Hey guys,

It's been a while since I came on here, but I've been busy! The kart that I've been building is very nearly done except for front brakes.

I've been tossing around the idea of turbocharging the CBR F2 engine that I have on there because I have an old set of headers, a pretty good break from school coming up, access to a CNC mill and lathe, and have read up on the turbocharging basics.

My plan is the following:

Garrett GT15 - good for 150 hp

Custom billet aluminum manifold, probably will make on the CNC mill

Turbo headers mated to the GT15

California cams due to lower valve overlap

Dual, smaller radiators to manage the heat more effectively

No intercooler because of packaging restrictions

Carb setup with pitiot tube

Remove ignition advancer

Possible E85?



Now for the questions:

1) I'm assuming I can safely throw 5psi at the stock cast pistons before they blow the ring grooves. Can anyone else provide an estimate of how much boost I can add before my pistons kiss their A** goodbye?

2) Does anyone know of a company that makes forged pistons for the stock bore? I can find forged pistons, but only in a 606 or a 636 kit.

3) If I can't find forged pistons, I'll make some. Can anyone provide me with a measurement of the diameter of the pistons so that I can order aluminum stock? I'll be making low comp pistons with around a 9:1 CR so that I could potentially run 10-15 psi.

At 5psi with a 100 hp engine, the Wallace Racing calculator said I could expect around 140 to the wheels, at 10 psi it said ~160 and at 15 it was 200. With this said, I'll be testing used eBay con rods with an arbor press or some other testing rig to make sure they can withstand the combustion pressures because, frankly, I don't want to dig chunks of con rod out of the scatter shield that will be on the back of the seat.

Here are some pics and a video of the current setup on the kart. In the video the button shifter blew a solenoid so I had to have someone put it in gear for me.

Thanks for the help,

Cal

 

Anybody have anything that might help me out?

 

Mate, you're going far into the unknown. You need to talk to a specialist engine builder for that kind of info.
I have to wish you luck though and please do keep this thread going with updates as you go. Modifications of this kind don't come around very often.
Sorry I am of no help whatsoever.

 

Yeah, you are not going to find any off-the-shelf bits for a f2. There is no market for a turbo'd 600. Gains vs. weight doesn't make sense. The logical thing to do it to save the money you can spend on upgrading that old f2 engine, and throw in a 1000cc or something. There are plenty of crashed examples that still have good mills. I know there is something to be said about being different, but I'd hate to see you get nearly there and find the gains aren't really worth it.

That's an awesome little piece of engineering you have there.

 

Thats just flat out remarkable buddy.

Perhaps you can find the diameter size on a set of new pistons? I know the 2 mill oversize makes a 67 mm?

 

Its actually kind of funny - I got my measurements from Wikipedia. They list the bore and stroke of each bike on their site, which I found to be 65mm for the F2. That's actually a good thing because 65mm is a good amount smaller than the 3 inch round 6061 that I have laying around, but I might invest in a chunk of 7075 or 2024 if the 6061 fails. I'm still reading up on piston design and the mechanical advantages of running different alloys of aluminum, but I'll post up a CAD model here when I get done.

 

Also a good story behind this one too - I actually had a 94 900rr stripped down to the engine that I was going to install because I read somewhere that it was a "drop in" fit. Unfortunately, it wasn't even close, and I would have had to change the engine mounts and move a bunch of other stuff around just to make it fit. Call me crazy, but I also had turbo plans for the 900 and had access to one of the old Mr. Turbo kits for the 900 and would have dropped it in there without a second thought had it not required a complete redesign. I did some more calculations and figured out that if I run a 12:1 afr, no intercooler, and 11 lbs boost, I would get to the 150 mark that I'm looking to hit. That would make it equal to the 900-919s, which would be hell of a lot of fun. Plus, I plan on keeping the weight to around 15-20 lbs, so there's really not that much weight added. With the new exhaust system, I bet I'll net about 10 lbs out of the total added weight.


Thanks for the feedback guys!

Cal

 

Update:

I've decided to stick with around 8-10 psi from the GT154, which is just an identical brother to the GT15. I'm going to see if I can find a junk yard with one of these cars (turbo-product) over winter break so that I can go and pull it for much cheaper than eBay prices. It looks like it's a pretty common turbo found in everything from Audi's to Fords, so I don't think I'll have too much of an issue finding it.

I ordered up a set of eBay pistons so that I could try machining down the dome to get a 10:1 ratio out of the stock pistons. I also have a foot long piece of 3 inch 6061 aluminum round for the initial pistons, but I'm looking into some 4032 (forged) alloy for the finals. Apparently silicon content in the aluminum takes an important role in the thermal expansion of the pistons, so the tolerance of the higher silicon 6061 vs the low silicon 4032 will be looser.

As far as the plenum goes, it'll actually be simpler than I initially thought. The design here: (https://www.google.com/search?q=turb...w=1600&bih=796) flows so that the inertia of the air isn't boosting one cylinder more than the other. I also like the fact that it looks like it'll be pretty easy to fab up and will fit right into where the airbox used to be - a good thing if I ever decide to start making kits for bikes. Also, the ideal volume is based on the volumetric efficiency of the bike times 1.57 times the capacity in liters.

If all goes well, I should be able to make this for around $150.

 

Dude, keep up the work and updates. And photos. Sounds like a fun build I look forward to fallowing it

 

I'll post whatever info I find that'll be useful on the turbo build.

Without EFI, I'll be stuck using the stock CV carbs - it's actually not that bad after looking at it some more. The stock carbs will handle 8 psi before the floats crush, so that'll be the limit of my boost. In order to make the carbs work with boost, the top and bottom of the carb needs to be pressurized otherwise the carb will whack wide open when you start to boost because of the CV running off of the vacuum of the carb.

Here are instructions on how to pressurize the carbs the right way. Turbo-bike.com