11 to 1 - too much on CA 91 pump gas? - Page 4

Excaliber · #61 (**permalink**) 10-30-2010, 04:10 PM

Quench, good point. Following Gessford Machine's advice, I had my new custom pistons spec'd to raise them in the bore to introduce some quench into the combustion chamber. One of the benefits, as I understand it, is the ability to run more advance and lower octane with less impact on detonation.

Bernica · #62 (**permalink**) 10-30-2010, 05:19 PM

Quote:

Originally Posted by RodKnock

So you're telling us that your CSX runs great with 11:1 compression and race gas. Cool.

I guess I could have written it better. My point was, prior to getting the 100 octane, I was trying to run 91. Dieseling, pings, pulling timing back etc. AFTER I put in the 100, yes, it was cool. Expensive, but cool. And a whole different "aroma" from the exhaust too.

By the time I got home from filling it, my credit card company was calling the house to let me know that someone was using my card to fill a bunch of cars!! I had to explain that it's just me...

Excaliber · #63 (**permalink**) 10-30-2010, 10:24 PM

Having to run race gas just didn't work for me, it's to limiting on how far you can drive for one thing. Not to mention the extreme cost! It's not like you can just pull off the freeway at any given place and find race gas. I need something that can go the distance and is reasonably easy to care for, maintain and buy fuel at a decent price for.

Having said that, I did give up some horse power when I rebuilt for a more streetable tuned motor. Most of the time, I don't miss the really BIG power because I can barely hook up what I got anyway! Tires are always the limiting factor. BUT, when I'm running the race slicks (front and rear) and tearing up Infineon raceway, I do find myself wanting a bit more power in the higher gears.

Dominik · #64 (**permalink**) 11-11-2010, 09:30 AM

Sorry, if I repeat someone, haven't read the whole thread:

A thicker gaskets may actually have the opposite effect in offsetting the desired quench area resulting in a worse flame travel (assuming it's not a hemi head).

A long duration cam helps at part throttle, but it's unlikely to rectify knocking at WOT.
There you could retard total ignition (at WOT).

To reduce (avoid!) detonation at part throttle play with the timing curve (weights). I strongly suggest to get someone on a chassis dyno to assist with the timing curve.
You can hole your pistons in seconds.

Also, if your car is light and has a short (numerical high) rear end, it will accelerate through part throttle faster reducing duration of knocking.

Keep an eye on A/F ration (air/fuel) too.

I ran 12.5 to 1 on german 98 RON octane which is about your 93 MON with a 2000lb car and 3.54 to 1 diff. It was weather sensitive...

If all the above fails, mill the piston domes off. Ask the piston manufacturer for min head thickness, or get a new set of pistons!

If your cam is matched to the 11:1, change cam timing a bit (advance?) Speak to your engine builder.

Excaliber · #65 (**permalink**) 11-11-2010, 10:00 AM

Dominik, interesting point about using thicker head gaskets and loosing any potential "quench". The original FE's didn't have any to speak of, nor was it a concern with high octane being readily available at that time. The piston is as much a .030 below deck on a typical FE. I had custom pistons made to specifically address this concern by raising the piston height to just under the deck. I forget the exact amount, but it was very close to the deck height.

The OP may or may not have quench to speak of anyway, in such a case, nothing lost by running thicker head gaskets. But it sure is an interesting question!

Dominik · #66 (**permalink**) 11-11-2010, 10:49 PM

Hi Excaliber!
We made that experience a while back when the Chev LS7 was the toughest you can buy and tried the above resulting in "rattling like a bag of nuts". There are people here that can explain better the dynamics inside the head, but the proper quench initiates speedy flame travel.

The FE has a flat portion in the head, right?

Anyway, I guees you can make 11:1 work if you tweak all the minor options.
Is the car "above" build with ally heads? The Chevs benefit from bleed holes in the heads to reduce hot spots. So should the FE.

Fuel quality may also be different from gas station to station. It cold prove worth a while to shop around.

D

Excaliber · #67 (**permalink**) 11-11-2010, 11:32 PM

The FE's do have a flat spot in the combustion chamber, which works well for achieving quench. FE's also like a LOT of timing advance, quench allows for more of it with better control of pre-ignition which adds horse power. Or you could run "normal" timing with lower octane fuel. Either way, it's a win win. Anytime you increase the efficiency of a motor two things are going to happen: 1. Makes more power. 2. Get's better mpg.

BAsque1 · #68 (**permalink**) 02-09-2011, 06:53 AM

I have a 427 FE SO and cannot figure out if it uses leaded or unleaded fuel. Any way to find out if I have to add lead additive or not?
Please any comments will help
Tks
Basque I

Excaliber · #69 (**permalink**) 02-09-2011, 07:03 AM

No matter what your engine is or how it is built, or when it was built, there is no need to worry about using unleaded gas. In spite of all the dire warnings you might have heard over the years, it just aint no big deal one way or the other. No worries.

CobraEd · #70 (**permalink**) 02-09-2011, 09:52 AM

I haven't read the whole thread, so this may have been stated earlier, but anyway, don't almost all gas stations sell 93 octaine. Why are we discussing 91 octaine ??

.

garry viohl · #71 (**permalink**) 02-09-2011, 10:34 AM

Here in California its only 91

bobcowan · #72 (**permalink**) 02-09-2011, 11:18 AM

Same in CO, 91 is the best pump gas you can get.

rodneym · #73 (**permalink**) 02-09-2011, 11:38 AM

This may be old news to some of you guys but there are 76 stations in the southland (Fullerton, Pasadena, West LA - 2) where you can get Sunoco 100 octane at the pump. It ain't cheap, about $8/ gallon, but you can mix to get your octane up to 93, etc. Ask boat owners

Not to mention specialty shops where you can bring your own container. They have the good stuff.
I know a guy who says he gets aviation fuel from the Santa Monica airport at $30/gallon

But he has an old Camaro so he's probably a liar

RodKnock · #74 (**permalink**) 02-09-2011, 12:49 PM

Quote:

Originally Posted by rodneym

This may be old news to some of you guys but there are 76 stations in the southland (Fullerton, Pasadena, West LA - 2) where you can get Sunoco 100 octane at the pump. It ain't cheap, about $8/ gallon, but you can mix to get your octane up to 93, etc. Ask boat owners

Not to mention specialty shops where you can bring your own container. They have the good stuff.
I know a guy who says he gets aviation fuel from the Santa Monica airport at $30/gallon

But he has an old Camaro so he's probably a liar

There's a 76 station nearby me that sells the 100 octane unleaded gas from the pump at $6.29/gallon. Cheap.