14 replies to this topic

[HUBBA.HUBBA]

Looking to tidy up my engine bay, was thinking of using a vacuum block manifold. I've added a diagram of my current layout (Vacuum pipe in red). The pipe to the fuel pressure gauge is straight off the plenum (pre throttle) and everything else is taken off the inlet manifold (post throttle). Could I run everything off the plenum take off? I would prefer it, especially as it's charged air and fuel mixture going to apparatus in the cabin and if any failed I would get a high pressure mixture spraying inside. Presumably there would be a vacuum in the plenum when the throttle is closed? Fyi - I have plumbed the bypass/recirculation valve to open upon vacuum.
 20180130_132403.jpg   26.67K   7 downloads

Edited by HUBBA.HUBBA, 30 January 2018 - 01:42 PM.

[Ethel]

I'd say the fuel pressure regulator is best as it is on its own line for a clean and responsive signal.

 

Bypass valve is waste gate actuator? They're usually run off the compressor outlet on the turbo for the same reason - by the time the gate's open it could be too late to blow off the over-boost if it's sensed a lot nearer your engine.

 

Just realised I'm talking turbo, but if anything the last bit applies even more.

[HUBBA.HUBBA]

I'd say the fuel pressure regulator is best as it is on its own line for a clean and responsive signal.

 

Bypass valve is waste gate actuator? They're usually run off the compressor outlet on the turbo for the same reason - by the time the gate's open it could be too late to blow off the over-boost if it's sensed a lot nearer your engine.

 

Just realised I'm talking turbo, but if anything the last bit applies even more.

I was thinking that too regarding having its own line and being more responsive.

 

Would the vacuum still be the same either side of the carb butterfly when closed. I thought it would be as the air is only being drawn from one place. I'm just about to get a plenum made up, wonder if it'll be worth having 2 vacuum take off's just in case.

[Ethel]

Not 100% sure what you mean...

 

Air is elastic so if you put a restriction in, it'll stretch thinner (lower pressure) on the side of the restriction that's being pulled (by the engine). It bunches up (high pressure) before the restriction if it's being pushed (by the blower).

 

Looking at your diagram again it looks like you're after using a recirculating dump valve (the blow off) for when you change gear etc? That would be piped to the engine side of the throttle as it uses manifold vacuum to tell it's shut and the boost isn't wanted.

 

If you are dumping compressed air back before the blower it'll be hot as well as already at a higher pressure. Better if it's gone through the inter cooler and isn't restricted into the atmosphere via the air filter.

[bluedragon]

When I read this, thinking about modern supercharger designs (to me the last 25 years are modern  ) the bypass valve would be a valve that bypasses the supercharger pathway entirely when boost isn't needed.

 

This improves fuel economy by allowing the supercharger to freewheel and not do unwanted work compressing air when the boost isn't required. 

 

It is relatively unknown in the Mini world because the vast majority of the Mini A-series supercharging solutions run wet superchargers - i.e. fuel is mixed with the air upstream of the supercharger, meaning the supercharger is compressing both fuel and air. A bypass valve such as I'm describing would be impossible with this method.

 

But all modern supercharger solutions include such a valve, since no OEM runs a wet supercharging scheme.

 

 

Dave

Edited by bluedragon, 31 January 2018 - 07:05 AM.

[HUBBA.HUBBA]

Not 100% sure what you mean...
 
Air is elastic so if you put a restriction in, it'll stretch thinner (lower pressure) on the side of the restriction that's being pulled (by the engine). It bunches up (high pressure) before the restriction if it's being pushed (by the blower).
 
Looking at your diagram again it looks like you're after using a recirculating dump valve (the blow off) for when you change gear etc? That would be piped to the engine side of the throttle as it uses manifold vacuum to tell it's shut and the boost isn't wanted.
 
If you are dumping compressed air back before the blower it'll be hot as well as already at a higher pressure. Better if it's gone through the inter cooler and isn't restricted into the atmosphere via the air filter.

Yep this how my engine bay currently is. The reason I was asking about The pressure either side of throttle was because as soon as the recirculation valve opens it relieves the pressure build up before the throttle, so the neg pressure should equalise each side of the butterfly. Just wondered how quickly it would equalise. Enough to use the vacuum take off from the plenum for my other items that utilise the vacuum ie boost gauge, mapping and water meth injector controller. So there is less pipework everywhere. I'll do a diagram as to how I'd like it to be

[HUBBA.HUBBA]

I like the idea of the recirc valve being after the intercooler. I did it that close to the charger before cause alot of chargers have them built in.

[HUBBA.HUBBA]

When I read this, thinking about modern supercharger designs (to me the last 25 years are modern  ) the bypass valve would be a valve that bypasses the supercharger pathway entirely when boost isn't needed.
 
This improves fuel economy by allowing the supercharger to freewheel and not do unwanted work compressing air when the boost isn't required. 
 

When you describe the air actually bypassing the super charger when not required, I think of twin charging with a turbo. Where the turbo my draw air passe the super charger via the bypass valve.

[HUBBA.HUBBA]

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If we forget about the turbo in the diagram for a miniute. It may look like the air would bypass the charger with recirculation valve closed, but the reality is the air blowing out of the super charger would be exiting at that valve and recirulating.

Edited by HUBBA.HUBBA, 31 January 2018 - 03:34 PM.

[HUBBA.HUBBA]

Looks like the spammers are liking this topic.

[HUBBA.HUBBA]

 20180131_154300.jpg   31.19K   1 downloads
This is how I would like my vacuum pipework. All off the plenum, But would there be enough vacuum straightaway that side of the throttle?

Edited by HUBBA.HUBBA, 31 January 2018 - 03:47 PM.

[HUBBA.HUBBA]

Ethel - Think I'm going to do it this way.  20180131_160550.jpg   29.94K   1 downloads

[Ethel]

Take it Mapp is for ignition timing - it must be down stream of the carb to see the manifold depression, same as vac advance on a dizzy. Similar for the cooling injection, if it's not to run when the throttle's closed.

 

If the carb is done like the Metro Turbo the FPR must be before the plenum restrictor to sense the boost.

[HUBBA.HUBBA]

Ok will do cheers

[HUBBA.HUBBA]

Right, got my new intercooler and plenum. Not enough room to fit recirculating valve between intercooler and plenum, but i have had a BOV take off welded onto the plenum i could utilise. 

One question - I have a water/meth injector (currently just using water, but will move to water/meth mix) mounted within the circle of the restrictor ring. Due to the close proximity (within the plenum) of the injector. When the recirculation valve opens am I likely to get unused water (or water/meth) going down it and recirculating through my charger, 

 

I can set the water injector to activate at what ever boost pressure I like. I have plumbed the diaphragm in the recirculating valve to solely work on vacuum not boost pressure build up, so i wouldn't be relying on boost build up in order to the valve to open.

Edited by HUBBA.HUBBA, 12 February 2018 - 04:26 PM.