Well I've played the N/A game long enough. It's time for Blown Alcohol. I have a Precision Turbo 4831B, its about the smallest turbo Precision makes and is supposed to be good to 400hp. I'm thinking I'll shoot for 250hp max. But who knows I'll probably get greedy...lol

Here is a pic of the bike Naturally asperated. We run 300 ft. dirt and sand drags. Its a factory Bombardier DS650 bored and stroked to 963cc so just short of 1 Litre. It makes around 125hp at 9500rpm on oxygenated race gas. More to come.
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What does this thing weigh? That ought to be quite the ride.

 

That is very cool. I never would have thought you could get that much cc out of that engine.

 

It weighs about 240lbs wet. Never sets the front end down so chassis tune up has to be on the money because there is no steering after you leave the line. We 60ft in the 1.22 to 1.32 range depending on track conditions.

Its 4.250 bore / 4.125 stroke. And yep its a hand full. It has snatched the handle bars out of my hands a couple time.

 

Here we go.
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This is going to be a fun build to follow. Interested to see where this goes.

 

I'm sure you are just useing it for mock up, but all the spectre silicone I have ever been around is non reinforced crap that will split at even modest boost pressures. Just a PSA.

The work you are doing is great and i love the project.

 

Agree with the Spectre couplers,. but you won't need much boost to hit your number, so they might hold. I get mine from Racepartsolutions.com

 

Is it finished yet? I am going to be extremely impatient on this build. It fascinates me

 

I new to all things turbo so thanks for the info on the spectre silicone. Working on getting oil out of the turbo fast enough. I'm feeding it with -4AN and dumping into a catch can with 1" hose. Then returning from catch can to the dry sump tank with a small snowmobile inline oil pump. More pics to come soon!

 

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I guess camshaft selection will be my biggest challenge. I'm used to running big N/A so not sure where to start with the turbo setup. Luckily this motor has two cams and I can change them one at a time. I also have a set of cam gears that can quickly be advanced or retarded a total of +or- 8deg in 2deg increments.

 

Your cams should be fine, especially if you can adjust them individually.

 

Here is my N/A cam specs...they seem to me to be pretty wild for turbo application. But you guys know more than me. What do you think?
Intake .700/[email protected] 118 LC
Exhaust .614/[email protected] 118 LC

Meanwhile I have struck oil, probably drain back issues that I am addressing right now.
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I put a brass tube in this oil port that runs vertical to the intake port and oils the top end of the motor. Seems that I lightly broke into it porting the head. Then added a little insurance epoxy to the side of the port.
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So now my complete running bike looks like this...lol

 

It may end up needing the duration backed off a bit. That's a lot even for 4.125" stroke. But if it has a good breathing turbine it may be fine.

 

How do I know if it has a good breathing turbine?

 

The dumb answer is the inducer of the compressor side is close to the exducer of the turbine side with an AR around 1. That is dumb generic, and super oversimplified, but ball park.
The smart answer a good flowing turbine is the turbine side that drives the compressor at better then a 1;1 pressure/drive ratio in the the operating range you are going for with considerations for boost response and threshold.

 

So cams can sort of band aid a non efficient pressure/drive ratio so to speak? I know that's not optimum but I have more cams than turbos...lol

 

You could say it that way. Basically if you can keep your backpressure:boost ratio at 1:1 or better, you can use a camshaft with characteristics more like a NA cam.