Thread: Drivetrain loss for dummies!!!!

You may be closer to the actual numbers, maybe. But you will still be way off. Did you miss the part where I said sheering strength of the lubricants goes up when encountering more power? This is the exact reason cars with high power need transmission and differential fluid coolers.

No i didnt miss that. But its not gonna suck up that much extra power.

In a world of cars ranging from 140hp to 300hp you can be fairly accurate with the percentage just as you can by taking its factory loses and going from there.

But when someone tries to tell me that a car making 800whp must be making 970hp at the crank is aboslutely 100% rediculous to say the least.

I had a guy confirm this with me on another forum. He built and tuned a dragster engine on an engine dyno to the tune of just at 1000 crank hp, put it in a chassis with an automatic trans and such and dynod 960 hp at the rear wheels. So what does that tell you for the % factor. Its gone and out the window, haha. Your only gonna lose soo much power through the drivetrain. Again little things that will affect it slightly but not that much. This is where using a set number loss for that drivetrain will give you a much more accurate number.

Just about as ridiculous as saying it makes 835 HP at the crank. *shrug*

Okay I take it back. That's the exact data we're all looking for. If that's accurate, than I'll have to agree with you.

i agree, when you get into dynos and turbos and na and tuning and numbers, there are many variables that need to be taken into consideration to be 100% accurate

I'm going to start this with a disclaimer. Please do not take this as an attack, as I mean it in no such way.
From what I've gathered you take numbers spouted off by others, and publications at face value, then apply your "rule" to it, since that has what has proven to be true in your experience. I can tell you from MY experience, which is alot of real world data, that you are uninformed at best. And it seems that BenFenner has a clue as to whats up as well. If you are willing to BLINDLY follow what someone on another forum preaches to you, how and why are you challenging everything that is told to you by other people with tons of experience. I'm no bench racer, and I have alot of experience telling me otherwise as far as your theory.
There is absolutely NO way that any engine putting down EXACTLY 1000 chp will put down 960 to the wheels. Unless the wrong correction factors were used on top of using something like a dynojet. But given your seemingly limited experiece you never thought of varying factors, such as correction values, the type of dyno used, the intended capacities of that dyno. On top of that EVERY dyno will read differently. If you don't use the SAME dyno with the SAME correction factors plugged in, similar weather for before and after tuning, you are nothing more than a dyno queen racer, like the Supra guys. Chasing a number.
The numbers published in magazines and other literature are that, just numbers. Something to throw out to give you an idea. That goes for manufacturer numbers as well. Take them with a large grain of salt. False claims, and exaggerations lead to numbers that are nothing more than a ball park figure. (remember when the RX8 came out, and they actually would buy back the car if not satisfied with performance b/c of false power claims??? It was rated at like 250 or so, but never saw above 160 to the wheels.) This goes for magazines, builders, etc.... Take what you hear with a grain of salt, not at face value that IT MUST BE what they claim. Unless you know the person in question, and their abilities there is a chance that they may not be fully capable of operating the equipment correctly, which will lead to skewed results.
Go out and get a lot more REAL experience. Stop taking everything you read and see for %100 truth. I know that you do have some experience, and I see by your sig you've done some things. I may not have the level of build you do, but I have a lot of tuning experience, and dyno time (all types of chassis, and engine dynos). I've had a large part building numerous bad ass engines, the most notable was a 2005 Engine Masters Challenge motor. Because of throwing the harmonic balancer we had to run it in the competition with no tuning. Our tuning time was spent replacing the balancer instead of re jetting the carb. Google it. I've since had a falling out with a few of the guys and wont post it. The owner's son that started the project got his nose in some dope, and another guy had a social interaction problem. I still talk to a few of the guys, and still work with them and others on some other projects. One of which should be protoyped in the next year will BLOW your mind
Please do not take this as any type of attack. I am sure you are capable, just with limited resources. Get friendly with some people that are really smart, and have access to equipment. You'll look back and wonder what took you so long.

tl:dr: only way to know is to dyno it yourself. There's no 'magic formula'.

No, well said other than the fact my eyes hurt from trying to read that huge paragraph and not get lost or skip a line. lol

I do remember when the rx8 came out with the rediculous claims of 250hp. But you see when you are dynoing only 160rwhp you know those numbers are off becaue again there is no way its losing 90hp through the drivetrain. Although i worked as a Mazda technician for a year and did sooo much work on rx8's its not even funny including about 5 ecu recalls in that one year time period.

I can tell you this, the automatic rx8's were absolutely butt slow compared to the manual ones. This can only be justified by the automatic trans and torque converter absolutely sucking away power from that already weak motor as it is. I mean its a night and day difference. Its like there are 3-4 ac compressors kicked on difference. lol. It was that bad.

I can see differences like that and get what your saying. But the info provided to me was by an experienced engine builder and tuner. Not just some joe shmo. I understand that a lot of variables can take affect. But again to say a vehicle at 1000 crank hp is gonna lose almost 200hp just getting that power to the wheels is rediculous whether it be rwd, fwd, or awd. It will be slight differences between all three drivetrains but again your just not going to lose that much.

All im saying is the % goes down as your power gets higher. Its not going to stay true. And numbers have shown this.

keelay have you ever seen data from an engine on an engine dyno and then later seen the output as measured by a chassis dyno (with no other variables changed)? I'd love to hear about your data if you have any.

As for Ashton, he's a smart guy. I don't think you've given him enough credit. I'd have thought the same thing if I'd seen the data he's seen (assuming the dynos are known quantities). So far that's the only real world info I have to go on as well unless you have some.

That is right. It is a proportional loss. But your original post sounded like you were trying to say "x" powertrain takes "x" power to spin it, and after that it's all static.
As far as the RX8's I'm sure that they do like most vehicles. The automatics are targeted towards people not really performance minded, and they do not have as aggressive tune as their manual tranny counter part. Also look at the engine. A rotary is no torque monster, and an auto is going to exacerbate this problem 10 fold. The manual, you can launch higher, and keep it in the powerband a little easier. I would also be willing to bet that the manual equipped cars also have, at least an option, for a numerically higher (shorter) diff gearing, which will help keep it in the power band also. More factors than the obvious transmission differences affect perfomance. The weight of the tranny, the parasitic torque convertor, taller rear gears, and more economical tune all make the auto equipped significantly slower. This goes for *most* cars on the road. This difference can even get into different mufflers between the 2 (new edge mustangs, and sn95's have slightly louder mufflers on the manuals), chassis reinforcements, tunes, gearing, and lots of other stuff you would probably never even think about.

I don't know much on this subject but, my good buddy with a 4g63 made 1100hp at the crank on an engine dyno, then made 810hp at the wheels. The car is a 70's monza with a powerglide and 6000rpm stall. He ran the same boost, but had to change the tune a bit from engine dyno to chassis dyno.

This is on instance where he was hoping for much better whp. He is taking it to the track tonight to hopefully run some mid to low 9's.