high octane content petrol
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  1. #1
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    Default high octane content petrol

    after reading a thread on this board, i decided to try filling my 504 with high octane petrol to try and get rid of the pinging that was ocurring when accelerating at low revs, and it worked!

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    can someone explain why this is the case, because when we did thermo-fluids 1 uni, im pretty sure our lecturer said that unless your car is a high performance car with a high compression ratio the octane rating doesnt really matter that much, because the mixture is not able to reach the high enough temperatures/pressures required to burn all of the octane anyway..

    im pretty sure that it was something like that, it was about 2 and a half years ago so i might be remembering it wrong..

    anyway, im just curious as to why it works is all..

    cheers

  2. #2
    bob
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    G'day,

    real life is different to uni.....

    Reckon that's not all to do with motor supposed C/R. There'll be squish factors, swirl, crap build-up, all sorts of gear that will affect the effect of the more expensive petrol.

    FWIW, we have found on all cars experienced using the "higher grade" juice, better running and better economy.

    cheers,
    Bob

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    Quote Originally Posted by guskenny83 View Post
    after reading a thread on this board, i decided to try filling my 504 with high octane petrol to try and get rid of the pinging that was ocurring when accelerating at low revs, and it worked!

    can someone explain why this is the case, because when we did thermo-fluids 1 uni, im pretty sure our lecturer said that unless your car is a high performance car with a high compression ratio the octane rating doesnt really matter that much, because the mixture is not able to reach the high enough temperatures/pressures required to burn all of the octane anyway..

    im pretty sure that it was something like that, it was about 2 and a half years ago so i might be remembering it wrong..

    anyway, im just curious as to why it works is all..

    cheers
    By now most 504's have probably had there heads machined a couple of times so you might find your CR is up over standard.
    David Cavanagh

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  4. #4
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    The 504 is not designed for low octane fuel, leaded was 97 octane and this is what was reccommended.
    Modern cars can use 91 octane because of advances in engine design.
    The 504 engine dates back to 1960 and the same basic design started in 1948!
    Graham

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    thanks for that, real life is indeed different to uni..hehe

    just started a job doing detail drafting and 3d modelling at a manufacturing company in coburg and the difference in accuracy/efficiency is quite a bit to get used to compared to uni!

    thanks for the info, ill continue using the higher octane fuel in the 504.. does that change anything to do with the amount of valve saver fluid i have to put in?

    cheers

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    Quote Originally Posted by guskenny83 View Post
    thanks for that, real life is indeed different to uni..hehe

    just started a job doing detail drafting and 3d modelling at a manufacturing company in coburg and the difference in accuracy/efficiency is quite a bit to get used to compared to uni!

    thanks for the info, ill continue using the higher octane fuel in the 504.. does that change anything to do with the amount of valve saver fluid i have to put in?

    cheers
    I don't believe that valve saver stuff is worth the money. I've been driving old cars forever and so has my family, never used it and never had a valve problem. My 403 with over 1 million miles has never used it, my brother never uses it in his old Renaults and never had a problem. Maybe needed on old cast iron heads like Holdens and Fords but with our alloy heads with already hard stem seals its a waste of money. Thats my opinion anyway.

    Interesting what your saying about uni, my father was a chief engineer and often had to deal with people fresh out of uni and he used to tell them that there in the real world now and before they can learn anything the first thing they must learn is the fact that they know nothing. Once they've learnt that he can teach them about work.
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  7. #7
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    You will get 8000km of unleaded fuel running out of a motor that has been run on leaded (the lead hangs around in the metal for that long) , then you may have problems.
    After that around town ,yes no problem, but if you do a lot of 110km crusing over long distances you will additive.
    Where you really need additive is if you get your original valve seats cut, this takes off the work hardening and you can get recession an a few hundred km.
    If you get the head recoed then get the hardened seats (exhaust only) fitted.
    Hard stem seals?
    Graham

    Quote Originally Posted by David Cavanagh View Post
    I don't believe that valve saver stuff is worth the money. I've been driving old cars forever and so has my family, never used it and never had a valve problem. My 403 with over 1 million miles has never used it, my brother never uses it in his old Renaults and never had a problem. Maybe needed on old cast iron heads like Holdens and Fords but with our alloy heads with already hard stem seals its a waste of money. Thats my opinion anyway.

    Interesting what your saying about uni, my father was a chief engineer and often had to deal with people fresh out of uni and he used to tell them that there in the real world now and before they can learn anything the first thing they must learn is the fact that they know nothing. Once they've learnt that he can teach them about work.

  8. #8
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    Quote Originally Posted by GRAHAM WALLIS View Post
    You will get 8000km of unleaded fuel running out of a motor that has been run on leaded (the lead hangs around in the metal for that long) , then you may have problems.
    After that around town ,yes no problem, but if you do a lot of 110km crusing over long distances you will additive.
    Where you really need additive is if you get your original valve seats cut, this takes off the work hardening and you can get recession an a few hundred km.
    If you get the head recoed then get the hardened seats (exhaust only) fitted.
    Hard stem seals?
    Graham
    Graham, all we do is highway cruising. Steve's 4cv's sit in the garage all year and only go out when there's a 4cv meeting on and will do 2000km in a single week end. Never had a valve problem, in fact, never had an engine problem.

    Strangely enough the only cars I've ever had a valve problem with are the newer ones (95 Laguna and 89 Mi16) Never an oldie so your choice but I'm confinced its a waste of money.

    My 403, after 1 million miles, 800,000 before on its first set of rings and all highway speeds, never used aditives.
    David Cavanagh

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    The 403 would not have have done 8000km after leaded fuel dissapeared?
    We had a lot of cars in the 2003 Redex Rerun with valve seat recession and I expect people to once again ignore advice regarding additives next May and have to then deal with another round of mechanical problems.
    I will say though that the majority of the cars with problems were those that had reconditioned heads but no new hardened seats.
    Graham


    Quote Originally Posted by David Cavanagh View Post
    Graham, all we do is highway cruising. Steve's 4cv's sit in the garage all year and only go out when there's a 4cv meeting on and will do 2000km in a single week end. Never had a valve problem, in fact, never had an engine problem.

    Strangely enough the only cars I've ever had a valve problem with are the newer ones (95 Laguna and 89 Mi16) Never an oldie so your choice but I'm confinced its a waste of money.

    My 403, after 1 million miles, 800,000 before on its first set of rings and all highway speeds, never used aditives.

  10. #10
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    Quote Originally Posted by GRAHAM WALLIS View Post
    The 403 would not have have done 8000km after leaded fuel dissapeared?
    We had a lot of cars in the 2003 Redex Rerun with valve seat recession and I expect people to once again ignore advice regarding additives next May and have to then deal with another round of mechanical problems.
    I will say though that the majority of the cars with problems were those that had reconditioned heads but no new hardened seats.
    Graham
    Hmm unleaded disappeared in 85, the 403 clocked over I million in late 90's so I'd say its done alot more that 8000

    Graham your probably right, most of my old car experince is with Renaults not Peugeots and even my fathers old R10 that he drove every day up until about 4 years ago never got any additives, my 403 might just be the exception to the Peugeot rule. Plus in your events there probably running on full throttle most of the time whereas I'm just putting along at the speed limit.
    David Cavanagh

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    Some of the slower cars may have been at full throttle but the events are touring between the short driving tests.
    The tropical heat may also have something to do with it.
    Leaded was phased out on the 1st of January 2002.


    Graham

    Quote Originally Posted by David Cavanagh View Post
    Hmm unleaded disappeared in 85, the 403 clocked over I million in late 90's so I'd say its done alot more that 8000

    Graham your probably right, most of my old car experince is with Renaults not Peugeots and even my fathers old R10 that he drove every day up until about 4 years ago never got any additives, my 403 might just be the exception to the Peugeot rule. Plus in your events there probably running on full throttle most of the time whereas I'm just putting along at the speed limit.

  12. #12
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    Quote Originally Posted by GRAHAM WALLIS View Post
    Some of the slower cars may have been at full throttle but the events are touring between the short driving tests.
    The tropical heat may also have something to do with it.
    Leaded was phased out on the 1st of January 2002.


    Graham
    phased out on 01/01/02?? Where? We've been using unleaded since it came in about 1985. Wish we had known we could still get unleaded.
    David Cavanagh

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    Quote Originally Posted by David Cavanagh View Post
    phased out on 01/01/02?? Where? We've been using unleaded since it came in about 1985. Wish we had known we could still get unleaded.
    Everywhere, LRP took over, then that was abandoned in the early 2000s
    Graham

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    Quote Originally Posted by guskenny83 View Post
    after reading a thread on this board, i decided to try filling my 504 with high octane petrol to try and get rid of the pinging that was ocurring when accelerating at low revs, and it worked!

    can someone explain why this is the case, because when we did thermo-fluids 1 uni, im pretty sure our lecturer said that unless your car is a high performance car with a high compression ratio the octane rating doesnt really matter that much, because the mixture is not able to reach the high enough temperatures/pressures required to burn all of the octane anyway..

    im pretty sure that it was something like that, it was about 2 and a half years ago so i might be remembering it wrong..

    anyway, im just curious as to why it works is all..

    cheers
    One of the features of higher octane fuels is they are more resistant to pre-ignition (or pinging). That's why you are experiencing the benefit.

    Dave
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  15. #15
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    You could retard your timing to run with 91

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    Quote Originally Posted by Bobomacho View Post
    You could retard your timing to run with 91
    yeah, that could have also have been the issue, when i bought the car, the guy said he had advanced the timing because he lived up in the hills and it gave him better power at low rpms.. which would probably explain why it was pinging in teh first place..

    might stick with the higher octane, seems to be running better all around since i put it in this morning..

    thanks again for all the info everyone

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