Watching videos of dyno testing (primarily Engine Masters) every video of testing they bring the rpm gradually to WOT. Has anyone tried slamming the throttle wide open on the dyno like you do at the track, or could you even do that on a dyno? Would it yield the same results as far as hp and tq? Would it be like comparing apples to oranges?
It really doesn't matter so much on how fast you load the dyno. The testing does not commence until the engine is at WOT against the water brake, and stabilizes for a few seconds. Here's a guy who has done over 10,000 engines in his career.. figure an average of 10 pulls per session, it means he pulled an engine against the brake more than 100,000 times, so you can consider how he does it as the "correct" way. This video has both carb and EFI pulls. I see a lot of guys sneaking up on the water brake with lots of rpm and little throttle opening, and when I see that, I usually figure they are inexperienced on the machine, or they are worried about the durability of their dyno water brake. JW
Genuine question, how is power even measured through the RPM range if slamming to WOT. I guess I might dive a little deeper into how dyno's work. My assumptions are a slow ramp up would better measure power through an RPM range and ideally there would be no variation in fuel systems (CARB/EFI), ignition or other systems. But I see most people put a bowl on the carb/EFI to do these pull which is not reflective of reality in a car. For a race application no one cares, its WOT from a stop to finish line. For a slower linear RPM ramp up, understanding power might be valuable to understand street drive-ability and shift points. Or maybe it doesn't matter at all. I can see value in both WOT pulls or slow RPM ramp ups.
Chad, Watch the video again carefully. Torque is measured mechanically, at 100rpm intervals. Non of this happens until the engine is at full throttle with the full torque of the engine at the start rpm. It is not measured as the throttle is being opened. Here's the sequence of a pull. Start the engine and stabilize it. At this point, the water brake (aka absorber) is filled with enough water to fully hold the engine's output. The throttle is the opened to WOT, with the absorber of the dyno holding it to whatever rpm the operator has it set at for the start of the test. Typically around 3400 rpm for a modified street type engine. the test should start at least 500 rpm below the torque peak, to get accurate results. Once the engine stabilizes against the water brake at WOT for a second, the operator then pushes a button on the console, and the computer starts the test. Computer controlled flow valves are then used to reduce the amount of water in the absorber unit, to let the engine accelerate at a preset rate. The industry testing standard is 300rpm per second. Attached to the outer shell the absorber is something called a stator.. this unit is hooked mechanically to a load cell, that measures torque, at 100rpm intervals. The computer on the dyno allows the engine then to reach it's max rpm that is set by the operator. Once that is reached, the throttle is then closed mechanically by the operator, and the test is over. Dyno's measure torque, hp is a mathematical equation. Torque x Rpm /5252 = HP The "bowl" on top of the carb or efi throttle body is actually called an Air Bell. It has a turbine fan in it, that measures airflow, and does not change the output of the engine, we always test with and without it to make sure of that. Some carburetors, Q-jets in particular, don't function properly with the air bell sitting right on top of them.. For a Q-jet I have the base of a GS 455 air cleaner that we put on top of the carb, and then the air bell goes on top of that. If you measure the air into the engine, and the volume of fuel flow thru flow meters to the engine, then you can exactly determine the Air Fuel ratio, which is critical for correct engine operation. Too little fuel won't make all the power it is capable of and taken to an extreme it will detonate and destroy the engine, too much fuel and it does not make the power it is capable of. Over the air bell is draped a large flexible hose, that delivers air to the engine from outside of the room, so the temp of the air going in the engine stays stable, while the room heats up or cools off during a pull. A correctly setup dyno cell draw cool outside air into the room during a pull, from an air exchange unit, whose inlet if often mounted on the roof of the building. The cell I use is so efficient at cooling the room, that often times in the winter months, you will see the air coming out of the engine breathers condense as it hits the cold air. But the air going into the carb is drawn out of the shop area outside of the dyno cell, that is maintained year round at around 70*. A good dyno setup is measuring RPM, fuel and air volume going into the engine, oil temp and pressure, inlet air temp and water temperature. It is also programed with a air temperature and a barometric pressure reading at the location of the testing, so that it can then correct the raw numbers to a "Standard Correction". It does this by calculating some thing called Density Altitude, which is abbreviated DA. This eliminates the variables that you would get with different dynos, in different locations with different base altitudes, as well as compensating for changing weather conditions.
My engine on the Dyno. You can just about see the throttle arm go to WOT, hear the engine being loaded down, and then listen as the engine RPM increases against the water brake. Here's another video I got from Jim. This was the 1st motor he built for me. It made 608 HP and 596 TQ. You can watch the throttle arm in this one,
Cool stuff! When you hear the engine under load ( sounds like it’s bogging) is the dyno measuring torque at that time? Is it possible to have the absorber set where the engine doesn’t have enough torque to overcome it or does the computer not allow that to happen by releasing water to complete the test?
After what sounds like a bog, listen for when the engine starts to accelerate. That's the beginning of the test. My test started at 3700 RPM, Jim also did a lower pull. It started at 2800 RPM. That is really stressful for the motor so he only does it once. Jim told me that the Dyno stresses the engine more than anything you can do to it on the street.
Mark, doesn't the 1970 Stage 1 pulls it's 510 ft lb of torque at 2800 rpm's? Isn't this the very reason why the Buicks were able to out run there competitors. When I look at Larry's Dyno sheet, it appears the higher torque numbers come at a higher rpm level. My guess for that is, all the high tech performance engine mods that are in Larry's engine that are way pass what an original 1970 vintage Stage 1 produced. One of the reasons I have been looking for a "Pure Stock" Stage 1 engine Dyno pull, is to see what the 1970 Stage 1 455 engine "really produced" in Torque & HP. I'am really curious if it really pulled 510 ft lb of torque and the 376 HP I heard that it really produced. Haven't found that pot of gold yet. All the Dyno'ed Stage 1's with 455's have all had some type of power adders or they don't retain their original camshaft. Maybe, one day I'll get lucky or maybe not. Vet
That’s what was advertised, but from what I’ve heard and read, nobody has been able to duplicate that from an original untouched Stage 1 455. The hi compression 350 for 1970 was rated 315 hp and 410 ft lb, who knows if those numbers are believable?? Either way, the 455 Buick is one of the most respected and feared muscle car engines from the 70’s Its torque output is legendary.
You are the first to agree with me on the forum, Ya. I know I can't find any info to back up those numbers either. That said, wouldn't it be fantastic if some Buick factory engineer had a stash of Dyno sheets from 1970 and said, think it's time to release these numbers!!!! I would love it, and remember, the 70 Stage 1 only had the 750 QJet. Wonder what those numbers would look like with a 800 QJet???? When I look at an LS6 1970 Chevelle 450 horsepower at 5,600 rpm and 500 lb-ft of torque at 3,600 rpm, not that far off the Stage 1, but advertised with a ton more HP. It's difficult for me to believe the Chevelle's HP number and it's only 10 ft lbs lower torque, but comes at a higher rpm number. Something doesn't add up here because the Stage 1 beats the Chevelle hands down at the strip. Vet
Yes, but that is only at WOT. You guys need to get to Bowling Green next month and talk with Denny Manner. Here is what Jim said about the stock 455 engine power, https://www.v8buick.com/index.php?t...ic-era-muscle-cars.357666/page-4#post-3090405 https://www.v8buick.com/index.php?t...o-and-dyno-results.153248/page-5#post-2792139 https://www.v8buick.com/index.php?threads/tsp-level-1-350-buildup-info-and-dyno-results.153248/ Read through the above threads.
The one I used to like was the one JW had on here somewhere you have a look down the carb as the dyno is turned on and you can see the squirters and the venturies pour the gas in. Mags were never going to let the Buick be better than a Chev.
If the 350 had a true 10.25 comp it may put out those numbers advertised but I would think it never really got to that number on comp. I bet with 10.5 comp on that stock motor would have a lot of tq. Leave the internals alone and put the alum heads on it and the TA intake with a 800 Q-Jet I bet that will be more like it. These are the things nobody does or does not try it. Then add all the hot rod goody parts
If you look ok at the rpm the LS6 made that 500 ft lbs, 800 rpm higher than the Buick YEP! The power of the media wanting you to know what they think you should know was alive and well back then too!
Chevy was inflating those numbers to sell cars I believe. But reality showed differently. I really don’t put much stock in factory numbers. The race track will tell you what your making
When I was a kid the guy next door had a GSX and at the time I knew nothing about Buick and later on in the years when he saw my Buick in the drive he cam over and told he once owned a GSX and he told me it was the fastest car he had ever driven and him and his friends had some real hot cars in the day. and That was the reason he ended up selling it. The only thing that I ever noticed about his car was it had a really cool hood Tach...that must mean it is really fast right? Other cars had 160 mph speedos. I was then put on a path to like all hot rods been a car freak ever since lol
That's right. I remember a magazine big block shoot out where the final contenders were a 70 Stage 1 and an LS6 Chevelle. The Buick won, but they had near identical trap speeds, yet the LS6 claimed 450 HP vs. the Stage1's 360 HP. The Stage1 was Dave Hemker. The article was in the January 1999 Musclecar Review.
Reminds me of my friend two streets over had a neighbor across the street had a ‘70 GS 455 in his garage he was “gonna fix up someday” not sure if it was a Stage 1, probably not.
