So glad to help you 
You are doing a amazing job.
Thank you very much!
I have a similair problem or the same problem in the Muscle Car Mania scenario from the V8 engines.
The engine has a RON of 90.9 and when I increase the ignition timing from 74 to 75 or the compression from 9.2 tot 9.3, I am losing like 80 kW, even if you compensate for engine knocking by making the fuel mixture thicker. Adding more fuel doesnāt seem to make up for my lost power.
When I switch from flatplane to the normal v8 and back again, the issues is fixed, until I start fiddling again with the compression
Here are the specifications of the engine:
(gold medal spoiler alert!)
V8 Flatplate aluminium block
Bore 84.1
Stroke 105.5
Cast Iron crank
I beam steel
Forged pistons
Direct acting ohc 2valves
Compression 9.2
Cam profile 70
Natural aspired
4 Barrel twin carburettor
Performance intake
Ignition time 74
RPM 5500
Long tubular single exhaust 3.00 inches
No cat or any mufflers or a bypass valve.
Bottom tech 3
Top tech 3
Fuel Tech 8
Exhaust tech 3
Edit:
Fuel mixture is 13.7
Iāll try to reproduce it right now.
how is the fuel mixture you are using?
and these problems I report initially still occuring 
Bullets: we were able to reproduce the error with the engine file you gave us previously, but weāve not been able to see what is causing it.
What we found out is that the problem is connected to the saving of the engine, thereās not even any need to change any of the sliders.
Do you have an engine you could share that was completely built from scratch in this current version (open beta) that has that problem?
I have managed to recreate the same bug with a new file for the scenario, the game has the latest patch installed, the specifications from the engine are the same. I simply moved the older file to another map.
When i started the game, the gold medal for the scenario was gone and I had to create an engine from scratch. After recreating the same engine and increasing the ignition timing without adding more and with adding fuel, I am still losing 80kW.
The power and torque curve of the engine with 250 kW and the one that can produce about 170 kW, are the almost same, until it hits about 3300 rpm. Thatās when the engine with 250 kW is still increasing in torque and the other engine loses torque and thus power.
V8Scenario11.lua (36.9 KB)
Rob the problem is not after save the engine. It occur while build it.
The difference after the update is that when I save the engine, close the designer and check the engine specs on engine management I you note that something is not righ.(the specs are totally wrong comparing to before I close the designer)
Here is the engine. I built a naturally aspirated yesteray and made a turbo version now.
1.3L Scion Turbo BugRev0.lua (79.2 KB)
Thank you for the engine, it does as I expected:
- revise engine (no changes!) -> run engine -> doesnāt work
- revise engine (no changes!) -> run engine -> save engine -> run engine -> does work
sorcery!!! 
lol 
So, this is an apropriated compression or this still a glitch/bug?
Definitely a bug, both cases should have the same result. We need to dig further ;(
ok
Thanks for your attention Rob 
Iām bumping this thread as I suffer from a similar problem that only seem to happen to me on the āflying debrisā and the āspinning fasterā scenarios. I am on the public build 1323 but I did start these missions in the build 1198 (not sure if thatās a factor). Everytime I improve my score and I make another test, the octane jumps up (for example, in spinning faster, it goes from 90.8 to 92.1), even if I didnāt touch anything. If I quit and reload the mission, it drops back to normal, until I improve the score again and make tests after that. However, I found out something weird when I looked back at the engine parts in āspinning fasterā : for some reason, the short cast header type has its max power value shrunk from 188 hp to 108! And all the other header types had their max power value changed as well. If I put long tubular headers, the octane goes back to itās previous value, but the score is lower due to the increased cost.
Could it be a glitch related to the bore value ?
EDIT : I just made another weird discovery in the flying debris mission : if I change the stroke value after the octane jump and I make another test, it drops back to normal. However, if I make other tests after that, the octane jumps back up again (unless I change again the stroke). So there must be something going on with the displacementā¦
I can confirm this was happening to me too. (once you set a new record, the engine go āberserkā) I forgot to pivotal it.
I have managed to figure out what happened in the Muscle Car mania scenario and the Da-Car scenario with my v8 engines losing power. I was losing power in both cases because the push rods and the direct acting valve headers were suffering from some bug which involved the calculations of valve float. In this case it was occuring starting around 3200-3500 rpm, they were turning yellow/orange/red depending on the rmp the engine was running. Whenever the bug occured, it didnāt affect the reliability of the engine for some reason.
If switching from flatplane to crossplane and back again, the power would be normal, until I start fiddling with my engine once again.
Can you upload an engine where that happens and give us the steps to reproduce this behavior?
I have managed to get across this bug once more, but strangely, it might not be a bug in the valve headers, but in the long tubular exhaust pipes / exhaust pipes from the v8 flatplane. The amount of power they can handle seems to drop from 400 kW+ to a mere 170kW+ for no reason.
The bug does not occur always, but if you change the ignition time and the amount of fuel injected, it will likely occur. Changing compression can also work.
V8Scenario6.lua (37.7 KB)