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

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

Post by Philip Chidlow » Sun Jan 08, 2006 3:01 pm

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?
• COMING SOON... 1992 Citroen BX TZD Turbo Hurricane
• COMING SOON... 1998 Citroen Xantia 2.0 16v auto Exclusive
• Xsara Picasso 1.6 16v
and some Ford tat lol

jeremy
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Post by jeremy » Sun Jan 08, 2006 3:59 pm

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

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Dollywobbler
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Post by Dollywobbler » Tue Jan 10, 2006 4:01 pm

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

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Cornishbx16v
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Post by Cornishbx16v » Tue Jan 10, 2006 4:13 pm

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!!!!

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Toddman
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Fuel

Post by Toddman » Tue Jan 10, 2006 5:46 pm

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

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Ian_Fearn
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Post by Ian_Fearn » Tue Jan 10, 2006 5:48 pm

Is everybody migrating now from BX16V.COM?
Over and out from me

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Vanny
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Post by Vanny » Tue Jan 10, 2006 10:28 pm

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!

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Toddman
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Forum

Post by Toddman » Tue Jan 10, 2006 10:43 pm

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

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Ian_Fearn
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Post by Ian_Fearn » Wed Jan 11, 2006 12:28 pm

The more the merrier in my opinion! :D
Over and out from me

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Dollywobbler
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Post by Dollywobbler » Wed Jan 11, 2006 1:29 pm

I'm here too!

Ian

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Stinkwheel
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Post by Stinkwheel » Wed Jan 11, 2006 2:02 pm

I'm not.
Doctor Of Gonzo Journalism!!!
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Stewart (oily!)
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Post by Stewart (oily!) » Wed Jan 11, 2006 2:49 pm

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
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Xantia Td estate, going soft