Sigma 150 vs K-series?

[Mostro]

So I'm looking at Caterhams in the 140-175bhp range (ish) and have only really considered the various K-series variants to date - I guess R300 would be the ideal on paper.

However, Sigma 150s are now appearing within my budget (& the odd 140 Supersport) - how do they compare for performance and character? I'm not really interested in tuneability (I don't think...) and there's a certain appeal to a newer, more modern powerplant to a first-time and not particularly mechanically-minded owner.

I'd be very interested to hear thoughts of people who have driven either or both on their respective character, drivability and reliability. Should I consider a Sigma, even if the exhaust is on the wrong side?!

cheers

[Smollet]

I've got a Sigma 150 and even if it doesn't deliver 150 bhp it is an enjoyable car to drive with plenty of torque all the way through the rev range. The exhaust is on the correct side. You can hear it far better than you would a k series.
Also I've not heard any stories re reliability which can be a problem with some k series. Having said all this I wish the 175 Duratec had been an option when I bought the car from new. The Sigma 125 also has a good reputation as being more driveable than the 150 which can be a bit jerky with a light throttle.

[Grubbster]

I have one of each, probably a bit unfair to compare them too much (230 bhp and 125 bhp Sigma) but I used to have a 140 K so reasonably experienced in the differences. The K is a more revvy engine, I like it a lot - the way the power is delivered a bit higher up the rev range. The Sigma seems more torquey, you can hold a gear lower down the revs and still pull quite cleanly without the need to change down so much - but it lacks the top end fizz at the upper reaches of the revs so no need to take it to the limiter. The 140/50 might be a bit different. I've not heard of many problems with the Sigmas whereas the K's have a [somewhat unfair] reputation for being unreliable - I have almost 30,000 K miles which have been pretty much incident free, even with the 230 bhp engine running to 8500+ rpm I don't have many issues.

Sigma tuning is starting to become more popular now, so I'd imagine a 180 bhp Sigma will be readily achievable, this could be a lovely option but I've not experienced one. If you want a nice drivable 7 for road and track then personally a K series of about 160 - 170 bhp would be hard to beat in my opinion. More than this and it starts being a bit silly as a road car if you try using it (mine hardly goes on the road these days).

[coppice]

If you are in L7C there is an article by Phil Morris about upgrading Sigmas to 200bhp in this month's Low Flying.

[HustleRussell]

In my opinion (have driven Sigma 125, K-series super sport, R300 Duratec), the K-series feels the most 'racy' and characterful because of the way they rev. The Ford engines are less dramatic, but dare I say more robust- particularly the Dura-nail. That's not to say the K-series is 'un-reliable' as such, you just have to expect that if the head gasket hasn't been properly sorted at some point it'll probably let go at some point in the future. If I wanted a 175bhp Caterham, though, it'd be hard for me to look past the Duratec.

[EFA]

Smollet, A sigma puts the exhaust on the same side as an old Pinto powered Westfield does it not??

The K may have its faults, but failures are less common now older cars have had updates applied. Only if you thrash from cold are you likely to get HGF issues.

[Smollet]

EFA said:

Smollet, A sigma puts the exhaust on the same side as an old Pinto powered Westfield does it not??

The K may have its faults, but failures are less common now older cars have had updates applied. Only if you thrash from cold are you likely to get HGF issues.

I wouldn't know about the Pinto engined Westfield but the exhaust is on the drivers side same as the Duratec.

[Steffan]

HustleRussell said:

In my opinion (have driven Sigma 125, K-series super sport, R300 Duratec), the K-series feels the most 'racy' and characterful because of the way they rev. The Ford engines are less dramatic, but dare I say more robust- particularly the Dura-nail. That's not to say the K-series is 'un-reliable' as such, you just have to expect that if the head gasket hasn't been properly sorted at some point it'll probably let go at some point in the future. If I wanted a 175bhp Caterham, though, it'd be hard for me to look past the Duratec.

The K series (I own three cars with this engine and have owned many more) is a classic example of a brilliant high revving engine which is inherently fragile. Not unlike the old 1622 CC MGA Twin Can engine which was totally unreliable but in tuned form held the world speed record for many years in its suoercharged form.

The K series will outperform all other current engines particularly in performance racing. All the Racing mechanics I know will testify that for absolute power and free revving performance the K series is the business. Buit it is inherently fragile and therefore requires all the right components (uprated waterpump and thermostat and latest gasket etc etc) and even then it will suddenly let go.

I think I would fit the Duratec unless racing the car because on the road, help can be a ball ache in arriving.

[EFA]

but the exhaust is on the drivers side same as the Duratec

[Smollet]

Steffan , the MGA twin cam was 1588 cc. The 1622 cc engine was the B series push rod ohv unit which was very reliable.

[Steffan]

Smollet said:

Steffan , the MGA twin cam was 1588 cc. The 1622 cc engine was the B series push rod ohv unit which was very reliable.

Quite right a temporary brainstorm. Sign of senility no doubt. The Twin Cam was 1588 I should know I owned two in the 1960's both melted the pistons etc but I wish I had them now. I think Gerald Palmer had a hand in the design certainly Leonard Lord fired him for the failures and warranty claims. Thanks for the correction.