So, Friday was the moment of truth. Had I ruined the car? Would it be a nightmare to drive? Would it even make it to the end of the day?
The first session is two laps behind the van showing you the lines, then 10 minutes free time until the next session is ready to start. As I’d found out driving it on the road, it was easy to drive slowly whilst following the van, being able to leave it in a high gear and use the low down torque to cruise around. Then the van pulled in and, well, here’s a video of how well it went:
Started off with a gentle squeeze on the throttle but it was far too busy to make any overtakes… and I didn’t want to get sworn at when I got back to the paddock area. I decided to hang fire on opening it up until the longest straight on the circuit. I popped it down into second for the chicane exit (mistake)… put my foot down then popped it into fifth. Oops! A quick change down to third and all was well with the world again. I wasn’t at full throttle for long, but even with a couple of extra gear changes I could tell it was quick. Perhaps too much throttle travel, I don’t think I need such distance so may mount the cable up a level on the pedal.
I followed the next car around for a while as there was nowhere really safe to open it up again. 3/4 of a lap later there was sufficient space to go for it again and the turn of speed is incredible. The yellow Westfield is around 170bhp for reference, so about where I was with the GSXR throttle bodies. It’s the way it build speed from low rpms that makes more of a difference than headline power I think. It doesn’t need winding up, just point and squirt.
Once I was behind the orange Westfield (we’re at similar power/weight ratios) it dawned on me that I needed to learn to drive all over again. This time last year I did the same track day but with 130bhp, and I was able to attack the corners, brake late and generally drive properly.
No such driving this time! I was arriving at corners quicker than expected, completely unsure of where to brake and missing most apexes. And I wasn’t quite flat out!
The session was red flagged before I could either improve or spin off.
After the warm up sessions had finished it went into open pit lane for the rest of the day. I ventured back out but seemed more interested in going fast on the straight bits rather than braking and turning properly. I got a bit of a telling off for overtaking without consent. It was perfectly safe to do so, I had the speed advantage over most of the cars out there to get by on the straights without them lifting off but it was quite right I should be pulled up on it and vowed to be a bit more patient. Power does not equal consent!
Then it started raining, which confined me to the pits. I didn’t fancy a trip out in the rain. I vowed to go out when it started to ease off though to get some experience on a damp track. Of course, as soon as I headed for the track it started raining properly again! Never mind, I’d still do a few laps… with the age old problem of rain on the inside of the windscreen plus some on the visor this time. It’s quite weird getting to 90mph and above and the rain streaming from the back of the visor to the front!
Whilst it was wet, I was pretty slow. I just wasn’t sure how much grip there was, and for some reason didn’t really want to find out. I cruised around, watching other people to try and get some idea. After the first few laps it stopped raining, and the track dried surprisingly quickly. Then it was as per usual… very quick, not particularly elegant.
Here’s another snippet of a session before lunch with a few other Westfields in it. Better behaved this time, waiting for consent before overtaking. Also starring a bumblebee… ended up with two of them in the intercooler. Must refit the grill.
And here’s the last session I did, where I was much quicker than before whilst with a clear track. Still missing the odd apex, but a bit smoother and more in tune with the circuit.
So, in summary, the car behaved and went very, very well. I’m incredibly pleased with the results. Throttle response is, whilst not throttle bodies good, still pretty good. Here’s a graph showing boost over throttle position:
Ignore the 2.2bar value, it takes 0 as total vacuum, and is reading a smidge high. That should really be 10-11psi. I may get a separate pressure sensor to double check. Anyway, you can see that in the 1 second it takes me to feed the throttle in, it will happily go from near vacuum to the full required boost level.
Temperatures were solid, 89-94 degrees on the coolant and 33-37 degrees on the intake. In fact, the only negative I have is the exhaust sound. It’s a bit ‘wooshy’.
I won’t be changing back to the ITBs so may well sell them on. Future upgrades are in my driving ability, and perhaps a longer ratio diff. I didn’t feel the need for an LSD strangely, don’t think my driving style is quite there yet. Oh and a clutch… still on the standard clutch which was new when I built the car so handling the power for now, but I’m sure it won’t last that long.