Sterling

Yeah, that's right...It's me again.

A few of you may be familiar with my desire to get started on what was previously called my "Eaton M-90 12A Stockport" project; but which has been changed to the "Eaton M-62 12A Stockport" project.

So I've asked this before, but in the hopes that someone will come across it that knows of a calculation- just a simple formula...

The M-62 has a displacement of 1 liter per revolution, and a max RPM of 14,000.
Im looking for what psi I can expect from this thing.

Now...If you can relate to that, then perhaps you can explain simply to me the relationship of SC displacement, engine displacement, and boost.

My thinking, and I still have'nt got a firm handle on any of this (I've moved my project deadline to about 2004...that's when I expect I'll know what the hell I'm doing!)...

I figured that for a given size blower at a fixed rpm ratio; the smaller the engine displacement, the more boost from the blower.
Is that right?

The following is guesstimation on my part, as I really don't know too much about the Pontiac Bonneville that the M-62 came out of (and I've worn my fingertips down to knubs trying to search the web!).

The Bonneville has a 3.8 liter engine.
My guess is that it redlines at about 6,500 (my brothers Fierro I think redlines there)
My guess is that the M-62 top rpm was pulleyed to about 12000 rpms there because it was an OEM part for GM, and I don't think Eaton would be able to offer a 100,000 mile warrantee if their blowers were pulleyed to their 14,000 RPM redline...A total guess on my part about what I would think Eaton would do just as a "fail-safe" for themselves. But I'll use the max RPM from the Eaton site anyway.
And I'm guessing that the boost was probably about 5.5 psi...pretty good for a production car, I would think.

So, 3.8 liter engine @ 6.5K RPM
+ 1 liter blower @ 12K RPM
= 5.5 psi of boost.

Sound reasonable?

The Bonneville:
3.8 liter displacement x 6500 RPM = 24,700 liters per minute.
BUT!...let's not forget that since it only fires 1/2 of it's cylinders per revolution, we divide that number by half...
12,350 liters per minute.

The 12A:
1.146 liter displacement x 8000 RPM = 9168 liters per minute.
(Rotaries are so nice 'n simple!)

The Eaton M-62:
1 liter displacement x redline of 14,000 RPM = 14,000 liters per minute.

My logical comparison:

I'm simply going to compare the forced volume to the Pontiacs needed volume, and then do a comparison likewise to the 12A...Though I'm not so foolish to think it's all that simple (That's why I need your help!), and certainly not taking into account all of the other nasty little "monkey wrench into the clockworks" variables that would make a simple equasion into a three page long affair...(Expasion from heat, belt friction losses, blower efficiency, engine volumetric efficiencies at given RPMs...the list is freakin longggg!)

If
14,000/12,350 = 5.5 psi,
Then
14,000/9168 = X psi.

Bonneville...1.1336 extra liters stuffed into a 1.9 liter space yeilds 5.5 psi of boost.

12A...1.5271 extra liters liters stuffed into a 1.146 liter space yeilds X psi of boost.

1.1336/1.5271 = 5.5/X
...do a little cross multiplying, and I get 7.4 psi of boost for my 12A.
(Yechhh!...Was hoping for a bit more!)

Now I guessed alot of things about the Bonneville engine specs. But if I could get all the correct info, would this be the correct way of determining how much boost I would get?

The thing that just does'nt come across as 'right', is that if you stuffed 1 "extra", or additional liter into a 1 liter space, would'nt that make twice atmospheric pressure? So 14.7 psi x 2?

Just seems like I'm missing a HUGE piece of the puzzel here.

error402

ooohohohhohohoohohohohohohoh....i love logic problems :drools:

these might help out for more logical comparison

http://www.3si.org/member-home/jluci...-fuel-flow.htm
http://members.eaa.org/home/q&a/dec95.html
http://www.csgnetwork.com/csgpumppsi.html
http://www.plasma.kth.se/~olsson/units.html
http://www.motorsportsdigest.com/perform1.htm
http://www.acepumps.com/usefulinfo.htm
http://www.linkline.com/personal/dbarton/SpecSheet.html
http://www.outsidepride.com/infoformulas.asp
http://www.olemiss.edu/courses/che50..._Analysis.html

i know there is alot of info there and some that you might not think is useful. ~shrugs~ I found it useful in any case.

Sterling

"GROANNN...Sigh..."

The only one I found to be of the most value was the first link. I started looking at them from the bottom of the list, not finding much help. Then I got to the top one, and was completely overwhelmed!!!
Thanks for the help, but it actually jumps ahead (wayyy ahead!) to when I'll need to calculate air desity for fuel mixture, ect.

Right now, I'm really looking for the totally theoretical comprehension, and a thumbs-up, or thumbs down at my approach to how I arrived at my calculation.
Then of course, the answer to the inevitable follow-up question, "Why?"

Once I know the capability of the M-62 blower when combined with my 12A engine (As in..."What's the most boost I can expect with reasonably achievable cool temperaters?), I'll most certainly make use of that site.

error402

I'll talk to my next door neighbor. I think he has the formula that you need and if he doesn't know I think he does know some people that do.

A endless little loop I'll try to keep you posted. I wish I could have been more help.

Sterling

No, you were a great help. Please don't forget to talk to him, cause I'll be waitin' for the answer!!

REVHED

Hey Sterling, I think you're way off base on this one! All things being equal, the blower should make the same amount of boost on both engines. It has nothing to do with the size of the engine it's on. But I could be wrong. Where's RICERACING when you need him, eh?

Sterling

...So you're saying that if a tiny room with open windows that had a volume of 1000 cubic foot, and the windows were just big enough to let 1000 cubic feet of air out per minute;
And a much bigger room, with a volume of 10,000 cubic feet, and windows just big enough to let out 10,000 cubic feet of air per minute....

You put the same size blower, with the same rpm, and therefore the same CFM on each room, and the psi (boost) will be the same?

I don't buy it.
And I just don't get it!

faster7

What does psi matter?

I'd like to talk with you on this one, but basically one way I'd look at it is way different from how much boost will I get.

It should be easy to get a very close estimate of how many lbs/min of air you'll be taking in, at X rpm at the blower. That many lbs/min of AIR will support so many horsepower. The math I'd use would be real world BSFC numbers for rotary engines. Plug in an AFR of 11.5 or 11.9:1 or whatever you'll be running safely at max hp, and get fuel lbs/min appropriate for that AFR from your lbs/min of AIR calculation.

Viola, total horsepower potential that should be in the ballpark. GROSS hp. I'm afraid with the smaller m62 that these numbers may upset you. But if you fab everything up, it shouldn't be too hard to change it out to the m80 that's SO easy to come by now, or a m112.

What EXACTLY would it tell you at this point if you KNEW your setup would make 4psi or 6psi or 8psi? If you'd figure airflow though the motor at that point, etc, what would you find that you couldn't find just based on lbs/min of air?

I could be in left field on all of this, but I'm building my system in a similiar fashion, and betting my numbers for my setup are in line with the real world results. Then again, I don't care, I'm just going to gear it to not exceed supercharger's maximum rpm, plumb in a nice intercooler and water injection + programmable EFI and enjoy the results, whatever they may be.

Then we can all guess what happens to the amount of energy the supercharger takes from the crank when the inlet to the supercharger is no longer at atmospheric pressure. :-) If you thumb around some of the turbocharged airplane specs, some of them use the turbocharger's shaft through gear reduction to add torque to the output shaft. Follow me here?

R

peejay

Right-o! PSI is just a number... while power is made by moving air through an engine! More air moved through = more power.

What's really cool is if you take a theoretical engine at X amount of boost with no intercooler... then add an intercooler, it will probably make 80% of X boost now, but the engine makes MORE power, because the air charge is cooler and therefore denser... meaning more mass flow is getting forced into the engine, meaning the engine moves more air, meaning it makes MORE POWER! (grunt grunt grunt)

Sterling

Faster,
Read the other SC replies.

These last few replies here gave me exactly the perspective I should've come from in the first place.
Precisely where I was gonna go with my hopefully-newly-aquired data was temperature drop-volume drop-mass increase numbers crunching.
Ultimately, I wish to end up with "more than 6" psi, but as cool as I can get, and have the power of other set-ups with far more boost...all in a blow-thru Yaw Nikki set-up.
I wanna make this happen within a reasonable cost that is less than any other system of comparable results.

I tend to ask the foundation questions, or what I (in this case; mistakenly) think of as the starting point for my own calculations.
If I don't do it step by step here, somebody blows by throwing an answer at me, and I can't jam any variables into it because I don't know how they arrived at it. (I don't know if they just guessed, either!)

I had asked Paul Yaw about the Camden blower in conjunction with my modded carb. Among the things he mentioned was water injection.
Don't know anything about it. What will that do for me?

REVHED

Water injection is just another form of intake charge cooling. I've heard it also has the added benefit of cleaning carbon out of the combustion chambers. Probably be a pain in the *** to set up and then you have to make sure you never run out of water. I'd just go for a good intercooler.

Sterling

...was hoping to do both.

jr69187

This gonna be a runner and half when it is done. Sterling keep us posted. Soon i hope to have soemthing close to yuor setup jaunk yard has gave me some bery nice parts like 2 more 12a's plus the running 12 a i screwed hey if you any ideas let me know until i get it fixed i am wheeless and the more despirate i get the more likley i am to make a very bad move. Read the post that says bad thing

dan

faster7

Sterling, which other SC replies do you mean? I've read all of this thread and the other thread started by my buddy JR...

I like water injection. I wouldn't use it to replace an intercooler, only to augment it. The simpler/Low $ setups using an air compressor to pressurize the water tank are easy to throw together. Otherwise high pressure atomizer pumps aren't terribly cheap.

R

error402

Try going to the http://www.teamfc3s.org forum it's targeted to 2nd gens but I think i saw some posts about the mathematics about your question.

Sterling

Thanks, Error- I'll look into that.
Faster, I meant I had read the other posts from the other SC site we were all yackin on...sorry bout the confusion.

What about using old fuel injectors for high pressure water? Would that mist it well? (or is that just stupid? Don't know anything about injectors, or water injection.)

jr69187- Yeah, you'll be reading alot more about my progress, because I'm sure I'll have all kinds of questions in the future.

REVHED

Can't you use boost pressure to pressurize the tank?

mar3

iTrader: (8)

It's not water injection like fuel injection. Get a wiper fluid bottle and use the entire assembly to supply your water injection. Take some SS tubing and have your machinist buds drill two rows of tiny tiny holes into it on one side 30 to 40 degrees apart along its entire length. Run that pipe into a plate sandwiched between your turb..I mean blower and the intake manifold. It's spraying a LITTLE water to cool down the air coming from the blower to prevent detonation on the combustion side. It might help to pack more air since cool air=dense air=more O2 to burn, but I cant say for sure in a rotary application. Liquids don't compress so the wiper motor and its valving won't allow the compressed air at the manifold to shoot the liquid outta your washer bottle---I think! Use a relay that is on with "IGN". Wire a micro-switch to click "on" when the carb is at WOT and run the wire from the switch to the relay so it'll provide power for the wiper/washer motor. Voila! Water injection only when it's needed under load and WOT.

Sterling

I like REVHEDs idea a bit better because I think that the wiper pump would have fuel mix blowing back through it. I've taken one apart (I take everythinng apart!), and it's not likely to hold up to boost pressure.
Even if it did, it would be adding the same amount of water no matter what the engine RPM...I would think what's a good amount for high RPM would be not good for low RPM, and vice versa.

Anyway, what kind of temp drop are we talking on an ICed SCed 12A? (as a result of water injection, I mean...)

peejay

Water not only reduces intake temp (by flashing to sleam and absorbing heat - phase transition always results in greater heat absorption) but also the steam raises the "effective octane" of the fuel by buffering the combustion... in other words the flame travels slower becayse the water molecules get in the way. (simplified)

I was doing the math this morning, actually... of course I don't have the formulae OR my trusty napkin handy but as I remember, at 70% efficiency at 7psi boost, on an 80 degree day, air temps are 164deg exiting the compressor. That's not enough, obviously, to make water flash to steam, (especially considering the boiling point goes up with higher pressure) but you'll still have some cooling effect + the anti-detonant effect as well.

I was also actually going to ask a question in the Single Turbo section before reading this topic... I keep hearing that a water/methanol mix is best, 50/50... well washer fluid is 30/70 (?) methanol/water and is readily available at practically any gas station, so you don't have to worry about running out as long as the tank doesn't run out before the fuel tank does. But working on cars I see the washer bottles and the area around the nozzles eventually get stained from the dye they use to make it blue, I'm worried that it might have adverse effects on the engine if injected.

jr69187

I don't know i think having the inside of my 12a blue would be nice. Then i could get some thick plexiglass and build a completly see through motor. Now wouldn't that be special. j/k

dan

peejay

I suppose I could do trials where I burn samples of washer solvent in a controlled way (in a spoon?) and check for residue. or i could get a small engine... yeah! i could run an over rich mix of the stuff in my 80cc 2-cycle engine. That way I can see the effects of the dye in areas that don't see combustion yet get exposed to it... like the sides of the rotors between the side seals and oil control rings, which are exposed to the intake ports.

Must get to work.

Actually, that engine probably NEEDS water injection, 'cos I modified the engine a wee bit... shaved a ton of material off the top of the cylinder top, and then machined down the clyinder head where it spigots in to maintain .030" clearance from piston to head.. basically increased C/R a whole bunch! (I can't leave ANYTHING alone )

mar3

iTrader: (8)

Sterling,
You don't have water injection running as soon as you crank the key. It's only supposed to be injected under load like NOS unless you're at the Flats going for a top end run.

REVHED

Well, I just went through my 200 or so four and rotary magzines looking for a tech article on water injection I remembered reading and it just happened to be in the 2nd last one I looked at.

Anyway, the way they set it up is almost exactly like mar3 recommended except that instead of a WOT micro-switch they used an adjustable Hobbs pressure switch tapped into the inlet to drive the relay which in turn drives the wiper motor. IMO that's a better way of doing it because you can adjust the point at which the water injection starts to work. The nozzle was mounted before the turbo which solves the problem of blowing boost pressure through the system.

On this car which was detonating heavily without the water they were able to wind on another 8* of ignition timing and up the boost by a couple of psi as well with no detonation. They also saw a 50*C drop in inlet temps which worked out to about a 16% increase in turbo efficiency.

Sterling

Well THAT'S impressive! I kinda like that!
I will figure out a much less "cob-job" approach to the injection when the time comes.

Guys; if I'm running a 2:1 ration -supercharger to engine, and I make 8 psi @ 4K engine RPM, does that not mean I make 8 psi @ 8K engine RPM also (theoretically)?

In other words, won't I be trying to accomplish constant boost? Is'nt that what "pro-SC" people find desireable about them?
Reason I ask is because of mar3s responce about the water injection. Don't I want that all the time, just that the amount should increase with CFMs directly?