Anyone for Alfa Romeo P3 open-source chassis tuning?

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#1

It’s an acquired taste, I know, but as a classic sports car racer I’m enjoying tuning and racing the vintage racers: the Auto Union type D, the Maserati 8CTF, the Mercedes W154, even the blower Bentley and, now that I finally had the money for it, the Alfa Romeo P3. I’ve managed to chassis-tune most of them - not great but reasonably well - but this Alfa is an unmanageable animal on the track. I’ve played my usual tricks with spring rates and ARB settings and so forth, but in a race it’s a problem even keeping the thing on the pavement. And while I can win races with it, they’re the most ragged victories I’ve ever notched. Sort of slow-motion train wrecks.

So, a question: is anyone interested in doing an open-source tuning for this beast? The limits are stock engine at 285 HP (although I’ve experimented with the race carburetor for a 10% HP bump, hoping for a bit of a speed edge, but at a cost in handling), and I’m staying faithful to the original RWD. Stock tires, but all other chassis tuning mods are expected. My test track is Astmoor Heritage Circuit, and I’m circulating at around 1:16, two or three seconds slower than, say, the Auto Union. Here’s my current setup. I usually start with Hoshi’s base tune, but for this one I started from the game’s stock settings.

Tires: 30 psi
final drive: 3.80 (circuit gearing, other gearing stock)
alignment: -1, -0.7, 0, 0, 6.0
ARB: 20.67, 9.07
Springs: 325.0, 210.4
Ride height: 3.3, 3.7
Damping: 11.5, 11.0, 5.1, 6.0
Aero: locked
Brake: locked
Differential: 40%, 30%

I’d really appreciate some help from some of you ace tuners on this beast. Any suggestions would be appreciated, and a full tune - open-source, not locked, so that I can learn from it - would be preferred. While a locked tune could be raced successfully, that’s not what I’m looking for here. I really want to learn how to improve my skills in this area.

#2

What, so we are looking at race suspension, ARBs and a race diff? No engine mods. Roll cage and the lighter gearshaft are approved chassis tuning mods, or strictly mods that enable chassis tuning options?

#3

Oh sure, all those are fine. The limitations I mentioned (stock engine, stock tires) are, for my purposes, just intended to keep the rating fairly low. Tire upgrades, for instance, seem to jack up the PI pretty fast, so I usually never even bother to look at them. I tried a small engine mod myself, just 10% as I mentioned, but right away started losing whatever handling I’d achieved with the stock 285 HP. I know that tuners like to focus on the fastest cars - the S1’s and S2’s, if not the X’s - but for me, with my old and slow reflexes, a tune that ended up in the stratosphere would not be of much use to me. I tend to run in the lower classes, trying to refine and improve my driving style without things happening so fast that I can’t keep up.

And thanks for stepping in.

2 Likes
#4

Hello!

I’m tuning such a beast right now. Would a B700 P3 with street tires be objectionable, or must it use the stock tires?

#5

The problem with tuning this car seems to stem not so much from the inability to get the correct ARB settings and so on.

The problem is: It has a 3 speed gearbox, and a relatively light frame. The tire compound doesn’t want to heat and stays cold even if we lower the pressure, and the aero is locked so we can’t induce heating that way. And then, you want to stick to the base RWD.
These factors all combine to mean that, even with the base engine, when it hits its powerband it will spin the rear wheels given half a chance if you go full throttle.

All that said, you are a way better driver than I, I can only hit a 1:18 using your tuning setup. I’ve hit a 1:16 with some adjustments, I started with the gearbox as the way its currently tuned 2nd gear is useless as it red lines around corners, but drops you into 3rd at 3000 rpm which has no power, and then 3rd redlines along the straight… so I stretched out the gearbox so 2nd gear could carry me around corners which then gave 3rd gear more power for the straights.
This of course made the car even more twitchy as I was hitting the engines powerband more often so throttle control is required to prevent the back loosing grip and stepping out.

At any rate, I see your chosen circuit has a natural B-Class Classic Racer Rival event that the car qualifies for. (Without engine (or drivetrain) mods we are only at B626 so the leaderboard of this event will have a 74PI advantage over the car we are currently tuning.)

#6

@ShellacMaster12, your B700 with street tires sounds like a good candidate! Let’s see what you’ve got. I generally tend to avoid tire upgrades because of the high PI cost, since I’m trying not to bracket out of the car’s B class. But the increased grip in the turns would help in the turns and perhaps even make the thing less twitchy on the straightaways. Plus being at the top of the bracket is excellent.

Interesting analysis, @GreenZombie76. I was hoping that better tuners than I am would weigh in on this beast. As a pretty inexperienced tuner I’ve been sort of focused on the chassis tuning, and never even noticed what the ratio spreads in the gearbox were doing. On the tires, all these vintage racers seem to suffer from the same problem - those skinny 1930-era tires just can’t absorb the HP. The men who raced those things - Nuvolari, Fangio, etc. - must have been amazing.

While I can hit those times on the track, I’m all over the place trying to do it. Wears me out just trying to stay on the pavement. Main thing, I guess, is that I’m having a hard time trying to learn how to modulate the throttle with only a half-inch of travel on the controller’s throttle trigger.

#7

@ReportedPeak2: If you don’t have one already, treat yourself to an XBox Elite Wireless Controller Series 2 this Christmas.

If you want to try my tune - the one I can get ~16s with - the things I changed significantly were
Tires: 15.9 psi
Springs: 413 lb/in
Rebound, Bump Damping: 11.5, 6.9

The pressure was chosen both to try and get some damn heat in the tyres, and to make the pressure match the mass of the car to a decent contact patch per tire.
Springs are chosen to have a bounce period of about 1.5s which should be forgiving in a low tier car, and the total damping (18.4) has a similar period over which it squashes oscillations.

the reason my front and back values are the same was I was trying the Roll Cage, because it looks nice, and it shifts the weight distribution to 50% exactly

I use my own calculator. Its a work in progress google sheet. You can make a copy of it here to use it: Forza Tuning - Google Sheets
You can toggle it to English units on the “Work” tab as well as tweak some defaults if you don;'t like my choices, otherwise the “Calculator” tab is a mobile friendly layout that lets you enter your car details at the top and then shows the results of the tune calculations, in the order FH4 wants them, scrolling down vertically.

#8

@GreenZombie76, you’re dangerous. I’ve been using an XBox Elite controller (series 1) for a couple years now, and just recently I’ve been going on and off the fence about upgrading to the series 2. I’m afraid this is probably going to push me over the edge.

I’ll try your recent suggestions shortly, but for now this is where I am. I put together @ShellacMaster12’s suggestion for a street tire upgrade, now at B700, along with your work on the transmission, and those two by themselves gave me a couple more seconds. Lowered the final drive to 3.50 now that I’m running faster, lowered 1st to work on the wheel spin and 2nd as you suggested for the turns. I’m turning 1:14’s now at Astmoor with those two adjustments, and not careening around as wildly. Let’s see what your latest does.

Thanks for the offer of your calculator.

#9

@ReportedPeak2

You picked an interesting car to tune ;). I know this tune looks a little wonky, but it does help with the skittishness of the P3. As a matter of fact, the P3 is one of the fastest B class cars; if you can learn how to use it. I’ve been able to post a lap time of 1:08:1 at Astmoor with this tune.

Parts:

-Sport Flywheel
-Race Springs and Anti-roll bars
-Race Driveline
-Race Diff
-Street Tires

Tune:

Tires - F/R 15psi

Gearing - Final 2.89
1st 1.59
2nd 1.28
3rd 1.15

Camber - Front -0.03
Rear -0

Toe - Front -0.3
Rear -1.4

Caster 6.8

Anti-roll Bars - Front 44.27
Rear 4.57

Springs - Front 524.1
Rear 174.4

Ride Height - Front 3.6in
Rear 3.6in

Rebound - Front 12.5
Rear 15.1

Bump - Front 3.9
Rear 3.2

Areo - locked

Brakes - locked

Differential - Acceleration 5%
Deceleration 2%

Give that a try and let me know what you think. It might feel a little odd at first because of the toe-in.

1 Like
#10

The suspension settings look insane. But the gearbox does what I set out to achieve but couldn’t: keeps you away from the engines power band while cornering allowing you to corner in a controlled fashion under power, important in Astmoor with its long sweeping curves.
I was hoping to achieve the same with 2nd rather than first gear as the car feels very sluggish taking off on its first lap : Which is fine if its used for Rivals rather than racing I guess.

I’m still trying to understand what your spring - and ARB - tuning is doing.
You have an oscillation period of 1.675s at the rear, but the front is tuned to a 0.978s oscillation. For your normal B class racer you are looking to tune to about 1.25 to 1.125, with your A going to 1s, and S1 and S2 dipping towards 0.8’s or even 0.7s. And you usually want to tune the rear to be ever so slightly faster than the front, as the front hits bumps first which sets up a front back rocking motion, but if the back springs are tuned slightly higher the back ‘catches up’.

Anyway, point is, your springs are tuned for a Ferrari at the front, a dune buggy at the back, I don’t know enough about roll bar theory but the ARBs seem to be tuned the opposite way around.
Whatever works I guess.

#11

@GreenZombie76

I know the suspension settings are a little different than most cars. The rear end of the P3 always feels stiff as a board with no suspension travel or grip, and the front end turns in so quickly, the rear is usually flung off the track.

I tried to give the rear more grip by softening the rear springs and bump ( a lot) so the suspension travels more and reacts better to bumps. I raised the front of the car and hardened the front springs to try to make the car “squat” even more in the rear. The toe-in is to dull the twitchyness. My car is tuned for a lot of under-steer to try to make it more controllable. The ARBs are tuned to make the rear grip more and to provide under-steer.

I guess you could say the car is set up to go through corners safely rather than quickly.

#12

I’ve been away a bit so I haven’t been able to keep up with what you guys are doing, but I’ll be back after a few days, probably. You two are way ahead of my simple notions about tuning, so I’m looking forward to driving your tunes and learning from this. 1:08 at Astmoor? Insane!

#13

@ShellacMaster12, after quite a long time I’ve finally gotten back to the Alfa P3 and I’ve been running your tune with good success. I’m running at Astmoor with my best laps in the high 1:10’s, which is about as good as I can do today with my current level of driving skill but still way better than the 1:14’s I was running before. The main thing seems to be that the car is now stable enough that you can stay on the throttle more, and longer, without going all squirrely. But if you turn 1:08’s with it you’re a way better driver than I am.

Thanks for your help.

#14

You may alternatively try these settings for the P3 at Astmoor Summer Rivals Race:

Tires: 29/29
Gearing: 2.77//3.10/1.80/1.11
Camber: -3.4/-2.3
Toe: 0/0
Caster: 5.0
ARBs: 4.70/4.70
Springs: 268.5/318.9
Ride Height: 5.3/5.7
Rebound: 16.8/17.1
Bump: 5.3/5.5
Diff: 86/0

The tune requires a bit more throttle control than ShellacMaster12s tune.