Small supercharger setup

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Re: Small supercharger setup

Post by PeteH » Fri Jul 14, 2017 11:49 am

In terms of sizing, you (ideally) really want to aim for a supercharger that is designed for a 2.7 litre engine doing 6000rpm, and about 300bhp. That would be the equivalent air flow. The MR2 charger would probably reduce the power :shock: , and the Jaguar charger would have the potential to blow the engine (unless you geared it down, which would make it less efficient). Mercedes did a C320AMG Kompressor with 350bhp, which sounds close.

The Jag is an Eaton supercharger, and you can find Eaton compressor maps here:
http://www.eatoncorp.com.au/Oceania/Pro ... PCT_378413
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Re: Small supercharger setup

Post by 350matt » Fri Jul 14, 2017 12:34 pm

the Jag unit is an Eaton M112 unit and as PeteH say you'd have to gear it down a bit, however the Eaton blowers are the best of the modern PD units and have a broad range

see here for the maps in handy comparison blog
https://www.superchargerforums.com/thre ... r-maps.94/

as you can see you can run the M112 in the 400 lts/ hr range at 0.5 bar boost and still be in the best efficiency zone so this would be a good unit to use I think, especially as they are readily available and quite cheap

ideally the 'best' unit would be a R1320 and these are fitted to the Audi S4

http://www.ebay.com/itm/Audi-S4-S5-A6-S ... 2556194058

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Re: Small supercharger setup

Post by tayfun » Fri Jul 14, 2017 12:43 pm

On this forum we found how to get great BBK for cheap (compare to other options), I'm sure we can handle sorting out SC for 1-2k :D

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Re: Small supercharger setup

Post by Dr. FrankenRex » Fri Jul 14, 2017 1:09 pm

Do I detect a whiff of GROUPBUY?! :lol:

TBH, if someone in the UK actually manages to make a SC kit with an easily obtainable SC like either of those two above, then sign me up. They'd make a tidy penny making adaptor kits etc. to make them as close to plug-n-play as they can be...
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Re: Small supercharger setup

Post by ChrisHolmes » Fri Jul 14, 2017 3:44 pm

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Re: Small supercharger setup

Post by ed80 » Fri Jul 14, 2017 5:25 pm

Rotrex superchargers have a great rep in BMWland. They have the benefits of a separate oil system, small size, plus rotrex sounds like rotary. They are harder to find second hand, but they come up from time to time for less than £1k. You can also use this as the starting point for a bracket.

No idea if there are any downsides to using a centrifugal supercharger with a rotary, perhaps it loses out a little on low end torque compared to a twin screw.
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Re: Small supercharger setup

Post by Phil Bate » Fri Jul 14, 2017 5:49 pm

After looking at all the different designs I settled on a centrifugal unit. The main reason being the whole point of a rotary is the way the output builds with the revs and being able to keeping it spinning high up the range all day long. The rotrex units would be perfect for this and are very efficient at high flow, and I got as far as sizing them and coming up with two possible setups. One mild one with no intercooler, utilising the stock upper intake manifold and running from the alternator belt thus keeping the install simple and cheap - and a stronger one where the UIM is replaced with a water/air charge cooler, and would require an extra pulley and belt to be added.

Both would utilise stock injectors and PCM, and would be a draw through setup utilising the current air cleaner and MAF (not requiring a blow off valve venting all the time you are not at WOT).

As always time and money are the restriction and I got as far as designing the bracket, with which you can only do so much using the technical drawings. At some point I will actually get hold of a couple of units and get a bracket fabricated, but it looks like it will be after I've finished and sold the house now :(
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Re: Small supercharger setup

Post by Ryan Rotary Performance » Fri Jul 14, 2017 6:02 pm

Guys....... anyone who thinks they can do a decent set up on the cheap is unfortunately mistaken.

So let's run through what you need.

Supercharger unit such as decent 2.1L screw type. That's £1225-£1500 to start.
Pulley configuration - would have to be custom (although the Ryan Rotary Performance ones are compatible with the kenne bell 2.1L) there is another £375.00 if you went for a one off it would surely be more.
Brackets - let's say £50-£100
Pre charger manifold - based on the Pettit design that would be £500 for a one off.
Charge cooler such as the Pettit design there's another £500.
Upper intake manifold another £500.
Then you have the charge cooler pre rad £200 for a cheap one!!!
Charge cooler pump £100
Charge cooler resevoir £50-£100
Hoses and connections belts etc £100
Bypass valve £100
ECU remapping £250-500

So I think at least £4K really to get something worthwhile.

For anyone who wants to see the 2.1L kenne bell next to the Pettit 1.7L blower.
20170325_170917.jpg

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Re: Small supercharger setup

Post by 350matt » Fri Jul 14, 2017 7:28 pm

Thats all for new parts though and I'd agree the prices are right for that, however I was considering something a bit more 'garage at home' level
so an 2nd hand eaton m112 seem to be about 300-500 quid and while water / air intercoolers are nice its again cheaper to do air / air as there's less parts

need to again find a donor for the air / air intercooler but how about this BMW 530 D item for £50

http://www.ebay.co.uk/itm/2004-54-04-06 ... Swq1JZHDQp

yes brackets to mount the charger etc will be needed and they need to be substantial as a M112 isn't a small thing so £200?

why do we need to remake the inlet manifold? are we concerned the standard plastic item will blow apart? as the Greddy turbo kit runs a bar of boost plus into the stock manifold

then of course we need pulleys. tensioner belt etc etc might need something custom turning up but again try and use donor parts for idlers and tensioners so allow £100 for this
then bits of pipe hose etc to make up the inlet path another £150
so this tots up to a bag of sand for hardware plus some lucky winners mapping time - allow another £500
so £1500?
say 2K all in

thoughts?

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Re: Small supercharger setup

Post by 350matt » Fri Jul 14, 2017 7:33 pm

Phil Bate wrote:After looking at all the different designs I settled on a centrifugal unit. The main reason being the whole point of a rotary is the way the output builds with the revs and being able to keeping it spinning high up the range all day long. The rotrex units would be perfect for this and are very efficient at high flow, and I got as far as sizing them and coming up with two possible setups. One mild one with no intercooler, utilising the stock upper intake manifold and running from the alternator belt thus keeping the install simple and cheap - and a stronger one where the UIM is replaced with a water/air charge cooler, and would require an extra pulley and belt to be added.

Both would utilise stock injectors and PCM, and would be a draw through setup utilising the current air cleaner and MAF (not requiring a blow off valve venting all the time you are not at WOT).

As always time and money are the restriction and I got as far as designing the bracket, with which you can only do so much using the technical drawings. At some point I will actually get hold of a couple of units and get a bracket fabricated, but it looks like it will be after I've finished and sold the house now :(
centrifugal units are pretty popular with the aftermarket for the reasons you say, and rotrex units seem to be generally Ok quality, however they don't do much for low end torque, my reason for doing an SC conversion would be to lift the bottom end up as well as the top and for this you need a PD blower.
Don't get me wrong I love the revs just don't see why you can't have both

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Re: Small supercharger setup

Post by tayfun » Sat Jul 15, 2017 10:14 am

350matt wrote:Thats all for new parts though and I'd agree the prices are right for that, however I was considering something a bit more 'garage at home' level
so an 2nd hand eaton m112 seem to be about 300-500 quid and while water / air intercoolers are nice its again cheaper to do air / air as there's less parts

need to again find a donor for the air / air intercooler but how about this BMW 530 D item for £50

http://www.ebay.co.uk/itm/2004-54-04-06 ... Swq1JZHDQp

yes brackets to mount the charger etc will be needed and they need to be substantial as a M112 isn't a small thing so £200?

why do we need to remake the inlet manifold? are we concerned the standard plastic item will blow apart? as the Greddy turbo kit runs a bar of boost plus into the stock manifold

then of course we need pulleys. tensioner belt etc etc might need something custom turning up but again try and use donor parts for idlers and tensioners so allow £100 for this
then bits of pipe hose etc to make up the inlet path another £150
so this tots up to a bag of sand for hardware plus some lucky winners mapping time - allow another £500
so £1500?
say 2K all in

thoughts?
In the link I sent before, where was used toyota's SC, the guy used intercooler from fiat croma, which fits great, for SC's inlet manifold he used the oem plastic one, and glued to it the gasket from toyota's SC, and he said that he tried to blow as much as he could air through that manifold and all been safe, so this part can be used as is. And overall the most expensive and time consuming should be mapping and hardware to fit SC in ours engine bay.

I don't think at the end we can get massive safe HP boost, but making the low rev torque higher will give our cars just what it lacks of + another nice sound from engine bay

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Re: Small supercharger setup

Post by ed80 » Sat Jul 15, 2017 11:21 pm

Speaking of Rotrex, I did find one company that offers a kit:
http://www.knightsports.co.jp/product/s ... r_booster/
Stupid price though :)
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Re: Small supercharger setup

Post by ChrisHolmes » Sat Jul 15, 2017 11:42 pm

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Re: Small supercharger setup

Post by Lemon » Sun Jul 16, 2017 12:51 am

on the subject of roots vs rotrex this might be of some use.

[youtube]https://www.youtube.com/watch?v=EHg2uqJvLOk[/youtube]
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Re: Small supercharger setup

Post by 350matt » Sun Jul 16, 2017 8:23 am

ed80 wrote:Speaking of Rotrex, I did find one company that offers a kit:
http://www.knightsports.co.jp/product/s ... r_booster/
Stupid price though :)
I'd agree with that kit the price is stupid
as rotrex units aren't that expensive to buy I'd say they're taking the mickey on that one

thing is there were over 1,000,000 RX'8s sold worldwide
the type of person that buys one of these buzz rockets is typically an enthusiast, whom should be a receptive customer for the aftermarket kits such as these
if you look on the GT86 platform , very similar price point , similar car but there's scads of FI kits for it, all complete with tunes and every last nut bolt and bracket required

for the Rex there's the greddy ( which apparently needs a lot of finishing off) and you have to tune it yourself , which is arguable the most important factor to finish it off and the Petit setup which doens't seem very popular

are we at the uncomfortable point where the cost of buying the car is now so low folks will never spend several thousand on a kit as the cost of the kit far outweighs the worth of the car?
a typical price point for an after kit is 17% of the purchase price of the car, so for a 100K car folks will spend on average 17K on modification

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Re: Small supercharger setup

Post by tayfun » Sun Jul 16, 2017 10:14 am

I think most of people who into buying boost performance hardware and sees high prices for it scared for the engine life, which in sum will cost just like buying something fast from the factory, so yeah, only enthusiasts going boost road

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Re: Small supercharger setup

Post by Rotary Potato » Sun Jul 16, 2017 10:41 am

I assume eveyone's read this thread?

http://www.rx8ownersclub.co.uk/forum/vi ... 05&t=73008
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Re: Small supercharger setup

Post by Lemon » Sun Jul 16, 2017 12:24 pm

yeah,

as a call back to my previous post i find it quite interesting that the rotrex gives more peak power whereas the roots type gives more low end power i guess it is down to the efficiency of the pump setup where the impellers on the rotrex are most effective at higher RPM's as opposed to the roots type where i would assume that above a certain RPM the rotors could be effectively be creating a barrier in front of it as it no longer is able to shift the required quantity of air.

i would also suppose that a rotrex (in our application) would fare better as there is, typically, no pipework in front of the blower setup to reduce and limit the available air to the system.

it is also worth noting that pumps always prefer to push rather than pull (as noted by the limitations on how far water can be drawn through a pipe system as opposed to being pushed, where there is no limit)

i apologies i'm drawing on my old hydraulic engineering stuff regarding pumping losses from uni there and whilst it was applied to water systems similar rules will still apply when shifting air as it will behave like a fluid in this sort of situation (as shown by the air straighteners required to ensure laminar flow for the MAF sensor)
Thanks, Stu

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Re: Small supercharger setup

Post by warpc0il » Sun Jul 16, 2017 4:14 pm

There seems to be some confusion regarding push and pull installions.

With carburettored engines "push" just means before the carb, while "pull" is after the carb. It makes virtually no difference to the pump.

However it does make a difference to the carb and the packaging.

With fuel injection the difference is really about packaging.

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Re: Small supercharger setup

Post by Lemon » Sun Jul 16, 2017 6:29 pm

sorry i should have specified, i wasn't actually referring to carb systems on that paragraph rather to the flow characteristics based on drawing compared to blowing.
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Re: Small supercharger setup

Post by warpc0il » Sun Jul 16, 2017 7:54 pm

Any compressor, super or turbo charger is always drawing from the outside and blowing into the engine.

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Re: Small supercharger setup

Post by Lemon » Sun Jul 16, 2017 8:36 pm

very much so, however pipework can be the limiting factor if it is before the charger a charger with no pipework before it wont have such limits.
Thanks, Stu

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Re: Small supercharger setup

Post by 350matt » Sun Jul 16, 2017 9:47 pm

Lemon wrote:yeah,

as a call back to my previous post i find it quite interesting that the rotrex gives more peak power whereas the roots type gives more low end power i guess it is down to the efficiency of the pump setup where the impellers on the rotrex are most effective at higher RPM's as opposed to the roots type where i would assume that above a certain RPM the rotors could be effectively be creating a barrier in front of it as it no longer is able to shift the required quantity of air.

i would also suppose that a rotrex (in our application) would fare better as there is, typically, no pipework in front of the blower setup to reduce and limit the available air to the system.

it is also worth noting that pumps always prefer to push rather than pull (as noted by the limitations on how far water can be drawn through a pipe system as opposed to being pushed, where there is no limit)

i apologies i'm drawing on my old hydraulic engineering stuff regarding pumping losses from uni there and whilst it was applied to water systems similar rules will still apply when shifting air as it will behave like a fluid in this sort of situation (as shown by the air straighteners required to ensure laminar flow for the MAF sensor)
the reason the centrifugal types produce more top-end that the PD type are largely down to drag, the power to drive a PD pump tends to reach an bit a 'knee point' and go exponential after a certain speed whereas the centrifugal type have a lot lower power requirement to begin with and the power requirement tends to increase at a linear rate
so by the time its making 1 bar of boost it needs less juice to do so compared to the PD making a bar of boost

however the centrifugal needs a lot of revs to get to the required boost level and typically with an engine running to 8000 rpm and you want a bar of boost then you have to get the gearing right to avoid overspeeding the blower, so this give a narrow power band where the charger is effective and the high engine speed of the renesis will compound this issue forcing the point of efficacy up the rev range .

there's a reason why the likes of mercedes, jaguar ford et al don't use centrifugals and stick to PD types like eaton as when sized correctly and geared correctly they work as you'd want ie a low down torque response that hammers against the red-line

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Re: Small supercharger setup

Post by warpc0il » Mon Jul 17, 2017 9:06 am

Our word of the day is " efficacy" ;)

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Re: Small supercharger setup

Post by warpc0il » Mon Jul 17, 2017 9:25 am

A few years ago Ford and Yamaha were working together on an engine with a centrifugal blower driven via planetary gearbox with a variable ratio. The output ratio being much higher at low revs then reducing as the revs increased.

This allowed the blower to perform well at low engine speeds while not over speeding at wot.

It also meant they could use a smaller blower which compensated for the drive losses and packaging issues of the gear drive.

The mule was a 3L V6 from the Jaguar X-Type though I'm not aware of it leaving the dyno bays and being fitted.

As with a large percentage of experimental configurations, it wasn't pursued any further, though I wasn't told of any fundamental issues.

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