Mini supercharger on 1zz

[lamcote]

Have you found the Mini SC outlet pipe yet. I have come up with one more option that could remove the need for a new subframe and would use most of the standard Mini plumbing!! I would need accurate measurements of the fully assembled SC with the big outlet pipe attached to test the theory.

I know you like having the new subframe, but if we could delete that it would make the cost of including a piggyback ECU more affordable and that would simplify the whole project so I thought it was worth ruling in/out.

[Carolyn]

Target RPM for SC?  I'm struggling to see how you arrived at 120 mm...

[Carolyn]

Slow down.  Yes I've found it does not clear the exhaust maniold.  Let go of your subframe fear.  Can we please, do one thing at a time?  Pulley size!

BTW It was the inlet we were looking for.  I have the outlet stuff.  How do you propose to deal with the fact that the supercharger fouls the subframe?

[lamcote]

1.6l is 0.88888 of 1.8l
138.7/65.5 = 2.12 and 135/120 = 1.125
1.125/2.12 = 0.53
10.5psi * 0.888 * 0.53 = 5psi
Assume our layout is 5% less efficient than the OEM Mini
5 * .95 = 4.7psi

That spins the SC at 7,200 at 1zz peak power

[lamcote]

I meant the tall wide pipe that sits on top of the SC.

[Carolyn]

TARGET RPM?  That is the inlet.  Now... pulley.

[lamcote]

No, that is the outlet, it connects the SC to the intercooler positioned on top of the Mini engine.

See post at 8:51am for the 120mm pulley calcs.

[Carolyn]

I've just been outside and spun the SC in the direction of rotation of the engine.  It blows out the bottom.

[lamcote]

The air goes up round the outside of the screws against the case wall, not squeezed down between the rotors in the middle, so it actually comes out the top.

[Carolyn]

Just checked - you're right. Now pulley.

[lamcote]

See post above at 8:51am for 120mm calcs.

Here below:

1.6l is 0.88888 of 1.8l
138.7/65.5 = 2.12 and 135/120 = 1.125
1.125/2.12 = 0.53
10.5psi * 0.888 * 0.53 = 5psi
Assume our layout is 5% less efficient than the OEM Mini
5 * .95 = 4.7psi

That spins the SC at 7,200 at 1zz peak power

[Carolyn]

Have you accounted for loss of SC efficiency at 7,200 rpm?

[shnazzle]

Some 2zz injectors just came up for sale for 70 quid.
 l viewtopic.php?f=37&t=59416&p=691910#p691910 l

[Carolyn]

That's handy.

[lamcote]

I am assuming that the SC makes about straight line boost with engine revs in the Mini. It produces max torque all the way from 1,700 - 4,500rpm so it must be pretty efficient at those revs. So if the Mini produces decent boost at 3,400 engine rpm we should get the same kind of performance at 6,400 engine rpm?

[shnazzle]

That's handy.

Well the rest of this conversation is out of my league so figured I'd contribute SOMETHING  s:D s:D  haha

[Carolyn]

Lamcote.  The best I can find off the shelf is a 96mm

[shnazzle]

Lamcote.  The best I can find off the shelf is a 96mm

Essex2Visuvesi offered to have a look at a custom one, in case that post was missed in the frenzy
 l viewtopic.php?p=691884#p691884 l

[Carolyn]

BTW  To use the stock outlet, the SC has to be moved a further 25 mm form the engine.  No problem -except even more reason for the subframe.  Well if you're convinced and I think you've convinced me about 120mm well have to make one.  Please explore that kind offer.

I'm away for the day now.

[lamcote]

If my other calcs are anywhere near, the 96mm pulley would give:

1.6l is 0.88888 of 1.8l
138.7/65.5 = 2.12 and 135/96 = 1.4
1.4/2.12 = 0.66
10.5psi * 0.888 * 0.66 = 6.1psi
Assume our layout is 5% less efficient than the OEM Mini
6 * .95 = 5.8psi

That spins the SC at 8,960 at 1zz peak power.

That could deliver c.200bhp so (in line with my previous logic!?!?) the ideal injector size would be 320cc. BUT my calcs/assumptions can't be THAT accurate so 310cc may still do.

Do we go for it with 96mm pulley and 310cc injectors?

[shnazzle]

Does that assume the 310s are running at 100%? That's obviously a bit sketchy

[lamcote]

No, about 92.5%. I always build in margins!


The only reason I suggested 120mm was to give a very safe boost level. If getting a 120mm pulley is prohibitive then 96mm isn't too much more. It's about 5.75psi rather then 4.5psi. That may not be too far off the mark? Who knows, it could even work out better if we try it??

[Carolyn]

Last shot before I get in the shower.  We aren't that interested in 6,500 rpm performance anyway....

[shnazzle]

Last shot before I get in the shower.  We aren't that interested in 6,500 rpm performance anyway....

That's definitely true for me.
I'm very interested in this kit even if it barely hits 200hp, simply for the power delivery UP to about 5000.

[lamcote]

No we're not, I agree, but for this to have any chance of working without a piggyback we need to manage to match the airflow to the fixed fueling levels we have (produced by the bigger injector size coupled with the standard non adjustable map), rather than the usual way which is to set your injectors to match whatever your airflow is, by using a piggyback.

It therefore needs to work across the whole rev range, otherwise it probably won't work anywhere.

We are sort of reverse engineering the fuel mapping.

Ignition timing is then the big issue for me, but the lower the boost, the less this may matter. Hence, another reason for the suggestion of a 120mm pulley.