More HP: a Quick Q&A!
(by Phil - our Cavalier World "Tech" guy)
(For Fuel Flow & Formula's
I get a lot of calls each day
asking the same question "How do I make more power (HP)?".
The answer may not always be exactly the same, and different engines are
affected by different factors, but here I'll explore some of the most
common answers and solutions. Some are pure physics and others are
applicable to specific motors.
IPP (and myself included), has worked for years in the
development of sport compact motors, with a strong focus on the 2.2
Chevy Cavalier both with street drivers, street/strip and all out
racing. So let's start by addressing N/A (Nat Aspirated) motors
First of all, always remember that when you buy a car from a
dealership, the MFG does not want to see you in their service bay -
especially while the car is still under warranty. What they are
concerned about before your purchase are things such as gas mileage,
longevity (time until the warranty runs out), federal emissions and if
the car looks hot enough for you to buy. That being said, the MFG's
always try to under design motors to just meet that initial
warranty period, hence the stock motor the car comes with. So you will
eventually need to upgrade from stock if you want to get anything extra
HP-wise out of the engine.
Let's start with the basics on HP:
There is NO Replacement for Displacement. In most cases this is true and
a proven fact.
Let's take a look at the Chevy 327 - that motor started with a 4"
bore, 3.250 stroke and then went to a 3.484 stroke (350), AND after that
a 3.75 stroke (383). Now you have 3.875 + 4.00 strokes!
The bottom Line? The more cubes the more HP (along with another
variables which may be needed to larger cubic engines).
So how about the Mitsubishi 4G63? One of the big time players in the
Import market. Take a bore of 85mm then stroke to 94mm, add a 4G64 crank
at 100mm and now you have a beast of a motor in a N/A or Turbo form!
Let's go over some of the more common calls I get on adding HP to N/A
QUESTION: "Do I have to bore the motor? Does that cost
ANSWER: Yes! And that is simply because you can't get more HP
without moving more air (and yes, boring is not for free usually!).
There are essentially two ways to increase cubic displacement:
2) Stroking the Crank.
(And while we're at it, let's also mention that compression increases HP
QUESTION: Customers call and asks "Do I want to
increase my compression? I've got 9-1, 9-5-1 (by the way the rule of
thumb on pump gas is 9.5-1 with steel heads and 10.5- with aluminum
ANSWER: YES! Do overbore to get more cubic inches
and raise the compression. Both are the most common ways to increase
And here's another common call (and it's a good one!)...
QUESTION: How can I get a LOT more HP and use LESS gas?"
ANSWER: Good question! And when you figure that one out please
call me ASAP and we can both become billionaires! Ha!
The Lighter the Assembly, the more HP you make!
Think about pushing a VW versus a Caddy up a hill - which is gonna be
easier? So the same physics goes for motors too. Always keep in mind
that bob-weight (Piston, pins, clips, rings and rods) are extremely
important to look at for more HP, and longer wear & longevity in
general. (Note: the furthest away from the center of the crank is the
most important in weight)
Let's tackle this in order:
- First are the pistons - on N/A motors you may be surprised at how
light you can run them!
- Second are the Pins - In today's technologies companies can make
stronger and lighter pins, and in most cases in smaller diameters
(factories like gentle, heavier parts and even limit the RPM ranges to
keep that warranty)
- Third are the Rods - Almost ALL MFG's of aftermarket parts have
learned that the Lighter the rod (within limits), the lighter the total
So what does this all mean? It means lighten your load!
Swap out for lighter Pistons, pins and
Rods and you're on your way to
more HP. In addition to the extra HP you'll gain, the lighter load means
less ware and tear on the cylinder walls and bearings. Think pushing
that VW versus Caddy up a hill and it all makes sense!
So let's review the Steps! To get more HP quickly, you can do
Now you have a great foundation for building a kickin' motor with
increased HP - Exactly what you want!
Next QUESTION: Should I add a cam?
ANSWER: Well... That depends on a few things! First, do you have
a small bore, low compression motor? If so, then a Cam ain't gonna help
you very much - go on back to Step 1 and start from there, then we can
talk about a cam!
QUESTION: Should I add a header and Cold Air Intakes?
ANSWER: You could, but 2.2 Cav's don't have a great exhaust port
to begin with, so there's not much point in that add-on. I personally
LOVE Cold Air Intakes, but only if what I am trying to feed is above
stock motor. Also, if a Cold Air Intake is fed from outside you can
expect that for every 11 degrees of colder air than under hood, then you
are looking at approx 1 percent of HP gain.
EXAMPLE: Your under hood = 165 degrees. It's 80 degrees outside.
You have 100 ponies to start with, so you can expect to see 107.7 HP.
Also remember that the Cold Air Intake serves 2 purposes; One is to
lower the Air Intake temp and the other is to increase Air Flow. (Note
that increasing air flow to a bone stock motor is as much a waste as
adding headers. So put your hard earned money where you can get the most
HP for what you pay for!)
QUESTION: Will porting my heads help me out?
ANSWER: Another zinger! If you can move more air into that pump
you can definitely get more out - but NOT on a stock motor (if
that's you, then go on
back to step 1, then move onto porting
QUESTION: What about bigger valves? That's gotta help
ANSWER: Yup, but NOT on a stock motor (sending you back to step
QUESTION: Can I get more HP by Stroking the motor?
ANSWER: You bet ya! Remember, cubes count! So how can you stroke
a motor that has been already stroked (like a 2.0 Cav to a 2.2 and
larger). That's a definite YES! And that's exactly what happened to
Chevy SB and BB motors as well as Mitsubishi 4G63, Honda B18 and a ton
QUESTION: But will my rod ratio be bad if you do this?
ANSWER: Possibly. You may need a longer rod and a shorter piston.
And rod ratio lessens into the figure with lighter bob-weights
(the VW versus Caddy example again!)
So I hope I have answered some of the more basic and most asked
questions . I will follow up with more info as I collect it and get it
onto paper (and my pc!). I plan on talking
injectors, superchargers, and Turbo's in my next Q & A!