better mileage with higher octane?

[Bob]

I didn't insult you and cheese didn't make me think you were lying. Good
luck with everything else..... wow

 

[Steve]

Bruce Richmond wrote:

IMO circle track racers operate in a narrower rpm range than a
dragster. And on tracks like Daytona the pedal stays planted most of
the time, so response isn't a problem.

True at Daytona *today*, but I kinda doubt that they ran wide open
through the turns back in the big-block engine, skinny tire, no aero
downforce days of the 60s even at Daytona. I wish they still ran that
way, the racing at Daytona and Talledega today is more boring than
watching grass grow.

Another factor is that back when we were talking about they didn't have
the huge carbs they did later. The dual-quads made more power because
they provided the most veturi area.

That's certainly true. The dual quads on the old cross-ram 413s were
only good for about 400 to 500 CFM each at best.

 

[Eeyore]

True at Daytona *today*, but I kinda doubt that they ran wide open
through the turns back in the big-block engine, skinny tire, no aero
downforce days of the 60s even at Daytona. I wish they still ran that
way, the racing at Daytona and Talledega today is more boring than
watching grass grow.


That's certainly true. The dual quads on the old cross-ram 413s were
only good for about 400 to 500 CFM each at best.

What are these quads you talk of ?

Graham

 

[clare at snyder.on.ca]

Maybe you are looking at the US version of the 350 instead of the
Canuck block?. This one was the real Olds engine before the Chev 350
narrow block ones became commonplace. My memory could be failing me
but I just remember they backed the compression ratios down after that
one. The trend was to increase compression more and more in the 60s.

An Olds Rocket is an Olds Rocket - not a Chevy
The 350 OLDS engine came to the Cutlass in 1969. This was the 4.057"
bore rocket, not the 4.00 inch bore Chevy and was used AT LEAST until
1985.1986 to 90 did not have a 350 engine available.The Chevy 350 was
used in 1992 and up In Canada the 350 was not available (except the
Deisel) from 1981 to 1985 and in 1979 the"L" code 350 was a Chevy
while the "R" code was an Olds. This is from the information I have
available (which covers USA and Canada.) In Metric speak, the olds was
a 103mm bore, and the Chevy a 96.5
In 1979, the 103mm 350 was 7.9:1, and the 96.5 was 8.5:1

My '69 Cutlass 350 Olds engine ran a 13.8:1 compression ratio and
yup...it needed high octane.

Factory CR on '69 Olds 350 rocket is 9.0 Up to 10.0:1 on the high
output version. 13.8 is VERY high.
The 429 Cobra Jet Super Cobra Jet, or Boss 429 ran 11.3:1
That's the highest stock north american CR I've seen in the sixties.

The Olds Diesel was 22.1:1
Diesels can run from 15:1 up.

y_p_w wrote:

Solar Flare wrote:

High compression needed it [higher octane] to reduce dieseling.


Or forced induction. Pretty much anything that increases the
fuel/air pressure in the cylinders would require higher octane
fuel.

My 2004 WRX with a 2.0L turbo four engine has a compression
ratio of 8.0:1. It sounds low, but then you add the boost.

7:1 isn't uncommon when boost is anticipated. And the other cool
thing about boosted engines is that they have cam profiles with
very
minimal valve overlap so they generally idle as smooth as a
Packard
v12. Whereas a normally aspirated engine with similar performance
would have 10:1 compression and a wild cam that would lope at idle
like a '67 426 Hemi.

 

[Steve]

Steve wrote:


What are these quads you talk of ?

4-barrel carburetors. One under each of the red air-cleaners in this photo:

http://www.hotrod.com/2004powertour/113_day4_2004/photo_06.html

 

[Steve]

An Olds Rocket is an Olds Rocket - not a Chevy
The 350 OLDS engine came to the Cutlass in 1969. This was the 4.057"
bore rocket, not the 4.00 inch bore Chevy and was used AT LEAST until
1985.

The Olds Rocket lived on into the early 1990s. It was the "5.0L" (about
307 CID) and "5.7L" (350 CID) engine used in the Cadillac Broughm
(formerly "Fleetwood Broughm) up until the time that they started
putting the Chebby LT-1 350 in the Broughm, the "bathtub" Caprice, and
the Buick Roadmaster.

 

[51_racing]

It pretty much invariably
improves performance.

Graham

Absolutely could not be more WRONG here.
I race(d) in a class that limited compression to 9.5:1.
We could run any fuel we wanted, and time after time, people would put
race gas (Sunoco 110 or Turbo 110) then have to crank their ignition
timing way up only to come close to getting the same performance that
they did using 92 octane pump gas.

 

[Eeyore]

Four barrel carbs,

I wondered but hadn't heard the term before.

Graham

 

[Eeyore]

Absolutely could not be more WRONG here.
I race(d) in a class that limited compression to 9.5:1.
We could run any fuel we wanted, and time after time, people would put
race gas (Sunoco 110 or Turbo 110) then have to crank their ignition
timing way up only to come close to getting the same performance that
they did using 92 octane pump gas.

That's hardly typical though. I thought we were talking about road cars ? Also
modern cars don't have manual timing adjustment., the ECU does it.

Graham

 

[*]

Some how I just can't see a circle track racer saying. "We can get
along fine with less power."

I had one tell me exactly that at Oxford Plains Speedway a few years back.

He was running a NASCAR Busch North Series car and he said, "Man, I wish we
could put my little Pro-Stock engine in. This track is so hard to hook up
to."

The more circular and the flatter the track is, the less power and the more
chassis - "handling" - is needed.

Too much power breaks the rear wheels loose all the time, and the car
certainly does not "handle" well.



Even if some were to take that aproach in

 

[lp13-30]

This is a very interesting and informative thread-as is the group here
as a whole. Here in S Tx. 87 octane is $2.05 at a few independent
stores, the major chains are mostly in the $2.12-2.17 range. At at least
95%, the difference between grades is a dime, so it really wouldn't take
a very big increase in mileage to be cost effective. The problem is that
such a small increase would be hard to accurately determine, given all
the variables affecting gas mileage. I would imagine that even the
temperature would affect octane requirements. In desert areas where it
may be 70 in the morning and 100+ in the afternoon, it may not be cost
effective on the way to work, and the opposite on the way home. The
funny thing is that there was a dime difference between grades when gas
was $1.00, and also when it was $3.00, but as the price was climbing
towards $3..00 (about as high as it got here) people started buying 87
octane instead of 89 or 91, when it is actually a better deal as the
price increases. I have a company van and they use 87 octane, and the
only gas burner I have is a Ford Aspire, so do spend much on gas. Diesel
is another story tho-- got a couple and have some questions. since there
seem to be some pretty sharp gearheads in here, let me know if it is ok
to ask in this thread --or at all. Larry