Anyone knowing what the airmass meter is used for in the ECU of the 993tt?
Since there is no electrical throttle and no cams that can be varied it should be enough with a pressure sensor and a temp sensor. Maybe the EGR can mess things up a bit but....
I used to work at SAAB with the Trionic system where we used the airmass meter to control the electric throttle to give us wanted airmass into the engine.
With a mechanical thottle the airmass becomes what it becomes so to speek, when you open the throttle, so why not just measure intake air pressure and temp and let that adjust your fuel and ignition?
Is possibly the turboboost controlled against the airmass meter?

 

Howdy Thomas!
Welcome to Rennlist, this is just the place for a person like you

You wouldn't happend to have a few pictures of your 993TT to share with us?

 

Thanks Rassel!
Well I have a few cool ones.....

 

and this one...

 

and another one!

 

I'm terribly sorry Thomas that I've spoken so warmly about Rennlist the technical knowledge of the 993TT board. I guess I was wrong...

(Come on you slackers, prove me of being wrong!)

 

If you switch to an aftermarket ECU, you would use only a TPS, MAP, and Air Temp sensor to meter the fuel. The Mass Flow sensor would not be needed.

 

Thomas,
Your ECU can be reprogramed for speed density (map) sensing, no need to use stand alone stuff,let me know if I can help you.,cheers,Sonny.

 

I'm just wondering why there is a airmass meter in the original system. I'm looking at the possibility to put the SAAB Trionic system on my 993tt. That system supports e-throttle (which I won't use), airmass meter plus the pressure and temp sensing. It must be for a reason Porsche has the mass air flow sensor and not just the pressure/temp.

 

If you are familiar with the Trionic or Bosch ME7/9 system then you will know why the Mass meter is there.An OBDII spec motor would have a tough job complying with emmission standards running a speed density system.The map sensor is there for final boost level reference.
Good luck

Geoff

 

The 5.2 Motronics for the 993TT does not have a MAP sensor. However if you'd like to dump your MAF unit you will have to convert to a Load Signal Converter with the addition of a MAP sensor. Do you feel that the Trionic ECU is better than the Motronic ECU?

 

There is no pressure sensor on the 993tt??? Are you sure! But the pressure indications presented on the dashboard then, where does that come from?
Well as you say, there is only need for one load signal....if it comes from a pressure/temp sensor or an airflow sensor does not matter as long as you don't have variable EGR or variable cams, since this influence intake pressure without the correlation to flow through the engine.
ME7/ME9 are systems that are designed for e-throttle and to handle variable cams. Then the pressure does not correlate to the actual airmass in the cylinder ==> airmass meter is necessary.
Futhermore the OBD2 system is just a diagnostic system due to the fact that there are no annual checkups on cars in California. It does not stipulate any emission levels, only that the system shall detect errors that make the emission rise by 50%. But you're right that with an airmass meter it is probably easier to comply with stricter emission requirements.

Anyone having a ECU schematics for the 993TT?

The reason for my interest in Trionic is that I have that system at home and I know the SW in it. I wouldn't say it is better, but it would give me more freedom to do what I want.

/Thomas

 

Thomas,

Lots of ways to address the poorly designed stock setup. Glad to see you thinking outside the box. One look at the stock setup and even a fool would see it far from ideal. You would be hard pressed to find another turbo car trying to control boost without a MAP sensor.

I am not sure if you are looking to achive better results of you like the challange of the project.

From a results POV Protomotive has achive what I consider to be one of the better balanced approaches. Todd installs a EBC to controll boost levels. The EBC is second to none when trying to control stable boost levels. There are many many great products on the market. Greddy is one fine example. He then fine tunes the setup from there. Since he has done lots of cars this way he has really got the setup dialed in quite well.

Motec is altogether the best option. The time involved to get the car setup correctly makes it less desireable from my POV.

If you got the time it would be interesting to see the results from your approach.

 

The boost sensor does not have control over the air density calculations for fueling in the Motronic ECU. The MAF takes care of this function.

A standalone ECU might be of better use for your situation. If you can get the Trionic system to adapt and you have the code, that might be a better route for you..

 

According to the factory wiring diagram the pressure sensor only supplies data to the boost gauge in the OBC; it isn't fed to the ECU. The wiring diagram indicates which sensors provide feeds to which systems but doesn't elaborate on how those systems use that data.