Stroking an inline 4 Turbo

[nhgunnut]

A question for the engineer types here.
I am Running a Hahn Turbo Kit and Port Fueler (Secondary Fuel Rail) On an Otherwise Stock 05 Busa. (Last Dyno Run showed 257 RWHP and 139 Ft pounds of Torque Peak torque at 6k. ) I have been counseled by people a trust against punching out a Street turbo as the tend to blow out head gaskets regularly. Up until recently a custom stroker crank at about $2700 was out side of my budget. But I have found out I can use a Gen 2 crank and pick up an extra 10mm of travel for a bump to 1340. (My cost on a new gen 2 crank is just shy of $750 the build gets completed at a local shop for just under 2500. Now on a normally aspirated Gen 1 with a stock fuel system and PC3 this has proven to produce an extra 8 to 10 horse the big gains have been with a slight degree of the cams and extra 12 to16 foot pound of torque. Logic seems to indicate that between the turbo and the fuel rail increases to be as much as 30% higher with the added side effect of the extra volume of exhaust gases causing the turbo to reach boost levels sooner.
IThe more I explore this the better I like it. But if we have folks here who can see a problem with this I would like to know. I appreciate your time. Rick

[derf]

Not an expert, take my thoughts with a grain of salt, but.

You would be better off lowering compression and upping boost than increasing compression and maintaining the same boost. Bikes in general already have pretty high compression ratios, I wanna say 12.5:1 is just about standard, my last turbo car had 8:1 compression, allowing me to up the boost and adding more power than just adding compression.

I would also question your fuel situation, I'm guessing that buy a 2nd fuel rail you mean the injectors are squirting into the head like the stock ones. instead they squirt into air hose from the airbox. The fuel doesnt vaporize as well the further up the air stream you go, instead it clumps into larger droplets and burns slower in the cylinder, causing preignition, upgrading the compression you will need a much better fuel system, possibly a larger dual stage injector in the stock location.

Anyway, to sum it up, leave it alone, upping compression on a blown bike will do nothing except cause detonation and broken engines. Save your money and buy a chrome spike kit or something instead

[nhgunnut]

Not a big fan of chrome. Or other "Aesthetic" changes (frankly i find that and stretched arms on bikes that don't drag goofy and not my style of goofy) This is my primary commuter not a bike night queen.
Using stock pistons and a standard 1mm base plate spacer and stock length rods actually drop the compression (If I were going normal aspiration I would use the gen 2 length rods) You are right about the the port fueler
www.turbosystem.com/cycle/suzuki/Busa Portfueler.htm it would not be ideal for a drag bike. It has been a great rig for me . Tied to a MAP sensor it eliminates that goofy falling off a ledge feeling you get using just the S2000 injectors or the Just splashing in extra fuel with and FMJ. But as you point out it can "puddle" under heavy load.
I have begun talking with drag guys that Build the 600 hp bikes using the Larger Garret turbos. They oddly enough are liking the Math Seems like with the right degreeing on the cams I should be able to see 150 foot pounds or torque in the 4800 to 5400 rpm range. with corrected RWHP in the 270 range. My goal is more usable torque both at normal pressure and under boost. I am leaning heavily in this direction. Now I just have to identify the FELONY FUNDING plan I am going to use

[Dave]

Originally Posted by nhgunnut

Not a big fan of chrome. Or other "Aesthetic" changes (frankly i find that and stretched arms on bikes that don't drag goofy and not my style of goofy) This is my primary commuter not a bike night queen.
Using stock pistons and a standard 1mm base plate spacer and stock length rods actually drop the compression (If I were going normal aspiration I would use the gen 2 length rods) You are right about the the port fueler
www.turbosystem.com/cycle/suzuki/Busa Portfueler.htm it would not be ideal for a drag bike. It has been a great rig for me . Tied to a MAP sensor it eliminates that goofy falling off a ledge feeling you get using just the S2000 injectors or the Just splashing in extra fuel with and FMJ. But as you point out it can "puddle" under heavy load.
I have begun talking with drag guys that Build the 600 hp bikes using the Larger Garret turbos. They oddly enough are liking the Math Seems like with the right degreeing on the cams I should be able to see 150 foot pounds or torque in the 4800 to 5400 rpm range. with corrected RWHP in the 270 range. My goal is more usable torque both at normal pressure and under boost. I am leaning heavily in this direction. Now I just have to identify the FELONY FUNDING plan I am going to use

just make sure that the piston speed isint through the roof. Too much stroke can do that. Especially with high reving motors like ours

[derf]

Originally Posted by nhgunnut

Not a big fan of chrome. Or other "Aesthetic" changes (frankly i find that and stretched arms on bikes that don't drag goofy and not my style of goofy) This is my primary commuter not a bike night queen.
Using stock pistons and a standard 1mm base plate spacer and stock length rods actually drop the compression (If I were going normal aspiration I would use the gen 2 length rods) You are right about the the port fueler
www.turbosystem.com/cycle/suzuki/Busa Portfueler.htm it would not be ideal for a drag bike. It has been a great rig for me . Tied to a MAP sensor it eliminates that goofy falling off a ledge feeling you get using just the S2000 injectors or the Just splashing in extra fuel with and FMJ. But as you point out it can "puddle" under heavy load.
I have begun talking with drag guys that Build the 600 hp bikes using the Larger Garret turbos. They oddly enough are liking the Math Seems like with the right degreeing on the cams I should be able to see 150 foot pounds or torque in the 4800 to 5400 rpm range. with corrected RWHP in the 270 range. My goal is more usable torque both at normal pressure and under boost. I am leaning heavily in this direction. Now I just have to identify the FELONY FUNDING plan I am going to use

Also, what is your intended use? Drag racing? Remember, drag racers might only ever see a few hundred miles of hard use before they replace an angine, if you are looking for any typer of life expectancy then what you are thinking about is a bad idea

[nhgunnut]

Originally Posted by derf

Also, what is your intended use? Drag racing? Remember, drag racers might only ever see a few hundred miles of hard use before they replace an angine, if you are looking for any typer of life expectancy then what you are thinking about is a bad idea

I am not a racer nor do I intend to be .. The Busa in my opinion is a GT bike but the Gen 1s had to weakeness IMO Brakes were 90s I have upgraded so that is resolved... cammed and geared for top speed low end is lackluster. To some degree the gen 2 bikes address this. (My B King comes off the line almost as hard as the Ducati it replaced. with Brakes that are every bit as good) My goal is increased torque acrossd the curve but especially at the low end. that combined wth an earlier spool up for the extra volume. Life expectancy on low compression turbos are not significantly different that stock bikes. Data indicates the weakest point in this kind of conversion is of all places valve guides. I will be doing the Oil Galley conversion at the same time (assuming I go this route.)

[No Worries]

This book on turbocharging is supposed to be good: http://www.amazon.com/Motorcycle-Tur.../dp/1884313078