[Crawlings]

Hey all, I have just finished searching through this forum for a thread related to exactly how the turbos on the 335i are set up and how they can produce no significant turbo lag, but to no avail.

Is there a thread or a website with an explanation somewhere that goes in to excrutiating detail on how these turbos on this particular vehicle are set up and what makes them so....juicy?

I'm an engineer by schoolin'(although electrical), so this kind of stuff gets me excited. I've wikipedia'd turbos in general, but it doesn't address specifically how these 335i turbos produce no lag...

Much appreciated.
Chad

[Ninjaneer]

This thread might help, some info scattered throughout:
Official: N54 engine with Bi-Turbo 306HP, 400Nm ...

[sstarch1]

They are small, and they are set up to only "power" 3 cyliners at once.

It does not require much flow to speed up the smaller turbine, thus turbo lag is reduced.

I dont really know what else there is to say.

[ksfrogman]

The link Ninjaneer gave is good. I just posted the N54 tech info in one place:

http://www.e90post.com/forums/showthread.php?t=38856

There are many factors that improve the throttle response and help to eliminate turbo lag. Perhaps the most important one is BMW's use of two small turbochargers in parallel. The smaller the turbocharger, the less energy it takes to spin the turbine. So it takes less time to spin and achieve the desired boost pressure. As a result of high rotational speed, the turbochargers get very hot. So BMW uses not only engine oil, but engine coolant to cool them down.

Another interesting technology is the use of direct injection, which helps cool down the cylinders during air/fuel induction, which allows the use of relatively higher compression ratios in a turbocharged car because of the increase in available oxygen. Said another way, the fuel is evaporated and atomized in the combustion chamber. This "cooling effect" allows an increase in air density; hence, more oxygen, which improves efficiency and engine power. It also means that there would be no condensation of fuel in the intake manifold, which would lead to inefficiency.

The throttle body assembly now uses a lighter plastic valve instead of an aluminum one with a much more sensitive actuator sensor to give the car's computer better input, and to improve responsiveness. Throttle valve position in addition to intake-air temp, engine speed, ambient pressure, intake-manifold pressure, and pressure before the throttle valve influence the N54's control over the engine's boost pressure.

[2007/335i/coupe]

I found this interesting about the 335d
http://www.caranddriver.com/features...-update-1.html

Originally Posted by CSABA CSERE @ Car & Driver

This is fundamentally the same engine as the 330d, except that it uses two turbochargers rather than one. Furthermore, the two turbos are staged, with the smaller one providing the boost at lower rpm, switching to the larger turbo at higher revs. Peak boost pressure is about 23 psi. For the Thunderhill race, BMW engineers have increased the boost pressure somewhat but, other than that, the engine is largely stock.

Wonder what the exact stock boost pressure is...

[ksfrogman]

Originally Posted by 2007/335i/coupe

I found this interesting about the 335d
http://www.caranddriver.com/features...-update-1.html



Wonder what the exact stock boost pressure is...

That particular 335d is turbocharged differently than our BMWNA 335i's are. Ours, or yours rather, uses two equally sized turbochargers--one for each of three cylinders. "Our" N54 has a "bi-turbo" setup as opposed to a twin sequential setup with turbos of different sizes.

[Crawlings]

Originally Posted by ksfrogman

Another interesting technology is the use of direct injection, which helps cool down the cylinders during air/fuel induction, which allows the use of relatively higher compression ratios in a turbocharged car because of the increase in available oxygen. Said another way, the fuel is evaporated and atomized in the combustion chamber. This "cooling effect" allows an increase in air density; hence, more oxygen, which improves efficiency and engine power. It also means that there would be no condensation of fuel in the intake manifold, which would lead to inefficiency.

I understand how cooler temps result in higher compression ratios, but how exactly does the direct injection garnish lower temps? When you say direct injection are you referring to Piezo-electric injection?


BTW, thanks for the info, that's exactly what I'm looking for.

[Boost335]

Originally Posted by sstarch1

They are small, and they are set up to only "power" 3 cyliners at once.

It does not require much flow to speed up the smaller turbine, thus turbo lag is reduced.

I dont really know what else there is to say.

Actually, they dont each power 3 cylinders, they are each powered by 3 cylinders, and then boosted gas is combined before it goes into the intake manifold.

[tintivilus]

Originally Posted by Crawlings

I understand how cooler temps result in higher compression ratios, but how exactly does the direct injection garnish lower temps?

Evaporative cooling? Does DI get more *liquid* gasoline into the cylinder than other methods?

[RiXst3r]

Originally Posted by tintivilus

Evaporative cooling? Does DI get more *liquid* gasoline into the cylinder than other methods?

The fuel/air mixture doesnt have a chance to heat up before it explodes in the chamber... cold fuel gets sprayed directly in...

[ksfrogman]

Originally Posted by Crawlings

I understand how cooler temps result in higher compression ratios, but how exactly does the direct injection garnish lower temps? When you say direct injection are you referring to Piezo-electric injection?


BTW, thanks for the info, that's exactly what I'm looking for.

Yes, this technology has been available for years, but was not practical due to the need for precise metering. BMW's first generation was introduced in 2003 with the N73 engine. Now BMW uses HPI or high precision injection using piezo injectors in its second generation of direct injection. Since high precision injection allows for more precise metering and directional control of atomized fuel, a higher compression ratio of 10.2 to 1 is possible. This sort of thing would have been unheard of in a turbocharged street engine years ago. The injected spray of fuel cools the air charge, and decreases the chance of detonation.

[2007/335i/coupe]

Originally Posted by ksfrogman

That particular 335d is turbocharged differently than our BMWNA 335i's are. Ours, or yours rather, uses two equally sized turbochargers--one for each of three cylinders. "Our" N54 has a "bi-turbo" setup as opposed to a twin sequential setup with turbos of different sizes.

Yes, I understood the general setup of the 335's bi-turbo. I just found the 335d's setup to be interesting since I didn't read much on it and assumed it was a similar set up to the N54 utilizing two smaller turbos, each powering 3 cylinders at the same time. And the boost pressure for the diesel is shocking as well!

[ArmyBimmerDude]

Wonder what the exact stock boost pressure is...[/QUOTE]


I believe its 8psi.

[2007/335i/coupe]

Originally Posted by ArmyBimmerDude

Wonder what the exact stock boost pressure is...

I believe its 8psi.[/QUOTE]

Are you referring to the 335i or 335d?

[ksfrogman]

Originally Posted by 2007/335i/coupe

Yes, I understood the general setup of the 335's bi-turbo. I just found the 335d's setup to be interesting since I didn't read much on it and assumed it was a similar set up to the N54 utilizing two smaller turbos, each powering 3 cylinders at the same time. And the boost pressure for the diesel is shocking as well!

I'm glad you posted that link. I enjoyed looking at all their mods: the roll cage, Performance Friction brake setup with 4-piston calipers, trick front strut camber plate.

[Nemesis335i]

I read somewhere that the turbo’s are VGT’s, variable geometry turbos. What this means is that the pitch of the vanes changes through out the rpm band. This allows them to spool faster, as well as, also being method to control boost.

[ksfrogman]

Originally Posted by Nemesis335i

I read somewhere that the turbo’s are VGT’s, variable geometry turbos. What this means is that the pitch of the vanes changes through out the rpm band. This allows them to spool faster, as well as, also being method to control boost.

I too have read this.

[eriks]

Originally Posted by Nemesis335i

I read somewhere that the turbo’s are VGT’s, variable geometry turbos. What this means is that the pitch of the vanes changes through out the rpm band. This allows them to spool faster, as well as, also being method to control boost.

I believe the new Porsche 911 (997) Turbo is the only production car to use a variable geometry turbo. It's been used before in an american car (I forget the make/model) and used in diesel applications for years but the 335 isn't benifiting from this technology. It is pretty though!

[ksfrogman]

Originally Posted by eriks

I believe the new Porsche 911 (997) Turbo is the only production car to use a variable geometry turbo. It's been used before in an american car (I forget the make/model) and used in diesel applications for years but the 335 isn't benifiting from this technology. It is pretty though!

I do recall reading about rumors of this variable geometry turbo in these forums.

Check out this "E92 Official Press Release" thread:

http://www.e90post.com/forums/showth...iable+geometry

Now there was talk about a diesel engine and variable turbine geometry here:

Originally Posted by Catscratch

Elegance at Its Best:
The new BMW 3 Series Coupé.

. . .

Given all these qualities, the harmonious combination of diesel technology and the new BMW 3 Series Coupé hardly comes as a surprise. Indeed, this combination is highly impressive in every respect, particularly as the new BMW 3 Series Coupé is entering the market from the start with a very powerful and muscular straight-six diesel. This outstanding engine develops its power and torque from 3.0 litres engine capacity and features newly developed turbochargers with variable turbine geometry, electrical throttle butterflies and common rail fuel injection boasting the latest generation of piezo-injectors.

[mr2guy]

Lets set the story straight:

Porsche 997 Turbo is the first GASOLINE production engine to use VTG turbos. High exhaust temperatures from the combustion of gasoline have in the past made the implementation of this technology troublesome but the use of higher quality materials in the turbos allow it to be used.

VTGs are not used on the N54 gasoline engine. They may very well be used on the diesel engine in the 335d though as most all modern turbo diesel use them; even the VW TDI engine uses them.

[rwalker]

Originally Posted by mr2guy

Lets set the story straight:

Porsche 997 Turbo is the first GASOLINE production engine to use VTG turbos.

What disqualifies the '89 Shelby CSX "Variable Nozzle Turbo" from your qualification?

http://en.wikipedia.org/wiki/Variabl...y_turbocharger

[theslik1]

Originally Posted by Boost335

Actually, they dont each power 3 cylinders, they are each powered by 3 cylinders, and then boosted gas is combined before it goes into the intake manifold.

Technically, you're correct. Effectively, since the compressors are in parallel and balanced each one supplies 1.5 liters of displacement, equal to "3 cylinders each".

Which makes me wonder how exactly the turbos are balanced flow-wise, and what happens if one compressor is weaker than the other?