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Can I run a 2-bar MAP and keep my MAF?

 
Old 10-28-2015, 06:13 PM
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TastyBacon
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Default Can I run a 2-bar MAP and keep my MAF?

I'm planning a mild turbo build over the winter and am thinking about how I'll tune it. I have an L33 and am planning on making 450-500whp for a fun street car that won't see the track. Yes, I know there are cheaper/easier ways to make that amount of power, but I like turbos.

All the turbo LS guys I know use HP Tuners and tune speed density, MAP only. But they also all make 800+ HP. I'd like to keep my MAF if possible. At my power level, I may not even max out an 85mm MAF. If I do, I can switch to a card MAF. The problem is that everything I read says that you need the HP Tuners 2-bar OS to use a 2-bar MAP, and if you do that, you are stuck with speed density only and can't use a MAF. I've also read that you can use a MAF with EFI Live COS, but haven't found anybody who is actually doing it.

So, is anyone here actually running a MAF tune and can set me straight? Thanks.
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Old 10-28-2015, 06:37 PM
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Originally Posted by TastyBacon View Post
I'm planning a mild turbo build over the winter and am thinking about how I'll tune it. I have an L33 and am planning on making 450-500whp for a fun street car that won't see the track. Yes, I know there are cheaper/easier ways to make that amount of power, but I like turbos.

All the turbo LS guys I know use HP Tuners and tune speed density, MAP only. But they also all make 800+ HP. I'd like to keep my MAF if possible. At my power level, I may not even max out an 85mm MAF. If I do, I can switch to a card MAF. The problem is that everything I read says that you need the HP Tuners 2-bar OS to use a 2-bar MAP, and if you do that, you are stuck with speed density only and can't use a MAF. I've also read that you can use a MAF with EFI Live COS, but haven't found anybody who is actually doing it.

So, is anyone here actually running a MAF tune and can set me straight? Thanks.
You can use a MAF with HP Tuners 2-bar OS too. Whomever told you that you can't is mistaken.
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Old 10-28-2015, 06:44 PM
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Yes. The 2 bar OS does NOT have to run SD only. You are NOT stuck with SD if you use their 2 bar OS. I'll have to check, but I also doubt you have to upgrade OS's to use a 2 bar MAP sensor if you're still running MAF only.

The 2 bar OS from HPT can run MAF only, SD, or mixed.

Why not just run SD? I'm not sure why people think it's only for 800+rwhp type builds.
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Old 10-29-2015, 12:57 PM
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Thanks for the input, guys. I got the info that the HPT 2-bar OS is speed density only from their website: http://www.hptuners.com/products/vcmsuite_enhance.php

schpenxel, by not needing to upgrade the OS to use the 2-bar MAP, do you mean just scaling the VE table?

I'd really like to use the 2-bar OS, because it has some nice enhancements for turbo cars, like the MAP-referenced boost enrichment table. Maybe I should just do that, go speed density, and see how I like it. My motivation for keeping the MAF is that MAF cars have a better reputation for street driveability, and I plan to continue putting a lot of street miles on the car.
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Old 10-29-2015, 01:18 PM
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I'm 99% sure they just put that on there because they haven't actually gone through and thoroughly tested it in MAF only. The E40 OS (which is what I'm running) says the same thing and I'm 100% sure it can run MAF only because I've done it. I could be wrong.. but I don't think I am. I found some posts by the owner of HPT that basically said it should work fine but they haven't tested it like that

You can run the 2 bar OS, in MAF only and still get the boost enrich features, etc. without being in SD mode. Even though it's called a "2 bar" OS, you don't have to use speed density at all.

I've found the exact opposite honestly in regards to which is smoother. SD cars that I've seen tend to drive smoother than MAF equivalents (all other things being equal). SD is popular on cars that do idle pretty rough, big cams, etc. due to turbulence and reversion, both of which can wreak havoc on the MAF. They don't run rougher because of SD; they run SD tunes because of the nature of the beast.. MAF tunes would be even worse on the same cars.

It's not unusual for the MAF signal to be a bit unstable given all the turbulence created by a supercharger, bypass valve, intercooler, etc. This can make them surge and have all kinds of unsmooth characteristics that no one likes. SD doesn't have that problem since it doesn't care about turbulence... thus the reason it tends to be smoother.

Unreal over in the C6 section swore his MAF only car drove just fine and SD wouldn't be any smoother.. but after he switched to SD he said it's quite a bit smoother and he was wrong.

Scaling the VE table in the standard OS wouldn't really fix the problem of it not going beyond ~100kpa, which is the major issue the 2 bar OS addresses.

My opinion? Upgrade to the 2 bar OS. It's free, you gain some cool new features, and you don't lose anything, so why not. You can then run MAF only, SD/VE only, or mixed mode. It's up to you. It should be fully capable of running MAF only just like the stock OS if you want

Worst case.. switch back to the stock OS. It's not a permanent upgrade that can't be undone

Last edited by schpenxel; 10-29-2015 at 03:06 PM.
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Old 10-29-2015, 02:48 PM
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Originally Posted by TastyBacon View Post
Thanks for the input, guys. I got the info that the HPT 2-bar OS is speed density only from their website: http://www.hptuners.com/products/vcmsuite_enhance.php

schpenxel, by not needing to upgrade the OS to use the 2-bar MAP, do you mean just scaling the VE table?

I'd really like to use the 2-bar OS, because it has some nice enhancements for turbo cars, like the MAP-referenced boost enrichment table. Maybe I should just do that, go speed density, and see how I like it. My motivation for keeping the MAF is that MAF cars have a better reputation for street driveability, and I plan to continue putting a lot of street miles on the car.

Anyone that had a bad experience from a 2-bar OS is going to tell you it sucks, but it's only going to be as good as the calibration and there seem to be far more people out there that have a difficult time with SD and therefore swear by MAF tunes. I mostly tune F/I SD. Even C6's and people always ask me why when the C6 MAF has so much higher airflow capability than the C5, which is what caused many to go SD in the first place. Much of my tuning work is retuning cars that were already tuned and they're always MAF. I've never had a customer say their car didn't leave my hands in better running condition.

I don't care what HPT says on their website. It's far too easy to prove them wrong. Plug in your MAF, enable it and see what we're saying for yourself.
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Last edited by [email protected] Performance; 10-29-2015 at 02:49 PM.
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Old 10-29-2015, 04:39 PM
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Thanks a lot guys. I'll plan on starting with the 2-bar OS and see how good I can get it running SD. I'll post a build thread eventually, but it's nice to have this question answered. One more thing checked off the list...
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Old 10-31-2015, 10:31 AM
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Some very good advice here. Mine was much improved after putting on the supercharger and going SD over the old MAF setup. The tuner worked and worked on the MAF tune to get it as good as he could but when we switched to SD, the idle and performance is mucho better. GL with your setup.
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Old 10-31-2015, 05:30 PM
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when i got rid of the maf on a stock ls1, the car ran like before and emissions were cleaner. without maf you have one thing less to worry about. reading on here and efilive it seems like a major headache to get that table right.
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Old 10-31-2015, 05:48 PM
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Not a matter of getting the MAF tables right, it's a matter of getting turbulence down to a point that it can even get a consistent/smooth reading
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Old 10-31-2015, 08:56 PM
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My car runs so much smoother SD than when I was trying to keep the MAF.
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