110 octaine: engine stutter?

i would think the octane is too high for the timing you are running. if you were running a lower octane at a set tune up spec and them went to a much higher octane, you would have to advance your timing 3-5 degrees.

i am no professional ferrari tech, so i may be wrong.

 

Im not a Ferrari tech either,but the ferrari 348 uses a Motronic M2.5 ECU. It has 2 sets of ignition coil packs.One for each bank and uses a hall effect sensor on the front of the engine to trigger the spark system. The timing cannot be adjusted by you. If you use higher octane fuel,the ECU adjusts the timing to suit. Have these cars got "knock sensors"?? I had a look in my tech manual,and it doesnt mention it?? The flutter you heard,may have been the engine"pinging"(if you have ever heard of that) The ECU adjusts the timing to suit,and when the engine starts to knock/ping,the knock sensors tell the ECU to retard the timing to aviod engine damage. We dont get 110 octane rated fuel here,the best is 98RON. When i 1st got my 348,i put in 20 litres of normal 92 RON unleaded fuel,then after that was all gone,i pumped in 20 litres of 98 RON premium unleaded fuel.It was a great improvement as the ECU adjusted to the higher octane fuel. Still now,it runs awesome! Maybe 110 RON is too high a octane fuel for these cars?? If someone can help us out or correct me,that would be great! Hope i helped you out JDAVID

 

I've never ever heard of too much octane causing a problem...except of course in your wallet.

It may be the particular fuel you chose. Some racing fuels are oxygenated which increases power, but also increases the fuel flow rate required...so you need to re-tune the engine to run properly on them. If you dump that stuff in an engine that has not been tuned for it, it will run lean which could explain the flutter you had.

 

My experience in a different car is that running race gas makes the car run very rich. I had a 39 ford with a blown 383 that was tuned for 91 octane. I put in 110 race gas and it was puking black smoke and fouled the plugs. I put back in regular gas, cleaned the plugs and it was fine. My guess is ferrari is the same way.

 

the basics are this, the higher the octane the harder it is to ignite. when running high compression lower octane can ignite before the spark causing pre-detonation, this is bad. when running boost the same problem can arise, the goal is to have a fuel that will not pre-ignite but ignite and burn completely with the spark creating the flame front. so getting the right octane is critical for peak power.
dumping in high octane with out knowing how your engine runs can cause a drop in power and other problems. to low of an octane will cause 'pinging' or pre-detonation this is worse as it tends to damage parts.

you'll need to factor in your dynamic compression ratio, static isn't really helpfull here. so you'll need to know your timing events, cam profile, valve size, bore stroke, etc... or blueprint your motor than you'll know excatly where to start and how to modify timing, fuel etc...not trying to be a pain but using the right fuel is happenstance but a calculated factor. you can even get into the temp of the coolant and its water passages to effect power and running.

basicly what works best is to run the lowest octane needed as that will burn completly and with the best charge.

 

Just went through this exercise on my Mondial t which is a 348 drivetrain.

The Motronic 2.5 pinout has both knock sensor and octane adjust inputs, true. BUT: the 348 does not have knock sensors nor a switch for octane; this I know for sure. I am 90% sure that the ECU is not programmed to respond to either input even if you did have the sensors/switches in place.

Higher octane fuel prevents, not promotes, predetonation.

 

does running gas that has lower or higher octane that engine requires affect engine temperature???

 

Where did you buy it? Because if they don't sell a lot of the 110 gas, what they have in the ground may be old and even have water in it...I alternate either 100, 107 and 110 gas in my BB512i all the time and it makes the engine run smoother and feels like it has a little more get-up-and-go...

 

There are less BTU's of energy in higher octane fuels, so its possible there could be some reduction in temperature just because there is less "heat" in the fuel, but I think it would be negligible.

 

Unless there is a higher compression ratio than stock, I don't think its possible for it to have more get up and go. My experience has been that lower octane fuels run smoother - they are easier to ignite and they have more energy in them, so a lower octane fuel will make (slightly) more power but run a bit hotter - so long as it doesn't detonate.

 

Dude,i have to disagree with you i think. From my experience,with alot of cars,including my ferrari,the higher octane fuels kick ass! With the normal 92 RON fuel i was putting in,even with a fuel additive(that gives you around 2-3 ROn points,apparently) did not compare to the 98 RON fuel!! The car makes more power with the higher octane fuel. Of course its more expensive,but who cares?? Ill happily run mine on the fuel forever. As for the flutter,whatver it was,maybe parkerfe is correct. Maybe the fuel in the tank at the servo,has gone stale/with water in it? With high fuel prices,maybe no ones buying it and its the same old **** in the tank for many many months. Which has now got a way lower octane rating cause it has been in the tank for a long time. One such case is my friends dad owns a servo,out of town and he has the premium fuel and he tells me not to use it,because the fuel is so old,i wont get any benefits out of it. No one out there buys the fuel,so it sits in the tank for years and goes off! A waste of good go-go juice! hehe

 

Of course, the assumption is that this was an automotive fuel and not aviation. The old addage about high octane being hard to ignite is pretty much the case here. We call it the Driveability Index which takes into account octane, vapor pressure (how easily the fuel evaporates), etc etc to calculate a number that relates to how easy a fuel is to ignite. It's likely the car didn't start that well with that 110 octane as well (or, of course, the engine could be calibrated fat enough on startup that it was immune). High DI fuels present the most challenge at startup/run transition, but are next noticeable on tipins. No need to use more than the car knocks for!

P.S.- Unless there are other blending differences from your supplier, high vs low octane won't produce noticeable power differences in a non knock-sensor equipped car.

 

98ROM in AU is about 93 in the US if I'm not mistaken. AU 92 is our 86-87 and way too low for a 348...although a 308QV likes it just fine.

 

Good point on the Aviation gas...it has stuff to prevent freezing and vapor lock and the engine will be lean on it if I recall correctly.

 

Really?? Didnt know that. I guess ill stay in Australia then! LOL

 

We use RON+MON/2, same gas, different number on the rating. 91-93 is our premium and about 98 RON.

 

Too easy!