Horse Power Predicton +/-10% (I think....)

[xctasy]

Okay, I've fielded this for all your benefit. It's sort of like the Virtual Reality Drag strip with a bit more gutts to it. http://fordsix.com/forum/viewtopic.php?t=6711

RemeMber this?

Take the cubic capacity of the motor in question, multiply it by the peak power rpm (10% ofF* the maximum safe rpm for the engine) and divide it by one of the following factors:
7000 if your six is box stock,
6000 if its got a good street intake manifold and exhast,
5500 it is worked with a cam that is over 260 degrees and very good breathing,
5000 if it is worked to an expert semi-race spec and
4500 if its a full-house, gas flowed, carb'd 300 degree + cammed motor. An electronic injected motor with Hillborn-style induction, very long rods, short stroke, and an A3 NASCAR/Cleveland style head that really flows might hit the 4000/3500 mark.

This gives SAE net (installed) power figures and works for most six and V8 motors.

Well, here is how to get the numbers. This system is very accurate to +/- 10% from my calculations, and is resonably easy to work through.

Here goes

9 things influence this 'k-value' above:

Intake manifold efficiency (ranges from 5%, 10%, 15%, 20%, 25% in most cases, with a rating of 1 for the best, to 5 for the worst). Pick the best choice form a rating 1 to 5 which replicates your intake. Most early 1.5" logs with 1" plugs will be rated at 5, while the later 1.75" hole logs with bigger welch plugs would be 4. A 250 2V is about 3, as is the 188 ME or 221 SP. An Offy 300 intake of any type should rate at 3. An independent runner EFI is about 2 for a stock 250 one, or 3 for an EFI 300. The Hillborne-type or Weber intakes are state of the art, rating at 1.

Degree of Carburation (ranges from about 15 cubic inches of engine to 1 square of carby venuri area to 44 to 70 to 98 to 125 for most carbs. A stock 300 I6 is about 125, rating at 5. A full on Triple Webered 250 can go down to 15, a rating of 1. Pick the best choice form a rating 1 to 5.

Camshaft Intensity (1= ~340+ degrees at lash, 2=~313, 3=~286, 4=~259, 5=~232). Pick the best choice form a rating 1 to 5.

Head Flow Subjective. 1= state of the art, 2=an aftermarket or reworked stock, 3= for a high-output, 4= most production head(s) for a stock lo-power version, 5=lousy. Pick the best choice form a rating 1 to 5.

ExhastSubjective. For branched controlled vortex with a primary size in excess of 0.8 times the intake valve is a 1. A standard aftermarket tubing header is a 2. A longer cast header with dual outlets can be 2 to 3 depending on the smoothness of the branching. A cast header with an outlet of in excess of the valve size is 4. A cast, undersized, sharp bended header is 5.

Examples of 1's are custom headers, 2 is an over the counter header, 3 is a great cast header, 4 is a ho-hum stocker, 5 is a nasty 1960 item.

Valve train configuration 1= Formula 1, 2 = DOHC 4V or State of the art Polyspheric or Hemi 2 valve, 3 = OHV wedge or SOHC wedge, 4 = Flat angle parallel valve OHV or lower rent wedge OHV, 5 = Side valve, unworked. Pick the best choice form a rating 1 to 5.

Rod Ratio 1=~2.1, 2 =~1.95, 3 =~1.80:1, 4= ~1.65, 5 = ~1.5.

Take the rod length, and divide it by the stroke. If you don't know, ask.

Compression Ratio 1= 15:1, 2 = 13:1, 3 = 10.5:1, 4= 9:1, 5 = 6.5:1

**Valve Size. Take intake valve size, and divide by bore size. 1= 0.54 or greater (4 or 5 valve per cylinder exceeds this often), 2= 0.50, 3= 0.47, 4= 0.44, 5 = 0.40. Pick the best choice form a rating 1 to 5. Side valves should use 5, because some valves are bigger but don't flow as well.

These 9 factors all get summed together to get a number, and then a scale factor is applied depending on the average of all 9 factors. So if you get a 41 for your Side Valve Ford 221, the average is 4.55. For the 1,2,3,4, and 5 averages there is a number you use multiply the sum of the nine factors.

For an average of 1, multiply the sum of the nine variables by 362. For 2, multiply by 250. For 3, multiply by 204. For 4, multiply by 228. For 5, multiply by 265. For anywhere in between, use math or make an approximation.

So our 221 Flattie, at 41, gets a multiplier of (228+265)/2, or 41*246.5

This adds up to 10107. Take the cubic capacity of the motor in question, multiply it by the peak power rpm (often 10% ofF* the maximum safe rpm for the engine, but it can vary a little) and divide it by one of that 'K-factor' we've found.

221*3200 = 70 hp net
10107

Try it. I'll do some examples, but it works pretty well.

Eg. 1
Jacks six carb Cross-flow 206 cuber.

Ratings were:-
Intake manifold efficiency= 1, (straight line tube, IR intake)
Degree of Carburation =1, (state of the art Motorbike CV's)
Camshaft Intensity =3, (wild street cam)
Head Flow =2, (stock with rebuild for lift and duration)
Exhast =2, (off-the shelf or simple custom)
Valve train configuration =2, (stock or roller rocker, altered for lift)
Rod Ratio =5, ( stock 1,505:1)
Compression Ratio =4, (About 10:1)
Valve Size =2. (**1.80/3.740= 0.48 or so )

using a score of 23, average of 2.44, multiplier is about 227. Hence the k-factor is 227*23, or 4994.

Rated at about 268 hp at 6500 rpm using this method.

So there you have it. A way of getting a power output without a dyno or the engine analyser.


*Edited. You guys were dead right. Take the maximum rev range, and often, the peak power is 90% of the maximum, or 10% off the maximum rpm for the power curve peak. It does vary a little. Sometimes its 80% of the maximum, or 20% off the maximum rpm for the power curve peak. Great to know you read this stuff gentlemen!

**And the valve sizes are divided by the bore diameter to get the valve size factor.

 

[Anonymous]

Xecute wrote "multiply it by the peak power rpm (often 10% of the maximum safe rpm for the engine, but it can vary a little)"

Bro, are you sure you don't mean 90%? For instance, my Toyota race engine revs to 10,500 rpm. 90% of that makes sense as it's close to the max power point, but 1500 rpm? It won't even idle at that speed!

 

[66Sprint6]

What about my car? Im not sure on the high RPM figure, but heres what I got.
66 head and block
intake hole bored out, ported and polished runners, port divider, milled .030, holley 2300 (350cfm) carb, cliffy dual out headers to dual flowmaster 40's. c4 tranny and stock rearend.
Anyone wanna take a crack at it or tell me what my RPM shoudl be for the bottom of the equation???
Matt

 

[Anonymous]

Bro, are you sure you don't mean 90%? For instance, my Toyota race engine revs to 10,500 rpm. 90% of that makes sense as it's close to the max power point, but 1500 rpm? It won't even idle at that speed!

Are you sure you don't mean 1050rpm?


-=Whittey=-

 

[Anonymous]

Whittey is right 1050 RPM

54Ford is right "(often 90% of the maximum safe rpm for the engine, but it can vary a little)"

XECUTE is RIGHT "(often 10% OFF the maximum safe rpm for the engine, but it can vary a little)"

GOOD JOB GUYS

 

[xctasy]

*Edited. You guys were dead right. Take the maximum rev range, and often, the peak power is 90% of the maximum, or 10% off the maximum rpm for the power curve peak. It does vary a little. Sometimes its 80% of the maximum, or 20% off the maximum rpm for the power curve peak.

Great to know you read this stuff gentlemen!

**And the valve sizes are divided by the bore diameter to get the valve size factor.

 

[xctasy]

66Sprint6 said:-

What about my car? Im not sure on the high RPM figure, but heres what I got.
66 head and block
intake hole bored out, ported and polished runners, port divider, milled .030, holley 2300 (350cfm) carb, cliffy dual out headers to dual flowmaster 40's. c4 tranny and stock rearend.
Anyone wanna take a crack at it or tell me what my RPM shoudl be for the bottom of the equation???
Matt

Ratings were:-
Intake manifold efficiency= 3.5, (even though cleaned up. Was about 4 as a 1.5" log)
Degree of Carburation =3, (much better than the 4 or 5 as a stocker)
Camshaft Intensity =4, (mild street cam)
Head Flow =4, (stock but blueprinted)
Exhast =3, (dual runner, much better than stock)
Valve train configuration =3, (stock or roller rocker, altered for lift)
Rod Ratio =5, ( stock 1,505:1)
Compression Ratio =3, (About 9:1)
Valve Size =4. (1.64/3.71= 0.44)

using a score of 32.5, average of 3.61, multiplier is about 218. Hence the k-factor is 218*32.5, or 7085.

I understand the peak rpm with this engine to be 5000 rpm. Rated at about 130 hp at 4550 rpm using this method. ([203*4550]/7085 = 130 hp)

It's rather close to what you may get in practice, although often the peak power level is 80% of the maximum, or 20% off the maximum. So it could be as low as 119 hp if you use 4167 rpm.

A Holley 350 cfm carb won't flow more than 125 hp unless the cam and head is set up for intake charge filling.

Hope this fits in with what you'd find using your numbers.

 

[66Sprint6]

Hey thanx X,
I was hoping, and had guessed in the 120-130hp range after all I did, but then I saw your post and wanted to try it out. You said the 350 carb wont flow more than 125hp without cam etc modifications, how about when I turbo it, will it flow more then even tho Im goin to prolly stick with a stock cam to keep it happy? Whats your take?
Matt

 

[xctasy]

If its a draw through, it will need as much carburation as a normal bigger cube engine. If you are looking for 200 hp, you'll need a 500 cfm 2-bbl.

When you add a turbo, that calculated K- factor of 7085 will imporove by a factor equal to the boost ratio, minus the heating factor. So a 10 pound boost via a turbo will need
10+14.7 = 1.68
14.7

This k-factor could be a drop off~ 1.5 if the intake air is very hot.

So 7085 could drop to, say, 4723, or from about 119-130 hp up to 178-195 hp, depending on the peak rpm. So a carb of about 1.5 times bigger than a 350 Holley should be used. Perhaps a 500 Holley for a draw through. There are many sound reasons for a bigger carb to be used for a draw through, which David Vizard goes into in his "How to Modify Fords SOHC"

I didn't want to get into too much other stuff, as it wasn't designed around turbos because there are many different ways to analyse them. Anyone who knows engines can face off my formula approach against an engine hp program. I'm confident this is very, very accurate.

I suggest you go through a cross check with some one else for your own peace of mind. If it works, then it'll be clear to everyone. If it is not accurate, then some-one will have the info to share.

I'd just like to say that HP calculations are not that difficult, and they canbe done by proforma, without having to grab a quarter grand program.

 

[66Sprint6]

Thanx again Xecute,
Ill be running blow through, but I might step up to a 500cfm carb anyways. I am not sure, but Ill see. Your calculations have gotten numbers that I almost expected to get out of this buildup anyways so I believe you have a good method
Matt

 

[Anonymous]

Are you sure you don't mean 1050rpm?

Yep...see how easy it is to screw up numbers? :roll:

 

[xctasy]

You betcha. Just running your 1600 4AGE through the program now. I'll get back to ya!

 

[Anonymous]

Psst, I can already tell you it's not very good. The bore is too small...

 

[xctasy]

For the 1587 cc 4AGE you have, here were my Ratings:-
Intake manifold efficiency= 1,
Degree of Carburation =1,
Camshaft Intensity =1,
Head Flow =1,
Exhast =1,
Valve train configuration =1,
Rod Ratio =2, ( stock 1,578:1, but I'm sure you have a better rod ratio.The stock rods are around 4.78", and I'm sure your running over 5" rods for a ratio better than 1.65:1)
Compression Ratio =1, (About 13:1?)
Valve Size =1.

using a score of 10, average of 1.111, multiplier is about 372.7. Hence the k-factor is 372.7*10.0, or 3727.

I understand the peak rpm with this engine to be 9500 rpm. Rated at about 247 hp at 9500 rpm using this method. ([97*9500]/3727 = 247 hp)

It's rather close to what you may get in practice, although often the peak power level is 90% of the maximum, or 10% off the maximum. Wasn't that 10300? 9500 rpm is therefore the peak.

The formula isn't related to bore:stroke ratio at all, but it does have another feature which compensates, which I will . More power is to be had from rod optimisation, 11 percenter between a good and a bad one. I could add a tenth term for bore:stroke ratio, if you want. But from what I've seen, the peak rpm will grow to a higher level, and this governs the power, not an additional factor for this.

An example was the old F5000 cars with Chevy Small blocks. On flat-out circuits, a 400 block with a 305 cube 4.125:2.85 bore:stroke. On tight circuits, a 302 block with a 305 cube 4.020:3.00 bore:stroke. The rod ratios were different, but the rev range was different by quite a few hundred rpm in favour of the 400 block. So the extra revs bought extra power.

 

[66Sprint6]

Hey X,
How much HP do you think I would be running if I added roller rockers, hydro. lifters, chrome molly pushrods, Holley 500 and a t04b turbo with intercooler pushing about 7-10psi? All that on top of what I have done. Think you could help me out with this prediction? Also, Im not sure what Ill do about cam, what would you suggest for my turbo build, and then add that to the equation.
Matt

 

[xctasy]

Can't say for sure. When you wind down the boost to about 7 pounds, it makes a blow though carb mmore of an option. I'd say that if you could get around 125 hp as a stocker, more if it had the right cam. With seven pounds to ten pounds, you will go up to the 165 or so with 7lb's, to the 178 -195 hp mark easily with 10 lb's. But the engine is limited by detonation, not the boost. The TO4B is a very big turbo, possibly too big. A split pulse TO3 may be more streetable. The roller rockers are just durability, you won't see extra power.

Jack said a while back that splitting the intake runners barrel to barrel is a good idea. I'll go one further. The stock heat stove is a power looser, and I recon, in a turbo conversion, that is the worst thing you can have, especially on a cast iron intake. So the solution is to get two separate blow through carbs, or a draw through which then get channeled into a dual branch intake, feeding the manifold, blocked off at the original hole, and going to the tracts between pistons 2 and 3, and 4 and 5.

On an engine set up as you describe, mit 500 Holley and good gear, I'd say keep it to 7 pounds, and you'd get an good 175 hp, but the best thing is the torque. 175 lb-ft from a good log 200, could get a stock 302 V8 eating 245 lb-ft without a care.

I'll get back to the horsepower party.

 

[66Sprint6]

Torque is good,
I am hoping to have things worked out to get the turbo project runnin by this time next year. Would be nice, but I drive this car everyday, its my only car so I want it to be reliable as well. Oh well, hopefully I can make it fast, fun and reliable all at the same time
Matt

 

[xctasy]

http://www.bgsoflex.com/auto.html has a great estimation program for HP.

If 66Sprint6's engine is used, you get these figures.

Rough Horsepower Calculator by Bowling and Grippo
Engine Displacement (CID) is 203
Mean Compression ratio is 8.5
Engine Revolutions Per Minute is 4000
Computation Results:
Computed Engine HP is 126

If you use 4167 rpm power peak, 131 hp, or the 4550 rpm peak, 143 hp.

Of course, this assumes a good head efficiency, which isn't allowed for in this program. Mine makes an attempt at doing this, and is quite conservative.

Turbos are a whole nudder thang, since they are really gas turbines share a combustion chamber with a piston engine. If you spike a huge turbo with an over advanced, boost inducing rich condition, V8 guys have gotten 1400 hp from 383 cubes!

 

[xctasy]

I'm still doing a sensitivity check on this. Its got no real input for the cam lift, which governs power more than duration alone.

Here is fordmuscle83's Falcon x-flow engine with a 280 degree cam with 215 deg duration at 50 thou lift. Cam is 510 thou lift at valve. Compression is 9.5, and carb is 500 cfm 2-bbl. Headers and a mild head clean-up with the bigger XF valves on an XE head.

Remeber the K-values?

Take the cubic capacity of the motor in question, multiply it by the peak power rpm (10% ofF* the maximum safe rpm for the engine) and divide it by one of the following factors:
7000 if your six is box stock,
6000 if its got a good street intake manifold and exhast,
5500 it is worked with a cam that is over 260 degrees and very good breathing,
5000 if it is worked to an expert semi-race spec and
4500 if its a full-house, gas flowed, carb'd 300 degree + cammed motor. An electronic injected motor with Hillborn-style induction, very long rods, short stroke, and an A3 NASCAR/Cleveland style head that really flows might hit the 4000/3500 mark.

9 things influence this 'k-value' above:

Intake manifold efficiency, rated at 3 (ranges from 5%, 10%, 15%, 20%, 25% in most cases, with a rating of 1 for the best, to 5 for the worst). Pick the best choice form a rating 1 to 5 which replicates your intake. Most early 1.5" logs with 1" plugs will be rated at 5, while the later 1.75" hole logs with bigger welch plugs would be 4. A 250 2V is about 3, as is the 188 ME or 221 SP. An Offy 300 intake of any type should rate at 3. An independent runner EFI is about 2 for a stock 250 one, or 3 for an EFI 300. The Hillborne-type or Weber intakes are state of the art, rating at 1.

Degree of Carburation, rated at 3 (ranges from about 15 cubic inches of engine to 1 square of carby venturi area to 44 to 70 to 98 to 125 for most carbs. A stock 300 I6 is about 125, rating at 5. A full on Triple Webered 250 can go down to 15, a rating of 1. Pick the best choice form a rating 1 to 5.

Camshaft Intensity, picked 3.5 (1= ~340+ degrees at lash, 2=~313, 3=~286, 4=~259, 5=~232). Pick the best choice form a rating 1 to 5.

Head Flow, Subjective, but rated at 3. 1= state of the art, 2=an aftermarket or reworked stock, 3= for a high-output, 4= most production head(s) for a stock lo-power version, 5=lousy. Pick the best choice form a rating 1 to 5.

Exhast, Subjective, but rated at 2. For branched controlled vortex with a primary size in excess of 0.8 times the intake valve is a 1. A standard aftermarket tubing header is a 2. A longer cast header with dual outlets can be 2 to 3 depending on the smoothness of the branching. A cast header with an outlet of in excess of the valve size is 4. A cast, undersized, sharp bended header is 5.

Examples of 1's are custom headers, 2 is an over the counter header, 3 is a great cast header, 4 is a ho-hum stocker, 5 is a nasty 1960 item.

Valve train configuration, rated at 2. 1= Formula 1, 2 = DOHC 4V or State of the art Polyspheric or Hemi 2 valve, 3 = OHV wedge or SOHC wedge, 4 = Flat angle parallel valve OHV or lower rent wedge OHV, 5 = Side valve, unworked. Pick the best choice form a rating 1 to 5.

Rod Ratio, easy, its 5, pretty crook! 1=~2.1, 2 =~1.95, 3 =~1.80:1, 4= ~1.65, 5 = ~1.5. Take the rod length, and divide it by the stroke. If you don't know, ask.

Compression Ratio rated at 4. 1= 15:1, 2 = 13:1, 3 = 10.5:1, 4= 9:1, 5 = 6.5:1

**Valve Size. Take intake valve size, and divide by bore size. 1= 0.54 or greater (4 or 5 valve per cylinder exceeds this often), 2= 0.50, 3= 0.47, 4= 0.44, 5 = 0.40. Pick the best choice form a rating 1 to 5. Side valves should use 5, because some valves are bigger but don't flow as well.

These 9 factors all get summed together to get a number, and then a scale factor is applied depending on the average of all 9 factors. So if you get a 27.5 for your X-flow Ford 250, the average is 3.10. For the 1,2,3,4, and 5 averages there is a number you use multiply the sum of the nine factors.

For an average of 1, multiply the sum of the nine variables by 362. For 2, multiply by 250. For 3, multiply by 204. For 4, multiply by 228. For 5, multiply by 265. For anywhere in between, use math or make an approximation.

So our 250 x-flow adds up to 27.5, or an average of 3.1, and its gets a multiplier of (204) or 27.5*204

This adds up to 5610. Take the cubic capacity of the motor in question (250), multiply it by the peak power rpm (often 10% off the maximum safe rpm for the engine [5400 rpm], but it can vary a little. This is 4900 rpm) and divide it by one of the 'K-factor' we've found.

This gives SAE net (installed) power figures and works for most six and V8 motors.

Answer for the 280 degree high lift camed engine is:-

250*4900 = 218 hp net, the most you could hope for.
_5610

The funny thing is there is a similar cam with only 429 thou lift, and I can't calculate the power as this thing has no cam lift input. Hmmmm. From just the head cfm at 430 lift verses 510 thou lift is 35 cfm, enough for a loss of 35 hp, or 183 hp.

 

[Anonymous]

** Suzuki GS1100 4valve **
Intake manifold efficiency= 1 (4 fat individual carbs)
Degree of Carburation = 1 (4 nicely tuned Mikunis)
Camshaft Intensity = 4 (Aftermarket 268 cam, closer to 4 than 3)
Head Flow = 2 (25+ year old design)
Exhast = 2 (SuperTrapp w/no baffles)
Valve train configuration =2 (DOHC 4v)
Rod Ratio = 3 (guess, can't seem to find rod length)
Compression Ratio = 4 (9.5:1)
Valve Size = 1 (27mm*2/66mm=0.818)

Total = 20, Average = 2.222222222

20 * 275 = 5500

65.6cid * 8000 / 5500 = 95.4hp. Estimated (because I used a larger than stock cam) would be about 120hp. Of course I guessed on the rod ratio, but I doubt it's too long. Gotta keep it all packaged.


-=Whittey=-