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12-05-2016, 04:54 PM | #1 |
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Drives: 2008 BMW 135i (E88 N54 6AT)
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Location: Sunshine Coast QLD Australia
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How to manage straight-line wheelspin for everyday driving
Sorry to ask, I'm sure this has been covered before but I couldn't find it with a search; and most could be worked out by experimentation with a good GPS logger - but I don't have one, and with no nearby tracks, it's a bit of a risk of licence
My previous cars were all AWD (Subaru WRX & X5 4.8is) and I've got years of experience driving enthusiastically, but always AWD. I'm now loving my FBO E88 N54 6AT 135i, but am finding I'm very much a beginner when it comes to translating high power into forward thrust with a RWD. I've changed FUA to 56 on my JB4, so I've been do some testing/logging with 0-60 & 0-100(kph) times with wheel speed logged - but that's pretty useless when your wheels are spinning. (According to my last log I did 0-90kph in 2.9 seconds with a second gear launch, but I'm pretty sure this is fiction and a GPS log would've been measuring much less than that). I generally drive with DTC / DSC entirely off, since I find DTC over-zealous with its power cut when I exceed the limit; and I do enjoy a bit of drift occasionally out of a corner - but I was after some pointers for how other spirited drivers manage first and second for best acceleration & daily use. options I see are (for a straight-line launch): 1) Turn DTC back on and let it do it's job 2) WOT until first sign of wheelspin, then learn to back off the throttle to regain traction and still hold in-gear until redline then change up. 3) WOT until first sign of wheelspin, then short-shift to the next gear retaining WOT. 4) reduce boost target in first to about 6psi, and second to about 10psi then WOT to redline in each. Thanks! |
12-05-2016, 05:32 PM | #3 |
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Drives: 2008 BMW 135i (E88 N54 6AT)
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The ones that came with the car (second hand car) - they're not runflats, and they're supposed to be performance tires - but when they wear out they'll be replaced by Michelin Pilot Super Sports. I'm hoping that'll make a big difference.
To answer your question, (FYI, I'm in Australia, so it's summer) the tires are Ohtsu fp7000 225/40/R18's on the front and Ohtsu FP8000 255/35/R18's on the back. |
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12-05-2016, 05:51 PM | #4 |
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Calibrate your right foot.
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12-05-2016, 10:16 PM | #5 |
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doing a quick search your current tires are all seasons, with a wear rating of 450. the Michelin's you quoted have a tread rating of about 300 a ton more stickier. Full bolt ons you will need sticky tires to help the spin. Might also wanna throw a wider tire back there 255 maybe 265.
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12-06-2016, 12:16 AM | #6 |
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As said, wider tires with better traction rating will always help. And to go off your points:
1) Thats always the safest but will cut power as you mentioned. 2) Good but unless you actually have power all the way to redline, I'd shift at your peak power point. Our cars down make power all the way to redline. 3) I wouldn't shift to another gear because that could lead to the result of spinning out and crashing. Get better tires and then maybe this could be a viable option. Yes, you have an auto but shifting is shifting and causes the tires and everything to become unbalanced. 4) 6psi is good for 1st and 2nd on out I'd set it higher but maybe up to 15 psi. Starting in 2nd has always been the acceptable means to launch since first is touchy and short. The main thing is teaching yourself to modulate the throttle and knowing how much to let off and when to get back into it. AWD vehicles give you the sense of invincibility but they can still be relentless as much as FWD or RWD. |
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12-25-2016, 11:42 PM | #7 |
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135i with JB4 & DCI running Kumho 265/35/18 tyres on factory wheels.
After a short burnout I launch in 1st gear and have recorded several 1.84 60' times without any wheel spin. |
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12-30-2016, 09:46 AM | #8 |
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Not necessarily an improvement for straight line performance. Wider does not equal larger contact patch, it just changes the shape of that patch, making it wider and shorter - shorter in the direction that matters most.
I'm not advocating narrow tires, and readily acknowledge that this is a complicated subject. Just wanted to mention that wider isn't necessarily better. |
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MightyMouseTech4334.50 |
12-30-2016, 10:40 PM | #9 | |
12.92 @ 173.0km/h - 1.84 60'
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Whilst correct. A 135i doesn't weigh a lot and with low profile tyres the tyres don't distort much and you will still have a similar length contact patch irrespective of width. |
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01-14-2017, 12:20 PM | #10 |
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I have no experience with automatic BMWs so i can't speak to the characteristics of the throttle in your car, but in 6MT, its all about managing that right foot. WOT is not always the answer. Sometimes even 80-90% TPP (throttle pedal position) makes all the difference. If good times on a track are what you're looking for, its very important to maintain open throttle. Less chance of you lifting to correct the wheel spin and lose all that boost you built.
IDK if that makes any sense. Im so far from a professional in these matters that i shouldn't even be allowed on this sub-forum. |
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01-16-2017, 02:10 PM | #12 | |
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I can actually put down more power with my 205 winter tires than I can with my 265 MPSS or 245 Michelin A/S3. |
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01-18-2017, 10:46 AM | #13 |
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01-18-2017, 11:56 AM | #14 | |
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Does not matter the size of the tire, the contact patch size will be the same, as long as tire pressure is the same. Skinnier tires will have a long, narrow contact patch better for acceleration, a wider tire will basically turn that patch sideways, better for cornering, worse for accel. |
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01-18-2017, 01:24 PM | #15 | |
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01-18-2017, 01:31 PM | #16 |
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With my winters, I can go full throttle in first, even on damp pavement without wheel spin. Seriously, the car just squats and launches like a scaled cat. Can't do that with the MPSS, even in the dry, can't use WOT reliably till 2nd.
Last edited by MightyMouseTech; 01-18-2017 at 01:40 PM.. |
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01-18-2017, 05:58 PM | #17 |
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Major noob question here. Answer is simple, turn DSC fully off by holding the button and then use hundreds of hours of experience to modulate the throttle to control the car to the position and attitude you want it to assume.
THERE IS NO SUBSTITUTE FOR EXPERIENCE / SKILL. |
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01-19-2017, 06:55 AM | #18 | |
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Our 135i is my work car. Our weekend cruiser is an Australian made car that has a 590 horsepower engine with a big converter and 4.1 diff gears. If provoked it will drop back to second gear at 70km/h and paint the road. If driven sensibly it is a very, very quick street car. This car has run 11.08 in the quarter on drag radials and 11.53 on 275/30/19 Kumho street tyres, however it has to be "driven" on street tyres |
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01-20-2017, 12:08 PM | #19 | |
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I think you're confusing extra grip provided by EXTREMELY soft winter tire compounds with wide tires and compounds that are extremely hard at lower temps... My RS3's dropped off noticeably in grip once the temp dropped below 65f. They went from sticky 200tw to 400-600tw rated (I could spin tires in 3rd gear just by mashing the gas). Temperature plays a huge role in how well a tire reacts, chemically, to the asphalt. You can't accelerate without grip and narrow tire = less contact patch = less grip. My winter tires grip like crazy too (205/50/17), but it is because the sidewalls and tire compound are EXTREMELY SOFT. Acceleration is better because I am using a tire compound suited to the weather, not because I am running a narrower tire. The trade-off with wide sticky tires is weight. A narrow tire does have less rotational mass... More power makes it to the ground and acceleration can benefit. This is why you see drag cars run skinny little tires up front. It's a waste of energy putting big front tires on a car if all you care about is acceleration and you are putting power to the ground via RWD and big rear tires. OP wants to know how to manage wheel spin... Modulate your foot better. Launch at a lower rpm. Get some wider tires out back with some nice sticky rubber. That's all you can do. A mechanical diff can help, but that's more of a handicap of the underlying issue [traction]. Last edited by bNks334; 01-20-2017 at 12:19 PM.. |
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01-20-2017, 12:25 PM | #20 | |
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You can actually fairly accurately figure out the weight of a vehicle by using just the size of the contact patches and the tire pressure. We actually did this in first year Engineering. |
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01-20-2017, 12:56 PM | #21 | |
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You are also ignoring the possibility of moving to a wider wheel... Wider wheel + wider tire = greater contact patch, does it not? Last edited by bNks334; 01-20-2017 at 01:02 PM.. |
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01-20-2017, 01:03 PM | #22 |
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