supercharger tech

[anglia4]

Does anybody know the tech about doing the relevant calculations to spec a supercharger?

I've been surfing ebay and Eaton M90 superchargers are cheap as (would be seriously tight to fit in the anglia bay but hey thats not the point!)

I've been on the eaton website and found the performance map for them:

http://www.eaton.com/ecm/groups/public/@pub/@eaton/@per/documents/content/ct_128485.gif

I've got the pressure ratio part sorted, its the absolute outlet pressure divided by the absolute inlet pressure. So for about 11psi you need a pressure ratio of about 1.7.

The green line is the rpm of the supercharger and the blue lines are the efficiency.

Is it right to calculate the flow rate as just the engine capacity multiplied by so many rpm?

I.e my car is 2.0 litre so at 6000rpm is it right that it would be consuming 12000 litres per minute?

so 12 cubic metres per minute or 720 cubic metres per hour?

meaning that for my application i would need the charger spinning at 9000rpm and have an efficiency in the charger of 59%??

[anglia4]

all right then i'll try find out for myself again

from the info i have gathered from this site (god only knows how reliable it is):

http://ezinearticles.com/?Supercharger-Calculators-Explained&id=3201927

according to this it looks like horsepower is proportional to the amount of air that the engine gets. So they base it around a density ratio.

If my engine is originally 150hp and i want 220hp then i have a density ratio of 220/150=1.46666

If T2 is the compressor outlet temp in degrees kelvin

and T1 is the comp inlet temp in deg kelvin

then T2/T1 = Pressure ratio/density ratio

so if the air inlet is at ambient ~25 deg c then T1 is about 300K

and if the air outlet is intercooled to keep it within 50 deg so T2 is about 350K

350/300 x 1.46666 = pressure ratio

so the pressure ratio is about 1.71

That relates to a boost pressure of about 10psi which seems realistic.

and then using the horsepower/airflow calculator on this page:

http://www.rbracing-rsr.com/turbotech.html

for 220hp i would need 0.1557 cubic metres per second which is 560 cubic metres per hour

Dunno how much i trust that calculator though coz it doesn't take into account any pressures, it gives it in either cubic meters per second or kg per second but the conversion between them depends alot on the pressure so i don't really trust that. will keep searching.

So far anyway though it looks like i'm on a useable part of that eaton performance chart

[anglia4]

ok flag that last post!

http://www.eaton.com/EatonCom/ProductsServices/PerformanceProducts/Products/Superchargers/

the calculator on this page for eaton superchargers is awesome! gives theoretical dyno charts

[Roman]

"I.e my car is 2.0 litre so at 6000rpm is it right that it would be consuming 12000 litres per minute?"

Half that... Because it's a 4 stroke remember!

Which makes the calcs easy, 5000rpm = 5000litres per minute.

*However* That is assuming that your engine can consume air with 100% efficiency currently, which is unlikely.

Probably 70% or 80% of that is a safe bet for actual current air consumption in the engine, maybe less if it's something of a particularly oldschool sort of design.

[anglia4]

Half that... Because it's a 4 stroke remember!

ah good point!

[RUNAMUCK]

Also, dont assume that your blower will pump it's ctual displacement per rev either. A blower will only ever be within so many % effeciency.

[cute wee gem]

Will running more than 8psi NON-intercooled be worth the effort of making a pulley up? (say 10-12)

Will changing the pulley size change anything or will the ABV/something else regulate the boost?

For a stock 1ggze (sc14)

[anglia4]

Also, dont assume that your blower will pump it's ctual displacement per rev either. A blower will only ever be within so many % effeciency.

yeah the blower performance map has efficiency plots on it

[eke_zetec_RWD]

Will running more than 8psi NON-intercooled be worth the effort of making a pulley up? (say 10-12)

Will changing the pulley size change anything or will the ABV/something else regulate the boost?

For a stock 1ggze (sc14)

no, most likley kill your mtor without a intercooler

[Jase]

add water/meth injection to cool the charge is my plan no intercooler

[Testament]

Will running more than 8psi NON-intercooled be worth the effort of making a pulley up? (say 10-12)

Will changing the pulley size change anything or will the ABV/something else regulate the boost?

For a stock 1ggze (sc14)

no, most likley kill your mtor without a intercooler

If your running pump fuel you could do it but you would have to pull the timing back and probably that amount of boost on a 2L will have the SC14 starting to get quite inefficient.

You are much better off to run less boost and more timing, will result in better engine response and less heat output.

if you ran methanol it would be fine. but thats another ball game alltogether.

the M90 works ok on a 2L, M62 would also be ok

for example a guy on one of the fiat forums had a 2L 8v fiat twin cam in a carbon fibre morris minor running an M90

"To give you guys an idea of what the package is capable of, the morris made 274 rwkw at 17psi with a best 1/4 of 11.4 @141mph - Prior to my engine being destroyed in a certain fire, i had just completed a tune at 23 psi - and was awaiting bigger injectors. "

So yes crappy old roots technology does still actually work.