s54/MSS54 Detune

[BBRTuning]

Stupid question time. How does a detune dyno? Does it just flatten out at the top end target #? How much is trial and error?

Pretty much. Depends on the particular racing class' requirements. Some just have a simple peak HP value you have to stay under, some average it over a certain RPM range. You also have to consider whether or not the sanctioning body will actually dyno the car vs. just use your dyno sheet as proof, in case their dyno may read differently than the one used during the tune.

Here's an example of a K20A3 CRX I tuned that had to be under 155whp for a particular class. Because it was just an absolute # limit, I kept the power just below 155 for as wide a range as possible. The car also has a switch to allow full power (all 170whp lol) for track days.

[eacmen]

Pretty much. Depends on the particular racing class' requirements. Some just have a simple peak HP value you have to stay under, some average it over a certain RPM range. You also have to consider whether or not the sanctioning body will actually dyno the car vs. just use your dyno sheet as proof, in case their dyno may read differently than the one used during the tune.

Here's an example of a K20A3 CRX I tuned that had to be under 155whp for a particular class. Because it was just an absolute # limit, I kept the power just below 155 for as wide a range as possible. The car also has a switch to allow full power (all 170whp lol) for track days.

“for track days” ... yeah right. 😉

[bigjae46]

Pretty much. Depends on the particular racing class' requirements. Some just have a simple peak HP value you have to stay under, some average it over a certain RPM range. You also have to consider whether or not the sanctioning body will actually dyno the car vs. just use your dyno sheet as proof, in case their dyno may read differently than the one used during the tune.

Here's an example of a K20A3 CRX I tuned that had to be under 155whp for a particular class. Because it was just an absolute # limit, I kept the power just below 155 for as wide a range as possible. The car also has a switch to allow full power (all 170whp lol) for track days.

My ever changing goals. I will... someday ...
run TT and then race the car (or at least get it ready so I can sell and upgrade to an E9X M3). It would be GTS3 with NASA or BMWCCA.

I would be average HP for NASA.


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[Pavlo]

Your power delivered over time is what gets you moving (so the area under the curve). Since NASA does an average over time, you may be better off just lowering the rev limit; this way your rod bearings will not stress, you will build less heat, and use less fuel. Ideally you'd want to play around with data and look at things like an RPM histogram to tell you what RPM you need your torque at most. Detuning an engine with drive by wire and variable cams is quite easy, the challenge is really figuring out how to fit the rules while keeping the S54 advantage.