Speed Density Air Calc Mode Patch and SD Tunes and Torque Based Functionality

[cmitchell17]

So I've been around HP Tuners with GM stuff for 15 years, but I've never actually done anything with anything GEN IV, only GEN III and GEN V. I've also never really done much with forced induction until now and I am finding out some limitations and things I screwed up and trying to read through all kinds of old threads and try to re-remember the stuff I used to know.

I've got a 2011 Sierra Denali I am putting a turbo on, and I got a 3-bar MAP (12592525), but I guess there is a 2.5 bar limit on custom OS's on E38s so I guess I can't go that route. That is ok since I can use VVE (I think?) and just scale the VVE editor to whatever limits I want and re-calc coefficients. The other thing is I can't find a custom 2/3 bar OS to use after searching everywhere on the forums. The only ones I found were for Camaros and other cars and not for trucks. I know we are not supposed to be full flashing OS's unless its something similar. I know with GEN III stuff I used to flash all kinds of different random OS's to see what would happen and hoping they may have "enhanced" functionality.

With that said I would love to go MAF, but it seems like MAF is the enemy of people especially with turbos, and they have to kill it at all costs. I feel like MAF is good and will help me report accurate airmass/flow for torque based dependent operations like transmission and traction control. My problem is I can't find the proper hoses and tubes to fit my MAF, even though I could go to one of those aftermarket ones, but that's a different story.

So I am assuming HPT has changed something with their custom OS's because this "Speed Density Air Mode Patch" isn't in the documentation, and all the relevant HPT Forums posts that have the relevant info I need on all these questions have been deleted for whatever reason, but they still come up in search engines.

Also if the documentation said only up to 2.5 bar MAPs are supported, I guess I can't use this supposed 3 bar MAP at all? I was thinking all the MAPs they make were calibrated to max out at their pressure limit at the same voltage, so why does the electronics/software care?

Also my current stock truck OS is 12639835. Thanks for the help.

[5FDP]

You can run the 3 bar map on the 2 bar OS upgrade, that has never been a problem.

Run the OS upgrade if you want, I see no problems here if ditching the MAF is what you want. Do you really think you are going to be pushing 20psi of boost?

That would be some pretty crazy horsepower numbers, enough to completely grenade the 6L80e and the hurt the driveline. I bet a 6.2 with 10psi makes an easy 600 horsepower.

[cmitchell17]

You can run the 3 bar map on the 2 bar OS upgrade, that has never been a problem.

Run the OS upgrade if you want, I see no problems here if ditching the MAF is what you want. Do you really think you are going to be pushing 20psi of boost?

That would be some pretty crazy horsepower numbers, enough to completely grenade the 6L80e and the hurt the driveline. I bet a 6.2 with 10psi makes an easy 600 horsepower.

Well not yet.. haha, but yes I have a 7 psi spring in the wastegate now.

So I guess I interpreted it wrong, it made since to me as long as the MAP was scaled with the right linear constant and offset in the calibration, everything is good, so good to know.

So I actually want to run a MAF, what I was saying was that it seems like everyone loves to ditch MAFs but I feel like with a MAF you should get better driveability, which yeah I'm about the only one that cares about that... I do realize I will hit a limit early on with my MAF though, I can't find a exact number but I would probably think that I would be around it at the 7 psi number.

And I wasn't really thinking at the time and just got the 3-bar, but 20 psi would be nice haha.

Also as a side note does anyone know where I can get a proper MAF tube so I could make sure its after the intercooler? I was going to get the cheap Chinese spectre one, but I can't confirm 100% it will work based on the feedback, and I can't find any other vendors that make one for that specific MAF.

[GHuggins]

The problems with a MAF on a turbo setup start to outweigh just running SD. In fact manufacturers even got away from running MAF's with turbo's for some of the same reasons.

If your running a large turbo it isn't "as bad" and you can almost make it work, but if running smaller duels it's especially noticeable. Basically what your going to find is that you have to run a blow-through setup. You can run pre-turbo like the smaller 4cyl's did, but then your going to have fueling issues during blow-off valve events. Your also going to run into dfco issues at the same time as it's still going to see the high airflow when it should be dropping. Try to tune for one then your going to have issues elsewhere. SO then the option goes to blow-through. Couple of problems here - has to seal for boost and then your going to experience weird engine cut issues when coming to stops where your blow-off and bypass's open. Your going to have to fine tune your blow-off to make it work. But basically your engine will just shut off with particular OS's both with light throttle and coming to stops. You would think that since a centri uses the same setup that it should work just the same, but it never does

VVE is the way I would go but the ecm can loose processing power for the equations anywhere above 3000rpms. If you notice the OE won't even bother fully tuning above that rpm point. This is where the custom systems come in, but I've never personally liked anything about them other than the PE settings for boost.

If your able to make the MAF work without the "side effects" then please let us know.

[cmitchell17]

The problems with a MAF on a turbo setup start to outweigh just running SD. In fact manufacturers even got away from running MAF's with turbo's for some of the same reasons.

If your running a large turbo it isn't "as bad" and you can almost make it work, but if running smaller duels it's especially noticeable. Basically what your going to find is that you have to run a blow-through setup. You can run pre-turbo like the smaller 4cyl's did, but then your going to have fueling issues during blow-off valve events. Your also going to run into dfco issues at the same time as it's still going to see the high airflow when it should be dropping. Try to tune for one then your going to have issues elsewhere. SO then the option goes to blow-through. Couple of problems here - has to seal for boost and then your going to experience weird engine cut issues when coming to stops where your blow-off and bypass's open. Your going to have to fine tune your blow-off to make it work. But basically your engine will just shut off with particular OS's both with light throttle and coming to stops. You would think that since a centri uses the same setup that it should work just the same, but it never does

VVE is the way I would go but the ecm can loose processing power for the equations anywhere above 3000rpms. If you notice the OE won't even bother fully tuning above that rpm point. This is where the custom systems come in, but I've never personally liked anything about them other than the PE settings for boost.

If your able to make the MAF work without the "side effects" then please let us know.

Thanks everyone for the help.

And I do see pictures and stuff of MAF's in line after the intercooler going to the throttle body, but then I guess it's probably people just putting the whole MAF assembly in there just to have IAT since they don't want to pull the wires out of it and/or buy another IAT sensor.

As for the lean condition during BOV actuation, couldn't you route the blow-off air back to the intake? I guess you would still have some transient behavior you would have to tune for but eventually you would account for your metered air?

I've always never understood how transient air being metered by the MAF could have a noticeable effect, it seems like the air is going so fast through the motor no human could even perceive any problems.

I guess I wouldn't care so much about running a MAF if it weren't for the inaccuracies especially with in accurate torque model, but maybe my concerns aren't warranted? Can you achieve just of good of airmass based torque estimation and fueling with SD as you can with MAF+SD? I would think you couldn't with the sloppily way GM programs the VE tables, but maybe you could if you spent a lot of time and effort on the VE/VVE table? You also have the inherent error in the VVE table from trying to satisfy equations, and I also think you have a large amount (more than most people think about) of error in reading feedback from a wideband O2 that reads excess oxygen from a up stream imperfect and inconsistent combustion event to determine airmass, but that's a whole different topic.

[Ben Charles]

This setup can be done in MAF no problem, just don’t have any crazy bend pre or post sensor (I actually like using a screen on larger tubes) but that OS had a huge G/sec limit and 15k hz limit.. I would run a 3” card style MAF tube and tune away. Keep the BOV before the MAF and not right beside it or post MAF

[cmitchell17]

This setup can be done in MAF no problem, just don’t have any crazy bend pre or post sensor (I actually like using a screen on larger tubes) but that OS had a huge G/sec limit and 15k hz limit.. I would run a 3” card style MAF tube and tune away. Keep the BOV before the MAF and not right beside it or post MAF

Thanks, it looks like the software hard coded limit is 31,746.6 lb/hr, which I guess doesn't really matter? Default its scaled up to 15,000 Hz.

So I see the big deal now, MAF tables aren't scalable, I tried to right click and there is no option to edit the axis. So is this why we see people running into hard limits on the MAF? And if so does this explain why no one runs an aftermarket MAF's? Since running an aftermarket one won't do you any good any way since we can't re scale it? Or am I missing something here?


Also on a kind of related note. Is it completely out of the question to try to integrate the OEM supercharger/turbo strategy built into the E38? So it appears, at least from what I can see using HPT, that there are only options for superchargers in my E38 tune file. I have tried to mess with these things before, on GEN V stuff as well, and they seem to just not do anything or respond to input. Anyone think one day we would get there? Maybe it wouldn't really do you any good, but it seems like it would be really nice to have a factory supported forced induction mode and it would seem like it would help preserve stock functions and good drivability.

[ttz06vette]

Not that this helps you now, but a company named Abaco used to make a fully programmable MAF. Basically it came with software and you can configure your MAF curve and scale any way you choose. It created a transfer function for the OS. After trying many MAF setups it is the only thing that worked for me. So I use a combo of VVE and MAF where I let VVE control the majority of the tune up through 2100 RPM. This helps with idle and low speed smoothness. My DFCO is turned off.

[cmitchell17]

Not that this helps you now, but a company named Abaco used to make a fully programmable MAF. Basically it came with software and you can configure your MAF curve and scale any way you choose. It created a transfer function for the OS. After trying many MAF setups it is the only thing that worked for me. So I use a combo of VVE and MAF where I let VVE control the majority of the tune up through 2100 RPM. This helps with idle and low speed smoothness. My DFCO is turned off.

Thanks, until I get everything else set up and running correctly, I think I could get away somewhat with the stock MAF flow, but I think first thing is going to be injectors. I was hoping I would get more out of L9H flex fuel injectors and pump, but looks like I am getting into the 70/80% DC area.

It's surprising to me just how much the IAT makes a difference in how it runs. Right now I don't have the IAT sensor decoupled from the MAF so I'm running not IAT sensor and I assume its defaulting to 68F, it still idles but its pretty rough and runs down the road at light throttle very rough as well, it feels almost exactly like its got a misfire even though its showing perfect zero counts on all cylinders. Everything else about the engine is bone stock.

My other question that I haven't seen anyone else talk about is how much having the O2's after the turbo effects them? I guess it doesn't? I do have one available bung on my turbo manifold on the passenger side but I plugged it and installed the right bank O2 in the downpipe so it's farther back than stock, which I know could effect integral delay like with long tube headers, but I am talking more about the combustion process, especially as the exhaust moves through the turbine I would think the combustion process could be driven more to completion by the time it gets to the downpipe? O2 feedback has always been one of those things I question on accuracy just due to how unstable the combustion process is and that you are relying on a measure of how much left over oxygen you have, it just seems really un stable and un predictable.

[cmitchell17]

This setup can be done in MAF no problem, just don’t have any crazy bend pre or post sensor (I actually like using a screen on larger tubes) but that OS had a huge G/sec limit and 15k hz limit.. I would run a 3” card style MAF tube and tune away. Keep the BOV before the MAF and not right beside it or post MAF

I guess before I spend 100+ to go to a card style MAF (I am assuming the "card" style is a LS3/LS7/LS9?/GEN V LT1? style MAF) I should try SD first and see how it works out. Especially since I already have a MAF breakout wiring harness and a aluminum bung and IAT sensor. I am trying to do everything where I can go back to "perfect" stock.

[HawkZ28]

I know I'm late to the soiree, but for the MAF tube on my D1SC, I repurposed the K&N CAI and OEM MAF sensor that was already on the truck by removing the air filter/box and replacing it with a 3" to 3.5" 90* coupler. I also run a 5:1 (upgrading to 8:1) airflow straightener from SaxonPC, a member on here, pressed up against the MAF. I've found that the larger the tube, the more erratic and unstable the Hz signal is- removed mine for testing and measurements and without the honeycomb my signal bounced across 6-8 cells while cruising, vs 2-3 with the honeycomb loaded in the tube. Without, throttle feels mushy, and your MPG look like you spend all day in boost.

Just installed an 8:1 101mm on my wife's 4" CAI on her Escalade and Hz is crazy steady and smooth.