Drive Train Loss - What %

I am setting up an application on my Iphone that will measure and record performance metrics for the speedster. In order to "dial in" the settings I need to know the weight of my car, and the % of drive train loss from the engine to the wheel. The weight I can handle. I read that +/- 20% is fairly accurate for most vehicles. Our cars are not most vehicles. Is this a simple answer, and if so... whats the percentage?

Here is a link to the program Ive uploaded, oh how I love my Iphone/construction calculator/spanish translator/mp3 player/weather channel/tv guide/mobile bank/photo album/GPS and now portable dyno.

http://www.dynolicious.com/index.php

Paul

A little research and voila:

These are the numbers that I have come up with over the years:
Type 1 S/A 12%
Type 1 IRS 12.5%
Type 2 with 002 gears 13.5%
Type 2 with 091 gears 14%
Mendeola 15%

My flywheel engine number 325 H/P - 13.5% = 281 wheel H/P

Paul - Are you sure about that 325hp number? Most of these engines - even the souped up ones - are well under 200hp. Mine is about 125hp, and is quite quick. Even Jake Raby's super hot engines are well under 300hp if normally aspirated. To get a number like that you'd at least need a turbo, and probably a whole lot of other stuff.

Pretty sure The number is accurate. His Nickname on thesamba is 'turbobob'. Think that helps to answer your question on whether or not the engine posting those numbers would have a turbo.

This is the link to the thread on thesamba:

http://www.thesamba.com/vw/forum/viewtopic.php?t=121044&highlight=drivetrain+loss

And this is turbobob's personal web page:

http://www.turbobobefi.com/

Paul

He's got a wicked shopping cart to!

My dyno guy said about 20% loss thru the d/train.

~WB

I've heard of 20 to 30 horsepower losses just for the fan?

Jake or Pat Downs, where are you?

I have heard about the application for the I-phone. I have been tempted to get one for this reason only. I hate a touch screen phone though. Please let us know how this applications works out.

bit of a hyjack

The air cooled fan will use exponentially more power as the RPM increases, till a point where the fan starts to cavitate. At stock type of RPMS the fan cannot consume 20-30 hp as some people say, Hell they only make 40-50 hp on a good day! The drive train on a beetle is amongst the lowest of all cars, Remember that the tyres also play a fairly significant part in drive train drag, Pump up the tyres hard after a dyno run and check again. I have seen as much as 10% by taking the tyre pressure up from 1.8 bar to 3 bar.

At the end of the day a dyno should be used as a reference tool. Before changing anything do a dyno run. Use this as a reference to see how much of an improvement each mod makes. Always use the same dyno at the same time of the day. Temperature and atmospheric pressure make a significant difference to the output of a motor.

What Greg says about measurements on the same dyno, et all, is spot on. Meanwhile, I'm headed for 3 neighborhood bars so I can check my tyre pressure.

I just tried that application for the first time yesterday. My 0-60 time was 5.81 seconds and it estimated my rear wheel hp at 110 assuming a fully loaded weight of 1950 lbs (me, gas, etc). That was on my second out of two runs. I think the application is great. I'm also not quite sure what to assume for transaxle loss. I suppose someone would have to have dyno'd their engine AND car to get the true number. All told, the application is worth the 13 bucks. I got it based on a tip from a guy I met at the AMG driving academy last weekend. He showed me the results from his BMW 335 that were pretty accurate with what the manufacturer posts.

Paul, what weight did you put in? You weighed your car at Carlisle, right?

The scoop on fans is about 12hp at 6000 for a stock doghouse fan.

The 911 fan consumes around 20hp at 6000, if I actually remember what I heard correctly.

Since these figures from the Iphone and those on a dyno are computed WITH the fan on, it really doesn't matter how much hp the fans consume now does it? I mean we're not drag racers with naked engines, are we?

Danny P,

My Speedster weighed in at 1708 lbs. I added an additional 190 lbs. to include me and my chin. While this program will get you close to actual HP, and its great to see 0-60, I find it most useful in the fact you can input dates that modifications are made to your car. You note it as 'carb floats adjusted', or 'timing adjusted to 30d BTDC', or 'New Exhaust'... than do a couple runs to see if the time/money/energy you just put into the car has done any good. My last two entries.... Amy's weight and Jessica's weight. They were both fun dates! ;)

P