GolfGTIforum.co.uk
Model specific boards => Golf mk2 => Topic started by: Godzilla on 01 March 2008, 12:13
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I looked inside the fuel cap (checking for any rust!) of a 1990 Digi im buying and it said 98. Does this mean this car will have to be run on Super Unleaded? I used normal 95 in my previous Digi's and they seem to have ran ok, but neither had a sticker on inside of cap.
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It's fine on any unleaded as it has a knock sensor that adjusts the timing depending on the fuel.
Nick
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98 is the safer fuel as these are higher compression engines, therefore the charge burns a little hotter.
The higher the octane, the more anti-knock agent the fuel has. This helps prevents the onset of detonation at high burning temps.
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Go to Tesco, get shopping worth £50 then get the 99 ron at a cheaper rate (with the voucher -5p on every litre) :evil:
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Go to Tesco, get shopping worth £50 then get the 99 ron at a cheaper rate (with the voucher -5p on every litre) :evil:
Thanks mate :wink:
Would 98/99 ron make a differance to performance then to an 8v Digi.....also would it use more fuel being its higher octane?
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The performance by using 98 would not change. The general census of opinion is that the higher the octane rating, the more performance. This is B.S. High peformance engines running high compression ratio, or turbos need higher octane ratings to reduce the risk of engine damaging detonation. If you have a normal engine for the average family car, then 95 is adequate. But for our Golf GTI's, although by todays standards have pretty mediocre power outputs, they are still high compression ratio engines and benefit from higher octane rated fuels.
In days of leaded petrol, tetra ethyle lead (TEL) was added to petrol to increase the octane. 100 octane which equates to about 6 or 7 star, is used for most light aircraft with 130 octane being available for high performance piston engined aircraft or high altitude planes. TEL has been replaced by another anti knock agent for todays lead free fuels.
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I have tried both fuels 95 and super unleaded and there is no noticable difference - you have to remember that your engine will be at least 16 years old and thats if it is one of the newest mk 2's. Some people claim to see a difference and to be honest I did - in my wallet!!
You'd probably see a difference if you had an impreza or a another highly tuned car!
Have a search for 'which fuel?' and i'm sure there is enough discussion for you to make up your own mind :smiley:
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I find that my car is not as jerky/shakey with 97/99 ron at low speeds (pulling off/traffic)
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my digi pinks/detonates often under load with 95 ron.
the knock sensor wiring is all cracked tho, so probably doesnt work too well...!
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with Mk2 Kezza on this
Tried runing both boggo unleaded and BP Ulitmate .
Only difference - bigger dent in the wallet - oh and mines a Valver :wink:
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The performance by using 98 would not change. The general census of opinion is that the higher the octane rating, the more performance. This is B.S. High peformance engines running high compression ratio, or turbos need higher octane ratings to reduce the risk of engine damaging detonation. If you have a normal engine for the average family car, then 95 is adequate. But for our Golf GTI's, although by todays standards have pretty mediocre power outputs, they are still high compression ratio engines and benefit from higher octane rated fuels.
In days of leaded petrol, tetra ethyle lead (TEL) was added to petrol to increase the octane. 100 octane which equates to about 6 or 7 star, is used for most light aircraft with 130 octane being available for high performance piston engined aircraft or high altitude planes. TEL has been replaced by another anti knock agent for todays lead free fuels.
Just about says it all :smiley:
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I find that my car is not as jerky/shaky with 97/99 ron at low speeds (pulling off/traffic)
Same here. Is this because mine's a K-Jet (doesn't have the knock sensor)?
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Yes mate, you car will be tuned to whatever fuel was in it last time the the fuel/air and timing was adjusted.
Nick
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The performance by using 98 would not change. The general census of opinion is that the higher the octane rating, the more performance. This is B.S. High peformance engines running high compression ratio, or turbos need higher octane ratings to reduce the risk of engine damaging detonation. If you have a normal engine for the average family car, then 95 is adequate. But for our Golf GTI's, although by todays standards have pretty mediocre power outputs, they are still high compression ratio engines and benefit from higher octane rated fuels.
In days of leaded petrol, tetra ethyle lead (TEL) was added to petrol to increase the octane. 100 octane which equates to about 6 or 7 star, is used for most light aircraft with 130 octane being available for high performance piston engined aircraft or high altitude planes. TEL has been replaced by another anti knock agent for todays lead free fuels.
But if your car has a knock sensor and the ECU controls the ignition advance I thought that the higher octane fuel meant that combustion is more efficient/closer to TDC - meaning that although there's no extra energy, there is a better conversion to kinetic energy?
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Well regardless of theories etc... When i run my digi on 99 ron from tesco it runs noticably better than on 95 ron stuff. I can't explain the magic behind it, i just accept it!
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i just accept that mine will be constantly pinking if i dare put 95 ron in it... :huh:
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Quote:
But if your car has a knock sensor and the ECU controls the ignition advance I thought that the higher octane fuel meant that combustion is more efficient/closer to TDC - meaning that although there's no extra energy, there is a better conversion to kinetic energy?
Higher octane fuels have a higher flashpoint temperature than the lower octane fuels. Burning efficiency does not come into it when talking about fuels. The efficiency of fuel burning depends on the shape of the combustion chamber and pistons. I built up a Chevy 350 V8 for my Cobra and went against the general consensus of opinion that I needed domed top pistons to reach the desired C/R, as the flame would need to travel around the dome, thus acheiving uneven fuel burning and retarded peak pressure, not to mention high emissions. I went for flat top pistons and changed the heads with lower cc chambers. I reached a C/R of 10.3:1 calculated, which for a large street engine is more than enough. And I was happy in the fact that I was getting complete burning and acceptable emissions. For racing applications, domed pistons will achieve the desired C/R but then fuel ecconomy ceases to become an issue.
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Higher octane fuels have a higher flashpoint temperature than the lower octane fuels.
Not quite. Higher octane fuels are more able to resist pre-ignition due to compression.
:smiley:
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With compression, you get heat. If the heat is excessive you will get spontanious combustion.
Remember when you pump up a bicycle tyre, the end of the pump gets warm...
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So even though your analogy is wrong you agree? I'm totally confused as to where this thread is going now.
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My analogy is not wrong, but I do agree, this thread is now dead.