mark4newman Posted August 5, 2002 Share Posted August 5, 2002 ohhh.....bhp at the wheels mentioned...... M100EOW.... Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 5, 2002 Share Posted August 5, 2002 Jag, My more specific point is this: Tyre adhesion is greatest at ~8% slip. Between clutch balance and revs, you are aiming for 8% slip. This slip means that the tyre operates for a period from standstill at friction limited grip. The power that is accelerating the car is exactly equal to the frictional force multiplied by the car's instantaneous road speed, which is a lot different from the maximum power potential of the engine. If you operate the throttle such that the engine develops more power than this, it either gets scrubbed off in the clutch or at the tyres, but doesn't deliver any more acceleration - usually less if you are spinning up the tyres. What this means is that from any standing start, there is a period at the start where the acceleration is determined by grip and not by power. Therefore from a 4 second potential 0-60 time for a 200bhp seven, subtract, say, 1 second of launch shenanigans and consider 3 seconds acceleration to be determined by engine power. Therefore with a 100bhp seven, the same first second acceleration may be achieveable, followed by 6 seconds of engine determined acceleration. 0-60 in 7 seconds. *thumbup*253 bhp, up and running *thumbup*New boingy bits Link to comment Share on other sites More sharing options...
JAG Posted August 5, 2002 Share Posted August 5, 2002 Peter, I completely agree. Acceleration is ALWAYS limited by grip, assuming your engine has enough power to break traction. If your engine generates a force (at the tyre to road interface) that's greater than the weight of the vehicle acting on that tyre multiplied by the tyre adhesion factor (a combination of the coefficient of friction plus the mechanical grip) the wheels will spin. Once the wheels start spinning you are wasting power. The limit to straight line acceleration is tyre to road adhesion, it's also the limit for all other forms of acceleration like braking and cornering! As an approximation my calcs are pretty close. Close enough to give the kind of performance increase Steve is looking for, the rest is down to technique - as you have pointed out. Link to comment Share on other sites More sharing options...
peterg Posted August 5, 2002 Share Posted August 5, 2002 Just my tuppenceworth...not theoretical but actual data Last year my AP22 meter recorded my 0-60 as 4.83 going southbound on the A24 from West Grinstead traffic lights (not the grippiest of startlines!) on oldish Yoko A510 tyres 185/55-13 - the car is very short geared so 2nd gear just gets over 60mph (64 from memory) at 7100rpm At Shelsley Walsh earlier this year 'best' first 64ft recorded was 2.32 secs on well scrubbed 185/60-13 Bridgestone RE720s All done via an 1800 Zetec on twin 45DCOEs and Alpha management with a Quaife sccr and LSD (4.1) in a W*stfield weighing about 520kgs..... Link to comment Share on other sites More sharing options...
puremalt Posted August 6, 2002 Share Posted August 6, 2002 My John Smurfit tweaked XF with 145 dynoed BHP and 137lb/ft is 5.2sec. If you run the car on roads you must have a cross flow because of the SOUND-its sex but not as we know it. Sorry to sully the intelligent comments on this thread chaps. Dave Robertson Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 6, 2002 Share Posted August 6, 2002 JAG, Perhaps then you could explain why your formula presumes that grip is proportional to engine power then. Link to comment Share on other sites More sharing options...
JAG Posted August 6, 2002 Share Posted August 6, 2002 Peter, at no point do I even consider grip in my equation. I simply ratioed the current 0-60 time with the required 0-60 time and used that value to propose an increase in power output. I have simplified the whole problem into a question of power. I have ignored all other variables because it would be incredibly complicated and prone to enormous inaccuracy. I have assumed that the engine already has enough power to spin the wheels. The drivers ability to make the most of the available grip (by not spinning the wheels and generating maximum force) will limit his 0-60 times. The F1 teams have recognised this fact by fitting "Launch Control" systems to their cars. Edited by - JAG on 6 Aug 2002 15:41:34 Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 7, 2002 Share Posted August 7, 2002 I'm not on a mission to add unnecessary complexity to the problem. However your formula will leave Steve short on power. You need more power than your formula suggests to get the desired 0-60. This is why 0-60 is an area of diminishing returns. *thumbup*253 bhp, up and running *thumbup*New boingy bits Link to comment Share on other sites More sharing options...
murph7355 Posted August 7, 2002 Share Posted August 7, 2002 Add 42. Link to comment Share on other sites More sharing options...
Big Brother Posted August 7, 2002 Author Share Posted August 7, 2002 Andy, Is that the definitive answer? Upgrade the 118bhp to 160bhp. OK, next question....what will need to be done to achieve 160bhp from a standard crossflow? Steve www.Se7en-Up.co.uk Link to comment Share on other sites More sharing options...
cdg Posted August 7, 2002 Share Posted August 7, 2002 Throw an awful lot of money at it! Speak to Dave Brooks or Roger King. Chris. Link to comment Share on other sites More sharing options...
John Posted August 7, 2002 Share Posted August 7, 2002 ..Or dont spend so much money and speak to Rob Morley at Pro-Tune on 0208 449 4447 instead. John Edited by - John on 7 Aug 2002 11:47:35 Link to comment Share on other sites More sharing options...
edmandsd Posted August 7, 2002 Share Posted August 7, 2002 I think the definitive answer to the original posting is NO. Link to comment Share on other sites More sharing options...
Big Brother Posted August 7, 2002 Author Share Posted August 7, 2002 Thats the conclusion I came to too 😬 I guess it will be a case of throwing all my spare cash in the direction of Roger King and seeing what I get back. Got to admit, that was the idea I came up with before making the post. Oh well, its only money Steve www.Se7en-Up.co.uk Link to comment Share on other sites More sharing options...
EFA Posted August 8, 2002 Share Posted August 8, 2002 Before you speak to Pro Tune, speak to Club Member Kevin Ford who's car has been off the road for a very long time. It has a Pro Tune engine and they have certainly been unable to fix the problem in an amicable and timely fashion. Link to comment Share on other sites More sharing options...
tom7 Posted August 8, 2002 Share Posted August 8, 2002 Whilst the 0-60 is an entirely superficial measurement, it makes for entertaining pubtalk. With my bog standard 120bhp 1.8 K, 5 speed box and 14" Avon ZV1's I managed a 2.34 seconds 0-64 foot time at Curborough in March. Comparing this to peterg's time of 2.32 with his well specified motor, LSD and 4.83 0-60 time, I am encouraged that I am able to at least match or better the factory time. I would agree that technique plays a large part in a successful launch. My best efforts were achieved with 2500rpm and a slipped clutch, whilst some (slower) competitors are max rpm and sidestepped clutch! Tom Link to comment Share on other sites More sharing options...
murph7355 Posted August 8, 2002 Share Posted August 8, 2002 I still think throwing the money at a Superlight will give you so much more to excite the fleshy parts than chucking it solely at the engine, lovely as XFs sound. And by doing that you are then on the first step of the ladder and can chuck money at that engine in a few year's time, rather than being close to the top of the ladder of what's practically possible... BUT I'm the last one that could be accused of being sensible so Roger King's door would seem a good place to start. Link to comment Share on other sites More sharing options...
John Posted August 8, 2002 Share Posted August 8, 2002 Arnie, My engine has a Pro-Tune engine and I cannot fault their workmanship or their customer service. Rob is a very knowledgable chap and has sorted even the slightest problem with my engine without it being down to any fault of his own, without charge, fuss or complaint. Top service and workmanship in my opinion and wouldn't hesitate to recommend them to others. John Link to comment Share on other sites More sharing options...
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