Forza Four Tuning...

[Blooze]

Well to make a long story short, all my Forza Three stuff moved directly over to Four.

There will be a number of revelations I'm sure, but I think they are mostly going to come from the upgrade side of things.

Mostly, I need a nap right now...

Chat with y'all later...

  $

[PhantomGinn]

I was just in the process of looking that up. It does appear that the basics haven't changed. The only changes I could see are differences in the camber (since they adjusted the suspension models) and maybe the tires with the new data. The rest appears to be exactly the same. I just checked the SWR and SB changes with changing weights on a 2006 Civic Si, they remained constant at Sb=0.52, SWR=0.47. So I agree with Blooze, it should port over without any problems.

[Blooze]

Well, that didn't take long.  I haven't sorted it out yet - had to shut down and regroup.  Not that I was floored or anything, but a bunch of stuff changes as far as the FHRA goes.

Tire Compound is going to be a big player in Forza 4.  If I'm a-memberin' rightly, it was in Forza 2 as well.   I just now ran up 75 Pi points between D and C with just the Race Transmission and the Street tire compound.  I was already carrying the widest possible tires and that may have had something to do with it.  Just the tire compound increase bumped the grip by a full tenth.

So, I got some looking around to do.  It's a good thing that the parts are free...

One thing I want to check is if tire width affects the Pi value of a compound upgrade, and visa versa.  I'm needing a nap or I would have checked what the DOT and Slicks did for the Pi.  Just on the surface, it looks like  a body could run from D to A on the back of nothing more than tire upgrades...

  $   

[Tonka Crash]

I just checked the SWR and SB changes with changing weights on a 2006 Civic Si, they remained constant at Sb=0.52, SWR=0.47. So I agree with Blooze, it should port over without any problems.

I played with the Roll Cage and Weight Reduction on the '71 Skyline and noticed the WB did change depending on settings by 2%, going from 54% to 52%.  First time I've seen it move in a Forza game.

[Blooze]

You're talking about the published Weight Bias, right?   Or are you talking about the Spring Bias?

Back in Fm3 a number of things could change the Weight Bias.  Exhaust systems was another of them.  But it was just a fancier bit to the ruse.  The weight was still distributed by the SWR.

$

[Tonka Crash]

I was looking at the published number.  I hadn't gone into looking at before/after numbers on the springs themselves.

A couple other things I've noticed.  Aftermarket rims do not always decrease weight depending like I'm used to.  I have the '80s Celica that the heavier rims increased weight. Maybe it always did and I never noticed.  I had one PI to spend and was looking at rims.  There also seems like there might be a sweet spot for tire size aspect ratio.  On stock width, inceasing rim diameter increased PI to a point.  At max rims sizes it starting going back down.  Didn't it always rim diameter increases decrease PI due to weight?  It's been so long since I messed around with upgrades in FM3 I don't remember. It also bugs me it doesn't show you the installed tire size.  You have to infer what it is based on the choices to either side of it.

[Spiny Anteater]

I was looking at the published number.  I hadn't gone into looking at before/after numbers on the springs themselves.

A couple other things I've noticed.  Aftermarket rims do not always decrease weight depending like I'm used to.  I have the '80s Celica that the heavier rims increased weight. Maybe it always did and I never noticed.  It did... and you never noticed I had one PI to spend and was looking at rims.  There also seems like there might be a sweet spot for tire size aspect ratio.  On stock width, inceasing rim diameter increased PI to a point.  At max rims sizes it starting going back down.  Didn't it always rim diameter increases decrease PI due to weight?  No, on some cars, particularly the older cars, increasing the rim diameter could also increase the PI up to a point. However, it was only really noticeable on cars with high tyre walls.It's been so long since I messed around with upgrades in FM3 I don't remember. It also bugs me it doesn't show you the installed tire size.  You have to infer what it is based on the choices to either side of it.

On the installed tyre size, in FM3 you could find the size on any car by going to the car list and right triggering across the attributes - the far right two were front and rear tyre size. No idea if that's the case in FM4 as it won't arrive until next week.

[PhantomGinn]

Well, that didn't take long.  I haven't sorted it out yet - had to shut down and regroup.  Not that I was floored or anything, but a bunch of stuff changes as far as the FHRA goes.

Tire Compound is going to be a big player in Forza 4.  If I'm a-memberin' rightly, it was in Forza 2 as well.   I just now ran up 75 Pi points between D and C with just the Race Transmission and the Street tire compound.  I was already carrying the widest possible tires and that may have had something to do with it.  Just the tire compound increase bumped the grip by a full tenth.

So, I got some looking around to do.  It's a good thing that the parts are free...

One thing I want to check is if tire width affects the Pi value of a compound upgrade, and visa versa.  I'm needing a nap or I would have checked what the DOT and Slicks did for the Pi.  Just on the surface, it looks like  a body could run from D to A on the back of nothing more than tire upgrades...

  $   

Yeah, I noticed some interesting things about the tire width, especially on FWD and AWD cars. At least for stock compound, it appears that increasing the rear width doesn't increase the PI by much. Using a 2006 Civic Si, here's what I found tire wise:

Starting Stock:
Stock width, stock compound: 0.853 G's (@60 mph), C371
upgrade to street: 0.885 G's, C388
sport: 0.919 G's, C400
race: 1.004, B430

When increasing rear tire width from stock (215/45/17 to 235/40/17):
stock compound: 0.853 G's to 0.857 G's (No change in PI)
street compound: 0.885 G's to 0.890 G's (No change in PI)
sport compound: 0.919 G's to 0.924 G's (no change in PI)
Race compound: 1.004 G's (B430) to 1.009 G's (B429)

Changing the front width, on the other hand, increases the PI by 7 to 9 points (215/45/17 to 235/40/17) and a minimal increase in roadholding (0.010 G increase).

As far as the rims things go, it seems like the PI will increase as you increase the rim size up until about 19 inches. After that, it sometimes increases, sometimes decreases. I don't quite understand why.

[Tonka Crash]

Hey Blooze, feel like some light reading?

I was looking around for some tuning info and ran across a book reference available as a pdf here.  It has a chapter 4. Driveline Dynamics that provides some methodology (with equations ) on optimizing gearbox ratios to engine performance for best acceleration to a terminal speed.  It looks like it might be a way to optimize the gear spreader part of the transmission spreadsheet.

[Tonka Crash]

I've come up with a different transmission calculator.  Take a look and see what you think.  Rather than pick gear ratios and look at how the shift points would change.  This lets you set the rpm shift point and sets the gear ratios. Final Drive is set from terminal velocity and tire size.

Edited: November 3, 2011 - Deleted the attachment. It was garbage.

[Blooze]

So, when my 3:15 am brain saw the first graph, it said, "Ah-hah... VTec!"

That was the last easy thinkin' work I had.  Good job on this!  It looks like you really busted the old tucus...

So, what's your impression of what you have wrought? 

What is it like to drive a car with that gear set, and shift at those points?  It seems like time would become the big pink buggaboo in the corner.

Any problems down shifting in the upper gears?

How did you get the telemetry data?  Start - Stop in 5^th on Old Mulsanne (sp)?

I need coffee...

$

[Tonka Crash]

This is the kind of stuff I think about when I'm at work and would rather be on the Xbox. I'm still missing something. In practice the down shifts aren't dropping far enough to use all the power band. I did more reading and the power band in my plot should be defined by the max torque rpm and max HP rpm for most engines, but the ratio from gear to gear shouldn't be constant like it is now. My goal is to get a first cut at gearing tailored to the engine characteristics without having to muck around with telemetry.

The data in the spreadsheet I posted is actually from a Lotus 135 in FM2. It's what I still had in my transmission sheet.  I didn't play FM3 enough to get around to tuning much. I drove mostly stock cars as I couldn't afford much else. The credits grind was an enormous turn off to me in FM3, but now that's gone and I can get back to having fun.  After a week of playing I have more credits than I had in my first month of FM3.

I haven't got too many cars with racing transmissions yet and the one I experimented with last night was a poor choice. At least it was very odd, the Renault Megane, I think it has a turbo-diesel. At least that's the only thing I could think of to explain it's torque curve. Pretty constant torque across the rpm range.  200 @ 100-1800, 235 @ 2000, Peak of of 262 @ 3000rpm tapering to 251 @ 7000. I ran some B-Class events with a 2-speed and it did fine except for launching. How do you gear a diesel?  It seem any change to the default gearing increased it's 0-100mph benchmark.  For more weirdness try the single speed Tesla.

I tend to use the benchmark ring for telemetry just so I don't have to drive around to find a straight and I don't have to brake for the turns in the classes I'm interested in. For the megane I didn't even bother with save a replay to step through since the torque was so constant.

[Spiny Anteater]

I haven't got too many cars with racing transmissions yet and the one I experimented with last night was a poor choice. At least it was very odd, the Renault Megane, I think it has a turbo-diesel. At least that's the only thing I could think of to explain it's torque curve. Pretty constant torque across the rpm range.  200 @ 100-1800, 235 @ 2000, Peak of of 262 @ 3000rpm tapering to 251 @ 7000. I ran some B-Class events with a 2-speed and it did fine except for launching. How do you gear a diesel?  It seem any change to the default gearing increased it's 0-100mph benchmark.  For more weirdness try the single speed Tesla.

It's not a turbo-diesel. Most of the European hot hatches have a similar type of torque curve - I can only assume it's due to the turbo.

Take my real life car as an example (Focus ST, so you can also see it in game). The peak torque is 236lb-ft at only 2000rpm and stays above 200lb-ft right up to over 6000rpm. However, as peak power is about 5000rpm, I think you would have to rethink the "max torque to max-rpm" strategy or you will have some massive gaps. And I do have to admit that you can feel the gap between 5th and 6th (which is geared for economy) when you're driving.

[Blooze]

Since they did away with the step process in the telemetry program I have gone off in a more simple route myself.  Extrapolation?  I think that is what it is called.  We are given the rpm at the torque peak and the rpm at Hp peak.  It can probably be calculated, but I just binary the torque at peak Hp in.  Once I have that I just  (Peak Tq - Hp Tq) / #rpm increments.  It ain't pretty but I have found that it is pretty damned close, and I have also found that the physics engine doesn't use numbers that are too fine.  As for anything past the Hp peak, I just goof with a delta value that delivers a line aimed in the general direction of the picture in the game... i.e., flat, down slow, down steep.  Something like that.

I highlight the range of torque values where the Hp is within 10% of it's peak.  That helps make some of the decisions too...

I have found that a final drive total gearing that reaches 95% on the transmission graph is going to be just about it for a terminal velocity.

Once I have the launch characteristics set, then it's smooth 'em out in between.  What looks good numerically much of the time will feel just a tad off... an up shift that bogs just a little, specially on a hill, or and emergency down shift that locks up the wheels and grenades engine.

The profile ( the line or curve created by the 5 entry points ) that I use most with cars that are torquey sort of hooks at the end with 6th gear.  I take a little wider bite with the last gear for two reasons, 1.  It drops the gear into a little more torque, and 2. It occupies space that the other gears don't have to - I can be a little more narrow with them.

I don't know if that makes any sense to anyone...  the world of transmission tuning according to Blooze/GICheeze circa Version IV... I guess.

Looking at your derived gear set, I suspect that the pull from the shift into 6^th to TV takes quite a while, leaving one to wonder if the additional mph is worth the wait.  I bet the gap on 5 to 6 is no honey, either.

How does it run?

$

[Tonka Crash]

What I had in the transmission sheet was more appropriate for semis and earth moving equipment.  I'm still looking into a better scheme. I found a design book that discusses progressive gearing, but I`m not finding how  to best match it to engine performance.