Greetings: Observation: WOT at 2000 rpm and 82 gr/sec my stock 350 and my modified 383 both hit the max air flow vs rpm table (89 gr/sec) and ride all the way to 255. Tried two Bosch and a wells type all read the same. I would have thought the 350 would have been lower and never hit the max table till 255. What do you think? Question: Does anyone have WOT data log of a stock 305, 350 or modified 383 ? Needs to have at least rpm, tps and gps. If the Max air flow vs rpm table has been altered I would like to know that. If so can you send it to me? I have datamaster and excel so any of these format's would work (.uni .csv .text .xls .ods) I want to plot a graph RPM vs Gr/Sec to see what is “normal” vs “modified”. Comparing to Max air flow vs rpm table. Thanks

max airflow vs rpm table can be moddified to allow the computer to read more air at certain rpms.


a more modified engine will pull in much more air than a stocker, so you need to adjust that table to allow the ecm to read more air at those lower rpms.

a hot 383 will max an air flow sensor at 255gr/s at sometimes 4000-5000 rpms.

I know my HSR bolt on L98 wouldnt go over 205gr/s at 5000 rpms. Table value i'm not sure of at this moment but it is well over that. So the ecm is capable of reading more air and making changes

I understand that the table can be changed. am getting prominator for the 383.

The question is at lower gr/sec flows (wot) why would a stock 350 tpi flow enough air to be near the Max air flow vs rpm limit @ 2000 rpm ?

If the max air flow table is reached, then the ecm will limit fuel at that gr/sec.
This will make for lean/rich spots in the factory tune. The view on this board is that a stock 350 will not reach this limiting table. It looked like mine did so I was tring to get some hard data to see if this is so.

I am looking for someone else's data log on a stockish 305 or 350 to compare to.

It has to do with the maf calibration, I think, which would be nice to know when tuning. After reading posts where tuner's have adjusted the lower maf scaler tables for rich/lean and got no change.

I got a bunch of Maf's all read differant at max flow 187 200 205 255.
also they hit this number at differant rpm's.

Maybe someone who is tuning with only one maf would get some insight to the variances with age that maf sensors show.

Thanks for the reply.

pandin, I hope you dont mine me posting here.

Is the max air flow VS RPM table "looked" at continually?????

I have been under the impression that it was backup in case the MAF malfunctions.

If it is looked at continually, if the MAF reading is above the value in the max air flow VS RPM table (for a given RPM) does the fueling equation use the value from the table????

It is all about volumetric efficiency(VE). 383ci more airflow potential, but probably has a bigger cam. This would make the 350 and 383 flow the same air at 2K RPM. At higher RPMs (3500-7000+), the 383 will outflow the 350 with the proper cam and equiv. intake & exhaust.

Your 2K RPM CFM points being the same is due to VE (cam,heads,intake).

Greetings Doc and junkcltr glad to have you join my post.

For anyone following this.

Check out RBob under tech boards-DIY prom-Prom tuning Guide book and Faq-Chapter 5 Tuning Articles broken down by ECM-165-Maf Miscellanea-

First Post by RBob:

"This value is then tested against a maximum value. The maximum
is from a lookup based on RPM." (Max Air Flow vs RPM? pandin) "If the calculated value is greater then the max allowed by RPM then the max value by RPM is used as the gms/sec term.

Otherwise the calculated value is used as the gms/sec term."


Also RBob 3rd Post

"10) The gms/sec term is then tested against a
maximum airflow based on RPM. This is from the
table as descibed in a previous post.

-done calculating the gms/sec term-"

He goes on to explain LV8 math.

Thank you RBob for all the knowledge.

If a stock 350 can bump this table then everybody that is using a maf is affected, to some degree, by it. It will shorten the pulse width (lean) when against the table.

Wrong time of year to test this. but was looking for somebody that maybe had a data log saved from the past.

Shouldnt be bumping your head on that table at the lower RPM's with a stockish 350. I looked at some older log files and I wasnt hitting it with a modded 350 until the 170 gm/s range, so around the 3200+RPM mark. My supercharged 305 was hitting it way before that, I saw some defaults down in the 2300RPM area and that wasn't at WOT.

Thanks madmax

What was the moded 350 gr/sec at 2000 rpm ?

Mid 70's.

Thanks