Afr numbers?

alfadanne · Jan 18, 2019

I have a -16 axys with a silberturbo and lowcomp head.
After install of lowcomp head 11.3-1 (because of bad fuel here in Sweden) i have problems getting it to not det, and lots of lag.
Bought a PC V fuel and ignition and started tuning, but doesn’t seem to get it all the way, so i bought a autotune.
But what afr numbers should i aim for? Low/mid/wot?
Is it the same numbers as on 4stroke?
I have tuned cars.
Thanks /Daniel

alfadanne · Jan 18, 2019

Ride at sealevel and 5psi

Octanee · Jan 18, 2019

Let me know your findings, not as related. But I'm also in the same sort of. Boat, lots of. Lagg and bog, and det codes which I believe are artificial. Leaning out my map helps the lag but seems to still want to throw det somehow.

That said at wide open they say shoot for 11.5 ish

sledhead9825 · Jan 18, 2019

Octanee said:
Let me know your findings, not as related. But I'm also in the same sort of. Boat, lots of. Lagg and bog, and det codes which I believe are artificial. Leaning out my map helps the lag but seems to still want to throw det somehow.

That said at wide open they say shoot for 11.5 ish

11.5 is to Fat. Octanee.. You have a Boost-it sled correct? You should be looking for 12.2 -12.4 WOT. Idle 14.2 but if its not wheezing don't worry about it. Mid don't worry about it. Polaris has them running in the 16.1 range.
I can't see running a low comp head. Before boost its going to feel soggy. 2 stroke numbers are NOT the same as 4 stroke.

Octanee · Jan 18, 2019

sledhead9825 said:
11.5 is to Fat. Octanee.. You have a Boost-it sled correct? You should be looking for 12.2 -12.4 WOT. Idle 14.2 but if its not wheezing don't worry about it. Mid don't worry about it. Polaris has them running in the 16.1 range.
I can't see running a low comp head. Before boost its going to feel soggy. 2 stroke numbers are NOT the same as 4 stroke.

good info! yes I'm boost it. and Interesting, I'm unsure then of where I was told that 11.5, could of swore I read it. that being said I'll try leaning my sled out some more LOL. I know my yamaha I think I was told/ran it at ~11-11.5:1 under boost. Figure'd it'd be the same on the 2 stroke...? especially since they need more cooling than a 4 stroke to keep the melt downs away. I have noticed the sled down the trail mid range ish likes ~16:1 or so. Always sort of worried me. And like wise sled idles 14 Ish.

sledhead9825 · Jan 19, 2019

Octanee said:
good info! yes I'm boost it. and Interesting, I'm unsure then of where I was told that 11.5, could of swore I read it. that being said I'll try leaning my sled out some more LOL. I know my yamaha I think I was told/ran it at ~11-11.5:1 under boost. Figure'd it'd be the same on the 2 stroke...? especially since they need more cooling than a 4 stroke to keep the melt downs away. I have noticed the sled down the trail mid range ish likes ~16:1 or so. Always sort of worried me. And like wise sled idles 14 Ish.

I have had a couple of Boost-It Sleds. Neil would tell me to shoot for 12.2. They run real strong there.

Sheetmetalfab · Jan 19, 2019

alfadanne said:
I have a -16 axys with a silberturbo and lowcomp head.
After install of lowcomp head 11.3-1 (because of bad fuel here in Sweden) i have problems getting it to not det, and lots of lag.
Bought a PC V fuel and ignition and started tuning, but doesn’t seem to get it all the way, so i bought a autotune.
But what afr numbers should i aim for? Low/mid/wot?
Is it the same numbers as on 4stroke?
I have tuned cars.
Thanks /Daniel

The silber reflash works extremely well at low elevation here in alaska.

Any reason you decided you wanted to do it yourself? (The tuning)

Put the stock head back in and run straight 100 octane (aviation fuel)

They rip.
No det.

alfadanne · Jan 20, 2019

No one sell AV fuel in Sweden.
Everything works great with the kit if you mix the fuel as silber says ?

richracer1 · Jan 20, 2019

A buddy of mine that had multiple boosted sleds, several in the 300HP range, told to watch for the 12.5 while full throttle.

My '16 800HO with the BD Sidekick Switch idles around the mid 14s AFR, cruising down the trail, 15-16s (5000-6000 RPMs) AFR. If I blip the throttle on the trail the AFR instantly drops to 14 to mid 12s depending on how much throttle I gave it.

In regards to the trail cruising 15-16 AFR numbers, I was a little concerned, so I asked the guy that built the Bully Dog turbo tune I have in my ECU about those numbers, and he stated, "Until the engine comes on the pipe, AFR readings will be overly lean on a gauge but not actually in the engine."

alfadanne · Jan 26, 2019

I have installed a afr gauge now and cant get fatter than 12..... something.
Still dets.
How long will the stock inhectors be enough?
Run at 0 feet over sea.

Octanee · Jan 26, 2019

alfadanne said:
I have installed a afr gauge now and cant get fatter than 12..... something.
Still dets.
How long will the stock inhectors be enough?
Run at 0 feet over sea.

Interesting! What's the air fuel ratios cruising?

Aside that I wonder if your over revving, I'm unsure if the axys will do the same but I read on the pro rmk they will throw det if they over rev. My sled at 5# at 5k feet revs. So fast that It over shoots my rpm then pulls down, I was running 80 gram primary, going to try lighter. I'd imagine the same over rev issue would be worse/harder to deal with at sea level as your also putting out more power as well at 5# than I would be.

TRS · Jan 26, 2019

AFR is only a tool.
Yes there is injector duty that will limit your boost capability.
There are many variables in AFR readings:
1)Where the O2 sensor is located pre or post turbo.
2)Where it is located in the pipe pre turbo.
3)If it is post turbo it may be picking up oxygen pulled back up the pipe.
4)If you are running a race fuel, Different fuels have different chemical makeups, and thereby different stoichiometric ratios.
5)Aftermarket and stock pipes
6)Oil saturation
Just to name a few.
Here is an example. I run a 60/40 mix of 91 nonE/ Sunoco 110 my AFR likes 13.2 at full throttle. My 02 sensor is post turbo. I know another SW guy that runs the same fuel ratio and O2 location as mine, his AFR numbers are in the low 12s. So you can see there isn’t a paradigm concerning turbo setups.
Each setup needs to be tuned to its own particular components. Understanding Plug readings and piston wash is paramount if you’re doing the tuning. You can’t compare numbers with another’s setup. Why do you think more and more turbo companies will not allow their customers to adjust fuel? An AFR gauge is a tool, You must practice and utilize old school tuning knowledge first. Then use your AFR readings as base.

Edit:
I was trying to find an old pic I had of a GM test pipe. It had nearly 100 O2 bungs welded in it. They were testing for the optimum/consistent O2 sensor location.

alfadanne · Jan 27, 2019

Octanee said:
Interesting! What's the air fuel ratios cruising?

Aside that I wonder if your over revving, I'm unsure if the axys will do the same but I read on the pro rmk they will throw det if they over rev. My sled at 5# at 5k feet revs. So fast that It over shoots my rpm then pulls down, I was running 80 gram primary, going to try lighter. I'd imagine the same over rev issue would be worse/harder to deal with at sea level as your also putting out more power as well at 5# than I would be.

Yes the axys do the same when overrev, but mine doesn’t overrev anymore.

alfadanne · Jan 27, 2019

My dutycycle are at 100% now ? at 5psi.
Is it possible find bigger ones?
And where and from what?

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Afr numbers?

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