Following on from the discoveries in my last post, I've trimmed back the sensitivity setting on the E-Boost controller and voila... the stuttering during hard acceleration has stopped! I've now increased the gain setting slightly to compensate and to set the boost pressure right at the end of the amber section on the dash boost gauge (I need to check but this should be just over 1.20 bar).
I'm also now slowly increasing the gate pressure setting, which is the pressure at which the controller starts to open the wastegates. It's currently set at 1.05 bar, but in third gear at least there's scope to increase this. Since my 3200 GT turbos don't spool up very quickly, there's less risk of over boost so the gate pressure can be set reasonably close to the desired boost pressure.
I'm really happy with the way that the car is performing now. Acceleration is nice and steady, with a kick in the arse coming around 4000 rpm. Keep the revs below this and the car is very civilised, above this and its nice and aggressive with a quick throttle response.
The warm weather is testing the new oil cooler. Now that I'm driving it more I'm noticing how it performs. It's obvious that when being driven with decent speed, the oil temp is being kept pretty low as the water temp is maintained below 80 deg C and the oil pressure stays just below 5 bar.
Slowing down or stopping when driving through town, the water temp is elevated and stays between 80-90 deg C with the fan coming on alot. Also, the oil pressure drops to 2.5 bar. But as soon as you get some speed up and get air flowing across the radiator, the temp is straight back below 80 deg C and the oil pressure to just below 5 bar.
So my conclusion is that the oil cooler is working well. It has no problem keeping the oil temp low when driving at speed (with good flow across the radiator) and it manages to take the edge off the heat when the car is stationary, which is where the problems occurred on the track.
There's some noticeable additional load on the engine at idle though, particularly when the engine is cold. It's only small, but the engine is more prone to stalling now and a dab of revs is required to prevent stall when reversing with full steering lock. I will get this sorted though when the car is dropped off at the garge next week end... the idle needs setting a fraction higher I think.
The car is going for the annual APK (road test) next weekend and also to have a few things done:
- Re-fit the original distributor; it was replaced with a new one to check whether this was the cause of the stuttering, but since it isn't then the original can be refitted.
- The volt meter has stopped working completely, so the wiring needs to be checked.
- The idle needs resetting.
- Maybe fit the new springs. I'm in two minds about this though as the ground clearance around town is good at the moment.
- See if it's possible to modify the left wheel arch to increase the clearance a little and prevent the tire from rubbing on fast or tight right hand corners.
- Perform small service (oil change).
I'll try and capture some log data to show the changes in the boost pressure... I expect that the boost curve will be much flatter now at the top end instead of oscillating up and down. I think the top end is now performing much better as a result. Feels like the car is back at 330 hp, but I'd need to take it back onto the dyno to check this...