Did you do your own prom?What does your maf top out at?I wonder if its possible to convert the gr/sec to cfm?At my redline the gr/sec is 236 i think(forgot).What would the 236 gr/sec be in cfm,anyone?

 

CFM x .5663 = Grams/sec

255 gms/sec = 450 CFM

Another little piece of math

1.3 CFM / HP

At 350 HP your of resolution,
thou, you can hammer the calibration to get more, but that's tough on the engine. And can be a nightmare to get the BLs right on it.

 

But the scan tool readout for maf is actual gr/sec or the reading from the gr/sec I inputed from the bin editor to the maf tables?How could corkvette run 11s on 450 cfms of air,something don't add up here?

 

The MAF will still continue to flow beyond that, but it won't register. You can get around that for a while, by adding more fuel via power enrichment.

 

yes but corkvette said his maf does not max out.thats on an 11 second car too.

 

If it is true, he has faulty/miscalibrated MAF or he is getting there with less than 350hp

 

This is what I'm saying,I think the maf tables modify the sensors output/readings.

 

But modding those tables "calibrate" the maf to your engine.So there is no useable conversion from gr/sec to cfm since the madf output can be modified??

 

It is VERY easy to max the MAF in terms of the maximum MAF reading BY THE ECM of 255g/s. That DOES NOT mean that the MAF itself cannot flow more air. The MAF can flow significantly more air ... the ECM just cannot register anything above 255g/s. I was helping a guy with his 350ci MiniRammed MAF car not too long ago and the 255g/s limit was reached around 4800rpms. Extra fuel is supplied via the PE %Change to A/F vs. RPM (and/or vs. Coolant). So - its not THAT big of a deal except in cases where the user is running a much bigger cubic inch engine where the electronics would be maxed out at normal throttle openings ....

Tim

 

I understand the maf can max out at 255g and know abouth the pe% f/a vs rpm compensation fix.But corkvette1 said his maf does not max out on his 11 second ride.I don't know if weight would make that much diff as far as load.He said his other friends maf does'nt max either.I have a 400 cid engine and mine does'nt max out.I have a stock ported intake and a mild cam though.That could explain why mine is not maxing but what about corkvette1?And many others that go fast but don't max the maf?

 

Well, you can force the ecm into an overflow condition.

In the GNs, they have the same 255, NUMERICIAL limit. Again the 255 has nothing to do with air flow, it's just the largest number the ecm can deal with for air flow. On the GNs it happens at 150 Hz. The GN is frequency based not voltage. The instant you excess that, the calibration goes goofy, ie timing get erratic, and injectors mis pulse. Also if you look at the Frequency of the MAF vs the MAF table you'll see that the numbers are no way near linear in nature.

So if you do screwy things with the intake tract you can generate all kinds of false numbers. Removing the screens is a classic. The turbulence increases along with the MAFs output so you've enrichened the engine, by just falsely reporting the air to the ecm.

Another reason for building an ecm bench and reading the code. Till people really understand the code they're guessing, and reporting on stuff that works for them, but it ain't the correct way to do it.

There may be around all of this, but til someone builds a good bench, understands the code, and is will to mule an engine, no one will really know.

A scope with an electric leaf blower might be an added bennie to the bench, using it and two MAFs with some simple electronics might answer alot of guestions.

 

kvu,

You need to give it a break. There was absolutely NO indication in corky's post about NOT maxing out the electronics. You are thinking that he said that he was not maxing out the electronics but the fact is ... he never said that. His basic point was that you can run fast with the 165 MAF system and that is very true. Furthermore, it was plainly obvious that he did not understand the issues behind maxing out the MAF. He was focusing on the fact that the MAF can flow enough air to run good times. That's it. I can guarantee that 350ci cars in the 11's at over 3000lbs will be maxing the MAF at 255g/s. I've seen plenty of mid 12 cars max out at 255g/s. But, that doesn't mean too much since the MAF will flow more air and more fuel can be supplied in the PE tables. There's really nothing further to this subject unless somebody comes along to discuss 165 code changes to eliminate the 255g/s limit. Yes, MAF systems can run fast ... even when the 255g/s limit is hit relatively early in the powerband.

Tim

 

Like you said ,I misunderstood the statement.I think you misunderstood something too ,my friend trax.I was never trying to defend a position on maf and how fast it can go.I have put alot of time getting my 400 tuned and it's fast enough for now.I am suprised the maf is not maxing on me though.I guess the corkvette guy dont know much about maf.

 

I never said that you were trying to defend a position on maf ... so, I misunderstood nothing.

Tim

 

kvu, could you list the gm/sec flow per RPM that you are experiencing? Also, if you ever have had your engine dyno'd I'd be interested in that. I am currently studying those relationships and trying to gather as much data as possible.

Also Injector PW would be interesting at those various RPM levels.

 

.Why are you telling me to give what a break?I'm trying to understand a post,how was I beating anything to death?I don't care who you are but it's rude to TELL people what to do.[quote]I never said that you were trying to defend a position on maf ... so, I misunderstood nothing.[/qoute]ok,next quote..Now tell me trax,what is your problem?I am trying to understand maf better by exploring everything.Comments like that are counter productive to my learning.Listen guy, I'm sorry if I offended you somehow.

 

I'm nobody. This is the internet. I call it like I see it and feel it. Don't take it so personal ... that's not me telling you to not take it personal - its a suggestion. The 255 thing has been going on for a long time ... a very long time. A search of the archives would reveal that. A search of the GMECM archives would drive the point home. I've seen it so much so the first thing that comes into my mind is 'give it a break'. Its not a command. I am not telling you what to do. You will do as you see fit. Like I said - this is the internet - its not real life.

My problem is as explained in the previous paragraph. But, its not a problem ... more of a seeing the same thing over and over and over and over again. Past topics are rehashed. Then they are rehashed again. Then again. Everyone emphasizes search search search ... few people do that (I am not saying that you don't do that - just saying that's why topics get rehashed over and over). I understand that comments like that can be counter productive to anyone's learning. Oooops. Sometimes chit happens. Its not personal. This is the internet. Just trying to get my point across without having to type 2000 words. Sorry if I offended you - was never my intention. Can we give it a rest now? (wow - I used a question. Normally I would have just said 'give it a rest'). I'd rather not lock this post because you and I are having an off-topic discussion. But, I need to follow my own rules.

Tim

 

Thanks for being civilized,no need to ramble on here.:rockon:

 

kvu and trax-good to see things not escalate! I've found that it's not easy to "hear" inflection and meanings in the typewritten word-so I try to be carefull with my wording-but yea "chit happens"!
OK, nuf said there; back to the above-Glen-if you're collecting data for a "project" I'd be glad to send you diacom logs etc. Just let me know. I'm currently just hitting 253 to 254gps at 6100 rpm. I havn't dynoed it with all the latest mods-soon to be done however. With 30lb Accell inj. my pulse width at 6000rpm is about 6.5ms now. With wide band tuning I've got the F/A at 12.8:1 at all WOT rpm's right now. With the previous 24lber's it was up to 8.5ms at 6000-and that was before the addition of a Super Ram. I have "modified" my maf-so I don't know how much that effects it. Hmmmm, after I pay off my Visa (soon) I might just pop the $$$ for a new maf, leave it stock, throw it in and see what the gps shows then for a comparison. What the hey-it's only money!

 

Guy i just read a post from grumpy and saw thi conversion:
MAF Math:
Grams/sec=CFM*.5663
1.3 CFM per 1 HP
.75 Grams/sec = 1 SAE HP ***
If .75 g/s = 1 hp does that mean in theory you will see your peak
g/s @ peak HP? (assuming you are not hitting the 255 limit.)
Ive seen my peak @ 6000 of 243 so am i making 324 HP?
I assumed that GPS would just raise w/RPM.
I to have modified my MAF and can see the danger in that but i guess you have to make a compromise calib or airflow,as soon as my money permits i would like to make the switch to SD also
but for now im gonna play and learn.

Thanks for any help.