#6

[F5 Dave]

So you need to destroke it to 100 yeah?

Then is BoB still running at Ruapuna? Even if you have turbo lag it will blitz everything else.

[speedpro]

BOB is being advertised. Looks like it is happening at a meeting with races on the big track, but the BOB on the B track. Last I looked there was no permit listed.

Correct, it will be a 100 for entry to BOB. I'm not that interested in winning. This bike has been all about the build. I really need to sort out the BOB thing. Cricket and I are both keen to go. He'll ride the FZR/MB bike.

One thing I have been considering is donating the Wigram GP trophy back to the bucket community in the Chch area. It's a real bit of the local bucket history of Chch and might make a nice trophy if repackaged and renamed.

I've also been "chatting" with ChatGPT about the turbo. My main goal with this motor was to make 40hp which has been achieved. The stretch goal is 50hp which looks achievable running 20psi boost. Sketchy has run 20psi. He ended up with a 2-piece conrod but he thought that was down to a trigger error earlier on causing ignition mayhem which did a bit of damage. My engine is still relatively mildly tuned. There's heaps of fuel being tipped in and the timing is still on the cautious side. What might be a problem is injector duty cycle. Currently it's peaking at 70% which is an ideal maximum. I have run 100% with smaller injectors but supposedly that's not desirable. I could up the fuel pressure, there's still headroom with the pump. What would be cool is adding secondary, overhead, shower-type injectors but I'm too lazy to bother with the fabrication, plus I'm spending time getting my other bike going again.

[Sketchy_Racer]

BOB is being advertised. Looks like it is happening at a meeting with races on the big track, but the BOB on the B track. Last I looked there was no permit listed.

Correct, it will be a 100 for entry to BOB. I'm not that interested in winning. This bike has been all about the build. I really need to sort out the BOB thing. Cricket and I are both keen to go. He'll ride the FZR/MB bike.

One thing I have been considering is donating the Wigram GP trophy back to the bucket community in the Chch area. It's a real bit of the local bucket history of Chch and might make a nice trophy if repackaged and renamed.

I've also been "chatting" with ChatGPT about the turbo. My main goal with this motor was to make 40hp which has been achieved. The stretch goal is 50hp which looks achievable running 20psi boost. Sketchy has run 20psi. He ended up with a 2-piece conrod but he thought that was down to a trigger error earlier on causing ignition mayhem which did a bit of damage. My engine is still relatively mildly tuned. There's heaps of fuel being tipped in and the timing is still on the cautious side. What might be a problem is injector duty cycle. Currently it's peaking at 70% which is an ideal maximum. I have run 100% with smaller injectors but supposedly that's not desirable. I could up the fuel pressure, there's still headroom with the pump. What would be cool is adding secondary, overhead, shower-type injectors but I'm too lazy to bother with the fabrication, plus I'm spending time getting my other bike going again.

An update to my 2 piece conrod haha

I rebuilt it the same with 3LN rods and pistons and still at 20psi, but then torched 2 pistons between the ring land. The 3LN piston have very small ring lands, so I decided to swap to the 2KR pistons and rods as they have pretty much twice the amount of material between the crown and first ring and also twice the thickness between rings.

This worked great and I had the bike back on track at 20psi for about 5 test days so probably 200 laps or so. So naturally I decided to turn up the boost more to 24psi.

After one afternoon of testing, ejected another rod. Same as last time it turned the rod into an S bend then fatigue fracture is my best guess.

At this point i've run out of injector size at 95% duty, but one idea I had was to point one into the turbo inlet like the old indy car turbos did. Helps with reducing IAT and for me much easier than trying to fit shower injectors

It's now about to get sleeved down to a 100cc trying out some 3D printed pistons. With the smaller capacity, I think my injectors will now be okay, but I really want to push the boost to 28psi to recover the lost power from the reduction in capacity. With the reduction of flow im also considering trying to rev it a bit harder. I'm thinking of some titanium retainers and some custom valve springs maybe.

Too many cool bucket projects on the go, not enough time (and motivation)

[jato]

this is a cool thread! workshops all over the country building super buckets...
a thought is that with an engine getting in the vicinity of "bursting" adding boost will increase (mostly compressive) load on the workings at a roughly proportional rate to psi but adding rpm increases compressive and tensile loads at an exponential rate. it could be the more "reliable" engine has sky high boost rather than rpm.