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Target AFR's for Nytro with supercharger or turbo

S

SnoBird888

Expert
Joined
Sep 4, 2013
Messages
354
Location
Neenah, WI
Country
USA
Snowmobile
09 Nytro xtx
Hey everyone. Finally got over to TY after years on HCS. Selling my 08 rtx and got an 09 xtx with the mpi +45hp supercharger kit. I have tuned many turbocharged vehicles in the past in the 15-28manifold psi range but never a sled. The sled targets like 6-8psi which is perfect for 91 octane. I want to swtich over to the power commander for tuning but not sure what afr these things like esp with the 9k rpm range. I would generally think 14.7 for low cruising loads but the supercharger is almost instant pressure raise over the large vacumn the engine produces so at what point do you guys start to richen it up psi/throttle position wise and how rich do you run it at wot in the higher rpms? A generic target afr table would be great to work off of as well

thanks everyone for the help.
 
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Please add your location to your site profile, thanks.

Most boosted sled guys will run as low as 12.8-13 while cruising, and 10.8+/- at WOT.

It's different for each setup though as you probably know, but it is largely depending on your fuel and ignition control system that you use, and how effective your intercooler is. The basic fuel controllers like the Dobec style only sense boost and add fuel. You technically have to overfuel them with this setup to avoid detonation. (11:1 compression stock)
If you have a more sophisticated system that will control the timing advance/retard as the boost increases, or better yet one that will also retard timing and richen the mixture if air or water temps get too high, you can then run leaner fuel mixtures for more power.
For a basic setup I wouldn't run 14.7 in any condition other condition than idle.. (maybe)
If you get the fuel controller with timing control, you typically want to retard the timing one degree per pound of boost, but the fuel table isn't necessarilly as straight forward.
Depending on which fuel controller you choose, post it up and someone will be able to help you get a base map to start with.
As far as your question regarding when to richen the mixture, that may be something to experiment with. I don't currently run a centrifugal blower, so mine is different, but I think most guys that are begin to add fuel right around clutch engagement speed. There isn't a need to be rich around idle when the engine isn't under load, and doing so will likely hurt driveability.
I'd start adding fuel from around 3500, and go from there.
 
Wow thanks for the fast replies. I planned to stick with just fueling for now unless a timing setup is really needed? I didnt realize that the stock CR was 11:1 so they much be around 180psi depending on the cams i guess. I have to do more reading on the system installed on it now by Yamaha/MPI but if given a choice what would you guys run? GEMS is what the mpi one is? Wish i could just hold my laptop and go out on the trails and record it and change all the parameters i can with ECUflash on the wrx/stis.
 
Hi SnowBird88
I run the same system with 28/28 pulleys on 92oct.
My afr with gems:

Idle 14.xx

Cruising, still negative or 0 boost 13.xx afr

@ WOT i have gems set to max fuel on red and green-blue mode and that gives me 12.x afr.
 
Idle: 14.5-14.7
Engagement: 13.5
Slow cruise: 13.5-14.0
0 lbs boost: 13.0
5 lbs boost: 12.5
10 lbs and over: 11.8-12.0
 
Awesome guys, exaactly what I was looking for. I suppose cruise is around 6 to 7k rrpms so low 13s makes sense compared to a turbo caar engine.
 
Evolution Powersports has a remap for the stock nytro Ecu that pulls timing at the higher rpm ranges. This is a good setup for a supercharged engine as the boost is dependent on rpm. Shoot me a pm if you want more information.
 
im gunna bring this back to life. i never got the cash to go Forced induction but finally go my wideband installed this past weekend with an ecxell exhaust and K&N filter kit. Idle when cold is about 11.8-12 and when warmed up 12.5. seems pretty rich to me just at idle. reving it up steady after stays in the low 12's. Would anyone be willing to share with me the autotune map for an NA nytro? even just a picture or general guideline?
 
That does seem a bit rich, which wideband did you get and what was its calibration procedure? Also, where was it installed in the pipe?
 
I have the brand new style aem uego with the 4.9 sensor. they are all calibrated from factory so cant recalibrate like on the lc1/lc2 sensors from innovate motorsports. Never used an AEM before only lc1/lc2 tuning cars and never had a problem> i read a ton about them and professional shops tend to use them in the automotive world so figured it accurate and will last.

I mounted it 6" past the collector outlet. They recomend 18" at the very least from the valves. 32" if you run at high rpms. Pretty sure I am about 20-24" right now and it only affects sensor life.

The map I am running doesnt add fuel to about 3500rpms and 5% throttle.
 
I think your sensor is in the right place, and you shouldn't have too many issues with it as far as life goes unless you run race fuel in it, or run consistantly very rich.

I don't have much on the PC map for you so I'm not going to be much help there, but if you're familiar with the program, you can start taking away fuel. Start in the idle area, and remove fuel by about 10% at a time. Just be sure top not have big jumps in numbers from one box to the next, and try to adjust a small block of numbers at a time.
If you get the afr's in the range(s) that have been posted earlier, I think you'll see more power, and it'll help the life of the sensor as well.
 
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