Did you ever read my post about the M4 and 991 Carrera S on AC thread ? I uploaded both dyno sheets ( Dynojet ). The M4 I uploaded is DCT model, 2015 M4, stock with 91 octane fuel ( which would be 95 RON ) and it was done by reputable tuning garage in California and the dynojet power correction from wheel to flywheel explained in the dyno readout brings it to over 500HP ( divide by 0.82 )
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Regarding octane, I know there's differences of fuel quality standard used between continents and I talked about octane (RON) used in Oz, I was also talking about JDM cars I drove a lot in Australia. Any lower than 98 Shell and cars like Skylines are more prone to detonation ( it was scary putting premium on these cars ), especially when running non stock boost levels ( most are
, at least either of these exhaust, intercooler, BOV, ECU, S-AFC etc ), and I even had to take extra
precaution putting octane booster to keep detonation at bay, because I know the Shell 98 is not really guarantee.
JDM cars recommended fuel is 100 RON for max performance, though it can take lower, but the lower the fuel, it will go rich ( burns more fuel ), retard the timing and power loss ( when ECU detects knocking/detonation ) Turbo cars are more sensitive to fuel quality + power increase/decrease than NA cars.
Sorry if I didn't put explanation about the M4 and Carrera S which were tested in the US.
As for Lotus Carlton, here is a dyno session with stock car ( dyno dynamics which often reads lower than dynojet ) :
and another dyno run with different dyno, 381HP at the wheel, which should translate at least 420HP at the engine ( using 10% loss )
Back then, there's one Carlton imported in Australia that were up for sale asking for astronomical price, and the owner said about 430+HP with around 0.1 Bar boost increase, 0.8 Bar boost , apparently his Carlton ran 0.7 Bar stock boost, this is why I wrote 420-440 HP stock engine HP approximation. The Carlton max boost stock is 0.98 Bar before ECU cuts injector pulse.
What often bothers me is manufacturer claims often just a number, no explanation in condition of measurement, like dyno ( engine or chassis ), fuel etc. The JDM 280PS gentlemen agreeement was even worse