Open Source Astra D400

The Result of a little experiment to see if I could make the Top Gear Vauxhall Astra into something worth using in D class league. Few Disclaimers, first off it’s not as fast as 97 civic or a Scirocco or a clio 93 in similarly skilled hands. It’s just not, sorry! 2nd it is RWD so those with fists of ham may find it a bit tricky though to me it’s nicely balanced. However if you want to run something a bit different in D class lobbies then what it is is a nice handling car that you don’t see every race. Speed wise i’m currently 500th in Europe on Sonoma short, 1166 on Laguna Seca (top 1%) 1048th (top 3%) on Alps festival 890th Brands Hatch and 787th on Catalunya. So it’ll run top 1-3% on the more handling biased tracks.

BUILD
Race exhaust
Race intake
Race exhaust
Race Valves
Race Engine Block
Race Pistons
Street Intercooler
Race brakes
Race springs
Race ARBs
Sport weight reduction
Rwd conversion
Aspiration Conversion Turbo
Race Chassis (roll cage!)
Race driveline
Race diff
Street Tyre compound
Team dynamics Pro race wheels (or equivalent) 235/35 R19 all round.
Forza aero F/R

TUNE
Tyres 28/28
Final Drive 4.57
Camber -0.8/-0.8
Toe .01/-.01
Caster 6.2
ARBs F 17.24 R 14.06
Springs F 509.4 R 472.3
Ride height F 4.8 R 4.8
Rebound F 9.3 R 9.2
Bump F 4.1/4.1
Aero F73 R140
Brakes F50% Pressure 125% or to preference
Diff. A 58%, D 32%

Handling notes: Balanced as is with the ability to tighten the line by going on the throttle in slower corners, half throttle can lead to understeer instead so be brave! Probably won’t respond well to TCS /STM as it’s car that steers from both ends! Good for mid length handling tracks without a lot of straight. If there are long straights then not a good track for this car but not dog slow in a straight line for a handling car. I use no assists, manual with clutch and sim steering.

Also I recommend BlueTomato90s Paint (red bull ring) as it looks good on it.

Have fun let me know what you think.

I’ll try it, only manual not with clutch as I’m not there yet, will let you know my thoughts in a couple of days, I can usually post top 1% in the right car in e and d. I’ve not seen the Astra much in lobbies and am looking to try something different.

Had a little time to give it a try on Sonoma it’s a nice build and really easy to drive, did 1.30.365 477 Europe in 5 laps, did a little tweaking for a little less mid corner turn in and made a 1.30.344 471 Europe in five laps again. I reckon with a bit more tweaking and time this will do under 1.30 comfortably. Unfortunately I already have 1.28.420 , 271 world on Sonoma short
which I did earlier today so I can’t offer you a replay. Am away til Thursday so will give a another go and on the other tracks soon. Add me Sticky Fiddler and I’ll try on other tracks I’ve not done so u can see replays if u want.

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Out of Interest: what’s the weght and weight distribution of the build?

Sorry about the delay been at work.

Thanks for taking the time, I figured people may wish to tune the point out of the front a bit, I like it but it’s a little unstable occasionally. Out of interest how did you alter it? I.e. roll bars, spring rates, aero or all 3?

52% front

And the weight?

3176lbs somehow I missed that…sorry

Out of interest, try following settings:

Tires: 28.0/28.0
Springs: 723.4/457.3
Camber: -0.7/-0.4
Toe: 0.0/0.0
Caster: 5.0
ARBs: 21.5/20
Rebound: 7.7/7.4
Bump: 4.7/4.5
Brakes: 48%@121%
Diff: 70%/35%

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Just did 10 laps in yours and 10 laps in mine. I bettered my original time with your version at a 1:30:276 putting me 466 in Europe. The weight transfer is better controlled than in my version so it’s a little better in the left/right section not sure on the brakes but it can’t float over kerbs.

However put in 10 laps in mine after getting my eye in and I’m now sitting on a 1:29:734 on a slightly scruffy lap so 349 in Europe. As predicted by sticky well into the 29s.

You use a calculator for yours? I just find the stiffness of the front very odd.

Yep I use a calculator, but if it feels to stiff on the front I probably used the wrong “car model”.

I will look into it once I have access to my xbox.

Sorry for bothering…

Didn’t mean any offence and your input is appreciated.

I’m also using a tuning calculator for the basic set up before tweaking so I’m wondering which one as most of the ones I’ve used seem to use an algorithm based on weight distribution and kerb weight to get the spring rates which you can then tweak the balance forward and back on to get it right. It would appear yours works a little differently as the rear spring rates are nearly the same but the fronts are about 60% more. It’s a nice tune part of the my pace will be learning the track over the previous 10 laps and the fact I spent most of last night playing D class lobbies so I’m in the zone handling wise.

I suspect if I came to both cold yours may be at least as fast as it has a bit more precision although there is a trade off over kerbs. Will say I didn’t notice it under steering much around Sonoma I’ll try back to back on some other tracks.

Edit: Been out on Brands Hatch, Alpine Ring in both versions and set some new fastest times. My impressions, Fifty Inch tune has a more precise feel, copes better with direction changes on flat ground, does not pitch and roll as much. Possibly a little more stable at the rear on flat ground. However situation reverses if braking and downshifting on uneven surfaces or turning on or hitting kerbs where it is skittish.

Weak points of my tune…body control you feel the the weight moving around and getting it wrong will lead to the wall.

Somewhere between the 2 is probably the sweet spot, stiff enough not to wallow, soft enough to kerb hop…

I softened the front rebound, not a lot but it stops most of the mid corner turn in

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The stiffness of the front will affect long cornering and make it under steer i would think, but I can’t get on to try it at the moment

I just tried my settings and please ignore them, they are really too stiff, This is obviously a completely different kind of RWD car that I have no base tune yet for my calculator.

I tried your settings and found them quite good. Only things I noticed was a bit oversteer on turn in (or should I say too direct without enough resistance) and mid turn understeer.

Here are the quick changes I did to your settings and I like it better afterwards:

  • rear rebound 9.0
  • rear bump 3.9
  • diff: 70/35
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The rule of thumb I always worked to for spring rates is they should be roughly similar to the weight distribution initially. You would then tune them to favour front or rear depending on drive type, eg the Astra is set 55% 45% the 3% additional at the front helps keep the rear planted. If you’re using a tuning calculator the one I have is very old and is missing a lot of the new cars (including this Astra!). Occasionally it spits out nonsense so it helps if you can sense check it.

I shall give those settings a go when I’m next on the Xbox, probably Saturday morning. If I’m honest I tend to fine tune the balance via ARBs rather than shock absorbers so will be interesting, may have to start experimenting a little.

I’ve just done my own quick build and tune for the Astra, made a 1.29.466 in 5 laps again on Sonoma which would be 304 in Europe . It has a completely different feel to yours ( much looser, rides the curbs better) not an easy car to drive though, had to take liberties with the curbs and came out of hairpin a car length behind but it has more grunt and just made pass on your ghost on final straight. Not sure it would make a very nice comfortable lobby car though but does sound the part. I have set a time on road America which was not a track I have done much on in this class so that you could download the tune easily. It is 394 in Europe out of 61000 ish and the fastest Astra in the world 103 in division behind the 97 civics at 2.40.307 but that was in 3 laps. If you try it remember it has stock brakes and is a little loose. If your interested in the build let me know and I will post

By all means, I’ll give it a go at weekend if I get the chance.

I love D class and have yet to touch this car. I’ll try it out.

Only thing I see may be an issue is the turbo, intercooler, and rwd swap. These arent upgrades I would use if grip/handling is the goal.

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It’s not an out and out handling car as such but yes you’re probably looking at the list of engine mods thinking it’ll have at least 250bhp + it actually has 210bhp because the stock engine is pathetic. So despite it all it’s only reasonable in a straight line. The intercooler is a null value mod it adds 3bhp but adds weight so you can remove it but will still be D400, so either way.

Also converting hatches to rwd I agree in most circumstances, rubbish due to short wheel base. But I did try a few different both front and rear drive builds and this one for me was the sweet spot. However if there’s a more efficient combination then every day is a school day. RWD does at least mean you can do full drag starts, pin the throttle and it’ll drop into the power band when the lights go green and leave all the FWDs looking a bit daft.

I agree, his tune had rwd so i just left it, have driven the tune a bit more and i really like it now, will try it in lobbies later. My tune however is not very good at all and rubbish on almost every track i’ve tried it on except road america but it did only take 5 minutes. I do think this car has potential to be pretty good though

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