regular Unleaded or superunleaded ??

Premium, such as it is these days. Especially with the autobox as the engine is more likely to be lugging in a too high gear ratio.

 

When new 4* or 98+ was specified so it seems fair to give the engine as close as possible to what it was designed for which seems as good as reason as any to stick with super unleaded

 

What Ross was referring to is that with an auto gearbox, the tranny tends to upshift sooner than it should wth the V-12 ...dropping the RPM's to a lower level than desired. In a sense, lugging it...& loading up the cylinders with carbon.
Whereas with the 5-speed, you control when to shift up to the next higher gear. And the tendency here is to take it to a higher RPM before shifting, I generally take my 5-sp to 5K rpms before shifting. In an automatic, that's hard to do without putting the hammer down...especially in traffic.
By manually shifting the auto tranny, you are able to take it to higher R's but I've heard that's not good to do all the time with an automatic transmission. I've rarely owned an automatic (only luxury types) so I'm not positive on that.

Refer to your owners manual (page 22 in yours)...it states that an octane level of 98-100 is recommended. My understanding is that the 98-100 octane european equates to 92-94 octane here in the States. High octane fuels are less likely to pre-ignite. I feel for you guys over there with fuel costs, but you're going to have to bite the bullet on this one.

http://400register.com/manuals/assets/400-owners.pdf

 

Russell, thanks.
I haven't tested myself but the previous owner of my (manual) car had done and noticed some performance drop off with lower octane. I always put in Shell V-Power as it is 99 octane although this more through habit than anything else.

The previous owner had also experimented with additives for lead and also Millers to boost octane levels. I tried these as well but found them unnecessary if using Shell V-Power - there are also other recent threads on here which show Ferrari advice is that lead additives are not needed.

So - I guess bite the bullet and go for premium fuel. After all, the cost difference compared with other 400 costs is not that great. And - as my father says - this car never passes a Shell station...

 

The basic chemistry of gasoline is the same no matter what additive package it comes with. What we call gasoline is actually a mixture of eight different hydrocarbons, beginning with the smallest hydrocarbon molecule that is liquid at room temperature -- pentane (C5 H12) -- and ending with dodecane (C12 H26). It is these hydrocarbon molecules that the engine burns, producing CO2, H2O, and heat energy. Here's a universal formula I got from Wikipedia, which describes the combustion of any hydrocarbon: CnH2n+2 + (3n+1)/2 O2 → (n+1) H2O + n CO2 + Energy. The heat energy from the combustion of the hydrocarbons expands the nitrogen that is also included in the air:fuel mixture. (Air consists of about 80% nitrogen, 19% oxygen, and 1% "other.") This expansion exerts pressure on the piston. That pressure makes the car go.

It is anti-knock additives which give the different grades their octane ratings. The purpose of these additives is to prevent pre-ignition, aka detonation, ping, and/or knock. Pre-ignition destroy engines. A higher octane fuel does not produce more heat energy. But it allows you to run a higher compression ratio and/or to supercharge, without pre-ignition. And that additional cylinder pressure produces more horsepower. It is only in this sense that higher octane fuel results in higher output. It's not the higher octane that's making the higher power. It's the higher cylinder pressure, made possible by the higher octane, that makes the higher power.

Also higher octane allows higher base timing, without pre-ignition. All else being equal, higher initial spark advance creates a crisper tip-in and a more lively feeling engine.

On the subject of horsepower, you often see it written that an engine is an air pump, and therefore the more air it pumps the more power it produces. That is true. But it is even more fundamentally true that an internal combustion engine is a device designed to create pressure on a piston crown. The higher the pressure, the greater the torque. Torque is the force that causes the crankshaft to rotate, and to overcome whatever load is being applied to the crankshaft, trying to prevent it from rotating.

The way I think of it, horsepower consists of an engine's ability to make torque at high rpm. The formula for converting torque to horsepower shows this: hp = torque x (rpm/5252). Horsepower and torque are always equal at 5,252 rpm. But if the engine spins higher than that, the horsepower number exceeds the torque number. Build an engine that makes a paltry 200 lb-ft of torque at 15,000 rpm and and you've got a 600 horsepower engine. Horsepower gives you top speed, and it lets you keep accelerating in the same gear longer, before you have to shift.

But back to the subject of what fuel to run in a 400i: premium only! It has to do with quench area. Quench consists of flat areas in the combustion chamber that are cast into the cylinder head. An old school name for this is a "closed chamber" head. One characteristic of pre-ignition is that, for any given compression ratio, the more quench area in the combustion chamber, the less likely the engine is to detonate. Look at any modern cylinder head and you'll see quench areas. But look at the old school Ferrari combustion chamber: it's a hemi, with no quench at all. The old school name is "open chamber." At any compression ratio above 8:1 an open chamber head is going to be a ping monster. Also be aware that ping can be happening that you can't even hear. That ping will cavitate the piston crown, a little or a lot. It's best to minimize the possibility of ping. Therefore I would never run a Ferrari on anything but premium.

 

That's what I always use, but only in my newer cars.
I wouldn't dare use it on the 400 cause of the ethatnol.

I remember Harold posting his HP & torque curves & remembered that they didn't equal out @ 5,250...I mean it's close but no cigar.

http://ferrarichat.com/forum/showthread.php?t=365247&highlight=torque+curve

BTW, great chem lesson!

 

This "5252 rule" is only true if power is in horsepower units and torque is in ft-lbs (and the two curves "cross" at 5252 RPM on the chart only if the two vertical scales are the same). Harald's data is in given in kW and Nm (which are numerically equal at 9549 RPM), and the two vertical scales he used are not the same for both so the curves don't "cross" at 9549 RPM on the chart.

 

I think that his answer puts him in a league with other automotive experts, such as Ms. Mona Lisa Vito:

[ame]http://www.youtube.com/watch?v=QVX68dO7SPs[/ame]

 

Ownership of any Ford product with a Cleveland engine sporting the open chamber "2-barrel" heads will make you an expert on ping. My description of horsepower as high-speed torque is a simplification that I think is a good model of the relationship between hp and torque. Hydrocarbons are a fascinating family of chemicals. They range from the natural gasses methane, ethane, propane, and butane, to the liquids gasoline, kerosene, diesel, motor oil, and gear lube, to the semi-solid asphalt and the solid paraffin. All these molecules consist of carbon atoms linked in a chain, with two hydrogen atoms attached to each carbon, and an extra hydrogen attached to the carbon at each end of the chain. In a real sense it is the energy-making capacity of this chemistry which drives modern civilization, including much of defense spending and diplomacy. And the greenhouse effect.

On that last subject, realize that in perfect combustion each atom of carbon in your fuel tank will mate with two atoms of oxygen. Based on atomic weights, 12 pounds of carbon will become 44 pounds of the greenhouse gas CO2. A gallon of gasoline weighs 6 pounds. Based on this ratio of 44:12, and ignoring the weight of the hydrogen atoms in the gasoline, each gallon of gasoline we burn creates 22 pounds of CO2. A 30 gallon tank converts to 660 pounds of CO2. I just throw this out there as another fun fact to know and tell. Not trying to get political. It's just that it's surprising when you realize how much CO2, by weight, an IC engine creates.

 

I am a chemical engineer as well as car nut and I do work in refineries. It is not a correct statement that the only difference between octane grades is the additive package. The ratio of components is different to obtain the octane number. I have work colleagues that are better at this than I am. I believe the octane rating is done prior to mixing the additive package (more on that in a minute). If anyone wants to get serious on this subject I will get one of my colleagues to site a reference and post it. I am not sure about now, but prior to ethanol days, premium gas had a lower heat content then regular gas (because of the fuel blend). So if your car could run on a lower octane without knocking it would actually get better gas mileage! This may not be true today.

Additive packages are quite interesting. The US government mandates a minimum additive package for gasoline. This is in order to keep fuel injectors clean so the cars meet emission standards. Each of the "name" brands have their own proprietary additive package.

Before it was closed, sold and re-opened I had several guided tours of the Valero refinery in Delaware City. At the fuel truck loading racks there are a series of tanks. The largest one has no branding label and has the government mandated additive that goes to all of the unbranded stations. Then there is a tank for each of the branded fuels. Valero sold their gasoline to every branded station: Gulf, Exxon, Shell, etc. The only thing different at the loading rack is the additive.....the octane is set in the upstream tanks. In the old days lead was the main adjustment of octane, now it is not. Some will remember Amoco selling "lead free" premium in the '70's; they lied a little as it did contain small amounts of lead. They obtained high octane without much lead by adjusting the gasoline blend.

I personally think Shell additive package is the current best but since their additives are made by Infinium which is a JV of Shell and Exxon they both probably have very similar additive packages.

Bill, I am not knocking your input to this forum. I just had to add my professional knowledge.
Ken

 

Our Shell stations contain ethanol, so we have to hunt down an ethanol-free gas station...& they're not just around the corner, sometimes they're quite a distance away (depending where you live).
Oh, and another thing...our F-cars have aluminum fuel tanks, aluminum & ethanol don't mix, not to mention rubber seals & other things.

And you are soooo lucky, at least for now (until your gov't. decides that going green is more responsible, I'm thinking' it's only a matter of time ).

That's what I thought.

& I've heard that Chevron runs a close 2nd.

 

I love corrections! But please let me know if I'm understanding correctly. What I'm getting is that the refinery manipulates the octane difference between regular and premium -- and hence their anti-knock qualities -- by changing the mixture of hydrocarbons from one grade to the other. That is, regular would have more of the pentane, hexane, heptane and octane molecules, and premium would have more of the nonane, decane, undecane and dodecane.

My thinking that it's the additive package alone which controls anti-knock derives from the old days when they used tetra-ethyl lead, and the modern use of ethanol, to bump the octane ratings.

This heat content concept is over my head, but does this statement mean that, assuming we're using the same low compression engine for both, the regular gas will generate more cylinder pressure than the premium? I do recall putting some ethyl in my lawnmower's tank back in the '60's (running a super primitive flathead engine of course) and that it seemed not to run as strong as with regular.

 

Based on atomic weights, 12 pounds of carbon will become 44 pounds of the greenhouse gas CO2. A gallon of gasoline weighs 6 pounds. Based on this ratio of 44:12, and ignoring the weight of the hydrogen atoms in the gasoline, each gallon of gasoline we burn creates 22 pounds of CO2. A 30 gallon tank converts to 660 pounds of CO2.

This seems illogical. I could readily understand it if the change were in volume since the fuel goes from a liquid to a gasious state. Can anyone enlighten me?

Greg

 

Try this site: puregas.org. I hope that this is of some use. Jq.

 

Start with that formula I got from Wikipedia, which describes the combustion of any hydrocarbon:
CnH2n+2 + (3n+1)/2 O2 → (n+1) H2O + n CO2

Plug in the smallest hydrocarbon, methane (CH4; "n" = "1"):
CH4 + (3*1 + 1)/2 O2 → (1 + 1) H2O + 1*CO2
= CH4 + 2 O2 → 2 H2O + CO2

Now, drop the "H's" and, in place of the C's and the O's, substitute the atomic weights of carbon (12) and oxygen (16):
= 12 + 2*16*2 → 2*16 + (12 + 16*2)
= 12 + 72 → 32 + (12 + 32)

If you're still with me, what we see in the last line is 12 units of carbon have been converted to 12 + 32 units of CO2, or 44 units of CO2.

 

Please pardon me for the thickness of my skull. I haven't thought about such formulae since 1961 when I got a C- in High School Chemistry.

I can see where the weight comes in. It is by way of oxygen being heavier than carbon and there being two such units per molecule. What does the * mean in your example?

I presume the Ozone depletion we hear so much about is being caused by all this bonding with carbon via comubstion residuals, that is, free carbon and carbon monoxide floating about.

Is this about the gist of it?

Greg

 

Gasoline is not just made up of linear compounds from pentane up to C10 or C12. If you go much higher than that you are into diesel. There are cyclic compounds as well. There use to be a lot of benzene in gasoline to boost octane but that content is very low now due to the C word. But toluene and other cyclics are still in gasoline. Remember straight ethanol is about 100 octane. I just went and found a Wiki that explains all!
http://en.wikipedia.org/wiki/Octane_rating
The table will tell you the octane of many individual components and it has several versions of Shell V-Power.

The government back 10+ years ago was trying to control vapor pressure of gasoline so that it did not evaporate in your tank or while pumping at the station. They MANDATED MTBE which had good octane and was less volatile than other high octane options. Oops, it is water soluble and got into the water supply! So they ditched the vapor pressure thing and made sure gas tanks did not vent and bought into the farm block and went for ethanol as the MTBE replacement. Yes, ethanol is water soluble too but we all love it!

I think the Wiki will tell you more than I can dig up myself.
Ken