Fuel Cut Good, Right?

[TalonJohn94]

In theory, fuel cut is a GOOD thing right?

I mean, yesterday I loosely (no 4wd launch/power shifting) raced my friend yesterday. My 94 AWD 5-speed has:

3" Exhaust (no cat) w/Thermal R&D muffler
2g O2 Housing
Ported EVO III 16g w/34mm Flapper (only 13 psi)
K&N Filter
SAFC set to 'safe' settings (like +8 on most RPM points)
About 20 degrees outside last night
93 octane

My friend has a virgin (80k original miles) late '89 Eclipse GST (K&N filter, Magnecor Plug Wires).

Anyway, I pulled on him at first, until 2nd gear fuel cut, 3rd gear fuel cut and then backing up at about 80 mph.

But again, I know I need to get a fuel pump and bigger injectors and probably a 2g MAS. But for now, isn't it good and safe to be hitting fuel cut?

My friends behind us said I was "smoking" - but I don't burn oil (20 degrees remember)
That's my other question - what does running pig rich look like from behind the car, what color smoke?

Thanks for answering NEWBIE questions.

 

[psychlow]

Smoke will be black if you're running rich.

At only 13PSI and getting fuel cut, I'd suspect you have a minor boost leak to find and fix, especially if you're puffing black smoke at WOT.

Fuel cut is caused by the ECU reading too much airflow. If you change the pump, it will still fuel cut. If you change to larger injectors and retune using a piggyback, it'll stave off FC so it'll be harder to hit.

You didn't mention if you've got a logger - if not, I would get one. Also, richening your SAFC settings probably isn't helping the situation in this case.

If you are running rich, keep an eye on your oil as well, sniff it on the dipstick and make sure you can't smell gasoline in it. If you can, change it immediately - what's happened is that gas has washed down into your oil, which will remove pretty much all of its viscocity and lessen its lubricating properties.

 

[TalonJohn94]

I have a logger, it says 100% DC in spots.

I have noticed OIL pressure dummy light come one, despite the gauge reading adequate pressure. Also, I JUST did an oil change and the oil looks darker than usual. (Castrol GTX 10w-30) Finally, when I check my oil there are usually bubbles on the dipstick. BTW I relocated my oil feed source from the head to the oil filter housing.

I better drive carefully until I figure this out.

Can you elaborate on how gas would get in my oil?








What equals more blowbye, rich or lean?

 

[CanadianTSi]

Set the S-AFC to 0, it is making the car see to much air thus you are hitting Fuel Cut.

 

[psychlow]

Can you elaborate on how gas would get in my oil?

What equals more blowbye, rich or lean?

I'm at work, so I'll have to come back and tell you more when I'm out of training (which will be in 8 hours) but I'll tell you what I can now.

If you are running too rich, not all of the fuel will be burned in the combustion cycle. When the piston raises back up to TDC, the fuel will work its way into the grooves on the combustion chamber and get past your rings. This will end up going down into the oil eventually, but not before removing all of the lubrication on your cylinder wall. Gasoline is a solvent for oil, which means it'll break it down.

Since you'll have no lubrication on your cylinder walls, your rings will quickly wear off all of the crosshatching on the cylinder walls, and your oil seal ring will fail, leading to poor compression, blowby, etc.

More on this later.

 

[psychlow]

The followup to this, since I'm on break ATM:

After the oil sealing ring is worn down, gasoline will start to enter your crankcase directly, breaking down all of your oil. Run too rich, or let this go too long, and you'll end up with spun bearings and other fun stuff like that.

In addition, since you have no oil sealing, you're going to get tons of oil blowby in your combustion chambers, so you'll blow white smoke.

To answer your question, both will cause equal blowby, rich or lean. Rich will destroy your rings over time due to wear, lean will destroy everything in your combustion chamber from heat and detonation.

 

[TalonJohn94]

OK, thanks a lot. So its KNOCK vs. FUEL CUT.
I was thinking about buying these soon: 2g MAS, DENSO 650's, 190 lph fp, EGT gauge, + Tuning (among other mods)

What do you think?

Winter is here, and in WI that means storing and hopefully working on car(s).

 

[psychlow]

Those will definitely help you raise your boost and make more power. At the moment, though, tuning and further problem diagnosis will likely solve your current problem.

 

[ninety7gst]

don't quote me on it but i believe delphi makes the 650 core injectors, and denso makes the 660, delphi is much cheaper tho so that's what I went with on my car...

 

[TalonJohn94]

what kind of affect could this have on my new turbo?