I'll have a '99' please...

BX Tech talk
Post Reply
User avatar
Philip Chidlow
Over 2k
Posts: 11594
Joined: Fri Oct 07, 2005 1:08 pm
Location: Chelmsford, Essex
x 25

I'll have a '99' please...

Post by Philip Chidlow »

Is putting 99 octane unleaded in my GTi going to be OK over time. It seems to make for slight 'perking up' but maybe I'm imagining it!

Tesco do a 99 for 90p a litre. Not too bad, and combined with lead substitute from a bottle every fourth tank I suppose it won't be doing any harm. But am I wasting my money?
• 1992 Citroen BX TZD Turbo Hurricane
• 2006 Xsara Picasso 1.6 16v
jeremy
Over 2k
Posts: 2112
Joined: Fri Jul 01, 2005 2:58 am
Location: Hampshire UK

Post by jeremy »

8 valve GTi will run on unleaded and is designed to do so. 16 valve is not the same and Citroen stated that certainly the earlier ones ran on leaded - but no-one seems to know if this is due to the valve and seat materials or the need for high octane fuel required because of the very high compression.

The compression on the 8 valve engine is 8.4 : 1 according to Glass data sheets for 1989 and it requires 97 octane fuel. The 16 valve is 10.4:1 compression and requires 98 octane.

So far - so good. the next bit depends on the type of fuel injection and what its abilities are. A simple system will simply advance or retard the ignition according to its installed instructions - later ones are sensitive, have knock sensors and may adjust the advance acording to prevailing fuel.

The EFi systems fitted to the 8 valves tend to be revised less frequently to that fitted to the 16 valve which actually may be advantageous as there is less computer to fight. If the thing 'learns' then an improvement in fuel quality may mean that the system has to be tricked to get it to recognise better fuel.

What I mean is that if the thing retards itself to avoid pinking its probably happy once that state has been reached and the engine won't pink. Put in better fuel, it still doesn't pink - so the computer doesn't detect anything different! Disconect it for long enough for all settings to be lost and it will start learning again and appreciate the benefits of good fuel.

Were'nt carburrettors and the kettering distributor simple!

jeremy
Dollywobbler
Over 2k
Posts: 3940
Joined: Sun Dec 04, 2005 2:25 pm
Location: Wales
Contact:

Post by Dollywobbler »

Am running my 16v on 95RON because I'm a cheap-skate. Doesn't seem to be making a huge difference but then I haven't tried it on higher rated fuel!

Ian
User avatar
Cornishbx16v
BXpert
Posts: 403
Joined: Wed Oct 05, 2005 3:41 pm
Location: Cornwall
Contact:

Post by Cornishbx16v »

ive run mine on both! i thought i noticed a slight difference on optimax style fuels, but i think that was me wanting to think that! i have no issues of running mine on std unleaded (normally tesco or the cheapest around) but one thing to beware is that optimax style fuels will 'go off' quickly if not used! i didnt use mine for 2 weeks with a fulltank of optimax and got 180 miles out of the tank! not good!
Timmo.

After all I AM CORNISH!!!!

www.bx16v.com
www.bx16v.co.uk/forum
www.bx16valve.co.uk
User avatar
Toddman
BXpert
Posts: 389
Joined: Sat Jul 02, 2005 12:55 am
Location: Lincolnshire
x 2
Contact:

Fuel

Post by Toddman »

In simple terms if you car has a knock sensor then what happens is this -
The knock sensor tells the ecu when pinking occurs, normally the ecu will try and run as much ign advance as is possible within its map but the knock sensor prevents too much advance which causes pinking.
A higher grade fuel will allow more ign advance than a low grafe one so YES you should feel a slight perking up if using good fuel after rubbish fuel if you car has the relevany ecu system.

The 16v has been discussed many times and if you thrash it within an inch of its life everywhere then highh octane or an additive is wise.
My head came off at around 50k and the seats were ok but there were signs of deteriation although I used to chuck whatever pump was available in it nowadays it gets the optimax or equivalent or a shot of Valvemaster plus.
Must say not heard of any 16valves packing up through head troubles associated with poor fuel though.

Cheers
Luke
Please call me Luke :)
1989 BX 16valve White 70k - G764KEW


http://www.bx16valve.com
User avatar
Ian_Fearn
Spender lotta cash on Citroens
Posts: 2231
Joined: Fri Jun 03, 2005 9:51 pm
Location: Derbyshire

Post by Ian_Fearn »

Is everybody migrating now from BX16V.COM?
Over and out from me
User avatar
Vanny
Merseyside resident
Posts: 3581
Joined: Tue May 17, 2005 11:48 pm
Location: BXProject
My Cars: BX 16v Ph2 - Jazz
BX 16v Ph2 - XPO
x 79
Contact:

Post by Vanny »

theres only me luke and cornish, and i dont count cos i have diesel runing through my car!


Hate to say it, but this is much better forum, more people, more fun and much more content to waste time with! Its a credit to the BX's of the world and its creators!
User avatar
Toddman
BXpert
Posts: 389
Joined: Sat Jul 02, 2005 12:55 am
Location: Lincolnshire
x 2
Contact:

Forum

Post by Toddman »

I have been here for ages just didn't feel the need to post very often.
A few threads have caught my eye so thought I would drop my collection of useless information into the fold :D

Cheers
Luke
Please call me Luke :)
1989 BX 16valve White 70k - G764KEW


http://www.bx16valve.com
User avatar
Ian_Fearn
Spender lotta cash on Citroens
Posts: 2231
Joined: Fri Jun 03, 2005 9:51 pm
Location: Derbyshire

Post by Ian_Fearn »

The more the merrier in my opinion! :D
Over and out from me
Dollywobbler
Over 2k
Posts: 3940
Joined: Sun Dec 04, 2005 2:25 pm
Location: Wales
Contact:

Post by Dollywobbler »

I'm here too!

Ian
User avatar
Stinkwheel
1K Away
Posts: 1516
Joined: Wed Jan 04, 2006 9:38 pm
Location: In front of this flamin' PC

Post by Stinkwheel »

I'm not.
Doctor Of Gonzo Journalism!!!
93 BX TZD Estate
90 BX 14TE St Tropez
93 BX 19 TXD Estate
92 BX 16TXi
77 Ami 8 Break
79 Acadiane
81 Dyane6
84 2CV6
85 GSA saloon rally car
To slightly mis-quote Kitch ... "BX 14. They're just brilliant!"
Stewart (oily!)
1K Away
Posts: 1604
Joined: Wed May 18, 2005 6:23 pm
Location: North Wales

Post by Stewart (oily!) »

Hi sixteen valve guys, as the thread started off on fuel here are my recommendations, regular pump deisel is fine but a few litres of cooking oil may be added per tankful, a dash if paraffin is good too in order to clean the injectors, if travelling abroad then french deisel contains some biodeisel and this often results in improved performance/economy :)
Stewart
TZD 19 TD one of the few
Xantia Td estate, going soft
Post Reply