17 replies to this topic

[Goosenka]

Next friday I am going to CMS to map the car after the SC conversion. Having sought advise regarding the fuel you need in the car when you do the remap from various people it seems rather conflicting. Some say stick with what you use normally (local petrol station is Asda so standard 97ron Unleaded), others say shove the best in you can eg BP Ultima etc. I have read through the stuff on CMS' website but as always rely on the VX collective to help with some experienced based advise. Edit to add - Are there 'dangers' as such of using standard unleaded?

Edited by Goosenka, 02 March 2012 - 08:30 PM.

[MrSimba]

V Power or Tesco Momentum - nothing else goes in my VX!

[Zoobeef]

If you want to always put 99 ron in it then use that. I would as i use vpower everytime and have never been 'caught short' and had to put 97 in

[techieboy]

I got remapped based on V-Power but Cliffie got his mapped on the weedy stuff and it made chuff all difference to power. So go with whatever your normal stuff is, if that makes life easier come refill time. No harm in putting the good stuff in later, if you want.

[The Batman]

im going up with pikey stuff honest.... no v power here

[techieboy]

BP 102.

[Goosenka]

I got remapped based on V-Power but Cliffie got his mapped on the weedy stuff and it made chuff all difference to power. So go with whatever your normal stuff is, if that makes life easier come refill time. No harm in putting the good stuff in later, if you want.

John at CMS came at me with all kinds of long bloody words when I asked the question, so I put the phone to one side and made a cup of tea.

He was talking about temperature of this and you cant map on one and then use the other but you can map on this and then do that. I kinda gave up listening.

[VXTyrant]

I only use V Power. I heard the car will run lumpy if 'normal fuel' is used after having the car remapped - never had to to find out if this is true though!

[techieboy]

Map on the lowest octane you'd normally use. You can always fill up with higher octane without a problem. Mapping on higher octane and then filling with lower octane is not such a good idea. Or do what I did and say I'd only ever use V-Power or better.

[P11 COV]

My cms stage 4 says minimum of 97. I use V power or Tesco 99 most of the time.

[turbobob]

My map was developed on 98 octane. It will run on lower but best results on 98+ octane.

[slindborg]

cheapest shittiest gone off fuel from the middle of nowhere (so Norfolk is ideal for that) would be used in any car I have setup (carbs,EFI,boosted) and then gives you the scope to rock up on higher octane (lower energy) stuff when you fancy.

[snotvomit]

When I had my SC'ed MX5 it would get detonation if I used low octane - no fancy knock sensor going to the ECU or anything. If I could only get crap fuel then I retarded the timing with my timing controller. I always used V Power where possible. I use V Power in the VXR. I believe the VX is more protected against detonation than the MX5 was but I try to play safe and Liam advised me to use high octane when he did my remap. If I am doing track day and there's no V Power around, I use some octane booster. I've never noticed any improvement in performance though - just trying to reduce the chances of detonation. Am I being over-cautious?

[Nev]

Hi Goose, I dunno how much you know about this, but the objective of higher octane fuels is to allow the mapper to advance the ignition timing on the 4 stroke cycle so that more power can be gained from the engine at the higher end of the RPM. If you turn up with low octane fuel in your tank, CMS will just end up retarding this timing by a couple of degrees, thus meaning you wont get quite as much BHP from your setup. They take the base map, run the engine on the dyno several times and advance the ignition until they hear pre-det (knock) on the ECU and then backoff a safety margin (presumably dependant on ambient temps of the day). If you intend to track the car on a moderately regular basis, a good technique a lot of informed people use is to map the car to an easily purchaseable octane, say 99 (ie Tesco or Shell). Then on a track day, fill the car up with the next highest available octane (say BP 102). This provides you with extra protection for the higher charge temps that you will likely experience during sustain hard (ie hot) driving. However, having said this the Motronic 1.5.5 that the VXT uses (which may or may not be similar to your ECU (I just don't know)), will adjust the timing by upto 7 degrees based on whether it hears knock, so the above regime may yield you more 'extra power' for the track day. I have seen successive dyno plot of cars using this and the power graphs do indeed improve considerably as the ECU recalibrates itself. Lastly, the higher quality fuels do have extra additives that may help with the burn, however they do 'go off'/bad more quickly, so its not advisable to use them if you intend to leave your petrol in your tank for more than approx 6 weeks. I have a friend who runs a 550 BHP escort and after leaving his petrol in his tank for 6 weeks he felt it detonating and had to drive slowly till it all burnt up and refilled. I too have experienced this issue too with 1 year old fuel which caused hugely high EGTs after 1 year of sitting around. All in all, you have a performance car and I'd advise mapping to and using performance fuel (ie 99 Octane). If you can't get it one day, just use 97 and dont boot it to the max. HTH.

[kg55]

cheapest shittiest gone off fuel from the middle of nowhere (so Norfolk is ideal for that)

your avin a bird barf souven boy its £1.60 a litre in some places!! not far from me

[theolodian]

Dyno loads are higher than road loads, especially for the VX. Therefore, I would dyno tune on fuel at least as good as what you run normally. Then use the better stuff for track use. Better fuel makes a real difference on a mapped turbo engine. In order of 'goodness' for mapping; BP 95 Shell 95 BP Ultimate V-Power 102 You can run one grade lower if the map isn't too aggressive. For instance, you can map on V-Power and run that or BP Ultimate. Or you can map on BP Ultimate and run that or Shell 95.

[chrisgold]

map with v power and 20% meth, but then you always have to run with it

[Goosenka]

Hi Goose,

I dunno how much you know about this, but the objective of higher octane fuels is to allow the mapper to advance the ignition timing on the 4 stroke cycle so that more power can be gained from the engine at the higher end of the RPM. If you turn up with low octane fuel in your tank, CMS will just end up retarding this timing by a couple of degrees, thus meaning you wont get quite as much BHP from your setup. They take the base map, run the engine on the dyno several times and advance the ignition until they hear pre-det (knock) on the ECU and then backoff a safety margin (presumably dependant on ambient temps of the day).

If you intend to track the car on a moderately regular basis, a good technique a lot of informed people use is to map the car to an easily purchaseable octane, say 99 (ie Tesco or Shell). Then on a track day, fill the car up with the next highest available octane (say BP 102). This provides you with extra protection for the higher charge temps that you will likely experience during sustain hard (ie hot) driving.

However, having said this the Motronic 1.5.5 that the VXT uses (which may or may not be similar to your ECU (I just don't know)), will adjust the timing by upto 7 degrees based on whether it hears knock, so the above regime may yield you more 'extra power' for the track day. I have seen successive dyno plot of cars using this and the power graphs do indeed improve considerably as the ECU recalibrates itself.

Lastly, the higher quality fuels do have extra additives that may help with the burn, however they do 'go off'/bad more quickly, so its not advisable to use them if you intend to leave your petrol in your tank for more than approx 6 weeks. I have a friend who runs a 550 BHP escort and after leaving his petrol in his tank for 6 weeks he felt it detonating and had to drive slowly till it all burnt up and refilled. I too have experienced this issue too with 1 year old fuel which caused hugely high EGTs after 1 year of sitting around.

All in all, you have a performance car and I'd advise mapping to and using performance fuel (ie 99 Octane). If you can't get it one day, just use 97 and dont boot it to the max.

HTH.

:: thanks