A Class US RWD grip tester needed

[Spiny Anteater]

I agree with you Pete about 1st gear - I just couldn't get traction off the line so I also extended it. Thing is that kev left me for dead every single race so it looks like he's better at coping with wheelspin off the line than me. It may be that for Kev the shorter 1st gear isn't an issue. I'd have liked to have got around to changing it earlier in the night but I kept trying something else instead - by the time I got around to setting first gear it was in the "all settings change" for the last race at Motegi so it got swamped a but by all my other errors

[sk15kev]

Hence the question about short shifting then?

I only use about 20 to 30% throttle off the line.  I have poor throttle control, which probably explains why I lived with the understeer.  I suppose I see it as try not to let them start spinning so creep it off the line and feed it in.

Would like to give your settings a go.  I might stretch 3rd gear a bit, as on a very few occasions I hit the limiter around Laguna when I don't really want to change up.

[Spiny Anteater]

Well, I sent it across about 10 minutes ago, so now's your chance

[sk15kev]

Thanks Spiny took a few laps to get used to, but I think I got there.  Put down after 10 laps a best time of 57.028 on Mugello Short, then ran my adjusted build for 10 laps and had a best of 57.011.  Basically nothing in it but two very different cars.

Loaded up the old tune that was gifted out and put down a 56.8 on lap 2.  Figure that one out!  Also ran a 72.6 on Road Atlanta beofre my brain blew up.
I played around for hours with different tweaks and can better it slighly as long as I leave the toe alone.  I know it probably goes against logic, but it helps straighten the car up and accelerate out of the corner.  I created a new local profile on my xbox to get new ghosts and ran the two of them together at SilGP (my favourite track).  The one with the funny toes switched direction a lot better, i.e. in a series of left/rights and also got out of the corner straighter. 

I think this one may come down to driving style between you and me Spiny.  Will send you the car back when I make some improvements and see how you get on with my tweeks on Mugs.

[fndrbndr]

Got the car, but didn't have time to run yesterday.  I'm guessing Road Atlanta and RAS are the preferred test tracks at the moment?  I'll try to get some times for you today.

[sk15kev]

Got the car, but didn't have time to run yesterday.  I'm guessing Road Atlanta and RAS are the preferred test tracks at the moment?  I'll try to get some times for you today.

Thanks,  will be interested to see how you find the handling.

[fndrbndr]

Loose and understeer prone at the same time, I'm afraid.

[fndrbndr]

First things I noticed at RAS:

1.  Downforce seemed a bit high.  Since there's little front DF, maxing rear is going to cause a lot of understeer at speed.

2.  Differential-This is a VERY open differential for a car with this much power.  Most people dislike my settings in the 25/35 to 35/45 range. 

3.  Toe-I suspect that the negative front toe leads to some understeer.  I found it difficult to get the car to turn in.

I meant to write down my times, but failed to do so (was in tuning mode).  I did, however, save your setup and what I was working on.  It's tough to get the car not to break loose on the uphill right hander.  I suspect I'm losing a lot of time there.

[sk15kev]

Thanks for the feedback. I find it great that you and Spiny both want the back to break loose, where as I am trying hard to avoid it.

Latest version has rear aero down by 20 and changes to the diff.

I suspect you would prefer Spiny's take on the tune.

[fndrbndr]

I don't want the back to break loose.  It just seems unavoidable at some points.  Spiny tends to use more throttle oversteer than I do, IIRC.  I'd ideally want the car to stay planted on that uphill right hander.  I'm almost certain that I'm losing speed there. I'm wondering if a diff that open, combined with about 450 hp, is essentially forcing the inside wheel to spin.  That said, the car is fairly predictable when it breaks loose at that speed.  My guess is that this build is a better racer than hotlapper.

[Spiny Anteater]

I don't want the back to break loose.  It just seems unavoidable at some points.  Spiny tends to use more throttle oversteer than I do, IIRC.  I'd ideally want the car to stay planted on that uphill right hander.  I'm almost certain that I'm losing speed there. I'm wondering if a diff that open, combined with about 450 hp, is essentially forcing the inside wheel to spin.  That said, the car is fairly predictable when it breaks loose at that speed.  My guess is that this build is a better racer than hotlapper.

A couple of points arise from this.

First it's true that I tend to the more oversteery end of the spectrum, but the last thing I want is for the car to "break" loose - that and immense understeer are the two things most likely to make me lose confidence, and hence speed, in a car. I like my RWD cars to break traction with the rear wheels first rather than the fronts, but I prefer that loss of traction to be a gradual process rather than a sudden break. In a stock car, one of the best examples of that would be the Shelby Cobra. Sure many people hate it because it has so much power, but the main reason I love it so much is that it tells you when it#s losing traction allowing you to maximise the throttle steering. Anyone who's seen me race that will know that through a corner I'm usually pointing about 10-15 degrees inside the line I'm taking. That's in a car with stock suspension so there's no fiddling around to get that - it's just a car which is naturally suited to me.

The second point is that I know exactly what fndr means about the diff. I think I mentioned it in our test session, but at 10% accel diff lock I'm sure I could feel the inside rear wheel spinning up, and that was affecting traction.

The fastest car will be one which doesn't have that rear wheel spinning up. However, the most important thing to remember is that the fastest car for you is the car which suits you

[BarbecuePete]

However, the most important thing to remember is that the fastest car for you is the car which suits you

This is very true, I had chance to get a bit more time with the car last night, Kev's tune I was hitting around 57.xx on a good lap but the understeer had me heading into the tyre wall on the last corner of RAS most of the time...

I think Kev may have the right idea on the launch, I really struggled to find a good launch gear, this thing just loves to smoke its tyres off the line! Eventually though I did find a set of gears that allowed a decent get away with a bit of throttle control and a short shift to 2nd... I also changed the tyre pressures, diff setting and the toe.

After just 3 laps I'd hit a 55.6xx, few notes for a lap.
Apex speed in the first corner 90-100mph,   
Uphill sweep, lift for turn in but full throttle all the way through.
4th gear approx 150mph at braking zone for chicane.
Full throttle through last corner

I'll get the changes to the tune written down and post them up later on and see what you think of them, toe settings may seem odd but really seemed to work well for me and 4th gear doesn't sound like its doing much but watch the numbers fly up on the speedo...

[BarbecuePete]

Here's the changes to kevs original tune, I've also got a second stage which changes a few more things and I felt I was able to carry a bit more speed through corners. see what you think.

Tyres : 28/28 (I had them set to this at the time but 28/29 is better IMO)
FD : 2.75
1st : 2.55 / 1.75 / 1.30 / 1.02 4th (might not work to well with auto shift)
Toe : 0.1 / 0.2 (yes that is meant to be positive  )
Diff : 20/40

Stage 2

Tyres : 28/29
FD : 2.75
1st : 2.55 / 1.70 / 1.28 / 1.02 4th
Toe : 0.0 / 0.2
Rebound : 8.0 / 9.0
Bump : 4.4 / 3.4
Ride : 5.8 / 5.8
Diff : 20/40

[sk15kev]

Thanks Pete,

Tried it out on Sebring Short as that's where I am currently testing at the moment.  I really liked you changes.  Still really stable through the corners, but without such pronounced understeer.  I also liked your gears and have adopted them if that's okay with you.

I am reworking the tune at the moment and have also tuned out the us, but now have a touch too much snap. 

As for the tyre pressure, I am have the 28&29 dilema on both the fronts and the rears.  Currently I am still 28/28.

If you want me to send you an update when done gift the car back and I'll update it.  Currently matching times with your version, but not as consistently.

I have also built up a Stingray on race tires, and can consistently drop below the 72's on Sebring Short.  Very promising.  Although it's only drawback is it can't get past 152mph.

[Spiny Anteater]

I gave the new tune you sent across a try at RAS last night Kev. As it was following on from my running a grip-built B Class Chevelle it probably felt grippier than it actually is, but I couldn't see any major daemons with it, other than a tendancy to wander under heavy braking which I'd put down to the 46% brake bias. That might be something you want to live with, I don;t think it's a major issue but could be corrected with a switch to 47%. One thing which really surprised me was how well it rides kerbs considering the minimum ride height at the rear - I guess this shows this is an area where the Forza model could do with a bit of tweaking for the 3rd iteration.

Going back to that B Class Chevelle for a second, it's running the stock engine and I was really surprised at how close the stats were for that and your Camaro (although the Chevelle is over 3000lbs and has the skinniest tyres possible to allow slicks within PI).

Chevelle:
450 bhp @ 5600rpm
500 lb-ft @ ???rpm
Top Speed Stat: 5.3

Camaro:
447 bhp @5600 rpm
494 lb-ft @ rpm (OK, I've forgotten how much, but it's the same figure as the Chevelle - might be 3800?)
Top Speed Stat: 5.3

Although those figures are the same, it translates into a 3 seconds gap around RAS. 59.000s for the Chevelle, 55.9s for the Camaro. That sounds about right as I'd usually expect about 3 seconds difference around this track between classes given similar cars.