BHP explained
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Just lifted this off another forum. I found it mildly amusing no doubt its a repost
Lesson 1: BHP Explained
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Right, we've all noticed a lot of magazines and stuff quoting BHP figrues
against cars and I thought I should take the time to explain what these are.
Basically the figure they are quoting is the most important factor about the
performance of a "phat/wicked ride".
Brake horsepower and Torque are all very well, but the main figure that counts
is Bar Horse Power, this is the figure that you tell your mates down the pub.
To calculate this use the following rules:
STARTING POINT
The manufacturers generally handpick an engine that they know is on the right
end of tolerances for testing, this means that often its a higher figure than
an average new engine actaully makes, ignore this fact and swear blind that
your smoking nasty example of a now half f***ed engine makes the figure
claimed, round up whenever possible, so 152bhp = 160bhp etc
BOLT ON MODS
Obviously the correct way to get more power from your smoking engine with poor
valve seal and rings that are about as tight as Freddy Mercury's arse, the way
to get more power is to ignore those facts (see "starting point") and just bolt
tat onto the outside of it.
These mods can include filters/exhaust/dumpvalve etc, or even semi-internal mods
like cams, we wont cover things like bearings or rings cause those arent very
shiney so you wont want to replace them.
The manufacturers always state the gains that you will get from a mod, often
your car wont be listed specifically with a power gain, so just pick the
biggest one that is, if a skyline can pick up 22bhp from an exhaust, then so
can your saxo, again dont forget the golden "always round up" rule.
The figures should all be added up, and round up again.
ITS A GOOD'UN
You need to add a proportional value based on the "its a good'un" factor of your
engine, basically, as this is YOUR engine not anyone elses, its special, so the
mods will all make more difference, so multiply the number up a bit to take
this into account.
STICKERS / SPOILERS
Race cars have them, so you need them too, the key thing here is to not buy ones
that apply to anything you have fitted, go for stuff that isnt even made for
your car, so Greddy/HKS/Blitz is ideal for an XR2i.
Now the thing to remember with modifications to a vehicle is that they work in
harmony, it all comes together as a package, exhaust will compliment head mods,
filter will work well with a decat or whatever, now stickers are about attitude,
and attitude is what counts out there on the street (or halfords car park).
Take the % of your car covered by stickers and spoilers and add that onto your
BHP figure as an attitude adjustment (dont forget to round up!!)
WORKED EXAMPLE:
Fiesta XR2
quoted figure (use a guess if you cant find the manufacturers), 94bhp
filter (using the figure for a porche 911) - 11bhp
Exhaust (using figure for a skyline) - 22bhp
decat (never had one so you get this without doin anything, PHAT!) - 12bhp
sticker coverage = 47%
spoiler coverage = 12%
Its a good'un factor = 25%
We'll do the rounding first:
So the calcs are:
94 round up = 100
filter round up = 20
exahust round up = 30
decat round up = 20
sticker round up = 50%
spoiler round up = 20%
good'un round up = 30%
So 100 + 20 + 30 + 20 = 170
plus stickers 50% = 255
add spoiler factor 20% = 306
add good'un factor = 397.8
Final round up = 400bhp
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This however is only your basic Bar Horse Power figure, make sure when you quote
it you increase it inversely to the age of the girl you have with you at the
time, and in direct proportion to the number of pints you have consumed.
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