If valvetronic, why is there a throttle body? - BMW 3-Series (E90 E92) Forum

DJRobbGordon · 11-04-2005, 09:00 AM

All,

I was looking through pix o the n52 engine I took at a 3-er product pavillion when i was in Munich and I noticed something... a throttle body.

I dont have the pix handy but have attached a pic from the part catalog that is referenced in the DYI forum.

My question is this: with valvetronic on the engine, which is supposed to replace the use of a throttle body, why do we still have a throttle body? is it a failsafe? does valvetronic only work in certain engine regimes?

JamieA · 11-04-2005, 09:16 AM

Quote:

Originally Posted by DJRobbGordon

All,

I was looking through pix o the n52 engine I took at a 3-er product pavillion when i was in Munich and I noticed something... a throttle body.

I dont have the pix handy but have attached a pic from the part catalog that is referenced in the DYI forum.

My question is this: with valvetronic on the engine, which is supposed to replace the use of a throttle body, why do we still have a throttle body? is it a failsafe? does valvetronic only work in certain engine regimes?

The BMW literature I have read on this matter says that the throttle body is retained as a failsafe mechanism. So you are quite correct.

Because it reamins fully opened, the aerodynamic losses are minimised.

mapezzul · 11-04-2005, 09:18 AM

What is the part number on the part you displayed??

06graphite · 11-04-2005, 09:33 AM

what purpose does the failsafe serve?

why do we need one?

E90Fleet · 11-04-2005, 09:48 AM

All Valvetroic engines have this large throttle valve.

Its usually wide open, except at idle

Its required at idle speed to help create a bit of turbulance in the incomming air , and to help maintain a nice stable idle. But then it goes wide open and stays there untill the revs drop enough ( it helps maintain a slight vacuume n the intake at idle speeds )

Tierfreund · 11-04-2005, 11:05 AM

I just know, somebody is going to take it out "to increase the airflow" in some home made "performance" mod.....

blueStreak · 11-04-2005, 11:59 AM

Quote:

Originally Posted by Tierfreund

I just know, somebody is going to take it out "to increase the airflow" in some home made "performance" mod.....

e90driver · 11-04-2005, 12:04 PM

Quote:

Originally Posted by Tierfreund

I just know, somebody is going to take it out "to increase the airflow" in some home made "performance" mod.....

more performance

be back in an hour or two...

just kidding

DJRobbGordon · 11-05-2005, 01:54 PM

So, some further research and talking to some engine engineers leads me to the following conclusion (other than the failsafe, which sounds feasible):

There are certain circumstances in which a sizable vacuum in the intake is required:
-regimes that require EGR
-canister purging

the vacuum is required in these cases in order to draw gases (exhaust gas in the case of EGR, raw hydrocarbons in the case of canister purge) into the intake manifold. the throttle body is there to cause the nessacary pressure drop.

11-04-2005, 09:00 AM	#1
DJRobbGordon Private Drives: 325i-SpkGrph,BlkLt Join Date: Jun 2005 Location: Ann Arbor, Mi Posts: 36 iTrader: (0)	If valvetronic, why is there a throttle body? All, I was looking through pix o the n52 engine I took at a 3-er product pavillion when i was in Munich and I noticed something... a throttle body. I dont have the pix handy but have attached a pic from the part catalog that is referenced in the DYI forum. My question is this: with valvetronic on the engine, which is supposed to replace the use of a throttle body, why do we still have a throttle body? is it a failsafe? does valvetronic only work in certain engine regimes? Attached Images

11-04-2005, 11:05 AM	#6
Tierfreund Major Drives: E90 330i Join Date: Apr 2005 Location: Germany Posts: 1,003 iTrader: (0)	I just know, somebody is going to take it out "to increase the airflow" in some home made "performance" mod..... __________________ No, not THAT kind of tierfreund!

11-04-2005, 09:18 AM	#3
mapezzul Special Agent Drives: Depends on the day! Join Date: Jul 2005 Location: New York Posts: 1,178 iTrader: (1)	What is the part number on the part you displayed??

11-04-2005, 09:33 AM	#4
06graphite Second Lieutenant Drives: '07 328xi Coupe Join Date: Aug 2005 Location: Plainville, MA Posts: 225 iTrader: (0)	what purpose does the failsafe serve? why do we need one?

11-04-2005, 09:48 AM	#5
E90Fleet Major General Drives: BMW Join Date: Apr 2005 Location: South Africa Posts: 6,515 iTrader: (0)	All Valvetroic engines have this large throttle valve. Its usually wide open, except at idle Its required at idle speed to help create a bit of turbulance in the incomming air , and to help maintain a nice stable idle. But then it goes wide open and stays there untill the revs drop enough ( it helps maintain a slight vacuume n the intake at idle speeds )

11-05-2005, 01:54 PM	#9
DJRobbGordon Private Drives: 325i-SpkGrph,BlkLt Join Date: Jun 2005 Location: Ann Arbor, Mi Posts: 36 iTrader: (0)	So, some further research and talking to some engine engineers leads me to the following conclusion (other than the failsafe, which sounds feasible): There are certain circumstances in which a sizable vacuum in the intake is required: -regimes that require EGR -canister purging the vacuum is required in these cases in order to draw gases (exhaust gas in the case of EGR, raw hydrocarbons in the case of canister purge) into the intake manifold. the throttle body is there to cause the nessacary pressure drop.