how You got Your HP rating?dynamo,combo specs?

[coolcarz]

Hi Friends, Question for all, if you show(like here in the forum,ei my 440 has 400 hp) or tell anybody that you might talk to on the street or friends ect... what your horsepower is and/or the torque rating of your motor, how did you come by that number? just wondering? What do you use to get those numbers, ???? (except if it's a stock motor) just wondering.............

thanks coolcarz

[bubby440]

i race my car 2 or 3 times a year. i figure my HP from it's 1/4 mile performance, usually the mph/weight calculation.i use my computer software strickly for reference,but it usually comes within 2-3% of actual results.

[1972roadrunner]

i have desktop dyno 2000 on my computer... thats how i figured my estimate...

520HP @ 6,500 RPM
465 ft/# torque @ 5,000 RPM

course, that would probably be with a better single plane intake...Rumblefish360 suggested to try selecting a dual plane... heres the numbers for that...

476HP @ 6,500 RPM
445 ft/# torque @ 4,500 RPM


these numbers are off the bottle, and at the flywheel... anyone know about how much rear wheel HP i would have with a 727 and 4.10's and P295/50 R15's in the back?

thanx!

[rumblefish360]

I tell people that ask that it has about...about I said...435HP.
I get this from the starting point of the Edel. flyer advertising there RPM package for the 340. 417 HP/ 397 lbs. torque.
Add more compresion. 1 1/2 points more.

Things to consider, but didn't add to the total.

1). The purple cam is better designed than the Edel. for it's steep ramps. Even though I like the split pattern of the Edel. cam.

2). I don't run a 340. I run a 360. Even though it's 20 cubes larger, the added cubes are in stroke. This will add HP. But not that much, as opposed to the gain in torque I get from the 3.58 stroke vs. the 3.31 stroke, of the 340.

From the 2 things, there could be a few HP more added to the top.
Say 5 hp from the cam???? 10 HP from the stroke?????
Who knows.....

The reason for the suggestion I gave in 1972roadrunner's post is that the single plain TorkerII was a loser to the RPM in a Mopar muscle mag dyno test.
I believe that the TorkerII is an OK unit. Get it cheap and your set. Buying brand new...RPM it!
The single plain setting on the DTD program, should be looked at as a race intake on a built engine. IMO
Even before the mag's test, I couldn't see it adding 50 or so HP to the engine. However, if it's a race intake on a seriously built 340 or stroker 392, I could see it when next to a dual plain.

[bubby440]

most drivetrains with an automatic transmission you will lose 18-22%,but it also depends on the mods to you drivetrain.there are a lot variables.
-convertor slippage
-trans (clutch lockup)
-the types of fluids, natural grade or sythetic
-weight of the parts in your drivetrain,even tires & rims

72roadrunner
i also have a 72 runner that i have run for about 12 years now. my second setup in the car ran about the same numbers that you have. my car would run 110 mph through the lights,with a 18% power loss @ 3850 lbs. my car calculated to -400hp at the tires & 472hp at the flywheel. IMO the only hp that counts is what you put on the ground.

[cuda66273]

......or you can go to www.prestage.com and go to the Automotive Math section, click on the HP calculator and enter your numbers......I figure it's a real close estimate.

[dacuda]

i got mine on a dyno and it made 572hp/590tq

[The Dartman]

Desktop Dyno/Dyno 2000 blows HP and torque numbers way over what they actually are.

Dyno 2000 apparently thinks my combo makes 420 HP. This is a 12.5:1 318, with a 517/292 cam, stock J casting heads, with a 750 on a single plane intake. Most horsepower/ET calculators put this motor, based upon a best ET of 12.87 in a 3400 pound car, somewhere around 295 HP. I would guess that it actually makes about 325 HP without converter slippage, almost a full 100 HP less than advertised by Dyno 2000. If my car actually made 420 HP, I should be wrapping off 11.60's in the quarter!

What Dyno programs are good at is finding the right parts to put together. I am in the process of determining what mods to make to my 440, and to see the differences between some of the cams is really helpful. I have a DYNO 2000 440 buildup that is set to make 610 "virtual" HP (510 real?), and I could see easily what really helped the performance. Case in point: I have a 554 lift roller cam from crane in the .040 over 440, with EB Heads, a single plane intake with a 750 Holley in a Dyno 2000 buildup. It makes 610 virtual HP, and the closest I could come to the 610 HP was 570 with a race only .595 lift mechanical camshaft. So it does a good job of heping me match parts for a new buildup.

As far as people stating that thier motor makes a certain amount of HP, 95% of poeple will never get their car on a chassis dyno, or ever have their motor on a Dyno either. If your really wondering how much HP your car has, go to the track!! A horsepower/ET calculator will give you a fairly accurate number, based upon a real pass. It is well known that a 500 HP motor with the right parts behind it, in a correctly prepared 3000 pound car can turn 10 second time slips. Do those people that throw out (nearly) unbelivable numbers, look like they have a 10 second (or 11 base dupon weight) car?

I really wouldn't worry too much about what HP numbers people are throwing around... there's too many different ways to guess at what it actually is...

Dartman

[sanborn]

You have engine dynometers, chassis dynometers and various "Desktop Dynometers". All have a place and all are useful.

We have used engine dynometers, but even there is room for error(or manipulation) of the results. All engine dynometers are supposed to be corrected for sea level, barometric pressure, etc. and get the same number(HP/ torque). We have found the the GO Power unit is the most optimistic, followed by Superflow and Stuska is the most conservative. For example if we say the Stuska is 100% accurate, then the Superflow is about 13% more and the GO Power is 18% more.

The chassis dynometers also use "correction factors" to abtain the HP/torque numbers. Those factors can also be altered to get bogus results. Chassis dynometers do take into account drive train losses and should give better, usuable numbers.

I have just become somewhat knowledgeable about some of the Desktop Dynos and must say the numbers are fairly close to real dynometer results PROVIDED the engines are properly prepared. For example, if there is a port mismatch, the real dynometer will find it, the Desktop Dyno assumes everything is perfect. The Desktop Dyno assumes the carb jetting, timing is perfect, etc.; we all know in the real world that is not the case. The Desktop Dyno uses one factor for parasitic friction losses, the challenge in the real world to minimize them.

So I guess what I'm saying is the Desktop Dyno is very useful for choosing combinations, maybe somewhat optimistic depending on how well the engine is prepared. The chassis dyno is very useful because it tells you what you are really putting to the ground. But, if you are searching for that last HP(development work), the "real" engine dynometer is the only way to find it(and even there it is sometimes hard to find).

[cuda66273]

Dartman:
Did you plug in your numbers on the www.prestage.com web site? I think you'll find that with their calculator your guesstimate id pretty close.

The number to study is the one beside the WIN on your time slip ...

[451Mopar]

DartMan, Desktop Dyno actually does a pretty good estimate of power and torque, but you have to be careful with the inputs you use, expecially cylinder head selection. The computer simulation software also estimates power assuming the engine has optimal air/fuel jetting and ignition timming.

To work out proper jetting and ignition timming you should put the car on a chassis dyno, or at least tune the car at the race track.

I tuned my car at the track, then had the chance to dyno the car on the chassis dyno. The jetting was very good as recorded on the dynos wide band o2 sensor. Some other cars dynoed the same day had really screwed up carb jetting and that really hurt the engines performance.

Anyhow, the Charger dynoed with 455 HP @ 6,100 RPM (Using the SAE correction factors) at the rear wheels
When comparing power be careful of what correction factor is being used as to will change the indicated power.

[AAR4fun]

sanborn nailed it! Dynos are relative.

Primary value of a desktop is baselining a combination and begin subjecting the baseline to changes. Great for cam selection.

Engine and chassis dynos primary value is optimizing or tuning what you've bolted together in the real world.

[dynorad]

Almost everyone has a lot less power than they think. We have been conditioned by the magazines to believe that it is common for a small block to put out 500 HP.
I have been measuring HP of various cars for the last 6 months as I have been finishing the dynorad and getting data from my first customers. Here are some examples:

451Mopar's car, a 71 charger with a Brodix headed 451 and a mechanical roller cam. This is a very powerful car. Uncorrected HP at the rear wheels is in the 380 range.

500" big block in a 68 Charger. Indy heads, hydraulic cam. This is also a very powerful car. 360 HP at the wheels. Runs 12.30's.

Stock 95 Z 28. 195 HP at the wheels.

1986 turbo Omni NHRA stock class record holder. 159 HP at the wheels.

Note that all these cars were run at Denver elevation so they are down by 20-25% from standard conditions. But even with the correction the numbers don't match the magazine articles.

So far I have had one guy give me an estimate before we started that matched the outcome. There are several others who have been severely disappointed with their power numbers. (none of the ones listed above) Here's an example:

340 in a 68 Cuda Notchback. The car is tubbed with huge tires on the back, ported heads, MSD ignition, big tube headers, a single plane intake and a big Holley carb. Runs on race gas. Deafeningly loud. 200 HP at the wheels.

If you want to know what you really have, you need to measure it.

[pishta]

Man that '68 Cuda must be running cement in his transmission for that much loss! I would be replacing parts fast...I tell everyone my mill makes 235 from the factory (because it has the "S" on the fender) If I beat them, I smile. If they beat me, I shrug and admit they have a pretty fast car. Edle says 397 with their RPM package, and Im pretty close with a better cam and better headers and a better carb.

[Doug Wilson]

I don't think this can really be used for comparison, since the mearurements must be taken with all conditions exactly comparable.

Can't happen.

Prove at the track, then work backwards.

Hell, you can't even get two scales to give the same weight of the car within 250 pounds.

[cuda66273]

Dynorad:
It would be interesting to run their time slips through that program on prestage.com and see how close it is to your true dyno HP.

On that Cuda did you run the RPM to MPH numbers to see if his convertor was slipping?

Did you do any tuning to see if was just messed up...seems it should put out more power than that????

[dynorad]

The Cuda had a 4 speed. There was nothing wrong with the tranny or clutch.
This car was just the victim of poor tuning and perhaps mismatched parts. It just shows the danger of trying to guess your power from the stock power plus something for each aftermarket part you have added.

I will check the prestage.com site and see how the numbers stack up.

[cuda66273]

Everyone take note here.....

This car was just the victim of poor tuning and perhaps mismatched parts

Before you get out your checkbook, get out your calculator, do your reseach, get my approval :-), develope a plan and stick to it.

[dynorad]

I ran the numbers for the 68 Charger with the 500" big block. I got some data from the owner and when I used the prestage.com calculator for HP from MPH and weight the result was within 2% of the result posted earlier.
If you include a revised (new since I did the testing on this car) mass correction that calculates mass factor from final drive ratio (RPM/MPH in the gear tested) the numbers match inside of 1%.

My assessment is that the prestage.com calculator for HP vs MPH and weight is pretty good.

[cuda66273]

Excellent observation Watson....:-)

So the Fish made 352.24 HP at the rear wheels on that 12.186 pass, are we safe to say that if we use a multiple of 1.25 we'll get pretty close to crank HP?

So that number comes to 440.3 HP, jeeze now I've impressed myself! There's lot's of Big Blocks, Mopar and Off brands that don't make that kind of power...

Does your dyno have a more acurate formula for calculatinig crank HP from wheel HP?

[cuda66273]

So now all I need to do is find another 26 HP at the crank to get to a 11.95....hummm....I have a new carb and fuel delivery system coming ...I wonder?????? maybe?????....Super Pro lines up in lanes 3&4?????

.....beating up on all those little black boxes with a foot brake and a Iron Headed, Mighty 318 Mopar ......Priceless...

[Doug Wilson]

Pretty cool.

[cuda66273]

Doug,

You gonna be there for dinner sat. night????

[451Mopar]

Like DynoRad said, uncorrected My Power is about 380 HP at the rear wheels. Corrected per Dynojets dyno the power 455 HP @ 6,100 RPM at the rear wheels.
I don't know how much loss I have through the drivetrain, and runing all the accessories (waterpump, mechanical cooling fan, alternator and power steering pump) which are usually not ran on an engine dyno except maybe the waterpump?
This is also in full street trim, example; full exhaust with mufflers, airfilter in place, running pump gas, and engine tempature at 210 degrees! (I need a new radiator!)
Also, I am not sure if my ignition timming is optimal.

If you account for the losses from the drivetrain, accessories and non-optimal engine tune-up and running tempature then Desktop Dynos estimate of 595 HP @ 6,000 RPM and 589 ft/lbs @ 4,500 RPM are fairly close to what I might see on an engine dyno.
The Desktop Dynos power curve and peak power/torque are also simular to what was measured.

[dynorad]

cuda66273- I don't have any new insight into how to translate rwhp to flywheel HP. Currently I am using 15-20% for 4 speeds and 20-25% for automatics.
I have some data that would suggest that the drivetrain is more efficient than everyone thinks. For example, the efficiency of a 4 speed in high gear is over 97%. The efficiency of a differential is about the same. It doesn't add up very well.

If the transmission is using energy, it has to be turned into heat. The fact that trannys don't get super hot would suggest that maybe they don't take so much power. Automatics have coolers, but still there are some limits to how much can be dissipated.

Fortunately, I am concerned mainly with wheel HP and am not required to nail flywheel HP. I'm not sure I could be very accurate on that.

On your car your power may be somewhat less than the calculator because your car has less frontal area and thus less aerodynamic drag. This might allow you equivalent performance with 10-30 less HP. It makes building a small drag car pretty attractive.

At 70 MPH the 68 Cuda takes 8 less HP to push it through the air than a B-body. This effect gets larger with more speed.

[rumblefish360]

Fortunately, I am concerned mainly with wheel HP and am not required to nail flywheel HP.

The rear wheel HP was not the topic starter. Although, this is what we should be concerned about. I said we as in everyone here. Because that's what counts. The suspension is what will keep you from getting good readings when your at the track. A dyno that you put your car on is best. No time loss from poor suspenswion at the track.

Almost everyone has a lot less power than they think.

True. But I think my est. of a guess is a fairly decent one. Considering it's flywheel HP not rear wheel. It could very well be high. But then again, I'm not a dyno. Just taking a guess at it with what I learned over the years.
Just In your opinion, what do you think?

[dynorad]

Rumble- I don't think I can estimate your power any better than you can. There are way too many factors to make a prediction.
If you get it dyno tested you will know!

[72Challenger]

Cuda, like dynorad said there's the influence of aerodynamics at work. I have a formula for computing aerodynamic horsepower requirements for a given speed, but it requires knowing the coefficient of drag of the vehicle. It would be impossible to know this without wind tunnel testing. Sometimes the manufacturer will publish these numbers, but I've never been able to find them for the A body 'cuda. Besides, that big ol' hood scoop is sure to change your numbers anyway! BTW, is that a rearview mirror I see in the pic of the fish?? It's hard to tell in such a small image. If so, wonder how many thousandths you could trim off your time if you lost it?

Actually, the aero drag only becomes significant at high speeds. Since in most cars such a small percentage of total time is spent at these high speeds, the effects of aero changes would be very slight in a drag car compared to HP changes. The faster the trap speed of the car, the more important this becomes. My limited experience indicates that it's an imprtant factor in cars with trap speeds of 135 or more.

[cuda66273]

Yes that's a rear view....I'm losing it today.

Wind resistance on a 66 Cuda? the numbers don't go that high...but, if I could figure out a way to make it run backwards...now that would make it way quicker

Like I said earlier the only number you need to look at is the one beside the WIN on your time slip......and hope it's yours.

In our case we're searching for the elusive 11.99 time slip so we can run Super Pro at Division 6 races, that's the highest dial-in you can put on your windshield. So by doing these calcs we know we need to find another 25HP at the crank, remove another 200#s or make the car more areodynamic. The last two being the most difficult at this point.

That hood scoop may not be the most areodynamic thing but it jams huge air pressure into the carb making big power at the top end. The top of the air cleaner has 8- 2" holes cut in it and sits flush with the hood forcing cold fresh air directly into the carb. When we first installed it we used 3 very small machine type screws and small washers....first pass it ripped the bolts and washers right through the fiberglass! so I know the ram air works. Remember the 12.27....the hood and scoop took us to 12.18...I'll go with functional over pretty anyday.

[72Challenger]

I totally agree with you about function over form. I wasn't criticizing but just making a little fun.

I agree that adding power should be the easiest for you at this point. All you would need would be some big port heads. But that takes away one of the coolest things about your car - the fact you're running those numbers with 273 heads.

I ran calculations of your HP based upon both your ET and trap speed. Interesting results - ET calc says you have 352.76 HP to the ground, speed calc says 327.67. This means one of two things - either you're launching much harder than the factor used by the calculator, or your drag is less at the top end than the formulas' factor. Maybe a combination of both.

Getting the increase from aerodynamic changes alone would be impossible. The reason is because at 109 MPH you're likely losing less than 100 HP to drag. I don't have your CD*A (coefficient of drag * frontal area) so I'll use mine of 11.2. It works out to 98.9 HP. You've got a higher CD, but less frontal area, and any differences are minor to these calculations, since drag increases at the cube of the speed, and directly with CD*A. At 50 MPH, the drag is only worth 9.5 HP! At 75 MPH it's worth 32 HP. Even if you could drop 25 HP worth of drag at the very top end, most of the time of your run it would be far less. That's why I feel you shouldn't even waste your time with anything but the simplest aero changes unless your trap speeds are over 135 (at 135, the HP needed to overcome drag is 188 for my Challenger!)

Added power or reduced weight has it's effect over the entire run, so you're best bet lies there, as you are already aware. I think the brag factor of the small heads is way cool, so what's your budget for fiberglass parts?