Cant get my engine to rev.

[PistonAddiction]

im only using the demo from the website (so I don't know if that could be the problem also.) Im trying to make a really high compression 5.4L inline 4 (that's all the demo gives you) but I cant get the engine to survive above 7200rpm. I cant get any engine to survive above 12.7:1 compression ratio. help please?

[ryandude2448]

Check the bottom end parts. Use the ones that say "High RPM"

[Kubboz]

Well, the bigger is the engine (the bigger is the stroke, precisely), the harder it is to rev. So, apart from using the bottom end parts best suited for high rpms, and increasing the bottom end quality, you can only make the engine's stroke smaller.

If you want the engine to have higher compression, you have to lower the required RONs in other areas. You can sacrifice the ignition timing, but it'll sacrifice power, so you need a good compromise there. You can also go for Direct injection, SOHC or DOHC valvetrain, and forged (or lightweight forged) pistons if you didn't already. If nothing else helps, make your fuel mixture richer. You also have to make sure the exhaust does not restrict your engine too much. Also, adjusting the fuel system quality helps. If you did all of those and still cannot go above 12.7:1, you will, again, have to make your engine smaller, except this time, lowering it's bore. Also, keep in mind that 15.0:1 compresion ratio isn't really achievable in Automation.

[PistonAddiction]

im running the best parts. 7200rpm is the highest I can get out of it. even when I turned to the quality up to +15. the crazy thing is that the engine is still making power. well over 700hp.

[PistonAddiction]

If 15.0:1 compresion ratio isn't really achievable then why they put it in the game??? its the same if they put turbo's in the game but you couldn't use them.

[Jakgoe]

Well, in the future, a 15.0:1 ratio might be possible, but it is not achievable at the moment. As for turbos, you can get them if you buy the preorder, along with I6s, V8s, and more.

[Daffyflyer]

Yeah, 15:1 compression is there as it may become relevant with better fuel systems if we add any, and if we have LPG, E85 and other fuels like that eventually, it'd also be relevant. Better to add it early just to make sure we've got all possible compression ratios covered.


If you're making a 5.4ltr Inline 4 there is no way you're going to get it to rev very well, the stroke is going to be so long that the pistons will be traveling at ridiculous speeds at 7200rpm. Inline 4s in road cars are rarely bigger than 2.5ltrs, for this very reason (and also to keep them running smoothly, larger I4s have a lot of vibration, and even a 2.5ltr one is going to be pretty bad for that)

[Reaper392]

15.0 compression is pretty easy to use in the later years for smaller engines, such as this otherwise quite reasonable I4 engine:

test 15.0 compressionRev0.lua

(51.78 KiB) Downloaded 260 times

However, it is very difficult to get it to work with bigger engines. This is made even harder because one of the ways to improve the compression that an engine can cope with is by using a more aggressive cam that is suited to high revving engines. With bigger engines it is a lot harder to get them to rev very high because of their bore, meaning that going for a more aggressive cam needed for very high compression will make the engine worse because it cant reach the high RPM that the cam is suited for. I did just about manage to get a maximum sized I4 engine to run without problems using maximum compression, but have a look at the quality settings and parts I had to use so that I could do this. I also got it to rev up to 8800RPM (it fails at 8900):

test 15.0 compressionRev1.lua

(51.32 KiB) Downloaded 235 times

[USDMFTW]

To add, bore size restricts compression as well.

[ThomasD1962]

Remember the Offy-engine? Had a 4.1L capacity with a 111mm stroke. They didn't rev much beyond 6500 rpm.

[PistonAddiction]

15.0 compression is pretty easy to use in the later years for smaller engines, such as this otherwise quite reasonable I4 engine:

test 15.0 compressionRev0.lua

However, it is very difficult to get it to work with bigger engines. This is made even harder because one of the ways to improve the compression that an engine can cope with is by using a more aggressive cam that is suited to high revving engines. With bigger engines it is a lot harder to get them to rev very high because of their bore, meaning that going for a more aggressive cam needed for very high compression will make the engine worse because it cant reach the high RPM that the cam is suited for. I did just about manage to get a maximum sized I4 engine to run without problems using maximum compression, but have a look at the quality settings and parts I had to use so that I could do this. I also got it to rev up to 8800RPM (it fails at 8900):

test 15.0 compressionRev1.lua

I cant for some reason download the file. I have used the quality setting to +15 and that made me gain about 1000rpm. but how much hp were you getting with it. I was making 750+ hp at 7200rpm. OFF TOPIC in real life the nhra pro stock drag cars are 500 ci. (8.2L) make 1200-1500 hp (depending on the engine builder) and they are running 118 octane so that's monster compression. there power band is 8500rpm to 10200rpm.

[Daffyflyer]

in real life the nhra pro stock drag cars are 500 ci. (8.2L) make 1200-1500 hp (depending on the engine builder) and they are running 118 octane so that's monster compression. there power band is 8500rpm to 10200rpm.

Yup, that'd make sense, they typically run about a 90mm stroke apparently, meaning the piston speeds would be waaaay lower than a 5.4ltr I4 with a 120mm stroke

[USDMFTW]

in real life the nhra pro stock drag cars are 500 ci. (8.2L) make 1200-1500 hp (depending on the engine builder) and they are running 118 octane so that's monster compression. there power band is 8500rpm to 10200rpm.

So, when can i put this into my family sedan in automation

[MattVRX]

Isn't the piston already doing 28m/s at 7krpm?
It's lucky to be surviving that, let alone 7200rpm. Cosworth managed to have their F1 engine survive 21,000rpm with about 29-30m/s, which is pretty much what your engine is hitting.

15:1 compression isn't too hard to use with the right settings. Pic related, you need to run it very rich and 2020 +15 all over the place, but usable and very powerful.

[PistonAddiction]

Isn't the piston already doing 28m/s at 7krpm?
It's lucky to be surviving that, let alone 7200rpm. Cosworth managed to have their F1 engine survive 21,000rpm with about 29-30m/s, which is pretty much what your engine is hitting.

15:1 compression isn't too hard to use with the right settings. Pic related, you need to run it very rich and 2020 +15 all over the place, but usable and very powerful.

that's a i6. im trying to make a 5.4L i4.