I thought I had hit the bottom last year, apparently not.
Spent the last few weeks doing fun stuff on the car, fire extinguisher wiring, hazards/heater wiring,
ABS sensor issues and various small but satisfying things as I waited for the weather to improve.
Last minute day booked last week for Friday as the weather was finally looking good, feeling positive as the car felt good driving around the paddock and passed the noise test with no issues and temps/oil pressure all looking good (4-5 bar under load)
However I noticed on the sighting laps that the car didn’t like being put under load when in a high gear, it felt like a light juddering as it got up to revs (2.5-3.5k) At the time I put this down to a flat spot due to the high comp / cams etc as it didn’t seem to occur at any other rev ranges but it was certainly in the back of my mind. Sorry for the watermarks but I feel the pictures help tell the story better..
Took the first 40 or so laps slow as I built up the revs and made sure temps looked good as well as doing a nut and bolt check on the frontend as most of that had been off to fit the engine.
I then started pushing the car, the chassis felt great, the frontend combined with the low weight and direzzas is just mega, optimal started to dip into the 54’s but I am no where near its limit. However the top end power was just not there, it was a weird feeling and it felt like the car got heavier / draggy as I went faster / into higher gears.
I assumed this was either the spoiler or me, took the spoiler off and looked to compromise the entry to clearways to try and get a decent exit to try and remove as many variables as possible. No difference in top speed, engine felt strong but something was wrong, just couldn’t work it out especially as the dyno was pointing to this engine being very strong.
Took lunch and started looking at the data, here is a comparison between the day and Oct 22 with the old car/engine but in the wet. You can see the massive difference in starting speed but higher finish speed by the start/finish line! As well as a near flat line of acceleration by the end (white line)
I noticed that my gear changes are a lot earlier in the current car, I assumed this was because I was going faster but I am actually changing much earlier in terms of wheel speed even though I change at the same revs / engine speed (second screenshot). I then remembered how it behaved during the sighting lap and put two and together realising that it was very likely the clutch slipping when under high torque. This would explain the disparity between revs/speed, the juddering and near flat lining of speed when in 5th gear. The dyno obviously loads the drivetrain up slowly hiding the clutch issue until it was on the track.
Not sure if this is due to the higher engine power or the lightweight
flywheel I put on has not bedded with the clutch. I am using my old clutch but the
flywheel face from memory looked brand new, happy I had diagnosed the issue I decided to keep going but ignore the lack of power.
First session after lunch, 3 laps in and just started to put the power down this happened.
Worst nightmare, I assumed at first it was either a coil/plug has been launched out of the engine or the clutch/plate had exploded. Pulled the plugs, #4 looked good, #3 looked good, #2 looked good and #1 looked like this:
It's quite obviously dropped a valve, I can also see bits in cylinder 4 as well but I believe that is common due to the
exhaust manifold design.
The irony of where it happened has not been lost on me with it being the following corner to my crash and right next to the pit entry meant I coasted almost all the way back to the garage. Why it has happened I don’t know, overrev? build error? component failure? unlucky? Probably all 4 as maybe I was pushing her probably a bit too hard on a fresh build, who knows. One thing to note is that the inside curb vibration seems to cause the final blow but I doubt that was the real reason.
So at least one piston is dead, head is going to be scrap, bores are going to be scrap, valves scrap, likely further damage depending where the valve ended up, you can see I disengaged the engine quickly before it died but it sounded horrific.
But fuck it I am going to buy a new engine and race this car, I have a potential candidate, stay tuned.