just wondering how everyone determines what to set their low and high throttle percentages at. is this more or less a standard number, or can you only determine this by looking at a dyno graph?

this is for a S5 non-turbo, i have an SAFC-II. just trying to figure everything out before taking it to the dyno...

 

With the S5 NA you have a lot of latitude.
Maybe 20-50 low & 60-90 high.

Of course dyno tuning is best.

 

cool, thanks for the reply.

now will being on the dyno let me know what low/hi throttle point to select?

also, further on this topic, with an SAFCII on an NA do you tune strictly for AFR on the dyno or try to use the power curve printout and adjust?

- Aaron

 

MANIFOLD PRESSURE!

Throttle position is totally unrelated to engine operation. It's just a manifold pressure control, and it's not even linear - at low throttle, you're at full manifold pressure by 20% throttle or so, and all the rest of the throttle isn't changing anything (except maybe opening the secondaries more & reducing primary velocity).

-=Russ=-

 

you are saying i should use the pressure sensor instead of the TPS?
i was under the impression on the series 5 the full range TPS is a better thing to use.
could you explain a little further?

- Aaron

 

The S5 wide-range TPS will work and report accelerator position properly, yes.

However, the throttle position really doesn't affect engine operation directly. It controls manifold pressure, and acts differently at different RPM. At low RPM, specifically, it doesn't take much throttle opening to produce full manifold pressure. This is why at low RPM, the first little bit of gas pedal travel does something, then the rest does absolutely nothing - you're already at max manifold pressure.

The advantage of using the boost sensor or pressure sensor is that you can tune based on what the engine is seeing, not some arbitrary input that doesn't actually affect engine operation directly.

Also, with a turbo, you can then tune based on boost pressure.

-=Russ=-

 

well, the way i see it is if you have a dyno to tune with, using a full range TPS reading gives you a lot more room to work with.

however the pressure sensor may be more useful on the street since it will tell you right away if you are at full load.
seeing how with an NA you reach that pretty quick though, i still like the full range TPS better.

- Aaron

 

This is where NA & turbo fuel requirements are way different.

The TPS input is more usefull on an NA.
Using the S5 TPS will hold you in the lean map at low throttle & low revs which can save gas.
Only when you do floor it for more power does it go to the high map.
On an S4 you're stuck with a short range TPS, so the boost sensor is better.

On a turbo, the MAP can shoot up at mid revs & low throttle, so using the pressure signal can get you in the high map sooner to keep up with boost.