Time to go Stage II!
- Thread starter Alky V6
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Like I posted in the other thread, with all your number juggling you should be my accountant. The rwhp numbers produced by that calculator are very, very close to the real world dyno numbers I see,. Not by adding any %, etc.. So lets just go with the fact that your engine isn't THAT SPECIAL that it defies normal physics and is making close to 857 rear wheel hp (of course, we wouldn't have to make any assumptions, if you would have put it on a dyno like I mentioned a long, long time ago in a thread far, far away). You are assuming over 30% drivetrain loss to get to 5 bhp/cid. I can only imagine what the 5 "plus" is that you tell your buddies. I'm pretty sure you have gradually lowered this value, wasn't your original "guestimate" something like 5.69bhp/cid? I'm too lazy to go back and review the thread where we discussed that.
Either way, your new engine according to you, should produce an easy extra 400hp. Using your calculations that should get you 1500+ hp. I can see why your pushing the 30% slip now, it will certainly help you get the bhp numbers you want out of the new combination.
Either way, your new engine according to you, should produce an easy extra 400hp. Using your calculations that should get you 1500+ hp. I can see why your pushing the 30% slip now, it will certainly help you get the bhp numbers you want out of the new combination.
Cal, is there something about the simple math that I just layed out that you don't understand? Where did you get 30% drivetrain losses and then 30% TC slippage?
You do understand that I used the figures that you, Gene, lazaris, and Tony gave to me, right?
Where the heck did you pull 30% out of anywhere?
Would you like a more detailed explanation of the equations I posted up in the last half dozen posts or so?
If you look them over more carefully, you'll see that it's all just very simple math. Nothing that you would need the advice of a CPA to understand.
What do you think, lazaris? Do you see any funny math going on here?
Anyone else out there see any funny math going on here?
If anyone sees any problem with my math, I'm certainly eager to learn what it is.
Cal, are you saying that Gene (12 hp) and Tony (5%) are completely wrong in saying that the calculator that you use might be slightly off? Are you saying that the calculator is absolutely perfect?
Let's assume that the calculator is absolutely perfect.
857 rwhp is the answer that your calculator comes up with for my car.
Again, let's assume 22% powertrain losses with my car. 22%. Not 30%.
1.00 - .22 (that's 22%) = .78
We're going to use the above .78 in our equation.
857 rwhp divided by .78 = 1098 bhp.
1098 bhp divided by 224 cid (cubic inch displacement of my engine) = 4.90 brake (flywheel) horsepower per cubic inch.
Now you can jump up and down and scream, "See! See! It's not 5! It's 4.9! 4.9 is not a 5! See!"
Good grief.
Let's assume that the calculator is absolutely perfect.
857 rwhp is the answer that your calculator comes up with for my car.
Again, let's assume 22% powertrain losses with my car. 22%. Not 30%.
1.00 - .22 (that's 22%) = .78
We're going to use the above .78 in our equation.
857 rwhp divided by .78 = 1098 bhp.
1098 bhp divided by 224 cid (cubic inch displacement of my engine) = 4.90 brake (flywheel) horsepower per cubic inch.
Now you can jump up and down and scream, "See! See! It's not 5! It's 4.9! 4.9 is not a 5! See!"
Good grief.If you wanted to use 30% in the above calculations to account for 30% drivetrain losses, you would take 1.00, subtract .30 from the 1.00 to give you .70 to use in the above equations.
.70 = 30% drivetrain losses
.75 = 25% drivetrain losses
.78 = 22% drivetrain losses
.80 = 20% drivetrain losses
.85 = 15% drivetrain losses
.90 = 10% drivetrain losses
.95 = 5% drivetrain losses
1.00 = 0% drivetrain losses
.70 = 30% drivetrain losses
.75 = 25% drivetrain losses
.78 = 22% drivetrain losses
.80 = 20% drivetrain losses
.85 = 15% drivetrain losses
.90 = 10% drivetrain losses
.95 = 5% drivetrain losses
1.00 = 0% drivetrain losses
Let's check this funny math.
20% of 2000 = 400
400 signifies 20% powertrain losses for a 2000 bhp car.
2000 - 400 = 1600
1600 signifies the horspower that the car makes at the rear wheels after subtracting drivetrain losses.
1.00 - .20 = .80
I don't know what the mathematical term is for what I just did above. I just know it works. I do it all the time with my books. Consult your accountant for a better explanation.
1600 / .80 = 2000
We just added back in our estimated 20% drivetrain losses.
It works!
If the above example wasn't simple enough, try using 10 for the bhp figure.
10% of 10 is 1.
10 - 1 = 9
1.00 - .1 = .9
9 / .9 = 10
Now we're all experts at adding drivetrain losses back into our rwhp number.
20% of 2000 = 400
400 signifies 20% powertrain losses for a 2000 bhp car.
2000 - 400 = 1600
1600 signifies the horspower that the car makes at the rear wheels after subtracting drivetrain losses.
1.00 - .20 = .80
I don't know what the mathematical term is for what I just did above. I just know it works. I do it all the time with my books. Consult your accountant for a better explanation.
1600 / .80 = 2000
We just added back in our estimated 20% drivetrain losses.
It works!
If the above example wasn't simple enough, try using 10 for the bhp figure.
10% of 10 is 1.
10 - 1 = 9
1.00 - .1 = .9
9 / .9 = 10
Now we're all experts at adding drivetrain losses back into our rwhp number.
I feel that the drivetrain losses figure that lazaris gave us of 15-22% is very fair.
The better the torque converter couples, the less heat that is generated inside the torque converter, the more efficient the torque converter is. That would place the drivetrain loss percentage closer to the minimum 15% in lazaris' range example.
The more slippage you have with a torque converter, the more heat that is generated inside the torque converter and the less efficient the torque converter is. That would place the drivetrain loss percentage closer to the 22% in lazaris' range example.
The heat generated in a torque converter is directly related to the amount of horsepower that is lost in the torque converter. Think of it as horsepower, that should be going to the rear wheels, being converted to heat and being lost.
It's the same as the hp lost through the cooling system in the form of heat, and the hp lost through the exhaust system in the form of heat, and the amount of hp that's lost due to internal component friction in the form of heat.
When you run a turbocharger compressor in an inefficient range, what happens? It heats up the air. If you can run a turbocharger in a more efficient range, you're able to get away with heating the intake air less.
The same goes with a torque converter. Run a more efficient torque converter and you heat the fluid inside the torque converter less. Less heat is generated. Less hp is lost.
The better the torque converter couples, the less heat that is generated inside the torque converter, the more efficient the torque converter is. That would place the drivetrain loss percentage closer to the minimum 15% in lazaris' range example.
The more slippage you have with a torque converter, the more heat that is generated inside the torque converter and the less efficient the torque converter is. That would place the drivetrain loss percentage closer to the 22% in lazaris' range example.
The heat generated in a torque converter is directly related to the amount of horsepower that is lost in the torque converter. Think of it as horsepower, that should be going to the rear wheels, being converted to heat and being lost.
It's the same as the hp lost through the cooling system in the form of heat, and the hp lost through the exhaust system in the form of heat, and the amount of hp that's lost due to internal component friction in the form of heat.
When you run a turbocharger compressor in an inefficient range, what happens? It heats up the air. If you can run a turbocharger in a more efficient range, you're able to get away with heating the intake air less.
The same goes with a torque converter. Run a more efficient torque converter and you heat the fluid inside the torque converter less. Less heat is generated. Less hp is lost.
For those running an efficient PTC torque converter, with extremely low slippage numbers on the top end, you would figure that your overall drivetrain losses are less than a torque converter that has higher TC slip numbers, so you would use a drivetrain losses percentage figure that is closer to the minimum 15%.
This is exactly why Dusty stated that he builds very tight torque converters for the fellas that engage in dyno challenges. A tight torque converter on the dyno will give you higher RWHP figures. Less bhp is being lost through the torque converter in the form of slippage and heat.
And as Dusty eluded to, running the same tight TC may work fine on the dyno to get that higher rwhp number, but might be a disaster on the track, depending on your combination.
This is exactly why Dusty stated that he builds very tight torque converters for the fellas that engage in dyno challenges. A tight torque converter on the dyno will give you higher RWHP figures. Less bhp is being lost through the torque converter in the form of slippage and heat.
And as Dusty eluded to, running the same tight TC may work fine on the dyno to get that higher rwhp number, but might be a disaster on the track, depending on your combination.
Tuners dont really care what the drivetrain loss is anyway. If there is a glaring problem with the converter it needs to be addressed. The tuner can't tune it out but will point it out right away. If you were to look at the road horsepower you will see why these cars are hauling ass with these seemingly low rwhp numbers. Once the converter flashes the engine is sitting within 5% or closer to peak power rpm the rest of the pass. 3% extra slip on a 170mph pass could be huge if the turbo was running outbid steam the last 100ft. It could be 4mph. The converters are letting us extract the most out of these engines. 10 years ago it was hit or miss. A lot less missing these days. Whp is whats available to get you down the quarter. If it's lost in the drivetrain then it's not available for getting you down the quarter. If I had over 15% loss I'd be figuring out why.
My PTC numbers are 1.12 in 60ft leaving at 4800 rpm and 20# boost with 7550 rpm at the crank and 7150 rpm drive shaft speed through the traps and 1050 RWHP on the dyno if you want to compare notes..
Not really a disaster and still fair dyno numbers
Not really a disaster and still fair dyno numbersWhere flywheel horsepower (bhp) numbers become important is when figuring out your BSFC. The amount of horspower you're generating related to the amount of fuel you are consuming. That's when it becomes helpful to be able to add back in powertrain losses when you have only a rwhp number to work with.
The BSFC number is helpful in determining how efficiently you are converting a certain amount of fuel to horsepower. I suppose you could use rwhp to calculate that, but that's not really a very accurate way of doing that.
If you don't mind, let's study your case.My PTC numbers are 1.12 in 60ft leaving at 4800 rpm and 20# boost with 7550 rpm at the crank and 7150 rpm drive shaft speed through the traps and 1050 RWHP on the dyno if you want to compare notes..
What is the weight of your car?
What is your max redline rpm? And what rpm do you generally see power really beginning to fall off?
Your TC slip appears to be 5.3% at the finish line. That appears to be pretty tight. That will mean that your drivetrain losses percentage is going to run closer to the 15% end of the scale, which means the difference between your rwhp figure and your bhp figure is going to be less.
With a more efficient torque converter, more of your flywheel horsepower that is being generated is making it through the torque converter and finding its way to the ground through the driving wheels.
With a less efficient torque converter (more slippage), less of the generated flywheel horsepower is making it through the torque converter, with more hp being lost in the form of slippage and heat. In this case, you have a larger difference between the rwhp figure and the brake (flywheel) horsepower figure because more hp got eaten up by the torque converter. Hence the different levels of drivetrain losses due to the differing levels of slippage and efficiencies between different configurations of torque converters.
Im just posting FACTS
Dusty Bradford
Well-Known Member
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- May 24, 2001
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What makes it interesting is when you go from 4% slip to 8% slip and you see the mph stay the same but et improves .06. Hmmmmm. Theoretically more power lost but the car runs quicker.
Its not just torque converter slip %. Drive train losses through the rear end, the trans, the engine all play a part and the more power/RPM you make, those frictional losses increase. There will be more frictional drive train loss in a car with a 80mm turbo opposed to a 44 mm turbo in the same car as an example.
Wow! I guess I missed a lot today. Slow morning at the shop, Donny? You missed the point of my post. Much like your SIM, I can juggle the numbers however I want. I could say your making 857 rwhp and the engine is making 30% more 857 X 1.3=1114hp OR I could say that the calculator is actually off 5% the other way rather than only running the variables only in one direction. I just wanted to make sure 5+bhp/cid is your bottom line I seem to recall that number gradually decreasing. I did have a couple questions before I step out:
Are you expecting over 1200 rwhp with new combination?
Are you changing the convertor or are you hoping the extra rpm's will help it couple better with the extra 400hp it will be seeing?
Why are you willing to take the new combination to the dyno when you were so against taking the old one, especially as hard as we tried to convince you of the benefits of going?
I seem to recall that number gradually decreasing. I did have a couple questions before I step out:Are you expecting over 1200 rwhp with new combination?
Are you changing the convertor or are you hoping the extra rpm's will help it couple better with the extra 400hp it will be seeing?
Why are you willing to take the new combination to the dyno when you were so against taking the old one, especially as hard as we tried to convince you of the benefits of going?
[quote="HighPSI,
Are you expecting over 1200 rwhp with new combination?
[/quote]
X2
When and if you do this and make it live then i will believe your a super tuner and you will get my respect. I would never challenge your ability as a tuner again
Are you expecting over 1200 rwhp with new combination?
[/quote]
X2
When and if you do this and make it live then i will believe your a super tuner and you will get my respect. I would never challenge your ability as a tuner again
You have more experience on this than I do, but I would guess that has to do with what we discussed earlier about keeping a particular engine in its powerband through the shifts?
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