Misfire WOT mcxpress 180

[stricklandj]

2013 nytro xtx with 180 mcxpress kit getting misfire on WOT. Running at sea level and getting 8.5psi boost. Too much boost cause misfire. Plugs gapped at .26.

 

[06 apex yamcharger]

install new plugs gapped at .18

 

[stricklandj]

new plugs but didn't go that tight, wasn't sure where I'm not pushing that high a boost

 

[mbarryracing]

What is your AFR?

X2 on re-gapping plugs to 0.018"

 

[stricklandj]

Don't have my afr hooked up anymore, tunnel dump exhaust, reading were good before I removed it

 

[mbarryracing]

So are you saying you just went to a tunnel dump exhaust? Did your misfire happen since you did that?

 

[stricklandj]

Unfornunately I don't know that forsure because before I did the tunnel dump I had clutching issues so I wasn't doing a lot of WOT. Added tunnel dump and did my clutching at the same time. Do you think tunnel dump would effact things? MCX you can't adjust your AFR.

 

[zx4ever]

Just putting this out there. Could it be the rev limiter. It really sounds like a miss fire. And if you gained horsepower and did some clutching it would be worth checking out. Also need the plugs gapped at .018

 

[mbarryracing]

Just putting this out there. Could it be the rev limiter. It really sounds like a miss fire. And if you gained horsepower and did some clutching it would be worth checking out. Also need the plugs gapped at .018

X2, you have a couple new variables that you didn't have before...
Yes changing the flow characteristics of your exhaust will change the tune.

 

[stricklandj]

yah I wish I didn't make both changes at once..easier to troubleshoot. I pretty sure it's not the rev limiter, my buddy who also rides turbo nytro, thinks misfire. I'm leaning towards boost blowing out spark with wider gap. Going to get boost down to 6 psi and change gap

 

[stricklandj]

Would the flow characteristics change that much where the exhaust is after the turbo?

 

[mbarryracing]

Yes, affects back pressure... Same reason the stocker's don't run the same when the header donuts are burned out...
and like you mentioned, the MCX has a set map designed for use with their exhaust system so if you uncork it and flow more air it can affect the tune AND BOOST LEVEL.
Also what boost level is the MCX180 map good for if you are over 8 lbs? And no AFR gauge????

I'm with everyone else, I'd first just start with re-gapping the plugs tighter to 0.018", watch the tach and see what RPM it misfires at. If it's right off the bat when you wack the throttle WFO, I'd lean more towards it's likely hitting the rev limiter before the tach catches up.

Beyond that your taking a stab in the dark troubleshooting a turbo sled without an AFR gauge...

 

[titanrcr]

Don't have my afr hooked up anymore, tunnel dump exhaust, reading were good before I removed it

My first step would be to get that AFR working !!

 

[stricklandj]

She is apart now so I can get my o2 sensor installed. Pulled the new plugs to gap.....pretty white!!!!!