Timing keys on M series?

I was wondering the same thing. Also I was wondering what people think of milling the heads on the 700 engine.

I understand that you do not need or want to advance the timing on 06 m7. I took .013 of my 06 m7 head and run 88 octane fuel runs great. At 7,000 to 10,000 feet

ran 2.5 key in my o6 at 2000 ft up to 9000 no problems but maybe i was lucky,i had to take it out for nos kit do not really notice much difference now to then was told at time mainly clean up top end fuel richness

Timing keys have the biggest gains in larger displacement engines. Because the distance across the piston bore, squish and dome are larger. A few degrees of advance gets the flame started earlier from the boost port. This is also more relevant when adding twins as they scavenge or draw more efficiently. Some riders change to high compression heads, then need high octane fuel to prevent detonation, then need a 3 degree key to control the slow burn of the fuel. Vicious cycle for 4hp.

I have always added timing for altitude. Albeit only one or two degrees, but that is when the motor is spot on to begin with (16* @ 8k RPM on a 70mm stroke).

The '05 is 13* (ish) at 8K RPM with stock key. But, quite advanced in the mid-range. So, if a person adds a 2.5* key and puts down the trail in mid-range, the chance of it doing damage is there.

On the old big block Poo motors, we would turn the stator until the plugs started to rattle loose, back it of a degree or two and not run it in the mid for extended periods.....

This is an interesting topic.

Ignition timing is a huge factor in performance for gasoline engines. If it wasn't such a pain to adjust it on snowmobile engines, I would mess with it more.


FORDpickupman

We are running a 2.5 key with twins in one of our F7 motors. running 91. Very good results, we also have porting done and running fuel regulators to control everything but its night and day over a stock 700 even with a single pipe. Not sure on the timing/ecu map of an M but we mainly ride 0-3000' tops. We have been entertaining pulling a tad off the head as Randog did, but running 88 octane in our cat motors will never happen as our 87 octane must be bad cause all of our cats run like crap unless its 91 or better. We get alot of mid skip( does a little hesitation or miss type deal).
But is it worth it for a few hp, to me no. I just like to have the fasted sled out there if possible in my CC range so its worth the tinkering to me.

This topic is even more important to you firecat99 because at 0-3K ft.your chance of deto is even greater than that of the 8K plus boys. But then you have those guys running super high compression 'thinking' they need 100% 110 race fuel that they now have a VERY finnicky sled that is great at one temp and stumbles with a 10 degree ambient change. How many people have a mod with twins that only really comes to life 50% of the time. With natural aspiration, a 70-30 blend is good to 11k maybe 50-50 @3k. remember we are trying to ignite all the fuel before the piston exposes the exhaust port. So if you have a big cc motor that distance is large from boost to exh. cyl. wall. and a serious advance is needed especially at higher elevations because we have less o2 to oxidize the fuel. So guys that run ignition advance at low elevations have greater risk and don't need a slow burn because their fire starts quicker. Look, think of detonation as using the kinetic energy from a bomb. Its like utilizing the percussion rather than the explosion for your power source. Get it?

So, you would suggest that 70% gas / 30% Av is optimum? I was thinking about running 50/50 this winter.

I run 4800 - 9000 ft and mostly boondock. Could I benefit from a key more than a RKT head re-shape?


FORDpickupman

Booster said:

a serious advance is needed especially at higher elevations because we have less o2 to oxidize the fuel.

So guys that run ignition advance at low elevations have greater risk and don't need a slow burn because their fire starts quicker. Look, think of detonation as using the kinetic energy from a bomb. Its like utilizing the percussion rather than the explosion for your power source. Get it?

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ok...my eyes are crossed here...are ya saying that if a person is running a ported bigbore with 13.5 or 14 to 1 compression at lower elevation that they should just need a mixed race gas/ 91 combination and DO NOT need a timing advance key and that an advance key may be dangerous..??

im in a similar situation as firecat...900 bigbore/ported /higher compression/ 2300 to 4000 ft/ 2.5 degree key
91 octane..(supposedly and possibly ethenol content)...your thoughts..??

m8magicandmystery said:

ok...my eyes are crossed here...are ya saying that if a person is running a ported bigbore with 13.5 or 14 to 1 compression at lower elevation that they should just need a mixed race gas/ 91 combination and DO NOT need a timing advance key and that an advance key may be dangerous..??

im in a similar situation as firecat...900 bigbore/ported /higher compression/ 2300 to 4000 ft/ 2.5 degree key
91 octane..(supposedly and possibly ethenol content)...your thoughts..??

Click to expand...

I am similar... Cylinder shim, cut head, full pipe... 2.5* key @ 0-3000ft (09 M8). The raised cylinders increase the port timing and the main reason I am running a key. But regardless, advanced timing on low elevation requires better/ cooler burn. I have run 91+ on this setup and never touched the knock sensor other than the few times I got stuck running 87.

I ofter run 91octaine/ Av gas mix (usually about 3 or 4:1) and find the performance much more crisp and hesitation free. I often read my plugs and wash, and find everything much cleaner with the mix. I think it is worth it to try. If you are running mod anything and not reading your engine, you are pretty crazy.

I guess to sum it up more in line with your question, running lower octane extends the burn time generating more heat. The deto often comes from the pop during compression rather than pop then compression. If that makes sense.

We have used AV gas straight and mixed 50/50 at first when we ran the motor, and worked it down to pump gas (starting to get annoy dragging barrels around, not to mention storing them), but we also mix our fuel as we dont use oil pumps. But our motors are tested for a good week pretty hard before we stop watching everything. I have never had a burn down, my brother has had two due to bad advice on some tuning numbers and him not knowing as well didnt help. I have taken timing out of some of my motors also as they didnt need it, I think it comes down to what your comfortable with and know what your looking for and how or why and combinations from all mods done can make a sweet good smooth hp or a motor that likes to pick its days to shine.

I have a 2011 with the timing Key. I rode with it for a full season on my 2011 and m8 and had no problems running pump gas even at 10 to 12,000 foot elevation running 7 to 8 pounds of boost

I believe you meant to say running higher octane extends the burn time.

m8magicandmystery said:

ok...my eyes are crossed here...are ya saying that if a person is running a ported bigbore with 13.5 or 14 to 1 compression at lower elevation that they should just need a mixed race gas/ 91 combination and DO NOT need a timing advance key and that an advance key may be dangerous..??

im in a similar situation as firecat...900 bigbore/ported /higher compression/ 2300 to 4000 ft/ 2.5 degree key
91 octane..(supposedly and possibly ethenol content)...your thoughts..??

Click to expand...

Hi m8magic...that is exactly what I'm saying. Look, there are many variables when it comes to two-strokes, and each engine is set up or manipulated different. However, there is some physics that don't change regardless.

rteller said:

I have a 2011 with the timing Key. I rode with it for a full season on my 2011 and m8 and had no problems running pump gas even at 10 to 12,000 foot elevation running 7 to 8 pounds of boost

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This Gent is a prime example....@ 10K- 12k you always need to jump start the flame front with advance as there is less o2.....and because he got a hair dryer he's shoving atmospheres through his engine at break-neck speed, thus he must use a slower burn fuel (high octane) to complete combustion. Not sure I can simplify any further.......

I have been running a a 2deg advance on my M1000 that has porting, reeds, BDX power valve delete, and twin pipes. 6-10k elevation. Probably around 215-220hp. I was not real happy with the setup as it was very finicky. The mid range EGTs would explode at any sort of part throttle. Very annoying. I decided to try the SLP single setup and sacrifice a little HP for the consistency. Their tech guys told me to get rid of the timing key. They were able to build better more consistent power without one. They said the issues lies not with the advancement of the ignition timing but the key also advances the injector timing. They recommended using compression to compensate for elevation, not the timing key. I got a high comp head and am going to try that approach. I plan to do some riding at 10-12k elevation this year and may try a day with the key and a day without to see if I can see any difference. On a more general note, timing is great for low end and mid range power and throttle response, but going too far can actually cost you power on the top end. Obviously there is a tipping point between where more timing is going to help your entire range and where it will start to hurt top end. The guys from SLP also said that the new Power Commander can control timing electronically so you can advance your ignition timing without messing with the injection timing. They also said that it can set up variable timing, more timing on the bottom and mid range where it needs it and take it away on the top end. If you have a mod sled, just ask the guys where you got your parts, or if your demented like myself and like to spend half you time figuring out what works the best, buy a couple keys and try it. Make sure you know what your looking for. I run EGTs and AFR gauge and check my plugs and piston wash frequently (one huge benefit from the power valve delete kit as you can put two bolts and look down your vale and see your piston perfectly). You can tell pretty quick if you are detonating, you can see a rough or pitted look on you piston in the center, or the square end of the prong on your spark plugs will round off and even start getting eaten away. Obviously, the correct fuel for altitude is critical and again wherever you get your aftermarket parts from should be able to tell you what fuel you should be running. They have spent a bunch of money doing research and probably ruined plenty of motors so you might as well learn from their findings.