oil?

[Jean-Sebastien Stoezel]

I'm being told by my engine builder that I should not be using regular gas anymore (like I did last summer). I'm not concerned about the higher octane that AvGas comes with.
Most people at the track run pump gas (from what they report). At the same time they only rebuild their engine when it's about to blow or it's blown. All that to say I'm not sure how much they care about maintaining a healthy engine.

The engine builder has observed some wear since the last rebuilt (last season). Also I was overheating like crazy and apparently leaded gas can help reduce overheating issues. I've improved the cooling of the heads, but at the same time I want to make sure I will not overheat again.
The drag shop guy mentioned that leaded gas helps with cooling too, it's something to do with the way leaded gas or racing gas burn. It's something he's seen on the dyno from what he reported.

Either way both that guy and my engine builder are very convinced I should not be using street gas, but leaded gas.

Jean - most of us in BC run 94 octane chevron.. It seems to work fine for most people. Some engine builders aren't fans of this - it can cause dieseling (setting your idle as low as it'll go can help, as can stalling the car in 4th gear instead of just switching it off).

Others say you need the lead to lubricate the valve seats and guides. The compression is low enough that we really don't need 115 octane gas, Avgas should be good enough. I've also been told to use a 5:1 ratio of pump to race gas - which again makes me think that Avgas would have enough lead to do what we need it to do.

I'll let the experts answer the question in more detail, but yeah, just wanted to let you know that a lot of people happily run good ol' pump gas with no apparent trouble.. knock on wood.

[Tiago Santos]

Well, then just do whatever your engine builder says, that's what I would do. Not that I think there's any sort of warranty with the kind of engine work we get, but if I trust someone to build me an engine (and considering these things ain't cheap, it is all about trust!) I'll do whatever they tell me to do.

Well, within reason

btw - 94 octane in Canada has no ethanol, all other grades are E10.. Supposedly!

[Jean-Sebastien Stoezel]

Alright then, I won't be using the VP gas then but AvGas.

Too bad because AvGas is much harder to get here.

Av Gas is ok. It has plenty of lead, (double what the low lead street fuels used to have) but you don't need it. The VW's heads have had the hard seats for years and VW said no lead was fine. As far as octane/race fuel. You have a compression ratio of under 8:1, so a 91 octane or above is fine. Some race fuels MAY help a bit HP wise due to flame front enhancers, etc, but you will do fine with AvGas or even better premium pump fuel if you are allowed to use it. Ask your builder what SG (specific gravity) he used when he dyno tuned it. If you have E10 up there in the street pumps AND he dynoed to that SG, you won't be able to do any better with a "Race" gas and you will save lots of money. (If you have the choice to use street premium, use it instead of AvGas. AvGas is ok, but it is not really formulated for the close to sea level racing and our application.)

BTW, using the fuel that your builder dynoed and tuned it with is far more important than what fuel you end up with.

(Before anyone jumps in about fuel cells and E10; ATL and Fuel Safe have both said E10 is ok. Just follow proper suggestions on keeping the cell topped off between weekends, or totally empty. One or the other.

[sracing]

I'm being told by my engine builder that I should not be using regular gas anymore (like I did last summer). ..

The engine builder has observed some wear since the last rebuilt (last season).

Did he say where the wear was? The only place lead would help wear is on the valve seat. It cushions the valve seat. Its only other function was anti-knock prorpeties. You don't need it. Your seats are hardened and you valve spring pressures are relatively low. Your valve guides also don't want or need it.

Also I was overheating like crazy and apparently leaded gas can help reduce overheating issues.

Lead in itself has no effect on heating. I have no idea where he would get that idea. Other than cooling shrouds, etc. heating is caused by improper by a/f ratios and/or timing.

The drag shop guy mentioned that leaded gas helps with cooling too, it's something to do with the way leaded gas or racing gas burn.

He is also wrong.

Either way both that guy and my engine builder are very convinced I should not be using street gas, but leaded gas.

Well it won't hurt anything, but it won't help a thing either and will just cost you money.

From what you are describing here it sounds like these guys are confusing proper jetting with the fuels and additives.

While it doesn't matter too much on a FV engine. Higher octane fuels in themselves usually have less BTU (energy content per lb). A high octane fuel is NOT goodness. It is ONLY a necessary evil in high compression or boosted engine. In building performance engines you tune for the LOWEST octane fuel you can to get through peak torque range and best BSFC without knock. If an engine is tuned properly and matched for a fuel, increasing octane does nothing for performance or economy.

The fuel being used should have the SG measured and then tuned for it. For example a street pump premium is in the .75 SG area. Some of the race fuels are in the .71 area. If you tune for a race fuel, you have to use it (and lose HP on an engine that doesn't need it.) If you tune for the proper octane fuel you will maximize HP.

That is why I said, runnning the engine on what it was tuned for is more important than any particular fuel.

Not trying to be rude here... but if your engine builder told you what you have said, he is simply wrong or you may have misunderstood him.

[budawe]

I have always used av gas cause it's cheap, easy to buy for me, and it's very pure and stores well. The FAA has a lot to say about the manufacture of Av gas. Most street fuels do not carry the committment to purity and consistency that av gas has. You may even get different gas every time you fill up. Most race fuels go stale and will cost hp over time. Recently, several Vee engine builders have begun to recommend and tune for race unleaded fuel that has been oxygenated. Sunoco unleaded seems to be the preferred since it's available at most tracks and is the required fuel at the Runoffs. Timing and jetting have to be altered for it's use.

[Hardingfv32]

1) E10 street gas (10 alcohol) will defiantly aid with engine cooling IF jetted correctly. Say one or two main jet sizes bigger. Note: it is generally accepted that you cannot "read the plugs" when using unleaded gas.

2) Our carbs are not going to notice any small irregularities that might be imagined with street gas.

3) I'm not sure Sunoco 93 Unleaded found at the track is not just street gas. Sunoco does not list it as a racing unleaded gas.

Brian

[sracing]

1) E10 street gas (10 alcohol) will defiantly aid with engine cooling IF jetted correctly.

And give you more HP.

Say one or two main jet sizes bigger. Note: it is generally accepted that you cannot "read the plugs" when using unleaded gas.

You can't read the plugs on an ACVW with a 28PCI with ANY fuel.

2) Our carbs are not going to notice any small irregularities that might be imagined with street gas.

Yep. Pretty much ANY street gas will have the same SG.

3) I'm not sure Sunoco 93 Unleaded found at the track is not just street gas. Sunoco does not list it as a racing unleaded gas.

It's just 93 Octane street gas with Ethanol.

[Hardingfv32]

I would have mention more power, but then I would have to defend/state how much to the skeptics.

Brian

[sracing]

25 to 30 additional hp with a Monster Mani.