turbogrill Posted September 21, 2017 Report Share Posted September 21, 2017 Hi, How can the gross power be some much higher than the net horsepower? The difference between the Datsun L28 engine is huge: 280zx (net) : 135hp 280z (gross): 170hp How on earth did they manage to squeeze out 35 more horsepower ? It's very hard to get more than 10+ HP on these engines without change a cam. Feed it with nitro during testing? It doesn't have that many emission stuff and besides weight there is a very minor performance degradation. The only think I can think of is running without alternator, AC and fan. But that shouldn't be to much. Quote Link to comment Share on other sites More sharing options...
Team Infiniti Posted September 21, 2017 Report Share Posted September 21, 2017 You'd be surprised how many horsepower takes to run the accessories including Fan 1 Quote Link to comment Share on other sites More sharing options...
karman1970 Posted September 21, 2017 Report Share Posted September 21, 2017 Yeah, watch the engine masters episode on fan testing. Very eye-opening. 1 Quote Link to comment Share on other sites More sharing options...
turbogrill Posted September 21, 2017 Author Report Share Posted September 21, 2017 But the fan is only running if it's needed right?....in go stop traffic not WOT. Same with the AC and alternator? Quote Link to comment Share on other sites More sharing options...
Team Infiniti Posted September 21, 2017 Report Share Posted September 21, 2017 2 minutes ago, turbogrill said: But the fan is only running if it's needed right?....in go stop traffic not WOT. Same with the AC and alternator? A/C kicks off @ WOT but your internal fans continue. Alternator is always pulling something or the battery would discharge A RWD fan never stops, may somewhat freewheel but is ultimately thermostatically controlled (random) FWD fan runs from battery : See Alt, even if the fan is not running the battery is still catching up a little from last fan cycle Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Andrew D Johnson Posted September 21, 2017 Technical Advisory Committee Report Share Posted September 21, 2017 2 minutes ago, Team Infiniti said: FWD fan runs from battery : See Alt, even if the fan is not running the battery is still catching up a little from last fan cycle Is it about transverse vs longitudinal not FWD vs RWD? Quote Link to comment Share on other sites More sharing options...
Team Infiniti Posted September 21, 2017 Report Share Posted September 21, 2017 (edited) 10 minutes ago, red0 said: Is it about transverse vs longitudinal not FWD vs RWD? Splitting unnecessary hairs, HP losses stack up no matter the config, belt dress and mass of the components + cooling (water pump/fan) etc... Most every car guy can feel hp jump when the belts throw (3 min before meltdown) Edited September 21, 2017 by Team Infiniti 1 Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Andrew D Johnson Posted September 21, 2017 Technical Advisory Committee Report Share Posted September 21, 2017 7 minutes ago, Team Infiniti said: Splitting unnecessary hairs, HP losses stack up no matter the config, belt dress and mass of the components + cooling (water pump/fan) etc... The HP losses are especially great if your HP has to make a 90* turn like it does on this saab. 1 Quote Link to comment Share on other sites More sharing options...
turbogrill Posted September 21, 2017 Author Report Share Posted September 21, 2017 14 minutes ago, Team Infiniti said: A/C kicks off @ WOT but your internal fans continue. Alternator is always pulling something or the battery would discharge A RWD fan never stops, may somewhat freewheel but is ultimately thermostatically controlled (random) FWD fan runs from battery : See Alt, even if the fan is not running the battery is still catching up a little from last fan cycle Are you telling me I should connect the TPS to a relay that cuts the magnetic field on the alternator during WOT? Quote Link to comment Share on other sites More sharing options...
Team Infiniti Posted September 21, 2017 Report Share Posted September 21, 2017 Just now, turbogrill said: Are you telling me I should connect the TPS to a relay that cuts the magnetic field on the alternator during WOT? yes if its worth the couple of hp and is ok with your team that you added complexity and points of failure. Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Ray Franck Posted September 21, 2017 Technical Advisory Committee Report Share Posted September 21, 2017 If net includes drive train . Also turning trans ,rear gears , all bearings , shafts ect , all adds up Quote Link to comment Share on other sites More sharing options...
Ham Sammich Posted September 21, 2017 Report Share Posted September 21, 2017 Probably just needs a bigger turbo. 2 1 Quote Link to comment Share on other sites More sharing options...
mhr650 Posted September 21, 2017 Report Share Posted September 21, 2017 20 minutes ago, turbogrill said: Are you telling me I should connect the TPS to a relay that cuts the magnetic field on the alternator during WOT? Been there done that, easy to do with MS, works great for sprint racing. Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Andrew D Johnson Posted September 21, 2017 Technical Advisory Committee Report Share Posted September 21, 2017 7 minutes ago, Ham Sammich said: Probably just needs a bigger turbo. That is the distributor, before they went with the direct ignition cassette I would assume. It looks like it might be vacuum advance too? Quote Link to comment Share on other sites More sharing options...
enginerd Posted September 21, 2017 Report Share Posted September 21, 2017 48 minutes ago, okkustom said: If net includes drive train . Also turning trans ,rear gears , all bearings , shafts ect , all adds up Indeed.. You have friction in the trans, diff, inertia to overcome in the driveshaft, axles, wheels & tires.. (friction, not just gear on gear, but viscous losses of trying to spin parts through thick oil) If they were doing this "net" test on an automatic vehicle then you have losses from the torque converter. I'm assuming the different tests which generated the OP's data were engine dyno vs. chassis dyno. Quote Link to comment Share on other sites More sharing options...
Ham Sammich Posted September 21, 2017 Report Share Posted September 21, 2017 (edited) 35 minutes ago, red0 said: That is the distributor, before they went with the direct ignition cassette I would assume. It looks like it might be vacuum advance too? Man... when did you guys get so gullible? The other real problem with that engine shown is there are NO spark plugs. No way that's gonna work. I say machine some spots for spark plugs into that head and it will probably develop more power. Edited September 21, 2017 by Ham Sammich 1 Quote Link to comment Share on other sites More sharing options...
Ron_e Posted September 21, 2017 Report Share Posted September 21, 2017 Net was before SAE net. Before SAE hp the manufacturers could test however they wish, i.e. run everything external to get gross hp. So some/everything would be driven external: fuel pump (mechanical or electric), alternator, power steering pump, oil pump, air pump, fan (mechanical or electric)... that chews up a lot of hp. Quote Link to comment Share on other sites More sharing options...
karman1970 Posted September 21, 2017 Report Share Posted September 21, 2017 Good article I found a while back https://ateupwithmotor.com/terms-technology-definitions/gross-versus-net-horsepower/ 1 Quote Link to comment Share on other sites More sharing options...
turbogrill Posted September 21, 2017 Author Report Share Posted September 21, 2017 1 hour ago, Ron_e said: Net was before SAE net. Before SAE hp the manufacturers could test however they wish, i.e. run everything external to get gross hp. So some/everything would be driven external: fuel pump (mechanical or electric), alternator, power steering pump, oil pump, air pump, fan (mechanical or electric)... that chews up a lot of hp. Maybe have two motors synced at the exact same RPM and have the second motor drive the camshaft and take all the drive train loss 2 hours ago, mhr650 said: Been there done that, easy to do with MS, works great for sprint racing. Do you drive the magnetic field directly from a GPIO output or do you have a relaly or transistor inbetween? Quote Link to comment Share on other sites More sharing options...
Ogren-Engineering Posted September 22, 2017 Report Share Posted September 22, 2017 I run cars on the dyno a bit. I ran a VW with a field wire hooked to the fan switch . No charge until you turn the fan and alt on. 2-3HP loss , charging.. It was enough that I made a full Throttle switch that cut the alt for one of the early SCCA cars. Later/now I use 3 batteries and no alternator. 4HP . is a lot on 125. Maybe 1.5 sec per lap @ Sebring. I learned the field wire deal withe ministock . Run non charging for the race and turn the fan and alt on as we roll through tech. The cam rule was it had to draw 17 in vacuum . Charging hard with e fan on dropped the idle to the 1000 and the wild cam made it through tech. Won many of the races . Quote Link to comment Share on other sites More sharing options...
ddombrowski Posted September 22, 2017 Report Share Posted September 22, 2017 15 hours ago, Team Infiniti said: yes if its worth the couple of hp and is ok with your team that you added complexity and points of failure. I suppose you could generate the same result with underdrive pulleys, but depending on make/model of car could be cheap or expensive. At least then its not an extra point of failure. Quote Link to comment Share on other sites More sharing options...
ABR-Glen Posted September 22, 2017 Report Share Posted September 22, 2017 39 minutes ago, flyinglizard said: I run cars on the dyno a bit. I ran a VW with a field wire hooked to the fan switch . No charge until you turn the fan and alt on. 2-3HP loss , charging.. It was enough that I made a full Throttle switch that cut the alt for one of the early SCCA cars. Later/now I use 3 batteries and no alternator. 4HP . is a lot on 125. Maybe 1.5 sec per lap @ Sebring. I learned the field wire deal withe ministock . Run non charging for the race and turn the fan and alt on as we roll through tech. The cam rule was it had to draw 17 in vacuum . Charging hard with e fan on dropped the idle to the 1000 and the wild cam made it through tech. Won many of the races . I'm not sure how efficient an alternator is at converting hp to amps, but the math says 4hp @ 14v is over 200 amps, that certainly seems like the upper limit of plausibility. 2hp seems easily believable though if you wait to turn it on until the battery has significantly discharged. Quote Link to comment Share on other sites More sharing options...
mhr650 Posted September 22, 2017 Report Share Posted September 22, 2017 13 hours ago, turbogrill said: Do you drive the magnetic field directly from a GPIO output or do you have a relaly or transistor inbetween? The ones I have seen used a relay. Don't forget the difference between the J607 and J1349 correction factor. Most race engine builders still use the old J607 factor since it gives a bigger number they can show to the customer. Quote Link to comment Share on other sites More sharing options...
JBgotM Posted September 22, 2017 Report Share Posted September 22, 2017 This is one of the reasons you see manufacturers trying to get all the accessories off the engine. Everything is going to electrically driven accessories (48V is coming hard). That power had to come from somewhere (engine and batteries), but once those accessories can be controlled completely independent of the engine, they can be operated much more efficiently, and also keep the engine happier. example... http://autoweek.com/article/technology/why-mercedes-new-inline-six-matters-even-if-no-one-sure-when-well-see-it 1 Quote Link to comment Share on other sites More sharing options...
ddombrowski Posted September 22, 2017 Report Share Posted September 22, 2017 18 minutes ago, JBgotM said: This is one of the reasons you see manufacturers trying to get all the accessories off the engine. Everything is going to electrically driven accessories (48V is coming hard). That power had to come from somewhere (engine and batteries), but once those accessories can be controlled completely independent of the engine, they can be operated much more efficiently, and also keep the engine happier. example... http://autoweek.com/article/technology/why-mercedes-new-inline-six-matters-even-if-no-one-sure-when-well-see-it Makes sense to me. I always thought it would have been a good idea to get all the accessories to be electrically driven and then it would be much easier to shut the engine off at stoplights. I know a lot of cars have stop/start systems now even with belt driven accessories, but its still easier to manage when they have their own drivers. Quote Link to comment Share on other sites More sharing options...
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