4 FOX SNAKES - Ross' 20vt 4kq

[loxxrider]

I don't understand this damn car. When tuning for 24 psi I added a bunch of fuel, even at the current boost levels. It wasn't scary lean but it was slightly lean. No biggie. So I tuned up to 24psi and put in some more fuel as we went, and the fuel curve was spot on. Today I took the kids to church in it and noticed some misfires or ignition breakup above 5k (boost for God!) and so I took a log with dad and again the car was running lean, but more this time. So again I added fuel, and now it's good again. Seemed to help the ignition issue slightly but it's still there. I also haven't driven it since tuning on Friday so it's not like anything changed. Anyway, it's back to where is supposed to be. I wonder if the fuel filter needs changing or perhaps it's just the more dense air. But really that's why you leave EGO correction on... To compensate for those small environmental changes. Bah.

A 10 degree swing in temp can make a huge difference in the tune... your MAT correction may not be up to snuff.

[chaloux]

It was cold both times, around 0-5 degrees C. I'll look into it.

[EDIGREG]

As Chris said, the MAT enrichment table is responsible for compensating for temperature change. Closed loop only gets you so far, and even then - it should be disabled at peak boost

[bradyzq]

Hmm,

Was boost actually the same in both instances?

Was the car still in closed loop in boost? If so, how much authority does the ECU have to compensate? There's nothing wrong with leaving it on. Just be sure that you don't give it enough power to blow up the engine if the wideband flakes out.

The MAT fuel correction should be about 3.0-3.5 percent richer for every 10degrees C cooler, low throttle/heat soak areas notwithstanding.

And yes, you should change the fuel filter! Isn't that part of the "new to me" maintenance regimen?

Cheers,
Brady

[bradyzq]

Oh, one other thing:

Do all the sensor inputs make sense?

Garbage in ...... garbage out....

[mushasho]

13,000!!!

[chaloux]

How do you disable it over a certain boost level? Didn't know taht was an option. I have it set to the "stock" settings of 10% rich, 15% lean currently. I'll go over all the advice you guys gave, thanks for that.

Guess I'm in for a fuel filter at least

And the real problem is the misfires up top. Step 1 is check plugs, step two is check 60-2 gap, step three.... I dunno. On another note, I really need a heat shield in between the EM and the intake hose. Or switch routing/intercooler setup. The 3b is pretty dumb to go right near the hottest part of the entire engine bay.

[EDIGREG]

How do you disable it over a certain boost level?

Go to the EGO page and the option is "disable over xxx kPa". You can also disable by throttle, coolant temp, etc.

[chaloux]

Well shoot. Also thanks for the info re:60lb injectors. Like I said I'm at 84 percent now. But I need to confirm fuel pressure before that means anything. do you have any old maps/configs I could look at?

[chaloux]

13,000!!!

Booya! On a stinking plain ol' AAN swap nonetheless!

[loxxrider]

Hmm,

Was boost actually the same in both instances?

Was the car still in closed loop in boost? If so, how much authority does the ECU have to compensate? There's nothing wrong with leaving it on. Just be sure that you don't give it enough power to blow up the engine if the wideband flakes out.

The MAT fuel correction should be about 3.0-3.5 percent richer for every 10degrees C cooler, low throttle/heat soak areas notwithstanding.

And yes, you should change the fuel filter! Isn't that part of the "new to me" maintenance regimen?

Cheers,
Brady

That is a good point about the closed loop authority.

Matt, I'd set it up to where it can add fuel, but not subtract (especially at WOT). There's nothing wrong with being a bit too rich, but there is a lot wrong with being too lean. If your tune was off by more than the ECU has authority to correct for, that could easily explain the difference you were seeing. I think you need to show us a log with EGO disabled.

[Mcstiff]

Hmm,

Was boost actually the same in both instances?

Was the car still in closed loop in boost? If so, how much authority does the ECU have to compensate? There's nothing wrong with leaving it on. Just be sure that you don't give it enough power to blow up the engine if the wideband flakes out.

The MAT fuel correction should be about 3.0-3.5 percent richer for every 10degrees C cooler, low throttle/heat soak areas notwithstanding.

And yes, you should change the fuel filter! Isn't that part of the "new to me" maintenance regimen?

Cheers,
Brady

That is a good point about the closed loop authority.

Matt, I'd set it up to where it can add fuel, but not subtract (especially at WOT). There's nothing wrong with being a bit too rich, but there is a lot wrong with being too lean. If your tune was off by more than the ECU has authority to correct for, that could easily explain the difference you were seeing. I think you need to show us a log with EGO disabled.

Doesn't this assume that it's not going to read a misfire as lean and dump more fuel? The safest seems to only have closed loop active for cruise and only with a very narrow range of correction to avoid over correction in either direction.

[bradyzq]

Doesn't this assume that it's not going to read a misfire as lean and dump more fuel? The safest seems to only have closed loop active for cruise and only with a very narrow range of correction to avoid over correction in either direction.

Yes, the wideband can be led astray by exhaust leaks and misfires, among other things. It's not the job of the wideband to correct misfires or exhaust leaks though! Basically, you're suggesting using a wideband only under conditions where a narrowband would work better!

What is needed here is a good open loop tune to use as the wideband's "zero" point. And, even before that, actually, we need to make sure that all sensors and actuators are doing what we think they are!

Oh, and I seem to be preaching this all the time lately, is your fuel pump relayed correctly? VERY important especially when you're pushing things fairly hard!

Cheers,
Brady

[loxxrider]

Hmm,

Was boost actually the same in both instances?

Was the car still in closed loop in boost? If so, how much authority does the ECU have to compensate? There's nothing wrong with leaving it on. Just be sure that you don't give it enough power to blow up the engine if the wideband flakes out.

The MAT fuel correction should be about 3.0-3.5 percent richer for every 10degrees C cooler, low throttle/heat soak areas notwithstanding.

And yes, you should change the fuel filter! Isn't that part of the "new to me" maintenance regimen?

Cheers,
Brady

That is a good point about the closed loop authority.

Matt, I'd set it up to where it can add fuel, but not subtract (especially at WOT). There's nothing wrong with being a bit too rich, but there is a lot wrong with being too lean. If your tune was off by more than the ECU has authority to correct for, that could easily explain the difference you were seeing. I think you need to show us a log with EGO disabled.

Doesn't this assume that it's not going to read a misfire as lean and dump more fuel? The safest seems to only have closed loop active for cruise and only with a very narrow range of correction to avoid over correction in either direction.

In my experience, misfires don't have enough duration to cause the EGO to react much. 10% enrichment generally wont be the difference between a good tune and a rich misfire if that is what you're getting at.

I'm still not quite sure if I understand your concern though. With the closed loop fueling, you really don't have much to worry about. It used to be more experimental with VEMS, but it seems to be fairly decent these days. You can get the tune dialed in for open loop, then enable the EGO to add/pull ~10% under most conditions. I used to do it up to 200 kPa with good results. At WOT, I still prefer the open loop, but I don't really see any reason not to at least give it authority to richen the mixture.

What are you worried about? If you're getting misfires at WOT, EGO isn't going to make it any better or worse in my opinion. You've got to go back to your open loop tune if you're getting misfires due to fuel. If the concern is with a spark-based misfire tricking the ECU into thinking the mixture is lean, therefore dumping more fuel in... well... the mix already isn't getting burned... who cares if it is a bit more rich? That isn't the kind of situation that will wash down cylinder walls if that's what you mean. To me, EGO can do no harm by being set to enrich.

[chaloux]

I don't think the misfires are related to the fueling but I could be wrong. It feels to me either like a dying coil (now that I've killed two of them) or plug. If it's a coil it's in the early stages. Maybe tonight I'll have some time to check things out. I'm pretty exhausted with this car to be honest I have to put the snows on the other two cars, but maybe not for a few days/weeks yet. And I need a new clutch/fw on the jetta.

I'll have a closer look at a log and check over all the settings you've been talking about. If I lift just a little bit the misfire stops. I did change the dwell multiplier to 4 instead of 5 (thought maybe too much dwell was killing coils, but now I think it was the heat), so maybe that is having something to do with misfire in the more dense mixture? Regardless I have a few things to go over.

Plugs, base fuel pressure, pump relay, mat enrichment, redo fueling again, ego on full boost, etc.

Thanks guys.

[loxxrider]

I don't think the misfires are related to the fueling but I could be wrong. It feels to me either like a dying coil (now that I've killed two of them) or plug. If it's a coil it's in the early stages. Maybe tonight I'll have some time to check things out. I'm pretty exhausted with this car to be honest I have to put the snows on the other two cars, but maybe not for a few days/weeks yet. And I need a new clutch/fw on the jetta.

I'll have a closer look at a log and check over all the settings you've been talking about. If I lift just a little bit the misfire stops. I did change the dwell multiplier to 4 instead of 5 (thought maybe too much dwell was killing coils, but now I think it was the heat), so maybe that is having something to do with misfire in the more dense mixture? Regardless I have a few things to go over.

Plugs, base fuel pressure, pump relay, mat enrichment, redo fueling again, ego on full boost, etc.

Thanks guys.

Not to make things more complicated, but that most definitely sounds like an ignition misfire. I had a very similar problem which ended up being plug wires arcing out (I went through three sets of brand new wires before I found out that the company making them was just shit). So you're certainly blowing out the spark, the question is, "why?" Plugs should definitely be first on the list, then maybe play with plug gap. If the rest of the stuff on your list doesn't pan out, look into the wires.

[chaloux]

So as is, "conditions for enabling" section of the ego page, maximum MAP is 210kpa. So I assume that means disabled over 210kpa. Great! I checked the mat enrichment table and I did add some correction as per Brady's advice. Now to go out and drive.

Oh. Plugs looked great. Not white but not black/greasy/wet.

[chaloux]

I wonder if this is my lower dwell setting showing up on the more energy dense mixture. I'll change that setting back to 5 from 4 to see what's up. Also, Chris, the plug wires are from Marc, and they're brand new.

[loxxrider]

I wonder if this is my lower dwell setting showing up on the more energy dense mixture. I'll change that setting back to 5 from 4 to see what's up. Also, Chris, the plug wires are from Marc, and they're brand new.

Mine were from 034 first, then I think two sets from Marc... all brand new, and the same brand. I am pretty sure he stopped carrying them because of the problems, but you never know. Going back to my stock wires cured the issues I had with all of the new "better" wires I was using.

[chaloux]

So the coil charge map scale setting actually makes a huge difference.  I haven't had the car out yet but I'm almost positive that's what's going on.  If it doesn't change then I 100% believe it has to be a physical problem, wires/coils etc as you said, Chris.

Check this page out: http://vems.hu/vt/help/v3/v3_ignition_settings.html

3 : 40% reached at 616 kPa, and 2.2% at 100 kPa.
5 : 40% reached at 400 kPa, and 3.6% at 100 kPa.

So 4 is obviously somewhere in between 3 and 5 but you get the point.  

Going to drive the car to work today, we'll see how it goes.

[chaloux]

Still there. Seems to be... okay sometimes. I dunno. Coils wires plugs coils wires plugs coils wires plugs coils wires plugs coils wires plugs coils wires plugs

[chaloux]

Or: smaller gap or more dwell? I could go from 2.5 to, say,3. Our leave it at 2.5 but increase the ramp up. My other coils had died by this point so I don't really think it's a coil.

[chaloux]

Fixed it. Dwell to 2.7 from 2.5. Apparently these coils produce great voltage but need the dwell to do so. And they can handle higher dwell times.

Good.

Lost traction quite badly. WEEEEE

[chaloux]

Plates came in today! Can't wait to put them on.

I'm thinking I want to go through all the suspension/rubber mints and replace everything and then get an alignment. What are my options to replace all those bushings? I know 034 carries a lot for the older chassis cars but man, holy $$$. I just want it totally fresh and ready to go.

[EDIGREG]

Nice... traction is overrated

I don't know much about the smaller chassis parts sourcing, but I think there are quite a few cheaper options available from powerflex / energy / etc?