CoralDoc

The latest evolution of my car was forced by the untimely death of #3 piston in my BP-4W engine at Daytona due to the failure of #3 injector. The car has well over 15k track miles and 11 years of service, with most of that time mildly force-inducted. I moved from NASA TT5 to TT4 this year, removed the inlet restrictor and tuned for more power. It was peaky power, but still a lot of fun.

Exit BP-4W and enter BP-Z3. The VVT motor has improved midrange and the same top end (running it with the VICS intake, not the VTCS intake). Here is the latest dyno, comparing the two engines (red = BPZE and blue = BP4W) with both slightly de-tuned at the top end to meet classing restrictions.

Under consideration is changing to the Rotrex C30-84 supercharger and adding an external wastegate to obtain a flatter power curve. NASA rules do not penalize flat power curves per se, but there is a forced-induction penalty in the form of fewer data points in the RPM band to calculate an average horsepower measure for your car.

rascal

That’s a shame, though looks to be bigger/better replacement..

Do you know what caused no3 injector to fail?

CoralDoc

11 years and 15k track miles of use? I had the injectors serviced at a local shop that specializes in injector testing and cleaning, and they said that one injector flowed but was not producing any type of spray pattern. The other three injectors had decent spray patterns, but were also not flowing sufficiently (though more than #3). They cleaned up just fine, so I suspect some type of particulates clogged that unlucky injector causing the cylinder to run lean. I switched to E85 about a month earlier, and there was a new fuel filter installed shortly after the switch.

Here is the spark plug from #3. The other cylinders and spark plugs looked perfect.

rascal

Yikes, That's one toasted spark plug....

I also swapped to E85 in the last few months, and have run two filters through it so far. I might do another (and inspect the current one) to see if there is any junk floating around, pretty savage outcome from a relatively minor issue..

MX5RACER

I’m case anyone was curious, this is what the piston looked like.