speed density benefits?

[Dannyho]

I read in one of the threads a while back that our cars don't have a MAF sensor, which implies that it's a speed density system, as opposed to alpha-N, like most car's I've worked on.
Are there any benefits to this that will show themselves when we start putting new parts on. Does it adjust to the new parts better perhaps without a tune? obviously I'm not talking about a bigger turbo or something crazy, but I'm just curious.

or maybe I misread and there is a MAF in there.

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[ABQstang05]

Interesting thought. I would assume it remains a good model as long as the volumetric efficiency isnt drastically changed. I assume a table is used for this....?

 

[mbreinin]

No MAF. SD is much simpler, adapts easier and is more effective in my experience. I hate MAF cars.

Mike

 

[superblur]

No MAF. SD is much simpler, adapts easier and is more effective in my experience. I hate MAF cars.

Mike

I thought it was the exact opposite....?

MAF has the ability to read air coming in and adapt where as speed destiny has to be tuned to assume certain variables are true in the engine thus doesn't adapt well and takes a lot of expertise to tune.

 

[foghat]

I thought it was the exact opposite....?

MAF has the ability to read air coming in and adapt where as speed destiny has to be tuned to assume certain variables are true in the engine thus doesn't adapt well and takes a lot of expertise to tune.

+1. That is my understanding as well (at least on the 'adapts easier' comment). Though I will admit my understanding on the matter is very limited.

 

[mbreinin]

Speed density is easier to tune, and requires less hardware changes. When you have a closed loop system operating with authority to make fuel trims based on 02 readings, it is plenty adaptive for high performance.

Mike

 

[Jimdohc]

I would never modify a speed density engine without a proper tune (should tune MAF systems too for max performance benefit). Shouldn't rely on closed loop feedback to protect your engine. It can correct bad AFR but that means there was a bad AFR. It's like saying, if I'm punched in the face a few times, I'll learn to move. Learn to move before you fight.

Speed Density is more reliable and does not restrict intake flow.

Normally, MAF is easier to tune. Ultimately depends on tuning software. Some cases Speed Density would be easier.

Modern MAFS only require changing the housing to increase their flow. It's usually included with aftermarket intake system but does require a tune.

Alpha-N is usually used for "limp mode". In some ECU, when a sensor like MAFS goes bad it trips the ECU into alpha-n limp mode.

 

[midnite9150]

MAF was better in the old days of 8MB computers, but with the far better computers today with variable valve and cam timing speed density is much better

 

[Dannyho]

so a speed density system is more sensitive to making changes like a CAI or downpipe than a MAF system would be?

 

[Ryudo83]

i personally would prefer speed density for a tune. There are a bunch of Subaru guys who switch over when trying to make big power for reliability. Things can get gimmicky with a MAF, ie an intake that "moves" the MAF to adjust for the flow rather than tuning it.

 

[mbreinin]

I can't think of one stand alone management system that utilizes a MAF meter. In high HP forced induction applications, it is common to shut it down with system like HP Tuners on stock GM computers.

 

[Jimdohc]

so a speed density system is more sensitive to making changes like a CAI or downpipe than a MAF system would be?

In general, yes.

But no worries, IMHO Speed Density is better than MAF based.

MOTEC, Haltech, AEM, HKS give the option to use MAP, MAF or TPS.
some of the above can run a hybrid version of TPS & MAP.

 

[tmcphail]

Each system type has its own inherent strengths and weaknesses. Overall you can do yourself a disservice by proclaiming one is superior to the other unless you spend a lot of time working with both as I have within the OEM controller spectrum. We must remember that before the first 3.5L GTDI Ecoboost engines that were released in 2009 for the 2010 SHO just about everything that came out of Ford prior was MAF dating back to 1987. I have worked on a ton of MAF based Ford vehicles in a wide range or power levels all the way up to 1500WHP TTSC Ford GT's.
The Ecoboost engines have all been CL / SD and function really well from a design & control standpoint. There is no question as the days pass these systems grow exponential in the level of complexity. But this is all based on working within OEM systems and calibrations. I don't personally work on or tune stand alone controllers.

It's totally ironic for me to see Ford move away from MAF and watch Dodge actually go towards MAF on their vehicles. They are both simultaneously moving in opposite directions

 

[B-Fox]

The main benefit of using speed density in Ecoboost applications is getting away from MAF latency,
you have to remember that traditionally air would flow from the airbox, through the MAF and then straight to the throttle.
Now when you add in piping to the turbo, then to the intercooler and then to the throttle this causes a noticeable delay in MAF signal.

 

[DeliciousTuning]

There are pro's and con's of each and every time a new vehicle comes out this debate always comes to the surface right away. LOL From our experience in the Subaru world here is what we see as the benefits and drawbacks of each, which should follow closely with the EcoBoost engine.

MAF Benefits
- More accurate way of measuring actual airflow into the engine based on temperature, and altitude.
- Changing parts on the car is ok to a point and the MAF sensor can scale with the better flow into the engine, providing more fuel etc...
- Usually better throttle response, while measuring actual airflow, not a calculated number from MAP.

MAF Drawbacks
- Any time you change the intake it needs to be re-scaled for the new intake
- You may be limited by how much power you can make because the meter will max out at some point or another, though usually fairly high

Speed Density Benefits
- If a VE tabled is scaled well, you can literally throw any parts on the vehicle and the tune will adjust for you. Makes for a lot easier tuning. This includes intakes.
- This can leave a lot of room on the table for big power and basically never limited. Only limited by the size of the MAP sensor you use.

Speed Density Drawbacks
- Tuning in a Speed Density tune from scratch can be a pain but if already done (done well I mean) from the factory can eliminate this issue, to a point of course.
- Tuning from scratch on Speed Density can be a pain in the butt to get everything working the way you want.

At the end of the day, they are both good systems and why all the manufacturers keep flip flopping between the two I do not really see a whole lot of benefit over the other, except that the MAF sensor can be in the way sometimes when plumbing parts.

Cheers,
William Knose
Delicious Tuning

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