s54/MSS54 Detune

[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.

[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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[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. 😉

[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.

[bigjae46]

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

[Arith2]

I would like bump this thread because I'm am also curious what table does what and how to properly tune this specific DME. I have training in other software that makes it stupid easy but tunerpro is anything but user friendly. That data is just all raw. I want to go through my Buildjournal can tune I bought a few years ago just see what they changed. It would be nice to have something more simple than tunerpro. I'd pay for something better.

[JBAshland]

That's only going to relate to torque interventions, not normal operating conditions.

I agree with BBR! Adjust power output via VANOS and the 23x14 Throttle Map (linearizes open-loop air mass flow control to account for the non-linearity of the throttle position to throttle area).

Thanks SliM3 and BBR. Both very helpful and obviously knowledgeable on the topic.

SliM3 - I have been reading many of your past posts on these topics, and I can't get over the amount of work you and others put into these efforts to benefit the community. Thank you. Your post explaining the Vanos table was very helpful to understand how the values within correlate to degrees. As for the Throttle table, maybe my XDF is wrong for the .Bin I am applying it to, but I do not see x and y values that make sense. For the header/'x', I would expect to see RPM when displaying the tables in TunerPro - in attached .jpg you'll see they all display as '00'.


I am still trying to wrap my head around how it might be best to adjust and perhaps reduce overlap from say 5000-8000 in order to flatten my HP curve. The way I see it is that I can either retard the intake to see what happens by reducing overlap that way, or maybe it will require a different sort of strategy with advancing both intake and exhaust at higher RPM. I was reading more on it at the link below which I thought was helpful in providing a better understanding of cam timing in general.

https://www.hamotorsports.com/pages/cam-gear-tuning-tuning-advance-retard-and-overlap-for-power#:~:text=To%20increase%20overlap%2C%20you%20have,and%2For%20RETARD%20the%20INTAKE.&text=In%20a%20naturally%20aspirated%20engine,overlap%20is%20called%20%22scavenging%22

"To increase overlap, you have to RETARD the EXHAUST, and/or ADVANCE the INTAKE.
To reduce overlap, you have to ADVANCE the EXHAUST, and/or RETARD the INTAKE.

Simple cam tuning rules for NATURALLY ASPIRATED engines:

* Advancing both cams => more low-RPM power, less high-RPM power
* Retarding both cams => more high-RPM power, less low-RPM power
* Less overlap => more low-RPM power, less high-RPM power
* More overlap => more high-RPM power, less low-RPM power"

"Retarding overall cam timing: Retarding overall cam timing is better for high-RPM power. This is because the valves are closing later. The intake valve is closing AFTER the piston has started to travel back up the bore for the start of compression stroke. This is terrible at low RPM because the intake air velocity is low, and air that was once in the cylinder is now being pushed back into the intake manifold and causing turbulence.

At high-RPM, the rules change. Air has weight, and thanks to Sir Issac Newton, we know that once it is moving, it doesn’t want to stop moving. This means that the air can continue to flow into and fill the cylinder, EVEN AFTER the piston has begun to travel UP the cylinder bore. This can allow an engine to exceed 100% volumetric efficiency, if even by a small amount."

Prior SliM3 post:
"3) Here is the intake VANOS map. The cell values represent the changes in total camshaft spread based on crankshaft degrees (øKW), which is 60ø (70ø to 130øcr). By default the cam is advanced to 130øcr at start-up/idle; So if you wanted to know exactly where the lobe center-line is in relation to the crank, based on cell values, you first need to figure out the degree of retard (x = 60ø - cell value), easy enough. Then take that value an subtract it from the max adv angle (y = 130øcr - x)."

[SliM3]

If you limit Max Torque KF_MD_MAX_MD_IND_OPT
you will also limit HP.

That's only going to relate to torque interventions, not normal operating conditions.

I agree with BBR! Adjust power output via VANOS and the 23x14 Throttle Map (linearizes open-loop air mass flow control to account for the non-linearity of the throttle position to throttle area).

[Anri]

'been there and done that' too many times with s50's and s52's. I am choosing to run the s54 detuned as opposed to an overstressed s50 or s52 because the motor for a racecar is just better in every way from the factory.

Hi,

Oh absolutely...S52 is great engine for the street but for the Track I have never ever been fan of..... !!!!
its from the oil pan to the valve cover is not design to take the abuse we do at say Buttonwillow
I know few people who were having problems with S52 and after several attempts the final
destination is alway S54.

Interestingly how people think just because S52 is cheaper from the start it will remain
this way...at the end cost is equal or more than having 320rwhp std. S54.

At this moment I am not willing to let the cat go about the proper way to have de-tuned
S54 for specific class.

Regards,
Anri.

[BBRTuning]

BBRTuning - you mentioned decreasing overlap to reduce power. Did you mean to say increase overlap or have you found that at the higher RPM's you will see increased HP with more overlap (to a point) on the s54 due to scavenging?

On the S54 even at peak power ~8000 RPM they tend to like 10-25* advance on the inlet cam and -20-35* retard on the exhaust cam depending on cam spec and exhaust setup, so there's quite a lot of room to go to reduce overlap and VE/torque at whatever RPMs it's needed.

[JBAshland]

Hi,

Interestingly those with De-tuned S54s are not any faster than those with S52s-E36M3s
I know few cars which run same de-tuned S54 to be in the Class but they are ain't any faster...

This de-tuning is all done in a wrong way. One must have to take advantage from the better
platform which is the S54.

S54 is about 45-50 +/- heavier engine compare to S52 which sits in the worst area of the car.

Regards,
Anri

While not the topic of this thread, I can tell you that I went with the s54 platform for my series (ST4) not because I thought it would make me or the car faster, but because I have 'been there and done that' too many times with s50's and s52's. I am choosing to run the s54 detuned as opposed to an overstressed s50 or s52 because the motor for a racecar is just better in every way from the factory. Scaling the car, you can see a bit more weight on the front, so I add a bit more front spring, and make other adjustments as needed to get the car where you want it depending on driver, tire and track conditions. The e36/e46 as a whole is a pretty forgiving chassis - hence why you will see so many different kinds of setups from supposed 'track experts' that all seem to get the job done with wildly different spring rates/splits/front to rear bias, 'the best shocks from such and such premium vendor', blah blah blah. This isn't Formula 1.

That said, if you think the de-tuning is all done in the wrong way, can you tell us what is the right way and if you have any actual experience in doing so?

BBRTuning - you mentioned decreasing overlap to reduce power. Did you mean to say increase overlap or have you found that at the higher RPM's you will see increased HP with more overlap (to a point) on the s54 due to scavenging?

[Anri]

Hi,

Interestingly those with De-tuned S54s are not any faster than those with S52s-E36M3s
I know few cars which run same de-tuned S54 to be in the Class but they are ain't any faster...

This de-tuning is all done in a wrong way. One must have to take advantage from the better
platform which is the S54.

S54 is about 45-50 +/- heavier engine compare to S52 which sits in the worst area of the car.

Regards,
Anri

[eacmen]

... Then you just have to add a hidden switch to change maps when you're not going dyno'd.


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[JBAshland]

You're usually best off limiting power first by reducing cam overlap (Vanos maps) and then reduce throttle opening only if needed. Ignition timing should be tuned to MBT as normal. Reducing ignition timing to limit power is a bad idea and will create excessive EGTs and other reliability issues. This method will net you the best fuel economy especially if you're doing endurance racing. You can simply just limit throttle as well but this is less efficient than reducing cam overlap due to inlet pumping losses.

Very helpful BBRTuning - thank you for a pointer in the right direction at least. The way I see it is, limiting throttle is the quick and dirty method. Working with vanos timing to reduce overlap is likely the more difficult but better way to tune the motor more efficiently. I will start looking in that direction to at least learn more about it. What about the torque limiting tables - do you work with those at all? Thanks again.

[BBRTuning]

You're usually best off limiting power first by reducing cam overlap (Vanos maps) and then reduce throttle opening only if needed. Ignition timing should be tuned to MBT as normal. Reducing ignition timing to limit power is a bad idea and will create excessive EGTs and other reliability issues. This method will net you the best fuel economy especially if you're doing endurance racing. You can simply just limit throttle as well but this is less efficient than reducing cam overlap due to inlet pumping losses.