Speed Density LFX engine, what is needed ?

[benf]

What PID's do I need for making sure my Speed Density numbers are where they need to be? I tuned my MAF both cruising and WOT along with PE already. MY LTFT's are +/- 3 for the most part. My WOT commanded is appx 2% off the actual, but i am working on getting it closer.

I never did anything with Speed Density before. Most of the info out there is for v8. So, what do i need to scan to make sure i don't need any changes to speed density?

2012 LFX(NA) running on e85.

thanks

[HackAbuse]

Fail the MAF out, then drive it and see what your trims do. Generally I've found that the stock maps arent too far off if it's a near-factory vehicle

[MarkTucker]

Well it depends on how you have your tune setup.

But stock tune the MAP sensor calibration is disabled at 4,000 rpms.

Tuning the MAF Calibration should be all that you need to do to dial in your fueling.

They do offer a Virtual VE Table for your ECU, to convert to Speed Density. By disabling the MAF.

[benf]

thanks for the replies. I did create the virtual ve table but I have to assume the reason it is blank is cause I didn't turn off my maf? I plan to keep running using maf, but thought I should see if map is ok since switching to e85. I noticed since upping the tb size and other pieces that I have to lower my airflow hz numbers. Also I am still trying to figure out the sweet spot lambda for wot. I have upped my PE to .774 lambda commanded, but wondering if I should richen it even more as it seems to run decent at .75ish lambda. Thoughts?

In addition to the e85, I also have the up sized TB to 80mm with the matching ported intake and lower intake spacer. The TB intake tube has been changed to 3.5" to match the tb size change. Hi flow cats on the exhaust side and x pipe.

[MarkTucker]

.774 and .75 is to rich for a direct injection.

Did you add a flex fuel sensor and wire it into the PCM? And enabled flex fuel control?

Or did you just retune entire PCM for E85?

[benf]

I have a sensor added. When I look online I see any where from .71 to .76 as max rich and up to .85 for max lean. I based my .774 from what one of my friends was running with an identical setup. He had someone remote tuning his. There isn't a lot of info out there for direct injection v6's. What do u think is an ideal for my motor?

[MarkTucker]

.85-.86 would be a good safe starting point for direct injection. Might possibly lean it out to .87-.88 once timing and fueling is dialed in.

.71 is about 10.5:1 gasoline afr (which is really rich even for a port injection car)
.76 is about 11:1 gasoline afr (which is still really rich for port injection, but getting close to that safe range for boosted port injection)

Most AFR/Lambda target guides that you see online are for based for port injection/carburetor engines.

[benf]

I was appx. .87 lambda when I was on 93 octane. I thought when going on e85 you should be appx 30% richer? my summer blend is appx e75

if u look at the factory alchohol pe table, they too have it set for a .75/.76 lambda 11.3 gas afr

[MarkTucker]

Gasoline(0%Ethanol) Stoichiometric is 14.7 = 1 Lambda
E85(85% Ethanol) Stoichiometric is 9.7 = 1 lambda

So to achieve E85 Stoichiometric from your existing Gasoline Stiochiometric calibrations, you must increase your calibration by approximately 34%. Being that it takes about 34% more fuel of E85 to achieve 1 lambda, than gasoline.

(9.7 / 14.7) = .6598639456
(1 - .6598639456) = .3401360544
(100 x .3401360544) = 34.01360544%

[benf]

since we are both saying the same thing, we need at least 30-34% more fuel, then why do u think I should have me commanded lambda set to .85? That is very close to where I was on 93 at .87 lambda. I am trying to find online the formula to show % differences of fuel delivery with different lambda's.

Ex. going from .87 to .85 is what % enrichment?

[MarkTucker]

Cause we are discussing lambda.

Gasoline AFR 14.7 = 1 lambda
E85 AFR 9.7 = 1 lambda

Gasoline AFR 12.5 = .85 lambda
E85 AFR 8.2 = .85 lambda

You do not need to change your target Lambda because of Ethanol Percentage change.

[benf]

so if I understand what you are saying, leave my pe the same I had on 93 octane but increase the maf for the desired actual lambda...then I will always exceed my commanded

[MarkTucker]

I am saying .85-.86 lambda will be a good safe starting point for gasoline or ethanol fuel, then you can lean it out once everything is properly dialed in.

And if you have the Flex Fuel Sensor and Tables all setup then, no you should not have to rescale the MAF Calibration. Cause the PCM will be able to rescale the Stoichiometric of the fuel based off of the Ethanol %.

[benf]

Update: this morning I changed my commanded to .85 and realigned my MAF at wot to be close to commanded. I also made a change to the Fuel Flow Rate Alcohol multi by going from 1.0 to 1.010 in the 62.5-87.5 range. Made a couple logs and am fine tuning the MAF back in. Do you think I need to add more to the injector multi?

[MarkTucker]

Here is a stock table from a 2014 Chevy Silverado that comes factory with the flex fuel sensor equiped.
Injector Flow Rate Alcohol Mult.png
So this will be a good starting point for you.

[benf]

yes, that helps..i see they jacked it up appx 30%..at least now I am on the right track

[MarkTucker]

That's not 30% by the way.

Example: 75% = 1.0299
(108.9 x 1.0299) = 112.15611
(108.9 / 112.15611) = .9709680552
(1 - .9709680552) = .0290319448
(100 x .0290319448) = 2.9%

[benf]

so,if they are only changing it by 3%, then how do you compensate for the e85 to give the extra 30% of fuel?

[benf]

thanks for ur time, what a learning curve on these DI v6's. Looking at my tunes from before e85 my commanded was between .87 and .88

[MarkTucker]

Engine>Fuel>General>Air Fuel Ratio>Stoich AFR
Alcohol Composition.png

Like I mentioned above, if the Flex Fuel Sensor is enabled and setup. There is no need for adjustments. The PCM will change the Stoichiometric based off of the Ethanol %