Project Supracharger

[garethr]

:...This means that I will need a 4.5", 4.25" and 4" pulley making. I have access to a lathe, but have never used one before and not sure that I'm up to making a good enough job. Is there a club member who is dab-hand at this and could make them for me?

 

No personal experience, but I found this guy through a build diary on a bike forum. I think he's near Wisbech.

[David P]

Thank you for the link, if there is no-one up for/to it in the club, I will make contact, but may be simpler to just go to the local engineers.

 

Is there anyone with a single turbo that knows their boost pressure and cam timing?

 

Just boost pressure in psi or bar and spec/make of cam will do, I can find out the remainder.

Edited December 2, 2010 by David P (see edit history)

[chrispot]

good work!!, once up and running plumb in a vacuum guage between throttle and charger , if you have high vacuum at full chat ,then the throttle is not big enough or pipework or filter restrictive

In a perfect world you would get zero vacuum ,any vacuum present means the charger is out sucking the throttle/intake with the throttle full open , this vacuum uses power from the charger and ultimately crank to be created - less vacuum more power

running a tad of pcv oil thru the charger helps preserve the rotor tips too , but only a tad needed as a mist

The charge cooler remember is mostly for IAT control , you cannot create more oxygen after the charger - what goes in also comes out as its fixed displacement - pre charger is where the benefits of cooling are - more oxygen in ,more oxygen out

 

correct me if i have misunderstood what you have just said, is that the charger cooler is better before the supercharger?

[David P]

Hello Chris

 

In addition to your queery to Adam.

 

Does that imply that the water/meth injection would serve a better purpose if fed before the supercharger?

[jagman]

No , you cant charge cool before the charger as the air is not compressed, after the charger you can go overboard with coolers when all you need is to reduce IAT , you simply lose boost .

cooling is always better at the heat source in this case within the charger (in fact at the outlet side of the rotors) so water injection pre charger will reduce heat in a big way and reduce the need for the post charger cooling .

In fact fuel can be added as a cooling medium into the charger , this gives great fuel/air mixing and as you need more fuel anyway with more air being moved ,but not as effective as water /meth

These chargers dont like going much above 13 psi , they create heat and get back flows creating turbulence , they will however still work when pushed , boost will be fairly constant but rise at the high rpms as the exhaust starts to choke , this rise needs to checked when going for higher boost as much heat can be created .

This charger is a tad big for the engine but will flow plenty so good power to be made

[jagman]

It pays to remember the charger is a pump not a compressor , so within the charger there is no pressure , but think of the exit ,at the rotors one side is zero pressure and the other is say 13 psi ,so the pressure tries to go backwards between the rotor and case(the gap) against the flow , this causes heat and turbulence the higher the boost the greater the backflow (hence coated rotors and oil mist to reduce the gaps to minimum) -cooling the charger also helps minimise the gaps and pumping losses

[jagman]

All will become apparent when you dyno , you will get boost real low down and a torque curve much like a diagonal line , it builds very fast and follows the cam , once the cam is at it max operating point the torque will max and then stay there across the revs ( big smile ) until the engine gets inefficient and starts to choke , then the torque will drop off and the boost rise , this point will moved depending on pulley as will the whole torque curve ,hence the bonus of a quick change pulley , you can play around and get your "best curve" for the type of driving you do ... whatever its nice to ride a wave of torque from 1500 rpm in any gear and instantly !!

[David P]

Pre charger water/meth injection = greater cfm @ lower pressure.

 

With more O2 @ lower pressure, maybe the engine can achieve the trans max of 500ftlb with a 4.5" or 4.25" pulley.

This would reduce the possibility of belt slip, lessen the detonation issues and keep the s.c. within the parameters of it's peak efficiency.

Edited December 2, 2010 by David P (see edit history)

[jagman]

Pre charger water/meth injection = greater cfm @ lower pressure.

 

With more O2 @ lower pressure, maybe the engine can achieve the trans max of 500ftlb with a 4.5" or 4.25" pulley.

This would reduce the possibility of belt slip, lessen the detonation issues and keep the s.c. within the parameters of it's peak efficiency.

 

You have lost me there !, the charger is a fixed displacement, lets say 1 litre , so it can only ever move 1 litre volume of air per rotation, ie pump , the 1 litre contains 30% oxygen , it can only move this amount , the density of the air will determine the amount of o2 in the 1 litre , the density is down to the temperature and altitude ,

water meth into the intake cools the charger, it heats due the compression at the outlet and heats the whole charger ,and air within it , water/meth cools the charger and the the air passing through it making denser air , same 1 litre but denser = more o2 = more power - the CFM is the same as the same volume and same rpm

belt slip is due the torque on the pulley ,this increases with speed ,pumping losses increase with speed ,and efficiency decreases with speed

The water/meth will reduce detonation allowing greater boost ,and reduce heat losses,clean carbon from pistons,allow greater timing ,and leaner AFR,

The boost pressure is determined by the restriction to flow within the engine , ie put a bung in the exhaust , high restriction , so the boost rises , but flow reduces , porting the head flows more so the boost drops but more power is made for example .

The boost is also a function of the throttle opening , its all similar but different from turbos

[David P]

Adam,

 

I understand your input re. isothermal compression and O2 partial pressures, maybe this re-hash of my simplistic equasion will make more sense.

 

 

Pre charger water/meth injection = denser air = more O2 @ lower pressure = larger pulley = less work for belt.

 

More O2 @ lower pressure = less detonation and keeps the s.c. @ around 13psi (peak efficiency) to achieve 500ftlb (maybe).

Edited December 3, 2010 by David P (see edit history)

[jagman]

"Pre charger water/meth injection = denser air = more O2 @ lower pressure = larger pulley = less work for belt.

 

More O2 @ lower pressure = less detonation and keeps the s.c. @ around 13psi (peak efficiency) to achieve 500ftlb (maybe). "

 

not quite , its a fixed volume,but now denser, so pressure would not be lower , the load on the charger would be higher ,so more torque on the belt , any belt slip is more likely at the high rpms .

Detonation is more likely with higher C/R , due more heat generated, but the water /meth will work against det, larger pistons are more det prone ,but you cant do much about that, higher rpms are less det prone (bonus) but the charger pumping losses cause more heat , its all balancing .

Heat extraction from the head is a real problem , you cant rely solely on plugs ,you need enhanced heat extraction ie better water cooling ie more flow of water ,and you dont have oil squirters to cool the piston ,so much more heat is transfered via rings , you need much more water cooling than the TT and much more oil cooling for rings , However you have a charge cooler- so cool water is available for oil cooling as oppose to hot coolant

[David P]

Entiendo!

I think I will leave out the simplistic equasions, they are too complicated.

 

Re. cooling, I have a 13 row engine oil cooler plumbed after a Mocal thermostat behind the vent in the n/s wing and a gihugimous oil filter located in a cold draught, which combined also gives 2 litres capacity more than OE.

 

The water cooling has a double capacity rad, a TRD stat, an electric pump and twin electric fans, which I believe to be more efficient than OE, yet in a previous post you have intimated not.

 

However, the belt is to be reversed around the electric water pump idler pulley to give sufficient wrap for the s.c. pulley, so this is an integral and necessary part of the conversion.

 

The headers are multi wrapped reducing under bonnet temps, there will be cold air ducted to beneath the charger and a large vent in the bonnet ramming cold air onto the head.

 

The charger will be restrained to 11.9 or 13.5psi.

 

Will this be sufficient cooling, or should I be looking at further options?

Edited December 3, 2010 by David P
Adding detail (see edit history)

[jagman]

The first problem with aftermarket elect pumps is they are non specific , the original set up was designed and tested for the supra engine by Toyota .

First they designed the system to warm up quickly and in balance ,ie the block and head both kept at a rate of heat extraction relative to each other, this is then kept throughout the rev range . the waterways in the head were again sized and flowed to keep balance within the head, hot areas given more cooling ,and each waterway made with calculation and testing for back pressures and flows .

Then they thermally tested the bejesus out of it with the flow ranges of the mechanical pump , and probably upto around 500-600 bhp if the design limits were in fact this high .

The mechanical pump is self regulating , the higher the revs the higher the flow to cool /extract heat , its geared also to take in the non linear heat gains with rpms , and then flow controlled by the stat itself .

the bypass water was also tested and designed to suit the engine .

Some cars have specific elect water pumps , but these are usually ecu controlled and have heated thermostats ,all to gain close temp control , no overcooling and no overheaating no imbalance between head and block.

The bigger rads simply delay warmup ,but offer NO extra flow thru the engine or no extra cooling , colder stats simply open earlier ,but still restrict flow

How do you retain the heat balance with an elect pump with different flows than the stock system? how well do they keep the balance .what about warm up if no stat fitted? bypass water

Adequate cooling is a major thing for detonation and the whole engine life , pushing up power needs more heat extraction too much can fail without it , one reason I am doing a dual stat arrangement on my car - still thinking about your oil

[David P]

I have just read this thread, lots of info re. pre charger/post charge cooler water/meth injection. http://www.aquamist.co.uk/vbulletin/showthread.php?t=251

 

It appears that pre charger w/m injection can give a 10% denser charge, yet post charger injection is still required for det prevention.

 

As far as I can ascertain for this build, to inject a 50/50 mix pre charger when over 8psi through a 0.4mm nozzle, and also directly into the runners at over 1,500rpm using 3 x 0.4mm nozzles, would be a good starting point, I will contact Aquamist to confirm this.

Edited February 20, 2011 by David P (see edit history)

[jagman]

I have just read this thread, lots of info re. pre charger/post charge cooler water/meth injection. http://www.aquamist.co.uk/vbulletin/showthread.php?t=251

 

It appears that pre charger w/m injection can give a 10% denser charge, yet post charger injection is still required for det prevention.

 

As far as I can ascertain for this build, to inject a 50/50 mix pre charger when over 8psi through a 0.4mm nozzle, and also directly into the runners at over 1,500rpm using 6 x 0.2mm nozzles, would be a good starting point, I will contact Aquamist to confirm this.

 

the above does not apply in your case as they relate to centrifugal compressors,and have different conditions to satisfy -a good read , but they are using the wrong solutions for things like erosion ,and coalescence - there are greater gains to be had with pre and post compressor WI .

[David P]

The 'good read' convinced me there are gains to be had, what I need is a starting point for injector nozzle sizes.

 

Is my guesstimate anywhere near?

[jagman]

yes for sure good gains to be had ,but so little information and testing has been done especially with the roots charger , you are on your own here ,that comes with pioneering !! start small and work up , much dyno time will be needed , and unknown effect with droplets size,satutation point , AFR reduction, timing changes and in cylinder temps - due low speed of the charger erosion is not a problem ,or angle of incidence and the air wont go near mach 1 ,so much simpler in many ways than a turbo

I would use a small pre charger spray and larger post charger spray - you have linear boost so less complex , try it and see what works!!

[David P]

There was certainly plenty of hot air about cold air, and theoretical claims of up to 30%, yet I would be happy with the +10% air density @ 10oC below ambient that was actually achieved.

 

So to conclude:

Is my reckoning to begin with a pre charger 0.2mm nozzle activated at 8psi, and 3 x 0.2mm nozzles into the plenum operating when over 1,500rpm a feasable selection?

Edited December 6, 2010 by David P (see edit history)

[jagman]

Got to start somewhere ? so start from there , in the absence of lots of instrumentation , then run on a dyno on load at a fixed rpm , then use a laser spot temp gun and measure the temps ; intake,charger case , exhaust manifold runners ,cylinder head, -alter the WI and get new sets of temps and compare temps

[David P]

The engineer had a limp excuse for not planing the blowers bottom, the Main Dealers had forgotten to order the distributor cap and it is still too cold to be lying under the car making the pre rad brackets.

 

Dejavue.

 

I decided that the distribution knuckle can live without one of the support brackets, so have relocated a manifold pressure feed and have 'pruned' some more to give better lines for re-fab, this gives me access to make a better job inside and the finished item will look better too.

 

 

Edited December 6, 2010 by David P (see edit history)

[barneybrendan]

No , you cant charge cool before the charger as the air is not compressed, after the charger you can go overboard with coolers when all you need is to reduce IAT , you simply lose boost .

cooling is always better at the heat source in this case within the charger (in fact at the outlet side of the rotors) so water injection pre charger will reduce heat in a big way and reduce the need for the post charger cooling .

In fact fuel can be added as a cooling medium into the charger , this gives great fuel/air mixing and as you need more fuel anyway with more air being moved ,but not as effective as water /meth

These chargers dont like going much above 13 psi , they create heat and get back flows creating turbulence , they will however still work when pushed , boost will be fairly constant but rise at the high rpms as the exhaust starts to choke , this rise needs to checked when going for higher boost as much heat can be created .

This charger is a tad big for the engine but will flow plenty so good power to be made

 

so is it best to have water/ meth injected before the charger .would having it before and after the intercooler also help.At the moment i have mine plumbed in after the fmic,but thinking that getting it befor the charger sounds like a good idea.Can the water/meth run 2 nozzles or do you need 2 setups.

[David P]

Barney,

 

The link I posted to the Aquamist forum is very informative, inbetween the mind bending.

 

In a nutshell, it would appear that to have both is best, water/meth 50/50 @ 170ccpm is a baseline figure I found recommended for 300bhp, you can calc up and down as a percentage from this to find a starting point for your target output.

 

You will need to confirm that your w/m system is up to feeding 2 nozzles, and the 1/4 - 1/3 total delivery of pre charger feed will only be needed when on boost.

 

I have decided to begin at 1 x 0.2mm nozzle before the charger, activated by a pressure control switch @ 8psi, and 3 x 0.2 jets after the charge cooler activated at over 1,500rpm and delivered fuel parallel by interfacing the Aquamist 2C with the MAP sensor via the AEM ECU.

This will deliver up to 280ccpm whilst the engine is under max load and should be good for 500bhp.

The ERL pump I have is good for up to 300ccpm, and the 0.2mm nozzles deliver 70ccpm, you will need to check the spec of the pump and nozzles you are using.

Edited December 7, 2010 by David P (see edit history)

[jagman]

so is it best to have water/ meth injected before the charger .would having it before and after the intercooler also help.At the moment i have mine plumbed in after the fmic,but thinking that getting it befor the charger sounds like a good idea.Can the water/meth run 2 nozzles or do you need 2 setups.

 

you can run 2 nozzels but remember pre charger is a vacuum and post charger is under boost pressure , the most important thing is the size of the droplets , smaller the better .

post charger you need the finest possible spray and the water/meth must not be made to turn or change direction , slow in speed and touch the minimum surfaces , not easy !!!

smaller droplets of water have greater surface area versus larger droplets and they absorb the latent heat much faster - the time element in vapourisation is often missed .

How much better for vapourisation? ..... a smaller droplet say 10 microns versus a 50 micron droplet could have multiple times better effect in heat extraction within the time requirement - keeping droplets small is not easy as they easily get bigger and merge .

pre intercooler causes the droplets to become very turbulent and spin around ,slow down ,touch loads of surface area and get bigger the opposite of what you want .

Always try to kill heat at source or it becomes harder,

[Supra-Brett]

you can run 2 nozzels but remember pre charger is a vacuum and post charger is under boost pressure , the most important thing is the size of the droplets , smaller the better .

post charger you need the finest possible spray and the water/meth must not be made to turn or change direction , slow in speed and touch the minimum surfaces , not easy !!!

smaller droplets of water have greater surface area versus larger droplets and they absorb the latent heat much faster - the time element in vapourisation is often missed .

How much better for vapourisation? ..... a smaller droplet say 10 microns versus a 50 micron droplet could have multiple times better effect in heat extraction within the time requirement - keeping droplets small is not easy as they easily get bigger and merge .

pre intercooler causes the droplets to become very turbulent and spin around ,slow down ,touch loads of surface area and get bigger the opposite of what you want .

Always try to kill heat at source or it becomes harder,

 

Same sort of principle/theory as is used in the manufacture/design of firefighters hose branches (the bit where the water exits from). They are designed to produce a certain droplet size to maximise heat loss/absobtion via evaporation of water.

[David P]

It's too cold to go out and play, so I have found a bonnet with the bulge to model.

 

Edited December 8, 2010 by David P (see edit history)