well, of sorts...
this is VERY basic, and theres ALOT to actually boosting you beloved bike, but heres an appetizer to the 9 course meal that is forced induction.

ok. since many ppl have an infatuation with boost and such, there's alot to consider when applying a turbo to a n.a. motor when doing a custom build.

here's some info that will lead you in the right direction if you want to really build your own custom, hand selected turbo setup.

-Motor size
-turbo size
-RPM range
-Type of use for machine (drag, salt flats, ect)
thers some more, but those are the Mr. Obvious ones

ok. your example!i'm going to use a 1000CC motor or this, cuz thats the example i have in my engineering literature. i can cheat like that.

the main thing is to size the correct turbo. you must find the specific amount of air flow needed.
for this we're gonna use
-1000CC motor
-4 stroke
-max RPM
-max boost

formulas you'll need:
---------------------------------------------------------------------------
Pressure Ratio
basically the difference between your target boost level and atmosphereic pressure.


Pressure ratio=Pb+Pa/Pa

where....

Pa: atmospheric pressure
Pb: boost pressure

ex...10psi+14.7psi/14.7= 1.68

thats our ratio....1.68

---------------------------------------------------------------------------
(a rough constant figured mathmatecally..)

VE, or volumetric efficiency, which is basicaly how efficient the engine is. these are typical values

VE of a stock motor in good condition= 75%
VE of a high perf. tuned motor= 80%
VE of a full built race motor= 94%

we're gonna use 80% here... pretty common
--------------------------------------------------------------------------
displacement

Cubic inches=Cubic Centimeters/16.387

ex. 1000cc/16.387=61.02

so, 61.02 Cu.In. is our displacement
--------------------------------------------------------------------------

Density ratio

thats a fuction of a chart that is usually available from the turbo manufacturer and involves its effeciency, and cross referencing our previously found pressure ratio of 1.68 for this example.
this chart in front of me has the Density Ratio at 1.4 with a turbo efficiency of 70%

so, our DR is 1.4
--------------------------------------------------------------------------
ok!! lastly we have the big one. CFM


the Cubic Feet per minute your engine requires is a function of the aforementioned values

so..
CFM= [(DxCIDxMAX RPM)/1728]xVExDR

WHERE.......
D-displacement factor per revolution. .5 is for 4 stroke motors and 1.0 is for 2 stroke
CID-cubic inch displacement
VE-volumetric eficiency
DR-density ratio
1728-number of cubic inches per cubic foot

ok now.

[(.5x61x10,000)/1728]x.80x1.40=197cfm

so there you have if. your literbike will need a turbo capable of delivering roughly 200CFM

you don't need a T88 for all that power!!

spooling up a big turbo is a waste. the A/R is the key to tuning the turbo to your specific application

the bigger the A/R the slower the wheel will spin.(on the exhaust, or "hot" side)the A/R is basically the cross sectional area of the exhaust inlet port.
it equals the incoming gas opening in the scroll, divided by the radius from the impeller shaft to the center of the opening. if you were to unwind the turbo's snail shape, you'd have an ice cream cone shape where the top of the cone would be the outlet (on the compressor side) and the tip of the cone would be where the inner passage of the turbo tapers to a point, and where boost actaully starts to form.

bigger motors typically can use a bigger A/R and get away with it.

a larger A/R wll gain top end and the expense of bottom end grunt. so a salt flat racer would love a larger A/R.

the smaller the A/R, (on the hot side) the faster the turbo will spool up, but it will work a little harder as well because the rotational speed is increased with a smaller A/R

remember... turbos typically see 150,000RPM!!!! sometimes more. theres turbos that spool to 230,000rpm at full boost.
the reason for the faster spinning is cuz the exhaust gas is forced closer to the center of the impeller (exhaust or "hot side") and forces the wheel to spin quicker. the tip speed of the fins is usually supersonic, which is where the whistle comes from. ya figure you got something spinning 150,000rpm, can you imagine the surface speed of that at the edge of the wheel?

the A/Ris one ofthe most important parts of a well sized turbo system.

just remember..
Big A/R= top end madness and crappy response (like a .80 hotside A/R)
Little A/R= snappy response, great low and mid range... dies out on top end. (like a .25 hotside A/R)
My TDO4-L has a hot sideA/R of .60 and should be a well rounded turbo for a 750. it flows more than enough -at 360CFM@15psi..if anything, it may be too big... my motor only requires 149.07CFM@10,000RPM... but oh well. it was free, so i'll try it anyway.


there bibles of turbo variables out there. wheel trim, bearing types, oiling issues, varible vane setups, intercooling, water cooled cartridges (turbo bearing housing), pressure drops in your piping, carb jetting/fuel injector sizes, ignition timing, and cams are just a few things that can make aperfectly sizedturbo system suck, make it badass,or make a bad sizing job actually work for your bike.

well, i'm tired and am wrapping it up now. my info's sourced from a boost and spray application and engineering book, and ihave alot more data if you desire such crap.

i hope you either had a great nap with the induced boredom, or actually learned something. good luck and have fun!

and thank you, as always, for your time! its appreciated.

 

^^^^^^^^^i knew that!

 

i was expecting a picture of a turbo on a bike...

but numbers are good too...

 

I cant answer your prayer fahim but here I am!

Anyway how do I tell what size turbo I need? all those numbers made my head hurt. And Im great at math? huh go figure. So I already have a turbo and extra header, but the turbo is pretty small. How do I figure out if it will work?
Thanks in advance.

 

So i looked everything over and figured about 176.1 for my 636 but that still doesnt tell me what turbo to use. I would guess that the small one I have would work fine. And what about an intercooler. Does it need to match the cfm capababilities of my bike? Thanks

 

I'm assuming you're only going to run around 6 lbs of boost or so. An intercooler will make it so you can run more boost safely, but then I think much beyond 6 lbs you're getting into the red zone of the capabilities of the motor.

 

ya, is that yor calcuated flow requirements? hell, my 750 is around the 150CFM mark... i dunno.

if you have any info on the turbo, like a tag, a spot where the model or anythings engraved on it, or whatever else you can find, then you may have to contact the creator of the turbo and see about acquiring a flow (or "compressor") map. its basicall a graph plotted out with the turbos efficiency and flow rate at a given boost amount.

i may be able to tell what it is if i saw a pic of it... something thats the equivalent of a T2 or T3 (garrett) ot a TDO-3 or TDO-4 (mitsubishi) will be perfect for a 636. that A/R thing is the biggy tho when tryin to size a snail properly. i always use the hot side numbers, since that'll ultimately dictate how the turbo reacts. a .25 A/R is a common small engine number. i wouldn't go any higher than maybe a .60...
my turbo has a 2" inlet for the compressor. though thats not a very reliable way to judge flow, you still know that you're not going to get mad flow out of a TDO-2, which has an inlet the size of a quarter.

i'm more than happy to try and help in whatever way i can.

oh, and just like compstall said, i wouldn't go too crazy with the boost on a stock motor. the compression is too high for anything over probably 8psi, and the ignition won't retard to stave off detonation. anything over 7-8 pounds tho, and you'll probably lift the head off the block! that would be poop. the intercooler, however won't necessarily let you run more boost into a motor not built for it..

i'll try to dig up some intercooler pressure drop info. if its not a big i.c., then you shouldn't worry about problems...but it does need to be sized large enough to flow i'd say 100-120% of your turbos highest CFM. it doesn't have to be big physically, but as long as it flows well.....

you dont have to really even run an i.c. with low boost stuff. plus, its a b*tch to try and incorporate all that stuff in an already cramped system. its a plumbing nightmare.. theres some craft ways to run a decent size i.c., but if you're not gonna run at least 12psi, i wouldn't worry about intercooling too much, bro.

god luck with it, and like i said, i'm more than happy to help.

 

Since this is not a how to: lets try general tech.

 

[sm=imsorry.gif]

 

hey so i found out that the turbo is a lombardini, off a small turbo diesel. Its inlet is only about 1in so am i ok to use it or will it be too restrictive? I havent got any word back on the flow charts from the man. but I am wondering if a head spacer will do the job for keeping the engine more flexible with boost. I am only planning on 6-8lbs but I just need some guidance. If yours is at 150 then mine cant be more than 130 I would imagine. but does that mean that the intercooler has to flow 130cfm or just that it has to flow the max of the turbo? thats what is confusing me i guess.