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MPI Stage 2 Apex Questions

D

Darin Ostertag

Newbie
Joined
Aug 30, 2016
Messages
9
Location
Minnesota
Country
USA
Snowmobile
2006 Yamaha Apex Mountain MPI Boosted
Hey everyone,

I picked up a 2006 Yamaha Apex Mountain. It has a MPI Stage 2 supercharger, stacked head gasket, 25/25 pulley (1:1 ratio), GEMS fuel controller, MPI BOV, custom exhaust, MSD high flow electric fuel pump, factory motor. It's running about 13 lbs of boost at 900 ft elevation. Issues I'm having. It starts a little hard, idles a little rough, and cuts out under hesitates at certain throttle positions. Pulls hard otherwise. Watching AFR I'm seeing 14.1 at half to WOT..which is too lean. Gems box settings: mode 1 is 5, mode 2 is 6, mode 3 is 3.5, mode 4 is 6, mode 5 is 2, mode 6 is 8. Does increasing those numbers add or subtract fuel. I'm not hearing any lean pops and it doesn't seem to be hitting the rev limiter but runs not so great. Any suggestions or advice is welcome. Trying to tune it before going out west in February. Any techs to live in twin cities, MN area that I could pay to help me dial this beast in?
 

The higher the number the richer it is. Make sure to find the GEMS manual to understand what your playing with. My settings in my sig would get you close for MN elevation.
 
kinger said:
The higher the number the richer it is. Make sure to find the GEMS manual to understand what your playing with. My settings in my sig would get you close for MN elevation.
Click to expand...

I would be interested in what setup your running and what your settings are kinger.
 
Ok
kinger said:
I run a head shim for 10:1 CR and 10-11 psi on Stage 1 blower. Settings are in my signature. It wont be perfect but it would be good to double check M5 and M6.
Click to expand...

Ok I'll start with that. Thank you. Stage 2 has a little more going on than I anticipated. What do you run for fuel and oil type at low elevation?
 
I plan on running 91 with BND Automotive ACES IV +P fuel additive and octane booster.
 
Look into Torco for octane booster that actually works I used it once with a tank of 87 and motor lived happily, it works as advertised. At 13 lbs you need more like 95 octane. There is a octane calculator in the stickies at the top of the turbo/SC forums. I used it to generate the max boost I could on our 91 crap fuel. Do you have 2 or 3 stacked gaskets?
 
Can you be more specific on hard starting, rough idle? Sounds like a fuel issue. A good test is to unplug the GEMS and leave it off, connect the harness and than start and idle it. If the conditions are the same than its something fuel related. Possibly a clogged fuel filter or a bad after market pump. If it goes away you have a bum GEMS module. Seems like the two most likely culprits for the scenarios you described.
 
I know I have 2 gaskets for sure, maybe 3. I am going to mess with the GEMS tomorrow morning and try your settings. I'll keep you posted on how that goes. The ACES product is supposed to be even better than Torco. Guy that created it is world renowned and is a chemist specializing in fuel. He said with 1:1 ratio of his product to 91 fuel (1 oz additive per gallon of fuel) I would be just fine. It richens it up and changes a dry fuel to a wet fuel. I will be testing that additive this weekend or early next week. Lots cheaper than 110 race gas and easier to bring out to the mountains.
 
Well my very knowledgeable buddy and I did some tuning and test riding today. It's now running pretty well, but still lean at mid to wot. It idles at 1 lb of boost with an afr of 14.6. At crusing speed and wot it hovers around 14.1. It has a few burps in the mid range but otherwise seems to run pretty well. Here are my gems settings: mode 1- 4.5, 2..5, 3..
 
Continuing...mode 1...(4.5), 2...(5), 3...(7), 4...(8), 5...(4), 6...(8)

Maybe the gems and my fuel system are maxed out at sea level?

Highest boost I've seen is 14 lbs. Hitting the rev limiter at wot so I'm going to add more weight to the primary.

Clutch engages at about 4300 with a yellow silver yellow primary. Any ideas on how to get more fuel, adjust gems? Clutching recommendations?
 
Where is your O2 sensor placed? Did you try unplugging the GEMs and starting it? See if the Afr changes. Also make sure the little hose from the IC to the GEMS is intact and not pinched. If you search CO settings maybe you can richen them up.


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