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Tuesday, November 30, 2010
Thinking Inside The Box
| I popped briefly out into the garage this evening to pop the lid off the gearbox for a peer to try to gauge that it all looked and seemed to be working ok. After re-attaching the gear lever, I eventually worked out that I could find all the gears, although it is far easier to find reverse rather than the first-second gear plane. I guess there is some sort of problem with the detent mechanism which should mean you have to push the lever down to move the lever past the first-second plane, into the reverse plane. After half an hour in the garage my fingertips were numb from the cold, so that investigation can wait for another day. |
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Monday, November 01, 2010
Engine Choice
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After a load of thinking and researching, I have reached a decision
on the choice of engine. As much as I would love a 5-cylinder, I don't think it is a realistic option really in terms of cost, and, having seen how the bonnet line of the Stylus causes issues with even the Vauxhall, physical size and weight. Unfortunately, the same argument goes for the F20 VTEC engine, and the B16 is not at all straight forward to use in a rear-drive configuration. The Zetec is certainly cheap, plentiful, and can easily produce enough power quiet easily, but it is a bit of an old and heavy design of engine, with an iron block. More recent engines are better. The Duratec is the obvious more modern alternative, but it is physcially slightly large, and I am somewhat worried about what I will be able to fit under the bonnet (as I want to get rid of that horrible bulge), and seems to be a bit more expensive to tune it. So that leaves a K-series or Sigma. I was fairly sure that I was going to go with the K, as I sort of know a bit more about it, some of it's issues, and how to overcome them. But the more I looked into the Sigma, the more it made sense. Physically it is very similar to the K, in terms of dimensions and weight (~80kgs). What the Sigma has in it's favour, is none of the problems that the K has! Yes, they can be worked around, but that all costs money, so why do that if you don't have to? The Sigma can be revved to 8000rpm with only a change of big end bolts and valve springs, everything else stock. It is simple to get to ~160bhp with just an exhaust, ECU, and throttle bodies, and nearer 200bhp can be achieved with the increased revs, some mild headwork and upgraded cams. All from a 1600 which is plentiful and you can buy from a scrapper for £400. |
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From what I can see, there isn't alot of choice of gearbox, for a
front-engine rear-drive configuration, with the Sigma engine. In
standard use by Ford, it is a transverse front wheel drive engine,
and as such has a gearbox for this purpose (known as the IB5).
Obviously, this is no good for rear wheel drive though when you
rotate the engine around into a longitudonal mounting. Previously,
there was alot of commonality between Ford engines and gearboxes,
and in the good old days, there a few different vehicles with rear
wheel drive, so you could bolt up a number of different gearboxes to
engines. |
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So, for the Sigma, there are a few companies around who will sell me
a bellhousing to connect a Ford Type 9 gearbox. The Type9 was Fords
first RWD 5-speed box, and was used in the Capri and Sierra (and few
other things). As it has a separate bellhousing and can therefore be
mated to all sorts of different engines, it is a popular choice for
kits and conversions. It is still relatively available, and fairly
cheap, though as Sierras are becoming a bit more scarce, I'm sure
that will change. There is also a thriving aftermarket for these
boxes, so parts and upgrades are readily available. The ratios in
the standard box are not ideal for a light car - well first gear is
way too short really - but that can be lived with and tuned using
the diff ratio to an extent. Ultimately, putting a nicer aftermarket Type9 box in will be a good plan, but for starters, a standard box will do just fine. |
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Speaking of diffs, it is my intention to replace the live axle on
the car (currently sporting huge spacers to widen the track) with a
home-brew independant rear suspension setup. Sounds scary, but in
essence what you need to do is build a diff cage hanging off the
back of the tunnel / rear bulkhead, and from that you can hang
double-wishbones. Now there is a little more science to it than that
to get the strength and geometry right, but it can't be too hard,
can it...? As such, a diff also needs to be chosen, and again the most widely used in kit car circles is from a Ford Sierra. There are other, more modern choices around, but the Sierra unit is well known, cheap, a range of ratios, and again there is decent availablility and an aftermarket for it. Also, rather conveniently, Richard (my next door neighbour) has a limited-slip version sitting forlornly in the corner of his garage, after he upgraded his to a different ratio by changing the whole thing. |
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| So there we go, 1600 Sigma engine, through a Type9 gearbox, to a Sierra diff. Done (hopefully). |