Carpenter Questions

[Dr.D]

It’s designed to improve the clearance the brute had.

Odd but in a sexy octopus hugging the engine way.

Similar sound to the brute.

Yes, it’s warmer than stock, all aftermarket pipes are.

I like odd.

 

[Tripps]

Same bore, same stroke, and same RPMs. It moves the same amount of air.

Ahh, I'm not sure about that, to get to full rpms quicker, it would have to move a lot more air. Think about it, stock is same bore, stroke, and up to a point, same rpms? Not positive about this, but just using logic, I think. Time is a factor too.

 

[leatal]

Ahh, I'm not sure about that, to get to full rpms quicker, it would have to move a lot more air. Think about it, stock is same bore, stroke, and up to a point, same rpms? Not positive about this, but just using logic, I think. Time is a factor too.

Me thinks a stock concave piston setup has more volume in the cylinder than a setup with high compression pistons (at same RPM), thus will actually move more air but at a much less efficient rate (more volume but less mass at full compression). As a matter of fact, my stock engine has more CCs than you guys with high compression pistons, high performance cams, and/or decked heads. The same should apply to the Carpenter engines with just cams vs his engines with the full cam/piston package. So for bragging rights: Sure you have more power but my engine will always be bigger!

 

[ruzzle]

Me thinks a stock concave piston setup has more volume in the cylinder than a setup with high compression pistons (at same RPM), thus will actually move more air but at a much less efficient rate (more volume but less mass at full compression). As a matter of fact, my stock engine has more CCs than you guys with high compression pistons, high performance cams, and/or decked heads. The same should apply to the Carpenter engines with just cams vs his engines with the full cam/piston package. So for bragging rights: Sure you have more power but my engine will always be bigger!

"Capacity" of an engine is SWEPT volume of the pistons. Those things don't make any difference.

 

[Tripps]

Sure you have more power but my engine will always be bigger!

I got something bigger for you.

 

[scot in exile]

Me thinks a stock concave piston setup has more volume in the cylinder than a setup with high compression pistons (at same RPM), thus will actually move more air but at a much less efficient rate (more volume but less mass at full compression). As a matter of fact, my stock engine has more CCs than you guys with high compression pistons, high performance cams, and/or decked heads. The same should apply to the Carpenter engines with just cams vs his engines with the full cam/piston package. So for bragging rights: Sure you have more power but my engine will always be bigger!

And do not forget slower also

 

[Claviger]

Air volume would not be the same. The increase lift of the bigger cams will allow more airflow thus creating more horsepower.

The other option would be increasing duration and overlap but I know the bigger cams are mostly lift increases not valve event timing.

 

[Claviger]

So I've been a little busy running numbers to try and understand some things about the state of tune of various rocket configurations. I'm using real world dyno tests multiplied by 1.15 to represent drive train loss, though, the R3 likely has more loss than 15%. Lets start with my most recent build and Bob's dyno numbers:

266fwhp (265 kit with CES instead of Brutes)

Peak power = 7200 RPM
Fuel flow at 13:1 AFR = 69.9L/hr or 117.5lb/hr
BSFC with those figures = .441 @ peak power

REQUIRED VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

1.097 (109.7%) VE = (1,105,792) / (1,050,000)

Interesting, we're achieving greater than 100% VE, and nearing the expected practical limit of 115% VE.

-----------------------------

Now run it with the Brute

288fwhp

Peak Power = 7750
Fuel flow at 13:1 AFR = 75L/hr or 127.3lb/hr
BSFC with those figures = .436 @ peak power

REQUIRED VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

1.089 (108.9%) VE = (1,182,386) / (1,085,000)

So, even more interesting is that the increase of 19 hp gain isn't a VE increase, its clearly an effect of adjusting the torque peak upwards to take advantage of the effect of RPM on HP, not a big surprise but interesting to see that there is, indeed, a trade-off going on.

-----------------------------

Now lets check out a stock engine bike tuned with CES and RAMAIR:

181fwhp

Peak power = 6200 RPM
Fuel flow at 13:1 AFR = 54.4L/hr or 92.3lb/hr
BSFC with those figures = .51 @ peak power

REQUIRED VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

1.0008 (100%) VE = (868,729) / (868,000)

Now we're getting there, this is a touch over 100% VE and it has extended the peak HP upwards, taking advantage of both higher efficiency and RPM to make more HP.

-----------------------------

Next looking at the stock bike with a Lushy tune, to avoid electronic limits messing with the hardware capability and show what the "best case" will be on a stock bike:

146fwhp

Peak power = 5800 RPM
Fuel flow at 13:1 AFR = 49L/hr or 83.1lb/hr
BSFC with those figures = .57 @ peak power

REQUIRED VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

0.964 (96.4%) VE = (783,183) / (812,000)

So we see a significant gain in VE over stock with all setups, no surprises honestly.

-----------------------------

For ****s n giggles lets look at Mizzy's bike, as it goes about making big NA power a bit differently than a Carpenter setup, and has an absolutely gorgeous torque curve!

256fwhp

Peak power = 7200 RPM
Fuel flow at 13:1 AFR = 69.9L/hr or 117.5lb/hr
BSFC with those figures = .459 @ peak power

REQUIRED VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

1.097 (109.7%) VE = (1,106,121) / (1,008,000)

Quite good and even without running all the math, just looking at his graph, I can tell you his VE is better below peak power than the 265 kit, meaning he'll get better MPG and make more torque below full throttle.

-----------------------------

Finally, lets take a peek at the TTS development bike:

394.5fwhp

Peak Power = 6150
Fuel flow at 11.8 AFR = 111L/hr or 188.4lb/hr
BSFC with those figures = .48 @ peak power

REQUIRED VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

2.069 (206.9%) VE = (1,779,808) / (861,000)

Ahh the joys of boost

Here is a basis for comparison on an F22 Honda S2000, a motor known to be extremely efficient and way overachieving for its' displacement:
83% @ 2000
90% @ 3300
88% @ 4600
95% @ 5900
102% @ 7200
113% @ 8500

Why does all this matter?

BSFC is a good indication of the state of tune of your motor, so you can tell how efficiently it's converting air and fuel into HP relative. For a point of BSFC reference, a stock Hyabusa BSFC is about 0.469 with a VE around 1.035 or 103.5%.

.55 to .65 - Most supercharged or Turbocharged engines
.48 to .55 - Stock and moderate performance engines
.45 to .50 - Performance Engines with good heads
.38 to .45 - Most race motors
.35 to .38 Pro/Stock-style engines

Well, knowing VE allows you to do some calculations, such as exhaust dimensions and intake dimensions and predict the outcome. Below is an estimator that gives you an idea of what to shoot for when designing your headers, I've run it once with the stock cam and once with a mildly increased cam, Bob's told me himself the exhaust side isn't particularly aggressive, but you can see the results for yourself:

Stock Exhaust Cam:

Bigger Cam:

Theoretical Giant Cam:

So, FINALLY, you can see why 2" primaries ACTUALLY MATTER to a built motor. Even with a massive cam, you'll see that the 2" is still important and technically, they may be a bit undersized since 2" OD = 1.875" ID.

Stock Tuned Bike:

This is the stock bike, you can see, it wants bigger than stock primaries. No surprises, but it does show WHY we get such good gains going with any header bigger than stock on a stock motor, it wants it!!

Conveniently, look at 1.67 primary diameter, well, 1.75 OD pipes are 1.625 ID, and now it makes sense why CES and others have chosen 1.75" for their primaries, it matches nicely to the stock motor, but it also shows why the 2" primaries can have a small gain over 1.75" even on a stock motor.

Just bored and playing with numbers

EDIT: Fixed some errors

 

[warp9.9]

MMMM you one smart Hombre

 

[Claviger]

MMMM you one smart Hombre

It's just been really bugging me about the 2" primary thing, I needed to math it out for myself to clearly see if it is in-fact beneficial or an ego thing.

A thought just occurred to me, the stock injectors are REALLY at the ragged edge with the 265 kit and Brute.

330cc @ 80% duty cycle

330cc * 1.2 (to find 100% duty) = 396cc

396cc * 3 = 1188cc

75 L/hr = 1250cc

soooo technically they're a tiny bit too small