Just back from the first long tour on my rebuilt engine. Great road trip to the Scottish Highlands with a total of 2100 mi. We were lucky and always managed to source 97 to 99 Octane E5 gas (comparable to US 93 pump) so gas quality was not an issue. Was a perfect test for my carb and ignition tuning and included ca. 1000 mi cruising to and from the ferry port, mostly on speed limited roads between 60 to 80 mph. Rest was „spirited“ driving on back roads. Average speed approx. 50 mph, with lots of stop-and-go on the single track roads so typical for the highlands. Also some pretty fast passages going up or down remote canyons or „glens“ and some mountain passes. Engine performed flawless and total oil consumption was ˝ quart for the whole trip. Very happy with my carb setting and engine almost feels like on fuel injection. You can cruise along in 5th gear at 1200 rpm and accelerate up to red line without any hesitation or hick-up. Plenty of torque even at low revs and during the first drive in the Scottish rain I experienced wheel spin in the lower gears when hitting the throttle at 3000 rpm. Certainly needs more attention compared to the 2.4 engine. Not unexpected driving characteristic is quite a bit different from the 2.4, with strong and even pull across the range, while the 2.4 is more sluggish up to 4000 rpm but then suddenly comes to live big way.
AFR readings very stable between mid-12 to mid-13. Only when cruising between 3500 and 4000 rpm AFR climbed to high-13s to low 14s which first was a bit alarming. However AFR drops at the slightest touch of the pedal and after checking the spark plugs I see no sign of a too lean mixture. Total average mileage was 22.5 mpg (10.5 l/100km) with up to 27 mpg (8.7 liter/100km) when cruising at 60 to 70 mph. Guess nothing to complain about, especially as on some day trips my mileage was actually better than a 911 SC running a stock 204 hp ROW CIS engine.
First thing to-do after the trip was checking the spark plugs. Cyl. #1 is a bit sooty, but all other sparks look fine and just starting to get some nice brownish color. All-in-all no need to change anything but of course I will continue with some more tinkering. Will test my new colortune kit and check whether I can confirm and correct the slightly rich setting for Cy. #1. Will also finalize ignition curve with an idle advance of 5° BTDC.
