The Mega Supercharger 4AGZE thread, using twinscrew charger

[jondee86]

And so the greater the tendancy for the nozzle to dribble (rather than atomize) at the begining and end of each pulse.

I would hope to be able to install the HSV within 500mm of the nozzle, and I like the idea of installing a spring-loaded check valve just before the nozzle. If this is set to open at (say) 10psi, it should pretty much eliminate dribbling.

The idea of injecting pre-charger is really to get the best possible vaporisation and mixing of the water and charge. Since this will be a custom install, I can locate the nozzle anywhere in the intake ducting. So I will come back to this a little further down the track when the intake side drawings are finalised.

Cheers... jondee86

[JustenGT8]

You guys are getting a bit too propellerhead about this The air velocity will take care of any drips as long as there's a valve of some sort to prevent siphoning while the engine is off. I just use a simple solenoid valve that closes once power is off.

Injecting pre charger is good as it improves abiatic efficiency, cools the charger and better seals the Chargers rotors so you actually get a small increase in boost.

Post charger is also good as the SC is a heat machine and cooling that boosted intake charge improves charge density into the cyls and a cooler intake charge is also less prone to det.

Do both if at all possible

[knightrous]

Check with Sprintex that the rotors will be fine with water injected into them and that it won't damage the supercharger. The internet might say it's 100% okay, because my cousin's, brother in law said so, but your $2500 supercharger is an expensive item to sacrifice if they are wrong .

[jondee86]

Yeah, I have asked Sprintex and they say no worries with injecting water-meth pre charger "if done correctly".

I will actually look at injecting pre and post charger, as I am not totally comfortable with putting all the water thru the charger. As I said before, I want to make sure that the air and water are fully mixed before reaching the manifold to avoid any distribution problems. Small nozzles should give a finer mist, and sound like the ideal solution

Cheers... jondee86

[jondee86]

One other thing that I was wondering about :-P My engine is currently on ITB's and redlined at 8200rpm. Seeing how with the supercharger it will have a nearly flat torque curve, I'm thinking that there will no longer be any need to rev to 8200 ?

Perhaps I should gear the charger to make a little more boost but redline the engine earlier at (say) 7800rpm. Theoretically it will still make the same peak power, but with a bit less stress on the engine. What's the prevailing wisdom ?

Cheers... jondee86

[trdee]

more boost less revs = yes.

also bear in mind the supercharger has a limited range. the harder you spin it to make boost, the less rpms you should be pushing up top, or you will overspin the charger, which will kill it quick. real quick

[knightrous]

The S5-210 has a RPM rating for 15000rpm continuous.
With a 7500rpm limit and 1:2 drive ratio, you'll only be hitting this rating, while according to the twinscrew calculator, you'll end up with around 22PSI*.



* - Theoretical

[jondee86]

The available Sprintex data is a little confused. The most recent brochure I have says max rpm 15,000, max airflow 210litres/sec and the charts max out at 120kPa of boost. The selection program says max rpm 13,500 for the S5-210 and to err on the side of reliability, I am going with the selection program limit.

At the moment I am looking at a 7800rpm redline and 120kPa boost. With a 130 to 75 ratio this maxes the charger at 213litres/sec. In reality I think 7800rpm is plenty, as unless you are street racing (bad... bad... BAD!!!) there shouldn't be any need to go past 5-6000rpm.

Just waiting to see what pulleys Sprintex have in stock

Cheers... jondee86

[trdee]

the confusion between the speeds might be because most compressors will have a continuous operating limit and then an overall limit.

IE its probably 13500 continuous, 15000 max

... or it could be the boost selection program is old and hasnt been updated to a newer revised supercharger which can now spin harder

[jondee86]

Bah... seems like some of the confusion is mine What I thought was the old brochure is actually the new one, and yes, the selection program is OLD !! The most recent brochure does say 15,000rpm max continuous and 22psi max boost. None the less, I think I will stay with the 13,500rpm recommendation for the initial installation. Looking at the performance data for twinscrew chargers in general, the Law of Diminishing Returns comes into play when you start pushing the envelope. And after all, should I ever want more, it's only a pulley change away

Cheers... jondee86

[jondee86]

Now that I have ordered the 120kPa pulley I have been pondering the matter of "Sustained Loss of Traction, your Honour" if I accidentally apply too much accelerator when merging on a wet road. Also, having an instant 18psi at 2000rpm may not be good for the engine ?

So I was looking at boost controllers for superchargers when I remembered about this curiosity... the Toyota TRC traction control



It incorporates a second ECU controlled butterfly in front of the throttle butterfly, and uses this to restrict the airflow to the engine to control wheelspin. It occurs to me that this kind of setup would make a nice boost controller. The TRC setup appears to have a DC motor that drives against a spring, so a single PWM channel should be all that is required for control. In its simplest form, the position of the butterfly could be set by a knob on the dash.

That would be helpful to me in due course, as I don't want to be trying to setup my system at 18psi. I would like to play with 6-10psi until I had the basics sorted, before running WOT. Short of having a larger pulley custom made, I think some kind of boost control is the answer

Anyone already been down this road ?

Cheers... jondee86

[Duk]

Me thinks you're making a complicated mountain out of a simple mole hill.

First of all, learn to control your right foot.
Secondly, you have an Adaptronic, so use its traction control capablities if need be.

And 18psi at 2000rpm is no different to 18psi anywhere else. It all comes down to tuning. Remember, you are working with a capable programmable computer, not living in the stone age.

[knightrous]

Can always dial back a bit of timing to torque limit the car down low if your that worried.

[jondee86]

Yeah... might have confused the issue by talking about traction control. That was just bringing up the fact that Toyota used a variable restriction in the intake as a form of boost control, not that I was looking for traction control. I already have my right foot under control

Cheers... jondee86

[trdee]

Your right foot will control boost also remember. Less throttle opening = less boost.

IMO try driving the car as it is first and see if you really need variable boost. I don't think you will. Also is this supercharger a clutched style? You can do things with the supercharger engagement to make it smoother at low revs/loads