[timgti]

Always get the immpression that my Cooper S is'nt as smooth under full throttle as it should be.. Kinda feels hesitant as the power is delivered, its fine on gentle acceleration but is noticable as you put your foot down more.

Its a 53 reg and has done 25k miles and was recently serviced at MINI.

Have been reading about fuel additives such as Millers/ redex/ greased lightning, as I wondered if this may clean the fuel system and improve it?

Have also read that BMW dont change the spark plugs until 40k so it may be worth a new set of plugs to iron out any problems here also?

Any input from people would be appreciated!

Tim

[Space Cadet]

If you haven’t been using Shell V-Power already, stick a tank in along with some fuel additive.

Cant comment on which additive is better as they all claim to be, so just go for a good make and one that you put the whole bottle into a full tank, otherwise you have to keep fannying about adding a bit each time you fill up.

The additive will clean out your injectors and fuel lines and any deposits in the engine. V-Power has additives already in, so it will keep everything clean once you have used the additive.

I always use V-Power and used Optimax before it, all my cars have run much smoother and gained a few bhp, especially previous turbos and now the supercharger.

I appreciate that it is more expensive to fill up on V-Power but I do so little miles that I don’t mind, if you are doing high mileage than perhaps fill up every other tank and use good quality normal unleaded such as Shell in-between.

To cut a long story short I work in the oil & gas industry and Shell’s petrol is amongst the best and their V-Power has won loads of tests by EVO magazine.

This will hopefully sort everything out, but if you fancy a little cheap DIY maintenance then stick in a new uprated panel filter, and better spark-plugs, both are inexpensive and easy to fit so why not.

[Richard Crofts]

Change the plugs it might help, as if you don't do hard driving or reguklar long journeys etc it can lead to problems, dont bother with JCW ones just get NGK irridium range 7 ones (£25 delivereed, whereass JCW are about £20+ vat each or som,ething equally rediculous!)

I would use nothing less than 97 octane superunleaded. Even my stock MCS would run like a bag of nails on 95 standard fuel, so a JCW will be worse. if you can use the 98-100 fuels like BP, sheel etc

It may also be due to your sensors picking up too much heat in the engine intake temps, this can then cause the car to retard itself in an attempt to stop you breaking it by giving it full beans with hot air being used, and so melting something. Thjis is more common on higheer boost cars, but it could be seen in a JCW

The other factor could be a dicky Tmap sensor, about £30 from BMW and 5 mins to fit.

its difficult to diagnose the problem without reading the fault codes or having a full health check. 1320 (near bedford?) and ThuinkMINI (worcestershire) boith do this service using either a data logger on the road @ thinkMINI or a rolling road @ 1320. I know Thinkmini have a qualified snapon trained and BMW trained diagnostic tech (1320 may also have a specialist).

[super c00per]

Are the spark plugs an easy and easily accessible thing to do yourself??

[Richard Crofts]

On stock and JCW cars, yes. You just need a plug socket and maybe a star driver to take the IC cover off (4 small star drive bolts) ... but i have a feeling the stock IC cover doesn't even cover the sparkplg tops so you might not have to do theat. The GP IC cover does block 3 of thwe plug tops though and the cover has to come off to remove them (the IC itself stays in place). The plugs come gapped out of the box (the NGK ones anyhow) so its bolt out bolt in job done. Still might be an idea to see if there are any fault codes being picked up, as this could save you a lot of time and cash.

[Shmoo43]

I'm new to MInis, but not new to tuning cars. I recently started daily driving an 05 S, and I have to say that my immediate impression was it has a crappy fuel map. Smoother and less sc lag with the DSC turned off, but a dyno & tune would most likely do wonders for these cars.

[Richard Crofts]

What map have you got? It makes a difference ... BMW produces all sorts of variations of the stock map to refine it over the years. Also some people poo poo the JCW map as a pile of cack compared to the stock map. I run a stock map that was last updated in late 2006 and it has a wonderfully smooth power curve on the stock car, recently it also showed a nice smooth power and torque curve.

RMW in US dio see some major improvements on many of the cars they tune in the states, as do 1320 via them in the UK. However if you have a good map, and mine appears to work well.... its perfectly viable to use a stock one and tweek parts to make it work better on a tuned car.

Also you may not have a map problem, you could have a retardation probklem, timing, boost sensor problem... all sorts of things that can make the car feel like its not delivering its potencial... i may not be the map thats the issue, but a small inoccuous part that causing the car to hesitate or hold something back ... The tell tale is your feel of supercharger lag. Superchargers shouldn't lag really, not in the typical sense like with turbos. What revs do you require before the 'lag' goes and she starts to really fly?

[timgti]

Thanks for the responses guys

The feel is not so much of a 'lag' its more of a lumpy acceleration on WOT (almost like your waiting for something to unblock itself before it becomes smooth again if you get what I mean!) In all fairness its not as bad as I make it sound, but I'm just not 100% convinced the performance is EXACTLY as smooth as it should be!

I do tend to do LOTS of short journeys like 1-2 miles per journey up to 5/6 times a day and only a few longer journeys at the weekend sometimes. I have also not been using anything other than regular unleaded, so i'm sure these 2 things contribute to the issue.

I think I'm gonna fill up with V Power and put some fuel system cleaner etc in (when I have decided what) and see how that goes. Might take out the air filter and check for crap as I'm not sure if BMW do this during the TLC services? Failing that some new plugs might be in order but we'll see how she goes.

[Shmoo43]

Regular? S should be running premium. Running regular will make the knock sensor retard your timing.

Check your spark plugs, I bet you're running lean and hot.

[Silent1]

Don't worry about additives, they're really not worth it.

Run a few tanks of V-Power through it (ideally run it on V-Power permanently), change the air filter and spark plugs, you'll probably find the spark plugs are horrible and the filter isn't great.

If i was you, just bung a K&N panel filter on in place of the original paper filter.

[timgti]

Well, interestingly I topped up with V-power today and could already notice the difference. Much smoother and generally felt better to drive. Seems to have stopped the hesitation under full throttle the few times I tried it, will report back further in a few days when I have had a few more tries!

Going to be interested to monitor the economy too!

[Space Cadet]

When I picked up my 2006 16k miles JCW last weekend I thought it seemed a bit sluggish, I ran the tank down to zero and then filled up with V-Power and it’s made a huge difference. I assume the previous owner/dealer had been using normal unleaded.

[Richard Crofts]

Just be aware the hesitation could be something more dramatic. My car had a cat that had fallen out and was blocking the exhaust under WOT. I doubt thats the fault with yours but just keep an eye/ear for it in future. TBH despite BMW saying the car will run on 95 I found that even in standard form my S was like a bag of nails on 95.... 97 works great and even on my tuned S (way above JCW spec) 97 works fine, but V-power and the BP race fuel make it work like a dream!

If you use a fuel cleaning agent, use nothing but redex (the one desgned for fuel injectors or EFi systems, not the classic) Most other cleaning agents are total pap, Redex is tried an tested over years and years.

[Lucky Dave]

I have seen plug leads cause this also.

[Richard Crofts]

Yep that was an adrian car wasn't it... thats why I got the magnecor race ones in the end

[Space Cadet]

I’ve just posted a similar thread in the JCW section, what if any difference do the leads make, there is also a ‘spark-generator’ thing available, are either of these worth it to a 16k mile car?

[Richard Crofts]

The stock MINI leads are a bit temper-a-mental! Basically the quality is not great and if you take them on an off a few times they seem to get damaged and so they don't let a decent spark. One way to resolve it was to fit the JCW leads (they are blue not the stock black), or buy Magnecor leads. I got race spec reds as my cars fairly tuned (plus I like red, as Dave will grimace and nod in agreement of )

Unless you have a problem again I'd not worry too much, just bear in mind to change the plugs every now and then and look at the leads if you have problems and yours runs stock ones

[timgti]

Pulled the air filter out today to have a look & IT WAS ABSOLUTELY BLACK. Covered in muck, flies and road grime! Surprised if any air was actually getting past at all! .. Cant believe that MINI dont even look at this until 40k as mines only done 25k at the moment!

Hoovered it out and replaced it but need to get a replacement asap as Im sure this has to be affecting economy/ performance!

Next question, is it worth getting a performance panel or just replacing it with the stock paper one?

[Space Cadet]

Upgrading panel filters will only make a small difference, but at the end of the day they do improve things a little and will probably cost less than an OEM paper filter so it is worth doing.

I’ve always preferred Pipercross, but everyone has their favourites. Have just fitted an ITG ‘cylinder’ filter to my JCW, I believe they also do panel filters.

[timgti]

Well, just called BMW and a new stock filter is only £5.96 + VAT so unless someone can convince me of spending £30-40 on a foam performance one? Or can point me in the direction of somewhere that doesn't charge the earth for them??.........