rdodger
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| posted on 10/1/15 at 11:27 AM |
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I would say you really don't want to over spin the charger.
It leads to a large increase in inlet temps and much reduces the life of the charger.
130-62 will be about perfect.
If you will have a requirement to bleed boost then you have started with a charger that is too large. M45 may be better for your application.
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Sierra
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| posted on 10/1/15 at 12:26 PM |
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The dump valve will not be because I'm running too much boost but to stop the back pressure on the charger when throttle is snapped shut. Just
as you described it won't be good for the charger as you've experienced.
The reason for the m62 is because it's more or less the same size but requires less spinning for the same air
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bi22le
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| posted on 10/1/15 at 12:29 PM |
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Thanks for your sharing your experiences.
The idea of using the refrigeration theory (I am sure it has a more relevant term, condensing?) in this case could be floored as the pressure drop is
so small. 10-14psi is not a huge amount. 30psi would probably be enough. Either way, Jeffw has proven it does not work!
I still like the idea of using a larger SC (and I already have a M62 to use!) so I have the luxury of spinning it slower and keeping it more
efficient. I want to be running 10psi+ and looking at the mini cooper s boys, and MX5 they are seeing only half that with the M45. Not considering
head efficiency as correctly pointed out by Mark.
As with all of our systems, they are different and have a variety of set ups. I am aiming for north of 230. Seeing that the previously stated lower
powered (stock) and less efficient MX5 achieved 220 I think I am realistic. 280 would be nice though. . . . .
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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rdodger
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| posted on 10/1/15 at 02:24 PM |
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quote:
Originally posted by Sierra
The dump valve will not be because I'm running too much boost but to stop the back pressure on the charger when throttle is snapped shut. Just
as you described it won't be good for the charger as you've experienced.
The reason for the m62 is because it's more or less the same size but requires less spinning for the same air
Sorry sierra yes that's correct. We seem to be having 2 conversations now.
In terms of having a recirc as Jeff says it can lead to higher inlet temps as the air you are recirculating has already been through the charger.
I'm not sure the effect of the air expanding into a chamber before the charger would be enough to cool the inlet as bi22le proposes. I kind of
doubt it or it would already have been done.
My mad idea a few years ago was to use the aircon on my mx5 as a kind of charge cooler. It sounded good until I was reminded that the AC compressor
shuts down at WOT.
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jeffw
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| posted on 10/1/15 at 02:36 PM |
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I do think we are confusing wastegate (to bleed boost off at a certain pressure and controlled by the ECU with a spring failsafe) and a dump or
BOV/recirc valve which opens to atmosphere when you lift off the throttle, this is done to stop compressor stall.
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Sierra
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| posted on 10/1/15 at 02:43 PM |
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Yes sorry that might have been confusing the conversation haha.
I won't be running a wastegate on my setup only a dump valve. As already said it's the pulley size that will control the amount of boost
the charger can produce so no real need for a wastegate
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mark chandler
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| posted on 10/1/15 at 03:28 PM |
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And no need for a dump valve on a rootes charger as its displacing air, not pressuring it so the recirculating valve is all you need.
With a spiral wound charger like a Whipple or compressor wheel like rotex it is pressuring the air inside the charger so a dump valve is required as
you have a stored volume of compressed air to lose.
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Sierra
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| posted on 10/1/15 at 04:02 PM |
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From my sketch where would you put the recirc valve?
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jeffw
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| posted on 10/1/15 at 05:03 PM |
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quote:
Originally posted by mark chandler
And no need for a dump valve on a rootes charger as its displacing air, not pressuring it so the recirculating valve is all you need.
With a spiral wound charger like a Whipple or compressor wheel like rotex it is pressuring the air inside the charger so a dump valve is required as
you have a stored volume of compressed air to lose.
This....
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Sierra
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| posted on 10/1/15 at 05:30 PM |
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Wow I'm just bashing my hard against the wall with confusion, stupidity.
So eatons just push air not pressurise it, therefore there's never pressured air before my tb so no need to get rid of any air or worry about
back pressure going back into the charger when off the throttle.
Is the below picture what you mean by recirc valve
If so the valve is open on light or no throttle and shut when WOT. The charger would still be spinning and pushing air even at light/no throttle so
what benefit has it?
Also if there's no air to dump pre tb how come loads of people that have installed these chargers fitted dump valves that do dump air?
https://m.youtube.com/watch?v=Ghjc_I1wQ-g
Sorry if it's all stupid questions. I'm just trying to get my head around it and just when I think I've got it, it's gone haha
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rdodger
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| posted on 10/1/15 at 06:12 PM |
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That's a bypass from a MINI.
A recirc valve and dump valve are basically the same thing.
Whatever you are using to pump the air, Rotrex, Eaton or Turbo, when the throttle closes you need to get rid of the air between your pump and the TB.
Why? Because the back pressure will at best stall the pump at worst damage the pump.
A recirc valve as the diagram is a quiet way of doing it, but can increase inlet air temp.
A dump valve will give the whoosh and confuse a MAF sensor if you have one.
The MINI bypass lets air past the SC when the inlet manifold pressure is 0 or in vacuum, so no need for a dump vale/recirc as the bypass does the same
job. These set ups tend to be used when the TB is pre charger.
The dump or recirc valve will also connect to the inlet and of course be open when manifold pressure is 0 or in vacuum.
So any of the three does the job.
I hope that helps 
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Sierra
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| posted on 10/1/15 at 07:35 PM |
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Many thanks that's how I saw it. So with my tb being post blower and recirculating already being proved to create heat my only real option is a
dump valve between intercooler and tb.
Just out of interest how does it work on idle when the charger is still spinning and pushing air towards closed tb, will the dump valve open to dump
the air? Or will it never get to the point where there's to much air to dump?
Also with the above m45 bypass which I've also seen on many charger setups when closing the throttle how does it get rid of the air post blower?
Does it just circulate it back to pre blower, if so then isint all that air still there in the system and not eliminating the problem of too much air
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rdodger
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| posted on 10/1/15 at 07:40 PM |
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There won't be too much air to dump as by the time you get to that point you will into boost.
As for the M45 question................ er mmm............ yes I guess so
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mark chandler
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| posted on 10/1/15 at 09:56 PM |
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In the picture above the throttle body goes on the end of the 90 degree mandral bend.
If you run an air to water intercooler and keep the inlet tract short you will not need a secondary throttle body, if you duct to the nosecone and
back with an air to air then you will want one, They just need synchronising and may cost a little power as another restriction for the air to go
through.
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mark chandler
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| posted on 10/1/15 at 11:35 PM |
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They work on vacumn drawn just after the throttle body, so throttle plate shut you get a high vacumn and the bypass valve is open, medium to heavy
throttle and you have low vacumn so it shuts.
When open the charger is circulating air outlet to inlet, dip your hand in a bowl of water and swirl the water around, it takes a lot of energy to get
up to speed but not much to keep it going, the same applies with the charger so at light throttle valve open it is only drawing a few HP to spin. Open
the throttle and the valve closes, air is now backed up in the inlet (boost) so the charger is now drawing a lot more HP off the crank as it works
against the resistance pushing air into the engine.
HP pinched off the front of the engine is HP you cannot get out the back, I believe my M90 may be pulling as much as 50hp at full throttle which is
why you need a good quality mounting.
You could remove the bypass valve, the car would now consume lots of fuel as it try's to drag air in as well as force it into the engine at
light loads.
Just get one off a mini you should be fine 
[Edited on 11/1/15 by mark chandler]
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Sierra
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| posted on 10/1/15 at 11:53 PM |
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Again many thanks. You've been very patient with my lack of knowledge and explained it very well. Definitely owe you a beer 
I understand that it benefits from recirculating already spun air but I wonder if this benefits as it hot from the charger, instead of the charger
just spinning fresh cool air. I imagine there's probably no way of ever establishing which is best.
Also with just a recirc as above with no dump valve when closing throttle the air will surely just be forced back so some hitting the charger and I
imagine some escaping out the air filter (seeing as my tb is at the plenum)
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mark chandler
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| posted on 11/1/15 at 09:20 AM |
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With a rootes it displaces air, when you close the throttle it just gets consumed by the engine as there is no excess air to lose.
At low throttle openings the air will be a little hotter as it is being circulated, remember only a few HP is being pulled off the crank so this heat
is minimal once it's been passed by the intercooler, also you are not after making max HP, a few degrees extra heat does not matter.
When you are going full throttle with a rootes charger it consumes a lot of power which is turned into heat, screw or turbine type chargers draw may
30%-50% less power for the same level of boost so are far more efficient and should ultimately produce more power as less being drawn off the crank
and it's cooler.
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Sierra
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| posted on 19/2/15 at 01:32 PM |
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Small update.
I'm still going a head with the upgrade of the m62 charger. I've found an intercooler that I think I can work with by angling both the
radiator and intercooler, tb wise I've got 2 from standard fords one with a slightly smaller tb plate but larger diameter hose section. The
other has a larger tb plate but smaller hose section, which one would be best?
Also I imagine I'll have to get new injectors as my current ones are the beige 250cc. I'd rather get some and take them with me when the
mapping is done so not to waste time and have to go back.
Thing is I'm not sure which ones to go for as I don't know what power I will get, will getting ones that are too large not work as
well?
The power could range from 200bhp to max 300bhp (one day)
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theduck
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| posted on 19/2/15 at 01:51 PM |
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Too small will result in not enough fuel, too large will mean that the injector is never working efficiently.
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beaver34
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| posted on 19/2/15 at 02:04 PM |
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i use astra vxr blue ones, around 440cc i run 3.5 bar static 1-1 raising rate fuel pressure they are good for for 300bhp with no issues
they are also cheap £100 new for a set
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scimjim
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| posted on 19/2/15 at 02:13 PM |
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injector calculator here
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Sierra
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| posted on 19/2/15 at 09:30 PM |
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Thanks for the info, according to that site for 250bhp I'll need 450cc and for 300bhp 540cc. If I went for the 540cc then this should cover me
but will they still be too big if I only went with say 250bhp.
Also when searching it's got ohm impedance, which would/wouldn't work on a blacktop?
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beaver34
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| posted on 20/2/15 at 08:21 AM |
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quote:
Originally posted by Sierra
Thanks for the info, according to that site for 250bhp I'll need 450cc and for 300bhp 540cc. If I went for the 540cc then this should cover me
but will they still be too big if I only went with say 250bhp.
Also when searching it's got ohm impedance, which would/wouldn't work on a blacktop?
thats not true, 440cc are fine for 300bhp
injectors are rated at say 3.5bar at 440cc but as you increase fuel pressure with boost pressure you get more flow
thats how i understand it anyway
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Oddified
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| posted on 20/2/15 at 10:29 AM |
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quote:
Originally posted by beaver34
quote:
Originally posted by Sierra
Thanks for the info, according to that site for 250bhp I'll need 450cc and for 300bhp 540cc. If I went for the 540cc then this should cover me
but will they still be too big if I only went with say 250bhp.
Also when searching it's got ohm impedance, which would/wouldn't work on a blacktop?
thats not true, 440cc are fine for 300bhp
injectors are rated at say 3.5bar at 440cc but as you increase fuel pressure with boost pressure you get more flow
thats how i understand it anyway
Not quite, the extra fuel pressure only compensates for the pressure in the manifold (which is working against the injector flow) so the flow stays
the same, ie, balances out.
440cc would be marginal for 300bhp even with a duty cycle of 100% which isn't recomended.
Ian
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beaver34
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| posted on 20/2/15 at 11:01 AM |
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quote:
Originally posted by Oddified
quote:
Originally posted by beaver34
quote:
Originally posted by Sierra
Thanks for the info, according to that site for 250bhp I'll need 450cc and for 300bhp 540cc. If I went for the 540cc then this should cover me
but will they still be too big if I only went with say 250bhp.
Also when searching it's got ohm impedance, which would/wouldn't work on a blacktop?
thats not true, 440cc are fine for 300bhp
injectors are rated at say 3.5bar at 440cc but as you increase fuel pressure with boost pressure you get more flow
thats how i understand it anyway
Not quite, the extra fuel pressure only compensates for the pressure in the manifold (which is working against the injector flow) so the flow stays
the same, ie, balances out.
440cc would be marginal for 300bhp even with a duty cycle of 100% which isn't recomended.
Ian
odd as i run 340bhp and i am not maxed out, must be near though
[Edited on 20/2/15 by beaver34]
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