As some of you know I headed off to R-Tech yesterday to find out why I was bleeding boost at the top end of the rev range - more specifically - the boost was dropping from 24PSI down to around 21-22PSI
Bare with me as its a bit of an essay but I'll hopefully add some pics when Photobucket behaves itself.
When I was at the RR day in January we had a look at the actuator and found it was sticking slightly so for yesterday Nick ordered in a Forge uprated actuator (yes I know how much I love Forge but)
So as well as having a turbo clean Nick fitted the new actuator along with the spring that was provided although Forge cocked up and supplied the wrong springs but luckily the springs from the 007P are the same and Nick had a few colours spare
Pic of the item in question - the spring nearest the actuator is what should be fitted - the ones next to it are what were supplied
So we started with what Forge provided - a yellow spring and here is what happened next......all the initial runs were done with my current Spec 2 map in place
Yellow spring - took it out and initially the car felt sluggish and unresponsive but the more I drove the more it seemed to free up. With Topher in the passenger seat doing the logging we headed for a blast up and down the M69. It become more apparent though that the more you drove it the freer it seemed to get, the car getting ever quicker although what was noticeable is that the car wasn't overboosting to 27PSI and then back to 24PSI. Instead it was either
A) surging as in starting from 21PSI and increasing to 25psi
b) would boost straight up to 24psi and just sit there!
After a approximately a 40 mile round trip we headed back and went to try the next spring, the initial thoughts being that an even stiffer spring was needed........
Red Spring - this was fitted and the test drive last until the 2nd roundabout - conclusion; its TOO stiff - there was no power from 2000rpm and then at 2700rpm it unleashed holy hell but even then it only spiked to 20psi. Needless to say it wasn't in for very long!
So the train of thought moved to a softer spring.....
Green spring - quite simply, if it wasn't for the fear of blowing my turbo across Hinckley I'd have this currently fitted. Saw regular spikes of 35PSI
in the short tun we did and I'm fairly sure if my boost gauge could read higher it would have gone higher. Quite simply it was the quickest the car has ever felt! It would just boost and go. Sadly though I quite like my current turbo and so does Nick and Topher so we headed back and put the Yellow spring back in and started playing with the mapping
First map was without being kind, not great. Lots of smoke on part throttle, felt like the turbo was being strangled, and then clearing its throat. So Nick started again from my original Spec 2 map
Nick took it for a drive first and came back not overly happy but thought I should decide for myself
This 2nd map was much improved, minimal pre-boost smoke and then gathering pace very quickly with minimal turbo lag, even on full throttle.
We did a couple of rolling road runs but all the runs were down on power and torque (averaged 170bhp and approx 290lbs ft torque in 4th gear) BUT I was now holding power where previously it was tailing off.
I set off home and for 90 miles it was superb right up until the point it threw me into limp mode
The reason behind this after chatting with Nick yesterday and this afternoon is simply this - the spring rate isn't suitable and therefore you get instances where the boost will surge as the actuator struggles to control what's being asked of it. No amount of mapping will ever cure this simply because the fault is mechanical
So to conclude - a new standard actuator will be fitted in a couple of weeks and further testing in both mine and Nick's opinion needs to be done to try and find the correct spring rate to suit a mapped car. It now seems obvious why the hybrid turbo builders currently do NOT recommend you fit this Forge actuator.
It's a bit of a shame if I'm totally honest - the potential is there, it just needs some more fine tuning and development work. An ideal solution would be a spring rate between the green and yellow. Nick said there are also some subtle differences on the rod of the standard and Forge actuator which could explain why it sticks initially
Hope that makes some sort of sense
