6
As I've mentioned before, my plan for this bike was to tune the ECU directly, mainly thanks to the incredible amount of customization possible. I know there is open-source stuff out there, but Guhl Motors is only about 1.5hrs away from me, so I loaded the bike up and spent a day out in Lancaster...
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We did about 20 pulls, tuning the air/fuel for each throttle position (and there are a lot of positions that the ECU reads from). Actually, the sheer number of maps present in the stock ECU is almost mind-boggling -- every condition you can think of is basically represented, and if you take the time, you can really have one killer running bike.
After everything was tuned, we decided to do a final power pull before taking it for a road test:
It produced 200whp @ only 10000rpm -- stock it made a max of 152whp. Keep in mind, too, that on Guhl's dyno, the S1000RR & 2011 ZX10R make 170whp. The sound of the thing was absolutely unreal, and it shot one and a half foot flames out the tailpipe due to eliminating the stock fuel cutoff at the rev limiter. We were having some issues with the power starting to flatline above 10.5k, and that final run there actually tapered off up top, at which point I thought that we might be leaking some boost...
Now comes the part of the story that usually never gets told in builds like this, and will hopefully teach you all a valuable lesson about assumptions. More specifically, just don't make them!
Here is how the bike looks now:
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If you look very carefully at the last few seconds of the video in the bottom right corner of the screen, you'll see the coolant overflow purge. I wasn't sure at first what was going on, but after another quick pull with power now really dropping, we deduced that the head gasket must have given way. A compression test sealed its fate -- the first two cylinders were noticeably down compared to the others. So, after all the work I had done, the engine had to come out.
Before I yanked it out, though, I took it for a spin back at the shop. You could not tell it was down on power at all, as it was silky smooth and absolutely impossible to give any more than 40% throttle in first gear (with stock gearing, no less). The datalogger told the true story though -- the engine was seeing between 15-17psi at redline! On pump gas!
Now, I have designed quite a few supercharger systems over the years for all kinds of engines, and I can usually predict the final boost within a psi or two, but this bike completely threw me for a loop. It apparently just runs out of steam up top, causing the Rotrex to pack serious amounts of air into the cylinders. On pump gas, this is not a good thing.
3 mistakes ultimately led to this failure -- 1) no boost gauge as I thought I knew the boost curve ahead of time, 2) datalogger was not recording while tuning since we used my O2 sensor, and 3) I was not personally handling the tuning on the road where I would have caught the insane boost levels before anything bad would have occurred.
Here's where the gasket failed:
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The cylinders looked pretty good, but there's some discoloration and aluminum buildup at the top of the bore, meaning the pistons are shot. There's almost no sign of detonation, but the intense heat led to scuffing.
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Lots of work to be done.
Stay tuned for the (hopefully) grand conclusion to this build...
We did about 20 pulls, tuning the air/fuel for each throttle position (and there are a lot of positions that the ECU reads from). Actually, the sheer number of maps present in the stock ECU is almost mind-boggling -- every condition you can think of is basically represented, and if you take the time, you can really have one killer running bike.
After everything was tuned, we decided to do a final power pull before taking it for a road test:
It produced 200whp @ only 10000rpm -- stock it made a max of 152whp. Keep in mind, too, that on Guhl's dyno, the S1000RR & 2011 ZX10R make 170whp. The sound of the thing was absolutely unreal, and it shot one and a half foot flames out the tailpipe due to eliminating the stock fuel cutoff at the rev limiter. We were having some issues with the power starting to flatline above 10.5k, and that final run there actually tapered off up top, at which point I thought that we might be leaking some boost...
Now comes the part of the story that usually never gets told in builds like this, and will hopefully teach you all a valuable lesson about assumptions. More specifically, just don't make them!
Here is how the bike looks now:
If you look very carefully at the last few seconds of the video in the bottom right corner of the screen, you'll see the coolant overflow purge. I wasn't sure at first what was going on, but after another quick pull with power now really dropping, we deduced that the head gasket must have given way. A compression test sealed its fate -- the first two cylinders were noticeably down compared to the others. So, after all the work I had done, the engine had to come out.
Before I yanked it out, though, I took it for a spin back at the shop. You could not tell it was down on power at all, as it was silky smooth and absolutely impossible to give any more than 40% throttle in first gear (with stock gearing, no less). The datalogger told the true story though -- the engine was seeing between 15-17psi at redline! On pump gas!
Now, I have designed quite a few supercharger systems over the years for all kinds of engines, and I can usually predict the final boost within a psi or two, but this bike completely threw me for a loop. It apparently just runs out of steam up top, causing the Rotrex to pack serious amounts of air into the cylinders. On pump gas, this is not a good thing.
3 mistakes ultimately led to this failure -- 1) no boost gauge as I thought I knew the boost curve ahead of time, 2) datalogger was not recording while tuning since we used my O2 sensor, and 3) I was not personally handling the tuning on the road where I would have caught the insane boost levels before anything bad would have occurred.
Here's where the gasket failed:
The cylinders looked pretty good, but there's some discoloration and aluminum buildup at the top of the bore, meaning the pistons are shot. There's almost no sign of detonation, but the intense heat led to scuffing.
Lots of work to be done.
Stay tuned for the (hopefully) grand conclusion to this build...
unk
