75% Solution

[StickMon]

With all of the tuning and reprogramming that's been done, has anyone considered or tried to eliminate the 75% throttle restriction at lower RPMs?

I wonder if it's possible and what would be the effect.
Maybe just clouds of tire smoke and bent rods?

My car's a DD with 88k on it. Hope to break 200k.
I shift at 4200 when I'm just toodlin' along, and 5200 when I'm jumping on the freeway. It's been in the high 6000's a few times, but then I wake up in the middle of the night with nightmares of rod bearing failure.

Since I've owned the car, I think I hit 76% throttle once or twice, but that may have been a rounding error.

I feel gypped.

[Finnegan]

Here's a topic I'm not up on. So you've data logged the throttle mapping and a low RPM it's limited to 75%?

More please.

[StickMon]

When I started using DashCommend, once during WOT I saw 75% on the throttle position out of the corner of my eye.
Not wanting to stare at the iPod while WOT, I added a peak hold feature.
Sure enough; 75% at WOT. Thought maybe I had fallen back to some limp mode.

Did a Google, and found this.

often referred to as "torque limiter."

but I like torque

[XMetal]

Hmmm...so that explains the slight kick that I feel starting at around 4K. Very interesting find

[ZStig]

very interesting. Wonder if it can be programmed by gear

[yousefnjr]

Good find, I didn't know that. I guess the moral of the story is stay above 5k

[Finnegan]

Great find! I love learning new things!

From that other thread one might conclude that we aren't "missing" anything, but that opening 100% below 4k+ isn't optimal for a bunch of other reasons, and might net less, not more power in a non-turbo car or centrifugal S/C car.

Moral, as others have said, is to be in the "right" rev range to get max power.

Stick, if you're worried about rod bearing get a UOA done. Assuming its fine don't be afraid the hit the redline now and then. If that worries you, pretend it's 7.5k or 7k. You're leaving a ton of power on the table shifting at 6k.

[bignosejim]

WHS, be gentle until it is properly warmed up (I use about 10 o'clock on oil temp) then have fun. Before that I try to shift at 4000 rpm. Then I'll have fun and rev to around 7500 rpm a couple of times on my way to work. I have some stoplights on a 65 mph road going to work.

[StickMon]

Got my Blackstone kit, and will be sending in a sample of my next change.
At my last change, when I was pouring the used oil out of the catch pan into containers, found metal sparkles in the sludge at the bottom.
I don't think (well I hope) it wasn't from the Z.
Can't remember when I bought the catch pan, but I'm pretty sure I've used it on at least 6 cars. Threw it out and got a new one.
I think the metal flakes were probably from the magical mystery Camry that my Daughter drove 70 miles with no oil.
(Don't send a pretty teenager to Jiffy Lube. They were so busy flirting with her they forgot to refill the oil.)

[StickMon]

Back on topic.
Yea, I think BMW probably knows a thing or two and we aren't missing anything.
My Toyota had a dual ported intake manifold, where one set of ports was closed at low RPM.
They determined that less mass but higher velocity gave more torque below 4K.

That was before the days of fly-by-wire throttle, so maybe BMW accomplishes something similar though throttle control.

[Z4inAZ]

Originally Posted by StickMon

Back on topic.
Yea, I think BMW probably knows a thing or two and we aren't missing anything.
My Toyota had a dual ported intake manifold, where one set of ports was closed at low RPM.
They determined that less mass but higher velocity gave more torque below 4K.

That was before the days of fly-by-wire throttle, so maybe BMW accomplishes something similar though throttle control.

A two-port system is designed to allow optimum intake configuration for torque and HP.

The throttle restriction is designed strictly to limit down-low throttle. So the two systems have completely opposite design goals in mind. Dual-ports maximize torque (and HP), the throttle limiting limits torque.

[StickMon]

I though of that as I was writing it. Hence it's being referred to as "the torque limiter".
Which brings me back to my original musing.
Hmmm ... what if ...

[Z4inAZ]

As I recall there are some people trying to DIY tune this generation of BMW ECUs, perhaps asking around here may help.

Also just a little sidenote, the dual intake port technology is not an outdated design, it is still used with modern engines. BMW engines used it first on the M42 and M44 4 cylinders, and then later on the M54 and N52 6-cylinders that power many of these Z4's

[Shipkiller]

I would not as of yet, take this 75% rule as gospel. There is no hard data from BMW or any other tuners that talk about this. Or at least any that I can find.

Although, it most likely is a good call, just something we all never knew.

Also, the 'kick in the butt' we feel, which really starts about 3850 RPM, could also be (and most likely is) the VANOs doing it's thing.. something to keep in mind.

[Shipkiller]

Originally Posted by Z4inAZ

As I recall there are some people trying to DIY tune this generation of BMW ECUs, perhaps asking around here may help.

Also just a little sidenote, the dual intake port technology is not an outdated design, it is still used with modern engines. BMW engines used it first on the M42 and M44 4 cylinders, and then later on the M54 and N52 6-cylinders that power many of these Z4's

Wrong ECU. The S54 in the Z4 uses the MSS70. E46M3 uses an older ECU.

[Kgolf31]

Originally Posted by Shipkiller

I would not as of yet, take this 75% rule as gospel. There is no hard data from BMW or any other tuners that talk about this. Or at least any that I can find.

Although, it most likely is a good call, just something we all never knew.

Also, the 'kick in the butt' we feel, which really starts about 3850 RPM, could also be (and most likely is) the VANOs doing it's thing.. something to keep in mind.

This is what I'm thinking.

Don't forget, we have a dual-mass flywheel and all as well. It takes time to spin up

[StickMon]

Originally Posted by Shipkiller

I would not as of yet, take this 75% rule as gospel.

Somebody want to double check it with a P3 Gauge?
It should be able to read TPS.

[Shipkiller]

You can do it with INPA and a laptop.

[marinb]

I agree, people with P3Gauges can check this easily, and do peak recall. I don't have my gauge any more but I do remember finding it odd that I wasn't seeing numbers closer to 100%

[seank]

My p3 run 74-75 on my pull from 4000-6000. I don't if it is different at wot while above 5000 rpm's.

Btw the torque and hp cross at 5250 which may be what everyone is talking about with the extra power.

[StickMon]

Beats me.
I'm used to having a mechanical cable between the loud pedal and the throttle.
Somewhere not quite to the floor the throttle is 100% open.
Was surprised to see only 75%.

On the subject of leaving power on the table, I want this knob on my dash, or maybe my steering wheel:

[seank]

Originally Posted by seank

My p3 run 74-75 on my pull from 4000-6000. I don't if it is different at wot while above 5000 rpm's.

Btw the torque and hp cross at 5250 which may be what everyone is talking about with the extra power.

To redline, it still show 75.