Quickest Way of Accelerating in First Gear

1. Barry123 Saxperience Hardcore! Joined: Oct 2005 Aycliffe Posts: 32205 Saxo VTS

   #1 20th July 2007, 08:04

   Ok yesterday my mate who's doing a similar research project to me came across a little gem of information you boyracers vroom vroom might find interesting.
   
   From the simulation results he's concluded that you get better acceleration in first by slipping the clutch for the rather than being fully connected. I spent a large amount of time trying to fathom out why and still not sure as to why although the simulator we use is a highly complex and pretty accurate.
   
   My guess is it is something to do with the inertia of the vehicle both sprung and unsprung masses, so body and wheel masses and that these inertia are transmitted through the transmission to the engine... opposing it movement. slipping the clutch minimises the opposing torque transfer of the (un)sprung masses, although that also means less engine torque transmitted...
   
   Im clueless
   
   
   But anyway you may know this already but came as news to me.
   
   Geek mode over.
2. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #2 20th July 2007, 08:21

   Here's a much simpler answer... Where's your power band? Around 1000 rpm? Or around 5000 rpm? So if you put the boot down with no revs, you have to climb through the revs until you get a decent amount of power. If however, you just drop the clutch at 5000 rpm, you will spin the wheels. This obviously happens because there is more power in that area. (We're suggesting the power band of course) Anwyay, if you don't allow the clutch to fully bite, you can feed it in while in the higher revs and get a quicker start.
3. Karl Saxperience Hardcore! Joined: Apr 2006 Ashford Posts: 25611 LY R26

   #3 20th July 2007, 08:32

   Won't it smell and be bad for my clutch though?
4. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #4 20th July 2007, 09:05

   Don't race then...
5. blacksax1 Frequent Poster Joined: Mar 2006 oxfordshire Posts: 812 top of the range scort lol. yeah right

   #5 20th July 2007, 09:09

   Quote:

   Originally Posted by Toad Here's a much simpler answer... Where's your power band? Around 1000 rpm? Or around 5000 rpm? So if you put the boot down with no revs, you have to climb through the revs until you get a decent amount of power. If however, you just drop the clutch at 5000 rpm, you will spin the wheels. This obviously happens because there is more power in that area. (We're suggesting the power band of course) Anwyay, if you don't allow the clutch to fully bite, you can feed it in while in the higher revs and get a quicker start.

   that was much simpler on adsayers one i was lost after the first unsprung mass. lol im gonna try it later
6. KamRacing Saxperience Addict Joined: Nov 2006 A farm shed in Aylesbury Posts: 14916 Corolla AE86 Peugeot 205 B18C (in bits)

   #6 20th July 2007, 09:21

   I don't slip the clutch I slip the wheels.
   
   The fastest way to accelerate is to get just enough wheel spin to stop the engine bogging down.
7. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #7 20th July 2007, 09:35

   I do a bit of both to be honest...
8. Karl Saxperience Hardcore! Joined: Apr 2006 Ashford Posts: 25611 LY R26

   #8 20th July 2007, 09:39

   Hmmm - out of curiosity, if i was too launch my car,
   say on a normal tarmacc'd road...
   what RPM should I ideally launch a VTS at?
   
   ++ would this be different to the RPM I would need at the pod?
9. Barry123 Saxperience Hardcore! Joined: Oct 2005 Aycliffe Posts: 32205 Saxo VTS

   #9 20th July 2007, 10:16

   Quote:

   Originally Posted by Toad Here's a much simpler answer... Where's your power band? Around 1000 rpm? Or around 5000 rpm? So if you put the boot down with no revs, you have to climb through the revs until you get a decent amount of power. If however, you just drop the clutch at 5000 rpm, you will spin the wheels. This obviously happens because there is more power in that area. (We're suggesting the power band of course) Anwyay, if you don't allow the clutch to fully bite, you can feed it in while in the higher revs and get a quicker start.

   no no toady you read me wrong... I'm geeking at uni at the moment so i'll grab the info.
10. KamRacing Saxperience Addict Joined: Nov 2006 A farm shed in Aylesbury Posts: 14916 Corolla AE86 Peugeot 205 B18C (in bits)

    #10 20th July 2007, 10:20

    Quote:

    Originally Posted by Soulless Hmmm - out of curiosity, if i was too launch my car, say on a normal tarmacc'd road... what RPM should I ideally launch a VTS at? ++ would this be different to the RPM I would need at the pod?

    the amount of revs you choose depends on the surface and the stickiness of the tyres. On a slippy surface you use less.
    Basically when I launch all I hear is a chirp from the tires and then its grip from there on. Can hurt the clutch though.
11. vtr130 Established Member Joined: May 2006 Posts: 2279

    #11 20th July 2007, 11:03

    Watch me launch at the pod then
    
    Get in between 3-5k dependin on if you want to go for it, slip the clutch out till you start moving then slowly release the rest of it No bogging down and not much wheel spin!!
12. KamRacing Saxperience Addict Joined: Nov 2006 A farm shed in Aylesbury Posts: 14916 Corolla AE86 Peugeot 205 B18C (in bits)

    #12 20th July 2007, 11:32

    If it works for you then that is the right way. Feathering the clutch is more difficult with a twin plate grp A one and slicks, which makes that technique impossible
13. craigy_87 Saxperience Post Whore Joined: Apr 2006 Wishaw United Kingdom (Scotland) Posts: 7326 Nissan 350z

    #13 20th July 2007, 11:52

    are those clutches kinda like all or nothing?
14. DamoVTS Established Member Joined: Jul 2006 West Sussex Posts: 1846 Clio 182 :D

    #14 20th July 2007, 11:52

    i feather the clutch when i do fast starts with my mate lol
15. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

    #15 20th July 2007, 12:00

    Quote:

    Originally Posted by craigy_87 are those clutches kinda like all or nothing?

    Hehe, it's like on or off!
16. Ryanp Super Moderator Joined: Feb 2004 Tonbridge United Kingdom (England) Posts: 38236 Vtr, 172, throttle bodied track slut

    #16 20th July 2007, 12:04

    muhaha! as i have said before on std set up it is indeed the best way to launch!
17. Karl Saxperience Hardcore! Joined: Apr 2006 Ashford Posts: 25611 LY R26

    #17 20th July 2007, 12:05

    I used to pratt about launching the VTR all the time (sorry Danr)
    but the VTS im too scared to do it really, dont want another box to go bang.
18. Danr Saxperience Hardcore! Joined: May 2006 Charming man Posts: 15880 Charming car

    #18 20th July 2007, 12:28

    Quote:

    Originally Posted by Soulless I used to pratt about launching the VTR all the time (sorry Danr) but the VTS im too scared to do it really, dont want another box to go bang.

    Ah, it was replaced anyway lol.
    
    IU find the best way to pull away is to have a fast car in the first place, then you can pull away as slow as you want and still win
19. Karl Saxperience Hardcore! Joined: Apr 2006 Ashford Posts: 25611 LY R26

    #19 20th July 2007, 12:46

    ~ true story Dan,
    but...
    that VTR flies off the mark i found.
    
    leave it about 2,400 RPM.
    play with the clutch as stated.
    BAM ~ lovely launch
20. vtr130 Established Member Joined: May 2006 Posts: 2279

    #20 20th July 2007, 13:56

    I need a decent clutch, but then i won't be able to slip it off the lights
    
    But my clutch always slips while changing gear!
21. djrem Saxperience Addict Joined: Feb 2007 Ramsden Bellhouse (Billericay) Posts: 12826 Various.

    #21 20th July 2007, 14:45

    out of the factory saxos arent race cars though.
22. Joesnow Frequent Poster Joined: May 2006 Posts: 691 Mk 1 VTS poseidon blue

    #22 20th July 2007, 14:46

    What research project are you doing? I would have thought you’d be finished uni now unless you’re doing a masters?
    
    I’m sure Toads pretty much got it spot on though… dont think its got much to do with inertia?... would get max acceleration when the wheels are on the verge of spinning (or the next best thing – slightly spinning, gripping, slightly spinning, griping…) which you could do by blipping the clutch or throttle
    
    What I recon the simulator will have done is given the wheels the max possible torque so that the tyres are constantly on the verge of slipping and its worked out that its better to hold the revs up and slip the clutch slightly than to drop the revs. Or perhaps a perfect combination of the two?
    
    What inputs did you put into the software?
    
    Would have thought it would be pretty tricky to do a perfect start every time unless you’re the Stig… I’m sure that’s how launch control works? Put that data into a controller for the clutch and throttle along with a few other things like coefficients of friction between the tyres and road surface and you’re off!
23. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

    #23 20th July 2007, 14:57

    I'm sure some of you have seen this clip before, but as we're on the subject...
    
    This was done with older gearbox, but it's still a good example. 0 - 60 in roughly 5.5 seconds, no wheel spin, and fed the clutch in from about 3500 rpm. I'm sure if I tried a few more times, I could have got a better start, as this one bogs down a tad. Still...
    
    http://video.tinypic.com/player.php?v=67x172c
24. Barry123 Saxperience Hardcore! Joined: Oct 2005 Aycliffe Posts: 32205 Saxo VTS

    #24 20th July 2007, 15:05

    Quote:

    Originally Posted by Joesnow What research project are you doing? I would have thought you’d be finished uni now unless you’re doing a masters? I’m sure Toads pretty much got it spot on though… dont think its got much to do with inertia?... would get max acceleration when the wheels are on the verge of spinning (or the next best thing – slightly spinning, gripping, slightly spinning, griping…) which you could do by blipping the clutch or throttle What I recon the simulator will have done is given the wheels the max possible torque so that the tyres are constantly on the verge of slipping and its worked out that its better to hold the revs up and slip the clutch slightly than to drop the revs. Or perhaps a perfect combination of the two? What inputs did you put into the software? Would have thought it would be pretty tricky to do a perfect start every time unless you’re the Stig… I’m sure that’s how launch control works? Put that data into a controller for the clutch and throttle along with a few other things like coefficients of friction between the tyres and road surface and you’re off!

    Yeah I'm doing masters man, although my research project is on Suspension Optimisation (Maximising Lateral Acceleration).
    My friend is working on a new type of gearbox which I cant bang on about unfortunately, but what i can tell you is it'll be 'mazin' and will kick ass
    
    We're using matlab, the car model is pretty damn complex to put it mildly.
    The torque outputs from the engine were obtained across the rev range then interpolated by matlab using Lookup Tables... I doubt there is any problem with the simulator applying full torque to the wheels as there is calculations in place with the gearbox, flywheel, clutch etc, recognising the associated losses with each and the friction co-eff of the clutch plates, mass moment of inertia of the flywheel and every other component. whats happening as i understand, my friend has determined the clutch input over time and the throttle is wide open throughout (i believe)... I'll ask him when he comes in.
25. medz_vtrturbo Established Member Joined: Jul 2007 anglesey Posts: 1055 saxo vtr turbo

    #25 20th July 2007, 17:21

    if u slip theclutch, it wrecks it in the long run. and if u do wheelspins and full throttle starts it wrecks the driveshafts as well as the tyres. if u want fast accelleration just tune up the car coz u would probably spend more on fixing the car than tuning it.
26. dannygti Saxperience Post Whore Joined: Feb 2006 dudley United Kingdom (England) Posts: 6790 106 gti/ SEAT LCR

    #26 20th July 2007, 17:46

    i am used to driving bike engined cars (westfields) and they have a "on/off" clutch so it makes launching very hard.the best way i find in that case is to rev it a bit more and get as little wheelspin as possible.