Supercharger Final Question (I think)

[Kelster 0]

Okay. From my understanding, if I get myself an 8PSi pulley then the charger will achieve this pretty much on the redline. So is this possible ? Running a smaller pulley say a 14 PSi pulley, dumping all boost above 8PSi to atmosphere or somwhere thus making the 8PSi lower down the rev range and holding it to the redline as shown in my rough drawings ?

[FishWick 21]

You would need some kind of electronic dump valve control. How about a schrick controller opening a dump valve instead of the flap?

[Kelster 0]

How about a turbo wastegate valve ? Instead of controlling the boost by bleeding exhaust gases, it could bleed off the intake ?

I assume that would mean I have a wastegate and a bypass recirc valve in the intake pipe ?

[rodney 17]

Wellllllll........... yes but...... ???

The pulley would only give you minimal boost increase at lower revs, the size/ratio of the wheel and turbine control this. Also the type of pressure relief would need a very accurate control.

if i use this as a way of explaining it. if you are in the cruising zone of the rev range then the valve doesn't just snap open.... it bleeds open so the car would be running in quite an in-efficient way and not seeing what it is expecting to see.

you can achieve a similar effect by limiting the set up thus controlling the boost. i.e the fueling etc. that way you don't expose the system to the inaccuracies of a valve and your foot position.

In order to improve on the bottom end boost you need to look at the cool air route in. no bend over 30 degrees and ideally less than 2 bends. Theoretically every bend over the 30 degree swipes 5hp and associated torque. if you were to spend some time on this end and look at the 4" rather than the standard MAF then this would benifit the flow in. Next ensure you have at least a 2.5" zorst. (Ovals are acceptable as they have the same air flow as a circle... but their must be a gradual change not an oval bolted to a circle) Again angles less than 30deg for any joins and no more than 2 boxes with a CAT Bypass off a manual switch. The manifold must have an extended flow radius under the car at the joining point.

This sounds like a lot but it will make it much more user friendly. As you can appreciate the valve is based on a spring that works off pressure - internal or external, differential or vacuum. as the pressure builts to the point of movement the spring will allow the flap to start to move slowly. This then allows the gasses to escape. The issue is that the MAF will be seeing one volume of air and the engine another. Controlling the gas in the cylinders will be very dificult and worst case you could look at detonation with in the engine due to your fuel mixes/inaccuracies.

I know this opens a box or worms and I am sure there will be more comments from the guys..... But have a chat with someone who can actually map the system you are using and see what they can do for you from that end.

As you can appreciate this is just my opinion.... I hope it helps..

Cheers

[Kelster 0]

Thanks alot RCF will bear all that in mind when designing this.

How about if the MAF was after wastegate and recirc then it could monitor the actual air entering the system ?

[FishWick 21]

How about a turbo wastegate valve ? Instead of controlling the boost by bleeding exhaust gases' date=' it could bleed off the intake ?

I assume that would mean I have a wastegate and a bypass recirc valve in the intake pipe ?

[/quote']

I don't think that would work. In turbo applications, when the WG is open, there's still enough exhaust pressure to drive the turbine and therefore make boost. Boost 'pressure', remember is the result of flow that can't get in the engine, there's always a restriction, aka head pressure.

On the boost side, if you bleed that off, you could end up losing all of it and not just some of it.

I don't think I explained that very well, LOL!

[Kelster 0]

Thanks Kev, yeah I think I got what you said. But surely if the boost was all going to be wasted then the pressure would start to drop and valve would close and maintain it ?

As a matter of interest, on peoples set ups. Where did say 6 PSi come in on 6, 8 10 and 12 PSi set ups ? If it is only say a few RPM then this whole idea may not be worth it.

I did find this though Universal Blow of valve

[rodney 17]

the psi level is dictated by the pulley size on any individual manufacturers turbine.

I forget the values of the top of my head. but if you review the bit in the members section you will see the VF9 ratings towards the end of the the build FAQ thread.

I have a VF9 stage 2 set up and i am only running at 260ish. but the curve and delivery is really smooth. the spool up is instant but the individual map and charger set up will vary from an rpm level as to what boost you achive when. if you're at 12psi at 7k then you would expect 6psi at roughly 3.5k, based on a linear curve with standard cams and a constant ambient temperature of 20deg C.

however the set up can affect the feel of this. you can set it up so you get that kick in the pants feel from 4.5k when all the air and fuel is flowing as you want it to.

That said i like the fact that as i pass the 2.5k I can hear the pressure spool up in the system.

The best advice I can give you is, if you haven't had the chance yet. Make sure you sit in one or 2 and just go around the block. They will be different animals each time as so many things affect the set up and delivery

[rigs 0]

I'm curious as to the point of this?

What's stopping you just running a 14psi pulley?

[Kelster 0]

An 8 PSi pulley will produce 8PSi at pretty much the rev limiter. A 14PSi pully would probably produce 8PSI around 4-5k RPM. So if this system was possible then you could have 8PSi of boost from 4-5K all the way to rev limiter using the 14PSi pully, giving you the desired power output (8PSi) for much longer.

You could just run a 14PSi pulley and have the engine modified to take the extra boost I suppose that would be easier but that boost would only be achieved at close to the rev limiter. if you went to all that trouble of engine modification, then you could, in theory put on a 20PSi pulley, set the wastegate to waste all boost above 14PSI and get the 14PSi alot lower down the rev range giving you even more usable power.

This is kinda theoretical but the Americans have done this to good affect on Mustangs, bringing the desired supercharger boost in much sooner.

I should also add, that this is just my understanding of what could happen, this is by know means would happen. I am sure there are more people on this forum that have a greater understanding of the whole process.

[FishWick 21]

I don't think it's quite as easy as that. When I had my 12psi pulley on, it certainly wasn't making more boost at lower rpms as expected.

There is such a thing on the market that does exactly what you want. It's called a Turbo :-)

[Kelster 0]

Cheers Kev, I think the turbo is the route I am now heading so I guess I will have another million questions to ask shortly I also think it will turn out cheaper than my Rotrex idea.

[Antihero1981 8]

i think you would be limited by the charger and what they can spool at...i dont think you can run vortechs with high Boost? not without upgrading to thrust ceramic bearings.....or so i am told

i run stage 2 and got stage 3 bits....but not fitted them

[FishWick 21]

Cheers Kev' date=' I think the turbo is the route I am now heading so I guess I will have another million questions to ask shortly I also think it will turn out cheaper than my Rotrex idea.

[/quote']

You only do it once (you hope!) so you need to make the right choice :-)

Because you've said you want your 8psi to come in lower down the rev range, a turbo is definitely for you!