Re: HP/Cubic Inch

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Re: HP/Cubic Inch

Postby kfxnando » Mon Apr 12, 2010 4:45 pm

well here is a very interesting concept, that I believe is a good indication on what to expect out of a motor while holding reliability!!

out of books and discussion with friend, the general agreement is that 1Hp/cubic inch

yes know very well we no longer work in horsepower or cubic inch for most of the world!!

however its a good way of working out what to expect from your motor!! and with a few simple calculations one can work things out quiet easily!!
take note this is not the limit however a good rule of thumb for a street motor, that will last and be reliable

well will start off with what I have and what I can expect and what I am expecting!!

sure by now every one knows that I am sitting with a 3.4L Ford V6

so will work out numbers on that one

3400ccc (actually a little less) = 207,.. cubic inches

so one can expect 207 hp
note that, that this will be flywheel power at sea level!!

yes can build the motor to compensate for the loss of altitude, and seeing that we spend most of our time at high altitude, there should be no issues!!
further 1hp/cubic inch is a street motor and much more can be gained out of it in different states of tune!!

any case back on topic will then translate to about 102.7kw at the wheels at seal level, the loss comes from a typical rear wheel drive system gearbox and diff!! its a loss of 1/3, that is typical for a rear wheel drive setup
then we need to add to that the loss for the altitude that we are at, and according to various books/experts we loose between 15-18% once most of us are home!! they talk about 3% for every 1000ft above sea level
we are around 6000ft witch is 18% with some minor variations!!

102.7kw minus loss for altitude of 18% = 84.214kw

translate that to hp (the only dyno operator that I trust, his dyno reads in hp @ the wheels) no compensations and other BS!!

112.9328hp, that will be from a 3.4L producing 1hp/cubic inch

can already hear all the comments, this is rwhp, nothing else!!
have a 1000cc super bike and a certificate that reads 155hp, great to brag and chat over round the camp fire, however I know its not accurate!!

lets do a double check on the numbers!!

stock Ford V6 3L in a Sierra (183.0712 cubic inches)
rwhp 76-78 at our altitude

convert to sea level
92.7-95.12 rwhp

back to the flywheel
139.05-142.68 hp at the motor

convert back to kw as that is the system that we use locally
103.6896 - 106.3965

go have a look at what the specs for those cars were, depending on model that is almost spot on!!

my target for the 3.4 after the rebuild 125-135rwhp
believe easily obtainable!!

yesterday we got some more great info on the Ford V6 (essex)
including on that same dyno 212rwhp from a 3.0l V6 normally aspirated

previously on the same dyno, had 108rwhp from a 3l V6 in a Ford Sierra with a single carb and a very mild cam!!
increase the cc by 13.33% with at least the same efficiency 122.364rwhp is a realistic/simple possibility
with a better cam and a slightly higher compression ratio 10-10.5:1
target should be with in reach for a strong towing motor(target 125-135rwhp), take note this will not be a dragster, however rather a workhorse tow vehicle 4X4, with reliability and years of towing in mind!!

hope this is informative and makes sense for someone more then just me!!
feel free to comment witch ever way!!
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Re: HP/Cubic Inch

Postby kfxnando » Mon Apr 12, 2010 4:47 pm

now, pls allow me to elaborate!!

poor old V6, keep being used for every thing including these examples!! the same could be applied to any other engine!!

stock Ford Essex 3.4L V6 108kw (disgusting and disgraceful I know)!!

minus 1/3 for drive terrain loss

minus 18% for altitude loss

convert to hp (reason - couz the dyno that I use measures in rwhp)
=79.17394 rwhp
heavily restricted as per compliments Ford SA

target 125-135rwhp BIG increase I know!!
back to seal level
= 152.44 - 164.63rwhp at seal level
back to flywheel
=228.66 - 246.945 hp @ flywheel/crank!! 207 Cubicinch, 1.104 - 1.193/ cubic inch (rounded off 1.1 - 1.2)
back to kw for every one to understand
=170.5117 - 184.1469kw

that is very comparable to the 4.0 V6s of other makes on the market
and better then the 3.5s V6 also of other makes
at a fraction of the cost!!

just wish I knew what to expect with respect to torque and at what revs!!
however am expecting/hopeing 350Nm+
and that should be enough to satisfy my need for towing torque and power!!
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Re: HP/Cubic Inch

Postby kfxnando » Mon Apr 12, 2010 4:48 pm

ok, before the Nissan/dustbins :lol: have been offended by only using the Fords for all the examples, will do a Nissan one, and to top it all the TV adds now claim the most powerful in their class!!

Nissan Navara 4.0i V6

4000cc = 244 Cubic Inch
so the target should be 244hp

however listed as 198kw = 265.5

comes to 1.088 hp/ci

now lets have some more fun and work it back to the wheels at altitude as well!!

at the wheels @ seal level
132kw / 177hp

at the wheels @ 6000ft altitude
108.24Kw / 145.14hp

anything else is being inflated if the vehicle is in stock form
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