low compression 548 dyno testing has begun!!
#272
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Joined: Jul 2004
Posts: 11,332
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From: chicago
Would it be safe to assume, that if we are talking big blocks per say, that BSFC numbers, can go up with things like, longer stroke cranks, thick piston rings, windage control, aside from the obvious, like combustion efficiency, ignition timing, etc?
I would think that a 700HP 4 inch stroke, running modern ring package good windage,, would have lower BSFC numbers, than a 700HP 4.5" stroke deal running an old school ring package, windage, etc. Seems like some of the guys building NA engines, with low tension rings, vacuum pumps, short stroke, good heads, cam, compression, are getting some really low brake specifics.
I would think that a 700HP 4 inch stroke, running modern ring package good windage,, would have lower BSFC numbers, than a 700HP 4.5" stroke deal running an old school ring package, windage, etc. Seems like some of the guys building NA engines, with low tension rings, vacuum pumps, short stroke, good heads, cam, compression, are getting some really low brake specifics.
#273
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Joined: Jun 2004
Posts: 7,317
Likes: 1,037
From: frankenmuth michigan
So lets say the HP was 753 corrected on sheet, and 685hp observed. The correction factor listed 1.0736 on sheet.
685 x 1.0736 = 735hp
685 x 1.0836 = 742hp
685 x 1.0936 = 749hp
685 x 1.1035 = 755hp
Seems like while the correction factor was 1.0736, it actually added about 9% to the observed number with Depac. Air Temp listed at 84.6 F, 29.211 baro, SG .751,
685 x 1.0736 = 735hp
685 x 1.0836 = 742hp
685 x 1.0936 = 749hp
685 x 1.1035 = 755hp
Seems like while the correction factor was 1.0736, it actually added about 9% to the observed number with Depac. Air Temp listed at 84.6 F, 29.211 baro, SG .751,
#274
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Joined: Jun 2004
Posts: 7,317
Likes: 1,037
From: frankenmuth michigan
Would it be safe to assume, that if we are talking big blocks per say, that BSFC numbers, can go up with things like, longer stroke cranks, thick piston rings, windage control, aside from the obvious, like combustion efficiency, ignition timing, etc?
I would think that a 700HP 4 inch stroke, running modern ring package good windage,, would have lower BSFC numbers, than a 700HP 4.5" stroke deal running an old school ring package, windage, etc. Seems like some of the guys building NA engines, with low tension rings, vacuum pumps, short stroke, good heads, cam, compression, are getting some really low brake specifics.
I would think that a 700HP 4 inch stroke, running modern ring package good windage,, would have lower BSFC numbers, than a 700HP 4.5" stroke deal running an old school ring package, windage, etc. Seems like some of the guys building NA engines, with low tension rings, vacuum pumps, short stroke, good heads, cam, compression, are getting some really low brake specifics.
As far as the negative correction factor dyno session and sub
.4 bsfcs i was talking about, it was on a 2 stroke snowmobile on a dyno where the dyno cell was cooled to sub 32 degrees, 2 strokes make best hp on edge of burndown
#275
#276
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Joined: Jan 2006
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From: taxachusetts
Would it be safe to assume, that if we are talking big blocks per say, that BSFC numbers, can go up with things like, longer stroke cranks, thick piston rings, windage control, aside from the obvious, like combustion efficiency, ignition timing, etc?
I would think that a 700HP 4 inch stroke, running modern ring package good windage,, would have lower BSFC numbers, than a 700HP 4.5" stroke deal running an old school ring package, windage, etc. Seems like some of the guys building NA engines, with low tension rings, vacuum pumps, short stroke, good heads, cam, compression, are getting some really low brake specifics.
I would think that a 700HP 4 inch stroke, running modern ring package good windage,, would have lower BSFC numbers, than a 700HP 4.5" stroke deal running an old school ring package, windage, etc. Seems like some of the guys building NA engines, with low tension rings, vacuum pumps, short stroke, good heads, cam, compression, are getting some really low brake specifics.
#277
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Joined: Jul 2004
Posts: 11,332
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From: chicago
Asking because i see engine builders on speedtalk and yellow bullet getting bsfc's of low 4s or even lower on NA bbc builds. I was always under the impression bsfc's were more an indicator of how efficient the engine build is, rather than the fuel mixture.
#278
When I dynoed my 454 I was around .52 bsfc and that was where it liked it. The next day we dyno'd Jim's 565 and played around with the fuel injection all day and it was about .43 where it ended up at. If that means anything.
#280
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Joined: Jun 2004
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From: frankenmuth michigan




