mike77

One of the other things I mentioned was biofuel. I've just been reading more on that. Super fuels are E5 which is 5% or less ethanol. Regular fuel is E10, 10% ethanol. I think we have until 2017 before the super needs to go E10. I believe this is documented to cause lower performance. It also seems to be a cause for concern for owners of older cars as it may cause damage to the fuel system and engine.

mark kibort

that was going to be my next question. how do i get fuel that doesnt have ethonol. there was a few stations in California. (there is a website that shows them) , but heck that is a power eater, right. what about the premium at the race track pumps.(sonocol fuel) are they subjected to the same % of ethinol?

what is the expected power loss for 5% vs 10% ethanol mixture?

mike77

Are you arguing that we should be running racing fuel in our cars?

I don't know what the power loss is but some reports suggest that some cars get 10% or more, less mpg and also higher co2 emissions than fuel with no ethanol.

mark kibort

NO, street cars and driving on the street, i go for cheap that cant hurt the car. regular in my other vehicles, but premium in the 928. however, if i was mellow in the 928 as a daly driver and it wasnt the stroker, i might use the middle grade.

My question was about ethanol in the race car for power concerns only

mike77

"My question was about ethanol in the race car for power concerns only"

Wouldn't race cars be built/tuned for using ethanol? As opposed to my S4 that was never intended to use ethanol.

mike77

Straight from Porsche themselves.

http://www.porsche.com/uk/aboutporsche/pressreleases/pcgb/?lang=none&pool=uk&id=2011-05-23-classic

"These Porsche vehicles may not be run on E10 fuel. As an alternative, Super unleaded (98 RON) can be used. With a maximum bioethanol content of 5% (E5 fuel), Super unleaded is compatible with these vehicles."

mark kibort

so, is that fuel bad for the car and for racing?

mike77

I don't know. The page says "Please contact your nearest Porsche Centre for more detailed information". So perhaps ask them.

As for me I'll be sure to run super with E5 until it is no longer available then perhaps run an additive such as Millers if there is no other option.

FredR

Mike,

What you say generally holds but not entirely. The main exception being the gasoline blended by Conoco at their Immingham refinery. They make their profits by selling petroleum coke from their delayed coker units so they market their gasoline cheaper to ensure the refinery runs flat out and so they discount the fuel to ensure it sells. I also have a feeling this is the stuff hypermarkets sell. Octane and other regulations wise it is perfectly OK but additives wise I doubt there is little or nothing extra to offset their losses.

The problem with high altitude locations is that gasoline that is stable at sea level would lose some of its light end components because of the reduced boiling point. It is quite conceivable therefore that the stuff they blend for use up there has heavier components with more calorific value that generates a little bit more power per kg burnt. The oil companies do not want to give you this -they just have no choice.

High octane fuel does not generate more power per se for the reasons mentioned above but it does permit a given engine to generate more power with higher compression and/or more advance. Indeed alcohol has very good octane rating but specific power output is quite a bit below gasoline I seem to remember.

Regarding our knock control on the later models this was quite an advanced system for its time and it is still quite potent. Under normal circumstances you will never be aware that it is doing anything as when it detects something , the correction is applied by the next firing stroke and only on the cylinder it detected the knock event. If you can hear knock taking place then there will be something chronically wrong like carbon build up on the pistons and/or valves and the full scope of correction [9 degrees retard] just cannot stop the problem.

The system can tolerate some degree of knock in terms of count per 10,000 firing events- cannot remember the number. The problem with this system is that it is so damm sensitive I reckon many of the things it registers as a knock are nothing but noise and thus the system could perhaps do with a better noise filter algorithm. In my sharktuner tests I found that many of these events were just not repeating and I think it was this that caused John and Jim to come up with the rule of up to 1 cylinder 3 degrees retarded or 3 cylinders 1 degree retarded is probably OK to live with. Try to get rid of knock events altogether and you ill pull a whole bunch of timing. You really need a dyno to do this and then I suspect you can really tell what is going on as true detonation will see power drop noticeably.

Given I am all to wary of the potential damage that can be done I am probably too conservative on my tunes. The problems are compounded by batch firing as air flow into the cylinders differs quite noticeably at different rpms. 6 and 2 seem to flow more air relatively speaking and thus are the first to knock on my motor followed by the other two inboard cylinders.

Rgds

Fred

Don Carter

With Shell gas, my understanding is that V-Power has more additives than Shell Regular or mid grade, and Shell Regular has more additives than the minimum required by law.

I became a believer about 10 years ago when I visited the Shell research center here in Houston, a massive complex that looks like a large college campus, and saw some of our test vehicles where the dirty valves in the pictures that used to be on the pumps came from. They had V6 engines with two fuel systems, one for one bank of cylinders and another for the other bank. Shell fuel was run in one side and non-branded fuel in the other (grocery store type gas with the minimum required additives). It was either 5k or 10k miles they ran the cars then broke down the engines and removed the valves. Huge build up on the non-branded gas valves. This was before V-power, but showed the differences in the amount and type of additives. Additives are not all the same either, so there are multiple factors that can make major brand gas better than unbranded.

There are several problems with the video, but I won't go into all that now. It does raise some interesting points, and like the Shell attendant said, many cars don't need premium, but if you believe more additives would keep your engine cleaner, which I think is reasonable, then you might want to burn a tank of V-power at least every once in a while even if your car doesn't need the octane.

Several posts in this thread mention that supermarket gas can come from the same refinery as name brand gas. This is true, BUT, the additives package is NOT the same. I've been to the terminal here in Houston where trucks are loaded with gas from the Port Author Refinery via a pipeline. There are large tanks at the loading area that inject the additive package into the trucks. Only trucks headed to the branded stations get the specific name brand additive package. Non branded gas gets a different additive package. The controls are very tight around this product differentiation.

996SPECticle

I don't get where the narrator sez "the oil companies are pushing premium gas." I have never once heard anyone other than a tard say premium is cleaner, better for gas mileage or makes more power. The only evidence they had were the tard pump jocks, maybe they're on commission.

And yes, as said most gasoline is the same except for the additives for Shell or Chevron Techron etc. that are splash blended in the filled tankers. There are minimum levels of detergents/anti-deposit crap in all Top Tier gas. http://www.toptiergas.com/retailers/
I think the worst thing you can do is buy premium gas from a station that sells very little of it. Any grade from a low turnover place really. Don't worry about water, they all have some water in their tanks

Does anyone have any stations near them that have 4 grades of fuel? Shhhh, there are only two tanks in the ground

You wanna reason to get mad at gas companies? Live a few miles from about 6 refineries and pay the same price as someone 500 miles away. Why? Because they can.

The Forgotten On

I live near a place that has 4 grades. 87,89,91 and 110. Albeit the later sells for $6 per gallon and is the only station in the area that sells it. That must mean they have 3 tanks, right

jpitman2

My experience in Oz (91,95,98 RON gas) in cars that have knock sensors (late Subaru turbo 4 and H6) is that we 'feel' they run better on 98 and the highway mileage is measurably better, especially the H6, which is a well known guzzler. 91 is regarded as comparatively dirty, less well filtered.
I usually run 95 in the 928, a couple of degrees advanced over stock - dumb ignition system. I have used 91, and NEVER EVER heard it ping.
jp 83 Euro S AT 56k

SwedeInSiam

I run my '80 Euro S on 95 RON which is the best fuel available here. Ignition set to factory spec. Never heard a ping and haven't seen any evidence of pinging in the cylinders.

Don Carter

That's good info about Top Tier gas. I was going to post that too, but my reply was getting a bit long.

Mid grade is usually blended on site.

As for water in the tanks, it's true that there is often some amount of water at the bottom, but if it ever gets close to the pump intake level, automated alarms contact the maintenance contractor so the issue can be immediately addressed. I'm not sure if the unbranded sites have this level of sophistication or not. Similar sensors/alarms exist for tank and pipe leak detection.

Another interesting fact is that for many of the majors, they no longer own the gas stations, at least in the US. Other smaller companies own and operate the stations, and could own stations including other brands.