Duratec in detail

[Dominic]

Great times & result! Well done

[David]

A few months have passed since I last posted here. In that time the engine has bedded in and I've upped the RPM and put some decent tyres on the car. The net result is that my SLS lap times are now in the 55's. But the faster you go, the less time there is, and things like gear changes become more significant. Whether it is my mid-life crisis, or just the pleasure I get from these projects, I'm not sure, but I've decided to replace the gearbox with a Sadev sequential unit, partly justified by the knowledge that the Caterham 6 is now at the limits of its design torque. After a long wait it arrived on Wednesday



It is a bespoke Caterham unit with straight cut gear and proper dog engagement with ratios chosen to use all six gears at KH. It will be fitted with the Geartronics ECU to provide clutchless flatshifting. It is really for next year, but I plan to fit it after next weekend's SLS and I'll use it for the final in September. A later phase will be to fit a pneumatic system and paddle shift.

[graeme]

Ohhh, that's nice!

[Ferg]

:

[Dominic]

Nice one! I must pop round some time when you are spannering.

[David]

Nice one! I must pop round some time when you are spannering.

[David]

Just an update on this! The gearbox installation was postponed as a chassis mod was required to fit the uprated prop shaft. The plan is now to do it after the season has finished. While I have the chassis stripped for this I have decided to upgrade the fuel system and fit taper throttle bodies. I'm hoping this will improve the mapping issues i had and release a few more BHP. The bits arrived today

[KingK_series]

Just an update on this! The gearbox installation was postponed as a chassis mod was required to fit the uprated prop shaft. The plan is now to do it after the season has finished. While I have the chassis stripped for this I have decided to upgrade the fuel system and fit taper throttle bodies. I'm hoping this will improve the mapping issues i had and release a few more BHP. The bits arrived today

Just a note of warning David - I've done a lot of number crunching and design manufacture of throttle bodies = my engines have completely bespoke systems

- getting the design right is very complicated and requires viewing the system as a whole - for instance the correct taper - is actually a reduction in volume between trumpet and valve - tuned length is more important, resonant air box volume even more important [ you have a sponge - ie no air box] ALL MUST WORK TOGETHER

- imagine chopping arbitrary lengths of a church organs' pipes - would it play in tune - of corse not

- sadly manufacturers think they can sell part of the equation [the taper] and it will give a result, it's a bit scandalous really.

a 2L on a 12mm lift cam with a correctly designed resonant chamber/tb system/correct valve chamber/exhaust is a 320bhp engine NA,

anything less is not - not enough cam, or not the right TB system ....... the fault is that everything is not working together.

best wishes simon

[robin]

Simon, you make the analogy of organ pipes, which is no doubt relevant.

At the 7,000 RPM engine speed, valve open/close frequency is approx 60Hz. The length of a pipe with resonance at 60Hz is 3m. So presumably we're not talking about a standing wave as 3m intake runners would be impractical ... that begs the question, what are we talking about?

Cheers,
Robin

[David]

I take on board what you are saying Simon. I don't have the resources to anything other than purchase what I consider to be the best bet. In this case it was a discussion with Troy at Northampton Motor Sport where I mapped the engine. Troy did not recommend these, or another setup - he's quite careful about that, but gave me pointers to where to make changes and said he had mapped these throttle bodies before, on a similar engine, with good results.

What attracted me to these was not the taper but that the fact that the injectors are positioned underneath (the photo is the underside) and they are also well up the induction path. The roller barrels use injectors mounted in the head. That's OK for small injectors (and gives a good response in the OME engine), but with the larger injectors needed for this engine, the fuel does not mix so well and washes through at low induction velocities. Second reason was the induction length is slightly longer and better suited to the power band I intend to use. The inverted injector means gravity is working with you.

On the SBD engines this setup is now delivering 315BHP - but, as Simon says, time on the dyno is what is really making the difference.

[Scotty C]

oooo that gearbox, should be good for at least a second or 2 round KH

[David]

Well, now my season has ended, it's time to report the end result.

Following the mapping at Northamptom Motorsport, it has ran faultlessly the whole season. It delivered 4 x SLS class wins, SLS Class Championship, 2nd overall in the 'King of the Hill' championship, and I now hold SLS class lap records in both directions at KH. A few trackdays thrown in too, so which ever way you look at it, the investment of both time and money paid off. I'm also pleased with reliability with no failures which, in the perspective of the championship, was every bit as important as good times.

http://superlapscotland.co.uk/championship.htm


The main issues I had were with tyres. The rear wheel slip just ruined tyres - the ZZR didn't even get to the markers before the heat cycles turned them to plastic. I ended up using the the soft compound Kumho V70 as they were the only tyre able to keep traction and let me compete with the big power 4WD cars. But they're done in less than a 100 miles.

So now the target is to get my 55 second laps down to keep ahead of the competition next year.

[Shug]

Bloody well done David.

The classic story of a little investment in money and a lot of investment in time and effort bringing just rewards.

[tut]

Great results David, especially to come 2nd overall.

Charlie already had it won with 6 x 65 points, so you would have to get 4 x 65 in your own Class to match him.

tut

[David]

Great results David, especially to come 2nd overall.

Charlie already had it won with 6 x 65 points, so you would have to get 4 x 65 in your own Class to match him.

tut

The dropped point rule (used when there is a tie) meant I'd never catch him as I had two 2nd places. But to be honest, I'm more than happy to be number two to Charlie - it far exceeded my expectations of what was possible. It does show that the principle of power-to-weight is a leveller - but there are a few questions about Class structure and plans are in place to widen the top classes next year.