Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums - Camaro5.com
 
TireRack
Go Back   Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums - Camaro5.com > Engine | Drivetrain | Powertrain Technical Discussions > Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons


Reply
 
Thread Tools
Old 11-27-2008, 10:03 AM   #1
rayhawk

 
rayhawk's Avatar
 
Drives: Camaro SS
Join Date: Aug 2008
Location: Miami
Posts: 1,060
BMEP-Or why you only need 1 camshaft

Check out this site. It is about aircraft engines, but he has a lot of good technical information about engine design. It does'nt all apply to street car engines, but interesting either way. I thought it was funny that an Indy engine only makes 214 ft lbs of torque at 17000 rpm! Considering how useless this engine would be in a street car, it shows that 2 valves per cylinder is'nt so bad after all when you look at it from the BMEP.

Or another way to look at it, the torque available (and accordingly the hp) is as simple as:

Torque(ft-lbs)=BMEP*Disp(ci)/150.8

Of course, the BMEP is all dependent on engine design, but it gives you an idea how much a small displacement engine has to overcome to catch up to a larger engine.

He also explains volumetric efficiency, what the practical limits are, and the tradeoffs between different engine designs, and a bunch of other topics. They also use a lot of LS engines for their conversions.

http://www.epi-eng.com/piston_engine..._yardstick.htm

- Brake Mean Effective Pressure -
BMEP: An important performance yardstick
We have covered the topics of Thermal Efficiency and Volumetric Efficiency as methods for estimating the potential output of a given engine configuration.

Brake Mean Effective Pressure (BMEP) is another very effective yardstick for comparing the performance of one engine to another, and for evaluating the reasonableness of performance claims or requirements.

The definition of BMEP is: the average (mean) pressure which, if imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output.

Note that BMEP is purely theoretical and has nothing to do with actual cylinder pressures. It is simply an effective comparison tool.

If you work through the arithmetic, you find that BMEP is simply a multiple of the torque per cubic inch of displacement. A torque output of 1.0 lb-ft per cubic inch of displacement equals a BMEP of 150.8 psi. in a four-stroke engine and 75.4 psi. in a two-stroke engine.

(The discussion on the remainder of this page is with respect to four-stroke engines, but it applies equally to two strike engines if you simply substitute 75.4 everywhere you see 150.8)

If you know the torque and displacement of an engine, a very practical way to calculate BMEP is:

BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci)

(Equation 8)

This tool is extremely handy to evaluate the performance which is claimed for any particular engine. For example, the 200 HP IO-360 (360 CID) and 300 HP IO-540 (540 CID) Lycomings make their rated power at 2700 RPM. At that RPM, the rated power requires 389 lb-ft and 584 lb-ft of torque respectively. (If you don't understand that calculation, CLICK HERE)

From those torque values, it is easy to see (from Equation 8 above) that both engines operate at a BMEP of about 163 PSI. (1.08 lb-ft of torque per cubic inch) at peak power. The BMEP at peak torque is slightly greater.

For a long-life, naturally-aspirated, gasoline-fueled, two-valve-per-cylinder, pushrod engine, a BMEP over 200 PSI is difficult to achieve and requires a serious development program and very specialized components.

For comparison purposes, let's look at what is commonly believed to be the very pinnacle of engine performance: Formula-1 (Grand Prix).

An F1 engine is purpose-built and essentially unrestricted. For 2006, the rules required a 90° V8 engine of 2.4 liters displacement (146.4 CID) with a maximum bore of 98mm (3.858) and a required bore spacing of 106.5 mm (4.193). The resulting stroke to achieve 2.4 liters is 39.75 mm (1.565) and is implemented with a 180° crankshaft. The typical rod length is approximately 4.016 (102 mm), for a Rod/Stroke ratio of about 2.57. These engines are typically a 4-valve-per cylinder layout with two overhead cams per bank, and pneumatic valvesprings. In addition to the few restrictions stated above, there are the following additional restrictions: (a) no beryllium compounds, (b) no MMC pistons, (c) no variable-length intake pipes, (d) one injector per cylinder, and (e) the requirement that one engine last for two race weekends.

At the end of the 2006 season, most of these F1 engines ran up to 20,000 RPM in a race, and made in the vicinity of 750 HP. One engine for which I have the figures made 755 BHP at an astonishing 19,250 RPM. At a peak power of 755 HP, the torque is 206 lb-ft and peak-power BMEP would be 212 psi. (14.63 bar). Peak torque of 214 lb-ft occurred at 17,000 RPM for a BMEP of 220 psi (15.18 bar). There can be no argument that 212 psi at 19,250 RPM is truly amazing.

However, let's look at some astounding domestic technology. The 2006 Nextel Cup engine is a severely-restricted powerplant, being derived from production components. It uses a production-based cast-iron 90° V8 block and 90° steel crankshaft, with a maximum displacement of 358 CID (5.87 liters). A typical configuration has a 4.185" bore with a 3.25" stroke and a 6.20" conrod (R/S = 1.91). Cylinder heads are similarly production-based, limited to two valves per cylinder, but highly developed. The valves are operated by a single, engineblock-mounted, flat-tappet camshaft (that's right, still no rollers as of 2007) and a pushrod / rocker-arm / coil-spring valvetrain. It is further hobbled by the requirement for a single four-barrel carburetor. Electronically-controlled ignition is not allowed, and there are minimum weight requirements for the conrods and pistons.

How does it perform? At the end of the 2006 season, the engines were producing in the neighborhood of 825 HP at 9000 RPM (and could produce more at 10,000 RPM, but engine RPM has been restricted by means of a rule limiting the final drive ratio at each venue). 825 HP at 9000 RPM requires 481 lb-ft of torque, for a peak-power BMEP of nearly 203 PSI (14.0 bar). Peak torque was typically about 520 lb-ft at 7500 RPM, for a peak BMEP of over 219 psi (15.1 bar).

THAT is truly astonishing. Compare the F1 engine figures to the Cup engine figures for a better grip on just how clever these Cup engine guys are.

To appreciate the value of this tool, suppose someone offers to sell you a 2.8 liter (171 cubic inch) Ford V6 which allegedly makes 230 HP at 5000 RPM, and is equipped with the standard iron heads and an aftermarket intake manifold and camshaft. You could evaluate the reasonableness of this claim by calculating that 230 HP at 5000 RPM requires 242 lb-ft of torque (230 x 5252 ÷ 5000), and that 242 lb-ft. of torque from 171 cubic inches requires a BMEP of 213 PSI (150.8 x 242 ÷ 171).

You would then dismiss the claim as preposterous because you know that if a guy could do the magic required to make that kind of performance with the stock heads and intake design, he would be renowned as one of the pre-eminent engine gurus in the world. (You would later discover that the engine rating of "230" is actually "Blantonpower", not Horsepower.)

As a matter of fact, in order to get a BMEP value of 214 from our aircraft V8, we had to use extremely well developed, high-flowing, high velocity heads, a specially-developed tuned intake and fuel injection system, very well developed roller-cam profiles and valve train components, and a host of very specialized components which we designed and manufactured.
__________________
rayhawk is offline   Reply With Quote
Old 11-27-2008, 10:12 AM   #2
MerF
Go Rays!
 
MerF's Avatar
 
Drives: 03 Trailblazer
Join Date: May 2007
Location: St Pete, Florida
Posts: 2,533
I'm in Physics and C-Programming and I am a new employee at a technical plant as a trainer learning oodles of crap there.

So I'm pissed that you made me think on my day off.

Other than that....cool stuff.
MerF is offline   Reply With Quote
Old 11-28-2008, 08:56 PM   #3
radz28
Petro-sexual
 
radz28's Avatar
 
Drives: Ultra-Grin
Join Date: Oct 2006
Location: Crazy Coast
Posts: 15,156
Quote:
Originally Posted by MerF View Post
I'm in Physics and C-Programming and I am a new employee at a technical plant as a trainer learning oodles of crap there.

So I'm pissed that you made me think on my day off.

Other than that....cool stuff.


I want to shoot myself in the face after reading the beginning of that. I started to read, then my eyes started bleeding, and I got an aneurysm. GOD! I even had to go to Dictionary.com to learn how to spell that! Thanks a lot
__________________

'20 ZL1 Black "Fury"
A10, PDR, Exposed CF Extractor
Magnuson Magnum DI TVS2650R // TooHighPSI Port Injection // FF // Katech Dual In-Tank // Soler 103 // PLM Heat Exchanger // ZLE Cradle bushings // BMR Chassis-Suspension Stuff // aFe Bars // Diode Dynamics LEDs // ACS Composites Guards // CF Dash // Aeroforce // tint // other stuffs
radz28 is offline   Reply With Quote
Old 11-28-2008, 09:21 PM   #4
DGthe3
Moderator.ca
 
DGthe3's Avatar
 
Drives: 05 Grand Am GT
Join Date: Jul 2007
Location: Niagara, Canada
Posts: 25,372
Send a message via MSN to DGthe3
I read it twice. I think I understand.
__________________
Note, if I've gotten any facts wrong in the above, just ignore any points I made with them
__________________
Originally Posted by FbodFather
My sister's dentist's brother's cousin's housekeeper's dog-breeder's nephew sells coffee filters to the company that provides coffee to General Motors......
........and HE WOULD KNOW!!!!
__________________

Camaro Fest sub-forum
DGthe3 is offline   Reply With Quote
Old 11-28-2008, 10:34 PM   #5
rayhawk

 
rayhawk's Avatar
 
Drives: Camaro SS
Join Date: Aug 2008
Location: Miami
Posts: 1,060
Sorry guys...I am an engineer so I like the technical stuff. I think it was interesting though when you look at the comparisons between the nascar and indy style engines. I was just trying to show why there really is no replacement for displacement, and that there is a lot you can do with 2 valve technology.
__________________
rayhawk is offline   Reply With Quote
Old 11-28-2008, 10:45 PM   #6
Mr Twisty


 
Mr Twisty's Avatar
 
Drives: the 2nd amendment home
Join Date: May 2008
Location: OK
Posts: 14,707
Quote:
Originally Posted by radz282003 View Post
I even had to go to Dictionary.com to learn how to spell that!
t-h-a-t
__________________
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
-- Benjamin Franklin
Mr Twisty is offline   Reply With Quote
Old 11-28-2008, 11:39 PM   #7
DGthe3
Moderator.ca
 
DGthe3's Avatar
 
Drives: 05 Grand Am GT
Join Date: Jul 2007
Location: Niagara, Canada
Posts: 25,372
Send a message via MSN to DGthe3
Quote:
Originally Posted by rayhawk View Post
Sorry guys...I am an engineer so I like the technical stuff. I think it was interesting though when you look at the comparisons between the nascar and indy style engines. I was just trying to show why there really is no replacement for displacement, and that there is a lot you can do with 2 valve technology.
I'm half way to becoming an engineer. Officially I'm an engineer in training.
__________________
Note, if I've gotten any facts wrong in the above, just ignore any points I made with them
__________________
Originally Posted by FbodFather
My sister's dentist's brother's cousin's housekeeper's dog-breeder's nephew sells coffee filters to the company that provides coffee to General Motors......
........and HE WOULD KNOW!!!!
__________________

Camaro Fest sub-forum
DGthe3 is offline   Reply With Quote
Old 11-28-2008, 11:56 PM   #8
rayhawk

 
rayhawk's Avatar
 
Drives: Camaro SS
Join Date: Aug 2008
Location: Miami
Posts: 1,060
Quote:
Originally Posted by DGthe3 View Post
I'm half way to becoming an engineer. Officially I'm an engineer in training.
I don't know what type of engineering you are doing, but if you get a chance, I recommend you take some sort of Internal Combustion Engines course. For mechanical engineering, it counts as a thermodynamic elective (or it did for me anyway) and you get to learn about cars. I loved it.
__________________
rayhawk is offline   Reply With Quote
Old 11-29-2008, 12:38 AM   #9
DGthe3
Moderator.ca
 
DGthe3's Avatar
 
Drives: 05 Grand Am GT
Join Date: Jul 2007
Location: Niagara, Canada
Posts: 25,372
Send a message via MSN to DGthe3
Quote:
Originally Posted by rayhawk View Post
I don't know what type of engineering you are doing, but if you get a chance, I recommend you take some sort of Internal Combustion Engines course. For mechanical engineering, it counts as a thermodynamic elective (or it did for me anyway) and you get to learn about cars. I loved it.
Mechanical, mechatronics option. I was going to take a course in auto eng as my elective last year but it conflicted with my required courses. I'm out of school now, working full time, getting my apprenticeship hours in.
__________________
Note, if I've gotten any facts wrong in the above, just ignore any points I made with them
__________________
Originally Posted by FbodFather
My sister's dentist's brother's cousin's housekeeper's dog-breeder's nephew sells coffee filters to the company that provides coffee to General Motors......
........and HE WOULD KNOW!!!!
__________________

Camaro Fest sub-forum
DGthe3 is offline   Reply With Quote
Old 11-29-2008, 10:04 PM   #10
MerF
Go Rays!
 
MerF's Avatar
 
Drives: 03 Trailblazer
Join Date: May 2007
Location: St Pete, Florida
Posts: 2,533
You dirty mech engineers.

EE all the way (Computer Sciences).
MerF is offline   Reply With Quote
Old 11-30-2008, 04:18 PM   #11
CamaroSpike23
Truth Enforcer
 
CamaroSpike23's Avatar
 
Drives: anything I can get my hands on
Join Date: Sep 2006
Location: anywhere and everywhere
Posts: 22,797
Send a message via Yahoo to CamaroSpike23
Quote:
Originally Posted by rayhawk View Post
I don't know what type of engineering you are doing, but if you get a chance, I recommend you take some sort of Internal Combustion Engines course. For mechanical engineering, it counts as a thermodynamic elective (or it did for me anyway) and you get to learn about cars. I loved it.
sweet, thats good to know. im working on my Mech Eng. along with a backup in Aerospace eng.
__________________
Never race anything you can't afford to light on fire and push off a cliff
A group as a whole tends to be smarter than the smartest person in that group until one jackass convinces everyone otherwise.
Quote:
Originally Posted by BowtieGuy View Post
Nobody makes CamaroSpike happy. You just disgust him a little less than other people.

Quote:
Originally Posted by WheelmanSS View Post
Post count is truly an accurate measure of how cool someone is on the Internet.
Quote:
Originally Posted by Greg Norris View Post
I piss excellence
and fart awesomeness
"You can think I'm wrong, but that's no reason to quit thinking.”
Quote:
Originally Posted by Overflow View Post
But not all people were born awesome like you, Spike.
CamaroSpike23 is offline   Reply With Quote
Old 11-30-2008, 04:24 PM   #12
TheClassicCarKid

 
TheClassicCarKid's Avatar
 
Drives: V45
Join Date: Feb 2007
Location: Southern California
Posts: 1,270
cool : D
I'll simplify it: A 6.2L engine>5.0L ; )
__________________
Quote:
Originally Posted by 1320junkie View Post
All of the stang guys in one thread..wow..lol
.

Last edited by TheClassicCarKid; 11-30-2008 at 08:16 PM.
TheClassicCarKid is offline   Reply With Quote
Old 11-30-2008, 08:14 PM   #13
Mr Twisty


 
Mr Twisty's Avatar
 
Drives: the 2nd amendment home
Join Date: May 2008
Location: OK
Posts: 14,707
That's too much math, just let the dyno figure it out.
__________________
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
-- Benjamin Franklin
Mr Twisty is offline   Reply With Quote
Old 11-30-2008, 08:55 PM   #14
crazz28
 
crazz28's Avatar
 
Drives: '10 Camaro SS/RS, '10 GMC Sierra
Join Date: Jan 2008
Location: Saskatchewan, Canada
Posts: 213
Quote:
Originally Posted by MerF View Post
You dirty mech engineers.

EE all the way (Computer Sciences).
Mining Engineering FTMFW!!!

Cool read though, and for all those people that didn't grow up in the "cubes" era:

BMEP = 150.8 x TORQUE (lb-ft) / (61.0237 (ci/L) x DISPLACEMENT (L))
or
BMEP = 2.4712 x TORQUE (lb-ft) / DISPLACEMENT (L) = (psi)
__________________
CGM/BLACK INTERIOR 2SS/RS LS3 M6
TTi/GMS Twin Turbo, Borla S-Type mufflers, Hurst Shifter
crazz28 is offline   Reply With Quote
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Camaro ls3 news...true or false? Dark Knight Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons 74 06-05-2008 05:29 PM
So...the L76... Mr. Wyndham Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons 51 04-07-2008 01:21 PM
VVT on the new Camaro Casull Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons 19 04-01-2007 01:55 PM


All times are GMT -5. The time now is 01:30 PM.


Powered by vBulletin® Version 3.8.9 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.