Electronic boost controller

[Apache]

This is meant as a kick off point to get some ideas flowing, so no nit picking of detail - yet!

Been thinking about boost control, and talking to a friend of mine who has a lot of experience of turbo cars, we've come to the conclusion that electronic control of boost is safest, and allows finest control.

It seems to me that a way of doing it would be by measuring the boost pressure electronically (which is why I was asking Matt about Maplin pressure sensors yesterday) and using this data which is presumably a varying DC voltage related to boost pressure. You could then use a comparator to take this data and feed a solenoid with a variable duty cycle square wave via a voltage to freq converter (at a highish frequency to avoid boost modulation - so solenoid small) which would bleed off pressure off from the waste gate feed.

Obviously when required boost is reached, the soleniod would be bleeding off the correct amount of pressure to have the waste gate open at that pressure.

It should be a simplish matter to tune the hysterysis of the comparator to avoid the initial boost spike common (I'm told) with mechanical boost controllers.

Any thoughts?

[MattF]

So literally, raise boost and then vent when a threshold is reached?

[Apache]

So literally, raise boost and then vent when a threshold is reached?

Yep, thats about it.

I expect you'd have to start venting before the threshold to prevent overshoot due to hysterysis in the mechanical parts of the system, but that shouldn't be difficult.

At the required boost, the duty cycle of the solenoid would be venting the excess of pressure required to hold the correct boost pressure.

[MattF]

Yep, thats about it.

I expect you'd have to start venting before the threshold to prevent overshoot due to hysterysis in the mechanical parts of the system, but that shouldn't be difficult.

At the required boost, the duty cycle of the solenoid would be venting the excess of pressure required to hold the correct boost pressure.

I might be misinterpreting the specifics, but if that's the intention, why not just raise the boost, (by whatever method), then use a BOV set at the required threshold?

[MattF]

BTW, you know when you mentioned piezo pressure sensors, were they a specific sensor, or were you meaning to try and run a transducer sods way round?

[Apache]

I might be misinterpreting the specifics, but if that's the intention, why not just raise the boost, (by whatever method), then use a BOV set at the required threshold?

Can you get electronically controlled BOVs? If so, then it would be a simple matter to just fit a restrictor calibrated to the max boost and then use the BOV to adjust boost to the required amount up to the max set by the restrictor. Yes?

[Apache]

BTW, you know when you mentioned piezo pressure sensors, were they a specific sensor, or were you meaning to try and run a transducer sods way round?

No, Maplin used to sell them. 0-30psi range. Ideal as the basis for electronic boost gauge / controller.

I've been looking at the pressure sensors fitted to Renault Laguna tyres... I wonder...

[MattF]

No, Maplin used to sell them. 0-30psi range. Ideal as the basis for electronic boost gauge / controller.

I've been looking at the pressure sensors fitted to Renault Laguna tyres... I wonder...

Just thought. Digital tyre pressure gauge.

[MattF]

Can you get electronically controlled BOVs? If so, then it would be a simple matter to just fit a restrictor calibrated to the max boost and then use the BOV to adjust boost to the required amount up to the max set by the restrictor. Yes?

An article here:

http://autospeed.drive.com.au/cms/article.html?&A=2188

[MattF]

No, Maplin used to sell them. 0-30psi range. Ideal as the basis for electronic boost gauge / controller.

Can honestly say I'd never heard of those. One learns something new every day.

[MattF]

And, a basic rundown of a few different types:

http://wwwrsphysse.anu.edu.au/~amh11..._off_valve.htm

[Sancho]

Don't even try to explain the ins and outs of this to me (one day someone will ask if anyone knows how to build 100 flats in the middle of London and I'll get to look clever) but these are on ebay and cheap enough to arse around with.

[AndyLala]

Also, please consider in the discussion what would happen should the wastegate control fail/fuse in a locked position... that would get rather messy... but sounds very interesting so far...

[Apache]

Also, please consider in the discussion what would happen should the wastegate control fail/fuse in a locked position... that would get rather messy... but sounds very interesting so far...

Had thought of that. A mechanical restrictor (a calibrated hole!) set to your maximum allowable boost pressure would provide a failsafe.

[MattF]

Andy, may also be worthwhile popping a thread up on the Oz site. Some of their members tend to be quite knowledgeable with borderline theories and ideas.