Corpsvette

I would post this at HPtuner except they are talking all different kinds of cars. Is it possible to tune a Corvette to the point of getting rid of the MAF altogether. I thought the MAF was the brains to air and fuel formulas for our cars. Just wondering if any Vette guru's have done this.

Thanks,

Jim K.

SideStep

I am doing it right now. I just got my VE table "dialed" and I had planned on completely reconnecting the MAF and try to calibrate my MAF Calibration table to agree with my new (and correct) VE table. Some (and I may do it myself) just leave the MAF unhooked and go with a permanent Speed Density (SD) system....

Disconnect just the MAF signal wires. Leave the IAT wires connected. This will cause the PCM failover to Speed Density (SD) mode. This causes the PCM to read from the VE table (obviously no MAF). you can then log your LTFTs and make adjustments to the VE table to get close to zero. After you have the VE table dialed in reconnect the MAF, this will cause the LTFTs to go high or low again. At this point adjust the MAF Calibration table to get the LTFTs back to where they were just after you dialed in the VE table... WOOF, after all that you should have a correct VE table and an accurate MAF. In short you want to tune your VE table without the MAF, then reconnect the MAF and adjust the MAF table values to get it to agree (according to the LTFTs) with the VE only LTFTs.

FYI, you will need to disconnect pins C, D, and E. Pin A and B are your IAT sensor. See picture below, provided by Patches....

Corpsvette

Hey Sidestep,

Thanks for the awesome scoop. I am still waiting for my HPtuner. Waiting for the WB integration before they ship. That is the information I was looking for. Thanks a bunch. I may be hitting you up for more info when I get kicking on this thing. Take care.

Jim Kay

T_Vert

sidestep, do you mind if I see your VE tables? I had my VE tables pretty close to 0s but when I plugged in the MAF Ltrims went back positive in some spots. And i was getting positive Ltrims at WOT so i went back to my IFR tune. Id like to compare our VE tables

our mods are almost identical but i have dynatech headers/cats.

Thanks
dave

SideStep

Dave,

After you have your (MAFless) VE table dialed AND plug your MAF back up your LTFTs will go postive....

THEN

You have to scale your MAF Calibation table (positive) to get your LTFTs back to where they were when it was MAFless.

The point here, and you may already know this, is to get an accurate VE table and then adjust your MAF (Calibration table) to agree with VE when you are observing your LTFTs...

Download this spread sheet:
MAF Calibration
Go to the "MAF Calibration Fix" tab, it is pretty self explanatory. You will need to LOG your MAF Frequencies vs. LTFTs (take the average of both sides). Once you have a large log (varied driving conditions) sort on MAF frequency, lowest to highest. Take the sorted LTFT numbers and paste them into the relevant columns on the spread-sheet. You will see the averaged LTFTs at the top of the column for that specific frequency range. This number is a perctage of how much to scale that particular cell in the MAF Calibration table on HPTuner... GOOD LORD that was a mouth full...

Let me know if you need any help...

T_Vert

thanks, unfortunately its a bit late in the season for me to be dealing w/ this so ill just have to sit on it over winter

Dave

thetorch

Sidestep, Any chance you can send me the spreadsheet you had linked here or tell me how you did the MAF Scaling? Thanks!

gojo

Here are some necessary procedures.


1: Unplug and replace MAF with a strait bellows (less airflow dispruption creates a better VE)

2: Disable MAF codes (No check engine light)

3: Change all points from 122* and greater to 1.13 in the Open Loop F/A vs ECT vs MAP table (commands AFR of 13.0)

4: Change all points in the Closed Loop Enable Coolant Temp vs IAT table to 250* (Disables closed loop)

5: Copy High Octane table to the Low Octane Table (computer reverts to low octane table when MAF is unplugged, this assure optimal timing)

6: Change all points in the Power Enrich Fuel Multiplier vs RPM table to 1.0 (disables PE mode)

7: Use wideband to verify AFR of 13.0

8: Make adjustments to the VE table accordingly to dial in a 13.0 AFR (a lot of driving or dyno time)

9: Hand smooth VE as described by Magnus (a smooth VE results in crisper throttle response)

10: Change all points in Open Loop F/A vs ECT vs MAP table back to stock (re-enable stoich commanded AFR)

11: Change all points in the Closed Loop Enable Coolant Temp vs IAT table back to stock (re-enables closed loop operation and fuel trim learning)

12: Change all points in the Power Enrich Fuel Mulitiplier vs RPM table back to stock (re-enables PE mode)

13: Use wideband and PE table to dial in desired WOT AFR. (optimum HP at WOT)

FreddyG

I'm pretty new to this stuff, so could someone please tell me what is the difference between using the MAF and using Speed density, other than one uses a MAF sesnsor and one doesn't? What are the benefits of goig to the SD set-up?

Thanks

Z06GMAN

BOOST as in 3 bar MAP

H82BFST

SideStep - You talk about changing MAF calibration table. What about the fact that the MAF table is a MEASURED airflow table for the frequency output of the MAF device. Meaning that, at 4750hz it flows 201.1437 lbs/hr of air through the C5 intake track setup & MAF. It would be like taking any finely CALIBRATED instrument and miscalibrating it on purpose just to fit your needs. The more you do this, the more you end up chasing your tail in the long run. Garbage in, garbage out.

Why are you guys so obsessed with nailing ltrims at 0 for everything? You do realize that strims and ltrims are a CORRECTION factor right?

Hint: Your ltrims don't all have to be 0 everywhere to not have fuel correction at WOT if so desired. Contrary to popular net belief, the GM boys do know what they are doing.

Just my .02 worth

SideStep

I think you need to take a trip over to http://www.hptuners.com/forum/YaBB.pl

It never it never ceases to amaze me, those who have never done "it" have the most to say about it....

Hint: It is a good thing you are here to save us from our ignorant non-tuning selves... just my 2 cents...

gojo's instructions in the above post are dead on......

H82BFST

Right how stupid of me. I forget sometimes that engine tuning was just invented when the LS1 was born and when HPTuners came on the scene.

You can rig almost anything to work one way or another. How long will it work or what's really going on are another question. Hell I know guys that spray 200+ on a stock block... it also works!!!

Enjoy your fun guys. It shall be fun reading threads in the future about the issues. BTW, I have some swamp land in Florida for sale.... ahh, nevermind.

tici

Who knows how to scan for VE's with an A4 98 Trans Am? It should be same as for the 97 Vette.
The problem is that disconnecting the MAF the A4 will work full pressure all the time (shifting like hell).
I know that HP tuners can fix this, but I'd like to use my Edit.
Who knows the solution? Is it that bad to drive around logging the VE's at full tranny pressure?

FreddyG

I understand what a 3 Bar MAP sensor is and what it does, but this doesn't explain why SD is better than MAF for our cars. What confuses me is that the Mustang guys are switching to MAF, and here we're going to SD, and I'd just like to know what the advantages and disadvantages are. Thanks

gojo

Sidestep, I'm with you. I've had the same experience. Notice that there are only critiques and general insults. Nothing constructive.


tici, you might try zeroing the MAF fail. If you select SAE MAF you can still log everything. It's not as precise as SD, but It's really not necessary to be totally precise.

tici

gojo, you mean to zero the High MAF Fail MHz?
Could you please explain SAE MAF?

I still don't know if it's better to drive SD, but I would like to first adjust the VE, tune the MAF and then see the difference.

ToplessTexan

Probably more annoying than anything else. Recall that the PCM typically commands max line pressure (maybe disabling TCC lockup) when tranny DTCs start popping. Given that, it wouldn't seem particularly unsafe to me.

gojo

[QUOTE]=tici]gojo, you mean to zero the High MAF Fail MHz?

tici

Thanks! This is one of the best explanations I got without the usual blabla.