| juld0zer |
03-04-2015 08:40 AM |
because the consensus blames 'high' oil temperatures. that sells oil coolers, which leads to a placebo effect in most cases (IMO).
External oil coolers are neccessary for earlier models which did not come with the oil to water heat exchanger fitted in 2011 and onwards models, and hot climate models. But on 2011 onwards models, it's overkill for street driving - even spirited street driving. It does a decent job at keeping oil temps under 100*c under most 'normal' operating conditions.
The other issue is the VVEL system. It's a very capable system and a pretty complicated system. I have never taken off the accordion pipes and ran the engine but i've heard it here a few times that the throttle bodies are wide open most of the time except under certain conditions, such as to build brake booster vacuum. The same folks reckon the ECU sends a pseudo-TPS signal thru the OBD2 system so for those who monitor via OBD2 you'll argue like me that the TPS suggests that the throttle bodies are NOT wide open most of the time.
Anyway, my point is that there's so much misunderstanding of VVEL - and also its oil requirements (temperature demands, for example). VVEL works fine even at 100*c oil temp in hot ambients. A more aggressive throttle map does wonders. But throttle mapping isn't easy and it's a bit of a trial and error experience sometimes.
There is definitely a delay in throttle response - i have seen it on logs. The ecu registers gas pedal input very quickly, but it opens the throttle bodies slowly and it does not open it as much as you expect. Likewise for VVEL activity. This is where an aggressive throttle map helps but doesn't eliminate the problem completely. Throttle mapping with VVEL is difficult because the tuner or yourself never has complete control over the translation of gas pedal input to throttle activity (ie. throttle bodies and VVEL). The ecu still has the final say.
What i have tried to learn in recent times is why the throttle response seems to become noticeably more sluggish when the motor is fully warmed up vs when it is still warming up or when it is cold. This is based on oil temperature, not coolant temp because we all know that coolant temps get hot very fast on modern engines to promote lower emissions.
If anyone wants to take the lead, i'd like to see what happens if you insulate the centre coolant pipe (the big one running underneath the actual metal intake manifold from the coolant filler neck to the rear of the head). Wrap it in exhaust wrap or throw some Earls fire shield over it. This is the final frontier when it comes to eliminating heatsoak because it's after the IAT sensor and the ECU doesnt know what happens in this area. But this assumes you have an insulated cold air intake system that doesn't get heatsoaked severely at a standstill - so the guinea pig will have to sacrifice some engine bay aesthetics in the name of science.
The other theory i have is that the VVEL motors are overheating and they get sluggish as they get hotter. But it should log a fault because the target angle isnt achieved - i guess that depends on how the ecu is programmed, in terms of how long does it give the actuators to respond.
Anyway, good luck :) My Z is for sale but it's been one awesome experience despite the lows. This is an awesome community of very knowledgeable people and it is the best car forum i have been a part of to date. The support, the experience, the info and guides - all make for a great Z ownership experience. I hope i have contributed and made a difference in somebody's Z experience but i'll still be around!
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