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gave it a run, seemed fine on both afr's and boost
also, the 75w90ns has quieted down the front diff a touch. it still makes the groaning/deep knocking noise, but no more of the violent popping, probably from what jon said with the stiction.. it does feel very bind-y with no power and low speed parking lot turns, like it wants to stop the car. My driveway requires a sharp left in, and slightly inclined, and I've stalled it twice from the car not wanting to move forward, so I still plan to remove some preload, but the noise and drivability is fine for now. will change it later.
i was at an autox last weekend and the conditions weren't ideal (40-50 deg, with 20-25mph wind gusts) - so I had zero ability to keep any heat in the tires. Usually that's when the Evo handles the best, but man it was extremely loose on power - the site I ran on is concrete but it's pretty janky concrete. Regardless, pretty surprising how loose the car behaved, likely due to conditions and the rear diff. I got up the car to set the sway bar to soft and it was already on soft so...
This is a clip of one of the runs where i got very late on the slaloms and then gunned it to the finish, but still wouldn't have expected it to power-oversteer like this
oh and this video shows exactly what a good rear diff does. when you lift the inside rear wheel and the diff stays locked while you go to WOT you generate a very large oversteer yaw moment due to the thrust coming from the outside rear tire only (ignoring for a moment what the front is doing). If the diff doesn't lock it spins the inside rear tire and you get no forward thrust but also no oversteer yaw moment. IMO the solution isn't to change setup but to change the driving inputs.
I agree with this. balance shouldn't dramatically change from cold tires to warm tires. What you describe is a car that is so pushy it is roasting the front tires which results in understeer and then have balanced the car in that condition by not running enough rear camber (or toe-in). when the fronts are cold you get more grip out of them and then roll over the rear tires a lot so it feels extra loose when cold. increasing rear roll stiffness will put more heat into the rears and less heat into the fronts but if you don't fix the now tremendous oversteer with more rear camber or toe-in you'll think that your increased roll stiffness is bad. Watch your tire pressure increases run by run, the fronts and rears should be going up by roughly the same amount each run. if you are getting 3-4psi increase on the fronts and 1psi increase of the rears after first run you need more rear roll stiffness.
i thinkt he 3-4psi front and 1psi rear increase is roughly what i see. i can't run the crazy autox rates on the track, that's a dangerous combo. on 8/11 the car is already extremely loose on the warm up lap. i'll look into toe arms to run more camber and toe-in for the rear - currently at about -2.5 in the rear with 3/32nds toe-in.. the car is also street-driven, much more than what i have for toe-in doesn't seem like a good idea
Pretty sure we've said this enough times but NEVER USE YOUR WARM UP LAP AS YOUR SETUP BASIS. Thats equally as bad as dialing setup on dead tires.
Ease into speed and things will come up. And as Marshal eluded to, ask the rear to do more work and it will reward you with more heat quicker.
Just in general, first lap of a ~60sec AutoX we can go from push till front starts working in 2-3 turns, to oversteer for maybe half to 3/4 of the run to finishing with the car we want. I would never make a setup change based on that first 3/4 of a run. First lap on track starts at like 5/10 creeping up as we feel the tires coming in. Mid corner you can feel lifts give yaw and throttle pulls out and how that changes with more lateral load vs tire temps. But Its still less than a lap till tires are fully working and even chopping throttle mid-corner only produces yaw and not spin unless you go like full throttle to full lift while asking for max lateral load because that shouldn't work in any well setup car.
i dont make setup changes based on cold lap, hence why it's so loose when cold. not sure how much power or tires you are on, but one lap at 5/10s will not result in operating temp tires by lap 2 on a 70 degree day for me. for an autox like last sunday when the tires are fully ice cold by the time the runs get to me, then the car can be a handful. the fast lap resulted in me getting a rerun the last run of the day when the tires were warmed up.
i'll see how this weekend goes at ncm, sunny and 50-70s from morning through afternoon
on COLD tires, it's loosey goosey. if I don't give it 7/10s on the warm up lap, it will still be loose for lap 2. it's greatly dependent on ambient temps. if it's 40s out, i need 2 laps warmup to really feel comfortable pushing the car. 60s-70s, still better on that 3rd lap. 80+, maybe then it'll be happier on lap 2 but haven't actually had many of those. when the tires are hot and i'm pushnig the car, i think it's fairly neutral/mild understeer. turn-in is great, post entry is a little meh, and exit is great. the longer the corner (sweeper), the worst the post-entry push is.
been meaning to look into this - what are the rear window vents some people use for? it's it just for cooling or does it help with drag somehow when the front windows are down?
been meaning to look into this - what are the rear window vents some people use for? it's it just for cooling or does it help with drag somehow when the front windows are down?
I crack my rear windows to reduce the terrible buffeting that happens with fronts only being down.
I'm doing these. Hoping to cure my low speed/ part throttle problem as well as having to be towed off course when I lose a coupling.
tHank's, @Lumpy Sticks
oh ok. so it's not for like, the back of the car not acting like a parachute when wind enters through the front windows. though j guess not a lot of wind comes into the car even when going fast
