Mongo

That would be great Carl!

I was reading the forums on EFI101.com and people are complaining about the Electromotive products. TecGT seems to be the better mousetrap out of all of them, but someone had mentioned issued with the autotune feature for the VE (Volumetric Efficiency) tables. Did you have any issues with this when tuning?

Alan

I imagine boxer engines need to have 2 sensors due to the extreme head seperation so maybe that influenced Porsches generic engine controller design specs for Bosch... Once you have provided for it maybe adding 2 sensors to the flagship product didn't seem overboard...

Alan

Mongo

Found a couple threads on TecGT in the 951 forums. Owners of it praise it and its plug and play system puts the fuel maps almost dead nuts to what is required to run the car without any issues. I hope it's just as easy for the 928 upon initial startup.

Ben Allison

The knock sensors listen to the cylinders, not the heads...

Carl Fausett

Auto-tune features are scarey. The TecGT does not have what you would call "Auto-Tune". What it has would be better called "Auto VE Correction"

It works like this: you tell it via the VE table what A/F ratio you would like to see in every box of the VE chart. Maybe 14:1 at idle no load, up through 12.1:1 under full boost and full load, and everything between.

Then you can assign a percent that you will allow the ECU to nudge or correct the A/F as needed to hit your target VE table. You can assign from 1% to 50% correction factors.

In this way you have greater control over the power that the system has to make changes without your permission/input.

Mongo

Great! That would be very helpful for emissions purposes too and getting it to pass the sniffer test. Just out of curiousity, at full load, what would the A/R be on an NA car? up to 12.1 also?

dprantl

12.8:1 would be what I would shoot for.

Dan
'91 928GT S/C 475hp/460lb.ft

Alan

Well of course you're right... but the compression ends of the cylinders just happen to be far away from each other too for the same reasons...and there is no convenient V bridging them together...

Alan

Carl Fausett

If I installed an electromotive system on a NA car, and I was going to go for emissions recertifications, I'd set everything to 14.7 and drive to the certification center. Your hydrocarboins will be way low and you will pass.

Then go home, and load the "other" fuel map that you prefer for performance. No changes to the car would be necessary.

You can have an unlimited number of engine maps on your laptop. Load the one you want into the ECU in about 10 seconds after plugging in the cable...

dprantl

Since no emissions test will do any testing at WOT, I don't think it would be a problem to load up a map that has the most efficient WOT AFR. At part-throttle, the car should be at 14.7:1 and using the O2 sensor to compensate. That way you can have one map for everything. For example, my car runs super-rich right now at WOT, sometimes less than 10.0:1 but it passes emissions just fine, since they do part throttle runs at two different loads at 15mph and 25mph. If they ever did a WOT emissions test, not even the newest cleanest cars would pass. Every car I have ever seen go to WOT in front of me (including 2009 models) has had a brief puff of smoke out the tailpipe as the ECU switches to a richer mixture.

Dan
'91 928GT S/C 475hp/460lb.ft

Carl Fausett

Yes it is. We were producing 11 pounds of boost in the plenum at 6500 rpm.

Carl Fausett

Yes. The spark plugs are perfectly colored and matched after my weekend at Road America, confirming we have very even air and fuel distribution.

Carl Fausett

I had the intake manifold off this weekend and grabbed a photo of the knock sensor location in the 5.0 Liter block.

Because I am only using a single knock sensor, I used the location (provided) in the center of the 8 cylinders.

Hard to imagine locating ther knock sensor any more perfectly on-center than this. Thank you Porsche!

Forgive the poor pics - taken with my phone...

Mongo

As long as splicing the 2 works, I'm plenty happy doing that when the time comes.

Any ETA on when you do the 928 GT TecGT conversion?

Carl Fausett

The knock sensor is a simple piezoelectric device.

More info here: http://en.wikipedia.org/wiki/Piezoelectric_sensor. Like all piezo sensors, they produce their own electric current.

Splicing two together will just increase the current the ECU sees. Because you can raise or lower the threshold of the "normal" engine noise on the TecGT system, you could wire in as many piezo sensors as you like and just adjust the threshold for the new level.

As far as a schedule, I am finishing up a 968 SC kit (its already running), and the 91 928 Electromotive install is the next project.

I should be able to start this project within this month. I dont think it will take very long.