right so let me outline todays findings.
first though, see transcripts for emails sent between myself and a very helpful person at Eaton called Kaid:
________________________________________
From: Patrick Firmager
Sent: Tuesday, December 15, 2009 7:49 AM
To: Marshall, SuperCharger
Subject: Which supercharger is fitted to...
Hello
I was hoping you could
help me with a quick piece of information...
Which model supercharger is fitted to the Volkswagen 1.4 TSI “Twincharger” engine?
Also, could you confirm that the M45 model supercharger is fitted the 1.6 Mini Cooper S?
Thanks,
Patrick Firmager
________________________________________
From:
[email protected] [mailto:
[email protected]]
Sent: 15 December 2009 15:22
To: Patrick Firmager
Subject: RE: Which supercharger is fitted to...
Hello Sir,
The 1.4L TSI engine uses an Eaton M24 supercharger specifically designed for VW. It is unique as the design incorporates step gears to change the drive ratio within the supercharger. Also you are correct as the M45 is the unit that is used in the 1.6L Mini Cooper S.
Best regards,
Kaid
________________________________________
From: Patrick Firmager
Sent: Tuesday, December 15, 2009 10:33 AM
To: Marshall, SuperCharger
Subject: RE: Which supercharger is fitted to...
Hi Kaid
Thanks for getting back to me, much appreciated!
Why does the 1.4TSI use an M24 instead of an M45, and why does it need to have step gears to change the drive ratio?
Cheers,
Patrick
________________________________________
From:
[email protected]
Sent: 15 December 2009 15:34
To: Patrick Firmager
Subject: RE: Which supercharger is fitted to...
The goal of the ”Twincharged’ engine was to use a supercharger to create boost at low engine RPM while the turbo charger was still trying to reach efficient rpm from exhaust gas. A faster rotating M24 was smaller in size and provided more efficient airflow than a slower rotating M45. The step gears allows the M24 to rotate towards maximum RPM at only 3500 engine RPM. Without the step gears the pulley would be much too small to fit on the shaft and would not have enough area for the belt to contact.
Regards,
Kaid
________________________________________
From: Patrick Firmager
Sent: Tuesday, December 15, 2009 10:49 AM
To: Marshall, SuperCharger
Subject: RE: Which supercharger is fitted to...
Ah I see. Just a couple more things, sorry to be a pain...
My understanding is that the supercharger connected to the 1.4 TSI cuts out at between 3000-3500rpm via the use of an electromagnetic clutch.
What is the peak boost and maximum RPM of the M24 at 3000-3500rpm? What is the maximum recommended operating speed and boost of the M24 supercharger?
I am trying to find some way of improving the performance of the supercharger on the 1.4TSI and the traditional methods (fitting a smaller pulley and belt to increase supercharger speed and thus boost) to seem to be viable at the moment... any thoughts/ideas?
Cheers,
Patrick
________________________________________
From:
[email protected]
Sent: 15 December 2009 15:58
To: Patrick Firmager
Subject: RE: Which supercharger is fitted to...
The maximum speed at the pulley is 9000 rpm (rotor speeds at 17370) due to the internal step ratio of 1.93. I do not know the theoretical boost at that speed as that is a function of the engine system. I do know that the unit will flow 360 m^3/hour at 1bar gage pressure, 17370 RPM. 1 bar gage pressure at STP is the maximum validated pressure for this unit.
I do not know the pulley to crank ratio so I am unsure how fast the unit is rotating when it disengages at 3500 rpm…
Regards,
Kaid
________________________________________
So what have we learn't?
1) after pouring over many sites and
reviews, a roots type supercharger is terribly inefficient... it runs at about 60% efficiency as apposed to a twin screw which is around 90%. this leads to an excess builup of heat which makes the extra air your forcing into the cylinders less dense... which is bad for power production. see link for a detailed comparison of heat (albeit i think it may be slightly bias :S)
http://www.kennebell.net/techinfo/gener ... atalog.pdf.
2) basically, a twin screw type supercharger would be much better. after going over a few websites, the winner appears to be a charger produced by lysholm, a subsidiary of opcon (see
http://www.opcon.se/index.asp?sPage=1&langID=2&cID=14 for product range). i've not got as far as pinning down which model would best suit the 1.4tsi... i have a feeling it won't be as simple as using the usual manufacturer's recommended approximate engine capacity to charger size charts...
3) doing it on the cheap, a smaller pulley and shorter belt would probably work; albeit it hasn't been developed yet and i'm struggling to find anyone with enough expertise/experience/interest in this type of thing to wanna try it out. also, from my link to kennebell.net above, around 12psi will heat the air to over 250degC... which again is bad. HOWEVER! there is a saving grace! the 1.4tsi comes equipped with a handy dandy intercooler which would
help to drop those temperatures significantly, more so if (like me ) you have a Forge front mounted intercooler installed too. also, having read a fair bit, whenver the cooper s' went for a smaller pulley and belt, the spark plugs were recommended to be changed to cooler NGK iridium plugs. this was to detonation or worse... the plugs melting :S. On top of all this, many were recommending water injection and spray bars to further try and cool the charged air. oh by the way, the maximum operating pressure of the M24 is 14.5psi (also known as 1bar)... just imagine the charge air temp and that boost arghhhh!!!
4) if you can spare the money and the heartache, a twin screw supercharger conversion would probably be a better plan. the only
problem being that:
a) it is totally unmarked territory
b) the twin screw's are more expensive
c) they have a slightly shorter lifespan and VW sure won't be
servicing them...
d) no clue how the electromagnetic 3500rpm cut-off clutch is implemented so again, no idea how you connect the two componants together.
e) boring stuff like engine bay location and mountings have to be addressed. also the supercharger is a b****** to get to as its under and behind the engine (i think...)
f) unsure which model twin screw is suitable.
at least you would recieve the same kind of power delivery as at the moment, as the whole point of the 1.4tsi is that the supercharger gives that direct "hit" of power and torque to get you by as the turbo spools up. this is why a roots supercharger has been used, a centrifugal stlye charger, such as a rotrex, has power delivery which increases with engine rpm, meaning you have bugger all low down the rev range... twin screwsuperchargers also give immediate boost.
final summary, you have two choices if you wanna improve your supercharger:
1. keep roots style eaton m24, get smaller pulley and belt developed, install a front mounted intercooler (and maybe a spray bar), replace spark plugs with cooler iridium type ones, alter vehicle mapping to make use of extra air.
2. replace charger with twin screw style lysholm model, get just about everything involved with adding a supercharger to an engine developed for this application, alter vehicle mapping to make use of extra air.
So yeh... an thoughts?
which would you go for? actually on second thoughts, lets have a vote!
