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Discussion in 'Your 250cc Projects' started by Mike Green, May 9, 2020.
I spent about an hour on the track at Edgecumbe. It was a hot sunny day and my mate was having trouble seeing the image on my video camera which he had also never used before. The bike mostly ran OK with only a bit of an oil leak. I've given it a good clean and ran it in the garage but where the oil came from is not obvious. I'm running a Link ECU which has data logging built in. It was interesting how little I used full throttle and also how little I actually revved it. Regular revs were only 13-14,000 with a typical squirt only going to 16,000. There is just a bit of a burble in a few places but it doesn't have any effect when riding it. The motor is very sweet to ride and runs crisp through the rev range I was using. Even down around 6,000 it pulls clean. It was a bit lucky I think but it started with the first pull on the back tyre. I simply had it on a stand, selected 3rd gear, and spun the tyre and it fired right up. Stupidly I had the AFR Lambda gear removed so didn't log any data. The good news is that it looks like I'll be back to the dyno over ANZAC weekend. Hopefully it'll be good enough to do a few power runs and fully sort the fuel and ignition.
Spent the day at Hampton Downs on Sunday. It was the first time on a track for 9 years or so, apart from Edgecumbe a few weeks back. The bike seemed to run OK but still has a slight oil leak somewhere around the head. It's not much but is enough to coat everything on the left.
The bike ran OK but unfortunately with the short notice for at least one race and the time it takes to warm up I was taking it a bit easy at the start of a few races. Only the last one was it warmed up when I went out.
The fuel pressure regulation is still a problem. Most times I turn it on the pressure needs to be adjusted, sometimes up and sometimes down. Despite having run it on the dyno and got the fuel map in the ballpark, at 100% throttle it was still lean around 13-15,000rpm. It was REALLY lean according to the log so a bit surprising it ran as well as it did. Definitely not quick but it ran OK. I did check the fuel pressure at one point and found it a bit low so adjusted it. The data log for the next race shows the AFR not as lean so the leanness may simply be a fuel pressure problem.
Interestingly, Ellie to whom I sold Cricket's CB125(the other #6), was on track in the same class. There was very little difference between the 2 bikes. I was glad to see the CB going well. I'd fitted a 150cc kit and done a bunch of machining to get things just right and I always had a nagging worry that it might go "boom" but it was going really well, even the gearing was more or less spot on for HD.
Anyway, it was a good day. There was a good crowd of various bikes and a few new and newish bucket racers. I think Ellie has only been to one other meeting, I was back, and the 2 guys sharing an FXR, the old club bike, were parked next to Rob and I. The weather was near perfect and as far as I could tell everyone had a good time, with maybe one exception, being the person taken away in the ambo.
I had a camera mounted on the tank. The view was obscured by the instruments but you get a bit of an idea. I was only revving it to about 16K and now and again 17K. It sort of faded out which would have been the AFR going lean. Lambda was going to 1.1 or so which is plenty lean, especially for thrashing.
Had an enjoyable and successful afternoon at ESE with the FZR on the dyno. I was doing runs at various throttle settings and logging the AFR so adjustments could be made to the fuel map. I made up a "desired lambda" table and the ECU can do a comparison of "desired" and "actual" lambda and also calculate what adjustment is required to make them match at every TPS position and RPM point. You only have to hold the throttle position and let the motor rev through the region of the fuel map you are tuning.
It's not perfect but does work very well.
One reason I wanted to do this all again is that last time resulted in a peaky looking fuel map. What I expected was a progressive change in values. I was very careful today to concentrate on the locations that had peak values with lower values each side.
The outcome was a fuel map with a ridge of peak values at 7000rpm and another ridge of peak values at approx 14,000rpm and partly into 15,000rpm. It doesn't seem to be an error as I went over it more than once.
I suspect it might have something to do with peak power supposedly being at 14,000rpm in standard trim. If this is correct it does highlight the compromises made using carburetors which will be incapable of fuel delivery with the peaks and troughs.
The attached table has the peaks highlighted. In the graphical version of the table it is REALLY obvious.
I have been informed that this is not uncommon and that Yamaha have played with ignition advance to smooth delivery on other models.
After a bit of thought I've decided that attempting to get the fuel map smooth was probably a waste of time. With the turbo installed there should be a lot less resonance which will be contributing to the fueling requirements. I'll probably have to smooth the map and then adjust for boost from there. We'll see. I've already started the process of installing the turbo.
The electric water pump has been fitted to the back of the block since I last had the turbo on the bike. The pump interferes with the air filter and it's mounting flange so I'll have to put a bend in it. The end goal will be to put the turbo directly in front of the exhaust ports. This will reduce heat loss and retain heat and therefore pressure in the gases before entering the turbo which will obviously help things along. I'll get it going first and build the new manifold on a spare head. Relocating the turbo will tidy and simplify the plumbing plus make it easy to add an intercooler.
It's definitely a bit "busy" on the left at the moment
A bit more progress on the new turbo exhaust manifold. In the end I didn't need a guide to centre the pipe on the boss. Instead I made the boss as I had drawn it with a recess that the pipe fits into. I dropped over to Kev's place last night to chat about how this was going to be assembled. In the end Kev machined the taper in the boss, 26mm-28mm, and then the recess. After tacking each pipe to a boss we then jigged it up on the bench and scribed the cut lines. If I had cut it in the mill instead of with a cutoff disc in the grinder it would have been spot on.
The good thing is that cutting the pipe so that the 2 halves fit together leaves the exit a bit small so I'll have to cut it back till the size is correct. Giving it a quick eyeball the turbo was going to be a bit close to the front wheel but there is a couple of things I can do if required.
A small video about the new exhaust.
Keep 'em coming Mike.
Been following this project and have to say it's pretty damn cool what you're doing.
Wondering if tack welding the pipes end to end (one 180deg to other and offset as necessary) then cutting one line through on a bandsaw would have given you the desired fit after "un-tacking" ?
I'm dabbling a bit with basic hobby engineering so trying to learn different ways. If I did that with angle grinder I know I'd have to chuck both pieces away afterwards
You are going to have to make some special clamps to hold them to the head also.
The clamps are already roughed out and a flange to weld on the pipes to bolt the turbo to. hopefully wil make some progress tomorrow afternoon.
Got a bit more done over the weekend. Kev gave me a piece of aluminium. In the lathe I faced off the top and bottom so they were flat and parallel and spun the exterior to clean it up so I could get a good reference off it. Drilled a 10mm hole through the middle to clamp it on the mill. It was then clamped down on the mill, clocked up to locate the centre and then offset in the X axis to the distance for the flange bolts which I then spotted. Took it over to the drill press and drilled and tapped the mounting holes. Once that was done I mounted the first flange on the alloy and mounted it in the lathe. I drilled the centre hole using a big drill and then bored it out to the desired size. I actually went up .25mm in size to get it over the pipes. The 2nd flange was simply a repeat. The good thing is that now I have the alloy boss I can easily make more flanges with good accuracy. The pipes need a bit more taken off the ends where the turbo mounts. It looks like it's OK but until there is a slight gap it's hard to tell if the pipes are under any stress. Pretty happy with how it's coming along.
I have decided to get my own machine tools. A good friend gave me his drill mill which I have used previously a very long time ago. I'm still looking for a lathe. The mill is 3phase and I've decided to go with a rotary phase converter so a 3phase lathe is fine as well. It turns out that I could get a 240v 32amp supply to the garage. I very much doubt I'll need anything like that, but it's nice to know.
I'd like a bit more info on the rotary phase converter. Do you just need the one to be able to run multiple tools? Does it run on one circuit/hotpoint and switch between tools as needed? I have a 3 phase car hoist that I need to get sorted on my single phase supply but thought rotary phase converters were pretty pricey. Was looking into the VFD option although there would be hp losses.
I've been trolling through TradeMe and the price that 2nd hand lathes are going for is a bit crazy. If I can swing it I'll get a new 240v 10a lathe. It'll be a bit smaller than most of the 2nd hand ones I have seen but will be big enough for the vast majority of my work. At the moment I have my eye on one with 320 swing, 600 between centres, and 38mm spindle bore. That changes supply requirements. I'm still going with a 32A 240v supply to the garage as it will be useful if we ever lose our minds and buy a PHEV. The rotary converter is now not the best option as I will only have one device to connect. You only get about 70% of the torque with a VFD but that really will not matter with what I'm doing. My mate Dave is looking at prices for Hugong welders for me. Even a 200a AC DC HF Tig only needs a 15A supply so it will be a breeze.