School me on MAF less
 

ran into a guy who just got a Cobb MAF less tune and he says his car runs very smooth with lots of additional power. I understand the additional power but ive searched to try and understand why his car is running so smooth without a MAF. teach me something, please. Thanks.

Hey Gt3.

There is a MAP sensor and Cobb has a load sensing set up that runs it like a 991 for example using other information. All safeties are in place and it works really well. Feel free to reach out and I can help you with trying it out. We can build you the same exact map both ways. Full guarantee!

And there are 996 Turbos with tunes that retain the MAF, and that run very smooth with lots of additional power.

Its all about the tune & quicker spool time/flow to & from the turbos.
Mafless systems support 600+ HP & much more.

Mafless incorporates larger y-pipe, eliminates factory air box & turbo air supply plenum. Most use fender well intakes.

I've got EVOMS Stage II tuning with something around 500-520 Hp. The tuning retains the MAF. My engine runs very smoothly from idle to redline. The tuning has been bulletproof.

If I didn't have a tune, I'd without question go with UMW and Kevin's custom turbos because of its better low-end power.

There are two schools of thought for this--

The stock Bosch MAF can only see something like 600hp worth of air flow, and the 996TT intake tract is quite long and convoluted. The stock MAF is also a common failure item. Many people feel the solution to this is to go MAF-less, relying on the factory ECU's fallback speed density/Alpha N system (boost pressure x throttle plate angle) to measure load. This system works by saying that at a given air pressure and temperature ahead of the throttle body, X% throttle plate angle SHOULD results in Y air mass should be drawn into an engine based on a calculation of air density (pressure x temperature), a mapped table of pressure differential across throttle body vs. throttle angle, and a mapped table of engine volumetric efficiency.

The reality is that this measuring system is not terribly accurate on this car, as unlike the 997.2 and 991 that come stock running speed density, there is no MAP sensor inside the intake manifold itself so there are a lot of assumptions/calculations made to come up with an air flow figure. This means that fueling and ignition timing is never totally on point, so especially at low load, partial throttle, and under transients the car tends to run richer/leaner than ideal, which reduces power and sharpness of engine response. Most of these cars run ok at full load where all the tuning is done, but the engine management can't really keep up outside of that.

There are other compromises you make when pursuing a MAFless system. There are a bunch of cars running around with 'MAFless' tunes with the stock airbox/inlet system in place. I assume the MAFless tune is done in these circumstances to deal with the limitations of the stock MAF, and you keep an intake tract that functions like stock otherwise--air drawn from the top of the car, no dirt/water ingestion issues, etc. With upgraded inlet ducts, these systems work well up to 800hp or so, but you have the driveability issues outlined above.

However, there are other cars that have the intakes off of the turbos, being drawn through the fender liners or intercooler ducts. This is tricky to do, as you end up sticking the filter some place where it is exposed to dirt or water off of the rear tires, or it takes valuable air flow away from the intercoolers. We've done cars like this before, mostly when we make more than 900hp or so and you don't have any other options to flow that much air. For a street car making 600-700hp, it isn't necessary and you compromise the usability of the car by doing it that way.

We went another direction. The MAF is fantastic because it gives you a direct measurement of airflow under any circumstance. If your MAF sensor and housing are properly calibrated, it is a very accurate and precise way of measuring air flow going into the engine, which makes it very straightforward to do calculate how much fuel needs to be delivered, and how much load the engine is under for calculating ignition timing, torque production, etc.

To get around the limitations of the stock Bosch MAF, we developed a conversion kit for our V-Flow intake to use a Hitachi MAF sensor and a software calibration to work with the new sensor. This sensor is much more robust than the Bosch sensor, and is capable of seeing very high air flow levels. With our V-Flow intake and high flow turbo inlet ducts (https://www.evoms.com/Porsche_Turbo_...kfaid996tt.htm) we build an intake tract that supports over 800hp, and does so with EXCELLENT driveability and consistency. It lets us do things like this, making 660wtq by 3500rpm and a peak of over 700wtq on a GT700 with a built motor. With a fuel pump upgrade, this car does just over 700whp now on the same induction system.

https://c1.staticflickr.com/3/2806/3...dd040dbc_b.jpg

Another benefit is that keeping the MAF sensor in place allows us to maintain almost all of the factory diagnostics, so the car will self diagnose itself should it develop an air leak. Almost every single time we get a >Stage 2 996TT in here that is converted over to our software from other brand, the car starts throwing faults that can be traced back to minor air leaks/mechanical faults that were undiagnosed on the previous tune.

Sam

Wait, I thought the 996TT had a real MAP sensor from the factory? What is 996-606-180-00? Is that not a MAP sensor in the intercooler pipe?

Dan

That is simply a pressure sensor measuring Y-pipe pressure pre-throttle body. This is what gives you the boost read out in the cluster.

Sam did my MAFless on Cobb, I came from a GIAC tune. I went from the MAF busting v-flow intake to the stock unit at the same time.

I had all the same reservations many do about drive-ability with MAFless but now I'm a believer. 1/50 transitions from no throttle to <10% throttle can induce a slight lull in power for .5-1 seconds but that is literally the only "complaint" I have. Overall the car makes boosts sooner, drive smoother, get A LOT better fuel economy, is more consistent across altitudes and temps, and is just overall better since Sam blessed it.

Just another data point: I've had the EVOMS GIAC Stage II "Hammer" tune with the EVOMS V-Flow for over 12.5 years, and until just a few months ago the car ran as smooth as silk. In January the car started having some slight roughness at idle, but ran perfectly above that. It was time for a plug change, so I decided to install a new OEM MAF at that time. Everthing is back to silky smooth.

Mafless is the only option to solve the "abortion style" factory intake plenum & kinked turbo inlet piping.
The turbos get the air they need quickly with fender well system. They are almost 6ft shorter.

Just look at the compression & kinks of the oem piping.

One note I can add is that getting the airflow meter out of the equation takes some of the "dampening" away. I've had a couple cars mention the same sort of symptom and got it fixed with either cleaning the throttlebody and or a new fuel filter. This is on any sort of intake. There definitely are a few good ways to go about it and great tuners how can I help. On the subject of Cobb I'd be glad to stand behind it for anyone who's interested in trying it but wants to be guaranteed support. I got you.

hammer time! love it..assuming it came with the pants? there was a lotta of room there as i recall. ( can't touch this :) )

so, tunes have improved, or so it is said. an evoms w hitachi setup is no longer the "latest and greatest", rather more like what was available 12-15 years ago. much like the the cargraphic/fvd/evoms/giac and whomever else of the "time". if all one hopes to achieve is a smooth running car touching 500hp crank? then ok, sure.

but the reason your car runs so great ( like mine w an "old tune" and "old" hybrid 16/24 turbo's.. ) after simply changing spark plugs ( lol ) is mainly because you haven't asked anything more of it since you tuned it! :)

all kidding aside. your evoms "stage 2 kit" first introduced when the 996 turbo was lol.. consisted of a flash tune, and air filter ( fancy/schmancy ) the hitachi maf ( or was that another add-on option? ) and some spark plugs :rolleyes: while doubtless better than stock, and also better than nothing else, it didn't then ( and sure isn't now ) exactly setting the world on fire. just made it a bit warmer.

pics of the pants with the tune.. or it never happened :)

Well that's disappointing... I would have thought Porsche would put a true MAP sensor after the throttle...

Dan

EVOMS called the particular tune I purchased the Stage II Hammer tune. If you have issues with what they called it, take it up with them.

The EVOMS tuning in my 996 Turbo used the OEM MAF. Like I said, I used my OEM original MAF with this tunning until January of this year. With the V-Flow and an exhaust upgrade (I have the Europipe Stage II Loud), EVOMS advertised 520hp/520 lb-ft of torque.

520 hp and 520 lb-ft of torque (or whatever it actually has) is for me a great street driving target level (today, and as it was over 12.5 years ago), and it has been very reliable (while retaining the MAF and using the V-Flow).