boost maths queston

[WabTheKing]

if johnny fits a supercharger that creates 825cfm @36,000rpm on to a 4.2 v8 with a 600mm x 240mm x 75mm intercooler how much boost will johnny have?

compression ratio is 10.6:1

standard engine is 380nm torque 294bhp

how much power will johnny have?



if they asked questons like this at school i would have been much more interested lol

there is an upgrade to 1200cfm @44,000rpm but too many pennies at the mo.

[prj]

Need engine VE to know that, basically how well it flows.
If for example the valves are tiny, then Johnny can have 3 bar boost, and no power, while if there was no such restriction, then Johnny could have more power at 1 bar boost.

P.S.
You need to drop the CR.

[WabTheKing]

... 90% @ 4000 rpm
... 97% @ 5200 rpm
... 94% @ 6000 rpm

[prj]

That looks a bit too high.
You got that from VEMS, right?

[WabTheKing]

yeah

[WabTheKing]

ABZ engine code with variable length manifold

[WabTheKing]

Need engine VE to know that, basically how well it flows.
If for example the valves are tiny, then Johnny can have 3 bar boost, and no power, while if there was no such restriction, then Johnny could have more power at 1 bar boost.

P.S.
You need to drop the CR.

this is really the queston im trying to obtain, how much boost can be run on stock CR on 98-102ron fuel so i can size my pulleys accordingly.

this supercharger runs very cold due to it being an internal belt drive rather than gear driven so intake temps are alot lower than a normal supercharger, its also a centrifugal type not a root charger

[prj]

I see where you are going with this

Here is a XLS for turbo calculations on AAN.
It has some VE based calculations, like CFM.

You should be able to plug in your numbers, and with some editing manage to get the answer.
You'll first have to match the curve though, if you want to have interpolation...

It's a bit messy, since I did not mean it for public consumption, and I made it a while ago.

[prj]

How much boost you will be able to run will be clear during mapping, just add boost until you stop making power (because you have to drop more and more timing), then go back a bit.

Or if someone has done this before, they might know.

Is there no possibility to control boost electronically on this thing?
Sorry, I have absolutely zero experience with superchargers.

[WabTheKing]

How much boost you will be able to run will be clear during mapping, just add boost until you stop making power (because you have to drop more and more timing), then go back a bit.

Or if someone has done this before, they might know.

Is there no possibility to control boost electronically on this thing?
Sorry, I have absolutely zero experience with superchargers.

guy who's mapping it has used these chargers before on bmw 4.0 v8s

hes estimating about 100bhp increase from stock running 10psi on stock CR, there are electronic boost controlers or limit valves available altho not strictly needed if you match your pulleys right as boost is linnear to rpm

im basicly just doing my homework to see what should happen in theory

[WabTheKing]

if you get the upgrade you can make more boost early ( this one doesnt really do much untill the higher rpms) then vent the excess pressure using a valve