I have read all the links in the stickys for tuning how to's but I have never seen exactly what the methodology for tuning is for MAF.

I have been trying for about a year now but am having limited success.

The approach I had been taking was to set the INJ constant to get an average of 128 for all my BLM cells and then adjust each using the MAF tables and the OPEN LOOP % change VS LV8 table.

The METHOD for doing this has been to drive and datalog the engine and then come back and make my changes. I export the logfile into excel and sort the data into BLM cells. Then plotting the BLM's vs time for all the cells I can see where they needed changing. Needless to say I am not having much success this way.

I am considering changing my method to the following more structured approach.

having the car warmed up I would log the following,

1. idle,
2. free rev the engine to progressively increasing airflows

This should give me a map of A/F vs airflow for the lowest loads possible.

Then put the car in manual 1st (auto trans) and drive stairsteps of speed again focusing on getting a map of airflows at this higher load.

Repeat for 2nd, 3rd and Drive (assuming I could go that fast).

I think this would give me what I would need to:
1. Set the MAF tables up (from the low load park test)
2. Set the OPEN LOOP % CHANGE vs LV8 table up (from the driving tests)

Does any of this make sense???

 

I'm no expert, especially on the MAF side of things since I drive a 91 (speed density), but one of the cardinal rules I've always heard was to set your injector constant and cylinder size to the correct values and then leave them alone. Use the other tables to bring the BLMs into line (not the injector constant). Otherwise all your PE and WOT stuff will be way out of kilter. At least that's my understanding anyway.

 

Yeah thats what I'm beginning to think was my first mistake.

But I am commited to starting a new chip with the correct Inj constants

But wait -- if I have an AFPR and it is set higher than stock 47PSI then shouldent I set the inj constant to a number higher than what the injectors are rated for at 40?

 

I would think so, yes. It should reflect the actual output of the injectors as I understand it.

 

Joe Georger's Home Page
Go here there is a flow rate calculator.

 

Thanks that calculator helps!

 

If you have to ding with fuel pressure to get enough fuel, then the correct solution is getting enough injector.
Once you get enough injector, then enter the correct values, and go from there.
The low speed *opening lag* differences between injectors should be taken care of with the PW, vs BatV corrections.
If you have higher flow area errors, then you might be seeing reversion raise it's ugle head, and while you can work around it, that gets very time consuming.

In a long run the easiest cure to the MAF reporting errors, is going SD. Yep, it's true.

 

I'd definitely NOT start tuning the MAF table with just free revving. I'd do it with load, and get the PWs up above 2.4ms at least. If you have a manual transmission, it's much easier, where you can hold load points easier. Then, once those are fully straightened out, you can free rev into the light load areas where the PW is low, but the flow is higher. Then calibrate the Injector offset vs Base PW table to get the lower PWs but higher MAFs to match the same BLM as the higher PWs but same MAFs.

Injector Offset vs VBatt can be used to straighten out the idle MAF table 1 a little in order to get a fairly straight MAF table there. If you see the table require a sharp hook at the low flows, try raising or lowering the Offset vs VBATT. If you have to make changes to this vbatt table, you may need to redo some of the other MAF tables by a small amount to bring them back to the previous desired BLM.

Clear as mud?

 

Grumpy,

I only raised FP to 55 psi to give me effectively a 22 lb injector instead of the 19's that came with the 305. I only expected a small increase over the stock power levels.

RednGold,

with that said -- why wouldent I start with the lowest load possible?

ARAP makes no corrections for load below LV8 of 48. I would think it would be harder to tune with varying levels of load because then more than one table could be to blame.
See the thing is I can reach all the values in the lower tables in free reving at a low LV8 so the only variable would be the MAF tables themselves, Coolant temp, and the battery voltage. Only the MAF would need changing as the other two are constant.

And I dont really understand how changine INJ PW vs. BATV is going to help at varying airflows... my battery voltage changes very little from idle to cruising speeds... Also, are you talking about the INJ PW CORRECTION for SMALL PW? I havent looked at that table yet -- but I dont see it in the tunerpro list so Ill add it.

 

LV8 has nothing to do with fuel.

Yes, INJ PW CORRECTION for SMALL PW is the table, although it's labeled as what I stated in my previous post, in my XDF (which I made a lot of, so not sure what was there before, and what I added).

Do all of your initial tuning at warm engine. Do injector flow rate first. Then, I guess you do have a choice. You could do idle and MAF table 1 first and make changes to VBatt Offset. Then medium to high load MAF Tables, then go back and do Injector Offset vs Base PW to make same airflows at different RPMs match BLMs. It's a little Rubik's Cuby when dealing with MAF that's not calibrated on a bench, and with injectors of unknown properties.

 

Alright then, sorry if I seem to be arguing, I just want to understand why the tables you suggest should be used. I do not want to dogmatically use one set of tables if I dont know why or how they are to be used when others seem to so naturally apply.

Why does LV8 have nothing to do with fuel when there is a table that corrects base open loop fueling with varying LV8?

I would think that this table like all the others, is a part of the rubik's cube.

I hear what you are saying about the batt voltage table but exactly how do I effect a change only in the lowest table when the voltage doesnt vary between tables???

So here is what you suggested I think:

warm engine up (+165F)
Set INJ single and double fire size to my actual values.
Then use the INJ v BatV table to tune the idle mix?
Then change upper MAF tables that you call high load while driving under load?
Then change INJ corr v small PW? for the change in load at the same airflows?

This does not make sense to me since there are tables specifically for corrections in LV8 (load).
I would think one would use the following method:

Warm engine

Set INJ size to correct

Use lower values of MAF table 1 to acheive good mixture at idle speeds along with CLOSED LOOP RICH/LEAN mv table if 14.7 is not what the engine wants.

Then use MAF tables 1-6 or as many as can be gotten to in free rev to tune to proper mix a low LV8. Taking note if any tune points exceed LV8 48 ( this is where the table OPEN LOOP % Delta vs LV8 will add fuel)

Then use OPEN LOOP % Delta vs LV8 to tune the mixture at higher loads.

Thanks for all the help -- I am really appriciative.

 

Oh wait -- could it be that the OPEN LOOP % AFR delta vs LV8 table I have been changing is not used during closed loop fueling?

 

Big question is: Are you using $6E or 32B?

 

Yes, open loop fuel tables are not used during closed loop fuel.

Use VBatt for lowest table because VBatt offset is of minimal effect, at most loads, EXCEPT idle and low loads. But low loads and high RPMs can have the same airflow as high loads and low RPMs. That is why there you need to correct PW vs Base PW. Small PWs are not linear fuel flow. In this case, go and fix the medium and high loads that have linear fuel flow, and then go back to the low loads and high RPMs to fix the PWs due to being small.

 

Then only expect that slight error to be dramatically increased as the code processes the error. It all adds up.......

It allows for the opening time differences in the injectors.
Just increasing the fuel pressure changes how fast an injector responds to the ecm's signal. Again, it all adds up.

You gotta have an accurate foundation to build your tune upon, or you will have headaches down the road.

 

Might just try some of the advise before replying.
Replying with *opinion* or *I don't think so and so matters* is just wasting BW.

 

$6E

I still dont understand how the Vbatt vs PW has any less effect at low airflows than high.
So lets say I am lean at idle MAF (7-10 g/sec). How would I increase this with the battery voltage table? why wouldent I just move the MAF values?

However I do now understand the PW correction vs request is the one way to change the fueling vs load.

 

Just blindly following orders is not the way to tune grumpy.

I wouldent even know HOW to change the tables mentioned to effect the change I want.

If you dont want to explain why then what is the point of this board?

 

The VBatt offset is always used. It becomes a larger portion of a smaller total PW. To idle at 14.7 (don't care what your BLM or INT is), it needs X PW. If that X is mostly Offset PW, then the MAF airflow will have to be low. If that X is less, then your MAF airflow will have to be more. In MAF table 1, there may be a slight curve. IF the curve starts to go level at the lower flows, your Offset may be too low, thus falsely requiring more Airflow in the MAF tables, and vise versa.

But, yeah, the main idea in a MAF setup is to adjust the MAF tables to keep things mostly in line. The offsets are the fine tuning aspect of it all.

LV8 is mostly used for spark and open loop AFR changes.

 

So the "injector pulse width correction vs. battery voltage" table is only adding pulse width in a very small amount? Compared to the pulse width at lets say cruise?

OK I am beginning to see the light here. so my engine idles at ~2.0 msec PW and if I look at the MAF table it says 7 g/sec and the batt voltage is 13.3 V which by the table adds .5 msec of PW at all airflows.

So if I want to lean the engine here I would reduce the Batt offset PW.

So then I have an additional question -- where would I use the "Injector offset for small pulse widths" table? It seems to add PW when low PW's are commanded and would cover .5 - 4.0 PW's. That seems to be the same area that would be effected by the batt correction except it would ONLY add PW to the low commanded values.

Last question -- how do I account for changes in load at HIGHER airflows. Like you said, "low loads and high RPMs can have the same airflow as high loads and low RPMs".
Is there some table that gives a correction for load at the same airflows ABOVE 4.0 msecs?

 

MAF Table, which is where I would start.

Yes

No, VBATT table is not "meant" to actually richen or lean anything. It's meant to allow the fueling to come out of the injector in a calculated manner. Fuel injectors turn on slowly and turn off slowly. This offset is to compensate for that, so that the computer can calculate fuel flow vs MAF flow with a linear response.

This is why I say that if your MAF table REQUIRES some curve in the lowest flow ranges, then maybe your VBATT OFFSET is not quite correct. This means you could change the VBATT OFFSET and then RE-CHANGE the low MAF table.

It is used to make the calculated fuel flow (using a linear equation) match the non-linear injectors. The larger PW calibration uses all MAF (+ VBatt, but VBatt is only there to compensate for injectors latency, not for rich/lean), and should be fairly linear. The smaller PWs may show different BLMs, but for the same Airflow - HOW? Well, it's because of this offset table for small PWs.

 

Thanks Jeremy, You have helped me a great deal.

 

My pleasure! Hope it's all accurate enough.