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Discussion Starter · #1 · (Edited)
COMMENT 10/03/2011 : THIS DYNO TEST IS NOT ADAPTED TO THIS CAR WHICH REQUIRES DYNAMIC AIRFLOW (see explanation on page 2). THE RESULTS SHOWN BELOW ARE NOT RELIABLE. I WASTED MY TIME AND MONEY . I KEEP THIS POST ALIVE SO THAT YOU DON'T WASTE YOURS.


Yesterday my car passed the dyno test.

Results are the rear wheel were:

327 hp @ 4980 rpm
532 nm @ 3750 rpm

They said their system can measure the drivetrain losses, by measuring the braking factor on the rolls, in deceleration phase.

This led to

50 hp loss at the peak power rotation,thus 377 hp at the crank
55 nm loss at the peak torque rotation, thus 588 nm at the crank

I'm puzzled by these results, because:
power at the crank is deceptive (lower than 400 announced by Alpina, first time I have lower results than what Alpina had announced)
power curve gets its peak before 5000 rpm and then starts decreasing
torque is humoungous but again too early in the curve
drivetrain losses ratio seems very low (13,2 %) taking account it's an automatic-converter gearbox.

I must say it's in total contradiction with feelings (the car is getting an extra-humph beyond 5000 rpm, which the B3 did not have) and with the comparison with my B10 biturbo (377 hp at the crank but 22% drivetrain loss, measured on the same bench) which, in real life, can not play in the same league as the B3S. On 0-200 km/h,the B10 is in the 19 sec range, whereas the B3S is in the 16 sec range. You need a lot more power to achieve this (same weight for both cars).

One cause we discussed with the manager, is that the air inflow might not be sufficient to feed up the turbos, especially after 4000 rpm. But he disregarded this possibility, arguing that his system can produce up to 22,000 m3/hour, and that should be sufficient. Still, with the Alpina Airbox developed by Alpina for the b3S, which contains a vortex system, it might be that this engine is sucking so much air at high rotations, that the fan was insufficient (or not well placed, or not fast enough). I want to further investigate .

It is noticeable that ,calculated with a drivetrainloss of 18 % (which seems a common ration for modern automatic BMW's) , the power at the crank becomes ... 399 hp ! (and 409 with a 20 % ratio).

I dropped a mailto Alpina with the detailed results and graphs,asking for comments.

I will keep you posted. If you have thoughts, happy to hear about, as this ruined my day yesterday :dunno:
 

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That correction factor for the automatic is indeed lower than I have ever seen. It's mostly 20% or so as far as I've read so far (tens of comments on Automatics and drive train losses). You may be right there.
No need to worry. As far as I'm concerned do this test: take a VBox and do a 0-200 KM/h test. If it's around 16s range, then it's got the power. You car is a convertible, so it should have around the same times as the M3 Convertible (17.3s to 200 is the best time I've found for the M3 Convertible). If you're around the 17s mark then you're as good as Alpina stated. If faster...:).
 

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Sherlock,

Is the results really that strange? Your new biturbo put out 325 hp on the wheels and your old biturbo put out 294 hp on the wheels (calculated from the information of a 22 percent drivetrain loss) - same bench. This means that the new biturbo produces a little more than 30 hp more than the old biturbo). It is probably those phonies that you feel when you say that the new car is faster. In fact, it should be given that is stronger, as measured in the bench - on the wheels where it counts -, and lighter,).

/Magnus
 

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Interesting! The drivetrain loss seems way too low for an automatic - around 18% sounds much more realistic.

Do you have a scan available of the dynosheet?
 

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The power curve matches nicely with the official Alpina graph for the B3S BiTurbo, however the torque curve falls off much earlier...
 

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Discussion Starter · #7 ·
Kees, I don't think the power curve matches either.

Anyway I got an Alpina engineer on the line right away. The curves do not make sense to them : too much torque, not enough power, decreasing reapidly after 4500 rpm. He said if this would be the case, I would noticeably feel it behind the steering wheel, in real conditions.
Verbatim : "apparently the engine switched the turbos in safe mode around 4000 rpm. This is probably due to excess of heating, and /or lack of fresh air intake detected. This dyno is not adapted to the air flow needed to feed the B3S engine".

Yesterday morning a chronometered a run from 0-100 km/h : 10,9 sec, with a very strong pull up to 6800 rpm.
The Alpina guy told me this would not be achievable with decreasing curves like on the dyno graphs.

Conclusion: I wasted 75 € on this dyno.
 

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What other cars hwere tested on this dyno earlier and the same day? Stock car that is?

I would say get a Vbox and get some times. That is a good indication vs other cars, esp. rolling starts and 0-200 km/h tests.
 

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0 - 160 KM/h in 10.9s is consistent with the best time I've found for an M3 Convertible (10.7s), so that dyno is probably malfunctioning.

You can compare your car's performance with these times:

0 - 100 kph 4.9 s
0 - 200 kph 17.3 s
0 - 100 mph 10.7 s
1/4 mile 13.1 s
0 - 100 - 0 mph 16.6 s

If your times closely match or better these then you have "the other M3" as I like to call the B3 S.
 

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Yesterday my car passed the dyno test.

Results are the rear wheel were:

327 hp @ 4980 rpm
532 nm @ 3750 rpm

They said their system can measure the drivetrain losses, by measuring the braking factor on the rolls, in deceleration phase.

This led to

50 hp loss at the peak power rotation,thus 377 hp at the crank
55 nm loss at the peak torque rotation, thus 588 nm at the crank

I'm puzzled by these results, because:
power at the crank is deceptive (lower than 400 announced by Alpina, first time I have lower results than what Alpina had announced)
power curve gets its peak before 5000 rpm and then starts decreasing
torque is humoungous but again too early in the curve
drivetrain losses ratio seems very low (13,2 %) taking account it's an automatic-converter gearbox.

I must say it's in total contradiction with feelings (the car is getting an extra-humph beyond 5000 rpm, which the B3 did not have) and with the comparison with my B10 biturbo (377 hp at the crank but 22% drivetrain loss, measured on the same bench) which, in real life, can not play in the same league as the B3S. On 0-200 km/h,the B10 is in the 19 sec range, whereas the B3S is in the 16 sec range. You need a lot more power to achieve this (same weight for both cars).

One cause we discussed with the manager, is that the air inflow might not be sufficient to feed up the turbos, especially after 4000 rpm. But he disregarded this possibility, arguing that his system can produce up to 22,000 m3/hour, and that should be sufficient. Still, with the Alpina Airbox developed by Alpina for the b3S, which contains a vortex system, it might be that this engine is sucking so much air at high rotations, that the fan was insufficient (or not well placed, or not fast enough). I want to further investigate .

It is noticeable that ,calculated with a drivetrainloss of 18 % (which seems a common ration for modern automatic BMW's) , the power at the crank becomes ... 399 hp ! (and 409 with a 20 % ratio).

I dropped a mailto Alpina with the detailed results and graphs,asking for comments.

I will keep you posted. If you have thoughts, happy to hear about, as this ruined my day yesterday :dunno:
Drivetrain loss is not a constant percentage. However, you can use 15% loss at the peak power as a close estimation. I believe the dyno operator could have printed you the drivetrain loss as a part of graph in case you were interested. The loss is quite linear to the speed, so it has a constant slope increasing to the right. Thinking of it, it is the higheset at the higheset speed, i.e. at 7000rpm, but at 7000rpm your power is down already, so the drivetrain loss there is humangous in percentage.

You have more power to the wheels (using the close 15% estimation by BMW) in B3 S compared to B10. In addition, the drag is lower because of better aerodynamics and slightly smaller frontal area. All in all you should have a noticeable difference in the performance for B3S's advantage.

The air flow in a dyno is way less than the air flow in driving. So although in theory the airflow could be enough for the engine, in practice your intercooler does not get the same blast of cool air through it and it heat soaks towards the higher revs. You should have really big blower in front of the car, and another small efficient one pointed at the intercooler in case you want to have even close estimations of the power in actual driving situation.

Also the air intake is designed in a way that the faster the car goes, the more there is pressure from the front of the car to the air box. The air box is filled with the air at a very high pressure. From there the air is directed to the turbos. The more there is pressure pushing the air towards the turbos, the easier is the work the turbos need to do themselves. Again, the actual air flow does not generate the pressure to the air box, and further to the turbos the same way as in driving.

Btw. do you know if the air inlet tubes from the air box happen to be the same as in stock 335i? I'd appreciate the knowledge. I'm looking into getting bigger diameter tubes to be able to feed more air to the turbos. Also, if you happen to open the airbox at some time, it would be interesting to see the design of it. Thanks!
 

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Discussion Starter · #14 · (Edited)
The air flow in a dyno is way less than the air flow in driving. So although in theory the airflow could be enough for the engine, in practice your intercooler does not get the same blast of cool air through it and it heat soaks towards the higher revs. You should have really big blower in front of the car, and another small efficient one pointed at the intercooler in case you want to have even close estimations of the power in actual driving situation.
You point it rightly so. I had a debriefing on this issue last week in Geneva with G. Schuster and A. Bovensiepen (they were informed about this test). The fact is that this dyno is not equiped to air feed this car as it should. The airflow should increase along with the engine rpm, it does not.
As a consequence, the engine is lacking air at a certain moment.
The test is not reliable. I wasted my time and money. End of this story.


Btw. do you know if the air inlet tubes from the air box happen to be the same as in stock 335i? I'd appreciate the knowledge. I'm looking into getting bigger diameter tubes to be able to feed more air to the turbos. Also, if you happen to open the airbox at some time, it would be interesting to see the design of it. Thanks!
Definitely different from the 335i and even from the B3 Biturbo (2007-2010).
Alpina people are not keen to provide detailed informations about their secrets, but this is what I learned:
1. The airbox includes (in the B3S) a "vortex" effect which further accelerates the fresh air towards the cylinders.
2. The filling up of the cylinders 1 and 6 has been improved, after Alpina noted these 2 extreme cylinders (to the block) where getting less air than the other cylinders. This "equalization" leads to an optimization of the combustion for all cylinders (delayed knocking, thus higher boost pressures admitted...).

Quote from A.Bovensiepen : "in essence, the way we got morepower on the B3S (+ 40 bhp) is pretty simple. We increased the airflow, both at admission and exhaust side. This allows to slightly increase the boost pressure, which in turn creates extra heat. The real key, in producing reliable high output engine (remember our cars must work in Middle East), is the cooling. Therefore the B3S has increased water and oil intercoolers and pumps".

Isn't it simple?
 

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Good and simple explanation.

Yes, decent airflow is always important, as for example Steve Dinan always have said.

Also, Andy told us (me and kees) in Geneva that upgrading a B3 BiTurbo to a B3 BiturboS isn't worth it: too many changes and it is better to buy a B3 S BiTurbo.

Quote from A.Bovensiepen : "in essence, the way we got morepower on the B3S (+ 40 bhp) is pretty simple. We increased the airflow, both at admission and exhaust side. This allows to slightly increase the boost pressure, which in turn creates extra heat. The real key, in producing reliable high output engine (remember our cars must work in Middle East), is the cooling. Therefore the B3S has increased water and oil intercoolers and pumps".

Isn't it simple?
 

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Also, Andy told us (me and kees) in Geneva that upgrading a B3 BiTurbo to a B3 BiturboS isn't worth it: too many changes and it is better to buy a B3 S BiTurbo.

You have just answered the question I was going to ask, re retro fitting to a B3

But, Andy would say that as they want to sell new ones, not upgrade used Alpina's ;)
 

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Yes, the more air flow through intake and exhaust, the more power.

However, I think Alpina marketing guys maight have been pulling you a bit. If in the intake they have changed only the air box, it would be easy swap for to get B3 to become B3S. The exhaust can be enhanced to flowing better by sport catalysators and increasing the diameter of it slightly and getting rid of the sharpest bends.

Vortex effect sounds marketing magic and if they have the stock 335i intake manifold, they are not really able to address the air flow allocation across the cylinders. Also if the inlet tubes from the air box to the turbos are stock 335i pieces, not much has been changed. Still the small changes are useful as e.g. the stock air box used by B3 is very restrictive and redesign has probably got rid of the sharp turns air must maneuver inside the stock (B3) air box. I'm sure the B3S air box flows a lot better (even though it would not have any vortex magic :) )
 

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The fact is a B3S is as fast as an M3, so no one should doubt the power.
I'm sure B3S is even faster. At low speeds B3S has a lot more torque and at the higher speeds the aerodynamics of B3S is so much better than M3 that the power being so close the aerodynamics makes Alpina faster.
 
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