It's because your fuel pressure drops when the voltage drops.

 

If it dropped it would go lean I would think...cars going rich...idk...

 

well, it’s still doing this crap...I noticed the cooler or humid it is out the worse it gets...tuber thought voltage was dropping and suggested new battery but battery tested good...u guys have any other ideas?

 

As well as having your fuel pressure cocked up, your SD will be done wrong too.
You need an AIT sensor in the manifold.
Otherwise the tune drifts with the change in weather.

 

Apparently you've never tuned an Evo. They run fine using fuel temp in place of IAT.


OP, did you ever try a new or known good MAP sensor?

 

Car used to run fine...I switched the Omni 4 bar with my friends and it was the same so that’s ruled out...it has an iat sensor...it gets worse when humid or cold but still does it when normal out...

 

A log will reveal the real story.

Please check the O2 sensor and battery.

 

ok I’ll see how I can figure out how to log and post it on here...

 

I bought a new o2 sensor and went to auto parts store to check battery...they said battery is good but still doing the same...

 

For those who haven't yet figured it out......

SD means speed density.

The density part of it means air density IN the intake manifold.

That is measured using a MAP sensor for the pressure part of it.
It is measured with an IAT sensor for the temperature part of it.
Air pressure IN the manifold and air temperature IN the manifold make density IN the manifold.

Fuel temp will never work accurately because fuel temperature is not air temperature.
In which case it isn't an SD tune it's a SP(speed pressure) tune which nobody uses because it doesn't work accurately enough.

If you're not worried about accuracy then just stick a carburettor on it.


Maybe mr wannagetitdone should stop posting bull**** information?


edit......you need a new toooooner too.
Fancy suggesting you need a new battery?
Stop paying a boy to do a man's job.

 

I think I've moved from disgust of ignorant misinformation to just profound laughter every time I see a RightSaidFred post now. Lol. Good times.

 

So you don't agree on the definition of "speed density" then?

You're a "tooner " too?
That's right....you've been toooning for 20 years and using a WB for 20 years but they've only been on the market a bit over 15 years.

This man knows a bit.
Just a bit.


Reverting to a MAF tune will fix most of it.
Not all of it.

 

Can’t see his posts anymore however to speak to the “you need an IAT” comment that was quoted above, ummm no, just no.

Been through all seasons on SD w/o an IAT and the car runs fine. Please get a life. Thanks

 

First of all, don't state I said something I didn't and secondly, Bosch would 100% disagree

 

Damn... Every thread gets ruined by fuel pressure problem