Does octane affect lean/rich jetting

I know the lashing is coming and I accept full responsibility.
Bike tuned on MR12: 87 octane, leaded oxygenated.
Second Identical bike, motor built by same builder didn't make it to the dyno. Last minute crap, no MR12 is available. Sunoco Apex is available 95 octane leaded oxygenated.

I know, trust me I know. oh yeah, it's at Daytona so yeah, any jetting suggestions relative to what I've got on the first bike with MR12.

 

Someone at the track has to have MR12, even if only enough for your race(s). Walk around with a jug and ask for whatever can be spared, dollars in hand?

 

im pretty sure APEX is not leaded.

 

Always dollars in hand Will give it a shot

 

Crap you're right

 

Can't offer advice on this particular jetting situation, sorry. But specific gravity, oxygenation, and base blend all can affect jetting dramatically. When I used to switch fuels from practice to qualifying we increased jet sizes enough that it was easier to swap carb racks or chips. Octane normally gets thrust into all that because when the others change octane normally changes also and the octane get published.

 

Can you copy mapping to new bike? Otherwise really really different mapping. You have a serious issue.

 

Carbs or EFI? If carbs, maybe bump up the main one size? Better to be rich than lean, especially someplace like Daytona, I would assume. Then adjust from there. Maybe go up two sizes, and drop one if needed?

 

Carbs. Yeah I suppose we will go up one or two sizes. The guy borrowing the bike is a 2 stroke racer so I'm sure he knows how to do a plug chop.
What a disaster . Zero hour motor doing a plug chop at Daytona.

 

Thank Emry and RM (don't know how to quote two posts at the same time).
This is what I'm looking for. Have a tendency to fall back to high school chemistry, change one thing at a time. These two fuels are a different octane because of other factors, correct? Plus one is leaded and one is unleaded.
RM, I have way more than one major issue

 

So, MR12 vs Apex

Spec Grav - .733 vs .744
MON - 87 vs 90
RON - 100 vs 100
Stoich Ratio - 13.13 vs 14.2
Oxygenation - 8.75% vs 2.6%

Yeah, I don't see these being in the same planet jetting wise.

 

Doesn't look like a need to jet richer, it's already gonna be so.
The real concern is the delayed combustion. First off, you're gonna lose power and, worse, that's gonna be followed by a still burning mixture exiting the chamber.
You'll need to advance the ignition and/or bump the compression. The question is, how much? Then, you still have to deal with getting a correct mixture.
If it were mine, I wouldn't bother starting it.

 

It's a cluster F. He found 2 cans of MR12 in Homestead. I just looked at the date. 2015. Truthfully I don't even know if that matters but it doesn't sound good.
It's 5:30pm, the zero hour motor was just started. We will do a few heat cycles today and tomorrow morning and then that bike will be broken in on the banking at Daytona. There's nothing that could go wrong.

 

Well I was down there this weekend and didn't hear about anyone going kaboom... How'd it go?!

 

Well...
my motor overheated slightly in practice and blew a head gasket 3 laps into the first race. The second bike managed a 3rd place in 500SS and then Miguel put the hammer down, as much as can be put down on an EX500. Led the race until the last 1/2 lap. Mark got him by a couple of bike lengths on his FZR400.
So we ended up going one jet size bigger for safety and it seemed to work well. I ended up with extra fuel since the first bike was down.
Overall it was a good weekend and very educational. Not a bad break in for a zero hour motor.
We will try again next year

 

i think the MR12 "87" octane rating of mr12 is a different method of octane rating (MON) .. here's the VP fuels master list. Based on the R+M/2 method (what i think most pump ratings are shown as ?? ) it's octane is 93 .. and the RON method is 100 octane..

https://vpracingfuels.com/master-fuel-table/

the popular c12 and U4.4 fuels are still higher octane in all methods of rating though.

 

Thanks Greg for the link.
It's my understanding that if I have a motor with 11:1 compression, I wouldn't necessarily need higher octane, correct? The proper way would have been to take to the dyno for multiple fuels and see what it liked, but time was limited and the first choice was MR12.
By the way, that stuff saturated my suit and the garage. The wife made me move the bikes to a storage unit. Holy crap that stuff stinks even after it was purged from the bikes and the can was sat out in a storage shed.

 

From what I understand, you need to run some pump through after draining the MR12. It leaves deposits in the fuel system and inside the head.

 

Correct, done on both bikes. Not sure how this stuff sticks to clothing so well, but between spilling a bit going from the can to a clear jug for measuring and then back it's a nightmare. After leaving Daytona, I stopped by Publix to grab some snacks for the road and could smell it on the open trailer in the middle of the parking lot. crazy stuff.

 

Lol, be glad it isn't Nutec or Agip from the 90's.