Sigma Engine Options
Discussion
Somewhat predictably, after a weekend hire of a Caterham (Sigma 125) I'm now looking to buy one.
I can see that the Sigma unit currently comes in 125 & 140 BHP flavours and in the past there was a 150 BHP option. Are there any significant differences between the characteristics of these that I should be aware of? Specifically:
- do you loose / gain more of the pops & bangs from the exhaust which the 125 delivered (much to my amusement)?
- are there any drivability considerations between these?
- are there any reliability issues associated with the 'higher' states of tune & why did Caterham cease to offer the 150?
- I know the 140 increases the limiter to 7k and change; does this make a difference in the 'real world' and does the 150 also feature the increased limit?
It will be predominantly used on roads with a couple of track days a year. Beyond the typical more power = better, what engine tune would you spec & why?
Thanks for any insight you can provide!
I can see that the Sigma unit currently comes in 125 & 140 BHP flavours and in the past there was a 150 BHP option. Are there any significant differences between the characteristics of these that I should be aware of? Specifically:
- do you loose / gain more of the pops & bangs from the exhaust which the 125 delivered (much to my amusement)?
- are there any drivability considerations between these?
- are there any reliability issues associated with the 'higher' states of tune & why did Caterham cease to offer the 150?
- I know the 140 increases the limiter to 7k and change; does this make a difference in the 'real world' and does the 150 also feature the increased limit?
It will be predominantly used on roads with a couple of track days a year. Beyond the typical more power = better, what engine tune would you spec & why?
Thanks for any insight you can provide!
Not sure but I think there were driveability issues with the 150 so they stuck with the 140, also I don't think they ever made 150 bhp. Best people to talk to are these - http://www.premierpowerengines.com/index they have done some fantastic development work on the Sigma, see if you can get to their open day at the end of the month.
As I understand it, the 150 was new camshafts with individual throttle bodies and a remap.
There were a lot of problems with the 150 throttle response and warming up. There is a very long thread on Blatchat about it.
The 140 is new cams, remap, lightened flywheel, and stronger valve springs and modified timing belt tensioner to allow higher revs.
The 125 is a great engine for road use with excellent torque spread, but it has given its best by about 6200rpm.
From what I have heard the 140 is a really nice engine but there have been a couple of reports of it not wanting to idle when cold, and with the new cam profiles the lower range torque must be a little less.
I have a 125 and love it, another 15bhp would be nice but not at £2000 plus!
There were a lot of problems with the 150 throttle response and warming up. There is a very long thread on Blatchat about it.
The 140 is new cams, remap, lightened flywheel, and stronger valve springs and modified timing belt tensioner to allow higher revs.
The 125 is a great engine for road use with excellent torque spread, but it has given its best by about 6200rpm.
From what I have heard the 140 is a really nice engine but there have been a couple of reports of it not wanting to idle when cold, and with the new cam profiles the lower range torque must be a little less.
I have a 125 and love it, another 15bhp would be nice but not at £2000 plus!
I've had my 125 for 7 years and love it. The only time I wish I hard more power is when I'm out with other 7's.
I may upgrade at some point but have being saying that for a number of years. I don't think 15 bhp is enough of a jump.
Premier Power and their 155 or 175 options look the better bet...
I may upgrade at some point but have being saying that for a number of years. I don't think 15 bhp is enough of a jump.
Premier Power and their 155 or 175 options look the better bet...
TheHoof said:
Somewhat predictably, after a weekend hire of a Caterham (Sigma 125) I'm now looking to buy one.
I can see that the Sigma unit currently comes in 125 & 140 BHP flavours and in the past there was a 150 BHP option. Are there any significant differences between the characteristics of these that I should be aware of? Specifically:
- do you loose / gain more of the pops & bangs from the exhaust which the 125 delivered (much to my amusement)?
- are there any drivability considerations between these?
- are there any reliability issues associated with the 'higher' states of tune & why did Caterham cease to offer the 150?
- I know the 140 increases the limiter to 7k and change; does this make a difference in the 'real world' and does the 150 also feature the increased limit?
It will be predominantly used on roads with a couple of track days a year. Beyond the typical more power = better, what engine tune would you spec & why?
Thanks for any insight you can provide!
Like you, I hired a Sigma 125 before getting the bug, and then started looking for one. I ended up getting lucky and found a Roadsport 140 matching the exact spec I was looking for and bought it a month after the hire day.I can see that the Sigma unit currently comes in 125 & 140 BHP flavours and in the past there was a 150 BHP option. Are there any significant differences between the characteristics of these that I should be aware of? Specifically:
- do you loose / gain more of the pops & bangs from the exhaust which the 125 delivered (much to my amusement)?
- are there any drivability considerations between these?
- are there any reliability issues associated with the 'higher' states of tune & why did Caterham cease to offer the 150?
- I know the 140 increases the limiter to 7k and change; does this make a difference in the 'real world' and does the 150 also feature the increased limit?
It will be predominantly used on roads with a couple of track days a year. Beyond the typical more power = better, what engine tune would you spec & why?
Thanks for any insight you can provide!
I didn't notice any loss of torque in the 140 over the 125, but it's noticeably got more poke in the high end. The 140 doesn't pop and bang as much as the 125 sadly, though as the mileage on mine has increased (up over 18k now) it has started to pop more when coasting, but it's definitely not the sort of engine that pops on gearchanges. It does sound fantastic when you rev it out though!
On the road it's fantastic. It's very smooth, lots of pull in every gear. Mine's a 6-speed and can be a little tiresome on the motorway (4k rpm at 70 with the 13x6" CR500s), but once you get over that it's brilliant everywhere else. I'm sure the 5 speed would be excellent too, but the 6 is a perfect match for the car.
Power wise, it feels like a real sweet spot to me. You can really drive the nuts off it, and you feel like you've done all the work. On trackdays you'll be faster than pretty much everything in the braking and corners, but once you're about 70, the aerodynamics take over and you'll be at a disadvantage. Having owned it for 2 years, as much as a little extra power would be nice, I wouldn't want to ruin the balance it has at the moment. You have to really learn to drive to get around tracks quickly, and I feel like I've got so much more to learn before I'm making the most of the power I've got - so I'll be staying in 140 tune for quite some time. Keep in mind that a "standard" Caterham tune will hold it's value a little better than a modified one - and if you do decide you want more power, it's probably more cost effective to just buy a faster car.
I've had no real issues with the engine. It did have a few problems idling when I first bought it, but after some new plugs and a throttle breather adjustment it's been absolutely fine.
In fact, the only problem I've had was yesterday when I filled the car up with petrol and it wouldn't start - flat battery! It hadn't been used for a month, and had been on a battery conditioner the whole time. But the power went off several weeks ago, and I fear the conditioner didn't go back into charge mode, thus leaving me with a flat battery! My fault for not checking often enough!
framerateuk said:
I didn't notice any loss of torque in the 140 over the 125, but it's noticeably got more poke in the high end. The 140 doesn't pop and bang as much as the 125 sadly, though as the mileage on mine has increased (up over 18k now) it has started to pop more when coasting, but it's definitely not the sort of engine that pops on gearchanges. It does sound fantastic when you rev it out though!
I also have a 140 (Supersport) and spent a weekend test driving the 125. The extra power is noticeable, with better pull above 5000rpm along with the raised rev limit (7200rpm). I noticed no drop-off in torque at all; it's a torquey little motor!My 140 pops and bangs a treat (see here: https://www.youtube.com/watch?v=kBie7Tt6zQY), however I have the pea shooter exhaust which I don't believe Andy has? Oh and mine also pops when changing gear at 7000rpm
ghibbett said:
My 140 pops and bangs a treat (see here: https://www.youtube.com/watch?v=kBie7Tt6zQY), however I have the pea shooter exhaust which I don't believe Andy has? Oh and mine also pops when changing gear at 7000rpm
Yeah I've got the Roadsport exhaust. Sounds the same as yours in the video, but definitely quieter. I'd be afraid of going over track noise limits on the peashooter, it's already bloody loud as it is! 
https://www.youtube.com/watch?v=-gC9paHdIrY
Grubbster said:
Not sure but I think there were driveability issues with the 150 so they stuck with the 140, also I don't think they ever made 150 bhp. Best people to talk to are these - http://www.premierpowerengines.com/index they have done some fantastic development work on the Sigma, see if you can get to their open day at the end of the month.
My Sigma 150 makes a healthy 151.7bhp and runs very nicely since the throttle bodies were set up properly by my friends at Premier Power. Please don't believe what you might hear about them being underpowered and or poor to drive in traffic etc. Mine is fine and I would recommend one to a new buyer looking for a little more power than a 125. Having said that, I would also recommend any of PP's engine upgrades too.Oli
I think the setup on the 150 was the issue more than anything.
I was out in mine last month and got chatting to a guy with a 150 and he mentioned his was very jumpy around town.
Also, as far as I know, Premier Power don't have another open day do they? They just haven't updated their site for nearly a year...
I was out in mine last month and got chatting to a guy with a 150 and he mentioned his was very jumpy around town.
Also, as far as I know, Premier Power don't have another open day do they? They just haven't updated their site for nearly a year...
Hi All,
Just to let you know Premier Power are not having an open day at the end of September. The front page of the website needs taking down.
We were planning an open day at the end of September but instead will be attending the Lotus7club track day at Hethel on the 28th of September. We do however plan to have another open day in the near future.
Happy motoring and enjoy what's left of the summer.
Regards
SKC
Just to let you know Premier Power are not having an open day at the end of September. The front page of the website needs taking down.
We were planning an open day at the end of September but instead will be attending the Lotus7club track day at Hethel on the 28th of September. We do however plan to have another open day in the near future.
Happy motoring and enjoy what's left of the summer.
Regards
SKC
My sigma 150 was a little tricky when pootling before I learnt how to balance the throttle bodies, which I do about every thousand miles. Pulls strongly from 4000 revs up to the soft limit at 7500, hard at 7600. Pops and bangs on overrun but only if being driven hard which is a good thing as they would get tiresome all the time. I actually wish the exhaust was quieter but love the induction roar from the throttle bodies!
Edited by RedCat7 on Tuesday 9th September 22:28
Thanks guys; that is helpful.
Can I check that I am correct in my understanding that the 'peashooter' exhaust is the standard exhaust rather than the caterham optional 'track day' exhaust which is offered on the Supersport & above?
My current thinking is a used Roadsport in either 125 or 140 flavour - probably 140. Am I safe assuming that given the lack of choice in the options list, a Roadsport in either tune isn't likely to cause problems with the noise limits at track days, and by inference, the Supersport is louder in 140 trim with the standard exhaust than the Roadsport 140?
Can I check that I am correct in my understanding that the 'peashooter' exhaust is the standard exhaust rather than the caterham optional 'track day' exhaust which is offered on the Supersport & above?
My current thinking is a used Roadsport in either 125 or 140 flavour - probably 140. Am I safe assuming that given the lack of choice in the options list, a Roadsport in either tune isn't likely to cause problems with the noise limits at track days, and by inference, the Supersport is louder in 140 trim with the standard exhaust than the Roadsport 140?
Edited by TheHoof on Tuesday 9th September 21:52
TheHoof said:
Can I check that I am in my understanding that the 'peashooter' exhaust is the standard exhaust rather than the caterham optional 'track day' exhaust which is offered on the Supersport & above?
The peashooter is standard on the Supersport, but the trackday exhaust is an optional extra. I'm not sure what exhaust comes with the 140 at the moment (it's changed since mine), but it certainly wouldn't be anywhere near as loud as the peashooter (it might even be the same as the trackday exhaust - but you'll need to check). I've never been questioned over noise, but I've not been to Donington or Bedford where they're known to be very strict! Is still don't think it would be over the limits though.
There's no difference between the engines in the Roadsport 140 and the Supersport. You can pretty much spec the cars the same if you choose the right options. (Mine's actually more like the old Superlight 150 spec but with the 140 engine, even though it's a a Roadsport).
Edited by framerateuk on Wednesday 10th September 13:51
As previously mentioned, I have the pea shooter exhaust, however I also have a std Sigma can which I'll put on for any track days. With my pea shooter I would not even entertain turning up to a track day and chancing my hand with the noise limits. In fact I won't even drive it without ear plugs for fear of damaging my hearing.
It's great
It's great
Gassing Station | Caterham | Top of Page | What's New | My Stuff