I've played with LFSTweak extensively over the years, really getting some of my machines down to a science. There's a few of them I REALLY enjoy driving around, so I'm going to use this thread to post some of them (It's at least 6 cars w/ setups). I hope some of you enjoy them as much as I do!

My first one is kind of a recent project, someone asked:

Quote from squidhead :

If anyone would make a good xrt setup around 900 bhp, RWD preferably N/A that would be controllable (and wouldnt have wheels stickig too much out of the arches) - I'd be very happy

I wasn't able to reach 900 horsepower unfortunately, without using a number greater than 1. What I did come up with, however, is the most powerful car you can make using LFSTweak without turbines, which was 870 horsepower. I figured it was close enough. The result? Well, see for yourself, and thank you very much for the idea that got this car underway! I call this one "Project Naturally Aspirated".

P.S. Criticism is very welcome, but please be constructive. Don't just say this car sucks, but telling me where it could be improved (and perhaps even how) is very appreciated!

Why didn't you want to use a number above 1? I don't get it.

Quote from hinirags :

Why didn't you want to use a number above 1? I don't get it.

Primarily because what that number is actually doing is altering Volumetric Efficiency. A number greater than 1 would no longer be Naturally Aspirated, in a technical manner of speaking.

The second reason is that LFS has nothing to take into account component/flywheel/drivetrain weight etc., and when you increase Volumetric Efficiency past 1 it begins to rev ridiculously fast. The only way I've fixed this in the past is created more room to rev by increasing the rear gear and geared the individual gears "wide". Thus peak torque was realised at 12,800rpm, and you would shift at something like 16k.

I also can't increase the redline anymore, so I had a limited amount of room to work in. This is why I geared it the way I did, to keep below 6,000rpm.

Quote from BloodRoses :

Primarily because what that number is actually doing is altering Volumetric Efficiency. A number greater than 1 would no longer be Naturally Aspirated, in a technical manner of speaking.

Thanks for the explanation, i didn't know that!!

Quote from BloodRoses :

Primarily because what that number is actually doing is altering Volumetric Efficiency.

That makes a kind of sense, 83% and 85% seem typical values for VE in a road car. How would you explain 71% on the XRT then? VE before forced induction is added? Any ideas on any of the other engine parameters?

Quote from BloodRoses :

The second reason is that LFS has nothing to take into account component/flywheel/drivetrain weight etc.

actually it does
some versions of tweak had a time2rev parameter that somewhat changed the flywheels weight (or actually its moment of inertia since iirc the parameter had no effect on the cars weight)

with very high values and extremely powerful engines you could flip the entire car with the countermoment from accelerating the flywheel

Quote from Bob Smith :

VE before forced induction is added?

well that would make sense
if im not mistaken low compression will lead to worse volumetric efficiency
considering that lfs actually does model the turbos using a lower ve would be the only way to get a proper and realistic result

I think your setup is set too stiff and too low and therefore is a bit jumpy. I would make the suspension definitely softer, somewhere around 170 rear, 150 front and use a higher travel.
Why did you use a locked diff? This feature spins me everytime I release the throttle
I will try to modify your setup and post it here later if you´re interested.

It´s a pitty the present Tweak doesn´t have the "flywheel weight" as it was an essential value to play with so as the "powerband width" and "redline" when modeling some real cars.
Judging from the lowered value of the GTT I was firstly thinking of the "General HP" value as a Compression Ratio changer but the VE seem realistic. But I remember modeling a few BMW M3´s and Ferrari´s where I had to exceed the value of 1 as these highly tuned engines have some superior efficiency.

Going off on a tangent here, but what would a value of 0.143 likely repesent if it affects engine torque? Seems a little too high to be a compression ratio, too low to be thermal efficiency.

IIRC, there was this value for "General HP" in the old Mekanic..
If it´s not powerband, what other value could be needed for adjusing torque..

Have you done some testing, how does it affect the torque in comparism with how does it affect the power (if either)?

Quote from wak :

IIRC, there was this value for "General HP" in the old Mekanic..

Yes, that is the value I am referring to.

Quote from wak :

If it´s not powerband, what other value could be needed for adjusing torque..

Have you done some testing, how does it affect the torque in comparism with how does it affect the power (if either)?

Doubling the figure approximately doubles the peak torque and power values, peak torque rpm increases very marginally, peak power rpm increases a little more but not much either.

You guys answered your own questions regarding VE in relation to compression and forced induction.

Quote from wak :

I think your setup is set too stiff and too low and therefore is a bit jumpy.

I've heard this before, from more than just you! I do tend to run *very* stiff, but you're probably right. I'll evaluate the driveability, but part of that reason was trying to hold that 12,000cc Godzilla of a thing up.

Quote from wak :

Why did you use a locked diff?

I use a locked diff in drag racing, this was a fragment left over from then. I guess I should set it up a little better, it would indeed help at least a little in grabbing all that torque. If you also notice, I still left in the "Boost" value at 3psi, to help me test gearing at top speed.

Quote from wak :

It´s a pitty the present Tweak doesn´t have the "flywheel weight" as it was an essential value to play with so as the "powerband width" and "redline" when modeling some real cars.

Yeah, I really liked running high flywheel numbers, kind of like how most cars feel when they're stock. It (can) have a slight affect on the motors ability to rev, but it loses revs more slowly and makes the motor easier to match revs with. Clutch work in general is just 'nicer' with it that way.

Quote from wak :

I remember modeling a few BMW M3´s and Ferrari´s where I had to exceed the value of 1 as these highly tuned engines have some superior efficiency.

This, in fact, further proves how close to realistic the LFS engine physics actually are. The M3 and Ferrari's (in general) create positive pressure with the induction manifold. The end result is a forced induction like effect, without the use of a mechanical turbine. The Honda S2000 also does this, among many others.

Quote from Bob Smith :

Going off on a tangent here, but what would a value of 0.143 likely repesent if it affects engine torque? Seems a little too high to be a compression ratio, too low to be thermal efficiency.

It might be some kind of "fuel energy" (143,000 BTU per Gallon?) value, as I know when you switch to the "Race" car type, that's the primary number it changes to alter the engine dynamics. I would assume that switching to a "race" configuration would also make the fuel type change to 116 octane, no?

Quote from BloodRoses :

This, in fact, further proves how close to realistic the LFS engine physics actually are. The M3 and Ferrari's (in general) create positive pressure with the induction manifold. The end result is a forced induction like effect, without the use of a mechanical turbine. The Honda S2000 also does this, among many others.

Interesting.

Quote from BloodRoses :

It might be some kind of "fuel energy" (143,000 BTU per Gallon?) value, as I know when you switch to the "Race" car type, that's the primary number it changes to alter the engine dynamics. I would assume that switching to a "race" configuration would also make the fuel type change to 116 octane, no?

I didn't think to check the other cartypes. 0.143 for road cars, 0.19 for race cars, 0.1 and 0.16 also used on karts. The range of values seems too large for fuel?

Quote from BloodRoses :

This, in fact, further proves how close to realistic the LFS engine physics actually are. The M3 and Ferrari's (in general) create positive pressure with the induction manifold. The end result is a forced induction like effect, without the use of a mechanical turbine. The Honda S2000 also does this, among many others.

Yes, this is actually very nice, how they use the pressure from valves movement and reach this wonderfull effect in the manifold.

The longer I was experimenting with the Tweak the more I loved the realism of LFS engine

Quote from Bob Smith :

I didn't think to check the other cartypes. 0.143 for road cars, 0.19 for race cars, 0.1 and 0.16 also used on karts. The range of values seems too large for fuel?

And you do think it is something else than simply general power value..? You probably know, but I have to ask.

Quote from wak :

And you do think it is something else than simply general power value..? You probably know, but I have to ask.

I always thought the values were rather random but seeing as one had a "real life counterpart", so to speak, I thought I'd ask some more knowledgeable people what they thought.