5.3L Dyno Disappointment


EA$Y_MONEY_04
05-20-2004, 04:08 PM
I put my truck on the dyno today and was very disappointed. The only item from my signature not installed yet is the K&N 77 series intake. The dyno showed a seemingly low 243hp to the rear wheel. Anyone have comments or comparable dyno results. 04 silverado Ext. Cab 1500 5.3l. Thanks

chevytrucks92
05-20-2004, 05:20 PM
I'd say that sounds about right. They say you loose 15-20%. So if you lost 20% (seeing as how its a truck, it probably did) then that means you should have about 291 or so hp at the flywheel. Those trucks are rated for 295, so thats pretty close.

chris97b
05-21-2004, 02:38 PM
That sounds right for stock, but with all those mods, you'd think it would get more than that. Are you running the auto or manual? I'm thinking the auto might lose even more than 20%.

EA$Y_MONEY_04
05-22-2004, 12:22 PM
I am running auto. The only mod I didn't have on for the dyno was the K&N cold air intake. Also I just added a throttle body spacer. I am thinking there is some false advertising on the stock hp of the truck. They say 295 engine hp. I think I'm going to take all my mods off and dyno it again. I am betting its below what they are saying. With all my mods, saying there is a 20% loss to the rear wheel, I am still at-under the stock advertisement. Oh well still love it and its faster than my 2000 4.8l.

CRUZING93
05-25-2004, 01:03 AM
Is that false advertising, I just got a silverado 5.3 auto. I will be very interested in those dyno results. Oh and what are your times on the quarter mile? if you have tested it?

Destroyed_1500
07-08-2004, 10:15 PM
Hello,

I am new and had been browsing the site for awhile. Where did you take your truck to have it dyno'd? I let the local vocational school dyno mine yesterday and they totalled it. Supposedly the chains broke and the truck's passenger side collided with the garage door. The damage is extensive and as one might imagine i'm not please. I tend to think some smart little punk dropped into 4hi and then it took of. That is all I can think of that would possibly cause it. Does anyone have any legal advice for me?

Destroyed_1500

Silverado Brethern
07-08-2004, 11:07 PM
well i'd say they would be responsible for repairing or repalcing the truck. and also i have a 97 with a 350 in it and it dyno-ed at 232 hp and the only thing i have done to it is custom dual flow master exhuast.

chevytrucks92
07-08-2004, 11:12 PM
well i'd say they would be responsible for repairing or repalcing the truck. and also i have a 97 with a 350 in it and it dyno-ed at 232 hp and the only thing i have done to it is custom dual flow master exhuast.

Wow, those were just rated at 255! Either you have a ringer or GM just seriously underrated those! That would come out to nearly as High as the current 5.3s.

huminski
07-09-2004, 08:26 AM
I think the hypertech web site shows a stock 5.3 with the HPPIII pushes 275 or so at the rear wheels. Let me look.....

yeah, though 256 stock sounds high for a 2000 5.3, no?

I'd say you might have something causing a power loss somewhere....

http://www.hypertech.com/images/dynocharts/2000gm5.3L.jpg

chevytrucks92
07-09-2004, 08:44 PM
Man that's alot of torque at just 1500 rpms in stock trim! Thats nearly 80% of its peak stock rated torque at 1500 rpms, and that torque curve is pretty flat too.

bans25
07-10-2004, 09:40 AM
There could be many factors to differnt dyno results.

1) Not all dyno's will give the same HP #'s, some can be 5% more difference

2) Temp, was it a hot day? was the truck heat soaked?

3) Fuel.. did you have bad or low octane fuel? did you have KR?

4) altitude, closer to sea level produces more HP..

all and all I don't think you are far off, GM's claim of 295 is an average, some are higher, some are lower...

Vortec327
07-12-2004, 09:22 AM
There could be many factors to differnt dyno results.

1) Not all dyno's will give the same HP #'s, some can be 5% more difference

2) Temp, was it a hot day? was the truck heat soaked?

3) Fuel.. did you have bad or low octane fuel? did you have KR?

4) altitude, closer to sea level produces more HP..

all and all I don't think you are far off, GM's claim of 295 is an average, some are higher, some are lower...

I have also heard that some dyno's "play" with the ambient temp reading to overrate the results. For example they would set the ambient temp input to the dyno computer to 110F instead of the true (say 70F) and as a result the SAE corrected HP/TQ #'s become higher....thus making you as a customer go :naughty: .

Shortbus
07-12-2004, 07:00 PM
Some of this has already been said but here is my 02cents on power ratings. Manufactures rate horsepower readings from SAE net horsepower. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349. Because SAE net is so common, this is the standard we will use to compare all others.

Factory ratings are all well and good, but many enthusiasts modify their cars and then want to see how much of an improvement they got from their labors. The problem is that most of the time people are not interested in ripping the engine out of their car to have it tested on an engine dyno; no, they're going to be testing on a chassis dyno. The most common chassis dyno, the inertial dynamometer (popularized by DynoJet), measures the horsepower as delivered at the power wheels -- whether front or rear.
But testing rear-wheel horsepower (rwhp -- obviously, front drivers would be measuring fwhp) makes it difficult to convert from what the dyno says to what the manufacturer says. The manufacturer, remember, measures horsepower at the flywheel. All that equipment between the engine and the wheels -- the transmission, driveshaft, differential, and axles -- introduce friction and inertial losses summarized as "powertrain loss" or "parasitic losses". The efficiency of the driveline can greatly affect the amount of the powertrain loss: Ford's AOD transmission, for example, is notoriously inefficient. As a very general rule, rear-wheel horsepower on a manual-transmission car is about 15% less than SAE net, and rear-wheel horsepower on an automatic-transmission car is about 20% less than SAE net.

Those horsepower numbers presented in advertising and brochures aren't always accurate. Though manufacturers are supposed to base their horsepower ratings on SAE net standards, they are not completely beholden to it. They often fudge the numbers. Ford and Mazda both recently got in trouble with the Mustang Cobra and the MX-5 Miata, respectively, when they delivered a car that had less horsepower than what they advertised. Ford ended up doing considerable warranty work to bring the numbers up where they belonged, and Mazda re-rated their car and offered to buy back any offended customers' cars. General Motors regularly underrates their engines, most notably the GM LS1 5.7L engine as installed in the F-body (Camaro and Firebird) cars. Mechanically almost identical to the engines installed in the Y-body car (Corvette), the engine mysteriously "lost" 40 advertised horsepower in the F-body chassis. Although this technically is as fraudulent as selling a car with less than the advertised horsepower, no one seems to complain when they get a car with more horsepower than what appears on the spec sheet.

So hypothetically if we say you lose 25% of the hp on a inertial dynamometer then 294 - 25% is 221 hp. You stated you have 243, I would say that sounds about right. I wish I could say my Silverado has that much HP. :)

Of course the above is just hypothetically, who knows what temperature, elevation, ect GM is basing their numbers on.

ldr1ff
07-13-2004, 10:50 PM
I am not sure if anyone had already posted this but as you have said you are getting the horsepower at therear wheels. The factory rating is at the flywheel. 15% loss at the rear wheels is actually pretty good.

Gregg

ldr1ff
07-13-2004, 10:51 PM
I am not sure if anyone had already posted this but as you have said you are getting the horsepower at therear wheels. The factory rating is at the flywheel. The loss at the rear wheels you are getting is actually pretty good. What was the horsepower at the rear wheels before the mods???? If you did not test that, your are comparing apples to oranges.

Gregg

Add your comment to this topic!