Ruiz Racing Posted April 25, 2009 Share Posted April 25, 2009 When I had my car dynoed at Mac Mann Motor Sports of Parker Colo. They est. that there was 20% power loss through the drive train. I know there are many variables, but do you think this a good middle ground? Quote Link to comment Share on other sites More sharing options...
at-jefft Posted April 26, 2009 Share Posted April 26, 2009 I have heard 15%. If it were me I would only worry about wheel hp. afterall thats what matters right? (unless your selling the engine haha) Quote Link to comment Share on other sites More sharing options...
cockerstar Posted April 26, 2009 Share Posted April 26, 2009 What kind of dyno was it run on? Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 26, 2009 Share Posted April 26, 2009 All of it is a crapshoot, but you need to have a stock vehicle dynoed that the MFR gives realistic numbers for. This has to be a the same type of dyno that you are using WHP numbers to convert from. At that point, you have a drivetrain loss for your car from that dyno, etc. etc. Honestly, pie-in-the-sky crank HP numbers are just that; pie in the sky. Even so, drivetrains don't take a fixed percentage of your power. Each type of drivetrain has different losses; manuals less than autos (typically). AWD more than 2WD (typically). Transverse trannies more than longitudinal (typically). Quote Link to comment Share on other sites More sharing options...
woldson Posted April 26, 2009 Share Posted April 26, 2009 Just add more untill you like the number you come up with;)!!!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
johnc Posted April 26, 2009 Share Posted April 26, 2009 how do you calculate flywheel hp? All the procedures are right here: https://shop.sae.org/technical/standards/J2723_200708 Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted April 26, 2009 Share Posted April 26, 2009 Ruiz.. there are A LOT of different factors.. Figures release from automotive companies is called BHP (brake horse power) this is a figure based on the SAE standards.. that tests the engine in optimum temperatures, in perfect conditions, with a bare naked engine... I mean no power steering, no flywheel, no fan, no power accessories running.. nothing.. its literally crank horsepower in perfect conditions. A good universal figure is 20%. I've always been skeptical since every car is different.. no 2 machines are identical. On top of that FWD will have less drivetrain loss because the transmission and differential are all in one, with no super long driveshaft to lose power in. RWD figures are next on the list.. with more drivetrain loss then FWD, but less then AWD... AWD cars have to transfer the power to the front transaxle, then a driveshaft, then another differential.. the same car with 18" wheels will put out less HP and Torque then the same car with 13" wheels and small tires on a rolling dyno. EVERYTHING makes a difference... everything. Also here in colorado at nearly 6,000 ft above sea level.. the performance of a car is terribly sacrificed. during my studies of aviation in college we learned a general rule of thumb to cut nearly 15% of the available power at 8,000 ft above sea level. thats 15% freakin percent, in addition to the general 20% powertrain loss. Thats a 35% loss at this altitude... so that advertised 270bhp nissan 350z actually puts out 175.5 wheel horsepower in PERFECT conditions. the pressure in the atmosphere, the air temperature.. air density.. dew point.. everything makes a difference.. some days in the summer we have a density altitude of nearly 9,500 ft in July.. which means im physically standing at an altitude of 5,200 ft but the air density on a hot day is similar to 9,500 ft because the air is so thin. now increase that figure to nearly 40-45% power loss. Catch my drift? Quote Link to comment Share on other sites More sharing options...
blackwidow Posted April 27, 2009 Share Posted April 27, 2009 Each type of drivetrain has different losses; Transverse trannies more than longitudinal (typically). You sure, and can you explain why for me? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 27, 2009 Share Posted April 27, 2009 All the procedures are right here: https://shop.sae.org/technical/standards/J2723_200708 Johnc for the win... Quote Link to comment Share on other sites More sharing options...
Ruiz Racing Posted April 28, 2009 Author Share Posted April 28, 2009 i was just asking becuse the first time i put my car on the dyno i got 180whp 210tq. so i told some guy on myspace i made 215. it was being compared to the stock 180hp claimed by nissan. but i did this with 4psi. i had a cracked hose on the turbo. more over there was a bend in one of my intake porpeller blades. i think a rock got in there or something. it came with the car. i could not tell if it was the boost gauge or the turbo before i put on the boost controller and a new boost gauge. i had a n-42 intake, 3 inch stait pipe, cold air intake, walbro 255 pump, no belts. only altenator, 91 octane. everthing eles was stock at the time. he said this was completly impossible. it made him so mad that he deleted me from myspace? i don't know what a stock 280zxt with 200,000 mile puts down to the wheels a mile high. so i compared it to the factory claim. is claiming 215hp way too much? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 28, 2009 Share Posted April 28, 2009 You should claim 180rwhp and nothing else. Quote Link to comment Share on other sites More sharing options...
Ruiz Racing Posted April 28, 2009 Author Share Posted April 28, 2009 You should claim 180rwhp and nothing else. the whole point was that it was being compaired to the stock power. a stock car does not put 180 hp to the wheel. i was try to compair apple with apples. to say my car made as much power as a stock dose not make sense to me. Quote Link to comment Share on other sites More sharing options...
RIPSNZ Posted April 28, 2009 Share Posted April 28, 2009 We've had stock 208bhp auto rwd cars make around 160whp on the dyno we use, and depending on the car up to 30% power train losses can be quite normal. whp is what gets you down the road not bhp so don't be too worried about it. Rob Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 28, 2009 Share Posted April 28, 2009 My point is I've seen such a huge range of dyno results between rwhp and the advertised hp of vehicles, that it's absolutely silly to try to make that statement. Somewhere between 8 and 40% difference, depending on the car, and the original hp claim. That's such a huge range that it makes any back conversion akin to a random guess... Quote Link to comment Share on other sites More sharing options...
Ruiz Racing Posted April 28, 2009 Author Share Posted April 28, 2009 My point is I've seen such a huge range of dyno results between rwhp and the advertised hp of vehicles, that it's absolutely silly to try to make that statement. Somewhere between 8 and 40% difference, depending on the car, and the original hp claim. That's such a huge range that it makes any back conversion akin to a random guess... That is a good point also. All I was trying to say to him was that my car made more hp than a stock 280zxt with 4 psi. Which he stated was completly impossible. The whole discussion was about making more power in other ways. Besides just turning up the boost controller. He also stated that even with a modified engine. There is no way a l28 could ever, in any posible way, make 300hp, or even 300rwhp with only 10 psi. So a better question, am I crazy of saying that it is possible? Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted April 28, 2009 Share Posted April 28, 2009 unless you can put an engine on an engine dyno, and the exact same engine on a wheel dyno once installed, drive train losses is a wild ass guess. Quote Link to comment Share on other sites More sharing options...
Sideways Posted April 28, 2009 Share Posted April 28, 2009 Ruiz.. Also here in colorado at nearly 6,000 ft above sea level.. the performance of a car is terribly sacrificed. during my studies of aviation in college we learned a general rule of thumb to cut nearly 15% of the available power at 8,000 ft above sea level. thats 15% freakin percent, in addition to the general 20% powertrain loss. Thats a 35% loss at this altitude... so that advertised 270bhp nissan 350z actually puts out 175.5 wheel horsepower in PERFECT conditions. And wheres the 270 from? I thought even the oldest ones had 290.. Catch my drift? Wouldnt you deduct 15% from 270 FIRST, then reduce it by 20%? The outcome is a bit different than just adding up the %s and reducing it. Quote Link to comment Share on other sites More sharing options...
Nizm0Zed Posted April 28, 2009 Share Posted April 28, 2009 the other thing that doesnt seem to be mentioned, is that the dyno operator can fudge the calibration, like changing the wheel size, to 'adjust' the power figure displayed. i have heard of dyno operators doing it down here, after the customer has spent several grand on engine work, so they feel better with the amount they have spent. a friend of mine wont mention power levels, he simply says it'll do the quarter in 11.5sec and his local race track in 1:23 on street trim. (numbers out of my ass, because i cant remember how quick his car is) Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 28, 2009 Share Posted April 28, 2009 Dyno power numbers should really only be used as a reference against themselves on the same dyno for that exact reason. It's a piece of cake to make the numbers say what you want it to say. A dyno operator with integrity will at least keep his numbers consistent for each run on his machine, allowing you to compare every pull on that machine with a reasonable degree of accuracy. Quote Link to comment Share on other sites More sharing options...
burninator Posted April 28, 2009 Share Posted April 28, 2009 I work for a company that makes dynos, so let me chime in my 2 cents. I'm not a spokesman for the company so I'm not even going to say which company I work for. Comparing dyno numbers to any car other than your own is pointless. The only purpose a dyno has is for tuning and comparing your car before and after a modification on the same dyno. As others have said, trying to compare bhp to the horsepower your car makes is impractical in any situation. I know of many ways a dyno operator can affect the results (intentionally or not). So pick a dyno operator/owner you can trust. I'm just saying there are many things that affect the numbers you get. Especially on load cell based dynos, inertia type dynos are better from a repeatability standpoint. My point is that you shouldn't worry so much what some guy on MySpace thinks of your power numbers and you shouldn't try to fudge the numbers by some % that you heard about. Just tell people that you make 180 whp or wheel horse power and explain to them that manufacturers rate their engines at the crank. I think up until pretty recently manufacturers were getting in trouble for rating their cars as more powerful than they really were. Its better to try and educate them about how dynos work than to try and fudge your numbers. Quote Link to comment Share on other sites More sharing options...
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