ruf_turbo

Talk to your tunner if you have a tune.

Not all tunes/tunners support MAFless.

 

The OP said with the MAF removed the tune switiches to MAP sensor so I assumed it is a speed density set-up which is fine. It's just with speed density, you need to know the VE of the motor to calculate air flow. I don't believe Proto has mapped out the VE of the OP's mods but probably has similar data for a related system which will be used. That's fine but I don't think it will be an optimized tune and it will need tweaking. I don't think the OPs MAFless tune will ignore boost which is essentially an alpha-N tune dependent on throttle position and rpm, except maybe at WOT when MAP is relatively constant.

 

ME7.8 is unable to calculate load based on MAP, that is fact. In regards to load the me7.8 dme doesn't even really know what boost is... Its a torque based management system and fueling, ignition timing are solely based on inputs derived from airflow and feed back from the o2 sensors, IAT sensor, CTS, but not the map sensor.

Ill say it again, the ONLY reason this works as well as it does is the fact that these cars run basically closed look to redline with individual bank wide band control.

If you dont believe me, data log load, requested load, ignition timing at 1 bar and then redatalog at 1.5 bar. The values will be basically the same despite a HUGE difference in airflow (thus there should be a huge difference in load). There may be slight variation due to iat, knock sensor input, etc... But map sensor data does not come into play. Basically...its not speed density.

 

I don't know if the DME is unable to calculate load based on MAP (maybe on a 996t) but just trying to better understand what you're saying. What I am wondering about is fuel delivery. For MAF, my understanding (and please correct me if I’m wrong) is that fuel flow rate is the product of MAF and target A/F ratio. So as you stated, actual boost pressure is not involved. If MAF is missing, then what parameter is used to figure out air flow? None? I assumed it was measured indirectly based on MAP readings. As you know, with MAP measurements, you can calculate air flow using the ideal gas equation and knowing the motor’s VE. The motor’s VE (load) is derived from MAF(before removal), engine displacement, density of air, and rpm. So one can build a VE table consisting of pressure and engine speed from which fuel delivery is mapped. Help me out here, if there is no fuel map, then by what mechanism or how does the O2 sensor information get processed to deliver the right amount of fuel? Are you saying that if the O2 sensor reads lean, then the injector duty time just increases until it’s goes rich? And this oscillates back and forth at all rpm’s? If that’s the case, then how can this be very efficient?

 

I also run a mafless tune. Yesterday i spoke with a guy who does REVO programming, he told me that MAFless tune can dammage the engine under some conditions. For example he said if for some reason something goes into the airbox and the air flow decreases the car cannot read air flow but still runs same boost. Also when air temp is very high etc.

I know that guy is not very familliar with Porsche cars so he might be mistaken, can anyone answer this,

Is it possible to dammage the engine just because of MAFless tune?

thank you

 

I'm running without mafs for a long time, no issue at all.
997 tt has so many sensors that I doubt maf less can be a reason for engine damage.

I'm running still with mafs but plugs are disconnected, good idea I will remove them.

 

You can damage your engine with a maf tune as well. If the maf sensor is dirty or malfunctioning in a way that is under reading the flow (or you have a leak), then your motor has a chance to run lean at high boost. As with high temp, I'm sure Todd programmed in scalars to account for different IATs. No worries.

 

997.2TT does not have MAF's from the factory.


This was posted by a tuner although he did not provide the answer

The 996TT uses the same MAP as the 997tt.1 and 997TT.2.
The 997TT.1 can run Mafless yet has a MAF as does the 996TT.
The 997.2 does not use a MAF Though.
What is the difference as to why these cars run this way?

 

i also run maf less

 

SMR

That's neat, did you fabricate the plug?

 

As you know, the tuner is Softronic. He is like the Riddler in Batman--aahahahaha.

 

Maybe Porsche figured if the 997.1 could run MAF'less they could take the MAF's off the DFI engine and save a few bux. Maybe BECAUSE of DFI they aren't really necessary.

 

More like a Joker and Riddler hybrid.

 

Thats theory is absolutely not correct Every ME7.X ECU used on turbo car(with MAP sensor) can work MAFless mode if its mapped correctly. Wideband ECU or early style narrow band is not important, both ECUs can run without MAF with boost compensation for load.

No, If you have proper MAFless tune you will see diferent % load on 1bar boost and on 1.5bar boost i.e MAP sensor max value, over 1.5bar you cant compensate for load with stock MAP sensor but if you change MAP sensor and try to use 3bar MAP then you can properly compensate for 2bar boost

 

I think EPL is more used to dealing with 996ts, although the load and boost comment was a bit odd. Not sure what he meant by it as clearly load is not independent of boost.