Anthony Posted January 6, 2003 Share Posted January 6, 2003 Hi Richard I have a ZF and had it set up by RRT at the same time as CWP change to 3.64 when 6 speed was fitted ( I cannot speak highly enough of their service ). The unit does clonk a bit in reverse though ( it has only done a v.small milage in the 12 years I have had it ) although it has only done this since being reset/6 speed going in so it could be the g'box ! Anthony Link to comment Share on other sites More sharing options...
RiF Posted January 6, 2003 Author Share Posted January 6, 2003 ZF is decided on. 😬 Will buy from Phil Stewart even though slightly dearer when Caterham take the diff of the starter kit but think I can get him to sort it out properly without a middle man being involved especially as the engine is non std Caterham set up. Interesting to know how to check pre-load later on. Thanks to all of you for a lot of very useful info. Lets hope the kit all goes together and that there is no trouble with the SVA Richard in France se7en weeks to go before delivery of chassis to start building my Duratec 7 😬 Link to comment Share on other sites More sharing options...
Rob Walker Posted January 7, 2003 Share Posted January 7, 2003 Richard your cheapest route is to source a secondhand standard diff 3.92 or 3.62 from a scrappy this will give you a casing and the crown wheel and pinion for around £80 , the rest can be discarded. Then buy the ZF LSD unit either fom RRT or Caterham and have it fitted. IIRC the ZF unit costs £580 and less than £100 to have is modded and fitted. Link to comment Share on other sites More sharing options...
jonhill Posted January 7, 2003 Share Posted January 7, 2003 Rob, The pre-load you describe the measurement of, is this the same pre-load that people are advising might be too much as supplied from Caterham? Or are you talking about something different, and if so is it possible to measure the pre-load that might be 65 but should be 30 (IYSWIM)? Jon Edited by - jonhill on 7 Jan 2003 14:02:48 Link to comment Share on other sites More sharing options...
Marius Posted January 7, 2003 Share Posted January 7, 2003 I´m quite sure that ZF do not produce the LSD´s anymore, stopped supplying them a few month back so they´ll be getting rare in the near future. Just build mine back from 4.11 to 3.92. Marius Link to comment Share on other sites More sharing options...
Rob Walker Posted January 7, 2003 Share Posted January 7, 2003 Jon, the 36 lbft preload that I refer is for the RRT modded ZF. Unmodded they are 55-60lbft, the AP suretrack was about 16 lbft and the quaiffe 10lbft . These are only guidelines not to be considered as accurate Phil Stewart put them all in the vice with a dummy driveshaft in on side and a torque wrench on the other and showed me the various torques as an aid to help me understand how the varius type worked. Link to comment Share on other sites More sharing options...
jonhill Posted January 7, 2003 Share Posted January 7, 2003 Right, so if I do as you describe with a torqure wrench on the hub nut, and I read ~60 ftlbs then I need it modding. If it's ITRO 30 it's already OK. Can ramp angles be checked in a similarly easy way, or is the pre-load just a symptom of the ramp angle anyway? Er, what is the ramp angle anyway? RRT are in kent aren't they? Is this adjustment something needing specialist knowledge and equipment? Cheers, Jon Link to comment Share on other sites More sharing options...
RiF Posted January 8, 2003 Author Share Posted January 8, 2003 Rob, Need a certificate of newness, so to get this think phil wants me to buy direct, shame though, thanks for the suggestion. Marius, Yes I gather it is not made any more but one can still get! Before there is a rush, let me get one first, so I don't have to decide again which diff to go for One last dumb question: If say with a 3.92 diff at 4000 rpm you are doing 27.1 mph in first, 41.6 in 2nd, 52.9 3rd, 64.0 in 4th and 73.6 in 5th what would be the approx difference in changing to 4.11 or 3.62 or 3.38 Bhp is say 185 and torque 160, wheels 13" using SPC semi helical 5 speed. Richard in France se7en weeks to go before delivery of chassis to start building my Duratec 7 😬 Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted January 8, 2003 Area Representative Share Posted January 8, 2003 Richard, Are you a Lotus123 user? I have a spreadsheet set up with various choices of gear ratio set, final drive ratio and wheel/tyre sizes that calculates road speeds at 1k rpm steps, but the spreadsheet doesn't transpose into Excel too well (mind you, that might be my fault, I'm not an Excel user!). Edited by - richard price on 8 Jan 2003 10:19:18 Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 8, 2003 Share Posted January 8, 2003 I couldn't post this last night. Trying again now. Ramp angle and preload are independent. Ramp angle cannot be checked with a static test, but if you have 60lbft preload chances are you don't have 30 degree ramps. The diff consists of a normal diff with a separate clutch mechanism. The clutch is preloaded so that for the two sides to move independently, a certain torque difference must be experienced from one side to another (the preload torque). The clutch is made up of... think of it as two round ashtrays, with regular cutouts for four ciggies around the circumference. The ciggie cutouts are made as V-shapes with specific angles. The two ashtrays are arranged cutout to cutout. A crucifix of round bar lives in the middle with its four arms sticking out through each cutout. When you try and rotate the two ashtrays relative to each other, the arms of the cruciform force the two ashtrays apart. When the two sides of the diff move relative to each other, the preloaded clutch drags the two ashtrays in opposite directions and they get forced apart, binding the clutch with more and more force until equilibrium is reached. In the Phil Stewart/Caterham modifications, the preload is lower so that cornering is still possible, but once the torque difference builds, the diff locks up quicker, as befits a race car. Link to comment Share on other sites More sharing options...
RiF Posted January 8, 2003 Author Share Posted January 8, 2003 Richard, No not a Lotus 123 user but could you e-mail me them anyway and I will try to open them. e-mail: easiclad@aol.com. Many thanks, lets hope. Richard in France se7en weeks to go before delivery of chassis to start building my Duratec 7 😬 Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted January 9, 2003 Area Representative Share Posted January 9, 2003 Richard You have mail Link to comment Share on other sites More sharing options...
Bilbo Posted January 13, 2003 Share Posted January 13, 2003 Hi All Well almost thread Highjacking but same subject. Is all rather a case of a wish list as I doupt I will get time to do it before the winter. I have to say overall gearing for best performance is a subject that leaves me rather dead. My cars has a 3.92 LSD fitted in 1988 and I have no idea what the preload or ramp angles is set up in the diff. Nor am I really sure what effect they both have on the car. Read on........ My Quaife box is 2.39, 1.54, 1.2, 1:1, 0.93 5th So all this chat on preload or ramp angles makes me wonder what mine are, anyone know 🤔 was bought from Caterham and has done say 55,000 miles. I gather that since the JPE they have changed the settings. Well as my BD now has more power and torque I have been considering changing to a 4.11 or 4.44 to get the most out of the engine by keeping it in the cam range but with a reduced top speed. Reason well lots of times on the track I find the car going off cam out of a corner on track days and sprints. Well one solutions to go faster in BUT.... Previously to try to cure this I fitted the 13" rims with A032 205/60/13 on 7.5 x 13 rims the old ones were 14". Alas NO gain on keeping on cam, as the 13" tyres and wheels have the same overall diameter as the old 14" ones. So if I change the diff to keep the engine on the boil what preload or ramp angles 🤔 Now lets start on the basis that this is properly a load of rubbish Also on the basis I have never seen one apart BUT if I have understand correctly. Ok why LSD well on the track or anywhere else for that matter in cornering the inside wheel goes light. The LSD transfer's power to the outside wheel and the car tends to keep the power down hopefully lessening the loss of torque hence power to the inner wheel. The preload can be adjusted by thickening the diff plates (Err think that's correct) So the LSD can be set up to suit an individual cars weight and power, ok so how. Well by varying the Preload a Ramp Angles I gather older style LSD's do not have facilities to vary the ramp angle not sure if this effects mine 🤔 Preload or rather static preload Ok what's mine new what should it be to be better 🤔 Looking on the web previously what I have read its cross-axle torque transfer point at which one wheel is allowed to slip in a when one of the wheels has zero grip. The desired preload is based on the mass of the car and what your trying to achieve road, race, grass track or off road 🤔. My current interest is for spinting. Its setting is also relative to grip. Higher figures are used where good grip availability. Where poor grip availability i.e. say grass track lower figures are used. Also it is varied by altering the clutch plate configuration. How am I doing so far is this correct. 🤔 As to car weight wheel more weight more grip 🤔 Ramp angle This is were I get very Ok what is ramp angle seems to be related or is the cam ring angle what's a cam ring. What's mine new and what should it be to be better 🤔 It seems to be the fine tuning of the static preload 🤔 Well not all diffs have this adjustment does mine 🤔 So from what I have read this or rather "these" have an effect on locking action of the diff on acceleration AND deceleration. Its actually 2 angles most seem to quote something like 90/50 road use 90/30 track or sprint or hill climb and 60/40 for grass or rally If I have followed it correctly say at 90 degree ramp effectively unlocks the diff. Then it behaves like a non LSD. (correct ?) What leaves me stumped is what the lower angle does 🤔 The ramp angles have effects on the power down and on over-run the upper figure effects the power down, the lower which is getting towards releasing diff on deceleration improves turn-in and reduces understeer. So how did I do is this a load of rubbish All this leaves out which just stay with the current one and having it modified or buy the Quaife Automatic Torque Biasing or a ZF.......... but that's another posting hopefully a few replies might make my mind up. Current favourite is to go the whole hog with a 4.44. Then again other have argued that a 3.6 would be better so that I can hold lower gears longer. However seems to me that this is just a good for cruising option. However, a change to 2.04 1st gear might be a good idea in this case more time more money. Any infirmed repiles would be welcomed Oh anyone have an alli bell housing for sale. 🤔 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 14, 2003 Share Posted January 14, 2003 Changing diff ratio doesn't close the rev drop between gears, but you will be selecting higher gears at any given speed. The rev drop between the higher gears is shorter than the rev drop between lower gears, but the effect is marginal. It is also pointless to have one gear in five that is useless because it is out of range. Looking at the info below, it looks like a 4.4 would really help you get up the straight at Curborough, making use of 3rd gear on both laps. 53 mph as a max speed in first is OK. With a 4.4 you would get: Gear Mph per 1000 RPM Mph @7900 RPM Mph @8300 RPM -------------------------------------------------------- 1 6.42 51 53 2 9.96 79 83 3 12.68 100 105 4 15.34 121 127 5 16.50 130 137 Mph RPM (in Gears) ------------------------------------------------- 1 2 3 4 5 ------------------------------------------------- 5 779 502 394 326 303 10 1558 1004 789 652 606 15 2337 1506 1183 978 909 20 3116 2008 1577 1304 1212 25 3895 2510 1972 1630 1515 30 4674 3011 2366 1955 1819 35 5453 3513 2760 2281 2122 40 6231 4015 3155 2607 2425 45 7010 4517 3549 2933 2728 50 7789 5019 3944 3259 3031 55 5521 4338 3585 3334 60 6023 4732 3911 3637 65 6525 5127 4237 3940 70 7027 5521 4563 4243 75 7529 5915 4889 4546 80 8031 6310 5215 4850 85 6704 5541 5153 90 7098 5866 5456 95 7493 6192 5759 100 7887 6518 6062 105 8281 6844 6365 110 7170 6668 115 7496 6971 120 7822 7274 125 8148 7577 130 7881 135 8184 Gear Change RPM drop (change @7900) RPM drop (change @8300) ------------------------------------------------------------- 1 -> 2 -2810 (to 5090) -2952 (to 5348) 2 -> 3 -1693 (to 6207) -1779 (to 6521) 3 -> 4 -1371 (to 6529) -1440 (to 6860) 4 -> 5 -553 (to 7347) -581 (to 7719) With the 3.92 you have: Gear Mph per 1000 RPM Mph @7900 RPM Mph @8300 RPM -------------------------------------------------------- 1 7.21 57 60 2 11.18 88 93 3 14.23 112 118 4 17.22 136 143 5 18.52 146 154 Mph RPM (in Gears) ------------------------------------------------- 1 2 3 4 5 ------------------------------------------------- 5 694 447 351 290 270 10 1388 894 703 581 540 15 2082 1341 1054 871 810 20 2776 1789 1405 1161 1080 25 3470 2236 1757 1452 1350 30 4164 2683 2108 1742 1620 35 4858 3130 2459 2033 1890 40 5552 3577 2811 2323 2160 45 6246 4024 3162 2613 2430 50 6940 4472 3513 2904 2700 55 7634 4919 3865 3194 2970 60 5366 4216 3484 3240 65 5813 4567 3775 3510 70 6260 4919 4065 3780 75 6707 5270 4355 4051 80 7154 5621 4646 4321 85 7602 5973 4936 4591 90 8049 6324 5226 4861 95 6675 5517 5131 100 7027 5807 5401 105 7378 6098 5671 110 7729 6388 5941 115 8081 6678 6211 120 6969 6481 125 7259 6751 130 7549 7021 135 7840 7291 140 8130 7561 145 7831 150 8101 Gear Change RPM drop (change @7900) RPM drop (change @8300) ------------------------------------------------------------- 1 -> 2 -2810 (to 5090) -2952 (to 5348) 2 -> 3 -1693 (to 6207) -1779 (to 6521) 3 -> 4 -1371 (to 6529) -1440 (to 6860) 4 -> 5 -553 (to 7347) -581 (to 7719) Link to comment Share on other sites More sharing options...
Bilbo Posted January 14, 2003 Share Posted January 14, 2003 Hi Peter Thank you for your reply......... I Err have done all this bit with the ratio's and as you ended up with preferring the 4.44. Thanks for the effort sorry as I should have said so. However, having established the speeds I felt a bit lost on what either would achieve on the track. Its all very obvious for foot down on a endless straight. Well obviously what's good for long straights at Silverstone is not good for Cadwell. So you can never have everything if your not into box and diff changes between events.... unless you have a nice Hewland box trans axel ❗......... dream mode off back to reality . Actually anyone ever fit one in a Caterham 🤔 Then again nor is 18.75 stone in the drivers seat . At Cadwell I can easily hit 110 mph on the straight some times push over 120 mph. The real problem is going off the boil out of the first bend at Charles and the bend into the mountain. In the later case if I use second its too slow if I use third its off cam. Nice fast spin in third going up the hill . What most seem to do is take the bottom bend in third and snatch second half way up at near max revs in second. So this prompted the suspension change..... Then again at Curborough I seem to spend too much time in first at max revs when I should be in second and second when I feel 3rd is where I should be ❗. At any time flat out the last thing you want to do is run out of power at the exit of a bent trailing the gear at max revs, whilst all the world passes you by... Its all rather relative, in my car, to keeping over 5500 rpm. Hence the interest in a 4.44. Conversely if I had a 3.36 I would be faster in the lower gear or rather could hold them longer, seems to work well for others on those days. Hence my I do take your point on faster acceleration on the straights with the 4.44. As to 5th being 0.93 well its not that expensive to get a 0.88 fitted for motorways. Noisier in 5th but what the hell. I am much more interested at the moment on preload and ramp angles rather seek some assurance that what I understood was correct. Its far too easy to light up the A032's at a start and I think I getting oversteer a little to sudden or rather the tyres stick like glue and then go that's not what A032's are supposed to do ❗ So if I have followed what I read lower preload and ramp angles help its very unlikely mine are anything other than standard. 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY Edited by - Bilbo on 14 Jan 2003 21:36:50 Link to comment Share on other sites More sharing options...
RiF Posted January 16, 2003 Author Share Posted January 16, 2003 Well as I started the thread and it has now been hi-jacked onto the next subject I am trying to sort out I thought I might as well take advantage. Gear ratio's and diff ratings are totally blowing my mind!!!!! I know it is a very personnel thing but everyone suggests different diff ratings and after Richard e-mailed me a spread sheet to put in my own numbers it has not helped to reach a conclusion. Facts: I will be having a 5 speed box either std version or semi helical SPC version. Ratio say 2.36 / 1.54 / 1.21 / 1 / 0.87 or 0.82. Car to be used 80% on the road, 20% track days. Acceleration 0-100mph most important, top speed limited by windscreen but may have interchangeable aero's later. Engine is the Duratec with a starting 185 ish BHP but may tune further sometime, torque is starting at say 160, but at what rev's I cannot confirm as I am stuck in Belgium for a few more days. Maximum rev's are I think say 7200 until further tuned and I think it may get up to 8300. Wheels will be R500 13" 185 and then 60 or 70 tyres, after reading perhaps problems in getting the 60's. The extra ground height is also an advantage. I do not want lots of revs on cruising at say 80mph on a long trip (France to UK). Although acceleration is the key issue for me I do not want a car that is not road friendly. Several people / businesses have said go for 3.62 or even 3.38 diff but Raceline are saying go higher than the 3.92 even up to a 4.4 (something). All advice welcomed so that I may see some light in discussing the facts with the diff companies. Richard in France six weeks to go before delivery of chassis to start building my Duratec 7 😬 Link to comment Share on other sites More sharing options...
Bilbo Posted January 16, 2003 Share Posted January 16, 2003 Hi Richard Well I had not intended to totally highjack. I had intended to talk just about preload ramp angles...... err then wondered Please accept my apology. 😳 Reading all that others said I am leaning towards a ZF if that helps. Not fully decided still Quaife have a nice gear/ speed calculator so does Dave Andrews home page but it does not like win 2000 on my computer. As to the box and 5th the nearer you are to 1:1 the quieter the box if you drive with the hood up worth remembering. At 1:1 no square cut gear noise well very little.... So 3.62 less acceleration higher top but will you ever really reach the speeds answer NO a Caterham is just too blunt at the front and with the outboard rear wings has massive drag. Best not get on to cycle verses clam as neither are that great compared to a fast tin top. Well mines seen over 130 on the clock true speed well your guess is as good as mine. 🤔 The 6 speed plus 3.92 suits the 1400/1800 K and X series non superlight but you have much more torque 160 lbs ft verses max for those at 130 lbs ft. However your carrying a heavier engine and box (unless you have a alli box case and bellhousing). Superlight use 3.62 diff but as a part of the fact they are super light and have 6 gears So your a half way house between 15 bhp less than the R400 Superlight but more torque 10 ft lbs. (aside to Peter C BHP verses Torque ). I am looking at more track use than road sadly because I now get far less time to go out in the car. Its rather become a sunny days car but life can always change and does regularly in my work style then its back to every day as often as possible So for you its rather like me chose your USE chose your diff. In my case as Peter said is more acceleration so a 4.44. In your case the 3.92 or 4.11 or 4.44 matched to the 5 speed might be better overall. If 0-100 is your main aim then a 2.04 first is a better bet. I rather chose the 2.39 as I was interested in town driving at the time as I live on the outskirts of London. Tyres smaller O/D better I use A032's 205/60/13 on special 7.5 R500 wheels but the overall O/D same as 14" 185/60/14. The R500 standard rather relies on bespoke caterham radials or crossplys I now rather think a 2.2 first gear might have been a better choice. I think I could even handle 2.04 and suffer London driving. Its all rather relative to the overall power/torque curves more low down the lower overall gear you can live with yours should be a lot better than mine. The more torque the better you can live with off the line and the bigger revs drop first to second. As to a cruising at 80 mph in France on a long trip, well the BDR spec, old standard box plus the current 3.92 managed a lot better than that no problem on a Caterham Swiss trip then on to Munchen and just under 110 mph average speed on the autobahn for 400 miles (0.88 5th) . As to your final choice well it should be suited to the final engine spec no point in paying twice. Trust this is some help if your near south London any time and I am free e-mail me I will give you a nice peaceful ride in the car my modest 1700 cc is not that far off your current spec taking the differences in BHP and torque. It has to be said for acceleration 160 ft lbs is much better. Well not an answer but a few ideas. If I had an answer I would not be asking very similar questions. The real truth is like me you really need a ride in something similar that has the alternative for both of us this is a limited option. Hello..... its gone rather quite anyone out there chaps, with a point of view for Richard and / or me.......... 😬 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY Edited by - Bilbo on 16 Jan 2003 22:25:12 Edited by - bilbo on 21 Jan 2003 18:41:05 Link to comment Share on other sites More sharing options...
RiF Posted January 18, 2003 Author Share Posted January 18, 2003 Hi Bilbo, I did not mind your hi-jack, all info is required by me and I think my subject had really finished except the next question on that you have now asked for me. Maybe we need to do another heading to get further help. Thanks for your notes and the invitation. Maybe in late February. I do think we need more advice or test drives to make up our minds. I may be able to do that with 2 similar Duratec cars, one with I think a 5 speed 4.11 diff the other with a six speed 3.62 diff. I know the gear boxes are different but by finding out the ratios I could perhaps get a better idea. By going to 2.09 or 2.2 first gear what do you mean about driving in traffic? Is it just too sudden / sharp for moving slowly? PS The Duratec is only going to be 3 1/2 kgs heavier than the K and I am thinking about an ally gearbox to keep the weight down as has been recommended as I will surely want to do it later if I don't do it now. Richard in France six weeks to go before delivery of chassis to start building my Duratec 7 😬 Edited by - richard in france on 18 Jan 2003 18:27:46 Link to comment Share on other sites More sharing options...
felix.klauser Posted January 18, 2003 Share Posted January 18, 2003 I used to run a 210bhp Zetec with a Quaife 5 speed box and a 3.92 diff ratio in my 7 with an aeroscreen. On the very long straights I would eventually hit the rev limiter (7200 rpm) in 5th but only just. To me that meant the gearing was pretty close to correct. Lower gearing would have meant better acceleration but a reduced top speed and higher gearing would have meant slower acceleration and possibly a lower top speed. If you go with a 4.1 diff ratio I think you'll need a higher rev limit or you'll be bouncing off the rev limiter in 5th gear from time to time. The Quaife box with a 2.39 first is a bit more friendly for road use as a bit less clutch slip is required to start off and you stand a better chance of being able to crawl in traffic at 800 rpm without trying to push the car ahead of you. A 4.1 diff would counteract the 2.09 first somewhat. Link to comment Share on other sites More sharing options...
Bilbo Posted January 19, 2003 Share Posted January 19, 2003 Hi Richard 2.04 not 2.09 as I posted before or 2.2 first gear in traffic is like constantly pulling away in 2nd in a tin top. If you have sufficient torque its no problem. If you want a quick off the line the lower the number the higher the revs. Also in very slow moving traffic you ride the clutch. In a Caterham you can live with the lower numbers as the cars are much lighter than the average tin top. Standard 5 speed box is just overgeared hence the Quaife mind you I was not that unhappy with it for 10 years until I had RK liven the engine up a lot. So I went for the larger number never having driven a car with any of the 3 ratios. Now if I have a 4.44 I would love a 2.04 to give that higher to speed in first. Thats on the main shaft so not a cheap mod. So 2.04 with 3.92 top speed in 1st gear = 67.989 MPH and changes into 2 gear at 6266 RPM dropping 2034 RPM 2.39 with 3.92 top speed in 1st gear = 58.032 MPH and changes into 2 gear at 5348 RPM dropping 2952 RPM however, 2.04 with 4.44 top speed in 1st gear = 60.26 MPH and changes into 2 gear at 6266 RPM dropping 2034 RPM So 2.39 with 4.44 top speed in 1st gear = 51.236 MPH and changes into 2 gear at 5348 RPM dropping 2952 RPM Then again, 2.04 with 3.62 top Speed in 1st gear = 73.623 MPH and changes into 2 gear at 6266 RPM dropping 2034 RPM 2.39 with 3.62 top speed in 1st gear = 62.841 MPH and changes into 2 gear at 5348 RPM dropping 2952 RPM So the difference is 10 mph with same rev drop but its much easier to move away with the 4.44. In reality 3.92 is the half way house between the max speed of the 3.62 and the max acceleration of the 4.44. What you chose is relative to what your going to do with the car and the O/D of the rear wheels and tyres. As to ratios in the 5 speed Quaife basically the above gears and what I posted before. Plus 1.69 second and 0.87 or 0.93 5th gear. Also 3rd is 1.21 I been posting my 3rd incorrectly as 1.2 . As I said before I chose 0.93 for 5th just because the closer you are to 1:1 the quieter the gear if you want better fuel consumption long distance go for the 0.88. I would say I use 5th a lot more now. Previously it was virtually a motorway only gear. From Caterham's site for standard 5 speed 1st: 3.65 2nd: 1.97 3rd: 1.37 4th: 1:1 5th: 0.82 Reverse: 3.37 and 6 speed 1st: 2.69 2nd: 2.01 3rd: 1.59 4th: 1.32:1 5th: 1.13 6th 1:1 So if you look here you will find the Quaife gear speed calculator. Also if you look on the site you can find the 2003 Product Catalogue where the ratio details came from. The 5 speed sierra dog box has a greater choice of ratio's in second ane third but your unlikly to choose them given the weight/torque of your engine plus you view to have it breathed upon. As to felix comment on the rev limiter.... well cheers felix thanks for the post, mine revs to change @ 8300 with max power @ 7750 but it may be more relevant for you Richard. Flat out in 5th is about 7500 in mine not that I was looking at the rev counter.... what was going on around me seemed far more important at the time *wink* Actually felix why is the rev limiter set so low if you have 210 bhp does this allow for the few extra revs for the gear change or is it not a steel crank/ rods 🤔 As to no comments well that's really part of the above your choice. Also I suppose they are all too busy slagging birkin off on the other channel (Chitchat)........ 😬 😬 😬 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY Edited by - bilbo on 21 Jan 2003 18:56:54 Link to comment Share on other sites More sharing options...
Bilbo Posted January 19, 2003 Share Posted January 19, 2003 Hi Peter re-reading your post I do not understand one comment "looks like a 4.4 would really help you get up the straight at Curborough, making use of 3rd gear on both laps." Did you intend to say "5th gear on both laps" 🤔 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY Link to comment Share on other sites More sharing options...
felix.klauser Posted January 19, 2003 Share Posted January 19, 2003 > Actually felix why is the rev limiter set so low if you have 210 bhp does this > allow for the few extra revs for the gear change or is it not a steel crank/rods It was the standard bottom end and I didn't see the point of revving to 7600 rpm that is the suggested max revs for that spec. Too much wear and tear and not enough gain. Link to comment Share on other sites More sharing options...
Bilbo Posted January 19, 2003 Share Posted January 19, 2003 Hi Felix It was the 210 bhp at that rev was what left me puzzled seems you have a beastie. I do very much agree that the lower the rev = much less wear that = less rebuilds = less spend. Also its saved you more than a few bob keeping the standard bottom end. However, you need to have an over than max to keep the power on a change more important on 1700cc . I went for the max bhp on carbs whist keeping sensible reliability, to do this the Doug Kiddie crank was the most expensive bit of the rebuild. 'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬 1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY Edited by - bilbo on 19 Jan 2003 19:20:37 Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 20, 2003 Share Posted January 20, 2003 Bill, In answer to the "third gear" comment... On any straight I presume you change gear appropriately at a short interval after peak power revs and not before. The last rolling road figures I had for your car showed peak power at 7900 and max revs at 8300. I presume that on each pass of the straight at Curborough you will rev to about 8200-8300 in 2nd and then select 3rd gear. On the first pass you are unlikely to get beyond 92mph. On the second pass you are unlikely to get beyond 97mph before the finish line. The most effective gearing for a straight where you have to change gear is to run out of revs just as you arrive at the braking zone. This is important on the first lap at Curborough. With the 4.4 diff, you don't quite achieve this in 3rd because the gear runs out at 105 mph (you are still overgeared, but it does mean you are using 2nd and 3rd for most of the run rather than 1st and 2nd. The rev drop at maximum revs from the gearcalc table is: 2952 (revs pick up at 5348)for 1st to 2nd as opposed to just: 1779 (revs pick up at 6521) for 2nd to 3rd. By bringing the gearing down so that you are using 2nd and 3rd rather than 1st and 2nd, we have in effect closed up the ratios on the gearbox and will keep the engine on cam. 5th gear doesn't have any bearing at all for a sprint run at Curborough. Link to comment Share on other sites More sharing options...
windy1 Posted January 20, 2003 Share Posted January 20, 2003 You all seem to be perfectly happy to spend hours setting up your plate diffs. Too complicated and too time consuming in my opinion! I've used the Quaiffe ATB in a hillclimb sprint car which has so far required no maintenance, uses normal diff oil, has been bullet proof, shows no slipping of an airborne wheel (as some of you describe) & does no induce understeer. I also use Phil Stewart to build it for me (about 4 years ago)! Windy Link to comment Share on other sites More sharing options...
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