Just finished reading Maximum Boost by Corky Bell, here's a link to a PDF for anyone interested in reading. http://forums.acuralegend.org/corky-...t-t16899.html?

Things that I picked up from reading the book were:

1) Use separate tube style manifolds for better boost control, but use log style manifolds only where and when packaging constraints demand it.

2) Forged pistons are not the only go-to for pistons...high silicon aluminum alloys will do just fine if the design is right. Also, the ring land on turbo pistons should be double the thickness of their NA counterpart to handle the increased pressure.

3) If you want to extend the red line, the loads on the rotating assembly are multiplied by the square of how many more revs you want to go.

4) Draw through turbos are useless if operating below 80 degrees Fahrenheit because the fuel likes to puddle in the tubing as well as the tendency for the carb to ice over at full throttle. Not a good combo if you ask me.

5) Any stock engine should be able to handle 5psi easily so long as detonation is avoided.

6) Do not put the blow off valve at 90 degrees to the flow, air doesn't work that way because air itself has inertia and will not simply flow around a perpendicular bend. The ideal setup will be a symmetrical angle between the turbo, headers, and the BOV.

 

Well, I manned up yesterday and bought a turbo off of an old Ford Probe. The compressor map for the turbo matches perfectly to what I need it for and I think it should start making boost around 4-5000 RPM.

I would have stuck with the Garrett GT15, but there weren't any around that were even closer to my price range. So, the new model of the turbo is an IHI RHB5-VJ11. This turbo is water cooled as well as oil cooled, so I'll have to plumb a few extra lines to the turbo in order to make it work well. I got it with the manifold, the wastegate actuator (which I think is set at 7.3 lbs or .5 ATM stock), and all of the lines, so today I'm going out to buy a small side mount intercooler and BOV for somewhere around 30 bucks.

Small side note - If anyone has a set of California spec cams for the F2 or F3, let me know. The low lift and low duration are good for the turbo engines.

Another side note - If anyone wants to try this on their own, I actually bought an extra turbo from the guy that needs a rebuild. PM me for more info/pics.

 

Just got the eBay pistons in today and threw a CAD model together. These pistons actually look well built - the dome of the piston is right around 8mm thick when the dome of a turbo piston should be a minimum of 5mm thick.

Also did some compression ratio calcs as well. According to the equation provided by Corky Bell in his book, the trapped volume of the combustion chamber and cylinder is 14.27 ccs at a 10.5:1 compression ratio. I'm looking at using an 8.5 or 9:1 compression ratio for the final, so in order to make that happen with the stock pistons I need to make the volume of the compressed intake mix 19.86 ccs which I will do by putting it in the mill and shaving down the dome of the piston.

In order to determine how much metal I've already removed, I'll take the mass of the piston stock and then machine it down a little, weigh it again and determine how much was removed based on the weight of 1 cubic meter of 6061 aluminum. This should make it pretty easy to get the new compression volume just right.

The headers are nearing completion, but I need a MIG welder that's more adjustable than mine for the final welding so that I can keep from blowing through the thin walls of the exhaust tube. I'll post pics when I'm done.

Braaaaapppp

Cal

 

Joking aside. Looks good, I am eager to see how this works!

 

Feel free to ask me to clarify things, I tend to over explain stuff sometimes lol

 

I'm playing the fool a bit - I know a fair amount about this stuff. It's a real interest of mine, but I've never had the cojones to do this myself.

 

I'm in the same boat. I've wanted to do something like this for a while but haven't had the cash for it. Now, things are just falling into place and cheap parts are plentiful on Craigslist so I figured I'd do something cool that I might be able to use on a scholarship app or on the resume

 

that kart is badass, sorry I can't be of any help but I just wanted to say that. Can't wait to see it boosted!

 

After thinking about it more, instead of making a fully custom plenum I think what I'm going to do is reinforce the stock airbox with fiberglass. The stock box is built so that the airflow from the two inlets is evenly dispersed to the right two and left two carbs. Plus, the inlets are right at the front of the bike, so I'll be able to use the two holes as an inlet. It flows much better than anything I could make with this time constraint.

I'm not too concerned with an accidental backfire (which would blow the stock box to pieces) because I'm going to install a pop off valve that opens and vents to the atmosphere whenever the pressure inside the airbox goes above a threshold pressure. It'll kind of be like a blow off valve.

I plan on doing the airbox tonight, so I'll post up pictures later depending on how glued together my fingers are

 

Scratch that last post. Measured the airbox and the volume is WAAAAYYYYY too big. Just the bottom third is around 40 cubic inches, which is already bigger than the displacement of the engine. I think I'll make a slight dome to cover the bottom third and then call it a day.