Rwhp vs engine dyno

[metcoll]

From research my engine should have 500 to 520 flywheel hp..but when went on the dynojet I put down around 360 to the wheels..my combo is a 440, 2355 pistons,rpm heads ported flow282 @ 600,cam is a hydraulic 240/250 520/547 lift,rpm intake,850 dbl. pump carb,msd ignition and 13/4 headers going into 2.5 exhaust...as for the rest it is an auto with a 4200 stall and 4.56 gears...compression is 170-180 psi..my question is do you lose that much power through the drivetrain

[cdr]

air filter, exhaust, fan blade, water pump, alternator, power steering pump & THEN the drive train. most engine dyno's dont have these parasitic items hooked up while running them, there is NET HP at the flywheel & there is Gross HP at the Flywheel. a;so a REAL 500hp fywheel , is a badass street car. take it to the track & see what it runs.

[cdr]

lets say you are making 500 Gross BHP, take approx 60 hp off for the items I mentioned, could be more or less a lot depends on the type of muffler you have, 500-60=440, lets say 14% drive train loss, 440 x .86 = 378 rwhp Dyno Jet tends to read higher HP that a Mustang

[metallicareload99]

From research my engine should have 500 to 520 flywheel hp..but when went on the dynojet I put down around 360 to the wheels..my combo is a 440, 2355 pistons,rpm heads ported flow282 @ 600,cam is a hydraulic 240/250 520/547 lift,rpm intake,850 dbl. pump carb,msd ignition and 13/4 headers going into 2.5 exhaust...as for the rest it is an auto with a 4200 stall and 4.56 gears...compression is 170-180 psi..my question is do you lose that much power through the drivetrain

Your 440 is similar to mine and the fastest I went at the track last year was 106 mph.  According to the Moroso calculator and based on my weight I was making 375 HP or so

[BSB67]

....my question is do you lose that much power through the drivetrain

Probably not.  But I don't know if I would necessarily believe the 500-520, nor the 360.  And seriously, I would not get too wrapped up on either of them.  I also think that Charlie's explanation is pretty good too.   

If you're concerned about track performance, go to the track and start dialing-in the car.  If you are not interested in the track, and you're happy with the way it runs, I suggest you move on and enjoy the car.  You'll chase yourself in circles on this horsepower thing.

My gut feeling is that 360 RWHP will put down a pretty decent number at the track, although my limited experiences are with Mustang dynos.

[BSB67]

From research my engine should have 500 to 520 flywheel hp..but when went on the dynojet I put down around 360 to the wheels..my combo is a 440, 2355 pistons,rpm heads ported flow282 @ 600,cam is a hydraulic 240/250 520/547 lift,rpm intake,850 dbl. pump carb,msd ignition and 13/4 headers going into 2.5 exhaust...as for the rest it is an auto with a 4200 stall and 4.56 gears...compression is 170-180 psi..my question is do you lose that much power through the drivetrain

Your 440 is similar to mine and the fastest I went at the track last year was 106 mph.  According to the Moroso calculator and based on my weight I was making 375 HP or so

I do love the Moroso Calculator.  For me its what levels the playing field for comparison purposes.  You can also use Mopar's published "Dragstrip Dyno".  It does the same thing as the Moroso Calculator, but the results are a littler higher.  So if your looking to rationalize a higher hp, use the Mopar calculation. It also has a nice narrative that is educational. 

Despite popular belief, the Moroso calculator is not RWHP.  MPH is was you use for estimating hp (not et).  If you use the track mph, and race weight, the slide rule will give you a net, actual flywheel hp.  If you correct the mph to standard conditions, the slide rule will give you net corrected hp).  Then, as Charlie stated, the remaining difference between the a true dyno corrected gross flywheel hp and the corrected net hp will be the items Charlie stated above.The best you can do is estimate these.

My experience is if you start with a not to happy dyno, these numbers line up pretty well, and consistently.

[INTMD8]

.my question is do you lose that much power through the drivetrain

You can lose quite a bit with a loose converter. 

Look at the dyno run in mph instead of rpm, calculate what mph would be with no converter slip at peak rpm to figure out slip on the dyno.

Inefficient converter is converting power to heat vs putting it to the tires.

High numeric gears (such as yours) also contribute to inertial loss. (If you had a 2.73 for example you accelerate the mass at a slower rate)

Agreed on, bring it to the track and go from there.

[firefighter3931]

Chassis dyno is mainly a tuning tool, in my opinion. Good for dialing in the timing & fuel curves. The track will tell you how much power it's really making. All you need is the MPH and raceweight as mentioned above....then it's just math, pure and simple. 


Ron

[c00nhunterjoe]

Chassis dynos are good for chest pounding in my opinion, Which is why you are upset by the number. So i ask, what does that number actually mean to you for your car? What does it matter if it is higher or lower? The dyno and dyno operater can manipulate the readings from car to car. You may make 350 on 1, go to the next one and make 400. So who cares? Just my 2 cents. Take it to the track as others have stated, but dont forget to get the weather conditions at the time of your run to get your corrected numbers as well. If you do not have a weather station, here is a decent site to use.
https://airdensityonline.com/track-results/Cecil_County_Dragway/

[flyinlow]

Educate me please;

car A race weight 4250 with 400 Hp ,2.76 axle and a 727TF  goes   XXX mph in the traps

car B race weight 4250 with 400 HP, 4.10 axle and  ZF eight speed goes the same mph?

Is that simple of a calculator accurate.

[cdr]

Educate me please;

car A race weight 4250 with 400 Hp ,2.76 axle and a 727TF  goes   XXX mph in the traps

car B race weight 4250 with 400 HP, 4.10 axle and  ZF eight speed goes the same mph?

Is that simple of a calculator accurate.

They would be a couple of MPH within each other, but does the ZF use more or less HP, it would take testing to find out.

[c00nhunterjoe]

Educate me please;

car A race weight 4250 with 400 Hp ,2.76 axle and a 727TF  goes   XXX mph in the traps

car B race weight 4250 with 400 HP, 4.10 axle and  ZF eight speed goes the same mph?

Is that simple of a calculator accurate.

The 2.76 and 4.10 have no bearing on mph, only et, assuming the preloads on the bearings are the same but we are splitting hairs there. If the car with the zf has the same mph as the 727 car and the cars were run at the same track and same weather conditions, then the car with the 727 makes more hp as a stock 727 takes more hp to turn the zf.

[metcoll]

Has anyone here had there vehicle dynoed on a chassis dyno & engine dyno

[c00nhunterjoe]

If someone wants to pay for it, i will put mine on the rollers. Lol. I have engine sheets.

[flyinlow]

With out the transmission our Charger engines are just expensive battery chargers. It is hard to believe that the gear box has little to no effect on trap speed.

Lets say in the earlier example car A and car B engines both peak Hp. is at 5500rpm.

A CVT transmission would allow the engine to sit at 5500rpm for the whole run.  Best run ?

Lets say that car A has a manual Valve Body and you put the car in 3rd. (single speed trans, I have done this with the '70 Charger , is pretty lame performance below 80mph ) worst run ?

Car B's 8 speed lets it stay at peak (or very close to) rpm for most of the run.  pretty close to CVT transmission maybe better with a good converter.?


Just hanger flying here.

[BSB67]

In extreme cases like in your example, there would be some difference.  Probably less than you think.

There are actually two formula for for manual and automatic trannys.  But they are close. 

Changes in rotating mass and rolling resistance will make a difference too. 

These formula are empirically derived and represents best fit of a lot of data.

To me it is still better for comparative purposes.  Even knowing that the formula are not perfect, I would trust it far more than anyone posting a dyno sheet on a forum.

[BSB67]

Has anyone here had there vehicle dynoed on a chassis dyno & engine dyno

yes

[cdr]

In extreme cases like in your example, there would be some difference.  Probably less than you think.

There are actually two formula for for manual and automatic trannys.  But they are close. 

Changes in rotating mass and rolling resistance will make a difference too. 

These formula are empirically derived and represents best fit of a lot of data.

To me it is still better for comparative purposes.  Even knowing that the formula are not perfect, I would trust it far more than anyone posting a dyno sheet on a forum.

This ^^^^^^^^^^, I have seen many 700hp Dyno sheet cars that run at the track like a 550hp engine.

[c00nhunterjoe]

In extreme cases like in your example, there would be some difference.  Probably less than you think.

There are actually two formula for for manual and automatic trannys.  But they are close. 

Changes in rotating mass and rolling resistance will make a difference too. 

These formula are empirically derived and represents best fit of a lot of data.

To me it is still better for comparative purposes.  Even knowing that the formula are not perfect, I would trust it far more than anyone posting a dyno sheet on a forum.

This ^^^^^^^^^^, I have seen many 700hp Dyno sheet cars that run at the track like a 550hp engine.

And the reverse- i can give you a 580hp dyno sheet that puts a 69 b body into the 9s....at stock weight.

[INTMD8]

With out the transmission our Charger engines are just expensive battery chargers. It is hard to believe that the gear box has little to no effect on trap speed.

Lets say in the earlier example car A and car B engines both peak Hp. is at 5500rpm.

A CVT transmission would allow the engine to sit at 5500rpm for the whole run.  Best run ?

Lets say that car A has a manual Valve Body and you put the car in 3rd. (single speed trans, I have done this with the '70 Charger , is pretty lame performance below 80mph ) worst run ?

Car B's 8 speed lets it stay at peak (or very close to) rpm for most of the run.  pretty close to CVT transmission maybe better with a good converter.?


Just hanger flying here.

Yes it makes a big difference.  Gearing to maximize your ability to keep the engine at/around peak HP maximizes rear wheel torque at any speed. 

So final drive, how many gears and if auto, the torque converter all comes into play to achieve this.

As your example, you can see how many cars with similar engine horsepower are much quicker/faster in the quarter when they moved to 6 then 8 and 10 speed transmissions.

The lack of ratios in older transmissions can in some part be overcome by a loose converter but now you are converting some more power to heat rather than making it's way to the tires.

As to the question of, has anyone ran their engine on an engine dyno vs a chassis dyno, the answer is yes and still would vary on a case by case basis as the power loss would be different from car to car unless they were all using the exact same components from the flywheel back.

[BSB67]

Yes it makes a big difference.  Gearing to maximize your ability to keep the engine at/around peak HP maximizes rear wheel torque at any speed. 

So final drive, how many gears and if auto, the torque converter all comes into play to achieve this.

As your example, you can see how many cars with similar engine horsepower are much quicker/faster in the quarter when they moved to 6 then 8 and 10 speed transmissions.

The lack of ratios in older transmissions can in some part be overcome by a loose converter but now you are converting some more power to heat rather than making it's way to the tires.

As to the question of, has anyone ran their engine on an engine dyno vs a chassis dyno, the answer is yes and still would vary on a case by case basis as the power loss would be different from car to car unless they were all using the exact same components from the flywheel back.

What are you calling a big difference?  Do you have some data or examples to show this big difference?   How does this wash with the popularity of the powerglide?

How does max horsepower maximize torque?  What does maximum torque maximize?

I'm not saying that minimize the engine rpm around the peak power doesn't have some benefit, but your statements seem a bit arbitrary.

[BSB67]

With out the transmission our Charger engines are just expensive battery chargers. It is hard to believe that the gear box has little to no effect on trap speed.

Lets say in the earlier example car A and car B engines both peak Hp. is at 5500rpm.

A CVT transmission would allow the engine to sit at 5500rpm for the whole run.  Best run ?

Lets say that car A has a manual Valve Body and you put the car in 3rd. (single speed trans, I have done this with the '70 Charger , is pretty lame performance below 80mph ) worst run ?

Car B's 8 speed lets it stay at peak (or very close to) rpm for most of the run.  pretty close to CVT transmission maybe better with a good converter.?


Just hanger flying here.

If you have a car start is second gear verses 1st (manual valve body), it will mph about the same.  If you have a car with a 4.10, and switch to a 3.23, it will mph the same.  If you have a run where the tires break loose and you have a 3.5 sec 60 ft time verses a normal 1.8 60 ft time, the mph will be the same.

[INTMD8]

Allow me to repeat myself.

Keeping the engine at/near peak horsepower maximizes -wheel- torque which maximizes acceleration.  

Once again, this can be achieved with many gears, or a loose converter and less gears. (except loose converter loses efficiency to heat).

See a lot of powerglide cars with a stock torque converter run well?  

Do you see what the new 8 and 10 speed auto cars run compared to the old 2/3/4 speed autos with similar power to weight ratio.

I have no problem explaining this in depth but not going to waste my time if you want to dismiss it as arbitrary without trying to understand what is being said.

[cdr]

Allow me to repeat myself.

Keeping the engine at/near peak horsepower maximizes -wheel- torque which maximizes acceleration.  

Once again, this can be achieved with many gears, or a loose converter and less gears. (except loose converter loses efficiency to heat).

See a lot of powerglide cars with a stock torque converter run well?  

Do you see what the new 8 and 10 speed auto cars run compared to the old 2/3/4 speed autos with similar power to weight ratio.

I have no problem explaining this in depth but not going to waste my time if you want to dismiss it as arbitrary without trying to understand what is being said.

Hellcat with a 8 speed runs just what it should for the HP the engine makes, no reason to be an ASSHOLE

[cdr]

An 8 speed trans has 7 shifts, each shift takes time to make the shift, a power glide has one shift that takes time to shift, easy math. between each shift the car slows down & then picks back up. yes the time is in milliseconds but they add up over 7 shifts