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Horsepower Calculation
My '81 280zx N/A should be putting out 145 net HP stock. I've got:
Header Straight pipe, no muffler Cool air intake -100 pounds weight redux. 20 Degrees BTDC timing 93 Fuel BUT: according to my calculations, I'm only pulling about 100 HP This is the formula I'm using: HP = Weight/(ET/5.825)³ Does this sound right to you guys? My ET is about 18 seconds, but I've only clocked it once. It was a pretty rough estimate, because I was using my trip gauge and stopwatch. so I may bring in better/ worse timing the next time I clock it. Even with my rough results, I'm pretty sure I should be showing higher HP. What have I overlooked? I'm too poor to take it to get dyno'd. Is something just probably wrong with my engine? I'm going to buy a compression gauge tomorrow. |
I do not know anything about your calculations or how you're coming up with them, but in case you didn't know, there is a difference between the Engine Horsepower and Wheel Horsepower. All cars lose power from the crank out on its way to the wheels.
Now, onto your lower horsepower figures.. I have no idea how old your engine is, how many miles it has on it, when it has been rebuilt etc, but over time and miles engines wear in many places which slowly causes a reduction in horsepower. Cylinder wear, pistons and rings, valve guides, camshafts, rocker arms etc, and all of those small things together add up. Your modifications aren't huge so I wouldn't expect to see too much gain, and nothing surprisingly noticeable. |
That formula is just something I found online... I was hoping someone could tell me if it looked legit. I'm pretty sure it's solving for wheel HP, but I'm not sure.
So, yeah stupid question. But, the engine is 31 Years old. 160,000 miles. Pretty sure it hasn't been rebuilt. You really think age alone could reduce me down to 100 HP? I know my mods aren't very substantial, I'm just adding them so you know what's going on. Thanks |
Originally Posted by campfirestring
(Post 314041)
That formula is just something I found online... I was hoping someone could tell me if it looked legit. I'm pretty sure it's solving for wheel HP, but I'm not sure.
So, yeah stupid question. But, the engine is 31 Years old. Pretty sure it hasn't been rebuilt. You really think age alone could reduce me down to 100 HP? I know my mods aren't very substantial, I'm just adding them so you know what's going on. Thanks Of course the only way to really find out your car's WHP is to shell out $50 or so and get a Dyno run done! |
Well I know the 145 is "net" horsepower... that sounds like RW to me, but I could be wrong...
Thanks, that's the sort of answer I was looking for! |
Both "net" and "gross" hp are flywheel measurements:
Horsepower - Wikipedia, the free encyclopedia SAE gross power Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower, because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a stock test engine, generally running with few belt-driven accessories and sometimes fitted with long tube (test headers) in lieu of the OEM exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic. SAE net power In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold. |
Dyno is really just for tuning and see how mods affect performance. If you dyno your car and it tells you you have 104rwhp what does that mean to you?
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haha guys, I just want to know! when you get something new to you, it's natural to look it over to know where to begin. The more I know about what I don't have to fix or replace, the less money I will spend needlessly as I slowly improve performance. I'm only interested in mods for curiosity's sake. lol I don't even RACE! I'm not even one of these punk kids who thinks they know shit about cars... so humor me, please.
:102: BTW: my cylinder compression is (1 thru 6) 160, 160, 170, 160, 170, 170. good enough to not need a rebuild, right? |
Pressures are where they should be. Your engine is fine. Try putting in a new blaster 2 coil and a good set of plugs and wires and a fuel filter. I found those to make the most difference over stock. Then go to a night drags or test and tune and weigh your car there and get real numbers and you will be able to get near the exact rwhp figures
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PPK posted his dyno results a while back. New exhaust and a few other things... 113whp stock, to 130whp with mods:
https://www.zdriver.com/forums/280zx...z-28955/page6/
Originally Posted by PurePontiacKid
(Post 272184)
dyno results are in!!! had a NICE gain in the power department from last year, as well with the torque. The power band is also quite a bit wider as well. my car sounded SO NICE at 6500rpm on the dyno :D
results comparo: 112.91whp/145.42wtq 130.49whp/152.31wtq |
Thanks shady, will do.
Nismo, his exhaust is what got me. I lost it. lol |
Correct me if I'm wrong but I'm pretty sure your timing is way off. If memory serves me right it's supposed to be set at 8 degrees btdc. That may be causing a lower power issue. I was running the same mods as you except mine wasn't straight piped however the cat was eliminated and I was running a 16.429 at Autoclub Dragway with 183,000 miles on my motor.
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Well, I very well could be at 16.5. lol it was a VERY rough run.
I'm at 20' because shady suggested it on another topic, haha. I wasn't too surprised by my time, because even by manipulating it in within my formula, it still came out to 100-ish rwhp. I was more concerned about whether or not my formula was legit. |
20 deg is for the turbo engine
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Shady is running 20* BTDC, but he has a lot done to his n/a motor. ~10*-15* would be about max for a stock n/a.
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Shady isn't quite stock :)
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hehehehe, you can do it on any l28e. just make sure you have good gas (91+ octane) and listen for ping
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What is the "all in" total advance optimal for the L28ET? I was talking to a guy in the know about the L16 and he says all in you don't want more than 32 deg but part of that is the displacement (eg area across the piston).
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all in for most motors is 36-38 deg. That said it can vary depending on the rest of the variables. I know with my n47 head I couldn't do that much timing at all. I could do 30-32 deg max without ping and 94 octane.
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