2012 Z4 sDrive28i Dyno video

[totoro]

[SliverBullet]

Originally Posted by totoro

Those numbers... those are at the wheel I assume. Soooo isnt that not far from what the 35i is putting out at the wheels (300 HP, 300 TQ is at the crank). Are we getting gipped?

[BlueZ4AZ]

Originally Posted by SliverBullet

Those numbers... those are at the wheel I assume. Soooo isnt that not far from what the 35i is putting out at the wheels (300 HP, 300 TQ is at the crank). Are we getting gipped?

No.

The 300HP/300TQ for the 35i are underestimated by BMW to begin with. The 35i already been dynod. Crank HP is estimated at 332. TQ at 332....and it's been posted in this forum.

The 35is HP and TQ are higher than what BMW claim too.

So, no need to worry where the 28i is dynod.

[totoro]

Originally Posted by SliverBullet

Those numbers... those are at the wheel I assume.

Yeah their numbers are at the wheel.
So if there is around 10-15% loss, this engine has more like 256-268hp??

[teagueAMX]

Did anyone notice if they had an air fans facing the radiator? BMWs are sensitive to air temps and engine temps and will retard the power curve if almost freeway-like air flow conditions are not met at the simulated speed.

Here's quote from Dinan's website:

Dynamometer Testing and The Modern BMW Engine

. . .By far the most significant criticism I have for many dyno facilities is the use of fans that are simply too small for the job at hand. The fan size is so significant that we employ a very large unit that was actually designed for ventilation systems installed in high rise buildings! This powerful fan produces 38,000 cfm of air flow @ 75 MPH, which is still less than the 150 MPH air that a modern BMW might see at redline in 5th gear, but it certainly provides a closer to real-world scenario than the more common fans I have seen used in dyno facilities. It should be noted that 5th gear is used for our dyno testing because it is one to one, meaning that the input and output shafts are connected, reducing power losses and transmission wear. I have seen many examples of dyno facilities where low flow fans obtained from the local hardware store are employed, and even situations where there was no fan at all. A minimum of 15,000 cfm and preferably 40,000 cfm of air flow is required for proper heat exchanging. This type of fan will produce a 40-80 mph air discharge velocity.

A lack of air-flow during dyno testing will almost always alter the fuel mixture in the rich direction as the radiator cannot exchange enough heat, resulting in the computer compensating by retarding timing and richening the fuel mixture to prevent the engine from overheating and detonating. In addition, the intake air sensor will read substantially higher temperatures than that seen on the road with proper airflow. This issue is particularly important to address when testing high output cars like the M5 or M3, and even more so on forced induction cars with intercoolers as the heat exchanger is not able to cool as efficiently because of the reduced air flow. The engine compartment is normally flushed with air driving down the road, particularly at speed, cooling the manifolds and other associated engine components. Cooler engine components and lower air intake temperatures will result in a leaner air/fuel mixture and ignition timing will be advanced, invariably resulting in greater power on the road than on the dyno. In simpler terms, accurate measurements can only be achieved when the dyno tests are conducted in a manner that simulates the car driving down the road, in as much as is possible. . .

[BlueZ4AZ]

Originally Posted by totoro

Yeah their numbers are at the wheel.
So if there is around 10-15% loss, this engine has more like 256-268hp??

It seems BMW underestimated the HP on the 28i as well.
All 3 engines are getting way more HP to the wheel than would be expected, given the crank HP BMW claims the engine has.

[Ateam]

This is way more to the wheels than even the n52 255hp version put down. Seems this little 4 banger is very strong.

What I do not get is why no NA I6 engine was ever under rated by bmw and they always dyno low if anything. yet every TT engine they put out seems to be way under rated.

[BlueZ4AZ]

Originally Posted by Ateam

This is way more to the wheels than even the n52 255hp version put down. Seems this little 4 banger is very strong.

What I do not get is why no NA I6 engine was ever under rated by bmw and they always dyno low if anything. yet every TT engine they put out seems to be way under rated.

If you happen to dig up anything by Googling that fact, let us know. Thanks.

[ATX78703]

Man, I was just looking up the specs on the N20 vs. N55 on bmwusa's website. for 7K less, you get a vehicle that is only 0.5 sec slower to 60 and likely gets 3-4 better mpg and carries less weight over the front axle. Not to mention u can get the exact same sport/msport pkg it prob handles slightly better.

[ATX78703]

the n55 is in desperate need of an upgrade to 320-330 hp/325 lb ft now not only to compete with audi's 3.0SC, but its own N20! and none of this performance pack BS.

Maybe they're waiting to debut the new V6 block on the f80 m3 and they'll come out with a detuned single twin-scroll set up for the _35i models.

[BlueZ4AZ]

Originally Posted by ATX78703

Man, I was just looking up the specs on the N20 vs. N55 on bmwusa's website. for 7K less, you get a vehicle that is only 0.5 sec slower to 60 and likely gets 3-4 better mpg and carries less weight over the front axle. Not to mention u can get the exact same sport/msport pkg it prob handles slightly better.

It's a matter of perspective. For only $7k more you can get a much faster car that gets only 3 miles less per gallon.

[BlueZ4AZ]

Originally Posted by ATX78703

the n55 is in desperate need of an upgrade to 320-330 hp/325 lb ft now not only to compete with audi's 3.0SC, but its own N20! and none of this performance pack BS.

Maybe they're waiting to debut the new V6 block on the f80 m3 and they'll come out with a detuned single twin-scroll set up for the _35i models.

Much like the N54, the N55 HP rating of 300 is most likely well underrated by BMW. We'll have to see some dyno results on the N55 to confirm.

If BMW was worried about 4 cylinder Z4 sales cannibalizing Twin Turbo sales, they probably never would have put a 4 banger in the Z4. The performance gap is plenty wide enough for the 4 cylinder not to impose any kind of threat.

There will still be an ample number of people that will prioritize performance and select the N55 Turbo.

[ATX78703]

Originally Posted by BlueZ4AZ

Much like the N54, the N55 HP rating of 300 is most likely well underrated by BMW. We'll have to see some dyno results on the N55 to confirm.

If BMW was worried about 4 cylinder Z4 sales cannibalizing Twin Turbo sales, they probably never would have put a 4 banger in the Z4. The performance gap is plenty wide enough for the 4 cylinder not to impose any kind of threat.

There will still be an ample number of people that will prioritize performance and select the Turbo.

doubt it..
it's a matter of opinion of course, until sales numbers come out. if you're truly going performance it's 35is all the way; the specs comparison between a n55 and n20 powered z4 is not, say, as big a difference as an s5 3.0sc vs a5 2.0t

[BlueZ4AZ]

Originally Posted by ATX78703

doubt it..
it's a matter of opinion of course, until sales numbers come out. if you're truly going performance it's 35is all the way; the specs comparison between a n55 and n20 powered z4 is not, say, as big a difference as an s5 3.0sc vs a5 2.0t

Buyers will base it on facts and seat of their pants feeling during test drives. The performance oriented buyers in general will want either the 35i or 35is.

ie. If you go test drive a 2 ton Infiniti G Convertible, then compare it to both a 35i and 35is, then the very fine line where "true" performance begins and ends becomes even blurrier. We had a G Convertible as a loaner last week while our EX35 was in for service. What a boat!!!!

I'd have to slide this hypothetical fine line separating the "true" performance convertibles/roadster, from smack in between the 35i and 35is, to down below the 35i, and definitely somewhere between the 35i and the Infiniti G. Exactly where the line falls, with there being numerous other makes and models of convertibles on the market, I am not in any position to determine myself, nor is anyone else, since we've not test driven every make and model out there.

Based on where the N54 engine Dynod, the majority consider a huge HP difference between the N54 in both 35i/35is and the 28i. A 60 - 95 HP difference in this HP range is significant. Unless the N55 is dynod and it's true HP at the crank is estimated at "only" 300, there will continue to be a signifigant power gap.

The majority will agree that we are just not at a stage where people are going to select the 4 cylinder as their "performance" choice.

The sales numbers alone are not going to tell the whole story. Basic economics says that more of the less expensive model (28i) will sell.