HONDATA seminar DVD - Fuel Octane / compression question

LK7R · Post by **LK7R** » Fri Mar 21, 2008 9:20 am

Hi,

bought Hondata seminar on DVD and one thing really surprised me.

At the very end Doug mentioned:

"And here is something about fuel. Run lowest octane number fuel you can."

Then he explains that no high octane fuel is needed until high compression is used on the engine. So only in higher compression engines (13, 14.0:1 or so) will benefit from the high octane fuel and that 11,5:1 compression engine will run just fine with 91(US) / 95(EUR) fuel.

Now the question:

With higher octane fuel you can advance timing of ignition that will bring you more power and less knocking. Isn't it what we want?

So if i use 91(95EU) octane fuel on stock N/A 2004 Civic Type R EP3 (11.0:1 compression) then can I "max out" the 93(98EU) fuel on this engine or not?

I'm a bit confused now.

If i understand this right - there is a point where ignition can't be advanced any more no mater what fuel is used? And that "ignition advance wall" is mostly engine compression dependent?

For example:

On the 11.0:1 compression engine the 91(95EU) octane fuel is "maxed out " and if i put 93(98+EU) fuel in i won't be able to advance timing any more anyway?

I'd be gratefull if someone could explain this to me.

cheers

Dan

Post by **Spunkster** » Fri Mar 21, 2008 10:43 am

Higher Octane fuel slows the burn rate. You want the fuel to burn as quickly as possible without detonation. So you want to run the lowest octane possible without detonating.

LK7R · Post by **LK7R** » Fri Mar 21, 2008 8:22 pm

Spunkster wrote:Higher Octane fuel slows the burn rate. You want the fuel to burn as quickly as possible without detonation. So you want to run the lowest octane possible without detonating.

Thanks for the quick reply Spunkster.

Understood.

Now if i ask other way round.

What makes more power:

1) lower octane fuel maped to the best ignition advance without knocking

2) higher octane fuel maped to the even higher ignition advance without knocking

basicaly - from what can I get (in general) more power - ignition advance OR quicker burning mixture

From what you have written i gues it is quicker burning mixture RIGHT?

jordancivic · Post by **jordancivic** » Sun Mar 23, 2008 7:18 am

Where can i buy this DVD ??

LK7R · Post by **LK7R** » Sun Mar 23, 2008 1:22 pm

At your Hondata dealer or website (clubrsx.com for example)

Post by **Spunkster** » Mon Mar 24, 2008 12:14 pm

There are far too many factors to give you a simple answer. You must take compression ratio, temps....etc into account. This is why books are written.

LK7R · Post by **LK7R** » Tue Mar 25, 2008 12:41 am

No need to get angry - will do my homework then. I wasn't expecting the infinite answer, just general answer like:

based on our long time experience - stock RSX type S with basic mods(hondata, exhaust, headers, CAI) is in most cases 93(98) octane fuel waste of money ... something like that

cheers

Dan

Post by **Spunkster** » Tue Mar 25, 2008 9:32 am

No one is angry.