Hello ALL: Well took the drag car to a chassis dyno in Dothan, AL. this past Saturday. Guy running the dyno seemed to know what he was doing. The dyno is a one year old Dyno-Jet 241XL (I think that is the model number). Do not think the numbers for the three pulls really are correct for this car. He gave us a HP and Torque conversion at the flywheel from the rear wheel HP and torque readings. It just did not "add up" to be correct as I have had both SBO and BBO, both Stock and Super Stock engines dyno'd and they made more HP and torque than this car and this car has more performance items?????????? This is my first try at using a chassis dyno. To start with I changed all fluids, rear end (80/90 Valvoline Semi-syn), trans. (TCI Maxi-shift fluid and high flow filter), and engine oil and filter(Brad Penn 10w-40 race oil and K&N oil filter). New NGK race spark plugs (#7 heat range, gapped @ .040") Anyways here is the "numbers": 1st pull: Air filter in place, 35* of total advance, coolant temp. 160* reading made @ 6,000 rpm= 362 HP 399 Torque 13.1 Air/Fuel Ratio 93.5 *F 29.93 in-Hg 23 % humidity 2nd pull: removed air filter and base, 35* advance, coolant 160* reading made @ 6,000 rpm= 372 HP (+10 HP) 371 torque (loss 28 ft. lbs. of torque from 1st pull, huh ?) 12.5 Air/Fuel Ratio (better ratio) 93.82 * F 29.94 in-Hg 22 % humidity 3rd pull: advanced total timing to 37*, coolant 160* reading made @ 6,000 rpm 378 HP (+ 6 HP more from 2nd pull with total over 1st pull of + 16 HP) 379 torque (+ 8 more than 2nd pull) 12.1 Air/Fuel Ratio 93.80 * F 29.93 in-Hg 22 % humidity So he used a multiplier of 1.25 to figure flywheel HP and torque so that equals 473 HP and 474 ft. lbs. torque. Christ I had stock engines that dyno'd at 430 HP and super stock engines at 495 hp????? As dyno operator stated and what I have read the weeks prior to this test you can loose 25-30% in HP/torque in driveline from converter and auto trans. This car has a fairly "tight" converter, a JW 10" race converter, stall rated @ 3,400 rpm (flash rated to 3,900 rpm with a BB) So what are your thoughts who have more experience. I am always open to learning, and "in the old days" it was what the "engine dyno said" during tuning and what the "time slip said" that told you if you made the right heat range plug, jetting, and timing changes at the track! I was under the impression that chassis dynos were better and more accurate than those of 20 years ago! Thoughts-opinions-agree/disagree????????????????? BTW: Have not done any timed runs yet. Wanted to do this first ! My bud and I decided to limit the pulls to only 6,000 rpm to be a little conservative. The graph showed torque falling off pretty fast @ 6,000, but HP was still climbing!
What does the car weigh with driver? My old 2000 Z28 was just shy of 3800lbs at race weight. My ETs and vehicle weight suggested close to 600 HP at the crank by NHRA factoring. It made 480 RWHP on a realistic chassis dyno. But, I was able to lock my converter.
By NHRA math... it's 570-ish HP at the crank. I use chassis dynos for tuning tools, nothing more. I much prefer the dragstrip-dyno for "proof."
I wouldn't get too hung up on the numbers, they are just that. Go have some fun with that car and enjoy it. Run it some and upgrade it to make it your own. Be careful, they can be adictive and a money pit. I know I have one (different brand). Nice car by the way and good luck. Mike D.
I'm a little surprised by the engine temps. Is it cast iron heads? I would think you'd want at least 190 or more then do your pulls.
I think thats too high...my 427 camaro would run 117-118 at 3700lbs and it put around 375hp to the wheels and about 100hp more on the engine dyno. The car in the original post is 200lbs lighter and only 2mph more, so I'm guessing it's currently around ~500hp. For reference, our Red Alert chevelle did 550hp+ on an engine dyno, weighs 4000lbs+, and will trap low 120s (think I did 123 on an easy pass this summer at Joliet).
Possible. My old car went 125 MPH @ roughly 3800lbs... The math I use is as follows: ET / 5.825 = x, x * x * x = xy, vehicle weight / xy = flywheel HP. So in Dave's case... 10.7 / 5.825 = 1.8369, 1.8369 * 1.8369 * 1.8369 = 6.1981, 3550lbs / 6.1981 = 572.756 The math only works for cars that dead hook and have an efficient driveline. Cars that spin and have to be pedaled will show way less. My 2001 SS 6spd car was a prime example... Never ran better than 12.70's on 17" street tires, but dyno'd around 450 RWHP on average. Trapped in the upper teens often, went 120+ ocassionally.
clanceman427: At start of pull (going up thru the gears to 3rd) temp. was 160* and at end of pull (6,000 rpm) was 180*. Engine has fully ported 70' "E" iron heads, 72 cc's, with 10:67 comp. ratio.
That formula is 75+ horsepower off for our Chevelle, and it dead hooks [see below], and it dyno'd just a smidge over 550hp in it's *as installed* form [we lost 100hp switching from Brodix intake+dominator to 163 factory intake+950HP]...matter of fact, the splits look the same as what he posted the Olds used to run (6.8x's in the 1/8, 10.7xs in the 1/4), except we're trapping a few mph better in the 1/4 yet have a good 500lbs extra to lug around.
I guess it doesn't work for everyone... uzzled: The splits for my old car were very similar - 6.80's @ 100 MPH in the 1/8, 10.70's @ 125 at the stripe. My sixty foot times were 1.49-1.51 on 275/60-15 Mickey Thompson drag radials. My example was just to show the NHRA math, and how I got my numbers. It has worked well for any of my cars that hooked and had an efficient converter.
If you gear horsepower appropriately you would. Jim ---------- Post added at 10:56 PM ---------- Previous post was at 10:14 PM ---------- Not going to argue! Here is a good read for you if you think you want to prove your point!!!!!!! http://speedtalk.com/forum/viewtopic.php?f=1&t=7809 Jim
Maybe you should tell that to our 350ci Nova, which makes exactly 32 lb-ft @ 3900 [no, that's not a misprint], and doesn't make over 100lb-ft until 5000 rpm...yet runs low-mid 10s in bracket mode. You're technically "sorta" correct since horsepower is a function of torque*rpm...but lest we forget, we have to "accelerate" the engine [car] which means rpm. Great, great link, but I'm adding the post below...the pure "efficiency" of Stock/SuperStock cars is lost on most folks, so most anything you can glean from them should be written to memory. With that said, here's a great post from Lynn McCarty from my days over at superstockforum.com that I seem to refer more than I give credit: *** torque/inertia/horsepower *** I used to have people tell me, run the motor on torque, it is a Pontiac. How did they invision I do that? Put a low stall converter. However, when we tried that, the car wouldnt pull a fat girl off of a tricycle! You cant cram down a motor and hope it to accelerate you. Put the RPM up there like a diesel and start shifting gears!!!!Then build the most efficient converter with high speed lock up as you can get! We are getting about 2% slip at 6500rpm (according to our on board computer courtesy of JPT Jim Paquet's 2nd to none converters!!!) The 400's and 455's like the high stall speeds where the engine stays at peak power, and has the drive train accelerate the car! This is how you make a High torque high inertia car accelerate! We had 620 ft-lbs of torque, however when we crammed the motor down to the peak torque, it killed the car by about 1/2 second. This is what is so frustrating with a Pontiac. Because everytime we make a significant improvement on the dyno it occurs at 4500 to 5000 rpm. Several hundred RPM below our converter speed. So now what are we doing? [Editor's note: this is the important part-->] We are doing everything we can to cheat the motor up on RPM including large headers, retard cam, wider lobe separation, Shorter intake runners. Even if it sacrifices power, as long as it gives us more at the higher RPM's the lower sacrifices dont matter. We are also trying try Y headers on the new car, and we hope to get some exhaust efficiency with that set up. The 455's we are running 2 1/4 tubes and the 400's 2 1/8. We were helped tremendously by Jim Paquet's transmission and converter which gave us more lock up and a lighter rotating group! Thanks Jim!! Just remember, think what you would do to a Chevy, then do the exact opposite! If you run a Pontiac! Lynn
