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      09-18-2019, 05:00 PM   #23
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Quote:
Originally Posted by tommytexter View Post
I assume M340i xdrive is going to less because of awd. Maybe 350~360hp at wheel.
Mission Performance recently did a dyno baseline for an M340i xdrive and I believe they were in the 335-345 range. Which is quite respectable. Kind of like the M240i (not surprising since same engine)
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      09-18-2019, 05:06 PM   #24
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Originally Posted by MartinS View Post
Why do people say the loss in % in the transmission?
15% on a 1000hp engine would be 150hp loss but only 15hp loss in a 100hp engine.

My M4 has about 64hp loss in the driveline. That would be 64hp loss nomatter how many hp it has, right?
These driveline loss estimates are nowhere near an exact science. The 15% number bandied about is actually not accurate. Different cars with different differentials, final drives, transmissions, transfer cases, wheels, etc. all will vary in how much loss they have. That's why when you see a tuner estimate the bhp "assuming" a 15% driveline loss, that is complete B.S.

The reason most just use percentages is because things like the differential, transmission, and the general durability/weight of these components are probably matched to the power output of the vehicle. A smaller car would have lighter components since heavier components would be unnecessary and slow the car down more.

Also, as engine power goes up, a lot of these loss forces are amplified which is why using a percentage is more appropriate than a fixed power figure. However, even this is not totally correct as these changes are not perfectly linear. So the loss is really dynamic and even depends on which gear you're in.
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      09-18-2019, 05:51 PM   #25
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      09-18-2019, 06:55 PM   #26
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Just curious, does anyone know if the B58 on the Z4 is the same as the Supra? The Supra community has unlocked a lot of HP and assuming they're the same then the numbers should be similar to the Supra.
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      09-18-2019, 08:44 PM   #27
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Quote:
Originally Posted by mecheng77 View Post
Why does Bmw consistently do this? Insurance, regulation, laws?
Do what ?

Folks need to get more familiar with power rating standards and the operation of modern turbocharged engines...
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      09-18-2019, 08:51 PM   #28
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Quote:
Originally Posted by MartinS View Post
Why do people say the loss in % in the transmission?
15% on a 1000hp engine would be 150hp loss but only 15hp loss in a 100hp engine.

My M4 has about 64hp loss in the driveline. That would be 64hp loss nomatter how many hp it has, right?
Drivetrain losses are a percentage and they actually increase with RPM (no, they do not increase linearly).

Look at a MAHA dyno graph, this brand of dyno does a good job of measuring losses and graphing them by RPM.
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      09-18-2019, 09:41 PM   #29
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Quote:
Originally Posted by goj View Post
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Originally Posted by sittingmongoose View Post
I wonder if bmw will detune these cars later on like they did the new 340 and the Supra?
What do you mean? Like early models have more HP than later ones?

You mean measured, not rated right?
The early releases of the car were full bore. They were Dynoed at far higher numbers. For the Supra, and m340i. Then they released a software update and it detuned the engine. Lost like 40hp at the wheels on the 340. Then another update dropped by like 20hp.

So the people getting 340s now are down like 60hp over the first releases(if they didn't get ecu updates). Or the car reviews that were early on were putting out far more power than they are now.

The upside is a tune will net A LOT.
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      09-18-2019, 09:43 PM   #30
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Quote:
Originally Posted by CanAutM3 View Post
Quote:
Originally Posted by mecheng77 View Post
Why does Bmw consistently do this? Insurance, regulation, laws?
Do what ?

Folks need to get more familiar with power rating standards and the operation of modern turbocharged engines...
They're underrated numbers from factory. Compare them with most other manufacturers and you'll see that. Ford RS makes almost 70hp less than it's advertised bhp. That's a huge number.
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      09-18-2019, 11:14 PM   #31
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      09-19-2019, 03:56 AM   #32
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Quote:
Originally Posted by sittingmongoose View Post
The early releases of the car were full bore. They were Dynoed at far higher numbers. For the Supra, and m340i. Then they released a software update and it detuned the engine. Lost like 40hp at the wheels on the 340. Then another update dropped by like 20hp.

So the people getting 340s now are down like 60hp over the first releases(if they didn't get ecu updates). Or the car reviews that were early on were putting out far more power than they are now.

The upside is a tune will net A LOT.
Is all of this based on just that one post by a vendor that is selling tunes? I'd take that with a pretty large grain of salt.
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      09-19-2019, 06:37 AM   #33
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Quote:
Originally Posted by tom @ eas View Post
Just wanted to share some baseline numbers for a new 2020 Z4 M40i on our dynojet. Peak numbers are 381/381, closely matching BMW's BHP ratings.

* Numbers are at the wheels, on 91 octane.






More to come..
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      09-19-2019, 06:39 AM   #34
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Quote:
Originally Posted by F30Allen View Post
Just curious, does anyone know if the B58 on the Z4 is the same as the Supra? The Supra community has unlocked a lot of HP and assuming they're the same then the numbers should be similar to the Supra.
B58 on Z4 2020 yes.
B58 from 2016-2019 is similar but not the same.
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      09-19-2019, 08:04 AM   #35
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Quote:
Originally Posted by low135 View Post
They're underrated numbers from factory. Compare them with most other manufacturers and you'll see that. Ford RS makes almost 70hp less than it's advertised bhp. That's a huge number.
No, they are not “underrated”. Engine ratings are highly regulated, car manufacturers cannot publish any numbers they want.

As I said, one needs to get familiar with the SAE and DIN engine power rating standards and understand the operation fundamentals of modern turbocharged engines to understand what is going on with the numbers.

In short, engines behave differently when in steady state (constant RPM) than when in transient state (while accelerating). Modern turbocharged engines usually tend to make more power in transient than in steady state in the mid to high RPM band while making less in the lower RPM.

Traditionally, power rating standards required the engine to be tested in steady state, which allows for much better control of the test environment for more accurate and repeatable results. The engine is held for a few minutes at a given RPM at WOT until all the parameters stabilize before the measurements are taken. The engine is then accelerated to the next RPM point and left to stabilize, and the process is repeated across the RPM range.

With the avenue of modern turbocharged engines, the SAE has modified the standards to allow manufacturers to take advantage of the engine characteristics and now allows them to test in transient if they so desire. The caveat is that they leave it up to the manufacturers to chose which of the two method they want to obtain their ratings, so it makes it difficult to compare numbers between manufacturers.

BMW and most European manufacturers choose to stick with the traditional steady state method for their ratings likely because it is more accurate and repeatable. This is why the numbers seem “underrated” when compared to numbers obtained on a chassis dyno that operates in transient state.

Excerpt from SAE standard J1349 section 9:
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      09-19-2019, 08:27 AM   #36
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Quote:
Originally Posted by CanAutM3 View Post
Quote:
Originally Posted by low135 View Post
They're underrated numbers from factory. Compare them with most other manufacturers and you'll see that. Ford RS makes almost 70hp less than it's advertised bhp. That's a huge number.
No, they are not "underrated". Engine ratings are highly regulated, car manufacturers cannot publish any numbers they want.

As I said, one needs to get familiar with the SAE and DIN engine power rating standards and understand the operation fundamentals of modern turbocharged engines to understand what is going on with the numbers.

In short, engines behave differently when in steady state (constant RPM) than when in transient state (while accelerating). Modern turbocharged engines usually tend to make more power in transient than in steady state in the mid to high RPM band while making less in the lower RPM.

Traditionally, power rating standards required the engine to be tested in steady state, which allows for much better control of the test environment for more accurate and repeatable results. The engine is held for a few minutes at a given RPM at WOT until all the parameters stabilize before the measurements are taken. The engine is then accelerated to the next RPM point and the process is repeated across the RPM range.

With the avenue of modern turbocharged engines, the SAE has modified the standards to allow manufacturers to take advantage of the engine characteristics and now allows them to test in transient if they so desire. The caveat is that they leave it up to the manufacturers to chose which of the two method they want to obtain their ratings, so it makes it difficult to compare numbers between manufacturers.

BMW and most European manufacturers choose to stick with the traditional steady state method for their ratings likely because it is more accurate and repeatable. This is why the numbers seem "underrated" when compared to numbers obtained on a chassis dyno that operates in transient state.
That's interesting.
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      09-19-2019, 08:51 AM   #37
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Quote:
Originally Posted by CanAutM3 View Post
Quote:
Originally Posted by mecheng77 View Post
Why does Bmw consistently do this? Insurance, regulation, laws?
Do what ?

Folks need to get more familiar with power rating standards and the operation of modern turbocharged engines...
Quote:
Originally Posted by CanAutM3 View Post
Quote:
Originally Posted by mecheng77 View Post
Why does Bmw consistently do this? Insurance, regulation, laws?
Do what ?

Folks need to get more familiar with power rating standards and the operation of modern turbocharged engines...
Underrate the power? Or is there an SAE standard that rates the power will full accessories on driving on a hot day?

Why the discrepancy?
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      09-19-2019, 09:07 AM   #38
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Quote:
Originally Posted by mecheng77 View Post
Underrate the power? Or is there an SAE standard that rates the power will full accessories on driving on a hot day?

Why the discrepancy?
Read two posts above
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      09-19-2019, 09:32 AM   #39
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Quote:
Originally Posted by MartinS View Post
Quote:
Originally Posted by DPelletier View Post
Quote:
Originally Posted by gheumann View Post
You're measuring at the rear wheels, yes? Then I'd say they're better than BMWs numbers which are presumably just the engine?
Yep, I assumed that's what he was trying to say?...... 15% driveline loss would put it at around 448hp net flywheel and 10% would put it at 424hp net flywheel. Good numbers in any case. :-)

Funny thing was when I first test drove an M40i and was worried about the power compared to my V8 Ftype, the sales manager said that BMW typically underrates their engines and that the net flywheel rating would be what I could expect at the rear wheels.....guess he was right on the money. Car certainly felt faster than I expected though the 400lb weight advantage vs. my F type was responsible for some of that...

Dave
Why do people say the loss in % in the transmission?
15% on a 1000hp engine would be 150hp loss but only 15hp loss in a 100hp engine.

My M4 has about 64hp loss in the driveline. That would be 64hp loss nomatter how many hp it has, right?
Based on your car 'always' having a 64hp loss. If your car had 50hp and you have a 64hp loss, your example would mean your car has -14hp. The power loss from wheel to crank is a percentage of the total, and changes relative to the increase or decrease in power, it's not a static number.
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      09-19-2019, 09:35 AM   #40
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Quote:
Originally Posted by helloelectro View Post
Quote:
Originally Posted by MartinS View Post
Quote:
Originally Posted by DPelletier View Post
Quote:
Originally Posted by gheumann View Post
You're measuring at the rear wheels, yes? Then I'd say they're better than BMWs numbers which are presumably just the engine?
Yep, I assumed that's what he was trying to say?...... 15% driveline loss would put it at around 448hp net flywheel and 10% would put it at 424hp net flywheel. Good numbers in any case. :-)

Funny thing was when I first test drove an M40i and was worried about the power compared to my V8 Ftype, the sales manager said that BMW typically underrates their engines and that the net flywheel rating would be what I could expect at the rear wheels.....guess he was right on the money. Car certainly felt faster than I expected though the 400lb weight advantage vs. my F type was responsible for some of that...

Dave
Why do people say the loss in % in the transmission?
15% on a 1000hp engine would be 150hp loss but only 15hp loss in a 100hp engine.

My M4 has about 64hp loss in the driveline. That would be 64hp loss nomatter how many hp it has, right?
Based on your car 'always' having a 64hp loss. If your car had 50hp and you have a 64hp loss, your example would mean your car has -14hp. The power loss from wheel to crank is a percentage of the total, and changes relative to the increase or decrease in power, it's not a static number.
What I mean is that I know it has a 64hp loss. So if I put pure turbos on and get, let's say 250hp more, then I still have a 64hp loss... or?
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      09-19-2019, 09:44 AM   #41
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Quote:
Originally Posted by MartinS View Post
Quote:
Originally Posted by helloelectro View Post
Quote:
Originally Posted by MartinS View Post
Quote:
Originally Posted by DPelletier View Post
Quote:
Originally Posted by gheumann View Post
You're measuring at the rear wheels, yes? Then I'd say they're better than BMWs numbers which are presumably just the engine?
Yep, I assumed that's what he was trying to say?...... 15% driveline loss would put it at around 448hp net flywheel and 10% would put it at 424hp net flywheel. Good numbers in any case. :-)

Funny thing was when I first test drove an M40i and was worried about the power compared to my V8 Ftype, the sales manager said that BMW typically underrates their engines and that the net flywheel rating would be what I could expect at the rear wheels.....guess he was right on the money. Car certainly felt faster than I expected though the 400lb weight advantage vs. my F type was responsible for some of that...

Dave
Why do people say the loss in % in the transmission?
15% on a 1000hp engine would be 150hp loss but only 15hp loss in a 100hp engine.

My M4 has about 64hp loss in the driveline. That would be 64hp loss nomatter how many hp it has, right?
Based on your car 'always' having a 64hp loss. If your car had 50hp and you have a 64hp loss, your example would mean your car has -14hp. The power loss from wheel to crank is a percentage of the total, and changes relative to the increase or decrease in power, it's not a static number.
What I mean is that I know it has a 64hp loss. So if I put pure turbos on and get, let's say 250hp more, then I still have a 64hp loss... or?
No. It's a percentage of your total. Also, your loss is at the wheels (whp) not at crank(flywheel/bhp)

75whp = 100 at crank

This is a soft figure of difference btw. It's what most people use to assume crank power when seeing wheel power.

The 64 hp loss you are noting was derived from a % factor. It will change with the gains/loss in hp.

200hp at wheels =~ 230hp at crank = 30hp difference
400hp at wheels =~ 460 at crank = 60hp difference.

Again, this is fuzzy logic that just makes it easy to assume crank hp. But it typically amounts to 15% difference.
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      09-19-2019, 10:19 AM   #42
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wow... these numbers are quite impressive, especially for a "Non M" car... isnt this more power than the OG M2 when it was first released? Idk why they still have a ZF 8 speed in this if im not mistaken,
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      09-19-2019, 11:03 AM   #43
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Quote:
Originally Posted by helloelectro View Post
It's a percentage of your total.
Well, actually it is not.

There are many different components to drivetrain loss that individually vary to different degrees with load and road speed. So even a blanket percentage is a false assumption.

It is just better to leave the whp numbers as they are and avoid trying to speculate crank power from them.
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      09-19-2019, 11:06 AM   #44
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Quote:
Originally Posted by CanAutM3 View Post
Quote:
Originally Posted by helloelectro View Post
It's a percentage of your total.
Well, actually it is not.

There are many different components to drivetrain loss that individually vary to a different degree to road speed. So even a blanket percentage is a false assumption.

It is just better to leave the whp numbers as they are avoid trying to speculate crank power from them.
Correct, which I explain that it's not accurate it's just what is typically used when looking at whp as a soft logic approach.

Lots of factors play in from humidity, altitude, the dyno itself and the list goes on.
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