MrRat

The advertising copy for the VVEL says it "virtually eliminates" the throttle. There are actually 2 electronically controlled throttle bodies that are in the intake tract on either side of the intake manifold. I've read some magazine articles that imply the throttles are there for some obscure emissions related function (generally the magazine writers are not technical and just parrot whatever the manufacturer tells them).
On the ECU tuning thread it was mentioned that these throttle plates are not always fully open when the accelerator is floored. I see that the throttle plates are attached to the shaft by two philips head screws. I was going to pull one and check to see if the rpms are uncontrolled or not (maybe with the car facing the street instead of the garage ) but didn't have time to finish.
1) I would think that if the VVEL is effective enough in controlling RPM then the throttle bodies could be gutted and polished. This should increase torque/hp and fuel economy as running unthrottled reduces pumping losses.
2) I bet that the VVEL is too limited in function to effectively "throttle" the engine and that's why they included the twin throttle bodies. It also could be a safety issue to prevent "unintended acceleration"

Has anybody tried circumventing the throttle bodies?

Chebosto

iTrader: (1)

drive by wire = ecu controls throttle opening. the only way around this would be going to stand alone engine control unit (Motec) and using conventional throttle bodies that are opened via wires.

MrRat

Supposedly, the variable valve lift controls air intake into the engine. So we should be able to remove the throttle plates and the ECU will control the "throttle" via valve lift alone. The wires would still be connected to the throttle, with the plates removed.

12fear

You cannot remove the trottle plate chambers at any cost. The throttle chambers are actually open 20% at idle and open fully on full throttle. The accelerator pedal actually controls the valves. The intake plenum has little to no vacuum inside it so the throttle chamber is there so when the brakes are applied the plates close so vacuum will increase for brake assist.

MrRat

Again, VVEL is supposed to replace the throttle, similar in function to BMW's valvetronic (which does not make use of the throttle plates). The throttle plates are present in this implementation for some unexplained emission's purpose.

I understand on a conventional engine you need a throttle plate, but this is supposed to be different.

So far it looks like no one has tried removing the plate to see if the engine revs uncontrollably or not...

Chebosto

iTrader: (1)

So why don't u try it then and post the results.

04STi208G37

iTrader: (2)

Did you read post 4. Not to be a Smart *** but post 4 seems to explain your original question. I don't know if post # 4 is correct but it makes good sense. Is seems to address your phrase, "unexplained emissions purpose". He seems to agree the VVel (valves) control the speed but the plates are there for another reason.

12fear

There are two new sensors adopted to the VQ37VHR engine. One of the sensor is mounted near the brake master assy. which is called a boost sensor (Not turbo boost brake boost). The other sensor is mounted on the intake plenum at the top and is called the map sensor. The boost sensor will detect pressure in the brake booster when the brakes are applied therefor the ecm will activate the throttle chamber plates to close so the brake booster will have vacuum assist. The map then will tell the ecm that the intake is now increased in vacuum and the ecm will then monitor it from that sensor(map sensor). So removing the throttle chambers is a no no....

sharif@forged

iTrader: (2)

Their wording is a complete marketing ploy. This is a conventional engine, who's engine speed is controlled by the two throttle bodies. They are trying to meld VVEL and spin it to make it sound like it can control the throttle/engine speed...but it cannot do this. This engine requires TB's, and its not something just for emissions purposes.

Hope that helps.

spyderbret

iTrader: (1)

Yeah, what he said...

Common sense dictates that if the engine didnt need the throttle bodies, they wouldnt be there. I cant imagine any car company putting anything on a car that didnt need it.....

That may be a little stretch but you know what I mean.....

RPF

BMW "Valvetronic" engines do still have a throttle plate, just like the VHR/VE engines do.

It is used on these engine families in the US:

"Prince" I-4 (Mini)
N52B30 I-6 (128/325/328/330/525/528/530/X3/X5/Z4)
N62B48 V8 (x50 cars, X5 SUV)

This seems to be a technology of diminishing importance for the propellerhead crew. The system didn't make it onto the N54B30 that is in the 135/335. Furthermore, they have introduced the N53-series I-6 which features GDI like the N54 and leaves off the Valvetronic from the N52. Supposedly it and the direct injectors vie for the same space in the head.

The VVEL system is smaller, lighter and faster, allowing for the 7600 rpm redline in the VQ37VHR. Nissan has also stated that they intend to use VVEL with GDI in future engines, so obviously the space problem that BMW had with Valvetronic and GDI isn't an issue with VVEL.

04STi208G37

iTrader: (2)

What about the brakes, as referenced by 12fear? Are you saying they would do something else for the brake vacuum if the car did not actually use the TB to Throttle the engine.

spyderbret

iTrader: (1)

My guess is that they would have to.... The vacuum would have to come from somewhere...
The only point I am trying to make is that the throttle bodies are there for a reason. If they were not needed why have them there? Technology continues to advance and I am sure it is possible that someday things will be done differently, until that time I wouldn't recommend that anyone remove the throttle bodies completely.

Now please understand that I am not a mechanic and I may be talking out my ****, but I try to use a combination of common sense and experience as often as possible and it seems to apply here....