Been a long time reader here in the F.I. section and although I've since parted ways w/ my FI s2, I still find this board an excellent source for quality information.

Heres my question, I own an rb25det powered Nissan. Among many other modification, it is also has a Haltech Platinum Sport 2000 for its engine management. I also own a very nice Holset HE351VE turbo. Right now I'm trying to find a way to porperly control the VGT electronically though the Haltech. I know it can control the servo for the turbo, and I have not yet got it able to accept the pusle signal from the compressor wheel speed sensor, but I'm confident I will be able to. What other inputs has anyone else used to regulate the vanes? I'm thinking TPS, MAP, RPM might be my three best. But injector duty, even egt might be worth using as well. Some people are having moderate success w/ Megasquirts, maybe some AEM guys have dabbled with this before here?


For all those unaware, the VGT system on the HE351VE allows for a variable turbine housing size. From a tiny 2cm^2 to a MASSIVE 25^cm (so large the housing doesn't need a wastegate depending on application). I havent seen many people on here using the VGT system, but it will catch on. People have show some extremely impressive numbers while using the VGT w/ mechanical actuators. I would just like to use it electronically though.

FYI, heres a video for all your curious members:
HE351VE
At start up the vanes are close (very small turbine housing) and you can hear the turbos very high speed at idle over the motor. You then see the owner reach down and open/close the vanes, which in turn affects the turbos speed.

 

Doesn't the Acura SUV (RDX i think) use something like this?

 

Yes so do porsches. But I'm sure they have done extensive research to control the geometry of the turbo for different conditions.

 

Hmm...

The simple way is to use it to hit a boost target. So basically what a regular actuator would do.

If you can create a 2D map using MAP and RPM as your axis, the and the variable being vane position...

If you can get super fancy, throw in TPS too. Reason I would consider doing that: at light loads such as cruising, I would want the vanes wide open to minimize exhaust backpressure. I think that'll improve gas mileage. As soon as you go over some TPS voltage, have the vanes close down to spool up the turbo as it'll 'know' that you actually want to accelerate.

I am curious as to how the stock logic works on the OEM applications.

 

I don't think opening the vanes would increase gas mileage?

 

open vanes would be less exhaust back pressure and could be better MPGs. For example, the holsets shuts its vanes to assist with engine breaking, pretty nice for a big truck hauling a load down hill or such.

I think it would certainly need 3 variable, MAP and RPM for sure, TPS seems like the logical 3rd option. Ideally I could create a setup which would always have the vanes fully open before any external wastegate was ever opened.

The stock logic is very complicated, but it also offers more benefits then I am seeking. I am not interested in using the turbo to increase engine brakeing, or using the vanes to regulate engine temps. Im just looking for a flexable a/r ont he housing for the purpose of increased response/spool w/o sacrificed power up top.

 

On an OEM application the control would be drastically more complicated always working to maximize BSFC by creating the greatest efficiency in terms of MAP/EMAP at any given power requirement. Assuming the platinum sport is the same as the platinum PNP for a 350z you are going to have a hard time controlling it using the turbine speed sensor, you would have to be able to read a digital input at 2000hz and that's if the sensor was only picking up a signal once per revolution. Even without that you are only going to be able to base it off two variables and essentially use it as a boost controller.

I assume by servo you mean solenoid because the Haltec cannot control a servo (without external electronics)

 

Also open vanes will not make better gas mileage, maximizing BSFC by creating the greatest map/emap ratio will (which will not mean opening the vanes all the way or even close to it).

You need to be monitoring drive pressure (EMAP) more so than TPS although all of the variables mentioned so far would be useful but the Haltech doesn't have the control strategy to use all those. If I had to pick two it would be MAP and EMAP.

 

I had a VGT on my truck. You might try the diesel truck sites like dieselplace or dieselstop for info on VGT control - lots of aftermarket hotrodding going on.

 

Hmm.... I would agree if the engine were operating at some significant load. But i was thinking light cruising, like putting around in 6th gear at 50-60mph. In this situation, you'll have significant vacuum in the intake manifold. To maximize your MAP:EMAP, you would need to minimize EMAP, and therefore I'd think you would want the vanes being wide open.

On a diesel with no throttle, I can see the situation being different.

Please explain further!

Oh yeah, I'd moniter EGTs. Diesel stuff has a way of breaking at gasoline temps!