Toymods Car Club
www.toymods.org.au
F.A.Q. F.A.Q.    Register Register    Login Login    Home Home
Members Members    Search Search
Toymods » General Car Talk » Higher RON Fuels: Did you know?

Show: Today's Posts  :: Show Polls 
Email to friend 
Switch to threaded view of this topic Create a new topic Submit Reply
AuthorTopic
Matt-itude
Regular


Location:
Perth, Western Australia
Registered:
October 2004
Higher RON Fuels: Did you know? Sun, 12 June 2005 09:11 Go to next message
This came to my attention the other day,

There is no difference in the calorific value of the different types of RON fuels. This means there is no internal engergy difference between BP Ultimate 98 and normal pump fuel.

So if you dyno'd BP Ultimate vs. Regular Unleaded on a stock car there really shouldn't be a difference in torque or power output.

The advantage to using a high RON fuel comes in with it having a higher flash point, or a resistance to detonation. This means engines can be run with a higher compression ratios, and can advance the timing to the limit of detonation, and produce much higher peak pressures and temperatures in the combustion chamber which will increase the thermal efficiency, and therefore increase overall torque and poer, compared to regular unleaded.

Better performance from BP ultimate? All things staying the same, i don't think so.

[Updated on: Sun, 12 June 2005 09:22]

  Send a private message to this user    
justcallmefrank
Forums Junkie


I supported Toymods

Location:
Perth
Registered:
May 2002
 
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 09:15 Go to previous messageGo to next message
Matt-itude wrote on Sun, 12 June 2005 17:11

Better performance from BP ultimate? All things staying the same, i don't think so.

Actually, with an older car, all things being the same, power should probably go backwards, but fuel economy may go up on cruise. On a newer car which is constantly sampling the knock sensor, it should adjust for the increased octane.
  Send a private message to this user    
Matt-itude
Regular


Location:
Perth, Western Australia
Registered:
October 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 09:34 Go to previous messageGo to next message
justcallmefrank wrote on Sun, 12 June 2005 17:15

Matt-itude wrote on Sun, 12 June 2005 17:11

Better performance from BP ultimate? All things staying the same, i don't think so.

Actually, with an older car, all things being the same, power should probably go backwards, but fuel economy may go up on cruise. On a newer car which is constantly sampling the knock sensor, it should adjust for the increased octane.


but with the timing adjustment, thats not all things staying the same is it?
  Send a private message to this user    
justcallmefrank
Forums Junkie


I supported Toymods

Location:
Perth
Registered:
May 2002
 
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 09:36 Go to previous messageGo to next message
Depends how you're looking at it, base timing isn't being affected at all.
  Send a private message to this user    
GBC_069
Regular


Location:
Upper Northshore, Sydney
Registered:
October 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 10:00 Go to previous messageGo to next message
coming in at 115.9L a litre i dont bother, 98 octane wasnt around when our cars came out was it ?? (correct me if i am wrong here, jus guessing) , so technically, use unleaded!

would buying an octane booster seperate fix this problem, or is it identical to ultimate ?

nick
  Send a private message to this user    
justcallmefrank
Forums Junkie


I supported Toymods

Location:
Perth
Registered:
May 2002
 
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 10:02 Go to previous messageGo to next message
Octane boost could bring premium unleaded close or to the level of Ultimate 98, but it still wouldn't be the same. I've wound some more timing into my RA60 and it lives on a diet of Ultimate, and the fuel economy savings are more than paying for the difference in price with a teeny increase in power.
  Send a private message to this user    
river
Forums Junkie


Location:
Land of Oz
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 11:07 Go to previous messageGo to next message
Hi,

Matt-itude wrote on Sun, 12 June 2005 19:11

The advantage to using a high RON fuel comes in with it having a higher flash point, or a resistance to detonation. This means engines can be run with a higher compression ratios, and can advance the timing to the limit of detonation, and produce much higher peak pressures and temperatures in the combustion chamber which will increase the thermal efficiency, and therefore increase overall torque and poer, compared to regular unleaded.

Better performance from BP ultimate? All things staying the same, i don't think so.


The first paragraph above you admit to high RON increasing the thermal efficiency and increase the overall torque and power in a high compression engine. Yet, in your next paragraph you say there is no improvement in performance. Confused

My engine is a high compression, and it performs much better on Ultimate than it does with Premium, and it just doesn't like standard ULP at all.

Then again, my old clunker doesn't have an ECU, or any other fancy gizmo to auto-adjust the timing or other parameters.

seeyuzz
river
  Send a private message to this user    
ae86drift
Forums Junkie


I supported Toymods

Location:
sydney.au
Registered:
August 2002
 
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 11:32 Go to previous messageGo to next message
my car wont run on the other fuels
98 ron only
its tuned for it in japan

strange
Smile
  Send a private message to this user    
thu187
Forums Junkie


Location:
Sydney
Registered:
September 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 12:23 Go to previous messageGo to next message
Why is it that some cars (for example) are rated 400hp on regular and 550hp on premium?
Anyway like river said you've said it increases power, efficiency and torque. Doesn't that mean improved performance?

Not having an rpm tacho I listen to my engine in deciding when to change. When I use premium I change gears later. ie. I start to get a loudish noise at 25 on regular unleaded but I don't hear that noise till 40km/h on premium. I do have more torque when I use it.
  Send a private message to this user    
TRD_Supra
Forums Junkie


On Probation

Location:
Hobart
Registered:
December 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 13:35 Go to previous messageGo to next message
would it matter running premo to just stock ULP ? would it do hte engine any harm at all ? or u reckon it would just ping more etc etc..
i have a full tank of premo with nulon octane booster and i can't really tell if it gets any more overall performace !! it just feels the same as premo without octane booster in it!
  Send a private message to this user    
no_tofu_speed
Forums Junkie


Location:
Newcastle
Registered:
August 2003
Jab what?!!?!
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 14:09 Go to previous messageGo to next message
..pinging is not good...
  Send a private message to this user    
TRD_Supra
Forums Junkie


On Probation

Location:
Hobart
Registered:
December 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 14:48 Go to previous messageGo to next message
well i found a cheapest place to get premo for $1.13 that 2c cheaper than else where! but ulp is 1.09, but i spose for an extra 1 dollar u can get a full tank of premo compared to a full tank of ULP!! so i am more than happy to pay $1 for the difference in quility and more km's per tank!
  Send a private message to this user    
Matt-itude
Regular


Location:
Perth, Western Australia
Registered:
October 2004
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 18:40 Go to previous messageGo to next message
river wrote on Sun, 12 June 2005 19:07

Hi,

The first paragraph above you admit to high RON increasing the thermal efficiency and increase the overall torque and power in a high compression engine. Yet, in your next paragraph you say there is no improvement in performance. Confused

My engine is a high compression, and it performs much better on Ultimate than it does with Premium, and it just doesn't like standard ULP at all.



Matt-itude wrote on Sun, 12 June 2005 19:11

The advantage to using a high RON fuel comes in with it having a higher flash point, or a resistance to detonation. This means engines can be run with a higher compression ratios, and can advance the timing to the limit of detonation, and produce much higher peak pressures and temperatures in the combustion chamber which will increase the thermal efficiency, and therefore increase overall torque and poer, compared to regular unleaded.



I think you have misread what i have written.

Higher RON Fuels give an engine the capacity to achieve higher power output by increasing peak pressure and temperature inside the combustion chamber, which increases thermal efficiency.

I.E. More energy from the fuel is converted into engine power.

My point was, higher octane fuels don't have anymore "potential energy" than lower octane fuels, but they let engines run with higher compression ratio's and more advanced timing, before the onset of detonation, which creates more power and better performance as per the reasons above.

River - This is probably why your engine runs much better on 98 RON fuel, as the engine would be tuned for it, and running on lower octane fuel would most likely cause detonation, or pinging, which is certainly not good for power or the lifespan of your engine.

If your car runs perfectly fine with no detonation on 91 RON, then putting a tank full of higher octane fuel will not do anything for performance. IF NO OTHER MODIFICATIONS ARE DONE

So i stand by my statement:

Matt-itude wrote on Sun, 12 June 2005 19:11

Better performance from BP ultimate? All things staying the same, i don't think so.
  Send a private message to this user    
Corona RT142
Forums Junkie


Location:
Campbelltown
Registered:
November 2003
Re: Higher RON Fuels: Did you know? Sun, 12 June 2005 23:52 Go to previous messageGo to next message
performance is not the only reason you run 98 ron fuels for, they also have detergents in them that aim at keeping engines clean, Bp ultimate for one is cleaner burning which means less carbon deposits in the engine which one means less wear and two better performance in the long run.
Meh the rona needs the good petty anyway being an 85 model and i only run ultimate now, cos i wasn't happy with economy and response with shell optimax. Note i actually get better economy and it seems more responsive on Shell LRP than on optimax. But ultimate still beats both.
Ultimate ends up paying for itself with the better economy so i run it and i need a minimum of premium anyway so its worth the extra.

But in a recent study of BP witnessed by motor mag testing Bp unleaded vs ultimate testing even basic cars like an echo and a camry, not only did economy improve but acceralation and top speed over a standing kilometre improved marginally.
  Send a private message to this user    
TRD_Supra
Forums Junkie


On Probation

Location:
Hobart
Registered:
December 2004
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 02:07 Go to previous messageGo to next message
is there any difference in the 98 ron fuels or they pretty much the same over all the companies... we don't even have 98 ron fuel here in tassie!! but we are getting it soon!!!
  Send a private message to this user    
Arch
Forums Junkie


Location:
Adelaide
Registered:
January 2004
 
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 02:38 Go to previous messageGo to next message
Look, when u find something good, u stick with it

Ultimate all the way baby Wink
  Send a private message to this user    
Corona RT142
Forums Junkie


Location:
Campbelltown
Registered:
November 2003
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 03:01 Go to previous messageGo to next message
there is another rating of fuel Mon and this differs a fair bit between optimax and ultimate. Basically ron is how a petrol performs in the lower area of the rev range whilst mon is for higher rev applications. Hence why Bp ultimate which has a higher mon rating works much better with high peformance engines.

My fuel economy on Bp ultimate ranges between 12-15L per 100km and have seen as low as 10L per 100km when i drove to Goulbourn and back. When i used to use optimax the best i could get was between 15-18L per 100km
  Send a private message to this user    
jeffro RA28
Regular


Location:
Tamworth
Registered:
August 2004
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 03:48 Go to previous messageGo to next message
In my race bike all i run is BP ultimate. It will run much cleaner and crisper and when it gets its periodic 10 hours of racing rebuild the combustion chamber and top of piston is clean! Thats running 32.1 motul premix aswell.

Alot of us moto x racers steer clear of optimax because of its bad record with engine failure with 2 strokes.

Not that this is relavant to cars but it tells me that BP ultimate is a better fuel all round.
  Send a private message to this user    
river
Forums Junkie


Location:
Land of Oz
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 05:40 Go to previous messageGo to next message
Hi,

Matt-itude wrote on Mon, 13 June 2005 04:40

If your car runs perfectly fine with no detonation on 91 RON, then putting a tank full of higher octane fuel will not do anything for performance. IF NO OTHER MODIFICATIONS ARE DONE

So i stand by my statement:

Matt-itude wrote on Sun, 12 June 2005 19:11

Better performance from BP ultimate? All things staying the same, i don't think so.



Technically, your statement is not correct. As evidenced by the posts in this thread there are those among us who do get improved performance in running 98RON (ie Ultimate, etc) in our engines.

Your statement would be more accurate if it was "98RON has the same power potential (or words to that affect) as 95 or 91RON"

Or, better still... "98RON fuel won't give you anymore power in your engine if your engine is designed and tuned to run 91RON"

Even then, I'm sure there are people who have 91RON-tuned engines and have found their motors running better on 98RON.

But a blanket statement such as "Better performance from BP ultimate? All things staying the same, i don't think so." is simply wrong. Unless you add the disclaimer that this statement is only applicable to lower compression 91RON-tuned engines.

As I mentioned earlier, my car pings it's butt off on 91RON. It pings less on 95RON, and it sings sweetly on 98RON. So, all things being equal (ie same engine, no or tune-ups between refills, etc), 98RON (Ultimate) does offer me better performance.

You said that 98RON has the same "potential energy" as 91RON, however it's the "kinetic energy" that actually provides the power to drive your engine, and in this regard the 98RON is superior to 91RON, specifically in a higher compression engine.

seeyuzz
river
  Send a private message to this user    
Toobs
Forums Junkie


I Supported Toymods

Location:
Sydney
Registered:
December 2002
 
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 05:53 Go to previous messageGo to next message
Higher RON fuels have a higher flash point and therefore are less likely to preignite.

This means that timing can be further advanced and boost can be increased over lower RON fuels without preignition.

People run higher RON fuels for different reasons:
1) Increase ignition advance
2) Increase boost
3) Increase safety margin before preignition.
4) Cleansing properties associated with the higher RON fuels.
  Send a private message to this user    
river
Forums Junkie


Location:
Land of Oz
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 06:12 Go to previous messageGo to next message
Hi,

Good points Toobs. But I got to add one more... 98RON smells better also. I can get more "highs" per cc of 98RON than your normal ULP. Razz

seeyuzz
river
  Send a private message to this user    
CLG
Forums Junkie


I supported Toymods

Location:
Perth, Western Australia
Registered:
December 2002
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 06:17 Go to previous messageGo to next message
Matt-itude wrote on Sun, 12 June 2005 17:11

Better performance from BP ultimate? All things staying the same, i don't think so.


I look at it this way:

You can have a killer blonde in bed who's dynamite in the sack - but if you don't know what you're doing, you're never going to blow the blonde away - in more ways than one!?!
  Send a private message to this user    
Toobs
Forums Junkie


I Supported Toymods

Location:
Sydney
Registered:
December 2002
 
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 06:28 Go to previous messageGo to next message
river wrote on Mon, 13 June 2005 16:12

Hi,

Good points Toobs. But I got to add one more... 98RON smells better also. I can get more "highs" per cc of 98RON than your normal ULP. Razz

seeyuzz
river


Jesus river... now everyone will think you're a stoner and a petrol sniffer Very Happy
  Send a private message to this user    
CLG
Forums Junkie


I supported Toymods

Location:
Perth, Western Australia
Registered:
December 2002
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 06:42 Go to previous messageGo to next message
Toobs wrote on Mon, 13 June 2005 14:28

river wrote on Mon, 13 June 2005 16:12

Hi,

Good points Toobs. But I got to add one more... 98RON smells better also. I can get more "highs" per cc of 98RON than your normal ULP. Razz

seeyuzz
river


Jesus river... now everyone will think you're a stoner and a petrol sniffer Very Happy



I've only met him once - that was my impression too!!! Razz
  Send a private message to this user    
river
Forums Junkie


Location:
Land of Oz
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 06:54 Go to previous messageGo to next message
Hi,

Don't forget glue-sniffer, permanent marker pen sniffer, paint sniffer, womens panties sniffer.....

Ahhh, gee thanks for that Clint. So long as I don't look like a piggy-eyed child beater I s'pose I can't complain. Confused

But, this is all OT, and any further derogatory or smart aleck comments should be PM'd or put into the appropriate thread. Wink

seeyuzz
river
  Send a private message to this user    
bmews
Occasional Poster


Location:
Mt Colah NSW
Registered:
March 2005
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 11:12 Go to previous messageGo to next message
Actually there is more energy in the 98RON fuels currently being marketed by Shell,BP, Mobil and Caltex. I did a survey some months ago and found that their density is somewhat greater than regular ULP hence greater energy per unit volume. Some of the above company's have the density stated on their web sites and other I sent an email and got a response.

So there is a technical reason why there should be a greater fuel economy when using these fuels but older engines will probably need to have their timing advanced to take full advantage of the higher RON. Most EFI engines only have passive knock sensors and will retard timing should they detect any knock, some higher performance vehicles do have active knock sensing and will advance timing to take advantage to better fuels.

[Updated on: Mon, 13 June 2005 11:13]

  Send a private message to this user    
Rainey
Regular


Location:
Hobart, Tasmania
Registered:
January 2005
Re: Higher RON Fuels: Did you know? Mon, 13 June 2005 13:35 Go to previous messageGo to next message
I don't claim to know my sh*t but I agree with what Matt-titude is saying. If the petrol is firing correctly on regular unleaded then increasing the RON isn't going to make the engine more powerful until you modify the timing to take advantage of the cleaner detonation. However the cleaner fuel may decrease engine wear and increase efficiency.
  Send a private message to this user    
bmews
Occasional Poster


Location:
Mt Colah NSW
Registered:
March 2005
Re: Higher RON Fuels: Did you know? Tue, 14 June 2005 02:30 Go to previous messageGo to next message
For those interested here are the fuel density figures I gathered late last year. They predate the Vortex98 so only reflect the Vortex95.

It would appear that Caltex/Ampol have the highest density ULP while Shell and Mobil the best 98. Offcourse they could all change without notice.

ULP/ 98RON
Shell 0.735/ 0.76
Mobil 0.72/ 0.76
BP 0.735/ 0.755
Caltex 0.74/ 0.75 (95RON)

Cheers,
Barry
  Send a private message to this user    
towe_001
Forums Junkie


Location:
Somewhere on a dirt bowl ...
Registered:
August 2004
Re: Higher RON Fuels: Did you know? Wed, 15 June 2005 00:02 Go to previous messageGo to next message
CLG wrote on Mon, 13 June 2005 16:42

Toobs wrote on Mon, 13 June 2005 14:28

river wrote on Mon, 13 June 2005 16:12

Hi,

Good points Toobs. But I got to add one more... 98RON smells better also. I can get more "highs" per cc of 98RON than your normal ULP. Razz

seeyuzz
river


Jesus river... now everyone will think you're a stoner and a petrol sniffer Very Happy



I've only met him once - that was my impression too!!! Razz


Now you've really got my imagination ticking over on images of an old geeser that looks like a mad scientist type bashing away on an old clunker of a computer Surprised Very Happy lol

But anyways here's something to throw in the pot. 4age bigport 1mm over bore and the head has been skimmed to much sure its flat. It runs on ULP but if i run it on PULP or Optimax/Vortex/etc within a week the motor blows a head gasket.
  Send a private message to this user    
Shraka
Forums Junkie


Location:
Melbourne
Registered:
November 2003
Re: Higher RON Fuels: Did you know? Wed, 15 June 2005 03:12 Go to previous messageGo to next message
I run 98ron 'cuz the car runs better. The response is nicer and it actualy revs out (when on 91ron, it screams and cries if I try to rev it). Also, under load low down in the RPMs the thing pings like a bitch if I don't have 98ron in it.

Also, I find it has economy advantages, although I'm not sure why, as I have a carby.

This is on a bog stock 1991 Mitsubishi Lancer GL.
  Send a private message to this user    
trevtrev
Regular


Location:
Brisbane
Registered:
October 2004
Re: Higher RON Fuels: Did you know? Wed, 15 June 2005 03:18 Go to previous messageGo to next message
Ahh, well that proves it then. Too much powah in the 98, blows your head gasket right out!
  Send a private message to this user    
st184 sillycar
Forums Junkie


Location:
Melbourne
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Wed, 15 June 2005 09:56 Go to previous messageGo to next message
As I see it, it all depands on how "smart" your car is. older carbied, distributer ignited cars will have a minimum RON needed to avoid pinging. Feeding the old girl fuel with a higher octane rating (but the same energy density) shouldn't have a noticeable benefit. Newer EFI-run cars are a different kettle of fish. A particularly clever computer can run at near-optimum on a huge range of petrols. The GenIII for exapmle constantly adjusts ignition advance, injector duration AND injector phasing according to the conditions. This "making it up as it goes" automatically adjusts for fuel RON.

Did I mention teh GenIII calculates exhaust temp & heat-soak, to prevent cat-cooking and piston damage? Pretty good eh? - although the masses of extra fuel it dumps into the ports to keep things cool REALLY kills fuel economy wen towing big, heavy trailers. Crying or Very Sad


Stupid dumb fuel prices. Sad Crying or Very Sad
  Send a private message to this user    
st184 sillycar
Forums Junkie


Location:
Melbourne
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Thu, 16 June 2005 10:06 Go to previous messageGo to next message
Y E S ! !


Another thread killed off by ME ! ! Laughing Laughing
  Send a private message to this user    
riceburna73
Forums Junkie


Location:
Sydney
Registered:
April 2004
Re: Higher RON Fuels: Did you know? Thu, 16 June 2005 11:34 Go to previous messageGo to next message
mmm all very interesting stuff..I havent had to deal with it too much as the car has been off the road but what should I be using fuel wise for the old 2T in the celica,premium and no valve lube/anti run on stuff in the tank aswell, or will normal ULP be fine??

Sorry for the semi hijak or if this has been covered..
  Send a private message to this user    
Corona RT142
Forums Junkie


Location:
Campbelltown
Registered:
November 2003
Re: Higher RON Fuels: Did you know? Thu, 16 June 2005 22:55 Go to previous messageGo to next message
*Snake says* premium dude
  Send a private message to this user    
Norbie
Forums Junkie


Location:
Brisbane
Registered:
May 2002
Re: Higher RON Fuels: Did you know? Fri, 17 June 2005 00:52 Go to previous messageGo to next message
My old 2T was perfectly happy on plain old ULP, but if you run PULP you can bump up the ignition advance and get a bit more powah.
  Send a private message to this user    
THE WITZL
Forums Junkie


Toymods Social Secretary

Location:
Sydney
Registered:
July 2002
 
Re: Higher RON Fuels: Did you know? Fri, 17 June 2005 03:50 Go to previous messageGo to next message
just a side note for those of us with imported engines..... the shittiest Japanese petrol is 96ron. They have up to 105ish RON as their "ultimate" pump fuels. Most factory imported jap engines are tuned for the higher grade 100ron fuels (most mid 1989 engines onwards).

Hence for this very reason i only ever run my 1UZ-FE with 98ron. If i had a scan tool i could probably show you the difference in knock sensor outputs from the use of both ULP and PULP.
  Send a private message to this user    
st184 sillycar
Forums Junkie


Location:
Melbourne
Registered:
June 2004
Re: Higher RON Fuels: Did you know? Sun, 19 June 2005 01:09 Go to previous messageGo to next message
THE WITZL wrote on Fri, 17 June 2005 13:50


Hence for this very reason i only ever run my 1UZ-FE with 98ron. If i had a scan tool i could probably show you the difference in knock sensor outputs from the use of both ULP and PULP.


Ditto my GTS-T. I'll see if I can get some phone-camera pics of knock sensor feedback when I install the PowerFC
  Send a private message to this user    
trd3sg
Occasional Poster


Location:
Sydney Australia
Registered:
June 2005
Re: Higher RON Fuels: Did you know? Sun, 19 June 2005 06:44 Go to previous messageGo to next message
st184 sillycar wrote on Wed, 15 June 2005 19:56

As I see it, it all depands on how "smart" your car is. older carbied, distributer ignited cars will have a minimum RON needed to avoid pinging. Feeding the old girl fuel with a higher octane rating (but the same energy density) shouldn't have a noticeable benefit. Newer EFI-run cars are a different kettle of fish. A particularly clever computer can run at near-optimum on a huge range of petrols. The GenIII for exapmle constantly adjusts ignition advance, injector duration AND injector phasing according to the conditions. This "making it up as it goes" automatically adjusts for fuel RON.

Did I mention teh GenIII calculates exhaust temp & heat-soak, to prevent cat-cooking and piston damage? Pretty good eh? - although the masses of extra fuel it dumps into the ports to keep things cool REALLY kills fuel economy wen towing big, heavy trailers.


ok - this post along with mattitude's post seem to make the most amount of sense

as originally stated - higher RON fuels IN THEMSELVES AS A VARIABLE do not add any performance value to a motor - any performance gain realised from merely adding PULP will be due to other factors - like in st184's post - the reason for the increase in performance in later model cars is the "fuzzy-logic" ability of factory ECU's to 'learn' to cope with the driving habits - for instance, after gunning a motor at WOT for two minutes straight without knocking, the computer in most quality multi-point EFI cars will be able to vary ignition timing to take advantage of the 'atmosphere' provided by PULP which makes is less prone to detonation or preignition.

As a general rule, higher RON fuels burn slower than lower RON fuels - think of this scenario - you have advanced your static ignition timing two degrees - what does this practically involve - the moving forward in time of the spark before a given point of the motor's cycle at IDLE - ie, lets say 10 deg btdc - your dizzy\coil\cas\computer (ignition triggering device) will send a spark to the relevant cylinder 10 degrees on the crank before your respective piston reaches top dead centre on its COMPRESSION stroke, - ie, you are bringing it forward - now as a motor increases its rpm, then the 'window' of opportunity to induce the spark at the correct time becomes much smaller - thus why mechanical or electronic advance is used to advance the timing in increments as the revs increase - BUT THIS CAN ONLY BE DONE TO A CERTAIN POINT - the advantages of this are well documented, in that by the time the ignition actually starts in the combustion chamber the piston has completed its compression stroke and will be on its way down with a greater force due to 'perfecting' the timing - pinging exists for one of two reasons -
1. either the fuel is burning way too quickly (because of its lower RON, ie. quicker burn compared to the slower burn of the higher RON fuel) and thus the 'explosion' is happening way too far in advance and is therefore exerting a force against a mass of metal (piston) moving in the opposite direction to the force (not good).

AND\OR

2. Hot spots in the combustion chamber causing the fuel to ignite before its peak compression\timing period or before the spark is actually delivered to the cylinder (hot spots can come from ridges, faulty plugs, gunk in the combustion chamber, faulty valvetrain system etc etc) - this has the same effect as fuel burning too quickly and will be pushing down against the piston moving up to complete its compression stroke (the piston can't exactly stop in its tracks [by virtue of the mechanical rotating mass structure] and if the force of the explosion\ignition is stronger than the force of the piston somehow, then you WILL have a shattered piston guaranteed) - now if a motor's compression ratio has been increased from a standard 8.0:1 to say 10.5:1, without even altering ignition timing or fuel values at all - this may provide an atmosphere for detonation, simply from the greater compacting of the fuel, which (due its slower burn being a lower RON fuel or due to hotspots) will in itself put undue heat\force unexpected into the combustion chamber and the fuel will ignite on its own from the pressure before the spark is even delivered.

and that is what the tick tick tick or thud thud thud sound is

Now - in taking the above into consideration, if a car is fitted with a knock sensor, which tells the computer when a motor is preigniting so as to reduce ignition timing accordingly, then the performance effectively will reduce if a lower RON fuel is used than that perscribed for the motor - ie a car happily running on 95 RON fuel may ping with 91 RON due to the standard ignition and fuel values, meaning the knock sensor will tell the ecu to retard timing and this equates to reduced performance for the sake of saving the motor from preignition and possible failure

but a carb motor with points dissy and no ecu will not benefit from a change in fuel types alone - unless the motor was pinging on the fuel used previously

IT MUST BE REMEMBERED THAT PINGING IS NOT ALWAYS AUDIBLE, ACTUALLY BY THE TIME THAT IT HAS BECOME AUDIBLE THEN IT IS QUITE SERIOUS and the consequences of this audible detonation are scuff marks, piston ring land damage and other physical piston damage, as well as possible damage to all other parts in the combustion chamber (chamber, valves, plug, gasket) and in the long term, engine failure due to smashed pistons or rings.

so taking the above into account - have a logical think about fuel values and whether one variable IN ITS OWN RIGHT can alter the performance of a motor so dramatically, and gauge this thought in line with the fundamentals of a four stroke motor

Mick


  Send a private message to this user    
jeffro RA28
Regular


Location:
Tamworth
Registered:
August 2004
Re: Higher RON Fuels: Did you know? Tue, 21 June 2005 11:52 Go to previous messageGo to next message
Picture this. A flame is ingited prematurely from a hotspot on the far point of the combustion chamber, this flame will then travel towards the spark plug. Whilst the flame is travelling towards the spark. The plug ingites the remaning fuel mixture(on time). The second flame front meets the first causing an extremely high rate of pressure rise.

Detonation can lead to pre-ignition because of the increased surface temps in the chamber. They work hand in hand, one leads to another.

When these flame fronts meet, this is when u may hear a kock or "ping". Or when then the flame front meets the walls of the combustion chamber. Depending on the severaty, u may or may not here a ping.

Remember detonation occurs after the spark plug has ignited its mixture and pre igntion occurs before the mixture is ignited by the spark plug.

Hotspots(causing pre ignitiong)can also occur from overhanging gaskets and Overhated valves

Detonation will only occur when the PRESSURE and TEMPERATURE in the chamber reaches a point where it ignites the remaining gas in the cylinder instantaneously.

Basicly wat trd3sg said but in a bit more detial
Not really on topic, but i hope it helps to give some people a little more understanding.

[Updated on: Tue, 21 June 2005 11:53]

  Send a private message to this user    
Nark
Forums Junkie


Location:
Cabramatta, NSW
Registered:
May 2002
      Nark@toymods.net/Work
icon4.gif  Re: Higher RON Fuels: Did you know? Wed, 22 June 2005 08:14 Go to previous message
Don't forget about MON!
http://forums.toymods.org.au/index.php?t=msg&t h=58333
  Send a private message to this user    
  Switch to threaded view of this topic Create a new topic Submit Reply
Previous Topic:2T extractors!
Next Topic:Helmets and safety gear... what and where to buy in Melbourne
Goto Forum:
-=] Back to Top [=-

Current Time: Sun May 5 01:35:30 UTC 2024

Total time taken to generate the page: 0.0096850395202637 seconds

Bandwidth utilization bar

.:: Contact :: Home ::.

Powered by: FUDforum 2.3.8
Copyright ©2001-2003 Advanced Internet Designs Inc.