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Discussion Starter #1
I just read out my fuel trims and my LTFT's are at 9%.
I remember Jim Hall saying they need to be as close to zero as possible. I adjusted my MAFT to 5% rich to get the LTFT's at 9. Is that close enough to zero? Would setting the MAFT to 10% rich bring it down closer or too far?
 

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RE: MAFT Settings

I've gone over those MAFT threads pretty close.

The way I see it, if your at +9% trim still.

And the MAFT is at +5%.

You were originally at +14%.

The system is adding 14% more fuel to hit 14.6:1.

So thats where you need to set the MAFT at (+14%) to get to 0%/nominal.

You've only adjusted it to 5 when you need to go to 14.

So go 9 more positive.

When you set it at (+) it's actually subtracting (-) and visa versa.

You want the MAFT to tell the system to NOT add 14% more fuel.

Make sense?
 

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Discussion Starter #3
Yea it makes sense. I was running lean after my mods (could tell by looking at the plugs) When my MAFT arrived I set it a 5% rich just as a guess till my scanner came in. There is no 14% rich setting but I'll try 10 then 15 if I need to. thanks.
 

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I wish someone would do a detailed How-To on this with pix!! :cool: I haven't been following all of these threads :roll: but the stuff is starting to interest me. :yeadog:

Looks like time for me to do a search. :D
 

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So at +15 your going to take away 1% more at WOT.

Now you can use your second control setting (WOT) to dial in WOT.

Now your starting at -1% at WOT.

Thats should be O.K. as long as WOT is still starting out on the rich side.

WOT remember, is preset in the program.

Power Enrichment Mode.

Now check your AFR at WOT. Are you above or below 12.7:1.

You've stopped the part throttle calibration from ADDING fuel to that number and now your taking 1% away.

Now check your AFR at WOT. Are you above or below 12.7:1.

If your UNDER (lean) turn your calibration setting to MINUS until you reach 12.7:1.

If your over (rich) turn your calibration setting to positive until you reach 12.7:1.

Your telling the MAFT where you are, not where you want to be, thats what confuses everyone.

Part throttle is now back to close to nominal, so the system can swing up and down (adjusting to 14.6:1 constantly) and work within the diagnostic ranges it was designed for, in case something is wrong (like an actual component failure) and can tell you so. And WOT throttle is properly recalibrated for MAXIMUM power.

Done. Now drive it, like it was built to be driven!

And enjoy!
 

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Discussion Starter #7
fcalmes said:
I wish someone would do a detailed How-To on this with pix!! :cool: I haven't been following all of these threads :roll: but the stuff is starting to interest me. :yeadog:

Looks like time for me to do a search. :D
Yup, I think toying with these things is still fairly new but there probably are still a few guru's out there. One thing is for sure......
Those of you that doubt that intakes dont make a difference, I can tell you for 100% certainty that they do, even never having dyno'd my car. With a T1, screenless MAF, and gutted pups, my PCM was adding approximately 15% more fuel to allow the engine to run the optimum AFR due to the added air flow through the engine. This can only equate to one thing......More Horsepower!

I also have figured out the MAF/MAFT/PCM relationship in a language that probably anyone can understand. I'm putting together a short explanation on this topic and will post it shortly. This has been explained many times before by people way more knowlegeable about tuning than myself but the language was maybe a tad too technical for most to understand.

The bottom line is that the ZO6 is not as difficult as you might think to tune. The hardest thing I've found is understanding how to interpret the results of your scanned information. For example it's known that your LTFT's should be at or near zero. Easy enough.....but there are 2 sets of LTFT's on the scan.....B1 and B2....which one or both do you look at and what is the difference between the two? Short term fuel trims (STFT's) have 6 different banks of information...1,2,11,12, 21,22....which one of these are for WOT? And what are the other one's for?

Anyway, my project is going very well and I will make final adjustments to the LTFT's today. Then I can drive it for a few days to let the computer learn the new info, then start dialing in WOT. Thanks for the replies so far....they've been helpful:cheers:
 

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Discussion Starter #8 (Edited)
MrZ06 said:
If your UNDER (lean) turn your calibration setting to MINUS until you reach 12.7:1.

If your over (rich) turn your calibration setting to positive until you reach 12.7:1.
The service manual states that the PCM maintains 14.7:1. Did you mis-state the value or are you saying that 12.7:1 is what you want to aim for at WOT and 14.7:1 is the PCM's goal at part throttle?
 

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Discussion Starter #9
Another question.....The GM service manual lists a procedure to follow for rich or lean codes. I've assumed after reading this that you want to read your LTFT's with the engine idling for 5 minutes with your coolant temp between 167-239 deg. Is this the right way to read them for tuning purposes? I assumed it is since while your driving, they are constantly changing.
 

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Thank YOU for the methodical way you're going about this and relaying the pertinent info.

My EASE stuff is on the way as is my MAFT which I'll use til the LS1edit stuff becomes available.

I'll be right behind you on this stuff. I am going to make an educated guess and say that bumping the A/F ratio from a super-rich (in my case) 10.6:1 to 12.6+:1 will net 10-15rwhp ... with that change alone. Time will tell.
 

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A lot of good info is starting to come out of this.... I too am interested since I have the T-1 on my car. Keep up the good work guys..... :cheers:
 

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Yes Ripper,

That is exactly what I'm saying.

Part Throttle setting

WOT setting

The gathering of the accurate fuel trim numbers we might want to ask Jim or even c4c5, Jim seems to have spent enough time checking trim numbers. There actually may be some specifics to gathering them for the most complete accuarcy. I'm honestly not sure about that particular data gathering method, I usually ask a tech to provide me with that information.

Back to settings: This is where Jim Hall said in his posts, when he eventually told his "secret", that he was dialing in WOT at, to get his BEST numbers on the dyno. Which is what we all want.

The rest of the instructions are all derived from some of the confusing posts. Primarily this is what you get from how Butcher did his and what Jim Hall has said. Just more straight forward.
 

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a/f ratios

I would like to ask..... if your increasing the air flow and fooling the PCM with the MAFT to force the stock injectors to work to their full capacity(maybe beyond), wouldn't you really need to add #30injector to balance the system out properly?
 

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Here is an interesting "site of links", the Injector Calculator they use offers a safe/unsafe zone listing along with alot of links to other sites with other calculators, hence the - car math name.

Kinda neat, you can even e-mail the guy to add useful formulas. I'm assuming it includes duty cycle to keep you in the zone, so you can come to your own conclusion.

If you actually know your factory injector size for sure, you can check. Or you can plug in the injector your considering! Don't forget to use the Horsepower you EXPECT to put out with your mod's when calculating. Give it a try! ;)

www.cobralads.com/car_math
 

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MrZO6. Thanks for the link. Lots of different ,usefull formulas.
 

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There seems to be some confusion on the MAFT adjustments. To quote from the RamCharger instruction document "Zero is the 'no change' position with clockwise rotation increasing fuel delivery (richer), and counterclockwise rotation reduces fuel delivery (leaner)".

Also, when scanning to measure your LTFTs, you do not just idle for 5 minutes. That way you will only measure the LTFT in the "idle" cell, cell 20. Not very useful.

There are 23 cells (0-22). Each cell has a LTFT value.

Cell 22 is WOT (defined as TPS > 80%). Cells 0-19 are "part throttle" cells, each one defining a portion of the MAP vs. RPM map. Cell 20 is the "idle" cell, the one you would read if you just idled. Cell 21 is the "over-run" cell, lifting the throttle for engine braking.

To tune the part throttle LTFTs to zero, you want to get an average of cells 0-19. To do this with a scanner, you drive around using many rpm and throttle settings, then edit the scan to remove cells 20, 21 and 22. Then average the remainder.

You also measure the left and right O2 sensors and average them together. This tells you your AFR. There are no left and right LTFTs, just one value for each cell. Ignore the STFTs.

When this part throttle LTFT average is near zero or 1-2% negative, do some WOT runs and average the cell 22 LTFT values. To do this you get to drive *fast*! This is the fun part. But watch out for the cops.

HTH, Jim Green
 

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Hey Mr. Z06............that is a great site..........but according to the calculator...........you will need #30lb injectors for any HP gain over 427HP!:eek:
 

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I believe that's at 40psi, without checking the math.

That's why I put that little part about what H.P. you expect to run. Like I said, its also taking into consideration duty cycle apparently, at 40psi, but not higher presssures, most injectors I beleive are rated at 43psi. The Z06's higher psi also has to be considered, what is it 58psi? Thats another 15psi or 35% of pressure. That math also should be done. That should effectively lower your duty cycle while increasing your lbs/hr. By the way, stock injectors usually start locking up around 80psi just for reference. Some supercharger FMU's will take them up there, typically thats why some S.C. company's start talking injector upgrades. A good Bosch injector shoudn't shut down till 100psi.

Test:

Based on the following information a 24lb @43psi/85% duty cycle injector @ .5 BSFC in a corvette actually flows about? What?

Effect of various pressures on a 30lb injector.

From T.P.I.S. flow test at 85% duty cycle.

They (the mfg) probably test at 80% duty cycle they don't say, that's probably why it flows 30.90 at 40psi, the point is the effect of pressure changes:

psi lbs/hr H.P.

30 psi - 26.55 424
40 psi - 30.90 494
50 psi - 34.76 556
60 psi - 38.62 618
70 psi - 42.50 680

According to this a 30lb injector @ 58psi should be worth about 600 h.p.

So what will the corvette's injector support?

42.50-30.90=11.60
11.60/2 (30psi/2=15psi)=5.80
5.80/30.90=.19 increase
.19x24=4.56
4.56+24=28.56lbs @ 58psi

the car math analyser says for 405 H.P.:

psi needed at 24lbs for 405hp will be 58psi or

a 29lb injector at 40psi.

I know this will raise more questions, but sooner or later we're all going to need the same book if we're all going take the same class. :)
 

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injectors

MrZ06
Thats some very fine calculating your doing there!
Maybe, I am being too simplistic.........but if you just factor in that 35% by multiplying it times the base 24lb stock injectors..........you get about 32lbs..........which the "calculator" now make it a max of 460hp!
That should make everyone feel better?cheers:
 
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