Opinions solicited: 270S vs 310S

[Yoram]

Hi All, as some of you know from another thread, I am going through the spiritual transformation towards ordering my Seven.
I don't expect to do a lot of track events (although I have a lot of experience on the track), but rather spend more of the time in the car up and down the many fun mountain roads close by.
Therefore I intend to order an S-Pack car with some performance options (e.g., rear sway var, sport suspension, LSD).
I want to stick with the smaller engine but having a tough time deciding between the 270S and the 310S. From the specs it looks like the max torque is virtually the same but in the 270 it comes 1500 RPM lower.
That and the lack of a 6 speed make me wonder whether the the 270 does not have better drivability other than flat out near the redline. I may be wrong, so the question is whether the 310 is worth the extra $2000 in driving joy.
I would appreciate all views from first hand experience.
Thanks!

[Vovchandr]

Without knowing any particular details between the two myself, I rather have a question about you and how you like to do things.

Will you buy this and leave motor more or less alone indefinitely or will you always tinker and seek upgrades for more power?

If you're the latter, from much personal experience I'd say spend as much money up front as you can and get the most you can. No matter what power you will have you will almost always get used to it and want more, but at least you won't have to deal with downtime and work etc while trying to upgrade and spend the same money or even more in the long run.

If you want to save money and you don't plan on tinkering I'd say 270 will suit your needs. Again no personal experience between the two but straight line power etc will be essentially unnoticeable between the two especially considering these aren't straight line cars.

The 5spd vs 6spd and final gearing will by far have a more drastic difference than those two engine choices.

Do these come with Duratecs as well? According to the builder I think Duratecs start with 360 but I don't think they sell Sigmas in the states?

Found this thread for some more opinions
https://www.lotus7.club/forum/chitchat/310r-vs

[jimmylukeii]

First, I strongly suspect you can't go wrong. You'll have a stupid grin no matter what.

I don't know how helpful this will be, but here is the analysis I ran through when making my choice last month. First, I am coming from a high hp Cobra, so my main fear was having too little grunt via the Sigma. But talking with a few folks and reading a lot made me think the Duratec may not get me what I wanted: more pedal to the floor, high rev fun. At least not on the mountain runs I love.

So then the choice was 270 vs 310. My fear was that I would yearn for more power quickly, and I understand that bumping up cams, new mapping, etc. after the fact would be more than the initial $2k difference. And I don't know how many shops would be willing or qualified to do the work. I also wanted the ability to slide the back end, and that seems more attainable with the 310.

Also, on the forums, the people who had a 270 and did the upgrade seem to really enjoy the difference.

Lots of blathering, so I will end with this article on a group that did the upgrade: https://www.autoexpress.co.uk/caterh...ham-seven-310s

Good luck!

[Yoram]

@Vovchandr and @jimmylukeli, thanks a lot for the quick and great replies and the very helpful links.

To your questions, @Vovchandr, I do not initially plan to do engine tweaking in search of more power. I look forward to enjoying primarily the handling and the connected driving experience and believe there should be sufficient power even with the base engine to enjoy and maybe even scare myself a bit here and there. Also, both the 270 and 310 are Sigma engines with different cams and tune and both are part of the current US specs for these models, and come only with 5 speeds.

My primary concern other than cost is/was whether the 310 is less flexible than the 270 and less ready to rotate if you fall between the gears carving up the mountain. All the feedback in the links indicates otherwise (in favor of the 310) and so is the expert opinion of Josh Robbins from Rocky Mountain Caterham, who BTW has been great help already. Another dilemma is having to miss out on the lightweight flywheel with the S-Pack (for which Josh pointed out $$ solutions)...

I am still inviting additional opinions and experiences from members to learn of any other angles to this topic.

Thanks again, guys!

[Croc]

I have driven all spec Caterhams at one time or another. The 1.6L Sigma is 270 and 310 models. 2L Duratec kicks in at 360, 420, and 620 models. The CSR is still out there at 200 and 260 models with 2.3L Duratec.

The difference between the 270 and 310 is character. The Sigma is a naturally revvy engine compared with the Duratec. Sounds better too - just as good as the old crossflow. I think the 310 is revvier and more lively than the 270. Its not much difference in hp - 15hp or something close. Difference in torque is a non event - you do not feel it. But the 310 has a higher rev limit and feels better for all of that. The 5 speed Miata gearbox has not got the greatest of ratios with really only 4 gears in use so having the ability to use revs improves the driving experience.

It will require you to change your driving style - no big v8 to lug you out of tight corners. You will need to learn to get the weight on the nose early (or trail brake) to pivot the car around crisply. Fail to do that will give you understeer. Simultaneously you will be making sure you are in the right gear with about 3500+ rpm on the clock to punch it out of the corner. It will make you work as a driver but once you get it right it is so satisfying.

If you do outgrow the Sigma hp then you have upgrade paths with Premier Power in the UK who produce some good upgrade kits that are well regarded with the L7C guys.

To give you an idea of what a 310R is capable of then here is one at Donington. I only ever use 1st to 4th gears - never use 5th until over 110mph because it is an overdrive.






Also consider if you can stretch for 13" wheels - that transforms the driving experience by accentuating how quickly the engine spools up plus improves handling and ride comfort. Its hard to describe until you experience it on a back to back test. You will have to consider ride height when you set up the suspension.

[11Budlite]

If you do a search in the following Low Flying archives you'll find some articles on the 310 and the Sigma motor. Just type in Sigma/310/premier power/etc and you should find some good write-ups. Sorry I couldn't link directly to the articles. Here:http://lowflying.lotus7.club/lowflying/search.jsp After doing some research and communication with several owners I decided to go with the 310. I had an idea on what I wanted as far as the driving experience and thought that the 310 best fit the bill. Like Croc said, I'll probably be shopping for a set of 13" wheels with stickier tires at some point. I did get the Premier Power lightweight flywheel/clutch setup which reduced the rotating mass by almost 50%. I'll have mine on the road when the roads are clean this spring and can give a better review at that time.

[Yoram]

@Croc and @11Budite, thanks a bunch for the additional insight.

@Croc, I am well familiar with driving low torque high revving cars and with trail throttle/braking to help turn-in (I have a street '87 911 which you cannot get to turn-in otherwise). The car before my Holden VFII with its 6.2L V8 was an E46 M3, as high revving/low torque as they come (but it had a 6 speed). Actually most of my cars over nearly 5 decades have been high revving low torque. The reason I brought up the torque, or rather torque band question is that with low torque and relatively wide ratio transmissions you end up "hunting" between gears in the mountains (which can be fun too with a good gearbox).

@11Budite, thank you too for the comments re 310 and lightweight flywheel.

And thank you both for the tip on 13" wheels. Duly noted. At this point I am speccing the base 14" "Minilite replica" wheels because I simply love how they look and fit the historic character of the car.

Thanks again!

[Yoram]

To give you an idea of what a 310R is capable of then here is one at Donington. I only ever use 1st to 4th gears - never use 5th until over 110mph because it is an overdrive.





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P.S., Awesome video!! Makes my mouth water...

[Kitcat]

Minilites come in many sizes, including 13". As the size goes down, unfortunately, so does the tire choice. FWIW-my Cat came with a 13" wheel/tire combo up front that, together, weighed in around 19 lbs.

[wemtd]

Kitcat- How much do you think this really affects us?
It seems everyone uses one of a small number of tyres (Hoosier, Avon, toyo) that suit our car’s performance needs (vs. having more size options and the same number of performance options)