Does my car not make the advertised HP?
06-28-2005, 03:04 PM
#2
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Originally Posted by dmp
My car's missing HP...3000lbs cars with 238hp don't trap at 90mph. 
http://www.dsm.org/tools/calchp.htm
ive tried several others and they all indicate about 170 at the wheels.
06-28-2005, 03:09 PM
#3
Humpin legs and takin nam
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I don't think there's any doubt we're only getting 170 - 180ish to the wheels??? With a very few getting 200, i'd like to see thier times. Gearing most likely has alot to do with it, since we essentially have only 5 power gears, right?
06-28-2005, 03:13 PM
#4
RX8 and a Truk....
Thread Starter
Originally Posted by zoom44
http://www.ajdesigner.com/phphorsepo...horsepower.php
ive tried several others and they all indicate about 170 at the wheels.
ive tried several others and they all indicate about 170 at the wheels.
My car dyno'd at 186whp....and my best trap was ~91 mph...I weigh 220lbs in clothes...so figure 3300lbs.
figures about right:
weight = 3300 pound = 3300 pound
velocity = 90 mile/hour = 90 mile/hour
--------------------------------------------------------------------------------
Solution:
horsepower (hp) = 187.7560309513 horsepower
or:
weight = 3300 pound = 3300 pound
velocity = 91 mile/hour = 91 mile/hour
--------------------------------------------------------------------------------
Solution:
horsepower (hp) = 194.08436213992 horsepower
06-28-2005, 04:09 PM
#7
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Originally Posted by dmp
15.0 with a 2.5 60ft
second one?
second one?
194whp * 1.20(for 20% drivetrain loss)= 232.8bhp which is just 3% off the advertised 238bhp. whats the isue?
06-28-2005, 04:12 PM
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Originally Posted by zoom44
i edited my post the hp calcs indicate you are putting 194 whp on the strip or about 8 more than on the dyno.
194whp * 1.20= 232.8bhp which is just 3% off the advertised 238bhp. whats the isue?
194whp * 1.20= 232.8bhp which is just 3% off the advertised 238bhp. whats the isue?
06-28-2005, 04:16 PM
#9
Administrator
that would be the dyno not being consistent.
he said his car cant be putting out advertise dhp based on the reult of his 1/4 mile run - specifically trap speed. however if you actually usea a trap speed to hp calc you get teh numbers about which shows his original remark was incorrect.
he said his car cant be putting out advertise dhp based on the reult of his 1/4 mile run - specifically trap speed. however if you actually usea a trap speed to hp calc you get teh numbers about which shows his original remark was incorrect.
06-28-2005, 04:17 PM
#10
RX8 and a Truk....
Thread Starter
Originally Posted by 124Spider
Oh, heck, I can answer that for dmp. :D At the same place and morning as he dyno'd his car at 186hp (uncorrected), mine did 219 (uncorrected; 210 corrected), and my car is rated at 240hp. Something's not quite consistent there.
The issue is "online calculators are crap" when it comes to the real world.
186hp or even 190hp is still too low, and your 'drive train loss' percentage is too high.
With Miatas using similar (the same?) transmission, but a non-CF driveline, and sending the power to a similar rear-end, they are losing about 26hp...
I simply cannot buy an RX8's drivetrain consumes TWICE that power.
As an aside- the link I went to was estimating ENGINE HP
This method uses the speed or velocity at the end of a quarter mile run. It is used to give an estimate of vehicle(car, truck, motorcycle) engine horsepower. Weight should include the mass of the vehicle, driver and passenger.
06-28-2005, 04:22 PM
#11
RX8 and a Truk....
Thread Starter
Originally Posted by zoom44
that would be the dyno not being consistent.
he said his car cant be putting out advertise dhp based on the reult of his 1/4 mile run - specifically trap speed. however if you actually usea a trap speed to hp calc you get teh numbers about which shows his original remark was incorrect.
he said his car cant be putting out advertise dhp based on the reult of his 1/4 mile run - specifically trap speed. however if you actually usea a trap speed to hp calc you get teh numbers about which shows his original remark was incorrect.
Please don't make the mistake of quoting these numbers as if they meant anything
For a comparison, I entered the data from my old Probe GT - I went 13.8 at 107 mph...shows:
Using the Speed method, I come up with 296 "on-the-pavement horsepower"
But for my Miata, which went 16.5@81mph, it shows:
Using the Speed method, I come up with 104 horsepower.
Talk about inconsistancies...
:D
06-28-2005, 04:24 PM
#12
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Warning: Thread hijack in progress....
No, actually the dyno was very consistent. All the RX-8s but one were within a couple of hp of each other.
Does anyone really think that the RX-8 puts out 238hp at the crank, stock?
Originally Posted by zoom44
that would be the dyno not being consistent.
Originally Posted by zoom44
he said his car cant be putting out advertise dhp based on the reult of his 1/4 mile run - specifically trap speed. however if you actually usea a trap speed to hp calc you get teh numbers about which shows his original remark was incorrect.
06-28-2005, 04:27 PM
#13
Administrator
yes but the wording is wrong- why else would the other calc(s)s say at the wheel. "There are two simple horsepower formulas that can estimate the on-the-pavement horsepower for a given car". it cant calculate bhp without knowing the gearing.
second 20% drive train loss is what we have.
check these - all are calulating rear wheel hp and get the same numbers as the first
http://www.amaprostar.com/dynos.asp
http://www.ultimateresourceguides.co...nt/index4.html
http://www.smokemup.com/auto_math/trapspeed_lbs_hp.php
try this one and read it carefully- gives 2 answers 1 whp and 1 bhp by adjusting with 25% drivetrain loss
http://www.gordon-glasgow.org/hpcalc.html
second 20% drive train loss is what we have.
check these - all are calulating rear wheel hp and get the same numbers as the first
http://www.amaprostar.com/dynos.asp
http://www.ultimateresourceguides.co...nt/index4.html
http://www.smokemup.com/auto_math/trapspeed_lbs_hp.php
try this one and read it carefully- gives 2 answers 1 whp and 1 bhp by adjusting with 25% drivetrain loss
http://www.gordon-glasgow.org/hpcalc.html
06-28-2005, 04:33 PM
#15
RX8 and a Truk....
Thread Starter
Originally Posted by zoom44
yes but the wording is wrong- why else would the other calc(s)s say at the wheel. "There are two simple horsepower formulas that can estimate the on-the-pavement horsepower for a given car". it cant calculate bhp without knowing the gearing.
second 20% drive train loss is what we have.
check these - all are calulating rear wheel hp and get the same numbers as the first
http://www.amaprostar.com/dynos.asp
http://www.ultimateresourceguides.co...nt/index4.html
http://www.smokemup.com/auto_math/trapspeed_lbs_hp.php
try this one and read it carefully- gives 2 answers 1 whp and 1 bhp by adjusting with 25% drivetrain loss
http://www.gordon-glasgow.org/hpcalc.html
second 20% drive train loss is what we have.
check these - all are calulating rear wheel hp and get the same numbers as the first
http://www.amaprostar.com/dynos.asp
http://www.ultimateresourceguides.co...nt/index4.html
http://www.smokemup.com/auto_math/trapspeed_lbs_hp.php
try this one and read it carefully- gives 2 answers 1 whp and 1 bhp by adjusting with 25% drivetrain loss
http://www.gordon-glasgow.org/hpcalc.html
There's no way the car loses 20% if a Miata loses 15% +/-...it's hard to use a percent, because it's not really a percentage...it's generally a fixed number AND some percent...
still...same engine as a miata, better drive shaft than a miata, similar rear-end as a miata does not mean that much greater loss.