gator's 99TA

iTrader: (2)

my car is the ultimate example of the difference in driveline loss. why? i have not changed anything in the motor but have had 3 different transmissions. lets focus on the t56 combo and the 4L60e big stall auto.

first check out this TCI calculator site. good info. the biggest thing is calculating converter slip. now the BEST way is to measure driveshaft revolutions and engine rpm through the traps but well...i am not a ballah with a racepak computer onboard. this site shows me my converter slip % at 15%

go to "% Converter Slip Calculator"

bases it on rpm, mph, trans gear (always 1/1), tire height, and rear gear. this shows my converter is 85% efficient.

http://www.tciauto.com/Products/Tech...culators.asp#4

to eliminate how nitrous is effected by bottle pressure lets talk about my n/a numbers. LOTS and LOTS of people get mad at my talk of the dyno. first i dynoed iwth the 4K stall 4L60e at 328 rwhp on teh slicks in race form (15 psi). but i dynoed 340 rwhp on the nittos. so lets use the 340 rwhp comparison (i will explain later)

so if we use 340 rwhp x 1.15 = 391 rwhp if i didnt have any converter slip. this would mimic a stick shift b.c the clutch disc is locked and doesnt slip (or extremely minimally).

back in 2001 i had a t56 the same exact engine, dyno, gear, wheel/tire (26" nittos), and rearend as when i dynoed in 2006.

i dynoed with the t56 385 rwhp. not too bad of a calculator when compared to real life.

so:

385 rwhp with a t56
340 rwhp with a 4L60e

same exact driveline. why do big stalls dyno low? my particular converter had a slip of 15% = lost power. my numbers all added up. kinda crazy i think

btw, i went 12.01 @ 114 mph on a 1.59 60' (DA=+2500 feet) with the t56. but too many variables in comparing timeslips. the auto obviously ran quicker.

buffman

iTrader: (9)

difference there is the fact that a manual tranmission is going to have more often than not way less drivetrain loss than auto. I remember a 4l60e being somewhere in the 18-20% range, and a t-56 in the 13-15% range..

gator's 99TA

iTrader: (2)

the bigger issue is converter slip % - a fact rarely talked about

jimmyblue

iTrader: (11)

Whaddya mean... I talk about it all the time.

One thing you have to consider is, especially on
a higher stall speed converter, slip% may not be
an accurate gauge. If the converter is still
multiplying torque out the back, (1-slip%) is not
the efficiency, (1-slip%)*TqMult is. Slip% is only
meaningful at unity torque multiplication (because
we can't get the torque values). (1-slip%) is the
minimum efficiency, not the true efficiency. And
all of that neglects the transmission pump, drag
losses, that's yer sales tax. Whereas slip is more
of yer income tax, where you might be better off
paying more, if it's on account of more income.

gillbot

iTrader: (27)

my car with a PT4000 and cam+bolt ons dynoed at 399RWHP. Not too shabby if I do say so myself. Lockup helped on that one though.

Magnet

iTrader: (36)

^^what did he say

darrensls1

Personally I could care less if my converter made my RWHP number go down.

As long as it took my 60' and ET with it

bjamick

iTrader: (31)

i really dont car if a civic puts down more power on the dyno than me. its on the track where it matters. im only going to dyno mine so i can get it tuned a bit.

ls1408cp

iTrader: (37)

I put down 490rwhp on a fresh motor and I cant get it to hook on the street with a big slick

SteveC

On the automatic, the higher the stall, and STR, the more inafficient (sp) the converter. I have a relativley (sp) low stall 3K, and the converter is @ 98% effiency, couped to 3.73 rearend gears.

YOU DO NOT WIN RACES ON THE DYNO!!!

My dyno numbers are 295 RWHP/345 RWTQ (310 @ 5400 RPM) on my 2001 Z28, the car runs like a raped ape.

SteveC

BAIN

iTrader: (5)

My car dynoed 304hp SI with a TCI 4400 and ran 11.4's. Then I put the cam in dynoed 380hp and ran 11.0 with the same weight and mods. Unlocked now it does 380hp and locked 423hp.

bjamick

iTrader: (31)

you see this is a prime example where HP on the dyno doesn't mean it all counts on the track.. 304rwhp and ran an 11.4 thats a sleeper.

12secSS

iTrader: (30)

You are not looking at the results from a converter on a dyno properly. First, the converter will multiply torque from idle, and based on the STR, from there it will start to fall off at a good rate. The trans gear ratios (3.06, 1.63) also help to "multiply" torque on the track, unlike at the dyno. So at the track you will have more available torque to get you going (better 60'), way before the dyno displayed power level. Horsepower = (RPM x Torque) / 5252 Given this formula, you can see that if torque drops at higher rpms, it will result in less power. The stock converter is very efficient due to the overall converter (impeller, turbine and stator) design, so it can maintain torque much longer. Downside is that it will not multiply torque as much as most aftermarket converters. Hence why aftermarket units will 60' better then an OE. Plus the size of the OE is huge compare to the aftermarket unit. Which are typically 10", and as small as 8". The smaller they are, the easier they can be spinned from idle, but they also lose efficiency and produce more heat then OE. This is why oil coolers are needed.

I hope this helps you guys understand why high stalls produce less desireable number on a dyno ... it is the way the HP number is calculated, a harder hitting converter will lose torque multiplication at a faster rate (resulting in less torque at the measured HP RPM), and less efficiency from OE.

jimmyblue

iTrader: (11)

I think the payback of a converter is best summed up as
"A fast nickel beats a slow dime".

Getting your speed up early pays off more in ET than a
strong finish. Like compound interest.

JNorris

iTrader: (4)

Very good summary!

gator's 99TA

iTrader: (2)

good discussion fellas.

ofcourse i am not about dyno numbers. my 328 rwhp = 11.5 @ 116 @ 3500 lbs n/a

BerryWS6

iTrader: (9)

I jsut recently did the M6 -> A4 swap
with the T56 (stage 4 clutch, aluminum FW)it dynoed 403rwhp and 384rwtq
with the 4l60e (Vig 3800, shift kit...) did 400rwhp and 380rwtq (locked)
380rwhp 338rwtq (unlocked)
these numbers are all through a 12 bolt with 3.73s

I thought this would give A4 guys some insite on dyno numbers compared to 6-speeds.

Zombie

iTrader: (2)

I've got the ultimate in heart braking numbers. T76 on my 370 @ 15psi made 420 rwhp. Managed to go 10.8 @ 126 with that power and a 3800lb car with 2.75 gears.

Made a few changes, weather cooled off and I got 470 rwhp, that netted me a 10.5 @ 130 mph, if you do the simple HP calculators it shows I had to AVERAGE 650 rwhp to get my car to do that ET and MPH.

Dyno's are good for tuning, and that's all they should be used for.

Sean Collins

Those are interesting numbers. I find them to be very consistent with what i see dyno HP vs ET with mustang dynomometers.The big lie is the RWHP calculators showing far more HP then it actually takes. I have 2 guys same head cam heade combo and the automatic cars and the stick car et roughly the smae and the dyno numbers are very close. The stick makes a better MPH while the auto makes a better ET. I know a guy running 11.18 with 375rwhp so your mark at 10.8 at 420 with a 3550 car is right on for an f car or a y car.Converter slip will cost some mph but the gain in ET is worth it. It also depends on the car the gear and the weight of a the car. take the same drivetrian and lighten a stick vs stalled auto 1000lbs for both cars I'd be willing to bet the ET increase on the auto car will be greater every time as the converter is loaded less it will not slip as much and the efficency will come up.

Zombie

iTrader: (2)

The rwhp calculators use the simple HP formula. I'd say they are much more accurate than mustang or dynojet dyno numbers. It takes X amount of HP to move Y amount of weight in Z amount of time. It can be calculated using Net HP = Weight in pounds* (Speed in MPH/228.4)^3 It's probably the best way to figure out what kind of power you are putting to the ground.

I'll say it again, a dyno can read in garflabs, it doesn't matter as long as it tells you that you made more or less garflabs when you made a change.

FWIW My numbers are from a mustang dyno as well.