Mine backfires all the time and I don’t have a supercar. The cars in the game (even the regular ones) are speeding and racing so we can assume they’re running rich. I think this causes backfiring. It does in my car anyway.
That is actually wrong, real cars run rich on the idle and get leaner as the revs go up. The aim when tuning a fuel system is to choose the RPM range where the car will be used the most - usually 3000 RPM for a regular car and make sure the transition from rich to lean happens there making the mixture STOICH at that given RPM for the sake of economy and power.
Race cars that are tuned correctly have the stoich mixture tuned to be right all the way through the rev range with the use of fuel mapping ECU and electronic fuel injection, old cars with carburettors rely on jetting for idle, primary and secondry circuits and aim for a stoich mixture around 5-6000 rpm depending on the circuit.
The backfires and excessive fuel in the exhaust are not due to being rich at RPM, that is due to the camshaft overlap being increased in a race car - overlap means the exhaust valve is open for a longer duration and is still open for a little while when the intake valve is open so some fuel goes right through to the exhaust, this ensures a full combustion chamber of charge and the remaining fuel in the exhaust ignites causing the backfires.
In a stock car we shouldnt hear this at all regardless of the RPM unless it has a burnt out valve.
If your car backfires in real life and its stock, do a compression test, I bet you have one cylinder that is low, usually an exhaust valve not seating right - this will eventually lead to a burnt out valve, it will however sound cool if you dont care about power or economy.
Actually no, most EFI cars still run rich at wide-open-throttle due to them running in open-loop mode (ie not relying on an exhaust oxygen/lambda sensor for feedback). At part throttle they will cruise in closed-loop mode (trimming the fuel map based on the O2 sensor readings) to keep AFRs near stoich for fuel economy, but as soon as you plant your foot the computer disregards the O2 sensor (as it can’t react fast enough) and goes off the internal fuel map. Stoich isn’t where max power is made either (it is the ratio where combustion is most complete), and running lean at high rpm can be quite dangerous especially for high-compression or turbocharged cars (misfires or detonation can grenade an engine extremely quickly), hence the extra fuel being dumped in as a precautionary measure.
Remember that when you drive a car in a game, chances are you aren’t driving it like you do in real life (no-one redlines their car in every gear and drives around at 3-times the speed limit drifting everywhere), so you’re not experiencing the same conditions. Most people will be running in closed-loop stoich mode in real life for 90% of their driving time (except when idling), whereas in Forza you’re usually driving flat-out 24/7 unless you’re cruising looking for bonus boards or just enjoying the scenery.
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I completely agree with you, I mentioned they get leaner as the rpm goes up, i did not mean they run lean. I was trying to avoid writing a book on it
In the case of a stock car the manufacturer will always set a safe compromise close to stoich but nothing leaner as they do not know how it will be driven, and yes you are very correct on how it works 100% ( I always thought the new cars could get away with a bit leaner to improve power and economy due to the knock sensor being able to detect a ping before damage occurs and reduce the timing to a safe point? i may be wrong - efi is not my strong point)
Lots of different tuning ideas apply to lots of different situations, HP vs economy, in some cases economy does not play a part
I was talking about a racing situation where lean is desirable if you know exactly what is required from the motor and can make a safe tune for the situation.
I cannot quote how the circuit guys set up their mixtures or fuel mapping- not much experience there.
Im not a fan of EFI (im too old) but I have a long history of mechanical fuel injection in drag racing (methanol) and also a lot of carby experience but the formula is the same. Lean =Power / Melted pistons. Its a fine line that you have to cut close for the win.
My bad habits are all drag racing based. The car I was involved in had 54 fuel injectors - 16 of which were only used to richen up the mixture to get off the line without melting anything, after that they were cut allowing a very lean mixture on the edge of destruction for the remaining pass - we did replace the pistons after every 1/4 mile along with every other engine component and a new 7 plate clutch. This car did consume 100litres of fuel in a 5 second pass and distorted the piston tops almost every time. We ran a datalogger and every pass was diagnosed for exhaust temp, track temp, humidity, air temp, traction, rpm, crank rotations etc etc and changes were made to the tune for each pass based on the last one. By the end of the night we crept up on the leanest we could and thats why in drag racing the last run of the night is where records are broken. Also the last run is a do or die situation so all the safe tunes go out the window for the win.
Life in the fast lane huh?
(maybe now people will understand why the in game drag racing is a thorn in my side the way it is)
I’ve had my car checked out and it’s due to fuel in the engine due to direct injection. It’s the way the DISI is designed and they told me it can’t be fixed. Doesn’t seem to effect the car and I’ve been driving it for years. The downside is that my small hatchback only gets about 20 miles per gallon (14litres pre 100km) lol
Thats not good at all, it is possible some backfiring due to being rich if it is actually that rich can be possible. Any unburned fuel getting into the exhaust can detonate causing it, but realistically it should never become that bad and be said to be OK.
What I would do is remove the fuel inj system and put on a carby if it is a factory fitted design fault…it wouldnt be the first time thats been done to eliminate a poor design. I ditched the fuel inj from an FJ20 Nissan motor and fabricated a manifold to take twin DCOE Webers… a massive improvement.
Maybe you need to increase the air getting into the motor to make use of the extra fuel in there? i mean if your using it you may as well gain some power out of it
The backfire or popping and burbling type sound is pretty common on new cars in sports mode and is designed that way by the manufacturers. Mini coppers do it by design in most of the r56 models and the f56 models. It was taken out of the r56 models for a couple years if I recall and mini received complaints that it was no longer there so they added the popping sound back in the later generation r56 models. My 12’ mini jcw did it stock and after swapping out a lot of parts and doing some tuning to it.
It seems to be common in bmw’s as well. My old 11’ 335is had plenty of popping and burbling sounds while in sport mode. As well as my current 2016 m3 has plenty of popping sounds while in sport mode but not very apparent when in any other mode(I can hear it when the windows down and it’s not from the stupid v8 sound effects pumped into the car that can’t be disabled). The pumped in sounds nearly had me not get the m3 and go for a c63 instead but I just likes the m3 more and had a better lease rate on it.
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I was at the V8 Supercars event on the Gold Coast and those cars backfire on the change up of the gears. It is loud and if you haven’t experienced it before, it is a little unsettling. But, these race cars don’t use the clutch normally, it is a trigger on the sequential gear lever that cuts engine revs to change gear, while the driver does not lift the throttle. As expected, a little extra fuel, engine management etc and backfire. It could also be the Sugar-Cane Ethanol being used as well. On the beach-side chicane this was fantastic to see and hear. These race cars slide and hop over and through the chicane.
The racing Porsche’s from the Porsche Cup did backfire as well but not as loud or distinctive. As the saying goes, “There is nothing quite like a V8”.
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Just to quickly add, I think the game generally does pops well, the timing and all. I just wish there were more variations of it like in Horizon 2 - depending on what speed you go off throttle or shift gears, the pops would either flash briefly or more prominently at slower speeds. Excellent touch, though Horizon 3 uses a generic exhaust flash that looks the same no matter what speed you’re at. Variation in the exhaust backfire/flash intensity and duration would have been nice.