Nice light engine in a ROAD Seven.
Discussion
Hey all.
I've decided to build myself a Seven for nipping 'round the lanes and fancied doing a Crossflow..largely for 'character' reasons.
However, I feel I should drag myself kicking and screaming into the modern world and having done a degree of research on the subject I quite like the idea of either the Rover 'K' or the Ford Sigma.
Does anyone with experience of either engine (particularly the Sigma)in a Seven fancy sharing their wisdom?
Any similar engines I should be looking at?
I've decided to build myself a Seven for nipping 'round the lanes and fancied doing a Crossflow..largely for 'character' reasons.
However, I feel I should drag myself kicking and screaming into the modern world and having done a degree of research on the subject I quite like the idea of either the Rover 'K' or the Ford Sigma.
Does anyone with experience of either engine (particularly the Sigma)in a Seven fancy sharing their wisdom?
Any similar engines I should be looking at?
First, may I say what a commendably sensible approach you have: discussion over 'Seven' engines on these forums tends to diverge to the extremes of either badly geared and fragile screamers from bikes or 250bhp+ monster car engines, chasing power:weight ratios that are effectively unusable on the road.
The engines you are looking at both fall into the 'sweet spot' of reasonably light weight matched with reasonably good power, torque and reliability...
I've no real experience of the Sigma, but my understanding is that the main limitation at present is tuning potential. You can take it to about 160bhp (which is admittedly plenty for a lightweight, road-gong Seven), but it's quite expenssive to do so, compared to the K-series. For example the packages I've seen for the Sigma suggest that you need individual throttle bodies for 160bhp, whereas the K-series can manage that sort of power and a little more on the standard single thottle body, and if you do become power crazed, then the ultimate limit on a K-series is 230bhp+, which is probably way beyond what will ever be achieved for the Sigma.
So, the K-series is just as light, more readily available, has better tuning back-up BUT is an older unit and has the well known (albeit solvable) issue with the head gasket.
I do have reasonable experience of the K-series (in both Sevens - including my current Westfield which runs a K-series tuned for around 175bhp on a single throttle body - and Elises) and can say that it's a very nice engine. I've yet to suffer head gasket problems, either, though I have friends with Elises who haven't been so lucky.
I also have a lot of experience with Crossflows (including a circa 155bhp spec. engine in my current Sylva). As you say, they are a couple of generations behind the Sigma/K-series, but I still wouldn't rule them out for entirely for a road going Seven, particularly since you quote 'character' as being of importance. The big disadvantage of the modern 16-valves is that they are very characterless in comparison; the power output and torque curve is so linear and smooth that they feel almost gutless; very much 'white goods' in comparison to the older, carburetted 2-valve engines and you do miss the snorting Webers and the smell of petrol and oil fumes from the breathers when you're driving something with an injected 16-valve.
Downsides with the Crossflow, of course, are that the fuel consumption is abysmal (count on low 20's mpg with a highly tuned Crossflow on Webers, even in a Seven), they are noise little beggars (which can give problems if you are planning track days), getting quite expensive to tune, and realistic power output on a really good road-driveable unit is around the same as the Sigma's current 160bhp limit. And they probably carry a 25 kilo weight penalty compared to the K-series (I weighed my Crossflow at 109 kilos dead, with clutch, wet sump, inlet manifold and twin webers, last time it was out of the car)...
The other obvious engines to look at are the Ford Zetec & Duratec, and the Toyota 16 valve (promoted by RAW, for Seven use), but they're a step up in terms of weight and bulk from the K-series and Sigma.
The engines you are looking at both fall into the 'sweet spot' of reasonably light weight matched with reasonably good power, torque and reliability...
I've no real experience of the Sigma, but my understanding is that the main limitation at present is tuning potential. You can take it to about 160bhp (which is admittedly plenty for a lightweight, road-gong Seven), but it's quite expenssive to do so, compared to the K-series. For example the packages I've seen for the Sigma suggest that you need individual throttle bodies for 160bhp, whereas the K-series can manage that sort of power and a little more on the standard single thottle body, and if you do become power crazed, then the ultimate limit on a K-series is 230bhp+, which is probably way beyond what will ever be achieved for the Sigma.
So, the K-series is just as light, more readily available, has better tuning back-up BUT is an older unit and has the well known (albeit solvable) issue with the head gasket.
I do have reasonable experience of the K-series (in both Sevens - including my current Westfield which runs a K-series tuned for around 175bhp on a single throttle body - and Elises) and can say that it's a very nice engine. I've yet to suffer head gasket problems, either, though I have friends with Elises who haven't been so lucky.
I also have a lot of experience with Crossflows (including a circa 155bhp spec. engine in my current Sylva). As you say, they are a couple of generations behind the Sigma/K-series, but I still wouldn't rule them out for entirely for a road going Seven, particularly since you quote 'character' as being of importance. The big disadvantage of the modern 16-valves is that they are very characterless in comparison; the power output and torque curve is so linear and smooth that they feel almost gutless; very much 'white goods' in comparison to the older, carburetted 2-valve engines and you do miss the snorting Webers and the smell of petrol and oil fumes from the breathers when you're driving something with an injected 16-valve.
Downsides with the Crossflow, of course, are that the fuel consumption is abysmal (count on low 20's mpg with a highly tuned Crossflow on Webers, even in a Seven), they are noise little beggars (which can give problems if you are planning track days), getting quite expensive to tune, and realistic power output on a really good road-driveable unit is around the same as the Sigma's current 160bhp limit. And they probably carry a 25 kilo weight penalty compared to the K-series (I weighed my Crossflow at 109 kilos dead, with clutch, wet sump, inlet manifold and twin webers, last time it was out of the car)...
The other obvious engines to look at are the Ford Zetec & Duratec, and the Toyota 16 valve (promoted by RAW, for Seven use), but they're a step up in terms of weight and bulk from the K-series and Sigma.
Sam_68 said:
or 250bhp+ monster car engines, chasing power:weight ratios that are effectively unusable on the road.
No sorry can't agree. Used to give my 300bhp Seven the full beans regularly. The accessability of the performence was such that my lawyer once described the car as "more intoxicating than crack". Sometimes it all goees wrong. The death of my car was an accidnent which occurred at 60% of the posted speed limit.
In answer to the OP however, the best engine for a Seven (and this is what I will use when I (re)build a basket case Caterham into my next Seven) is a stock 1800 K series, with supersport cams, a very light flywheel and throttle bodies. Good for 170bhp, economical, reliable and £300 for a new engine if you lunch it.
Clsoely followed by a BEC which is a better drive, but at the expense of refinement.
Edited by EFA on Saturday 31st July 21:51
Thanks for taking the time, Sam.
I haven't ruled the crossflow out completely, but the fuel consumption and maybe the lure of more reliable fueling has turned my head.
I'm told that the Sigma requires less revving to extract it's power than the 'k', which is more attractive.
Research tells me that the head gasket of the 'k' is a little more scare story and bad maintenance than anything else.
I haven't ruled the crossflow out completely, but the fuel consumption and maybe the lure of more reliable fueling has turned my head.
I'm told that the Sigma requires less revving to extract it's power than the 'k', which is more attractive.
Research tells me that the head gasket of the 'k' is a little more scare story and bad maintenance than anything else.
Don't have any experience / knowledge of the Sigma. Do know a little about the K. The well known head gasket issue, is usually a problem with rear engined cars and the Freelander. This is due to cooling issues. In a Seven type, it's easy to arrange a proper cooling system and the problem is much less common.
The K series is very sensitive to over heating, the trick for long life is to never thrash it from cold (even with no load) and to put the thermostat on the hot side of the engine, i.e. the water outlet.
It's light, cheap to tune and readily available. A good friend of mine had the misfortune to write off a crossflow Caterham. He replaced it with a K series Caterham, which according to the specs was about the same weight and about the same power. He was amazed at the difference the K series made. Much more nimble due to lower weight and better drivability due to broader power/torque curves.
Twin Webbers on an old iron engine like the crossflow or the VX will always sound nicer to me, but in a Seven, a light engine is a much better choice.
The K series is very sensitive to over heating, the trick for long life is to never thrash it from cold (even with no load) and to put the thermostat on the hot side of the engine, i.e. the water outlet.
It's light, cheap to tune and readily available. A good friend of mine had the misfortune to write off a crossflow Caterham. He replaced it with a K series Caterham, which according to the specs was about the same weight and about the same power. He was amazed at the difference the K series made. Much more nimble due to lower weight and better drivability due to broader power/torque curves.
Twin Webbers on an old iron engine like the crossflow or the VX will always sound nicer to me, but in a Seven, a light engine is a much better choice.
XanderH said:
I haven't ruled the crossflow out completely, but the fuel consumption and maybe the lure of more reliable fueling has turned my head.
The fuel consumption is more to do with the fact that a crossflow will probably be fitted with Weber 45s. Why not keep the crossflow but upgrade the fuelling and spark to the same as the Sigma/K Series? Twin throttle body injection and full 3D mappable fuel injection and spark would more than likely give you much better drivability accross the entire rev range and maybe cut down on fuel consumption since the fuel can be metered to suit every second of driving rather than a Weber hosepipe. (And before anyone flames me, my XI runs a Weber 45) Yes a Weber can be properly set up on a rolling road but it can never be as effective as properly mapped injection.MKnight702 said:
Why not keep the crossflow but upgrade the fuelling and spark to the same as the Sigma/K Series?
.Arguably that would give you the worst of all worlds, though? An engine that's heavier, less powerful, shorter lifespan and more expensive to build than an equivalent K-series, whilst removing much of the character that you get with a carburettored engine...
jason61c said:
why not just fit a ford 2.0 duratec, they're light and about 150bhp standard if that's all you're after.
After speaking to the bloke at Power Torque at the Stoneleigh show, the Duratec is only 15kg lighter than the Zetec, hardly worth the additional cost in my book unless you'e going to fit cams, throttle bodies and a blower. The main problem if you want lightweight if the standard gearbox option though.Another lightweight option is a Suzuki swift egine mated with a Jimny gearbox. A friend of mine has one in a Fury with bike carbs and it performs really well
Stubby Pete said:
jason61c said:
why not just fit a ford 2.0 duratec, they're light and about 150bhp standard if that's all you're after.
After speaking to the bloke at Power Torque at the Stoneleigh show, the Duratec is only 15kg lighter than the Zetec, hardly worth the additional cost in my book unless you'e going to fit cams, throttle bodies and a blower. The main problem if you want lightweight if the standard gearbox option though.Another lightweight option is a Suzuki swift egine mated with a Jimny gearbox. A friend of mine has one in a Fury with bike carbs and it performs really well
andygtt said:
Stubby Pete said:
jason61c said:
why not just fit a ford 2.0 duratec, they're light and about 150bhp standard if that's all you're after.
After speaking to the bloke at Power Torque at the Stoneleigh show, the Duratec is only 15kg lighter than the Zetec, hardly worth the additional cost in my book unless you'e going to fit cams, throttle bodies and a blower. The main problem if you want lightweight if the standard gearbox option though.Another lightweight option is a Suzuki swift egine mated with a Jimny gearbox. A friend of mine has one in a Fury with bike carbs and it performs really well
jason61c said:
Thats something most people don't think about is the weight of the gearbox, I know the bmw gearbox's are light.
Whilst keeping overall weight down is highly commendable, you've got to remember that on a 'Seven' the gearbox sits very close to the CoG, so it has minimal effect on the polar moment and the car's handling.It would be rather misguided to select a huge boat-anchor of an engine on the basis that it has a light gearbox attached to compensate, 'cos it's the engne that sits out at the front of the dumb-bell and has the big influence on the car's behaviour...
There are, of course, all manner of lightweight casings and bellhousings available for Ford boxes, if you're obsessive, not to mention gearsets that offer much more sensible ratios than the tall, overdriven 5th gears that you find on modern saloon car boxes,
There was an article in TotalKitCar Magazine a couple of copies ago on the weights of the Ford engines and they varied between high 80Kg and about 120Kg if I recall correctly, the older ones being the heavier of course.
Read quite a few comments about "boat anchors" "light engines" but other than the TKC article I've not really seen any reference data to what the weights are and what components are included ?
I know from work I've done in stripping weight from BMWs that the std BMW M3 engine will be about 140-150Kg all in, the 4 cyl BMW's even 20 year old ones are about 100Kg and that the newer engines are of course lighter.
Perhaps to help the questioner and future questions about engine weights if people know of reference material on a particular engine they could reference it ?
Obviously a lot more influences the handling and driving experience than pure weight of the engine, but as the question is about weight perhaps you should consider power and get a light engine and gearbox and then FI it ?
Read quite a few comments about "boat anchors" "light engines" but other than the TKC article I've not really seen any reference data to what the weights are and what components are included ?
I know from work I've done in stripping weight from BMWs that the std BMW M3 engine will be about 140-150Kg all in, the 4 cyl BMW's even 20 year old ones are about 100Kg and that the newer engines are of course lighter.
Perhaps to help the questioner and future questions about engine weights if people know of reference material on a particular engine they could reference it ?
Obviously a lot more influences the handling and driving experience than pure weight of the engine, but as the question is about weight perhaps you should consider power and get a light engine and gearbox and then FI it ?
The K and the Sigma are the two I'd be looking at.
I haven't driven a Sigma engined kit, but I've heard good things about them from the Caterham camp.
My Caterham has the Supersport spec 1.6 K-Series and it's a peach. Surprisingly tractable (25mph in top through towns), extremely responsive and very revvy. It's a light engine, which suits Sevens well and performance is good. It's largely standard Rover fayre barring a remap and a lightened flywheel, which makes 140bhp from 1600cc pretty respectable and you can tune them to well over 200bhp.
I haven't driven a Sigma engined kit, but I've heard good things about them from the Caterham camp.
My Caterham has the Supersport spec 1.6 K-Series and it's a peach. Surprisingly tractable (25mph in top through towns), extremely responsive and very revvy. It's a light engine, which suits Sevens well and performance is good. It's largely standard Rover fayre barring a remap and a lightened flywheel, which makes 140bhp from 1600cc pretty respectable and you can tune them to well over 200bhp.
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