MCX 270 Tuning/Altitude display changing on boost?

[Hillclimber]

I have been dialing in my new Viper with it's MCX 270 kit. I've been having some interesting issues, figured I'd throw them out here for the forum to chime in on. By the way, I love the new ride!
For preliminary testing, I've been running about 10 lbs of boost, at 9,000-10,000 ft elevation, clutching is good and it is not hitting the rev limiter.

The viper has a little backfire from the intake, (located outside the hood) at 4600-4800 rpm right before it gets into the boost, not a big deal; the real issue is the bogging after it gets into boost. It feels like it's getting too much fuel and I've been watching the A/F ratio drop from 12ish to the low 9's once it gets into the turbo. As long as you don't mash the throttle, it will usually clear and rip thru the mid range, but will bog again at the top. It is ride-able, but it is enough to throw you off your line and disappointing that it only barely out-climbs a race gas turbo Polaris! I should be dominating that bitch.

We had to dial back the stock fueling on my MCX 240 turbo Nytro, not sure if this is necessary or possible with the Viper.

I am double checking with MCX to make sure the gen 5 controller is paired with the correct injectors.

One thing I noticed when riding last time, is that the altitude display is all over the place, starting with the correct altitude and by the time the bog hits at 5lbs, it is down to 2,000 ft. Seems to me that would be enough to confuse the stock mapping and could be the source of the bog. I plan to check and see where the dealer/installer has the barometric pressure sensor is located. Wondered it any of you noticed the same thing on boost.
Any thoughts?

Thanks,
HC

 

[MCXPRESS USA]

Call me @MCXPRESS USA 406-782-2318 Thanks Mark

 

[Hillclimber]

Thank's for the conversation Mark, I'll report back after the weekend!

 

[Martens199]

Have you had any problems with a backfire when the sled gets into the high side of boost? I can't get my sled up over 13 lbs without it backfiring. It will also backfire when the sled is shut down under load (pulling the tether). Think these are rich conditions, Seems to be a common problem right now out here.

 

[MCXPRESS USA]

The 270 responses is so quick when you hit the throttle it can hits the rev limiter depending on your clutching. Then you can get a back fire and not sure why.
MCXpress Sweden recommends a heavy flat profile weight so it does not hit the rev limiter

 

[stingray719]

The 270 responses is so quick when you hit the throttle it can hits the rev limiter depending on your clutching. Then you can get a back fire and not sure why.
MCXpress Sweden recommends a heavy flat profile weight so it does not hit the rev limiter

Rev limiter drops fire to plugs not fuel, so when it comes off limiter it fires the unburned fuel and backfires.

 

[Martens199]

Yeah those are the weights I'm running, the ones from MCX. Only thing I have done is unplug the TCV and that seems to keep my boost around the 13psi mark at 8500-8800 rpm WOT, then It doesn't back fire. but once the TCV is plugged in I can't even give it half throttle and it back fires. When this happens I only ever see 9000 rpm. But its hard to tell with a digital gauge.

 

[MCXPRESS USA]

MCX just came out with some new weights, Not sure if those are the one's you have.
You also can recall your max rpm on your digital gauge

 

[Hillclimber]

Mark nailed it, MCX specified in the installation instructions that the hose from the barometric sensor get tied into fitting on top of the inter-cooler.
I'm sure this works fine at sea level, but at higher elevations, this can cause the altimeter to bounce around and as I noticed, surging boost and rich conditions.
As Mark suggested, I cut the line, left the sensor end open and tucked out of the way, plugged and sealed the end going into the inter-cooler, and presto, problem solved. Sled ran crisp and clean boost all weekend! I may need to start lifting weights and bulk up to be able to hold on.
Thanks MCXPRESS USA!
Without all that extra fuel messing up the A/F ratio, I noticed the 4500-4800 lean condition and corresponding backfire is even more pronounced. Come on Mark, please finishing testing your updated map and lets get this beast dialed!
HC

 

[Armani]

Thank's for the conversation Mark, I'll report back after the weekend!

I wish i could listen to that conversation, i`m allso wondering if that barometric pressure have something to do with mapping and MCX TCV valve?
At 2800 ft on gps my Viper displaying 3900 ft

 

[Martens199]

So your saying to remove the hose on top of the intercooler and plugg it
Off going into the cooler of coarse, and then let the hose disconnected hang loose? No problems with the hose plugging up?

Mark nailed it, MCX specified in the installation instructions that the hose from the barometric sensor get tied into fitting on top of the inter-cooler.
I'm sure this works fine at sea level, but at higher elevations, this can cause the altimeter to bounce around and as I noticed, surging boost and rich conditions.
As Mark suggested, I cut the line, left the sensor end open and tucked out of the way, plugged and sealed the end going into the inter-cooler, and presto, problem solved. Sled ran crisp and clean boost all weekend! I may need to start lifting weights and bulk up to be able to hold on.
Thanks MCXPRESS USA!
Without all that extra fuel messing up the A/F ratio, I noticed the 4500-4800 lean condition and corresponding backfire is even more pronounced. Come on Mark, please finishing testing your updated map and lets get this beast dialed!
HC[/QUO

So your saying to remove the hose on top of the intercooler and plugg it
Off going into the cooler of coarse, and then let the hose disconnected hang loose? No problems with the hose plugging up?

 

[Hillclimber]

So your saying to remove the hose on top of the intercooler and plugg it
Off going into the cooler of coarse, and then let the hose disconnected hang loose? No problems with the hose plugging up?

That's what I did, I have the open end of the hose tucked down in front of the engine, facing down. I don't think there is any chance of debris getting in there.
A screw and liquid electrical tape are sealing up the hose on the intercooler, but next time I am by the auto parts store I will look for a more official plug.

 

[Martens199]

That's what I did, I have the open end of the hose tucked down in front of the engine, facing down. I don't think there is any chance of debris getting in there.
A screw and liquid electrical tape are sealing up the hose on the intercooler, but next time I am by the auto parts store I will look for a more official plug.

Now this just helped your bog, not the intake backfire correct? Still have the burp at 4500-4800 rpm? I also have this.

 

[Hillclimber]

Correct, the burp is still there. From what Mark and I discussed, there is a lean condition in the MCX map for that rpm range. When I watch my Air/Fuel gauge it runs 11-12 just over idle to the low 4000's, hits 17-18 at 4500 to 4800, then it backfires. Once you get further into boost, the A/F drops back down to normal.

 

[Martens199]

You think this line dissconnect is something save to run at lower altitudes as well? Around 3000ft
Want to leave it off, but wondering if is save to run with it disconnected at low altitude as well.

QUOTE="Hillclimber, post: 1217101, member: 9693"]Correct, the burp is still there. From what Mark and I discussed, there is a lean condition in the MCX map for that rpm range. When I watch my Air/Fuel gauge it runs 11-12 just over idle to the low 4000's, hits 17-18 at 4500 to 4800, then it backfires. Once you get further into boost, the A/F drops back down to normal.[/QUOTE]