Dyno results S38B38: how to improve S38 max power, cruise, fuel economy

daytonaM5 · Jun 5, 2008

As the owner of a 3.8L and a Dyno Dyanmics Chasis Dyno, I would like to post my dyno results, talk about it, and if you have your own dyno results, post them, we can see what goes wrong, what can be done to improve performance.<O

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All power numbers are WHEEL HP. <O

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The run was made @ Shootout mode, meaning that NO correction factor can be dialed. `As it is mode`.<O

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Just look at the right axle of the graph, and see that the air fuel ratios are between 10,8 to 12. <O

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Note that the intake temps are 41 celcius degrees, it was a hot summer day. Power results would be slightly better on a cooler day. As we see, the detailed dyno page shows intake temperatures, and air fuel ratios, and vacuum for all reference engine speeds.<O

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The vacuum column, far right column, indicates that the vacuum is increasing with the increasing revs. IDEALLY vacuum should be ZERO inches of mercury, if the intake system was ideal. On S38B38, at least on my M5, vacuum has increased to <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com

1,0 inches</st1:metricconverter> of mercury from <st1:metricconverter w:st="on" ProductID="0,1 inches">0,1 inches</st1:metricconverter> of mercury. This shows that OEM M5 intake is restrictive. Once again, on an ideal engine, these vacuum readings should be close to ZERO at full throttle.<O

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By looking at the vacuum readings, S38B38 can make more power, if the intake system can be improved. It is very tough to improve the intake of S38, but can be done. <O

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Max power is attained at 12,8:1 air fuel ratios. This means, leaning the fuel will add more power.<O

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Power dips from 5500 rpm up to 6000 rpm, due to overfueling. Now, a ready on the shelf cannot cure this. This M5 needs to be custom tuned on the rolling road. <O

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The cats were on, stock muffler was on, stock air filter was on during this power run.<O

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Now, I have started a turbo project, and did not work on the software. But if I would change only the fuelling part, it would add approx 30 whp. <O

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Other than reprogramming fuelling, ignition maps can be tuned to add more power, this entails high octane fuel. We can go into the igniton in the coming posts.
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Post yours and we talk about them, this is basically what chip tuning is.<O

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By the way, I am about to get the maps of the S38 software, so that I can edit the maps with the proper software, load it.<O

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I am trying to point out that any ready on the shelf chip, wont work well. All M5 or all automobiles must be custom programmed on a rolling road.

Cyrus · Jun 11, 2008

WMWM...

That is surprising!

I would have thought the S38 would have been louder than an S14 with an airbox.

The dyno figures are not so impressive given the amount of work done though.

I have seen +10 BHP from a quick tune on an S38 with just some changes to the ignition map.

My little carbon intake muffler is effing loud and gains 3 bhp.

There may well be loads more power to come from you engine with that airbox though. Have you kept the MAF?
If not, how has the ECU been configured to run without one?

Schrick cams - join the club, I want a set too but I have concerns about future valve clearance adjustment problems they cause.

WMWNWMN · Jun 12, 2008

There are bigger gaps in time between when a value opens on the s14, so u can hear the engine gulp more than on s38. I think its louder than a csl, which is cool, but definetly not louder than a built s14. i never saw the dyno plot, but the car is definetly more fun 2 drive with the box. I should have more pics after this weekend once i get the brakes sorted...

nebpor · Jun 12, 2008

You're once again focussing on peak power gains - it's the rest of the curve that affects the real world - what is the difference in overall area apart from the 10BHP at peak? :hihi:

For the record I'd love a carbon airbox, with some mad cams and standalone ECU, but it's easier (although almost as expensive) to do this on my Honda so I do it there instead!

Lantz · Jun 12, 2008

And if you can please post a video, you car is sick and you have the best colour

Lantz

DiegoR · Apr 23, 2011

Hello,

I would like to get a performance chip, I might need to source one from europe, but I'm not sure which is a proven chip, I just want the engine more happy overall and I'm not looking for the last drop of power.

In the other hand, how exactly does work the resonance flap in the intake box? And what's the porpouse of it? It acts just for the noise of the engine breathing at high RPM's or it does work like a variable intake runner to gain lower end torque? Also, someone said you check if it's really working if you rev up the engine past 4K rpm while the hood is open to let you watch it of corse and other says no matter what you do it won't actuate until you put "some load" i.e. drive the car?

Finally, which doesn't have to do anything with this thread, what does the "air pump" these engines has? Create some kind of pressure or just vaccum? What's the porpouse? I hear it being activated every time I start the engine when is cold.

Thanks

mottati · Apr 23, 2011

DiegoR said:
In the other hand, how exactly does work the resonance flap in the intake box? And what's the porpouse of it? It acts just for the noise of the engine breathing at high RPM's or it does work like a variable intake runner to gain lower end torque? Also, someone said you check if it's really working if you rev up the engine past 4K rpm while the hood is open to let you watch it of corse and other says no matter what you do it won't actuate until you put "some load" i.e. drive the car?

Finally, which doesn't have to do anything with this thread, what does the "air pump" these engines has? Create some kind of pressure or just vaccum? What's the porpouse? I hear it being activated every time I start the engine when is cold.

Thanks

the air pump is an emissions control device. It pumps air into the exhaust during a cold start, combined with the rich cold start mixture, this gets the catalyst up to temp more quickly.

The resonance flap enhances mid range torque, on a 3.8, there is no observable self test (a 3.6 runs a test procedure on each cold star, so you can see that it functions). There are threads about how it works and what controls it. In short, to test it, smear a dab of grease on the 'stop' go out for a WOT run and see if you see a mark in the grease where the little cam hit the stop. Not sure if it will do it's thing just revving without load and the hood up. I believe there is a thread about this with pictures if you run a 'resonance flap' search.

Dyno results S38B38: how to improve S38 max power, cruise, fuel economy

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