good point.

however....id be willing to wager that the change in friction is not equal to a fixed percentage of flywheel horsepower.

if you double your engine power, does the friction of transmission components also double.....or does it just increase slightly?

 

I think that drivetrain inertial losses are greater with higher power levels. That is, DynoJet style inertial dynos will register more of a loss at higher power levels.

DynoJet style dynos calculate hp by measuring the amount of time it takes for your car's drivetrain to accelerate the large, heavy roller. Keep in mind that your car's drivetrain (rear axle, wheels, driveshaft, transmission, even internal engine parts) are mass that has to be accelerated also. The quicker you accelerate the Dynojet roller, the more energy you are putting into accelerating the drivetrain of the car.

This phenomenon can be seen when dyno'ing a car in different gears. One of my old combinations dyno'd 250 rwhp in 1st gear, 310 rwhp in 2nd gear, and 350 rwhp in drive. The engine itself made the nearly the same flywheel hp on all the runs, but alot of this energy is put into accelerating the mass of the drivetrain in lower gears, not the roller.

To further explain my point, when you put the car in neutral and floor it, 100% of its power goes towards accelerating the mass of the crankshaft, rods, etc. The lower the gear you're in, the more pronounced this effect is.

So, a car that makes 600 rwhp accelerates the dyno twice as fast as one that makes 300 rwhp. So, energy required to accelerate the drivetrain doubles.

Note that this does not take into account friction because I think that is a small part of the loss. That is, of course, if you don't have an automatic with a non lock-up converter, which poses a loss of around 4 - 10% extra.

Mike

 

I saw this in real life your car = drool

you can feel free to put it on mine haha my lt1 is already pretty strong

 

engineermike: one thing to say to you STFU I saw this in real life saturday when I was dynoing my car, its real so go read some more books mr engineer

 

Why is this so hard to believe? Granted the power at 7 psi is alot, but it hovers around 20 hp /lb of boost. If hondas can meet and exceed that, then why not an LT1? A friend here in town has an Integra GSR with a DRAG turbo kit and it made 337 WHP at 9 psi. That is roughly 20hp/lb of boost. Everyone claims b.s., but the boost gauge AND the datalogger report the same. Lets say turbospeeds gauge is off by 1 psi, so instead of running 7 psi it was making 8 when it dyno'd 462. His car made 263 RWHP stock, so if we chuck the restrictive manifolds and it had say LT headers, it would make in the neighborhood of 300 - 310 RWHP. My car dyno'd 260 bone stock and 300 with a K&N and LTs, so thats not far off. 462 - 310 = 152 whp from 7 psi. That is 21hp/lb of boost. Lets say the gauge was off by 1 psi, and you are down to 19. With a very efficient manifold design, that would be possible. Has any other turbo car guys dyno'd directly before and after to see how much hp/lb of boost gain there is?

 

Interesting dyno results, How did you spray the N20 on the intercooler, just held the bottle up close and opened 'er up? How much did you spray? I am going to try something like this (maybe Intmd8 and I can collaborate) but I want to use C02.

Your injectors look undersized, I'd go bigger otherwise they will be running at 100%+ duty cycle.

Base FP on an LT1 is like 43, in an LS1 where the base FP is 58, those 30's would be like 36's, but I'd be looking at running 42's honestly.

 

I dont think the power is in question... Its whats holding up that power...

I made 555 with just 8psi... So you tell me..

 

For the nitrous, we just held it up and cracked open the bottle. This session wasn't for proof of concept of my kit, it was just for the hell of it. I've already got a spray bar designed for his Cobra and I might try one on mine later. C02 would be the gas of choice because it is colder and more importantly, less expensive.

Concerning fuel, I run a rising rate fuel pressure regulator. While I don't know the exact fuel pressure, I would estimate it above 80psi at 8lbs. When I dynoed in St Louis there was a period between about 3800 and 5400 when it was so rich, it went below the sniffers 10:1 range.

I told you what's holding the power. It's an internally stock LT1 in a 1997 Camaro Z28.

 

Zac2003, I'm tired of re-typing the same information because people misunderstand it, so I'll just quote myself:

so you said. . .

 

I cannot believe I read this whole stinkin' post when I should be working! Clearly, we have some super smart people here debating, and I am learning a lot just by sitting back and digesting everything. Thanks to all the guys calling each other names, as it makes learning all the more fun

 

Let me shed some light on this for you guys.

When you make a run at your local dyno it corrects your raw numbers into one of a bunch of different formats. (unless you tell it not to) STD, SAE, etc... it doesn't really matter for my point.

Now say you are making a dyno run when it is 100º F outside you will get a raw number which the dyno will add power to in order to compensate for the heat. Say it adds +15HP, theoretically the total will be what your car should make at whatever the testing standard temperatures/pressures are. Likewise if you take the test with actual temps below the standard is subtracts power.

Now if you artificially change the parameters at your car and not at the sensors at the dyno you are "cheating" the numbers plain and simple.

Here is how it works...It's 100º outside and I take my car to the dyno. It makes 300 actual HP, when corrected to SAE it gives me +20HP...so my total is 320HP for normal conditions. All good right? Well on my next run I spray some N20 on my intake before my run. The engine is now ingesting 50º air instead of 100º air giving me more power. I now get 335HP actual. If the dyno knew the car was taking in that temp of air it would subtract out (-15) HP and give me 320HP which is where I am supposed to be, but instead it adds MORE power because it thinks I'm running 100º air. Now my SAE numbers say 355HP.

So now you are adding artificial power via unrealistic intake temps and adding a correction factor on top of that! The above example only really made 300HP but now I get to tote some nice 355HP dyno sheets. Plus the correction factors of STD are even more extreme than the SAE standards. I'm not even getting into altitude and humidity.

SAE standards are (77ºF)(29.235"Hg)(0 ft alt)(0% humidity)
STD standards are (60ºF)(29.92" Hg)

So, take other people's Dyno numbers (especially FI cars that benefit even more from "tricks") with a grain of salt please because a lot of people do this. Remember, you don't get that free HP on the street. This is a major reason people get confused with comparing track times to dyno numbers...and dyno to dyno numbers of different cars etc...

 

So, it would be impossible to rig up a nitrous jet that would spray the heat exchanger while going down the track? How is that artifical power? If you take your car to the track and it runs a 12.0 and then you spray the heat exchanger with nitrous and it runs a 11.5, then you picked up real horsepower. By your description, you would take a new cobra, put in the info that it is getting 15 lbs of boost, and subtract 15hp/lb from the numbers to get the "true" hp. ???

 

You missed my point. I'm talking about Dyno numbers, where people are getting the beneift of SAE and STD correction factors when there should be none. It's "artificial" because you are operating at parameters not taken into account by the dyno software. I didn't say there wasn't a real performance gain, I explained just the opposite actually. (see actual numbers) What I was showing is how these numbers get inflated on the dyno.

 

I can see what you are talking about for std versus sae, but my car actually made MORE power with STD than with SAE. Also, when you say this

and this

Its directly related to what I said, and has nothing at all to do with correction factors. Correction factors are the closest thing there is to making numbers comparative. If I dyno my supercharged car on a 10* day, and you do yours on a 100* day, and they both make the same exact power and torque, across the board, and then we race on an 60* day, and the cars weigh the same, and so do we, its pretty much a given that my car will make LESS that day and yours will make MORE, and your car will be faster.

 

I'll try to explain it better.


Assume the same exact car.


I Dyno on a 10º day

Actual Power 400RWHP
SAE Power 350RWHP

The dyno subtracts power because it's estimating the power you would have at 77º

I Dyno on a 100º day

Actual Power 300RWHP
SAE Power 350RWHP

This time the dyno adds power to get me my estimated power at 77º

Now lets do the same with N20 sprayed on my intercooler,turbo,intake pipe/manifold...ice bags etc...

Dyno at 10º

Actual Power 400RWHP
SAE Power 350RWHP

I'll assume the N20 didn't do anything because it's already cold out and the N20 didn't lower my intake temps. So numbers are the same as the first example. (again power is taken away like above)

Dyno at 100º

Actual Power 400RWHP
SAE Power 450RWHP

Do you see how the dyno added power assuming my intake temps were at 100º? The REAL gains of N20/ice on a 100º day are shown through my ACTUAL numbers before correction not after.

Now look at my SAE numbers from the n20/ice 10º day and 100º day...this is what I am talking about. It's the same exact car, it should always make the same power. SAE is supposed to correct for different weather/elevation, but if I dyno w/ "prep" on a cold day SAE takes power away...If I "prep" on a HOT day I get the benefit of a cold day (that gets taken out on a cold day run) PLUS another bonus for the hot weather. You only get actual power at the track no matter what you do.

Does that help?