[Saab_c900] Are new turbo overboost switches for 8V engines available?

Question

Hiya,Got a bit of an issue with the overboost switch in my 8V turbo. Has a big vacuum leak and I think it's one of the reasons that the engine's not running properly (and not starting at all currently). I've got a replacement but it's turned out to be the one for 16 V engines and I'm betting their pressure settings are different. 8-) has the 8V ones priced at a massive US$116! Seems a lot for a small device but then if they're new, perhaps it's not so bad.Are there any other sources of these switches (Saab # 8579963) as new items that you know of? If I do need to get a new one, it'll be handy to have some alternative sourcing info available.In the meantime I'm going to try out the 16V version (Saab # 8594632) and see if it'll help to solve the current problem(s).Regards,Craig.

ShazWozza · Accepted Answer

Craig, why can't you just use a generic adjustable Hobbes switch?

Craig's Saab C900 Site · Answer

What is a Hobbes switch? 8-)Craig.

ShazWozza · Answer

A pressure operated switch. Some folks spell them Hobbes and some Hobbs. I suppose it is the name of the guy who first designed one. Examples being your overboost detector, oil pressure switch yadda yadda If you are really stuck for a genuine Saab overboost switch I don't see why you can't use one.

A common after market use for them is in boost sensors for controlling water injection.

I think from memory either AutoSpeed.com or Silicon Chip have designs which use them in various boost pressure related projects. I would check out Oatley Electronics or Jaycar. I found this Sydney link here

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have a A$40 switch (no idea of the quality). Hobbes switches come in various ranges of pressures and many can be adjusted. It is also possible to use one with a lower pressure rating by way of a restrictor (in which case you would need to calibrate the restrictor hole carefully).

Craig's Saab C900 Site · Answer

Ok thanks. I've found a few of them on Ebay. Seems that these generic items have a threaded connection. I have no idea what the pressure settings for the overboost switches used by Saab are, but there are a couple of these 'Hobbs' devices specifying 15 psi which sounds about right for an 8V non-APC turbo engine, though I'm open to correction...

Craig.

[Saab_c900] Are new turbo overboost switches for 8V engines available?

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