Super Unleaded and 1.4 K series

[MikeK]

I understand the Rover K series 1.4 fitted in the supersport is supposed to run on super unleaded. Does anyone know if it can do any damage (e.g. to the catalytic converter) to occasionally run on bog standard unleaded?

Thanks for any advice,

Mike K

🤔

 

Thanks for all the responses. Nice to know that its not necessary to search for garages with SUL. 😬

 

Edited by - MikeK on 24 Feb 2003 22:16:30

[Mick Day]

I always ran mine on standard unleaded with no apparant problems. However, I always used super for track days.

 

Hope this helps,

 

Mick

[Allen Payne]

Mine runs on fine on either, but I always try and use super for trackdays.

 

Regards

Allen

[Sheds Moderator]

Mine is OK on UL. Maybe you lose a few BHP but there are lots.

[V7 SLR]

Won't affect the cat at all.

 

In addition, the octane rating only limits the extent to which you can tune the engine for more power. Unless your ECU can sense what fuel you are using, you will get neither more or less from using SUL or normal UL because octane's property is to help fuel NOT self-ignite under pressure and heat. The only way an engine will generate more power from a different fuel is if it's timing were adjusted to take advantage of a higher octane's ability to NOT self-ignite.

 

AFAIK the MEMS is unable to determine what fuel you are using, probably because the K (in a Caterham) doesn't utilise a knock sensor.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

 

Edited by - V7 SLR on 24 Feb 2003 10:51:42

[V7 SLR]

In addition, the reason why you would use SUL at a track day is because your engine will run hotter, therefore self-igniting (detonation) is more likely. SUL will combat this.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[Nifty]

I asked this question last year when I got mine and Caterham told me that it would run fine on both but to extract the last horsepower out of it use Super Unleaded, but the difference would be small.

 

The only way an engine will generate more power from a different fuel is if it's timing were adjusted to take advantage of a higher octane's ability to NOT self-ignite.

 

AFAIK the MEMS is unable to determine what fuel you are using, probably because the K (in a Caterham) doesn't utilise a knock sensor.

---

From my conversations with Caterham I understood that the mapping was set for best performance from SU but the difference between that and standard would not really be noticeable except on the track. Hence the reason the owners Manual specifies SU for the SuperSport.

 

I've been using Optimax for the last 12 months and it certainly gives the impression of increasing the bark and bite.

😬 😬 😬 😬

[V7 SLR]

If it has been mapped for SUL then in order to be fully clued up, you need to know the conditions at which the engine was running during the mapping session. It is reasonable to assume that your car runs hotter when used on a track, which will influence the fuel's point of self-detonation (WRT to the engine cycle). I would imagine that these factors would have been considered, although the opinions of the state of some people's mapping being what it is, it might not.

 

What I mean is, if the car was mapped for SUL at the high temps experienced on-track, then on the road you have a slight safety margin which would allow for the use of normal UL. Then again, given that the K doesn't have a knock sensor, you probably have a larger safety margin in-built anyway.

 

And then given that larger safety margin, it is debatable (e.g. I would like to hear some debate) as to whether the engine was actually mapped for SUL at all. I don't know how much different your timing would have to be to take advantage of SUL over normal UL. By "take advantage" I mean, "make some real use of".

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[V7 SLR]

And another thing... normal UL and SUL have the same calorific value, so there is no extra power to be gained from SUL over the other. If your car is mapped for SUL, and I mean properly mapped to take advantage of SUL, then if you notice the difference between normal UL and SUL I would submit to the panel of experts that you are possibly hurting your engine running it on normal UL. I'm basing this on the belief that your car will work 100% on SUL, so if you run it on normal UL it may be suffering pre-detonation.

 

That's never a good thing.

 

I've tried my DVA'd SLR on all variants (including a small top up of 4 star once when I had no other option) and I can honestly say they all seem to offer exactly the same results. Haven't checked it out on a RR though with different fuels.

 

In my old GSi Cavalier, it had a knock sensor fitted. It also had a plug that you could insert one way or the other to indicate to the ECU which fuel you were intending to run on. If you ran it on the SUL setting and the knock sensor detected knock, it would supposedly switch back to the normal UL map.

 

Given that the SUL plug setting was for 98 RON and we can only get 97 RON in England (ignoring the recent addition of Optimax which is supposed to be 98 RON) then I can only assume I only ever managed to utilise the normal UL map.... unless you believe that the RON number is a minimum and most fuels easily exceed that number. Again, I never scientifically checked it (it was 4WD and I didn't know of any 4WD RRs in the area).

 

It's an interesting subject.

 

Apparently the drag racers in the States use fuel with high oxygen content which genuinely do give more power. Would probably blow the head off my K if I tried them though.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[Peter Carmichael]

SUL burns slower than UL.

 

SUL has fewer calories than UL, because there is a higher proportion of octane modifying additives compared to fuel molecules.

 

Optimax is known to burn fast, unlike traditional SUL.

 

The things that will make you need SUL over UL are high compression (by design) or abnormally hot running. If (without these things occuring) you have an UL specced map, you will get the same performance on UL as you would get with an SUL map on SUL.

 

But they burn at different speeds.

 

So the faster burning fuel feels to the engine as though you have an extra degree or two of advance.

 

So running UL on an SUL mapped engine will give more effective advance, which may cause pinking problems.

 

Running SUL on a UL mapped engine will give less effective advance, so the engine will produce less power/efficiency.

 

Optimax seems to presume on the engine having been mapped conservatively (most engines are) for UL. Therefore an extra degree or so of advance really picks up the power/efficiency. Race engines are usually mapped aggressively to minimum best timing. Optimax run on an engine mapped to minimum best timing on SUL will be closer to pinking and will not produce more power.

[Mark Piper]

Peter, I run Optimax in my SLR - it certainly helps the engine to run smoother from cold. I am aware that the SLR runs fine on normal unleaded - does this mean that it falls into your category of an engien mapped to use UL? Hand on heart I can't say that the engine produces any more power on Optimax though....

[Steve-B]

but the # 64K question, does an emerald sense or get feedback? i think the answer is in the mapping IMHO

 

Steve

210Bhp SV-VHPD click here to see our pictures....

[V7 SLR]

No it doesn't get knock feedback owing to the lack of knock sensor in a Caterham rather than anything lacking in the map. I don't know if there's a knock sensor in the Rover installation.

 

The Emerald doesn't have the ability to switch between maps anyway or change timing advance based upon detected knock (at least the version of the software I have doesn't, and mine's pretty current - V1.1 rev 5).

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[Neil F]

This is an interesting thread.

I run an Impreza as my other car and the boys on the Subaru web board are always banging on about RON ratings and the effects of NUL/SUL.

I've also heard many a mixed story regarding the benefits/downfalls of Optimax.

The Subaru ECU does run a knock sensor and so fuel quality can produce some very noticeable changes in performance. I am suprised that the K-Series ECU doesn't and if so then as Peter and V7 say, I can't see you reaping a benefit as the map will have a conservatively fixed timing advance for worst case conditions (most probably).

The comment on Optimax burning faster is particularly interesting as it may explain a snippet I'd heard:

Apparently Optimax is so much cheaper than SUL because it is lower in aromatics than SUL and this determines the taxable rate of the fuel. The 97.8 to 98.3 octane level quoted for Optimax is achieved through octane booster additives. Could this explain the faster burn rate (as it is more akin to NUL) and why Subaru owners have complained of pinking when using it? Could it also explain the other report of Optimax's RON rating degrading quickly if left in the tank for extended periods? Could that in turn explain why Optimax is rated as between 97.8 to 98.3 RON?

I run my Impreza on SUL with octane booster as a preference, certainly while on track and only use Optimax when necessaary or preferably when mixed with some SUL.

It could be that Optimax is a good thing in a K-Series for all the above and not so good for cars with ECU's like the Subaru (which remember suffers from the effects of turbocharging, increased intake temperatures etc).

 

Bring on the learned responses!

 

Neil.

 

Better to burn away and fade out, than to burn out and fade away....

 

Edited by - Neil F on 26 Feb 2003 17:28:01

[rgrigsby]

A used to have an Audi S3 that did have a knock sensor, switching from UL to SUL made a noticeable difference in performance and gave a 5-10% improvement in economny as well!

 

When Optimax came out that seemed to improve things again although only by a little

 

Cheers

 

Rob G

www.SpeedySeven.com

[Neil F]

I thought that the points raised here regarding Optimax, knock sensors etc were worth a bit more input.

Any takers?

 

Neil.

 

Better to burn away and fade out, than to burn out and fade away....