E40 VE Tuning using MAF Numbers

[Tiffer]

I am definately gonna try this bluecat. I have the exact same scenario as 5 litre eater, and i tried the MAF VE Error thing before which threw things out just like trying to tune with AFR Error.
One thing i did notice - changing the VE values threw my AFR out even though i had "disabled" SD and was running in high speed. So VE is always there...I am sure if I get the VE right I would have to change the MAF cal as the MAF cal is probably compensating for the wacky VE...

[Tiffer]

Bluecat you are a legend I had pretty much given up on SD tuning, but tried your trick last night. After a short log and some interpolation I had a VE table that didn't resemble a minefiled for the 1st time. Flashed it and logged again and wow - the mass, ve, and dynamic airflow were all pretty much inline, and my wideband wasn't as all over the place as before.
I still need to do some fine tuning because it did show up some slight changes needed in the maf calibration, but this seems the business.
With this method used for a base VE table, I am sure there would be a way to work out what the ECT/IAT bias stuff should be...

[5_Liter_Eater]

Tiffer,

Can you explain what it is you actually did? So you did created the custom PID for GMVE in Bluecat's post #16 and plotted it against the VE table and cut and paste those numbers directly into the VE table in the tune or you compared the % error from bluecat's PID against the MAF airflow and pasted the % error into the VE?

[Tiffer]

Hi 5 Liter Eater,
I created the Bluecat's GMVE PID and logged it in a VE histo as in the picture. I then pasted the histo values into the tune (i.e. replaced the existing values). This looks a bit scary because the cells you don't hit are 0's. I then interpolated horizontally across the zero's in each rev range, and estimated the missing corner values etc.
The table i ended up with had GMVE values of around 300 higher in the low revs, 150 higher mid revs, and 400 lower high revs as compared to stock.
So you are basically creating a new table from scratch - no % error stuff.
Give it a try and let us know.
Tiffer

[redhardsupra]

i'm still not sure why you're calculating GMVE if you can just scan for the PID (on some platforms, E40 should be good to go tho)

[Tiffer]

I am not sure of how it works - I would have assumed the GMVE PID would be the value in the tune's VE table?

[EC_Tune]

Easiest way is to calculate it for one histogram and use the PID for another then copy them to excel or to an HPT VE table to see the differences.

[Bluecat]

If the GMVE pid reflects the MAF calc while in MAF mode, its a simple as building a histogram of the GMVE pid. If it dosen't, then it's still as simple as deriving the ve numbers from CAM, MAT, and MAP while in MAF mode. GMVE = MAT / MAP * CAM * 1000. So the PID formula would be:

GMVE = [PID.2126.MET] / [SENS.30.MET] * [PID.2321.MET] * 1000

Like I said in post 16, I'm not 100% sure about what the GMVE pid is generated from. I thought I had seen screwy stuff in the past, but in the last car I did and payed attention to, the pid seemed to be relative to what the computer was doing at the time. So, yeah you could probally just log the pid and not do the formula.

I guess you could blow in a screwed up VE table, log the formula and the pid while in MAF mode and compare the two. If they match then we don't need the formula.

[Bluecat]

Easiest way is to calculate it for one histogram and use the PID for another then copy them to excel or to an HPT VE table to see the differences.

What he said...

I should have hit post instead of re-reading it 5 times and you wouldn't have beat me to it.

[ktoonsez]

Here is some additional information on the formula from post #16: (This was done on my LS3, has a very nice VE table but MAF table is off and causes the car to log misfires at idle when I enabled MAF.)

Using the formula from post #16 I did some logging to see if the formula matches up to the GMVE PID and it does when I have the car running VE ON and MAF OFF.

If I turn OFF VE and turn MAF ON the formula PID is almost 200 higher than the value of GMVE PID.

If I turn ON VE and MAF together the formula PID gets a little closer to matching GMVE but not exact (somewhere between 1-7%).

So you can see that the GMVE value does get altered depending on your current "Air calc mode".

I am still trying to get it straight in my head which way the MAF table needs to go to make these match (add or subtract).

[redhardsupra]

if you want your GMVE-based airmass to match your MAF-based airmass, why not first calculate airmass from the MAF, and then use it to generate GMVE values? now that'd be a much better use for it, assuming of course that MAF has been properly calibrated.

[ktoonsez]

if you want your GMVE-based airmass to match your MAF-based airmass, why not first calculate airmass from the MAF, and then use it to generate GMVE values? now that'd be a much better use for it, assuming of course that MAF has been properly calibrated.

That is the problem VE table is GOOD and MAF is BAD, don't have a WB at this time and want to try to find a nice way to tune MAF without WB till I can tune with it again, just trying to help myself and others that don't have a WB.

[redhardsupra]

ok, then go in reverse: calculate airmass from GMVE, use it to calculate MAFflow have you seen this yet: http://redhardsupra.blogspot.com/200...ss-models.html i talk about how they're all equivalent and how to transform one into another

[ktoonsez]

Thanks I will read it and see if helps my add/subtract problem.

[ktoonsez]

No luck, MAF is never going to work with my setup I guess, I think the MAF table itself has to big of a spread between each column (150 Hz). The biggest problem is down low and there is just no making it happy, wish I could take MAF out of the equation below 3150 Hz.

[Harlech]

Good reading info here. Love watching the masters brain storm.

[rian_human]

Hi 5 Liter Eater,
I created the Bluecat's GMVE PID and logged it in a VE histo as in the picture. I then pasted the histo values into the tune (i.e. replaced the existing values). This looks a bit scary because the cells you don't hit are 0's. I then interpolated horizontally across the zero's in each rev range, and estimated the missing corner values etc.
The table i ended up with had GMVE values of around 300 higher in the low revs, 150 higher mid revs, and 400 lower high revs as compared to stock.
So you are basically creating a new table from scratch - no % error stuff.
Give it a try and let us know.
Tiffer

Hi there,

I tried this and all I get is unsupported parameters. I have an 05 LS2 GTO.
Could you post your config?

On a side note; How's SA? Grew up in Johannesburg. Moved to the US in 04, but I miss SA....

[Tiffer]

Hi Rian,
I have posted the config - histo 9 is what you are after. SA is all good if you avoid reading the news - at least you can still get away with not having plates! Wouldn't mind living in the US tho...
Tiffer

[DSteck]

Just as an FYI... this is the first time I checked out this thread. I had remembered reading RHS's speed density stuff, and based on that, I used the dynamic cylinder air mass from my scanner to calculate a GMVE table. I run MAF only right now on a big cam, ported heads LS7 because the VE table just didn't work and was causing bad lean spots at 4k rpm on the dynamic to high speed switchover.

Since I am running MAF only (and it's dialed in pretty spot on), the reason I used dynamic cylinder air is because it uses the filtered MAF value instead of the raw MAF value to calculate, and is generally more stable (and ultimately it's what the car runs off of from what I understand).

I took that dynamic cylinder airmass value, along with MAT and MAP values, and used them to create a PID. I don't have my laptop with me right now, so I don't know the sensor numbers, but it looked like:

1000 * MAT * DCA / MAP = GMVE

I used that PID of MAF-calculated GMVE to build a histogram, and logged drivability stuff for about 25 minutes. I didn't do WOT sections because my MAF HIGH table is still out from the head swap, and I haven't had a chance to redo that. Anyway, using this table that had the LS2 VE axis labels, I massaged a table together, got the coefficients, threw it in... and it actually worked pretty well for drivability. The airflow values for GMVE and MAF weren't totally different from each other (which is expected), and it seemed to give a good starting point for a VE table.

I'm not saying this is a way to perfectly set up your VE table, but it's a damn good starting point for E38 vehicles since trying to set up SD for a radical change (ie: big cam) is such a pain in the ass. Anybody trying to at least get a baseline for their VE table can use this. However, you will still have to make sure your bias for MAT is correct (I did mine based off of the stock bias table).

I haven't given it much thought, but maybe it's possible to use the MAF to help develop the bias table as well, assuming you had some way to always hold your coolant and intake temps constant. Somebody else with more time/dedication can try to figure out if that's possible, though.

That said, I'm still MAF only until I can completely finish the MAF HIGH table.

[rian_human]

ok, then go in reverse: calculate airmass from GMVE, use it to calculate MAFflow have you seen this yet: http://redhardsupra.blogspot.com/200...ss-models.html i talk about how they're all equivalent and how to transform one into another

Bringing back an old thread...

A little background. I was running with a MAF, commanding 12.9 AFR, and actual was a very flat 12.9. I switched to a Vararam, with no other changes, and actual fluctuated from 11.1 to 11.9 and the MAF Hz would jump up and down, giving readings like 379,415,394,431,387,406 g/sec in the 6300 to 6700 r/min range. I am ditching the MAF, but since it was 'calibrated' I want to use the original flow numbers to come up with a base GMVE

I read this blog and got this calculation:
GMVE= IFR*IPW*AFRwb*(IAT+(ECT-IAT)*BIAS)/MAP

Where can I find the BIAS, or is there another way to go from g/sec to gmve that I missed somewhere?