Any Dyno Gurus?

[jhein]

Hal,

Do you know what your flywheel numbers are?

John
spf1421

[flipper35]

A 215hp Neon SRT-4 will out accelerate a 240hp Honda S2000 from a rolling start (5 mph). The Honda makes all it's power above the Neon's redline.

From C&D's Web:

"The S2000 engine's compressed power band is its downfall. You don't get all the horsepower you've paid for until the engine zings to 8300 rpm, or all the torque — that is, all 153 pound-feet — until 7500 rpm.
That's because the VTEC variable-valve-timing system doesn't serve up the hot cam until 6000 rpm, giving you just 3000 raucous revs in which to enjoy the enhanced punch before the fuel cutoff. That's fine for faster corners where you can keep the engine spinning, but in the tighter turns and full-stop hairpins, the engine falls into a crater, and it's a long climb out. "

[kountzecobra]

Fixit, the main reason I did this is to verify that my a/f ratio was safe throughout my usual RPM band. However, I find the discussion interesting about how different things affect power output, etc. It's really not neccessary, but we can never learn too much about our cars and from each other too. I think my problem lies with both carb's secondaries' opening time/rate.

[A Snake]

Here's engine dyno #s from my 427 S/O

hp 485@ 6,100rpm
torque 490 lbs/ft @ 3,900

FYI the numbers didn't cross at the "magic" 5252.

As to the high rpm Indy type engines, I would suggest that two thing be taken into account. First, they are not "normally aspirated", meaning they are stuffing air in with turbos or superchargers. Second, they have a bore and stroke ratio that would scare you. They often have less than a 1 1/2" stroke. Those engines rely on airflow/manifold pressure and rpm to make hp. 320 lbs of torque doesn't sound like much, but 853hp will break tires loose at 200mph.

Al

[mr0077]

Al, I wonder why they didn't cross at 5252 RPM...maybe the dyno tach (or some other parameter on the dyno) was out of calibration? The formula says torque in lb-ft numerically equals horspower at that RPM. What RPM did they cross? Maybe the values for torque and horspower weren't at the same scale (points on the graph)?

[George Snyder]

Curt C,

Stand next to your car? Where I get mine dynoed, you are the operator! You blow it up, shame on you.

I will say that the first time was an experience. In a closed building only two bays wide spinning the engine up to 6.5k. Upon second thought make that 6k, I changed my mind. 6k on the street sure is different than in that building.

Just setting there reassuring yourself that this engine is balanced and blueprinted to .002, so it should stay together.

Ended up I ran out of air at 5,300 and flat lined. I was disappointed, but sort of relieved too. Next runs after that were a piece of cake!

Mr fixit. It's hard to explain, but it's like you gotta know what you think you got.
Bud

[Hal Copple]

John, no, i have never had my engine on an engine dyno. I have port matched Trick Flow heads, RPM intake.

It was plenty strong up and back to Charlotte this pm, that is for sure.

hal

[ToyCollector]

This is one of the best threads I have read on this site in quite some time. Lot's of knowledge here.

David,

Are your dyno results corrected back to standard atmospheric conditions (temp and humidity)? I have dynoed some bikes and the swing between actual conditions and correcting for standard atmospheric is pretty interesting to observe on paper as well. A hot humid day with a normally aspirated motor make for some big swings (and being able to brag about gobs of HP and torque is not one of them).

[750hp]

Originally posted by jhein


I'm just gonna take a guess at this.

It would seem to me that a really high winding motor is going to probably make it's torque and HP over a much wider RPM range. That is, the torque curve will be very flat and peek torque will be available much longer and therefore be much more useful.

I don't know much about motors that turn 10000-14000 rpm but it seems to me they have to have a much wider range of useful rpm and that is one of the things makes them go faster.

Just a thought.

John
spf1421

John, interestingly enough - it's quite the opposite. Disregarding all the launch control, traction control, anti-stall and semi-automatic transmission technology, if you simply revved a Formula 1 motor to 9000rpm and dumped the clutch, it would stall!!!!! They make so little torque down low as a result of the engines being designed solely to work at stratospheric rpm. A Formula 1 engine program is deemed a major success if they can move their torque peak up another 200rpm. In the previous case of 853hp @ 14000rpm, if they don't increase their maximum torque, but simply move it up to 14200rpm, they've just picked up 12hp. If this means losing 10lb/ft at 12,000rpm - who cares! That's what gearing is for! That's why they have 7 speed automatic transmissions, and have computer simulators that calculate the gear ratios required on each and every circuit to ensure that in all situations the motor stays "in the powerband". If you hear an F1 motor at 10,000rpm, you would seriously think it was doing 3,000! Wacky engines, but certainly a testament to what some of the world's best engineers can accomplish if they're given the budget to build the best automotive parts money can buy.

[flipper35]

The only way to make more power when you have fixed displacement like the F1 cars is either forced induction, which has been outlawed there for years, or spin the motor faster.

The F1 spin faster. The curious thing though, the old group B rally cars were as fast as the F1 cars, but with "only" 600+ hp. I wish I could find the website now.

http://arturmarques.com/old_news/new...ruary_2003.htm

It isn't the same one I read before where on of the current F1 drivers got a ride in a Group B car and it scared the snot out of him.

Anyway, torque range, hp, gearing, etc are engineered to work within the intended use of the motor. I wouldn't put a 10,000rpm Por-Stock motor in my car, but they spin them that fast to make power. WRC cars on the other hand are limited to 300hp but go 0-60 in under 4 seconds (in gravel no less) because they make nearly 600ft/lbs of turbocharged torque.

Would I want an F1 engine for my car on the street, no, but I would take a WRC motor and try to live with the traction problem.

[kountzecobra]

Toy Collector, I do not know if the numbers are corrected. I will try to find out.

[Curt C.]

Ok, I did some research on the Mustang Dyno vs. the Dynojet. Go here to this Corral thread for a good uploaded article

http://www.corral.net/forums/showthr...t=Mustang+dyno

The article is in the middle of the thread. For those who dont want to go, A Camaro or Firechicken (something like that) was tested: 331 RWHP on the DynoJet, 315 on the Mustang Dyno. Good article, it dicusses differences between the two.

Mr. 0077 and AI, I bet the HP and TQ did intersect at 5252 - it has to. Its just the the Axis on the left and right denoting TQ & HP are staggered differently. Sometimes the computer will break the Axis numbering to get both lines on the same page for a better visual.

Edit: Oh, to join the testorone poisoned club and beat my chest, my little 351W yields 377 RWHP at 6000 RPM and 353 RWTQ at 5000 RPM

[kountzecobra]

Good article if you can block out the Chevy in it. It's a wonder it stayed together on the dyno.

[ToyCollector]

I love the "bottom line" at the end of the article:

Dyno numbers are for show, track times are for dough !

I think I found a new signature

[kountzecobra]

Went for a long drive with my carb parts toolbox yesterday. Tried 5 different sets of secondary diaphram springs and a couple of accelerator pump cams. Finally settled on original pump cam and "Black" coded springs (The strongest). Got rid of my very-slight stumble at WOT and it still runs great! Maybe I will try another trip to the dyno some day for a comparison.