Yes, I was thinking about that after I posted. I was perhaps extrapolating too much, as I based my assumptions on data from one model (M45), then extended that to another model without checking the figures.

I stand corrected , (and quite pleased ) as it seems my choice of M45 may result in less of a temperature rise than a bigger blower

Its been good to revisit this however, and makes me even keener to get the thing running to see how theory translates into practice

And datto-510, thanks for the microtech offer, but I've just laid down my hard-earned dollars for a Haltech E6X. Group buy on DatNet at a very good price.

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

Yeah the basic equation is

Discharge temp celcius = ((Ambient air in Kelvin * PR^0.283) -273)/CompEff

Here are where everyone can find the maps for the Eatons, links to the side.

http://automotive.eaton.com/product/eng ... rs/M90.asp

That 200cfm figure is right in the meat of the efficiency of the M45, so it kind of makes sense that the smaller unit would be a good idea. I think where the bigger supercharger idea might really come into its own is looking at when the M45 is at its redline at 14000rpm and passing 320cfm @ 10psi, with a temp rise of 175F. The M90 is only doing 7800rpm under the same conditions with a temp rise of 160F. Looking at the hp loads to drive them under these conditions the M45 is taking 26hp vs the M90 at 22hp - I guess that would make sense in that the power to heat the air more has to be coming from somewhere (probably other losses involved here as well).

So I guess in an ideal world if you knew that at redline your motor was taking in x cfm at 10psi you could neatly look at these maps and pick the supercharger that could pass enough air at that pressure and is just near the upper edge of its efficiency, that way you would probably be more likely to end up with a supercharger that is pumping efficiently throughout the bulk of your rev range, and would be producing decent boost as low as possible.

the exhaust gas analogy was just a very rough guide to explain the idea behind the scale of the comparison.

both engines put out the same amount of gas, but one isn't working as hard to do it and therefore is operating cooler.

that's pretty much it - no VE comparisons there, or anything like it, at all.

but the stuff you've just posted regarding bigger chargers is very interesting indeed! bar the maths side of it, can someone explain why this is?

_________________
frankenstein projects R us.

The Republic of Western Australia -
Propping up the Nation's Economy since 1901.

Yes there's always more to selecting a huffer than just the rise in charge temp. The parasitic losses contributed by pumping losses, dynamic losses, friction losses, etc have to be factored in to get the net gain.

Selecting a compressor that matches maximum efficiency with peak torque is desirable, but if it doesn't match the system curve performance is compromised.

Just the kinetic energy to provide motion will largely become sensible heat. As sensible heat rises so too does sensible temperature. The larger the compresor the larger the mass and therefore the larger force required. The compressor efficiencies then come into play.

and on comes the light bulb.....nnnnnnNOW.

_________________
frankenstein projects R us.

The Republic of Western Australia -
Propping up the Nation's Economy since 1901.

Well, I've just got one thing to add -

Where were you all in May

My initial post elicited a handful of reponses, now there's pages of really useful discussion

Just kidding - I'm glad that my choice of M45 seems to get the stamp of approval from quite a few people. Although I'm still a bit worried that I'm pushing it a bit hard at 2.2 : 1 drive ratio

I suppose it'll be fairly easy to get a smaller crank pulley if that proves to be the case.

And hey, I can always get one of the 19% smaller blower pulleys designed for the Mini if I think I can get more out of it once its running

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

My mum lives in the UK at the moment . roughly how big and what do these chargers weigh?
might have to see if she can fit one (or a couple) in a suitcase on her way out here next time
no idea when that would be though...

_________________
Dave W

The 1600

Recommended traders: Nissanman, pro240c, 2door510, Datsport, mkyle, Green510, Um_510, jdmdatsun510, Ludachris

Dave,

you were saying that it would have been cheaper to fit a N/A SR20.
would you mind sharing a rough budget with the rest of us ?

cheers
Jeff

Or buy one off eBay, get it delivered to your mum in the UK, then she can post it on to you

And by the miracle of modern science (well, by finding a PM that I posted on a mini forum), I can tell you the exact measurements.

The box it was shipped in was 25 x 25 x 44 cm. This was the original box the JCW supercharger came in, so still had the correct shaped packaging to protect it. The weight (by my not-totally-accurate bathroom scales) was a whisker under 10kgs.

Most of the ones I watched on Ebay seemed to finish at just over 100 pounds. Some where cheaper, but as you said I had to settle on one of the few I found that would post to Australia.

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

i was actually thinking of just sending her out to pick it up, and then getting her to bring it back on the plane with her, as i'm in no rush for it really, so may asweel save as much $$ as i can getting it. My plans are for a blown sr20de
i'm watching 8 at the moment, any the price varies quite a bit too. i'll let you all know the average once they're all finished.

_________________
Dave W

The 1600

Recommended traders: Nissanman, pro240c, 2door510, Datsport, mkyle, Green510, Um_510, jdmdatsun510, Ludachris

Well, that was a bit of a guess.

I'll need all the usual efi into old car stuff no matter whether its an L18 or SR20 - new fuel lines, efi pumps, upgraded brakes, etc, etc, so no difference there.

For an SR20 N/A, I've seen them advertised for under $2 grand, including everything you will need - engine, gearbox, wiring, ecu and so on.

For the L18, the big expense is setting it up for programmable injection and ignition.
Number one big expense - an ecu. I just paid $1060 for a new Haltech E6X, so thats half the SR20 budget gone.

The cost of the blower ($250)

The cost of ignition (another few hundred for coils and ignitors, plus whatever else I use - Hall sensor, CA18 CAS ??)

Blower bypass valve (genuine Mini for $150)

Ijectors and fuel rail (I got them cheap but need to do a lot of work to make it fit, say $50)

Custom inlet manifold (maybe another $100 in materials, plus lots of my time)

Probably custom extractors to fit with the custom inlet and the blower mounted on the same side of the block (Again, maybe $50 or so for materials, plus even more of my time)

Then I will have to factor in a full rebuild for the L18, including making it a bit more robust to handle the phenominal extra power it will now generate The SR20 should be in good condition, just throw it in and off you go without needing to open the motor. (Say another $1,000 at least)

Then I still need to find a good gearbox for the L18 (comes with the $2000 SR20 package).

It will all add up, or I could have just paid my $2000 for the SR20

Ohh, one other factor that I haven't included is the cost of a fitting kit. Reason being that I will still be using a 200B x-member for the handling benefits. So, no extra cost here (for me). You could save this cost with the L18 conversion by just using the original front end.

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

I ordered "supercharged" from the states this morning

I cant remember where i got the following from, but the may be of interest (i have been thinking about doing this for a while)

bugger - theres a 3 image limit - read this one first !

there is some more info & pics here http://ozdat.com/forum/viewtopic.php?t=4958&highlight=