Tuning ECU on FC
 

I have heard that I can lean out the ECU by altering the resistance of the signal of the water sensor.
Anyone have any knowledge of this setup?
The car is an SCCA ITS 2nd gen.

Thanks,
Charles Buzzetti

Isn't that against the rules?


-Ted

not if you dont get caught

This was the rule before they made the new ECU rule (can do anything inside ECU box as long as you use factory harness and plug) read MOTEC here. $3500+.
There is a recomendation to add the wording to include the old rule since many of the cars had this done already.
Just trying to find out what gains can be had with this mod.
And yes if you buried this into the harness it would be almost undetecable.

Cbuzz

Actually the rule is, as long as you put the resistor between the sensor and the stock wiring harness you are O.k.. I know a Motec would work, but how about a Haltec. Can you get it to work with all the stock sensors including the CAS. I had look into using a Mega Squirt but found that it would not work with the stock CAS.

Adding the resistor is the old rule and it has been deleted as Buzzin said. I just sat in on a Miata tuning session yesterday where a resistor was used on the AFM. It leaned out the entire curve. Same would happen with any water temp resistor. A legal way with easier adjustments to do the same thing would be to add a fuel pressure regulator.

My opinion FWIW on the ECU modifications is to either a) change the rule back t allow only stock ECUs or b) open the wiring and sensor rule up so that we don't have to spend the $3500 to shoe horn a Motec into the stock case. Spending $3500 is way too much for IT but guys will do it. Speedsource says the Motec is worth 10hp bottom to top. That's alot. A guy could do the same thing with a Haltech for ~$600 plus some dyno time.

Thanks CL I will try taking an adjustable FPR with me to the dyno to see what that nets as far as HP and TQ.
I have not yet had the injectors blueprinted. I need to get another set to send out so I can change them all out on the same day.
Any other suggestions?

CBuzz

Yeah, my advice is don't spend too much time and money on the dyno.

Last spring I built a new motor. New everything except rotors and e-shaft with carbon seals. For various reasons I only got to drive the car one weekend last year and that was the 4th of July weekend at Mid-Ohio. There are always deep, strong fields at Mid-Ohio with 20 or more ITS cars being common. I ended up with a 2nd and 3rd for the weekend. Pretty good? Well, during the whole weekend I was way down on power and couldn't figure out why. I guessed I was 30hp down on the field and had ITA cars running on my ass down any straight piece of track. The saving grace for the weekend was all the chassis work we've done the last couple years has really worked out and the car was an absolute jewel to drive. I turned some of my quickest lap times ever at M-O but was really bummed because it looked like I sucked as en engine builder.

First thing I did when we got home was go straight to the dyno to set a baseline before I started trouble shooting. Speedsource says their setup will put 175hp to the wheels. My exhaust is far from optimized so at this point I'll be happy with 160-165hp. I made 110. So I was down 50-65hp on the field and still had great results. In the end the problem was traced to the throttle linkage. The double throttle on the secondaries had come loose and the butterflies had fallen closed. So we were only running on the single primary butterfly. One hell of a restrictor!!! I'll finally make it back to the dyno next week to see where we are with all three throttle bores breathing.

Later last year after I found the problem and fixed it I leased the car to a rookie driver for a weekend at Gateway. With the exception of a BMW there was nothing there that had motor on my car. But with a green driver the lap times just weren't there.

The moral of the story is that while horsepower is important at this level of racing there is far more time to be had in tightening the nut behind the wheel than in motor tweaks. Motor work is important but don't waste development time or money on finding 4hp when you could be at the track turning laps which improves your skill and knowledge of the chassis setup. Track time is more fun than dyno time too.

Wow pretty good finish for such low HP!
Now I have to check all my linkages and throttle cable and alignment settings etc.
Having used Data Aq. many times I am well aware of my short comings and strengths as a driver.
I know I will always need the practice.
Once I get a baseline HP for my car I will decide if I need to chase the power.
Thanks for the info.

Cbuzz