel free to throw it at me even if you think is very basic. What does detonation look like on a methanol plug, does it still give you a black peppered look. Is there a color that is visable down inside at the bottom of the porcelin if you go to rich or will it just stay looking like a new plug with no heating color change on the threads. What brand and part no plug would you use on a Yates headed sbf making around 650hp. It might help me use your method as you say different manufactures cad may burn differently. (which brand burns the cad the easiest). On a single dominator manifold feeding 650-675hp with your expirience what fuel presures do you recommend(BLP belt drive)at idle and top end?Engine turns to about 8200rpm.
On another point of interest for me is at what comp do you think you start to see a gain using methanol against petrol.

Once again I appreciate and thank you for any advice. Craig

You can thank member Larry Meaux for this:

http://www.maxracesoftware.com/spark_plugs.htm

Check out Larry's software- some of the best at great prices!

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CSH, for .750 reach gasketed plugs I use NGK R5671A-9 in most cases or go to -10 if the application has a ton of cylinder pressure or extended temperature. Same with Autolite. 3933's are about same as 5671A-9's, 3932's same as 5671A-10. You won't find a dark "fuel ring" at the base of the porcelin like you would with gasoline. Alky consistantly shows performance increases of 5% even with compression down to 11:1. Look for pepper on the porcelin just as in gasoline when looking for detonation. Missing ground electrodes and missing chunks of porcelin are a sure sign of detonation Sorry, couldn't resist. Happy hunting

Hello CSH; Methanol does build up brown on the porcelain. It varies depending on the engine. At least if the porcelain is slightly browning you know the mixture is safe. With a lack of any measuring equipment that is a safe way to start. Whereas petrol will brown the strap electrode methanol wont. Methanol will form a slight brown ring just below the radius on the top of the porcelain if its a safe burn in a correctly energized mixture. It takes a while to form deposits as it doesn't have the carbon in free form like petrol does. Look for excessive wear on the corner edges of the center electrode. If the plug is rounding these edges off its just on the side of too lean at sparktime.
The best strategy is to ignition time it safe. Without data you will have to sneak down from the rich side and go by engine feel and time slips.
On some engines a rich mixture will wash the plug clean and no coloration at all will get onto the center porcelain. When reading methanol plugs it gets a little more difficult if there is any Acetone in it. Some sellers add acetone to methanol and that builds up carbon like petrol does. So first you have to know your fuel. It doesn't hurt to ask. regards Shrinker

I think the easiest way to check the tune up on a methanol engine is to look at the exhaust valve on #6 cylinder (SBC).

A very light tan color is usually pretty safe. If the valve is white, that is too lean. If the valve is brown that is too rich. If the valve is blue you are probably in deep trouble.

Sometimes the port is hard to read due to idle circuits, racing conditions, etc. But if you look in your header there should be a slight trace of carbon in the entry to the header pipes and no soot at the exit. If you have black carbon soot at the exit of the collector you are too rich.

Anymore, at least in circle track applications, it seems like detonation caused by a lean condition will crack pistons under valve reliefs before they will burn the edge off. (Voice of experience speaking)

MB

Thats how I do it to MB. Never lost an engine (or piston). 2-Strokes on Methanol can be an absolute pain to get right. The team I'm with now run an inline six on Meth in circle track. Pull the headers. The only way to be sure. And get yourself a density meter. Zammit Bros here in Aus had/have a good one that we always could count on........trikes

I know this is bring up from the dead

If seeing a lot of black pepper spotting/splinters on porcelain after 2-3 dyno pulls. Is this a definite sign of detonation?

Or could bad ring seal or excessive carbon build up cause this?

I would compare the plug color against a brand new never used plug and if I could see any difference in color I figured I was OK. never burned one down so maybe I was lucky.

G,day James,
If I see pepper, ie that has a size or shape and is raised above the porcelain, than its detonating.
If you think you have excessive carbon on the pistons or chamber than its still detonating and rattling it loose.
Plug may look ok fuel wise but simply have too much timing, only has to be at one point, ie at peak torque.
Cheers
Paul

I have seen new plugs that had little particles on them when inspected, now I always blow them out with air regardless. A scope looking thru the spark plug hole could be useful.

This is from Larry Meaux on Spark Plug Reading.
(looks like his page is down?)

Spark Plug Reading