HORSEPOWER TIPS

[SassyCassie14]

I get these monthly emails and thought I'd share them with y'all......

 

 

HORSEPOWER TIPS:

 

The Engine Masters Challenge is a yearly engine

building contest created by Popular Hot Rodding

magazine. 50 engine builders attempt to build an

engine that produces the highest average horsepower

and torque over a given rpm range.

 

On a dynamometer, you can analyze peak power and

torque, or you can analyze average power and torque

over a given rpm range; this competition only cares

about the "average". Many engine builders and racers

worship the false god of "peak". When trying to

increase an engines average power, a builder quickly

learns that changes with carburetors, headers, and

spacers most often only teeter-totter the curve. This

alters peak but does not change average. A 408ci

engine might have a peak HP of 650 and a peak TQ of

550, but the average total for an rpm range of 2500 to

6500, might be closer to 500HP and 500TQ; these two

numbers are added together produce a score of 1,000.

 

1. HEADS, CAM, COMPRESSION - Cylinder heads, camshaft,

and compression, will always be the largest

determinants for the final power output of any given

engine. More than 95% of an engine's power is derived

by the "big three"; this was true in the past, and it

will hold true in the future.

 

2. HEADS - Heads are everything. If you need more

power, then you need more air-fuel mixture flowing

through the system. When making a bigger explosion,

larger quantities of air and fuel must pass through

the system. I personally feel that port volume is

over-rated and flow is under-rated. Porting must be

consistent and efficient, but generally speaking, more

flow means more power. Here is a quote from John

Kaase, the 2003 and 2004 engine master champion:

 

"Chris Howe, labored two days on porting and valve

seat work. We started the testing with full-size

intake ports and later shrunk them down, which made

very little difference at any rpm." - Jon Kaase

 

This is a good example where port volume had

negligible effects on flow and power. Kaase's heads

outflow the competition, especially at mid-lift. If

you have the skills to pull it off, one of the ways to

improve flow is to shrink the combustion chamber. This

reduces the quench distance and places more of the

chamber in the top of the piston. This makes for a

very efficient chamber and is referred to by my Phd

friends as a "Heron" chamber. This will not help peak

flow but does help mid-lift flow numbers since the

valves are un-shrouded sooner.

 

3. CAM - The camshaft determines the shape and size of

the horsepower and torque curves. Camshafts are chosen

to optimize horsepower and torque for a given rpm

range. Drag racing, roundy-round, and road racing, all

require power in different areas. Computer simulation

software is very good at finding a starting point for

picking the cam that will best match your specific

power needs.

 

* Duration

* Lobe Shape (Lifter Acceleration Rate)

* Lift

 

The computer is good at finding the correct duration.

Lift is often limited by rules. The lobe shape should

be as aggressive as possible, with practical engine

life in mind. The lobe shape is probably the part of

the cam design that is least understood by the public.

The faster you can open and close the valve, the more

efficient the system, and the more power you will

make. You can design a camshaft with a 280/288

duration and 106 centerline many different ways, based

on the many different lobe shapes. Use the computer,

talk to the cam reps, and do some testing.

 

Belt drives are worth the investment because you can

test various intake centerlines; wiggling the cam

finds power.

 

4. COMPRESSION - More compression makes more power,

assuming you can control detonation. Compression is

often limited by rules. In the Engine Masters,

contestants are limited by 92 octane pump gas. The

most popular compression in the winner's circle is

12.5:1. This ratio is too high for a street car, but

it has a place in race engines on the edge. Many

builders are scared of compression, it's worthwhile to

test and find the engine limits using a research mule.

 

5. MANIFOLD - If heads, cam, and compression are the

"big three", the intake manifold makes the "big four".

The manifold is an extension of the cylinder head.

Most of the top engine masters test and re-test to

find the manifold that best works for their mill.. I

don't have statistical proof, but I believe a manifold

should flow the same or 5% better than heads at peak.

If you have heads that flow 350, I would start testing

with a manifold flowing in the 350cfm to 365cfm range.

If your manifold flows less than your heads, air flow

becomes restricted and total power will be reduced. If

your manifold flows way more than your heads, the air

gets lazy, loses some velocity, and power declines.

 

6. CARBURETOR - It surprised me and all the lads at

Westech Dyno, when we put an 830cfm on my engine and

did a baseline pull, then sleeved it up to 1050cfm,

made one jet change and repeated the pulls, and the

total average power was identical. Don't get too

hung-up on the carburetor. Pay the money ($700 -

$1,500) for a good race carburetor, tune it, and don't

worry about it; retune it when conditions dictate.

 

7. HEADERS - I took seven sets of headers to the dyno;

I was certain that one pair would have the magic.

 

* Hooker (2 sets)

* Heddman

* Mac Performance

* Basanni

* Kooks (2 sets)

 

Once again, me and the lads at Westech Dyno were

shocked that all of headers produced average scores

within 5 points of each other. The headers had

different peak horsepower and torque, but when you

examine averages, the truth is revealed.

 

Most racers and engine builders want headers with

primary and collector tube size diameters that are

simply too large. My rule of thumb is to choose a

header with a primary tube size, ten percent larger

than the exhaust valve. Start in this range and test.

In the 2004 engine master competition, most heads had

1.6" exhaust valves, and most competitors were running

with 1.75" headers.

 

One of the more interesting tests we did while

preparing at the dyno, was to run a set of 1.75"

Kook's with a 3" collector VS. a 1.75" to 1.875"

stepped Kook's with a merged collector. The difference

in scores between the two headers was 1-2 points at

best; that is 2 points out of 1,000. I've never been

convinced that stepped headers or merged collectors

make more power, and this test reinforced my beliefs.

The two headers did have differing peak numbers, but

peak is the false god...average is the true strength

of the engine. Stepped headers and merged collectors

are expensive. If merged collectors work, why do they

work? It's my belief that they work by simply reducing

the size of the collector (people choose collector

diameters that are too large).

 

I wanted to test my size reduction theory; on the

fourth day of pulls, with a standard set of 1.75"

Hookers with a 3" collector, I mounted a pair of 2.5"

collector reducers, inside the collector pipe. These

reducers cost $25. We ran the test and picked up 2-3

average points. You can spend $500 on a pair of merged

collectors, or you might try testing a cheap pair of

collector reducers, fit inside your exhaust pipe. I

think you will be pleased with the results.

 

8. BIG BORE SMALL STOKE VS.. SMALL BORE BIG STROKE -

On paper, a big bore with a small stroke makes more

power than a small bore with a big stroke. I'm not

clear on all the reasons, but I do know that heads

flow more efficiently over a bigger bore. When you add

detonation to the story, suddenly the small bore big

stroke gains the advantage. Kaase was one of the first

to use this in competition.

 

"Because of the low test rpm range, I felt I needed

the longest stroke and smallest bore with which the

heads would work. With pump gas, detonation was a huge

factor in the design of the short-block and heads. A

smaller bore has less chance of detonation because it

doesn't have some far-off place for a secondary flame

front to start." - Jon Kaase

 

9. OIL - As much as I don't want to believe it, there

is hidden power in motor oil. When going from SAE

20w-50, to synthetic 30, and then to synthetic 20, 2-5

average points in power were found. Thin oil makes

more power than thick; synthetic oil makes more power

than regular. The gains aren't huge but they do exist

and they are clearly seen on the dyno runs.

 

A good oil pan allows oil to drain properly; a bad pan

can cost power at certain rpm levels. Too much oil

will effect power adversely and most people run with

too much oil. Don Terrill suggests testing an 8qt pan

with 5qts of oil and I have to agree. On the dyno, my

engine master's engine was happiest with 5.5-6qts.

 

"With a properly located oil pump pickup most engines

don't need more than 5qts of oil. Want to see how

critical oil level is to power? Test it: If you have

an 8qt pan, run it with both 5 and 8."...Don Terrill

 

Too much oil pressure reduces power. It takes more

energy to turn the reciprocating assembly as it slings

off excess amounts of oil. Too much pressure can

prematurely wear the cam and distributor gears. If you

have an engine that won't hold timing, pull the

distributor and look at the gear. If the gear is worn,

the cause may be excessive oil pressure or an

improperly clearances distributor gear and shaft. A

good rule of thumb is Terrill's 10lbs of pressure for

every 100hp.

 

10. TESTING - The best way to find the truth is

testing. Engines are tested on dynamometers. Book the

dyno for longer than you think; one day is barely

enough time to break-in an engine and set the carb.

Check the oil and water temperature every run and be

consistent. Make good notes for every run. Only test

one thing at a time. Use average horsepower and torque

for your running range as the yardstick to compare

changes. Average horsepower and torque are easy to

find with SuperFlow software, just click File >

Average > Columns and then select the RPM range you

want to analyze.

[keyman]

Thats some good stuff to know, thanks Cassie