VNT Control

[rodpaslow]

I've read over the posts of the throttle controlled VNT and they look like should work well- as well as the electrically controlled one.  I have one question as I was thinking if it would be possible to use a solenoid in conjunction with the flipped can (so it's vacuum controlled).  You could make it with a rpm switch that when the engine hit what rpm maybe 1500 -1700 the solenoid turned on and put the vnt to full boost and the vacuum can would do the rest.  Has anyone tried something like this?

[Bugsy_malone 666]

I am not trying to be unhelpful, but why would you use a solenoid to do this?

I have only briefly looked into VNT turbos (eg in the past week) after seeing the build for the T25 and I see why it makes sense to have a mechanically controlled system when an ECU cant do the job.

My thoughts would be that by having a RPM switch which might take some work in itself and would create turbo lag? From what I understand the VNT has the vanes 'shut' pointing at the turbine wheel when in the lower end of the RPM band so the turbo will spool up, easing off as pressure increases to allow the greater exhaust gas flow to keep at a set pressure.

by linking it mechanically to a throttle means if you were at half throttle and put your foot down the vanes close under your foots control to give you pretty instant boost response with the vac can then sorting things out once higher boost levels are acheived.

I may have missed the point of VNTs at this stage or possibley just using the solenoid as a switch.

On the other hand I could see the point of having a solenoid operate as part of the mechanic system to almost switch the boost off around town etc so that it only works when it gets to motorway speed(so the vanes are perminantly open and it takes alot more to spool up), which with a petrol car has the advantage of fuel economy, but with a diesel I am not sure it does?