MEEN = Mechanical engineering.  It's the coding that the schools here in Utah use.  Actually,  I've taken calc a couple times now.  And the deeper I get into it the more I can see that it has real word apps... go figure.  

Thanks for the lesson in turbo charging physics.  If you have a picture of the plennum, that'd be nice too.

Later,

Dathan

bling,
 quick ? about intakes in general. would it be better to have a intake that is fed from the side(most cars) or straght through and branch out into individual runners. Kind of like a header(4-2-1) but in the opposite.

also, In your opinion should the Pent. be the same size all the way across. I've seen some that  tapper at the other side. I had two ideas on this last ccylinder will not get as much as the other/ it's smaller becuase it'll force the air into the cilinder because it has no where to go.

sorry if it's too off topic.
thanks in advance....
albert

Shapes of Plenums:

Generally the best plenums are those that allow the intake flow to maintain its momentum and flow directly into the cylinder.  While the "Best" shape is a subject of long debate, one fact is clear:  the intake should never blow across the inlet of the carbs or throttle body.  This would have a venturi effect and substantially reduce the pressure seen by that carb.  Much like the old laboratory vacuums that worked by flowing water by a small hole hooked to a hose.  The carbs would suffer the same effect to some extent.

I should say that I have seen plenums that taper and those that don't.  While a tapered plenum would stand a better chance of being correct, only flow testing can tell the truth.  Generally, even with flow prediction software, airflows are a little tricky and can be potentially unpredictable....Just ask the Aviation Industry..

Bling!

I've got a few questions now, after reading along for awhile!

How does the system keep at a certain pressure? Is there some sort of blow out valve that only works when a certain pressure is reached? Without this i would assume the turbo could just over pressureize and explode things   .

Another thing, while we're on the topic of air and whatnot. Would adding a ram air intake do anything at all? Probably does the same stuff as the turbo only just at high speeds. (I think I just awnsered my question)!

Oh well, I'll think of more!

The system maintains a certain pressure two ways: by using a waste gate and a blow off valve.  

The waste gate is a short cut for the exhaust to avoid going into the turbo.  The waste gate receives a pressure feedback from the plenum and a small pressure diaphragm opens the waste gate at a preset pressure (set by the amount of spring force upon the diaphragm).  The exhaust's heat and pressure energy is wasted...thus the name.

The blow off valve is a secondary protection.  It is simply a pressure valve like a radiator cap set to a couple of PSI over the desired boost pressure.  It normally does nothing.  However, when the engine is at high RPM and the throttle is shut, pressure builds up quicker than the waste gate can dispose of it.  When that happens the blowoff valve pops open and vents.  This normally happens when a highly tuned car or bike is at WOT and shifts gears....you hear the engine whine up and then a "pfooshhissstle".   Some of the more trendy tuners put a horn on the waste gate to make more noise.    

To compare Ram Air to Turbos, a turbo system typically adds 5 to 15 psi to the intake pressure.  At 150 MPH Ram Air effect is 0.5 psi.  The reason it has become so popular with bikes is that the new 600s and 1000s are so closely matched in engines and powermaking that the 0.5 psi can mean 1 or 2 more horsepower at high speed.  It also looks cool, and sounds good in the Ads, which sells more bikes.   "He's got it, So I gotta have it, too"

Bling!

this is a little off topic, but what do you know about pop-off valves?  i've got a blow off valve on my turbo supra, but am looking for something that will give me more protection from overboosting.  there's an adjustment spring on the blow-off valve, but no real way to set to a specific PSI.  know any good ones?

thought up another one!

What would happen if you had 2 turbos? (Or one for each cylinder) Would it not get enough exhaust pressure/speed to spin up enough to create pressure? Would it eliminate the little bit of pressure loss for the 2nd cylinder?

Do they just do twin turbos on cars because they have lots more cylinders and the pressure would drop too much? Sidenote on that: Do the turbos both feed all the cylinders or do they each feed half? ect.....

What else..... I guess thats all for now!  :mrgreen:

Im currently (well on winter break still) going to school to become either Mechanical Engineer or Aerospace Engineer (both are same till like 4th or 5th year). And yes, its a 5 year program here because we get co-op added into half the 4th and 5th years! I really like learning about anything mechanical, I've been itching at buying an old engine or something and tearing it down to see if i can get it back togeather and working!

most twin turbo setups, in fact, all the ones i know of, both turbos feed all the cylinders.  you see a lot of twin turbos on v-configuration engines because it's easier to route the piping.  the twin turbo setup on my supra is sequential, which means the one turbo comes on first for quick response, the other comes on at higher rpm for more top end power.  most twin turbo setups, the two turbos just run in parallel.

two turbos on a 500cc engine would probably be a bad idea.  more displacement spools the turbos quicker.  you would need two VERY small turbos to be worth while on a gs.  as far as i know, there isn't any real advantage to twin turbo setups over a comparable single turbo, unless it is a sequential setup, or you can't find a single turbo that is big enough for your needs.

Ok, still pinballing the Megasquirt FI bit around in the brainpan.   thinking of what to use for the Thottle bodies.  was thinking of some Guted stock carbs,  basicly pluging over all air/fuel porting save for air bleed for idle.  working a custom top cap to hold an injector and having it aim down where the neddle slide would be.   OR   make a manifold and bolt a 2bbl tbi from a small car engine engine.    Could use a single TBI and a custom plentum box. still, no coolent temp, unless one is rigged to run off oil temp.  O2 sens woudlnt be an issue. hmmm, Bling? any free radicals shorting amungst your nuerons?

I' try to respond to all the Q's today, from easiest to hardest.

For fuel injection, you could convert a carburetor.  Certainly, many people have.  However, if you look, there are a ton of throttle bodies available already.  What does the SV650 use?  Injector placement is easy, just drill a hole where you want it, and reinforce the mounting....The hardest part will be routing and mounting the pressurized fuel rail.  The easiest set up i could think of would be an injector after the throttle body, and use an electronic system to measure O2 and exhaust temp.  (that's what you really want to know, anyway.)

Twin turbos serve several purposes on a big engine.  The foremost is the reduction of turbo lag: it is faster to spin up to little turbos than one large one.  The cost is that the twins usually peter out at the higher engine RPMs where a large turbo would just be hitting it's efficiency zone.  Thus the preference in drag racing for super large turbos.  Problem is, it can take forever to spin them up; this is not good for street applications.  

Second, two smaller turbos working in tandem at, say, 65% efficiency, are better than a larger turbo handling the same volume at 55% efficiency.  

Optimum, for multiple setups, is the sequential system where one small turbo works for low RPM and a slightly larger one joins in for the High RPM.  You need more advanced controls for this, and special gates and valves for this setup.  Usually, only the pro builders can afford to spend this sort of money.  

Some engines separate the sides into mini turbo systems, with one turbo feeding each side.  This is really more of a packaging issue, and doesn't really add a whole lot to the system.  

There are some VERY small turbos out there, but since they are hard to find, and the graphs for them are even harder to find, most small engines use a larger, more common turbo - like the Garrett series I have.  

Now, Pop-off valves are typically, but not always, set by a spring on the inside to blow off at a certain pressure.  If your blow off (pop off) valve is set too high, you can either reset or cut the spring to adjust.  Some valves can be screwed in or out to set the pressure.  Turbonetics, Inc. makes a really nice one for about $100.  Also, not only must the valve open at the right pressure, it must vent enough air to decompress the system.  If the valve is not big enough, then some big turbos can open the valve and STILL pressurize the system.  Dangerous.  Make sure that your blow off valve is big enough.  There usually is some flow rating for them.  They should at least match the flow of the turbo at highest efficiency.  

WheW!    I'll check back later.  

Bling!.  

PS.  Lots more can be said about EFI and Blow off.  This is just a light touch.

gonna have to disagree with you about the twin vs. single turbo setups.  it is true that you *could* have  a twin turbo set that spools faster than a single turbo setup.  it's also true that you could have a single turbo setup that spools faster than a twin setup.

i think we can agree that two small turbos, that are less than half the size of one larger turbo has less inertia, and therefore quicker spool.  let's say they have half the inertia (which we can agree is NOT true, they would have less, but it makes my math easier).  now you are splitting the exhaust gas in half to spool two turbos, you would get identical spool.  if you made those turbos any bigger, they would spool slower than a "double" sized single.

anyway, this argument could go on and on, but i don't feel it's accurate to say that a twin setup will outspool a single setup.  that's too broad a statement.

on sequential systems... optimal would be truly sequential unequal sized turbos but that is extremely complicated (one turbo comes on first, and as the second comes on, the first shuts off).  the stock turbo setup on the supra has two equal sized turbos in a quasi-sequential arrangement.  (one turbo comes on first, then both) it's not as good for high end power or low end spool as an unequal sized setup, but the tradeoff is, it only requires one (maybe two) valve(s) to operate.  for anyone that interested in a true sequential, unequal sized turbo setup, there's a good thread somewhere over at supraforums.  if i can find it i'll post a link.

next... the pop-off valve.  maybe i've got my terminology wrong, but you seem to be using the term blow off valve and pop off valve interchangeably.  the blow off valve i have is not actuated by boost pressure.  it's either vaccuum actuated or actuated by the change in pressure, and so adjusting the spring doesn't <edit>change</edit> at what pressure it blows off.  (hks super sequential BOV)   i'm looking for something more like a wastegate, only for the compressor side, not the exhaust side.

Jiggersplat,

The rotating inertia of an object increases with the square of its radius. This is the reason two smaller turbos spin up faster than a larger single one blowing the same volume and pressure .  For a quick example, the moment of inertia of a sphere is I=2/5 x Mass x Radius squared.  Thus, in the two turbos, the moment if intertia is double, in the second larger turbo, it is squared.  I realize we agree, but I wanted to support my statement.

"Pressure is pressure" whether positive or negative.  the blow off valve is simply a pressure differential system.  Vacuum operated blow off valves have a lead to the intake after the throttle and before the valves, to draw off the vaccum there.  the differential pressure in the valve works against a spring inside to open the valve.  Trust me, there is a spring in there, whether it is metal or just a stiff rubber diaphram, there must be a force to return the valve to close. (no use having a valve that opens at just 1 psi differential, either)   Another type of blow off is simply a static pressure valve as part of the plenum, and uses outside air.  This is an absolute pressure blow off.  This is what i was talking about.  They are both the same thing, just receive pressure (or lack of it) from different sources.  

Corky Bell, a renowned Turbo Engineer, has written a book called "Maximun Boost".  Corky has laid out the basics very well, based on true science.  He also has a website where you can glean more info.  For a pictoral explanation of what I'm talking about, I suggest that everyone go pick it up.  It's about $22 at barnes & Noble.  I don't mean to Hawk the book, but it really is the best source of general information in one place.

Bling!

i think the SV 650 uses a larger diameter TB. main reason i was thinking Moded carbs, they are perfect fit, airflow is designed for that engine, plumbing shouldnt take up any more space then standardlines already do.

i think i have a trashed set that i can play with, wouldnt need a hardline for fuel rail. perhaps (depending on pump) 2 threaded injectors with braided lines.

ok yea but i thought you were goin to post up some vids of your bike.

on the twin turbo versus single turbo issue.

In the case of a two cylinder motor.  Two turbochargers in parallel would not be a good idea.  Exhaust timing is a big factor in getting turbochargers to spin up and stay that way.

In the case of a harley davidson. With it's odd (from an exhaust builders standpoitn) exhaust timing.  It's possiable to actually have air in the plenum stall and even reverse the spin on the turbocharger.  The more even the exhaust pulses, the less time the turbo has to coast on it's own.  And the faster it will spin up, and stay up.

If you had two turbos on a gs500.  You'd have ages between exhaust pulses.  At that point I might even considder using a flapper valve to prevent backflow from the pleanum into the turbo.  

Sequential turbos "might" have a place.  But unless you need instant boost responce I can't see it being a real issue on a gs500.  I mean, look at our example.  45psi, single turbo.   How's the lag?  I have this funny feeling out engineer friend matched his turbo right so there's almost no lag whatsoever.  Between that and a properly sized pleanum you're sitting pretty.

Staged turbos....  Well if you want 150psi manifold pressure, that's the only way to get it  

Course, if your biggest concern is boost responce, your best bet is to run a small pelanum.  And run multiple throttle bodies.  One on each side of the turbocharger.  This stalls the compressor when you shift.  Stalled compressors use less energy than one actively compressing so the turbo doesn't spool down as much in the meantime.  Blow off valves are often rigged to simmilar effect.  By dumping pleanum air between shifts you can  reduce energy lost as well.  (turbo isn't trying to pump against 15-45 psi...)

Isn't the rate of spooling effected by the angle of the vanes, and to prevent overspooling at low rpm's you increase the angle so the turbine is essentially less effecient at lower rpm's and only reach their maximun effeciency at the desired rpm?

Quote from: BlueknytOk, still pinballing the Megasquirt FI bit around in the brainpan.   thinking of what to use for the Thottle bodies.  was thinking of some Guted stock carbs,  , Bling? any free radicals shorting amungst your nuerons?

I believe Dana used throttle bodies from a 550cc (or thereabouts) snowmobile.

FWIW Dana doesn't park here anymore...

Quote from: DomIsn't the rate of spooling effected by the angle of the vanes, and to prevent overspooling at low rpm's you increase the angle so the turbine is essentially less effecient at lower rpm's and only reach their maximun effeciency at the desired rpm?

Yes, no, no.     Yes, the "vane angle"  Actually A/R ratio of the turbine housing changes the efficancy and gas flow required to spin the compressor up.

No, the turbine housing isn't changed to alter compressor speed.  Though it can be used to rig a turbo setup that won't overspeed.  But usually the wastegate is used to to prevent compressor overspeed.  And more importantly to control boost pressure.  

Overall system efficancy is affected in part by the A/R ratio.  By incresing backpresure on the engine or reducing backpressure.  But that's a byproduct, not a primary function.

a lot of the new turbodiesel cars here use turbo's with variable vanes. It's used to let the turbo spin up at lower speeds. Maybe they're even usable on GS500's. The turbodiesel engines for cars here are mostly 1900 cc, but they operate at much lower rpm. The turbo works really well at 2000 rpm, so it will probably work also on the GS when it's at a higher rpm.

Quote from: Blueknyti think the SV 650 uses a larger diameter TB. main reason i was thinking Moded carbs, they are perfect fit, airflow is designed for that engine, plumbing shouldnt take up any more space then standardlines already do.

i think i have a trashed set that i can play with, wouldnt need a hardline for fuel rail. perhaps (depending on pump) 2 threaded injectors with braided lines.

You're right, SV650 has 39mm throttle bodies... If you figure out how to convert the carbs, please let us know!

I think I'll be looking out for soma carbs on E-Bay!


D.