Supercharged power ea81

[tweety]

It's been a while since I added a supercharger to my ea81 then took it off and sold it. I believe while running it the engine suffered some internal damage to a ring but I only found that out some time later.

 

 

The benefits of a supercharger over other boost systems is immediate engine response from idle upwards. It is relatively cheap to do but needs to be installed with attention to detail.

 

The supercharger selected was a SC12. This is a Toyota unit off an MR2 around 1990 vintage. And vintage is correct, too old in many ways. Bulky it has 1200cc and the SC14 is larger at 1400cc, the latter being 2" longer otherwise identical.

 

 

There are other SC's on the market like the Australian built Sprintex that have less drag and are much more efficient. These are found on Harley's, Honda Jazz and Mini's. If I was to go that way again that's the Sc I'd buy.

 

The build commenced with a Dellorto sidedraft carb. The tricky bits were to fabricate the manifold each side of the SC. The inlet manifold was easy, I bought a aftermarket twin carb LYNX manifold off a Datsun 1600 and cut it in two. The manifold between the SC and the standard ea81 intake was more complex as it was smaller and had to be made from scratch. It also has a blow off valve on it. This is to safeguard the whole unit if there was a backfire (and there were).

 

 

 

Once the SC has been mounted on this manifold then the SC mounts need to be made up. Basically it one long bolt that the SC swivels on if it was unbolted to the custom manifold. Then you need to seek out the belt drive pulleys. A supercharger's boost is dependant on its gearing. A 5 tooth pully around 140mm diameter will give you say 4psi boost. Not much eh....its deceiving. This much boost easily achieved 100hp at the fly (more on that later. But 7psi is the max if you want lots of reliability. More boost and you get a larger pulley on the crank. So this pulley needs to be on the crank and you'll need it to be secured well. I use 3 bolts but welding is the way to go. Then the idle adjusting pulley needs to be mounted and all lined up.

 

The pulley on the Sc was fixed. I took off the clutch. The reason for this is that a clutch system can only be used in a blow through system i.e. air, Sc, carbie, engine. but in the suck through system its air,carb,SC, engine. The blow through set up is the factory method and the carb would need to be pressure proof. This might involve different floats that don't collapse under pressure and the carb sealed. The suck through system is harder to tune.

 

My suck through system had 3 dyno tunes. Each time an air leak came about between the manifolds and their paper gasket seals. Eventually in frustration I used nitrile rubber home made gaskets and got a 100hp at the flywheel (82hp ATW)reading just before that leaked also. It was obvious my surfaces were warped.

 

The distributer was recalibrated for the SC. Timing was around 10 degrees.

 

 

As you can see the before and after dyno readings were impressive. About 33% more power and 30% more torque. Now the problem...

 

The biggest issue was economy. About half the economy of the non SC engine. That was in the end my main reason for taking it off.

 

 

 

In one last desperate measure I tried water injection. Nozzles the right size were hard to find. After much testing I found water injection simply made things more complicated with zero benefit.

 

So the verdict. If I was to go down that path again I'd go blow through, make sure all surfaces were milled flat, install a seriously modern SC screw type which is also much more compact and lighter. It would also fit under the hood.

 

Compression doesn't need to be changed unlike a turbo. There is no kick in like a turbo, just sheer power off the line. My trike would lift its front wheel easily at 25mph when the auto changed from 1st to 2nd and at 90kph was tempted to do the same into 3rd. It was enjoyable. Bare in mind there was 35kgms of SC and fittings over the engine which helped with the balance to do this.

 

[ihscout54]

Wow tweety, thanks for the read. You always have the coolest pics. Wheres the girls?

Im not a fan of forced induction on gas engines. But, then again, Im more of a keep it on the road junk yard kinda guy. What you have done is inspiring and our community needs more of this.

[turbosubarubrat]

I saw a trike the other day and thought of this. The one i saw had a v8 and 9" rear end though.

[tweety]

Thanks Turbosuperbrat,

 

Australian design rules have limited trikes here up until 2011. Then they opened them up with little restriction of weights etc. Because of that German trikes and V8's to a lesser degree have been entering the market more.

 

Hence in Oz, most trikes are the VW style. But that is slowly changing.