Craigorypeck
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| posted on 5/5/12 at 11:42 AM |
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How fast can you spin an eaton 45??
Apparently 14000 is the max on an eaton m45??
With my current gearing to suit the 14000 sc rev limit the engines rev limiter is set at a modest 6300rpm..
I could go a larger SC pulley to allow a higher engine rev limit but dont want to loose the 6psi boost I have gotten used too. I'd loose over
half the boost probably more to be able to rev to 8000 and keep within the SC guidelines.
My engine is capable of 8000 rpm but up there the supercharger will be going 18200rpm.
Could I run engine to say 7500, with charger at 17000???
Some say that you can spin them way faster than the book says and they just become inefficient... true? it currently makes constant boost to the rev
limit, doesn't drop off at all
Anyone have any hard evidence for me??
A bigger charger is not an option.. space- no, time- none, money-gone!!
Its bolted to a cosworth YB that was built NA BTW.
Thanks
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flibble
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| posted on 5/5/12 at 12:12 PM |
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Mine ran at 17500 max with no obvious ill effects on an MX6 for a few months until I sold it, no doubt it was not entirely healthy for it and no good
for power/intake temp but it was a 'ghetto' setup anyway and I rarely hit the red line :\
[Edited on 5-5-12 by flibble]
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MakeEverything
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| posted on 5/5/12 at 12:46 PM |
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quote:
Originally posted by Craigorypeck
Apparently 14000 is the max on an eaton m45??
With my current gearing to suit the 14000 sc rev limit the engines rev limiter is set at a modest 6300rpm..
I could go a larger SC pulley to allow a higher engine rev limit but dont want to loose the 6psi boost I have gotten used too. I'd loose over
half the boost probably more to be able to rev to 8000 and keep within the SC guidelines.
My engine is capable of 8000 rpm but up there the supercharger will be going 18200rpm.
Could I run engine to say 7500, with charger at 17000???
Some say that you can spin them way faster than the book says and they just become inefficient... true? it currently makes constant boost to the rev
limit, doesn't drop off at all
Anyone have any hard evidence for me??
A bigger charger is not an option.. space- no, time- none, money-gone!!
Its bolted to a cosworth YB that was built NA BTW.
Thanks
You really need to work it all out properly. I spent a lot of time sizing mine to make sure i could get the boost pressures and CFM that the engine
needed.
It all depends what your pressure ratio is, which will then tell you where in the efficiency map your ideal S/C RPM is.
There is a calculation in my blog on the link below to help you out. Its the most recent (latest) post, where i went back and confirmed my original
calcs.
The green line on the map is the RPM, so at 17000 RPM, youre way off. 6000 looks to be optimal to achieve the highest possible efficiency from the
S/C, but it depends on the CFM rate required. Im running at 14,000 to get the CFM needed.
[Edited on 5-5-12 by MakeEverything]
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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Craigorypeck
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| posted on 5/5/12 at 04:08 PM |
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How do i work out Engine Volumetric Efficiency???
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mark chandler
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| posted on 5/5/12 at 05:27 PM |
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Do not forget, spinning at these speeds introduces a lot of heat so you may simply lose power.
Better to get an M90 and spin at its rated speed, you also will need a decent intercooler.
I ported my M90, it has made a significant difference to the car, you get rid of the sharp edges and open up the inlet to gen 5 style.
Regards Mark
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Craigorypeck
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| posted on 5/5/12 at 05:59 PM |
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An m 90 would be best but as said above that not happening. well at least not this year.
I have a pretty big intercooler installed so that will help.
Maybe i can port the m45?? what advantages will that have? more boost? if so I would reduce the ratio then.
The torque I have now is sooo good I'd rather keep that than gain top end where it will rarely be anyways.
But if im gonna pay to get it rolling roaded I wanna push it to 7500rpm.
I can get an air temp into the plenum and keep an eye on temps, when exactly is the boosted air too hot??
Thanks again.
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mark chandler
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| posted on 5/5/12 at 06:17 PM |
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Have a look here
http://www.3800supercharger.net/pulleys.html
High inlet temps force you to retard ignition and lose power, porting does not gain any more pressure as this is fixed to the amount of air that can
be moved by the rotors, what you do gain is less effort required to spin the supercharger and by smoothing the airflow you reduce induced heat in the
charge.
You also need to look at the exhaust, 1lb back pressure costs 1lb boost on the inlet.
Regards Mark
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Craigorypeck
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| posted on 5/5/12 at 07:35 PM |
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cheers guys, as its gonna stayed geared as is I might get a wee shift light from the megajolt to indicate 14000 on the charger, and pee into the wind
from there on! now, I should really get the tps switched over to map. hehe.
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