[hurryinhoosier62]

.49-.50 BSFC? Dear God, that IS efficient!!!

[72LuxuryLeMansLa.]

Originally Posted by hurryinhoosier62

.49-.50 BSFC? Dear God, that IS efficient!!!

Tom seems to tend towards the generic no frills kind of builds....I mean, who doesn't run a RAV...… Boring.

[Dick Boneske]

Those numbers were with a 303 c.i. engine?

[pastry_chef]

Originally Posted by Dick Boneske

Those numbers were with a 303 c.i. engine?

434 CI, 9.5 CR

[ponjohn]

Very cool.

Interesting split on the cam.

[tom s]

It is a factory 303 std deck block.3in main.Its really just a 70 RA block with engineering numbers.4.120 bore.Tom

[tom s]

because there were 29 pulls I just will post the best HP pull and best TQ pull.He had to figure the corrected and wrote them in in pen.Tom

[hurryinhoosier62]

Originally Posted by tom s

It is a factory 303 std deck block.3in main.Its really just a 70 RA block with engineering numbers.4.120 bore.Tom

Tom, what stroke is the crank?

[hurryinhoosier62]

Originally Posted by 72LuxuryLeMansLa.

Tom seems to tend towards the generic no frills kind of builds....I mean, who doesn't run a RAV...… Boring.

Karl, an average street engine has a BSFC of .38-.40. Most race engine have a BFSC of .45-.48. This engine is incredibly combustion efficient for an NA engine.

[tom s]

4in stroke,4.150 bore.This engine liked a lot of timing which is usual for RA V chambers.Most HP were at 36-38 total.34-35 cost us 9 HP on the upper end.I know I could have got another 40HP with a 1in spacer and my 950 carb but except for headers I wanted it as it has to be in the car.With the 69 RA setup there is no room for any size spacer and the lower RA pan wont clear the 950.Tom

[pastry_chef]

Originally Posted by hurryinhoosier62

Karl, an average street engine has a BSFC of .38-.40. Most race engine have a BFSC of .45-.48. This engine is incredibly combustion efficient for an NA engine.

Lower BSFC is more efficient. .400 is better than .500, it means more power from the same fuel.

[hurryinhoosier62]

Originally Posted by pastry_chef

Lower BSFC is more efficient. .400 is better than .500, it means more power from the same fuel.

Ever read any of Jim McFarland's writings on BSFC? Probably not. For years, the accepted "standard" for race engines using race gasoline was .500 BSFC. McFarland found that optimum BSFC coincides with peak torque. One of the most important quotients in a BSFC calculation is the type(and quality) of the fuel utilized. Here's an example: Darcy built a new engine for his Firebird a couple of years ago. This was a purpose built race engine fueled with race gasoline.Darcy saw BSFCs in the .44-.46 range.....a truly efficient race engine with a peak torque in the 4800-5000 rpm range. Tom's engine is a street performance engine. It is powered with the 91 octane "panther piss" California alleges is gasoline. Are you willing to agree that racing gasoline is a more powerful fuel (isometrically speaking) than the 91 octane CA 'panther piss"? Tom's engine is already saddled with fuel that more than likely does NOT meet its BTU requirements(meaning it WILL require additional fuel) nor is it a purpose built race engine. As Tom has stated, it won't see the high side of 4,000 rpm. Factor these variables into the BSFC equation, you'll discover that Tom's engine is nearly as efficient as Darcy's. IMO you are confusing fuel efficiency with combustion efficiency. I'm talking about combustion efficiency.

[tom s]

These sheets are hard to compare as the EXACT RPMs are what the TQ and HP is at on the pull and the engine is held at that RPMs for MANY seconds.A fellow board member is putting all of these pulls in a spread sheet and graph to look at them better.All the first 11 pulls were done with 20-50 breakin oil and 37 degrees with a heavy spring in the vac sec holley.The next 10 were done at 37 degrees and 10-30 mobil 1 and a lighter vac sec spring.The final 7 were at 34 degrees,and the same 10-30 oil and sec spring.ALL the final RPMs were held for many seconds.
Here are some examples of each group @about 5000RPMs
5121 RPMs,482.5 TQ 470.5 HP 202 lbs/hr fuel flo .451 bfsc
4981 487.7 462.6 215 .489
5049 486.9 468.1 214 .481

Not sure if anyone finds this usefull?

[Steve C.]

Jim McFarland explains brake-specific fuel consumption (BSFC) and how it impacts the thermal efficiency of a racing engine ...

https://www.google.com/url?sa=t&sour...nuiP-sct92drWJ


.

[pastry_chef]

Originally Posted by Steve C.

Jim McFarland explains brake-specific fuel consumption (BSFC) and how it impacts the thermal efficiency of a racing engine ...

Thanks Steve, everything is right here.

As engine builders and modifiers refined ways to improve both thermal and combustion efficiency by methods that included combustion chamber shapes, piston crown designs, exhaust system efficiency, and related areas, the original “standard” for gasoline decreased to somewhere only slightly north of 0.400. This meant that improved combustion was allowing the same amount of fuel to produce an increase in power—e.g., combustion efficiency improved. As a result, BSFC was reduced.

[Steve C.]

Love Google

The volumetric efficiency numbers on my previous 462 even with a crappy low 9.7 static compression using alum heads was fine with a high of 110.8 and the BSFC number at peak torque was 0.42
It's my understanding a well-tuned high-performance RACE engine should come in at 0.45 or lower.


.

.

[tom s]

Guys,as said the dyno operator said my dyno headers were hurting the engine.They are 2 1/8 4 tube off a tube frame race car.1 7/8 will be made on the car which should help the TQ numbers.Tom

[pastry_chef]

Originally Posted by Steve C.

It's my understanding a well-tuned high-performance engine should come in at 0.45 or lower.

Close with this Ehead street 461 Pontiac, RPM intake, 236/242 dur @ .050" .543"/540" 110 LSA cam, 1.5 rockers.

[Steve C.]

During a dyno session the first thing Steve Brule at Westech Performance looks at is the BSFC numbers !


.

[pastry_chef]

Originally Posted by tom s

Guys,as said the dyno operator said my dyno headers were hurting the engine.They are 2 1/8 4 tube off a tube frame race car.1 7/8 will be made on the car which should help the TQ numbers.Tom

That makes sense Tom, thanks