flak monkey
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| posted on 8/1/15 at 12:54 PM |
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From the welds, looks like it might be steel - is it magnetic? Are the inlet tubes round?
Sera
http://www.motosera.com
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Sierra
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| posted on 8/1/15 at 03:18 PM |
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I don't have a magnet unfortunately but thinking how much it weighs it must be steel. Would they make it out of mild steel or stainless? Only
asking as when I buy the pipe work I can choose either of them.
Oh yes the ports are round, 45mm.
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flak monkey
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| posted on 8/1/15 at 06:31 PM |
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I expect it will be mild steel.
Sera
http://www.motosera.com
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Sierra
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| posted on 9/1/15 at 02:19 PM |
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Just a thought about post or pre charger tb placement. Which would you guys say is better?
On a post charger tb placement when you shut of the throttle the recirculating valve which is pre tb releases the extra pressure back to pre charger,
while at all times the charger is spinning getting fresh air from the air filter.
Now with pre charger tb placement when you shut of the throttle the bypass valve will again release any extra pressure from post blower to pre blower
only this time the charger continues to spin but without any air from outside. Question is wouldn't the charger now produce a lot of heat?
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rdodger
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| posted on 9/1/15 at 04:58 PM |
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If you use a pre charger TB then it will run quieter and cooler. If you then have long pipe runs/ intercooler to the inlet you may have trouble with
lag, unthrottled air, idle droop, stalling etc as there is quite a large volume there.
If you put the TB on the inlet you will probably want to run a dump valve along with the bypass. Back pressure when the throttle snaps shut can damage
the charger. Ask me how I know! The supercharger will also be very loud on part throttle.
A lot of MX5 M45 supercharged owners run dual TB's These are linked together. The idea is to get good throttle response and idle. The draw back
is lots of heat at part throttle plus balancing the 2 is problematic.
I would use the TB on the inlet and have the inlet to the supercharger going through a couple of easy bends and put the filter in a box. That should
help with the noise. Short inlet to the charger with a cone filter works like a megaphone. At WOT both set ups are equally loud.
The JRSC kits for MX5's put the TB on the charger and a dummy TB containing the idle air valve on the inlet. They just used a link pipe not an
I/C and these worked ok. Add an intercooler and it starts to become a problem again.
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Sierra
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| posted on 9/1/15 at 05:12 PM |
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Can I ask why the post charger tb setup creates more heat then the pre charger tb setup?
My supercharger m62 does not have a bypass so I would simply be running 1 recirculating valve. Recirculating from pre tb post intercooler to pre
charger post air filter.
I believe the recirculating valves are closed until you lift off throttle then recirculates back to pre charger.
Is it worth using a recirc valve instead of a blow of valve
[Edited on 9/1/15 by Sierra]
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bi22le
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| posted on 9/1/15 at 05:23 PM |
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Can i ask another question to the pros?
Do ITB make things any easier or different?
I am assuming that the currently discussed MX5 had direct injection and seperate singularTB.
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 9/1/15 at 06:14 PM |
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It's generally thought that ITB's offer little benefit and certainly not money well spent with FI,
With FI you are ramming as much air in as you require anyway. If you fit a charger that supplies the right amount of air to the engine to produce the
required amount of boost..........
If you were using a Rotrex or other centrifugal charger then it might be better as I would imagine throttle response would be better. Marginal though
I bet.
With the MX5 the injectors stay in the inlet manifold and people generally use the standard TB. I did use a larger (70mm)TB but again the increases
are minimal.
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bi22le
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| posted on 9/1/15 at 06:50 PM |
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Thanks for the insight.
I am planning on doing my 4age at some point with an m62. Bigger charger spun slower.
I was hoping to just keep the ITBs, no other TB added, and just have a recirc valve fitted between the plenum and the SC inlet. Boost control via a
set sping in the recirc.
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 9/1/15 at 07:03 PM |
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quote:
Originally posted by bi22le
Thanks for the insight.
I am planning on doing my 4age at some point with an m62. Bigger charger spun slower.
I was hoping to just keep the ITBs, no other TB added, and just have a recirc valve fitted between the plenum and the SC inlet. Boost control via a
set sping in the recirc.
No reason not to use ITB's if you have them, though I might sell them to fund the sc?
With a supercharger boost is controlled by the pulley ratio. An M62 would normally be run at a ratio of 1:2 crank:SC that should keep it within
it's rev range for efficiency and life. The recirc valve is there to dump boost when you close the throttle or cruising it stays open to bypass
the charger.
To give you an idea. On my 1.8 mx5 running an intercooled MP62 on 1:2 ratio I got 240 bhp 220 ftlb which was about as far as I wanted to take the
standard engine. That was about 10psi.
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Sierra
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| posted on 9/1/15 at 07:10 PM |
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The m62 do not have a bypass like the m45, well mine doesn't anyway.
What reason does the bypass stay open and bypass the charger on low throttle, will it cause issues if it just went through the charger all the time?
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Sierra
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| posted on 9/1/15 at 07:47 PM |
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Here's a rough sketch of my setup.
As you can see there's no bypass valve but there is a recirc after the cooler
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rdodger
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| posted on 9/1/15 at 08:09 PM |
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That's fine.
That will work in a similar way. When manifold pressure is in vacuum the recirc valve will be dumping boost.
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Sierra
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| posted on 9/1/15 at 08:14 PM |
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Thanks. Is there any advantage of recirculating the air back to the charger as oppose to just dumping it atmospheric.
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rdodger
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| posted on 9/1/15 at 08:22 PM |
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Depends really on whether you are using MAF or MAP and if you like the chavtastic Psssssst.
If MAF then the ECU can get confused if you dump to atmosphere.
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bi22le
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| posted on 9/1/15 at 10:23 PM |
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Thats the same setup as i was going to do. I under stand that max boost is achieved at max RPM.
I was unsure how the boost will change when the CC is so reduced compared to what the M62 is used to. I like the idea of running the SC as much as
possible then bleeding off the rest using a recirc with a dictated pressure spring. These types of recirc are freely available.
I am hoping to to govern and gaurentee my max boost this way and get more of a turbo boost curve.
As the eaton chargers are basically pumps this will also hopefully do other things. It may reduce inlet temps and reduce parasitic power losses.
I dont know if this Is going to work. I dont anything with this set up and just dreamt it up, but i like it!!
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 9/1/15 at 10:41 PM |
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My experience with the MP62 was it gave about 9psi as soon as it came in then climbed to about 10psi at max rpm.
Unlike a turbo the boost stays pretty constant. The faster the SC pumps the air, the more air the engine is using due to the crank driving the SC on a
constant ratio.
The idea is to match the size of the SC to the engine and run a pulley ratio to keep the SC in it's most efficient window. Bleeding boost is a
waste.
This of course is different with a centrifugal SC.
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Sierra
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| posted on 9/1/15 at 11:43 PM |
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I've currently got a couple of pulleys for the charger, one is 60mm and the other 62mm. So as the crank pulley is 130mm that will give me a
ration of 2.16 on the 60mm and 2.09 on the 62mm. Does anyone know how to work out what level of boost this would produce?
I've been doing some research on the m62 chargers and apparently
Safe continuous rpm is 14,000rpm
14,500rpm ported
Safe Max rpm limit 15,500rpm
Look at gearing car max rpm (7,000rpm) to max charger rpm 15,500rpm
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jeffw
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| posted on 10/1/15 at 07:37 AM |
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quote:
Originally posted by rdodger
It's generally thought that ITB's offer little benefit and certainly not money well spent with FI,
With FI you are ramming as much air in as you require anyway. If you fit a charger that supplies the right amount of air to the engine to produce the
required amount of boost..........
If you were using a Rotrex or other centrifugal charger then it might be better as I would imagine throttle response would be better. Marginal though
I bet.
With the MX5 the injectors stay in the inlet manifold and people generally use the standard TB. I did use a larger (70mm)TB but again the increases
are minimal.
The case for ITBs over single TB is the same regardless of NA or FI. ITBs give a much better throttle response, it has been described as the
difference between being directly connected to the engine (ITBs) or being connected via a bowl of porridge (TB). The ultimate power will be the same
(assuming a TB of sensible proportions) but the finesse on part throttle or throttle pickup is much better with ITB.
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jeffw
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| posted on 10/1/15 at 07:43 AM |
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quote:
Originally posted by Sierra
I've currently got a couple of pulleys for the charger, one is 60mm and the other 62mm. So as the crank pulley is 130mm that will give me a
ration of 2.16 on the 60mm and 2.09 on the 62mm. Does anyone know how to work out what level of boost this would produce?
I've been doing some research on the m62 chargers and apparently
Safe continuous rpm is 14,000rpm
14,500rpm ported
Safe Max rpm limit 15,500rpm
Look at gearing car max rpm (7,000rpm) to max charger rpm 15,500rpm
(7K x 130)/60 = 15167
(7K x 130)/62 = 14677
To get 15500 rpm at 7000 you need a pulley of 58.7mm
Are your diameter measurements at the bottom of the V grooves or the top?
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Sierra
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| posted on 10/1/15 at 09:35 AM |
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The measurements are at the top of the v groove.
I'm not sure if going any smaller will be pushing it and create belt slip
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mark chandler
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| posted on 10/1/15 at 09:37 AM |
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The level of boost will depend upon your engines ability to breath, a poor breathing engine will result in more boost and heat as you are effectively
feeding air into a funnel.
A good analogy is pumping air into your push bikes tyre, pump like mad and it's hard work and the Schrader valve gets hot so just go for a
maximum speed matched pulley and pay attention to the head, inlet tract and exhaust.
You will also find that a rootes charger ability to push air goes off as the rotors spin at high speed so there is no point overspeeding, if you look
at the chart I posted earlier for my DB7 you can see the boost dropping off which clearly demonstrates this as the engine is struggling to breath at
high revs so the boost should increase but the charger has lost efficiency, at low revs the boost is low as the engine can easily pass the air.
I,ll be pulling the head off this car maybe this year, port matching and cleaning up the head, this will result in less boost shown but more power as
the power dragged off the nose of the crank reduces along with inlet charge heat so a win win.
Regards Mark
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bi22le
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| posted on 10/1/15 at 10:12 AM |
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quote:
Originally posted by rdodger
My experience with the MP62 was it gave about 9psi as soon as it came in then climbed to about 10psi at max rpm.
Unlike a turbo the boost stays pretty constant. The faster the SC pumps the air, the more air the engine is using due to the crank driving the SC on a
constant ratio.
The idea is to match the size of the SC to the engine and run a pulley ratio to keep the SC in it's most efficient window. Bleeding boost is a
waste.
This of course is different with a centrifugal SC.
I agree with almost all of this as i am using a larger SC. The M62 is used on engines twice my size so expect it to be able to over boost my car
beyond the efficency of the SC which is why it needs to be controlled. I will try and get the ratio of pulley correct but want a fail safe.
Bleeding boost on the face of it seems silly but let's think about the pump idea. If a pump spins faster than the work required the waste will
allow the pump to spin with relative ease as long as the recirc can flow the volume of air that needs to be wasted.
Another way of looking at it is the torque on the SC pulley would be greatly reduced if you just removed the outlet completely, it would greatly
increase if you just blocked it off 100%.
This meeting in the middle could reduce parasitic losses once the prescribed boost has been achieved. In fact i expect this excess of air to help cool
the charger because the air is being passed through the charger and bleed straight off requiring little effort. I also wonder if the wasted and now
cooled (post IC) decompressed air released into a chamber in front of the charger would reduce inlet temp to the charger, using the refrigeration
principle.
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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Sierra
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| posted on 10/1/15 at 10:41 AM |
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But is the air being recirculated from post intercooler really going to be much cooler than the air coming in pre blower?
Cause if it's not then you'll just be recirculating warm air which wouldn't help the charger
[Edited on 10/1/15 by Sierra]
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jeffw
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| posted on 10/1/15 at 11:21 AM |
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Recirculating is a great way to raise the inlet temp. I originally did this and found if I dumped to atmosphere it dropped average inlet temp by 10
deg C.
I had it as a recirc to cut out the annoying noise but given the temp issue I'm prepared to live with the Max Power wooosh.
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