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What car's that in then bstardchild?

bstardchild wrote:

Del_GTi wrote:There is no way you'd get 10bhp of a difference from using super-unleaded. Doesn't matter if it's from a supermarket or a big producer.

Errr maybe for a GTi thats true.......

Yeah it is true.

Fair enough on a turbo'd or twin turbo'd car with a lowish compression ratio and some nice boost you can get decent gains with a higher octane fuel but the GTi engine doesn't have high enough compression to generate the heat to make the most of the 98-99 octane.

ModifiedMadness wrote:What car's that in then bstardchild?

http://www.tigerstyle.co.uk/poloforum/v ... php?t=8414

the top one

What a beast!!!!

I love those.

Del_GTi wrote:What a beast!!!!

I love those.

It's the main reason why the Polo hasn't had a heart transplant

bstardchild wrote:

ModifiedMadness wrote:What car's that in then bstardchild?

http://www.tigerstyle.co.uk/poloforum/v ... php?t=8414

the top one

... ... ...



Lovely

Hi guys,

So after reading this discussion on fuel have we decided which is best for the Polo GTI??

Any suggestions will be of great help!!

Cheers guys!!! oh and girls if there are any out there!!

i wouldn't use anything other than shell optimax, bp ultimate is poo

hmmm fair enough, everyones different! if people are happy with their fuel and the price they pay for it then thats cool!

just wanted to enlighten everyone with the tesco product!

good luck in your quest for the ultimate fuel!

hehe

bstardchild wrote:

Del_GTi wrote:There is no way you'd get 10bhp of a difference from using super-unleaded. Doesn't matter if it's from a supermarket or a big producer.

Errr maybe for a GTi thats true.......

My "other" car when run on the Dyno on normal unleaded makes 35 bhp less than when it's run on Shell Optimax or BP Ultimate.

35 bhp down from 377 is very very noticable

It pulls 6th from 60 mph when run on Optimax or Ultimate

It pulls 6th from 70 mph when run on super unleaded

It won't pull 6th till 85 mph when on normal 95 RON

It's all down to knock sensors and maps

Run lower RON and the knock sensors pick up knock so change the ignition setting - that loses power

Revert back to higher octane fuel and the knock sensors don't pick up knock so change teh ignition and that gains power

Optimax is very very good fuel but it goes off real quick

bstardchild has hit the nail on the head! the gti engine does run quite high compression and it loses power through detonation if don't use at least a 98ron fuel, optimax is the best but only as long as its fresh ! i'm not too sure about the difference in peak BHP when using normal 95ron and optimax, but there is a big gain in torque through the whole rev range when using fresh optimax for me (though I will still get detonation if I try to use full throttle from very low revs frequently), which must just be down to engine to being able to use the high compression without the engine knocking anymore !

Del_GTi wrote:Fair enough on a turbo'd or twin turbo'd car with a lowish compression ratio and some nice boost you can get decent gains with a higher octane fuel but the GTi engine doesn't have high enough compression to generate the heat to make the most of the 98-99 octane.

I ignored this coment earlier cos it didn't seem important to correct anyone as the thread is about Fuel octane and benefits but.....

1st point - I thought GTi's were 10.5:1 thats fairly high compression

2nd point - My track day car will be running 11.3:1 and thats about the limit for pump fuel (even optimax or ultimate)

3rd point - it's not just about compression

Compression will give a bigger bang..... Compression will generate more heat but the heat doesn't make power - it's a by product of it!!!

We aren't talking about diesels here are we?

you need in addition to good compression

- the right amount of fuel (and air to a stoimetric mix)
- the sparked timed at the right time
- the right ammount of overlap on the cams (to clean the dirty gasses out without wasting fresh charge)

It's more than just compression way way more

clees wrote:So after reading this discussion on fuel have we decided which is best for the Polo GTI??

My advice for a GTi or any other performance car (I don't own a GTi but I think I am qualified to coment under the performance car banner)

In my order of preferance and not including racing fuels which Ihave dabbled with on track use.

1. Optimax
2. BP ultimate
3. Branded Super unleaded
4. Branded unleaded (BP SHELL ESSO blah blah)
5. Any other unleaded ie supermarket fuels (I have to be really really desparate in the case of some of my other cars)

maybe this al depends on how good ur local garage is...?

i have print outs of the power graph to show the difference in when i used optimax and later when i used super sainsbury fuel!

maybe the shell garages in england have clean storage tank where as maybe up here they might be dirty...? this cud all affect wots actualy in the fuel ur usin!

i find that the best fuel i personally have used is super sainsbury's!

oh and for dubpolo - i only have a K&N induction kit and a main de-cat, (the little cat is still there)!

Grum wrote:maybe this al depends on how good ur local garage is...?

It could well do but not for the reasons you mention later

Grum wrote:i have print outs of the power graph to show the difference in when i used optimax and later when i used super sainsbury fuel!

1st - were the dyno runs done on the same day and on the same dyno? - if they weren't then it's not an acceptable comparison - sorry if this offends but it's a fact

Aside....

To see the difference between Optimax and Normal Branded unleaded I ran my Lotus down to the dyno on branded unleaded - it was a 260 mile trip so she was low on fuel when I got there

I did the first run (by the time it was over the fuel light was on) and then went out and filled up with Optimax - brim filled and came back and did another run in the afternoon

35 BHP for an extra 5p per litre!!!

2nd - higher octane fuel goes off very quickly - by off I mean the octane level drops - same thing happens with normal unleaded too but it's a slower process cos it's not so volitile!!!!

Grum wrote:maybe the shell garages in england have clean storage tank where as maybe up here they might be dirty...? this cud all affect wots actualy in the fuel ur usin!

Nope I think it depends on how much they sell - small garages don't normally sell Optimax if they don't sell a lot - nearest garage to me that sells Optimax is 14 miles away and it's amazing how many people I know will drive there to get it but it sells a lot - all the club racers using snetterton circuit (bikes and cars will fill up there) so it's always fresh

Grum wrote:i find that the best fuel i personally have used is super sainsbury's!

They obviously sell a lot of it and it gets turned over quickly - I'm not critising or saying you are wrong just trying to explain why it may well be that your car runs better on it - against the normal experience!!

fair enough mate, just givin my side of the story.

anyway.... if i find a local tesco with 99Ron, i'll try that too!