Interesting results Mark. I have used OBD2 readings to check efficacy of cold air inlet mods on my Roadster. On this car there simply isn't enough space above engine to run a large bore (4 inch) inlet pipe to front of car. An aluminium radiator also reduces space available above. Have therefore resorted to interfacing with nearside inward facing side louvres on that bonnet, after cutting off and sealing original inlet at bottom of air box that drew air from rear of engine and adjacent exhaust manifold.
![[Linked Image]](https://i.imgur.com/eNFLTh6.jpg)
Results show that IAT now remains within 1°C of ambient, unless car is stationary in traffic when IAT can run to 5+°C above ambient. I think you just have to accept this though.
I'm not in the least concerned with cabin heater unless it could be made hotter, and I don't have air-con option thankfully. Winter time heater output remains adequate rising noticeably with fan on when in 30 mph limit. Would be nice to have a little more in reserve though. At my age I'm concerned about comfort more than specific temperature readings
Regarding adding heater matrix bypass as per current thread. My own view based on above is it's a waste of time unless you have air-con option. If you do have this though, based on GoMog findings, then a heater bypass would seem a good option when air-con required.
Please do not consider a simple shut-off though. The coolant flow dynamics particularly in the area adjacent to thermostat where heater return pipe is fitted should not be changed. This would require as a minimum a three way solenoid valve plumbed into heater matrix inlet hose. Better still a four way on/off solenoid valve fitted in parallel with heater matrix inlet and outlet allowing in either case a full flow in these pipes whether heater functioning or not.
