Simmy's Naked Turbo Project

The ultimate hot-rod XJ...........

 

Really like that colour scheme.
Minty fresh.

 

Ultimate? not sure about that, I think you're overlooking @skylrk62 and his Turbo Maximus.
His high tech special might no longer be considered a hotrod though, that's a class unto itself.
Wait until I slip the 900 in, then we'll see

I always need a winter project up here and the 900 mill will fit the bill.
I think I'll build this motor with the standard 900 crank and con rod bearings.
I don't like the idea of drilling the additional holes through the 900 rods.
Thinking about getting an 891 cylinder block from Germany then ordering custom 68.5 mm forged pistons.
Go big or stay home, right?
Maybe in this case, going big you don't want to be far from home in case she blows.
The cases are currently at a local bike/machine shop drilling and tapping the tapered threads for the oil feed to the turbocharger.
Sandblast and paint then I can start this build.

 

You are an animal!

 

I went for a spin down my favourite country road this morning.
I love this bike!

 

Seems I've got more sorting with this thing.
Most of my testing to date consisted of rolling the throttle on in 5th gear down my local expressway.
Boost pressure would build smoothly to 14-16 psi until I had to back off due to ahem....social conformity issues.
Whenever I got on it in the lower gears it would keep rising, all the way to 22 psi.
It behaved similar to a clutch slipping and that's what I feared was happening.
So yesterday I backed the boost controller all the way out and boost conditions did not change.
It's clear now that the waste gate is staying shut and the controller is having no effect.
22 psi is where the BOV is opening and acceleration is impeded.
When I sent the turbo out for rebuild I just assumed he had tested the actuator. Perhaps not.
I'm going to hook up a compressed air source and try to get the actuator to move.


On the other front I got my 900 cases back from the machine shop.
I had them drill the crankshaft oil passage to accept the Turbo's oil feed to the turbocharger (red circle)
I pressure washed the cases yesterday, still not sure if I'm going to sandblast and paint as most of the areas that show are still good.
It's funny that the boss for this is present on most of the XJ's.
The boss on the cylinder block for the Turbo's knock sensor is also cast into most of them.

 

It's perfectly sensable to do that. Making the engine cases essentially be universal at the casting stage means you can make large single-runs for your working stock, instead of having to make a special small-run for that one model that needs those ports to be machined. Save a few cents per part, and you just increased profits significantlly. The change to the castings was likely done while the turbo was still in the on-paper development stage since those changes are not going to impact anything negatively.

 

I can fully recommend the 16” wheel configuration for these 650Secas if your not worried about original appearance. The handling is much improved, I’m having as much fun in the corners as I am boosting down the highway. Very stable bike.
The Bridgestone Battlax work good

 

I like to think Yamaha was planning to T/C their entire line.LOL
Interesting that both these bosses are tapped for tapered threads.
That’s why I had them done by the machine shop I’m sure the tapered tap would have cost me what he charged for the job.
I’ve never encountered any other tapered threads on a Yamaha.
I understand why they’re used as steam fitting is part of what I do it’s just not common on oil fittings. Rubber O-rings are better.

 

I stripped the pipes off and I can just barely get a look at the wastegate lever with the turbocharger still installed.
I put compressed air to the air line coming from the boost controller and verified the lever was moving.
I can't tell how much pressure I applied so I'm going to need a more accurate means here.
The actuator is supposed to stroke with just 8 psi.
I'll get my son to help, my 88 yo father hadn't a clue what I was telling him while laying under the bike LOL.
So the wastegate does open, just need to measure when.

 

I hooked up a cheap pressure regulator and managed to feed a consistent 10 psi signal and the actuator is definitely stroking the waste gate lever.

Now I need to verify my boost controller is working properly.

 

You can see how tight the space where the actuator sits.

 

Still trying to sort out why I'm not able to limit my boost pressure.
I bench tested the boost controller, its a very simple device with a ball, spring and a screw to preload the spring to the desired pressure, essentially an adjustable check valve.
I thought it would hold pressure until the spring succumbed then release pressure through the outlet (the outlet triggers the waste gate)
With preload all the way in it holds no pressure, as you can see in the pic 1 psi leaks through it.
I'm not sure if this is normal, still doesn't explain why I'm getting so much boost.

I reverified the wastegate is stroking pretty close to where the stock actuator is supposed to open.
Also verified there isn't a dead mouse plugging the waste gate silencer.
????

 

I took the boost controller right out of the circuit and ran the bike just as they came from the factory in 1982 without the power-up kit.
It worked perfectly, limiting boost to about 8 psi, happy things are making sense now.
Even at 8 pounds it's still a crazy fast bike!

I noticed the boost controller passes pressure out the threads when I had it on the bench.
Perhaps too much leakage there is not holding the waste gate open.

 

That could very well be. It's also possible that small pits have formed on the sealing surfaces. Is it possible for you to disassemble and polish the seat for the ball bearing, along with the mounting surfaces for the controller?
Also inspect the bearing under a magnyfing glass. Even though they are hard chromed bearings can develop ridges over time that prevent s good seal from forming.
As for the threads, I'd seal them with teflon tape. That should prevent the leakage you see there.

 

It's a ball bearing and the seat looks fine. Even if it leaked I'm getting 20 pounds of boost and that should depress that spring and bleed pressure through to the waste gate.
Holding high boost pressure is not the problem.

I don't think teflon is going to fit on these threads, teflon is good to crank threads until you have a tight seal, not for something which needs to be adjustable like this.
There's actually a very small hole in the centre of the cap holding the spring in which leaks pressure so the threads leaking is not going to matter.
I found this on the net and they talk about controlled leakage. I get that it's going to take testing to find the sweet spot but I've already had it adjusted as soft as it will go and still seeing 22 psi.

Ball-and-spring controllers: Later, more sophisticated ways of fooling that wastegate were introduced, like manual boost controllers that, internally, were made up of a spring-loaded steel ball that created its own controlled leak between the boost source and the wastegate. Boost controllers like these still bleed off boost pressure but are known for their ability to increase lower-end performance and turbo spool-up since they're able to hold that wastegate valve shut until the last moment. Adjustments can be made by cranking on a knob that stiffens the spring, which means more boost will be required to move that ball out of the way.
Manual boost controllers like these are known for their simplicity and ability to crack open the wastegate's control valve at the last possible moment. Their main disadvantage is they don't offer on-the-fly adjustability and that finding that target boost level is a process of trial and error.

 

Here is some info from the manufacturer about the hole I saw in the cap.

Centered Vent port
A small detail that makes the BoostValve better than many of the other boost controller designs. This allows it to release air trapped in the waste-gate line after turbo boost pressure drops. Many hours of testing led us to the correct port size.

 

as you can see it's a pretty simple device.
The BoostValve is probably mid-priced, they seem to range from $10 to $120

 

I was thinking about my comments more after recalling how my automatic brake bleeder works. It's essentially the same sytem, but at lower pressures. I think you are on the right track to getting her to run how you want.