How does GM measure horsepower?

[deerefan]

When I bought my new silverado, i was told it had 315hp/335tq. The truck feels alot stronger than this. I drove a Titan that had similar hp numbers and it felt the same acceleration wise. Does GM measure these numbers at the rear wheels or flywheel? This trucks acceleration acts more like 350hp, which has me curious.

 

[sweettractors]

I am betting the GM 327 CID engines from the mid sixties with 300 hp will run circles around the 350-400 hp rated cars and trucks of today. Ken Sweet

 

[Diamondpilot]

When I bought my new silverado, i was told it had 315hp/335tq. The truck feels alot stronger than this. I drove a Titan that had similar hp numbers and it felt the same acceleration wise. Does GM measure these numbers at the rear wheels or flywheel? This trucks acceleration acts more like 350hp, which has me curious.

I have often wondered the same. By the way, the Titan has way more TQ (385 ft lb) but that is a mute point. As our buddy Builder has implied its more to do with the drive line and where the power is made. Keeping the truck in the power band is what is important then getting that to the ground.

Just like you I came out of another truck with similar numbers, 2007 F-150 with 300 HP and 365 ft lb TQ and the Titan feels much much stronger, especially on the bottom end where it counts.

Chris

 

[ace10]

Gearing.

 

[deerefan]

I am betting the GM 327 CID engines from the mid sixties with 300 hp will run circles around the 350-400 hp rated cars and trucks of today. Ken Sweet

It is funny you say that. I actually have a 300hp 327 in a 66 Nova and another in a 1970 Chevelle. My buddy had reg cab silverado 2wd with the 5.3, a tune and exhaust. The Nova can't touch him and the Chevelle gets him in the quarter, but barely. Both 327s were built to 300hp specs. Now, you want to see something funny? My dad's 70 350/350hp Vette hanles the new 400hp Camaro with ease, about 3-4 car lengths. Go figure. The main reason I feel the silverado gets me is not only hp. The throttle response and quick shifts are seamless as compared to both muscle cars. I think it is more technology making him quicker than raw power.

 

[JasG]

When I bought my new silverado, i was told it had 315hp/335tq. The truck feels alot stronger than this. I drove a Titan that had similar hp numbers and it felt the same acceleration wise. Does GM measure these numbers at the rear wheels or flywheel? This trucks acceleration acts more like 350hp, which has me curious.

There is a lot more to acceleration than just HP. Weight of the vehicle, gearing, both tranny and rear end, shift points etc. Unless you know the trucks are set up similar it is very hard to make an apples to apples test based just on acceleration or feel. I've driven 2 trucks that 1 had a 3.08 rear end, the other a 3.55, yet everthing other than that was the same, the 3.55 would smoke the 3.08, yet the 3.08 had better MPG. Now the MFG's are playing with the trans a lot more, of course they have more gears now to play with.

Every MFG likes to play with numbers to make sound like they have bigger engine.

At least thats my opinion.

 

[Heywood Jannockitov]

One of those TV programs such as "How do they do it" or Modern Marvels" or something showed a GM engine plant where they were testing the output on an engine with an SAE approved inspector present monitoring the test. It was just an engine on a test rig attached to a dynamometer, so I would guess the HP is measured with ancillary devices attached such as alternators, power steering pumps etc, but no driveline.

How a truck "feels" acceleration-wise is pretty subjective too, I would imagine. There are many sensory inputs to the brain that help enhance the impression of "delta V". Trans gearing, rear end, power to weight ratio, traction, exhaust tune (how pleasing it sounds!), suspension tune (how much the front end lifts when you put your foot into it, suppression of NVH.

All these things can make one truck "Feel" faster than another even if it really isn't.

 

[jonyyuma]

There is a lot more to acceleration than just HP. Weight of the vehicle, gearing, both tranny and rear end, shift points etc. Unless you know the trucks are set up similar it is very hard to make an apples to apples test based just on acceleration or feel. I've driven 2 trucks that 1 had a 3.08 rear end, the other a 3.55, yet everthing other than that was the same, the 3.55 would smoke the 3.08, yet the 3.08 had better MPG. Now the MFG's are playing with the trans a lot more, of course they have more gears now to play with.

Every MFG likes to play with numbers to make sound like they have bigger engine.

At least thats my opinion.

The old rule still stands. "It is how the Horsepower is applied to the ground". The ratings are set to confuse the consumer.

 

[sweettractors]

It is funny you say that. I actually have a 300hp 327 in a 66 Nova and another in a 1970 Chevelle. My buddy had reg cab silverado 2wd with the 5.3, a tune and exhaust. The Nova can't touch him and the Chevelle gets him in the quarter, but barely. Both 327s were built to 300hp specs. Now, you want to see something funny? My dad's 70 350/350hp Vette hanles the new 400hp Camaro with ease, about 3-4 car lengths. Go figure. The main reason I feel the silverado gets me is not only hp. The throttle response and quick shifts are seamless as compared to both muscle cars. I think it is more technology making him quicker than raw power.

How much HP did the tune add to the 5.3 Silverado pickup? Ken Sweet

 

[deerefan]

How much HP did the tune add to the 5.3 Silverado pickup? Ken Sweet

He picked up 22 hp with the addition of tuner and exhaust. I believe the tuner is from hypertech. The truck is an 05