I have an evo ix with the usual mods (tbe exhaust, mbc, intake + custom dynoflash).

I was driving back home on the highway tonight and when going WOT in 5th gear I peaked about 21psi and at around 5k I noticed the car had a slight stumble, I have never noticed this before, any ideas what this is?

Do you think the car is running to much boost, and possibly knocked and went to its low octane protection save my motor map (im a newb).

In 3rd gear my peak boost is set at 23 psi according to my boost gauge which I know is inaccurate but should be getting my zeitronix goodies soon.

 

describe the stumble...were you getting backfires? you possibly need to check your plug gaps...i believe they should be .024 if they are bigger they could be getting blown out with the boost you are running. Just let me know how that works!

 

It probably pulled some timing on you... Was your car warmed up?

 

The car seemed to be unreponsive for a second and made a groaning sound.

What would a backfire sound like?

 

Yes but the stupid temperature gauge is pretty meaningless imo, and I don't have an oil pressure gauge. I drove around like a pansy for about 10 minutes, until the temp gauge was in the middle, maybe I should have waited longer.

 

boost cut plain and simple. Crank up the boost a little more, and the cut is more pronounced. Temperature also affects it greatly. Make sure you turn it down a pound for every 20 degrees or so drop in ambient temp.

Be thankful you have it.

 

It may be boost cut but unlikely... He said a slight stumble. Boost cut would feel like you hit a wall for a second. It was most likely the ecu pulling timing. You need to drive the car for about 15mins before your oil temperature reaches its optimal temperature. If the weather is real cold it may take a little longer.

 

Its about 46-48 degrees in NJ so its not terribly cold. The car did not have a CEL or anything, and I think that occurs with fuel cut, and I didn't hit a brick wall or anything. I guess I'll take it very easy driving in the cold weather.

I guess I had knock and the ecu pulled timing. Thanks for the quick responses guys.

 

now that you mentioned, I had a similar hickup today when accerlerating onto a highway from 4th to 5th. It kind of felt like a minor stumble. I have not added mbc but just TBE. Never felt anything like it w/ my VIII. Weird...

 

^IF your not tuned then I think it is most likely fuel cut.

Search for "fuel cut" and you'll get some hits.

I think hiccup describes it the best.

 

Probably the ECU pulling timing. The coolant temperature gauge actually does a pretty good job of telling you when the coolant is warmed up. When the needle settles into its "warm" position, the coolant has reached normal operating temperature (about 180F). The engine oil does take a bit longer to warm up. I usually wait until the oil temperature gets up to about 60C on the MR oil temperature gauge before I start boosting heavily.

Anyhow, if you have access to a laptop computer, you can use EvoScan or Mitsulogger to find out if the hesitation is due to timing being pulled. You can also find out a bunch of other stuff about what your engine is doing.

 

What rpm's did it happen ?

Usually, higher boost is seen on 4th and 5th gears than 3rd with a mbc.
But you have a 9 so maybe the mivec changes that a bit.
.

 

What would I need to determine if ecu is pulling timing (cables/programs). Do you think changing the sparkplugs would have any effect, in any?

Some afterthoughts: I usually run a bit more boost in the summer and have no issues going WOT from 3,4 and 5th. I also filled up some gas with a gas station that I have never used before (it was a Mobil + 93) so maybe they had a bad batch of gas? (I'll double check the receipt to ensure it was 93 when I get back home)

 

You'll need the Tactrix cable ($94 shipped, this is where most people get it):

https://www.evolutionm.net/forums/sh...d.php?t=202422

You'll need one of the two logging programs for the Tactrix cable:

EvoScan ($25):

http://www.limitless.co.nz/

Mitsulogger (Malibujack's free, more advanced, slightly more complex logger). Look about halfway down the page on Aktivematrix. You'll need to signup on the website to get access to the file.

http://www.aktivematrix.com/

And you'll need a WinXP laptop PC with a USB port. Its pretty close to an entirely plug-n-play setup, but it takes some background reading to understand the datalogs. You'll probably want to start doing some reading on the ECUFlash subforum:

https://www.evolutionm.net/forums/fo...play.php?f=179