HeMan Posted June 11, 2015 Share Posted June 11, 2015 Hello,So, I have a 2006 k-series 1.8 that has been DVA tuned to 188bhp and 145lbft. I love it. But, whilst it is great on track, it is a little hard to keep on the boil on the road. I think this is due to a bit of a dip in the torque curve around 4.5-5k RPM, and you get looked at a bit funny if you drive around the roads keeping it in the 6.5k+ sweet-spot the whole time.So, I am doing what any bloke would do and trying hard to justify a bit of upgrading.I suspect the k-series is pretty much at its limit without becoming so highly-strung it will become a bit of a nuisance.As much as a 620R would be nice, it might be a bit too far from budget and as they don't do a SV, it isn't compatible with my back-side.So, 420 (or R400 in old money)??? But apparently it only has 5lbft more than mine (and about 25bhp)?! If I am going to spend £10 - £15k (including the px) on this sort of upgrade, am I really going to feel it was money well spent?Anyone else scratched this particular itch with satisfaction? Or got any real-world (beyond the dyno) experience to share? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 11, 2015 Member Share Posted June 11, 2015 Which gearbox do you have?The peak power doesn't seem to be the key factor that you're trying to improve... this is a great opportunity to share some power curves...Jonathan Link to comment Share on other sites More sharing options...
SM25T Posted June 11, 2015 Share Posted June 11, 2015 I have the 1.8 in VVC Form. Torque curve a dead horizontal line. I had Dave Andrews fit the 6-degree offset dowel (as you can't fit verniers on the VVC) ... and an exhaust cam with longer duration. This improved the mid-range torque. Then I changed the 4:1 exhaust collector for a 4-2-1 from Powerspeed. This gave yet more improvement in the mid range grunt. Ian Link to comment Share on other sites More sharing options...
HeMan Posted June 11, 2015 Author Share Posted June 11, 2015 5-speed. But you are right, this is more about mid-range than out-right power.Curves! I'll show ya mine, if you show me yours... Link to comment Share on other sites More sharing options...
Adrian Williams Posted June 11, 2015 Share Posted June 11, 2015 The 5 speed box is your problem, just get a 6 speed and keep the rest of your upgrade money in the bank. Link to comment Share on other sites More sharing options...
Mankee Posted June 11, 2015 Share Posted June 11, 2015 That is one nasty dip in the torque curve! Let me guess; you have a 4-1 manifold? A decent 4-2-1 manifold should sort that out. My 1.8 makes a peak torque of 160lbft. The torque curve looks a little bumpy on the rollers, so the map could do with some more refinement, but you can't feel it when driving.However, my real-world experience is limited to only flat-out track driving, rather than on the road. I also have a 5-speed box (but with a non-standard gear kit), so I tuned my engine for mid-range rather than outright top-end, engine-exploding power. Link to comment Share on other sites More sharing options...
Roadsport06 Posted June 12, 2015 Share Posted June 12, 2015 Adrian, is it as simple as just putting in a 6sp? Wouldn't that also need a change in diff away from a 3.9 for road use? Link to comment Share on other sites More sharing options...
revilla Posted June 12, 2015 Share Posted June 12, 2015 Surely the idea of swapping to a 6 speed is just to allow you to keep the revs way up in the power band for more of the time - which is what the OP is wanting to avoid? Link to comment Share on other sites More sharing options...
nickh7 Posted June 12, 2015 Share Posted June 12, 2015 I have a 1600K SS with a 5 speed and the switch to a 4-2-1 was amazing, even my 1600 just felt more gusty. I'd try that and then get a remap before changing your car . Talk to Dave again nobody has more knowledge on how to extract the best from your K , it might be that it needs a few tweaks to smooth that curve.There is also a modified gearbox which has a long first then a more closely stacked 2-5 to help keep the car in the sweet spot . How old is your air filter does it need a clean , I'd not done mine in a very long time and it made a difference , no doubt it was just a placebo Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted June 12, 2015 Area Representative Share Posted June 12, 2015 What a horrible torque curve!I can see why you struggle with a 5 speed 'box.I'm sure your existing set up could be make more drivable by filling in the hole in the torque curve.What exhaust does the current car have?I suspect the torque curve could also be improved with a tweek to the cam timing.If you want to justify a 2 litre duratec, then I'm sure that would have more torque over a much wider rev range than your existing K. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 12, 2015 Member Share Posted June 12, 2015 Caterham curves on dyno-plot. (This is the database to which DVA Power links.)Jonathan Link to comment Share on other sites More sharing options...
Adrian Williams Posted June 12, 2015 Share Posted June 12, 2015 I was being a little simplistic with my 'just swap the gearbox' comment but genuinely feel that the standard 5 speed box is a terrible match for a K.My first seven was a 1600 super sport K with a 5 speed box which I thought was great until I put a 6 speed into it and realised what I'd been missing. It transformed the car which then became a totally focussed driving experience and in my view was the best road seven I've ever driven and that includes my current R500K which is nothing like as enjoyable on the road.The standard 3.9 diff is a great combination with the 6 speed so it is just a gearbox swap.The dip in the torque curve isn't helpful and if it currently has a 4:1 fitted a 4:2:1 and a re-map would be on my list of things to do. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 12, 2015 Member Share Posted June 12, 2015 ... and in my view was the best road seven I've ever driven and that includes my current R500K which is nothing like as enjoyable on the road. That interesting suggestion again that lower powered 7s are more fun on the road. More details, please.Jonathan Link to comment Share on other sites More sharing options...
Mankee Posted June 12, 2015 Share Posted June 12, 2015 I think Adrian is implying that an R500K belongs on track as it is too hardcore for the road to drive hard unless you are irresponsible/like to risk your license/want to show off/are a hero. Link to comment Share on other sites More sharing options...
simonpa Posted June 12, 2015 Share Posted June 12, 2015 Agree with Adrian,I have had all sorts, including 2 R500s and the most fun cars have been the basic 1.6k (often ex-race cars). The R500s were amazing, I loved the way they just keep accelerating until you just hit the rev-limiter brick wall at 150. However, they are too quick for the road, you go to overtake a line of cars and can guarantee someone in the line will pull out without looking. They just make everything too easy; the only challenge is keeping the power down and holding onto your licence!Going back to the OP - the 6-speed does transform any K, as you can just keep it on the boil all the time. You really need to change the diff to a 3.6, but they are still quite easy to find. Actually, it's a good excuse to upgrade to a LSD at the same time! Link to comment Share on other sites More sharing options...
jackb_ms Posted June 12, 2015 Share Posted June 12, 2015 Like you I have a a dip in the power curve, and after an exhaust upgrade and a roller session all was a lot better. With regards more torque, have you thought about supercharging?It is something the the back of my mind...Jack Link to comment Share on other sites More sharing options...
HeMan Posted June 12, 2015 Author Share Posted June 12, 2015 I do already have a LSD (that was on my "must have" list when I bought it) but not sure what type beyond that.I will look in to some of the other sggestions when I get home and make post some pics...Thanks all. Link to comment Share on other sites More sharing options...
Adrian Williams Posted June 12, 2015 Share Posted June 12, 2015 JK, I'm happy to expand on my comments but have no wish to take this post off topic and my thoughts remain that HeMan would maximise his cars appeal simply by fitting a 6 speed box and filling in the torque curve a little.On the basis that you can't have too much of a good thing it doesn't really make sense to say that the R500 is too fast and as its fitted with a throttle pedal you don't have to use all that's available anyway. I've driven many sevens and they are all easy to drive down the high street at 30mph but doing that is not what I'd call stimulating or exciting because I don't feel I'm interacting with the car at any meaningful level.On the road my old 1600 had a lovely balance between grip and power which meant you could interact with it and USE it at a level where the car felt alive and was working for you while still covering ground at a more than reasonable rate. The R500 can still do that but if you make proper use of it so that it's truly working for you and feels intermate the speed at which you find yourself is completely absurd. It can of course be driven slower but then you loose the intermacy that was present with the 1600.Hope that makes a it more sense. Link to comment Share on other sites More sharing options...
HeMan Posted June 12, 2015 Author Share Posted June 12, 2015 So, this looks the be the first problem to deal with then?Maybe followed by a remap, 6-speed and supercharging (in that order, until I am satisfied). Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted June 12, 2015 Area Representative Share Posted June 12, 2015 HeMan,that 'zorst should not be too bad.I'd look to have a rolling road session and try swinging the cam timing. I suspect that running less overlap may well smooth out the torque curve.What has been done to achieve 188bhp? I assume you have TB's and a programable ECU?An 1800 making that sort of power should not have a hole in the torque curve like that. Link to comment Share on other sites More sharing options...
Mark Durrant Posted June 13, 2015 Share Posted June 13, 2015 What cams do you have? Link to comment Share on other sites More sharing options...
Nigel Riches Posted June 13, 2015 Share Posted June 13, 2015 Supercharging = super spending too do it correctly, cams, pistons, induction, re-mapping, and that's just to get a dip out of the torque curve, then the power output will be to much for the gearbox and differential, so throw more money at the car, then would the brakes be up to it, and different tyres, and so it goes on. Nigel Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 13, 2015 Member Share Posted June 13, 2015 Thanks, Adrian. I think you're not alone with that description.Jonathan Link to comment Share on other sites More sharing options...
elie boone Posted June 13, 2015 Share Posted June 13, 2015 If Caterham doesn't do a SV 620R, then just build one yourself. Link to comment Share on other sites More sharing options...
Grubbster Posted June 13, 2015 Share Posted June 13, 2015 Have you had it mapped or was that graph just a power run? Just for comparison here's mine - Link to comment Share on other sites More sharing options...
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