I had my computer hook up to the Autronic ECU the other day and notice that the throttle position was not getting to 100%...........all I could get to was 98.2%.
I did several tests to see if the throttle plates were opening to 90 degrees (100% throttle).
The tests included
1. Taking a mirror and looking down the throttle bodies to see if the plates were at (90 degrees) at WOT when working the bell crank by hand ............and they sure looked like they were and I was hitting a stop that sounded like it was in the throttle bodies.
2. I removed the throttle linkage from the bell crank and work the bell crank by hand and got the same 98.2% throttle reading when hitting the stop .
3. I lenghten the throttle linkage a little........No change still 98.2% when hitting the stop
4. I preformed volt/Ohms tests on the TPS and found all values fitting within the range called out for in the Autronic Manual.
5. I talked with Twin Induction and found that my throttle bodies has a built in stop to keep the throttle plates from going past 100% open (90 degrees).........That pretty much says what I thought all along that the throttle plates have a built in stop when they are fully open and that stop must be the one I was hearing in the earlier tests.
After doing this I can say for sure that the throttle plates are opening 100% and the TPS is functioning OK but for some reason the ECU is saying it's 98.2%
Now the Autronic has a nice feature called "Throttle Limit Learning"
that will learn the throttle travel by just unplugging the TPS connector with the ignition on followed by at least 5 seconds with throttle closed followed by at least 5 seconds with the throttle fully open.
But until I get the go ahead to use this function from Bob (Autronic Dealer/Tuner) I'm afraid to use it.
You might wonder what the big deal is between 98.2% and 100% throttle but as you can see in the tables below for Base Fuel Delivery
and Target A/F
there's quite a difference in the cells for 90% to 100% (A/F Target Table) and 97.5% to 100% (Base Fuel Delievery Table).
Any opinions of whats causing the down drifting % of throttle readings?
1. Base fuel delievery table
2. A/F Target Table
3. TPS Setup in Autroni Manual including Volt Range for TPS and the "Throttle Limit Learning" function instructions.
4. My work table.
5. The new gas pressure gauge. The black gauge looks much better then the red one IMO............Much Faster Too!!!