EFI University

Techsalvager · Joined: 21 Jun 2011 Posts: 140

I have a megasquirt currently running on a speed density setup, map based. I am trying to incoprate a MAF into the system and currently have a KA24DE ( 95+ ) MAF wired into the system. Currently its placed before the turbo inlet but angled and I believe this angle is causing readings to be off. How much space should I give the maf before the turbo and how long of a straight pipe should be infront of it before the maf?

Thanks

Justin

hezsmurf · Joined: 17 Nov 2005 Posts: 101 Location: The Netherlands

I would not change the system and keep the map, but that may be a personal preference. Why change to maf, if I may ask?

I would put the maf behind the turbo, just in front of the throttle.
Now you're also measuring air that escapes in the waste gate control or the blow-off valve when you release the throttle. So, mixtures can be a little too rich to a whole lot to rich which cause big flames from the exhaust.

skylinegtrhr · Joined: 14 Oct 2009 Posts: 30 Location: Croatia

On OEM Nissan ECU You need bend between turbo and AFM or You get reverse flow reading when You lift the throttle , I don't know how MS behave ... But as hezsmurf suggest blow trough is always better option just adopt VQ map to new position and be ready to regularly clean AFM or it will be giving You false readings.
_________________
http://www.nistune.nissan-club.hr/

StantonWarrior · Joined: 10 Dec 2010 Posts: 188 Location: UK

Stick with MAP based speed density...

Techsalvager · Joined: 21 Jun 2011 Posts: 140

changing because I feel like the maf would be a better system in terms of telling actual airflow thats being ingested compared to computing it with map based.

skylinegtrhr is there a place with these VQ maps that I can check out?

skylinegtrhr · Joined: 14 Oct 2009 Posts: 30 Location: Croatia

I have them in NIStune software pack if You PM me Yours email I can send them to You .
_________________
http://www.nistune.nissan-club.hr/

Techsalvager · Joined: 21 Jun 2011 Posts: 140

Techsalvager · Joined: 21 Jun 2011 Posts: 140

stevieturbo · Joined: 29 Aug 2006 Posts: 846 Location: Northern Ireland

Techsalvager · Joined: 21 Jun 2011 Posts: 140

Flr Power · Joined: 05 Jun 2007 Posts: 100

IMO there is no need to use a MAF. MAP works great on race or street car and has great driveabilty once properly tune. It is also more reliable, from experiance, and cheaper. There is no need to complicate things like the car industry has been doing for so many years, often not really improving things for the better.

Grocerius Maximus · Joined: 02 Apr 2006 Posts: 171 Location: McKinney TX USA

There is usually too much swirl and/or turbulence present in IC pipes to make most MAF's work right, calibration gets thrown way off depending on gas velocity and pipe configuration. They REQUIRE laminar flow on the upstream side, downstream only needs 2-3 pipe diameters until a disturbance won't effect it much. So turbo inlet is the ideal spot. There are no blow-thru MAF setups in the OEM world, and there's a reason for it- you need 8 to 16 diameters of straight pipe PLUS a (mostly patented) flow mixer/flow straightener element.

Why do OEM's use MAF's? 'Why' can pretty much always be answered by 'cost'. If you know the exact characteristics of the MAF and injectors, there is very little calibration time needed, and most of that is for things other than fueling.

Techsalvager · Joined: 21 Jun 2011 Posts: 140

Roberto Arano · Joined: 22 Nov 2005 Posts: 364 Location: colorado

quote "What do you mean pipe diameters is that some type of formula? "

it's a rule of thumb, it takes some length for the airflow to become "organized/predictable", the length it takes is related to the diameter of the pipe l/d ratio
_________________
www.circuitse7en.net
http://stores.ebay.com/Circuit-Se7en

stevieturbo · Joined: 29 Aug 2006 Posts: 846 Location: Northern Ireland

Techsalvager · Joined: 21 Jun 2011 Posts: 140

I was planning to eventually add 4 EGTs in the end, though 4 o2 sensor would take a lot more cash and I would be worried about their lifespan in the cast iron turbo exhaust manifold.

I have a J&S for knock running in the car.

Techsalvager · Joined: 21 Jun 2011 Posts: 140

Back to this, anyone ever seen a maf setup after the TB any reason this may or may not work?

RootesRacer · Joined: 04 Apr 2005 Posts: 461 Location: Arvada, Colorado

Tomak · Posted: Mon Nov 21, 2011 8:39 pm Post subject:

As has been said, to use a MAF, you need smooth airflow. Also, if its before the turbo, what are you gonna do when the blow off valve vents what was metered air? If it's too close to the impeller, you will get a "noisy" signal as well.

If it "blow through", what are you gonna do with the oil that will eventually cause it to read lean?

Most factory MAF car that run turbo are draw through with recirculating or no blow off valve.

Also, to get a clean blow through signal, I have found you need a minimum of 3 straight pipe diameters before the maf, and 2 straight after.

I am not sure how MS handles a MAF.

Factory MAF cars convert the MAF voltage(or frequency) to a mass flow, and then to a "load", your target AF ratio is then load based (and most often so is your timing), but the fueling calcs are based on air mass, and work well IF you have an accurate MAF transfer curve. Again, not sure how Megasquirt handles this, and if you retain the benefit of the MAF with this system.

Remember, the factory uses a million dollar flow bench, and flows the whole inlet tract when mapping the MAF trasnfer curve.
_________________
www.Dynomotive.ca
AEM Factory Trained, Accel EMIC, Haltech Trained, Advanced GM EFI, Diablo CMR Mopar Dealer, SCT TUner - Viper/SRT10, Delta Force Dealer.
Analog DD 450
Mustang MD250 - gone but not forgotten.

Techsalvager · Joined: 21 Jun 2011 Posts: 140

I've been testing, indeed to close to the turbo there is tons of reversion letting the throttle close. I don't have a blow off valve currently.

terms of blow though well the pcv isn't hooked up to the intake tract and taking off couplers and piping I have not seen any oil residue in the system.

in terms of straight pipe diameters, if I have a 80mm maf, does that mean I need 240mm length of 80mm pipe before and 160mm of 80mm pipe after?

This how they implemented it in MS http://www.microsquirt.info/mafmap.htm
Though thats for B&G firmware not sure if MS2extra uses the same implemenation

Even so when running with a 55mm ford maf I've found engine responce and driveability was a lot better compared to my speed density tune. Now of course I'm not suggesting I tuned the speed density setup the best possible and it sucks, just that swaping to maf setup with a rough transfer curve and little tuning showed that much promise to me says volumes.

I found out that the nissan maf VQ curves are not airflow to voltage charts.
I can't seem to find any place with airflow to voltage curves. so I decided I will take a throttlebody\butterfly, straight pvc, and a vacuum and a known maf to test aganist unknown mafs and get a rough curve sorted out.