125 sigma power upgrade

[Jools Powell]

Looking for my first Caterham and the cars I like the look of and are in my budget range are all 125bhp. I feel that really I want a 140. What is the most cost effective way to get the car upgraded. There's also the fact I'm way down in Cornwall so getting the car to a tuner it's always going to be a pain.

[DirtBuddha]

To answer your question: 

You'd need new cams, ECU and remap to upgrade the 125 Sigma to 270 spec... cost is circa £3k-£4k. 

However, it would be better to buy the right car in the first place.... and I may soon be selling my 140bhp 1.6 K Series and at £16,250 it will be quite a bit cheaper than a vanilla spec 125bhp Sigma plus costly upgrades.

 

Also - I'm in West Sussex, so the South 🙂 

 

 

2005 1.6 K Series SuperSport - factory built car. 

 

Engine

1.6 EU3 K Series with forged pistons, SuperSport cams, solid lifters, VVC manifold and larger 52mm throttle body

Uprated (later type) lower oil rail, uprated 10.9 through bolts, new Payen head gasket (DVA’s preferred choice)

Dry sump (genuine Caterham ‘gold pump’ dry sump) - just been serviced by Titan

TTV lightweight flywheel (3.14kgs vs 7.2kgs standard)

ARP flywheel bolts

 

 

 

Cooling

New Radtec radiator

New alloy submarine

Silicone hoses throughout

Mikalor clamps throughout

 

 

Gearbox/drivetrain

New 5 speed gearbox

New paddle clutch & cover

PGM uprated clutch fork

Uprated CRB

Titan LSD (3.92)

 

 

 

Suspension

Wide track suspension

Bilstein adjustable coilovers (M2 rear and M0 front)

Uprated springs (250 front / 215 rear)

 

 

 

Body/Interior

Tillett seats

New TRS 6 point + 4 point harnesses

Caterham 6+8 inch Apollo’s with Toyo R88R

SLR cage

LED lights all round

Quick-release Momo wheel

Meteor Motorsport clear aeroscreen

Stack oil pressure gauge

New carbon vinyl boot cover (SoftBitsForSevens)

New carbon cycle wings & rear arches

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited August 2 by DirtBuddha

[paul_w]

Hi Jools

I was able to do this conversion pretty cheaply as I got some parts from someone who was upgrading their low mileage Supersport (to the Premier Power 190 conversion) and I also found a set of the cams second hand. But it was still about £2500, though that includes labour as Sevens and Classics did the work. It felt much better than just an extra 15bhp would suggest, and I think a lot of that comes from the lighter flywheel - that came from TTV for £300, so if you can do the work to pull the engine out yourself it would be a pretty cost-effective upgrade to just swap the flywheel and nothing else.

But it's true is that it's always cheaper to buy a car that's already done than spend out on upgrades yourself. I certainly didn't get my money back when I sold the car.

Have you driven a 125 bhp car? My first 7 only had 100bhp and it was by no means slow compared to normal cars, and was a great tool for improving my driving which is the main thing that makes you quick in a 7. My S1 only has about 40bhp and is still lots of fun, despite being out accelerated by almost every other car on the road!

Paul

[Jools Powell]

Yes, I've not driven a 125 only a hired 360 so I thought it might feel a little lethargic with two and luggage. Also I was thinking of going for a SV which heavier as well.

[StevehS3]

I wouldn’t rule out a 125hp seven. I did loads of road/touring and some track days in my 120hp K and loved it - the Sigma has a bit more power and I expect more torque. Nice and light too. I would say try one at a local club meeting. 

[Ainsley]

Don't forget, they all go round corners at the same speed whatever the bhp 🙂

[Jonathan Kay]

If I had a Sigma I would have been very interested in the Premium Power modifications because of what owners have said about how they improve the pleasure of driving rather than any increase in power. See also lightened flywheels.

Is anyone else offering anything similar to that?

Failing that I'd spend the money on tuition.

Jonathan

[mso]

I think there is possibly some confusion here between the 270 upgrade and 310.  Last time i looked the parts-only price of the 270 upgrade (ecu flash plus spark plugs) was £295 - up from 125bhp to 135bhp, so total price should be a few hundred.    Cams and lightened flywheel are for the 310 upgrade, which then takes it up to 155 bhp

 

 

[Jools Powell]

5 hours ago, mso said:

I think there is possibly some confusion here between the 270 upgrade and 310.  Last time i looked the parts-only price of the 270 upgrade (ecu flash plus spark plugs) was £295 - up from 125bhp to 135bhp, so total price should be a few hundred.    Cams and lightened flywheel are for the 310 upgrade, which then takes it up to 155 bhp

 

 

Well that doesn't sound so bad.

[BigCol]

Am pretty sure the 125bhp engine has a fixed cam whereas the 310 is based on the variable cam Sigma.

Stand to be corrected… 🤷🏻‍♂️

[mso]

good point - it depends on the age of the engine doesnt it ?  I think the 125bhp engines are variable cam from about 2015,  a bit earlier for academy cars

  

[olly]

My 2021 ex-Academy car with 125bhp has variable cams.

[paul_w]

I had assumed fixed cam as 140bhp is the fixed cam Supersport spec and because Jools mentioned budget so I guessed we're talking about the older Sigma cars.

A 310 is a similar upgrade package added to the variable cam engine to get 152bhp.

None of the Sigma cars will have the torque of the 360 so would indeed be slower as an SV two up with luggage. There no replacement for displacement, as the Americans say.

But if it's what you can afford, I doubt you'd regret it if you just bought a standard 125bhp car. It still won't be slow, and will corner slightly better than a 360 of the same spec.

[Stewart Collier]

So just to clarify the post from Jools. Is the 125 to 135 upgrade only for the later VVT sigma engine? 

 

[StevehS3]

37 minutes ago, Stewart Collier said:

So just to clarify the post from Jools. Is the 125 to 135 upgrade only for the later VVT sigma engine? 

 

Yes. All other upgrades for either engine require new cams etc in addition so the ECU software. 

Rob made a video about the 125 to 135 Ti-VCT upgrade  https://youtu.be/OtplUw6ufpg?si=4MyblEITgz9ykE-I

[Stewart Collier]

Thank you Steve 👍

[Jools Powell]

Thanks for all the replies and in conclusion I feel the upgrade path is very expensive for small gains. Important if racing but for Sunday morning blats not so much.  Having fairly recently got my Peugeot Boxer CamperVan remapped adding 60BHP for £240 it leaves me wondering why in a Caterham the costs are so high but then I dont really know much about the black arts of engine tuning. 

[StevehS3]

Hi Jools, other than the 125 to 135 upgrade, the Caterham engines are already mapped [to the max?] so beyond that requires engine work which is expensive. 
You are right that buying a seven with the power and spec you want is likely to be the most economical path. 

Edited August 3 by StevehS3

[Andrew 21 Edney]

2 hours ago, Jools Powell said:

Having fairly recently got my Peugeot Boxer CamperVan remapped adding 60BHP for £240

I'm going to assume that you are talking about a turbo diesel engine in your camper van, so there will be different options when compared to a naturally aspirated petrol engine (especially if Caterham have already "picked the low hanging fruit" so to speak).

[150SV]

On 03/08/2024 at 15:32, Jools Powell said:

Thanks for all the replies and in conclusion I feel the upgrade path is very expensive for small gains. Important if racing but for Sunday morning blats not so much.  Having fairly recently got my Peugeot Boxer CamperVan remapped adding 60BHP for £240 it leaves me wondering why in a Caterham the costs are so high but then I dont really know much about the black arts of engine tuning. 

The Sigma is pretty high in tune before Caterham got hold of, gains get more expensive the higher you chase them.

The F175 from Premier was an approx 25hp gain for my 150, but still the thick end of £8k to have fitted.....

If you feel more power is the answer, Id look to buy a used F175 as someone has already taken the hit on that cost.

I may be worng, but IM not sure you can even buy the supersport 140 kit from Caterham now.

The fixed cam Sig requires revs to make progress, whereas the VVC has much more torque.

Ive driven both and prefer Revs tbh....

 

[DirtBuddha]

So just coming back to this topic...  

I had a Sigma 125 before I got my K Series. I loved it, but like the OP I wanted more power. I looked at all the options and realised I was going to have to spend at least £4k to get it, and I wasn't sure I'd get that back if/when I sold the car. 

A few months later a friend offered me a drive in a K Series... I was immediately impressed by how much more willing to rev the K Series is. It's not that the Sigma wasn't willing to rev - it was, but not in the same way that a 1.6 K Series is 🤪   I found the whole experience to be much more engaging than my Sigma and, for me, that's what Caterham's are all about... the most engaging driving experience possible. Long story short: I sold the Sigma and bought a K Series. 

Regarding upgrade potential:  

K Series engines are cheaper to upgrade than Sigma's and have possibly more tuning potential. It's easy and inexpensive to get a 1.6K to 140-160bhp and there are lots of people who have taken a 1.6 K Series to 180bhp+. I know at least 1 person who has a 1.6K running 196bhp very reliably with just head work, cams, ECU and throttle bodies.

Parts for K Series are relatively inexpensive. The ECUs are easy to remap (unlike Sigma's) and there are several places offering them. Larger intake manifolds/TB's (eg the VVC manifolds) cost less than £100. 

And then there's the option of course to swap in a 1.8l... with even greater tuning potential. Used 1.8 engines are available for £250-£500.

I'm not evangelising the K Series - that's not my intention. I'm simply highlighting to the OP (who sounds like he hasn't bought a car yet) alternatives that may get him what he wants at less cost.

There are other engines than Sigma's that have considerable tuning potential at the cheaper end of the Caterham price scale

Edited August 5 by DirtBuddha