gptoyz

so we are shaking down my friends new build @ button willow running CW1.

The car is an Ap1 with an ap1 engine; no ecu mods; test pipe, stock air box; HKS exhaust

on the initial out lap and first hot lap the vtec engagement is spot on.

on the 2nd lap; the vtec either engages way late >7k or not at all

currently no checking engine light

What we did notice is that the heater is nice and toasty on lap 0, 1 but towards the end of the session the heater spits out mildly hot air (outside temperature 88 F)

We don't think there is air in the cooling system but right now we can't be sure.

What determines vtec engagement other than:
-coolant temp
-sufficient oil
-rpm
-throttle position

Would late vtec engagement @ WOT trigger a check engine light?

AE_Racer

Sounds like it could be the coolant temp hampered by an air bubble. Any recent work on the car?

By saying sufficient oil I assume you mean sufficient oil PRESSURE. You could have plenty of oil in the car but if the pump/sump isnt doing its job or it has a blockage between the head and block then its not gonna engage.

Not sure on the s2000 but on older hondas the VSS or vehicle speed sensor must be operational as well.

bgoetz

Sounds like air in the coolant. Hope you didn't overheat and not realize it.

gptoyz

We were watching the dummy gauge and it never wavered.

Assembly of the car literally finished the night before so today was a shake down

99SH

Assuming coolant temp isnt the issue, check the solenoid to see if it's getting trigger at the RPM you expect. I'd run a test light to the solenoid and drive it around the block. You just need to start pruning the fault tree one item at a time.

gptoyz

Well we aren't at the track anymore so now we have all of our tools, diagnostic stuff and what not at our disposal.

We were trying to pique collective troubleshooting while we were out there as to what we could determine with available information and tools