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Various unrealistic OHV engines balance observations


Dear Automation team

I hope that you have a chance to view this topic and our grate game even better and more realistic

I notices that in the game OHV engines power and torque are massively under rated , Maximum RPM speed is really slow , cost is very high exceeding DOHC 4 valves ,VVL ( with the same power rate) , and octane rating is very high at leas by 1:1 compression ratio in addition to Hi gas consumption in Fuel Injected variants.

It seem that the team Ideas about OHV engines is based on the area from 1975-1990 while these engine weren’t always had that standard ,

Please check the below examples and feel free to review the below Wikipedia links if you have a time :slight_smile:

A- Pre 1972 OEM Factory engines

1- RPM exceeding 7000 RPM even in BIG Block engines 7.0 Liter (427ci) , 100mm (4 inch) strock. ( 427 (Z11)

2- OHV engines use to run in hi compression Ratios exceeding 11:1 compression ratio

B- After 1997

Notice that all these engines are mass production engines for ( Sedans , pic up , SUV s , sport cars ) , Normal exhaust systems , No long tube headers .

1992 - GM LT1 5.7L 300 HP @ 5200 RPM (5800 RPM Reline) compression ratio 10.4:1
1996 - GM LT4 5.7L 330 HP @ 5800 RPM (6300 RPM Reline) compression ratio 10.8:1
1997 - GM LS1 5.7L 345 HP @ 5600 RPM (6000 RPM Reline) compression ratio 10.1:1
2002 - GM LS6 5.7L 405 HP @ 6000 RPM (6500 RPM Reline) compression ratio 10.5:1
2005 - Chrysler Hemi 6.1L 425 HP @ 6200 RPM (6400 RPM Reline) compression ratio 10.5:1
2006 - GM LS7 7.0L 505 HP @ 6300 RPM (7000 RPM Reline) compression ratio 11.25:1
2011 - Chrysler Hemi 6.4L 470 HP @ 6000 RPM (6400 RPM Reline) compression ratio 10.5:1
2014 - GM LT1 6.2L 460 HP @ 6000 RPM (6600 RPM Reline) compression ratio 11.5:1




I agree that current engine designer overly simplified and unrealistic. Even Killrob has said that the current engine designer has only around 3% of accuracy* 2 years ago.

There will be a new engine designer, however, with more header choices, more sliders and more parameters**, we will have a more accurate (I cannot say how much though, as the engine designer revamp is not implement yet, and I am not a dev) and more flexible engine designer.


Thank you very much for the well-sourced feedback, that is helpful. Let me address some of your main points.

OHV maximum RPM speed is really slow

I think you are referencing solid lifter setups, which of course do rev a lot higher, those are not the one in game though.

cost is very high exceeding DOHC 4 valves

I can’t confirm that at all. In an example engine I have $620 material cost for DOHC-4, $566 for OHV. 22.5 production units vs. 15.5 and 35.8 months engineering time vs. 24.7. The pushrod engine will be A LOT cheaper to produce and engineer. Maybe you are playing the Kee engine version and reference MOHV? That has been removed from the game in the UE4 version. For that the material costs were higher due to the fancy materials used for the valvetrain of modern LS motors.

octane rating is very high

Yes, and compared to other engines it should be due to the less optimized path the air fuel mixture has to take to get into the combustion chamber. That is an OHV and DAOHC issue. If the compression ratios overall are too low is arguable though.

Please note that because of American automotive history, they are obsessed with OHV engines and their tech does NOT reflect the norm. In order to build anything American style, assume that you need to put about +10 quality into the top end section. That is about where the US manufacturers were in the 60s with their OHV setups.

Valve Float!

It’s worth noting that, while it doesn’t help the issue with modern OHV engines, that the reason all those 1970s engines show such high outputs is probably that they’ll be Gross rather than Net HP, so I’d expect it’d be about 25 - 35% less power than is quoted for them.


Wouldn’t the more convoluted path act sort of like a simplistic EGR? Always seemed to me like the main trade off with OHV was giving up volumetric efficiency, but you gain more displacement vs engine volume.


I think what actually mostly contributes to the octane differences is theoretically better combustion chamber shape possible in OHC engines. But how accurate that is I’m not 100% sure.


Thanks so much for your prompt response :slight_smile:

Dear Killrob

This is exactly what I am talking about the +10 quality , its leading to make the OHV engine much expensive than DOHC ( in the same Power range) specially for the new engine model +2010 Its to nearly impossible to simulate the newer engines with realistic cost and Fuel economy .

2011 - Chrysler Hemi 6.4L 470 HP @ 6000 RPM (6400 RPM Reline) compression ratio 10.5:1 ( Multi fuel injection )
2014 - GM LT1 6.2L 460 HP @ 6000 RPM (6600 RPM Reline) compression ratio 11.5:1 (Direct injection )

In 1994 LT1 5.7L OHV V8 engine that introduced in Chevrolet Impala SS and caprice has 10:1 compression ratio require regular 87 octane (AKI)
While V12 M120 which powered the mighty Mercedes-Benz S600 has 10:1 compression ratio require Premium 91 octane (AKI)

In addition the 5.7 OHV LT1 have better fuel economy than 1995 5.0L DOHC V8 that powered the S500 , both cars weighted almost 2 tons .

You can also find the fuel consumption between the 400 HP 6.0L OHV V8 corvette , Porsche Carrera and the Ferrai F430 , please notice the efferent in the engine sizes and the fuel consumption :slight_smile:



Ahh I see where the misunderstanding about the cost is there. It is necessarily balanced for the campaign, where your company would have +10 tech pool, which means that you build an engine with +10 quality in top end for the price and effort of it being at zero! :slight_smile:

Regarding fuel consumption, that is a difficult issue to address, unless you build exact replicas in game and then compare stats. Even then we could probably via tuning of it somehow make it realistic. The point is: it requires a lot of in game and out of game data. Overall we seem to be in the ballpark though.



Dear Killrob

Thank you so much for your understanding I really appreciate your concern :slight_smile:


Thank you for the effort put into your posts, that is exactly how we like people to address potential issues with the game.


I have a slight problem with that.

So if we need to have a +10 tech pool on the top end to build a semi accurate modern OHV, then it would still be better to build a DOHC engine as the tech pool would still apply.


That is theoretically true, but then wouldn’t they still be more expensive?


Yes, but you have returned back to the original problem where while the OHV is cheaper it is not anywhere near as good in power, rev limit, and fuel economy, and then can now build better than current DOHC engines.

edit: ill know more when I get a chance to play with the concept a bit more.


Am I understanding correctly? Since the same tech point category applies to all the valve train types, OHV will never have a relative advantage over the other valve types?
I think the familiarity bonus in the Kee Engine Lite Campaign addressed this to some degree. I think it was based on how many vehicles your company had built with each specific part.


It has the advantage of

  • less weight
  • less expensive (even when 10+ is still cheaper than 10+ DOHC)
  • in U4 is significantly smaller engine
  • Familiarity (50 years building OHV engines will make your engineers design them quickly)

if i remember correclty :stuck_out_tongue:
And chances are, we who use them are not for perfomance but rather role playing and company lore, cuz when we want performance we go straight to DOHC…


Check this vedio to to learn about OHV performance :muscle:


3.8 turbo vs 6.0 Natural aspirated vs 6.2 supercharger vs 3.8 turbo.

6.2/3.8=1.63= 63% more, so a slight volume advantage for the yankee engine.


I am going to use this article as a basis of a couple of engine builds (keeping in mind that the article is biased) and see what I get after I normalize for the displacement difference both ingame and from what the article gave.



Sillyworld got it right, in proper context everything behaves close to how it should. OHV along with DAOHC are far cheaper than any DOHC-4.

Also you OHV guys, stop. Whenever someone introduced DOHC into American racing series, that tech instantly won everything and was insta-banned thereafter. It just is not worth a discussion. OHV has its place, and it is in performance only for historical reasons, not for their actual performance.


Or, in the case of LS engines, a good combination of performance and small physical size, with the power made by loads of engineering effort, familiarity with the design, and large capacity.

I imagine that ought to be possible in the campaign.