| Author | Message | ||
| Mark Eberhardt (Me_k)
Junior Member Username: Me_k Post Number: 144 Registered: 5-2002 |
I saw an article where several makes of cars were dynoed with high and low octane street gas. The result was no change. Normally you are just throwing money away running higher octane than the manufacturer calls for unless you have modified something. High compression pistons, turbos or blowers all increase the temperature in the cylinder and require a fuel that will tolerate it and burn without exploding. The higher the temperature the higher the octane that is required. | ||
| Kevin Butler (Challenge)
New member Username: Challenge Post Number: 14 Registered: 9-2002 |
Alex Trebec. I rest my case. God bless America. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 309 Registered: 8-2002 |
Peter, Still does not make up for Celine Dion. You got me on the beer though. M | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2121 Registered: 12-2000 |
Don, quiet! Don't give away our little secret!...  Current rock groups like Nickleback and Default (Vancouver-based) are doing mighty fine in the states now... No sissy hair-bands these are! | ||
| DONALD GRIESDALE (Griesdale)
Junior Member Username: Griesdale Post Number: 54 Registered: 11-2001 |
Matt and Paul, rock groups aren't my speciality so I can"t comment but we in Canada have better beer than you do and new F-cars are CHEAPER here than in the US, and we pay for them in our devalued CDN dollar!! Don. | ||
| Dave Mills (360dave)
Junior Member Username: 360dave Post Number: 75 Registered: 1-2002 |
Paul, I suppose we may be saying the same thing, and yes, it's a bit off-topic for the Ferrari board. But the LT1 PCM has a spark map which does have the maximum advance set in it, by RPM and MAP. Other than a few esoteric conditions such as warmup and EGR, this does set the maximum timing advance for that RPM. If that table is programmed for 100-octane fuel, then it'll advance up to those numbers unless it sees knock. But if those tables are programmed at 94 octane, and running at those maximums (ie, no knock), pouring in 100-octane won't change anything. That is, it would not advance timing any further. I think this is in line with what Ed first suggested. Apologies for the off-topic-ness. Dave | ||
| Edward Gault (Irfgt)
Intermediate Member Username: Irfgt Post Number: 2155 Registered: 2-2001 |
According to the General Motors manual on a 1996 Chevy Impala with an LT1 engine, the timing is advanced by the ECM in a pre programmed curve according to engine temperature, manifold air temperature, throttle position, and air flow. The Detonation sensor subtracts from the pre determined advance program until detonation is no longer present. In other words, the octane has nothing to do with advance but will cause a retard if a knock is detected. If a higher octane is introduced the advance curve will perform in it's normal programmed curve without retarding. | ||
| Paul Newman (Newman)
Member Username: Newman Post Number: 640 Registered: 12-2001 |
Dave, Im going by experience on LT1 engine programming and the circle I was involved in at the time I owned the car. I never said more power would be generated using a higher octane fuel in a car that didnt need it through more advanced timing. I said it could or would advance it until knock occured. I was running 11.5:1 compression and ran on 94 octane fuel. After monitoring the knock retard signal, I noted no knock or retard. My guess is the aluminum head combined with the reverse flow cooling system is what prevented detonation. The LT1 is very forgiving. Running 100 octane would allow the pcm to advance the timing further than if I was running 94 even though knock wasnt detected at the 94 octane fuel. My engine could take advantage of this feature in the pcm. This is an example of a pcm advancing timing contrary to what Ed has seen in his vast, dirverse and long career in the automotive field. Im not here to challenge anyone about LT1's on a ferrari site. I dont know everything about them but I know enough to talk intelligently about how pcms, fuel and ignition maps work and how to change them. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 301 Registered: 8-2002 |
Thanks Paul. How could I forget glass tiger. Aye Did you know that if a bus crashes carrying 100 people in canada killing all aboard, that same bus crash would kill 62 in America. Aye Why are they so upset about being called America Jr and Canadia? Americas come from America, Canadians come from Canadia right? And don't get me started on the funny looking money. Aye ;) AYE | ||
| Dave Mills (360dave)
Junior Member Username: 360dave Post Number: 74 Registered: 1-2002 |
"As far as an old injected ferrari goes, I wouldnt know about it but some computer controlled cars do advance timing as well as retard it" I think the point was that the PCM is programmed for best operation at a specific octane, and it's maximum advance is where it will expect to run unless it sees knock. Adding octane to a well-functioning engine (ie one without knock, in this example) won't cause the PCM to advance timing even more. So unless one re-programmed the PCM for more advance, it's unlikely the additional octane would accomplish anything. Dave | ||
| Paul Newman (Newman)
Member Username: Newman Post Number: 637 Registered: 12-2001 |
dont forget glass tiger | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 298 Registered: 8-2002 |
Don, You guys may have 94 but you still must be held responsible for Air Supply and Loverboy. M | ||
| DONALD GRIESDALE (Griesdale)
Junior Member Username: Griesdale Post Number: 53 Registered: 11-2001 |
Chevron in Canada has 94!!! | ||
| Lawrence Coppari (Lawrence)
Member Username: Lawrence Post Number: 338 Registered: 4-2002 |
I'm running 1.1 bar boost on my Porsche turbo - close to 16 psi but have the orifice to run 1.2 bars boost. However, the company that sold me the go-fast parts says I need racing fuel for the 1.2 bars to get the benefit. Lots of track junkies put the higher octane in for track events. The old beast has 137K on the clock. I think 1.1 bars is enough. | ||
| Jim Glickenhaus (Napolis)
New member Username: Napolis Post Number: 15 Registered: 10-2002 |
In my 1931 Deusenberg you can both retard and advance the timing as you motor along. As 1931 fuel was unleaded 45 octane it runs fine on todays fuels. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 296 Registered: 8-2002 |
The OM for the 78 308 calls for 93. In California at least, only 91 is available. Would a octane boost help? or should I put the cash in the major service fund? | ||
| Paul Newman (Newman)
Member Username: Newman Post Number: 634 Registered: 12-2001 |
Fords pcm's advance timing in 1 degree incriments and until knock is detected and retards in 4 degree incriments. When I recalibrated my 94 Z28's pcm after extensive engine modifications, I could watch the pcm advance the timing as well as the knock retard signal. I would then assume that if it didnt see knock with a higher octane that it would advance it until knock was seen unless it exceeded its ignition map and stopped. As far as an old injected ferrari goes, I wouldnt know about it but some computer controlled cars do advance timing as well as retard it. | ||
| Edward Gault (Irfgt)
Intermediate Member Username: Irfgt Post Number: 2152 Registered: 2-2001 |
My old Turbo Corvair is a prime example. It runs better on the higher octane stuff as detonation is a big problem on a car that runs a cylinder head temp of over 400 degrees. It has a normal 8.5 to 1 compression ratio without boost that regular fuel would easily satisfy, but when you mash the go pedal, it goes to over a 12 to 1 compression. When the boost comes in and you need all the octane you can get. | ||
| Ernesto (T88power)
Member Username: T88power Post Number: 830 Registered: 2-2001 |
On turbo cars high octance fuel will provide a huge benefit - as well as allow you to crank up boost if you have the proper air/fuel upgrades. Ernesto | ||
| Edward Gault (Irfgt)
Intermediate Member Username: Irfgt Post Number: 2150 Registered: 2-2001 |
I don't know of any car that will advance the timing to suit the fuel. It can retard the timing but not advance it. If you are not having any spark knock problems or vapor lock issues then higher octane is a waste of money and in some cases can hurt performance. | ||
| Lawrence Coppari (Lawrence)
Member Username: Lawrence Post Number: 335 Registered: 4-2002 |
My 9 year old 400E has 11:1 compression ratio. Perhaps I should try it. Wonder if the electronics has enough sense to bump the timing, etc.... | ||
| Marq J Ruben (Qferrari)
Junior Member Username: Qferrari Post Number: 114 Registered: 2-2002 |
My last sports car had 11:1 compression ratio. If you DIDN'T run 100-105 octane, it ran as if it was out of tune. When using the high octane gas, it sang a beautiful song. Magoo is right on; unless you've got a high compression engine, it'll make little/no difference. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3263 Registered: 2-2001 |
As you probably know it depends on the compression ratio of your vehicle. The higher the comp. ratio the better it will perform with a higher octane fuel. I have tried 105 octane fuel several times in my 79 308 GTS and did not notice any difference in performance compared to using regular fuels. Of course the 308 comp. ratio is 8.8 to 1 so using a high octane is a waste. | ||
| JPR22 (Cavallini)
New member Username: Cavallini Post Number: 10 Registered: 6-2002 |
In the otherwise worthless long-term review by Edmunds of the 550 M I noticed one nugget. Next month they plan to put 100 octane gas in the tank to maximize performance. Anyone had any experience or insight with 100? |