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Started By
Message
re: Dyno question: drivetrain loss.
Posted on 9/24/14 at 9:13 pm to DownshiftAndFloorIt
Posted on 9/24/14 at 9:13 pm to DownshiftAndFloorIt
Wait, what?
1
Posted on 9/24/14 at 9:15 pm to VetteGuy
I read that wrong.
For some reason I thought 447 at the motor and 440 at the wheels was what you said it was.
Too late. Going to be.
For some reason I thought 447 at the motor and 440 at the wheels was what you said it was.
Too late. Going to be.
Posted on 9/24/14 at 9:15 pm to VetteGuy
I Dyno my old Firebird with the 400 block with turbo 350 transmission. It was about 320 hp at rear wheels. The motor was estimated to be 400hp.
This post was edited on 9/24/14 at 9:19 pm
Posted on 9/24/14 at 9:19 pm to VetteGuy
Depends, it's not a static number but it isn't as dynamic as a fixed percentage either. Depends on the dyno setup and who's putting their fingers on the scale too... 
I know a stock F-150 with the 9.75" axle loses about 60 - 65hp and that number is about 20% on a stock truck but that 20% wouldn't apply to a supercharged Lightning since it would see pretty much the same drivetrain loss.
I know a stock F-150 with the 9.75" axle loses about 60 - 65hp and that number is about 20% on a stock truck but that 20% wouldn't apply to a supercharged Lightning since it would see pretty much the same drivetrain loss.Posted on 9/24/14 at 9:19 pm to DownshiftAndFloorIt
Remember our fence thread? 
Posted on 9/24/14 at 9:32 pm to VetteGuy
quote:
Car is rated at 550, been measured at 447 at the rear wheels. Some speculated Jag was overstating HP.
Technically that 550 is 550PS not SAE Net which would be about 543hp. Without knowing the dyno setup, correction factors, and if anything was done to limit the ECU from trying to protect the catalytic converters or transmission it's hard to speculate on anything. Generally, supercharged engines are underrated by the manufacturer though.
Posted on 9/24/14 at 9:48 pm to Clames
Man, you know a ton of stuff.
I had a thunderbird SC back in the day and I really liked it. Very seamless, not at all like the turbo cars of that era.
I had a thunderbird SC back in the day and I really liked it. Very seamless, not at all like the turbo cars of that era.
Posted on 9/24/14 at 10:14 pm to VetteGuy
I'd like to have an old Turbo Coupe to mess with. Those 2.3T's can make some power and do it cheap. With modern EFI systems, turbos, and boost controllers you can do some crazy things now and still have a perfectly streetable car.
Posted on 9/24/14 at 10:15 pm to VetteGuy
That's a good bit of drivetrain loss. My mustang rated at 500 hp dyno'd 440 whp stock. But every drivetrain is different. My truck had a lot more loss due to heavier moving parts and more resistance through the transmission and driveshaft.
Posted on 9/25/14 at 9:32 am to tigers225
What kind of dyno? Inertia or eddy current, they will read differently with inertial dynos having a tendency to report higher rwhp numbers. Now that doesn't mean one is more or less accurate than the other.
Posted on 9/25/14 at 10:20 am to tigers225
quote:
That's a good bit of drivetrain loss.
Depends on the efficiency of the system. If there are a bunch of components that require the pulleys to work then the energy will be transferred to them as well. This is why different size pulleys will increase HP. So if a vehicle that has been stripped of A/C and other non necessities towards racing, the vehicle will have a higher transfer rate to the wheels. Driveshaft weight also has an effect towards RWHP. If it is heavy, it will require more to turn therefore decreasing the hp to the wheels.
Power = (Force*Displacement)/Time
So if it takes longer to get to the end, then less power. If the vehicle is shorter, it will have more to the wheels with the same system.
This post was edited on 9/25/14 at 10:31 am
Posted on 9/25/14 at 10:40 am to Hu_Flung_Pu
Mustang was on a dynojet (inertia) and the truck was on a load bearing dyno dynamics. I know the loaded dynos will read a lot lower, but im just saying that's a lot of drivetrain loss for a smaller car. I would be pissed.
This post was edited on 9/25/14 at 10:56 am
Posted on 9/25/14 at 10:58 am to tigers225
In reading the Jaguar boards, some of the owners are kinda surprised.
That said most of 'em aren't gonna track the cars or tune them, so it's not that big of a deal.
Plus, the dyno numbers are coming from a tuner that may have reason to under-state base HP.
I can't believe a manufacturer would cheat too much after the Ford fiasco of a few years ago.
That said most of 'em aren't gonna track the cars or tune them, so it's not that big of a deal.
Plus, the dyno numbers are coming from a tuner that may have reason to under-state base HP.
I can't believe a manufacturer would cheat too much after the Ford fiasco of a few years ago.
Posted on 9/25/14 at 11:52 am to tigers225
Like I said, unless you know if the ECU was pulling power because the catalytic converters were getting too hot or there is a torque management issue then there is very little that can be concluded with any certainty. It takes dozens of pulls by a competent dyno operator who is familiar with the car to establish a proper baseline with all the data properly recorded. That pretty much never happens since I've rarely seen oil temp, oil pressure, coolant temp, timing, injector duty cycle, IAT, MAF counts, etc overlayed on a dyno graph. My truck has an onboard datalogger that pulls all that info plus wideband O2.
Posted on 9/25/14 at 1:14 pm to VetteGuy
quote:
Thunderbird SC
I remember when Ford delayed introducing the SC because the engine was twisting driveshafts. I told a friend they should provide a free driveshaft with each purchase and promote the hell out of it.
Posted on 9/25/14 at 1:28 pm to Clames
You'd think it would all be fully automated and they would program corrections into the results by now. That would eliminate a bunch of error, but what do I know?
Posted on 9/25/14 at 1:36 pm to Hammertime
They are complicated machines for all that the priciples they run on are simple. I was looking at a few Dyno Dynamics single axle dynos a few years ago. Second hand they were about $36k and would have needed a lot of money to do all the routine maintenance that most shops don't do. Doesn't help that cars are so much more sensitive today and it makes it difficult to get reliable numbers out of them.
Posted on 9/25/14 at 1:54 pm to FightinTigersDammit
Man, that car ran great. The only issue I ever had was grenading the AC compressor at about 48K.
Posted on 9/25/14 at 5:02 pm to VetteGuy
quote:
Man, that car ran great
Can you imagine the sales if they put a free driveshaft in the trunk?
Posted on 9/25/14 at 5:42 pm to Clames
quote:
Clames
i do t know all the logistics of running something on a dyno, but they have to run it in a certain gear from what I was told? When I had my truck dynoed they said they my tire size affected the ability to do this (run it in the necessary gear). That make any sense to you?
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