Effective supercharger boost control.

[GazM3]

Been a while since I visited here.

I have 2x simeltanious supercharged builds going on.

1/ e36 euro s50b32 built engine 8.5:1 comp 16psi Intercooled

2/ e34 540/6 m60b40 standard motor 10-12psi Intercooled

on both cars I'm running a standalone (link on e36, haltech on e34).
Both are going to run e85 fuel and as they are road cars I want the ability to run ron98 with a flex fuel sensor. The e36 will see the racetrack so boost control is primarily for rain to reduce power.

with the e34 the std engine is for memory around 10:1. I don't think it will cope with 10-12 psi boost with the Ron 98 so the boost control is to work in conjunction with the computer so when it detects the levels of e85 are dropping ( say a mixed fuel blend ) it drops boost a little in proportions with the timing and fuelling with the input from the flex fuel sensor. My Mrs will be driving this car regularly so ideally I want to have it setup where the control happens automatically as it will be hard to setup a system where u have to flick this switch and that dial based on what fuel I'm running.

The e34 will be done first I have everything for it except for an upgraded fuel pump as I would say the std one won't cope with the demand for e85. It's just waiting for the mechanics queue.

As um a relative newbie to this just go easy on me LOL

[5mall5nail5]

Firstly - I think an M60B40 will hold 10 - 12 psi no issue - it's all in how it's tuned. What blower are you going to run 10 - 12 psi from? As you know, boost pressure alone does not tell us how much power this setup is going to produce.

With that, there is a super easy way to control boost on supercharged setups:



A turbo wastegate! Simply install that on your charge pipe (pre-intercooler is likely preferred so you don't needlessly cool air that will be vented). Run a spring for the lowest desired boost pressure, apply pressure from the charge pipe to the wastegate bottom fitting and now you will create a 44mm boost leak whenever you reach that spring pressure. So, in a rain situation, use electronic boost control (just like you would for a turbo configuration) to regulate the pressure down to spring pressure. When it's dry simply use a MAC boost solenoid to limit the pressure that the wastegate sees by altering duty cycle to the valve. Presto. You'll need to run a steel charge pipe at the s/c so that you can weld the Tial flange on.

There's really only one issue with this setup: there's nothing keeping you from over-spinning the s/c. So, as long as you realize that your headunit is going to turn at the same speed whether you ask 3 psi or 12 psi from it, then you're good. In this situation you're creating a boost leak that bleeds off pressure, it obviously does not stall the compressor wheel like it would on a turbo setup when situated between the exhaust valve and turbine.

[GazM3]

Cheers. I thought of a waste gate on the high pressure line with the excess looping back to the pre supercharger intake. It will ad you said spin the supercharger at the peak speed you set for the pulley. One of the good things I see of this on low boost setting as it will boost at the same rate and then flatline at the waste gate/solenoid set position. So my understanding is I would size the waste gate spring for the lowest boost I want (say 6psi) then use the solenoid (controlled by a dial or better by the standalone / flex fuel sensor).

Sounds good.

My my kit on the m60b40 is the ESS so has the basic vortech which to my basic research will be capable of 600odd HP. I can remember looking some time ago that the Porsche 928 place does a juiced up impeller taking the basic vortech and getting it close to the spec of the T-Trim one. A few of these may make it onto the shopping list.

Thanks again for the advice. It's nice to get it explained clearly

The builds are just to create some fun cars. Don't need the fastest 1/4 or the most HP I'm just looking to build it to its potential. To be honest the ESS kit without Intercooler is hardly worth having in Australia as the heat soak makes it perform in traffic not a hell of a lot better than a NA engine.

[5mall5nail5]

I thought the porsche modification was a powerdyne wheel not vortech but I could be wrong.

[dbarton62]

I did this on my vortech on an M54B30, but recirculated the bleed off back between the MAF and the turbine so as not to mess up the measured air. I used a Turbosmart Kompact BPV.
It seems to work well and have seen 10psi before bleed off starts at around 5500rpm

[GazM3]

I thought the porsche modification was a powerdyne wheel not vortech but I could be wrong.

I'll go read again to confirm.

[pbonsalb]

I'll go read again to confirm.

I think there are aftermarket vortech wheels now just like powerdyne. Superchargerrebuilds.com may sell them as well.

[GazM3]

Yes they have vortech wheels it seems. Always nice to move more air for same amount of boost. Looks with the standard vortech unit that comes with the ESS kit you will be close to maxing it out at 500rwhp where with the improved impeller 500rwhp will be right in the happy zone for it.

[GazM3]

Some time between posts.
The wastegate on the pressure line works perfectly well. I set it up with an 8psi spring in the WG and use a 3 port solenoid so I can have a high/low switch in the cabin so effectively have 8psi for low boost and 17psi for high boost.

I ran it this way for some time, but recently fitted a stand-alone ecu and custom headers. With these changes it has made a massive difference to the power with it correctly timed and fueled for e85, to the point even 8psi is too much. Was thinking of putting a 3psi spring in the WG and using a variable dial (rather than a switch) making it talk fully to the ecu as well.

Is there any issue running it down as low as 3psi which would make it at power levels only modestly above NA levels, with the ability to turn up the dial when need be.