DaveGS4

iTrader: (2)

8speed, just curious.... do you know how a chassis dyno works by measuring power at the rear wheel vs at the crank?

Unless I'm missing something, the dyno above shows an increase of 21.8 rwhp and similar tq increase with the mods listed from the 'before' stock dyno.

javyLSU

iTrader: (21)

8speed - you do realize you're comparing FLYWHEEL horsepower to REAR WHEEL horsepower, right? Thanks for playing, though.

Javier

8speed

Maybe I'm not making myself clear.......I'm not speaking about gains from the exhaust modification. I'm talking about drivetrain loss to the wheels from stock. 84 hp sounds like a lot....and I've seen the IS-F putting down closer to 350 to the wheels. Again, what are you guys not getting?

DaveGS4

iTrader: (2)

8speed,

OK, let me try to explain. A chassis dyno measures the power at the rear wheels of your car. It basically figures out what the mechanical (and other) loss is through the drivetrain and records what the power is at the rear wheels. That's why people typically refer to the results as rear wheel horsepower and rear wheel torque

The 417 hp that you are quoting is the hp measured at the crank (right at the engine, when it's out of the car) by the manufacturer.

The 333 RWHP on the dyno chart above is the stock rear wheel horsepower of a 417 hp IS-F on a dyno. It ultimately shows the drivetrain loss through the transmission, drive belts, condition of lubricants, mass of rotating parts etc and gives the results of actually getting the power to the ground. That 84 HP difference represents the loss in a typical stock IS-F on the dyno. In most Lexus cars the drivetrain loss is about 20% (and this dyno proves that out). The loss on a stickshift car is typically less.

How you should be reading that dyno is a stock IS-F like yours makes 333 rear wheel horsepower. So if you wanted to work backwards you could calculate the 333 rwhp stock IS-F by taking rwhp divided by 80% to take into account the drivetrain loss. (333/.8 = 416.25 hp). The IS-F tested with the modifications made 354.8 rwhp so using the same formula that's 443.5 hp, a decent increase.

There are a lot of other factors including weather, temperature and a big difference in the way different brands of chassis dynos measure. The best way to measure what increases you get from modifications is to do it same day, same dyno... as close to the same conditions that the baseline (before) dyno is taken

Hope this helps. Loads of information out there if you google this stuff.

8speed

So the IS-F on Joe Z's dyno run lost 84 hp or 333 to the rear wheels? My point again for the 1000th time is that number seems low. How are you guys missing what I'm trying to say.

I understand perfectly how a dyno works. Again, what am I missing?

And I didn't know it took two mods to battle the 8speed. I must be moving up in the world!

Classic PM by the way......do as you say not as you do I guess?

http://www.dragtimes.com/Lexus--IS-F-Dyno-Sheets.html

DaveGS4

iTrader: (2)

I'm not "battling" anything; I just responded to review a reported post and saw some grossly incorrect information being posted by you.

You can read my edits in the post above, hope that helps you better understand what you're missing.

8speed

So Dave, you don't think the 333 is on the low side for dyno results? Honestly, what are your thoughts.....please enlighten us

I know dynos vary, but as I posted above......on the low side for sure!

DaveGS4

iTrader: (2)

I don't know the brand of the dyno that SP engineering has, so can't comment for sure but from the math it looks pretty much in line with Lexus' OEM crank claims. Every vehicle will measure slightly different as well. From the factory I've seen bone stock GS400 models have as much as a 20 hp difference for same year, same car.

Supraman16

iTrader: (5)

A 21 RWHP gain from a exhaust on a natuarlly aspirated car, like the IS-F is a HUGE gain. One would expect such gains from changing the exhaust on a forced induced cars.

8speed

Thank you for your insights. As you can see, it doesn't take insults and flaming PM's to get your point across! And you can see now what I have been trying to say in here for hours.

1. I wasn't discounting gains from exhaust mod
2. I understand the difference between numbers
3. My point was I thought the "TO THE WHEELS" hp numbers seemed low on JOE Z's dyno runs.

That's an hour of my life I wish I had back........

8speed

For sure........MY 05 WRX STI gained over 70 ft lbs. of torque with a turboback exhaust and ECUTEK reflash alone!

Again, I'm discounting the exhaust mod numbers.........but the baseline "TO THE WHEELS" numbers put down.

DaveGS4

iTrader: (2)

If you'll look at the link you posted, there are four dynos posted and two of them are ~ 333rwhp. Sounds like Joe's posted dyno is a pretty reasonable number given the evidence. The HP swing in others could be hotter OEM cars, modifications, weather, different reading dynos, etc etc

1) 357.00*# 345.00 Dynojet Lexus IS-F 2008 Cole
2) 357.00*# 345.00 Lexus IS-F 2008 Cole (duplicate)
3) 344.22*#+ 324.31 DynoJet Lexus IS-F 2008 CrazyMPG
4) 333.20*#+ 318.60 DynoJet Lexus IS-F 2008 NA
5) 332.50# 330.27 DynoJet Lexus IS-F 2008 gcollier

I'm not sure what you're saying here 8speed... you're saying I insulted you ? Please send me a PM with an explanation.

PHXDiesel

Listen.. I don't know why you keep beating around the bush and quite honestly it's starting to sound like a 4 year old throwing a tantrum.

What you WANT to say is Joe Z is artificially posting low numbers for his baseline. If you didn't want to say this then you wouldn't be bringing it up in every thread you could possibly squeeze it in.

Find a way to say it without acting like kid in high school.



And for my 2 cents... the numbers do seem low.. one of the lowest I've seen, although I have no idea how many miles were on the car, how old the oil was, etc. There are many variables. My car put out 362HP just after the 5k mile oil change.

DaveGS4

iTrader: (2)

Guys lets keep the personal comments out of this thread so it can stay open please, thanks.

Joe Z

iTrader: (10)

Looks like I missed a little bit of fun... But let me help clarify a few things...

The IS-F from the factory is rated with the following:
- Horsepower (Hp) 416 @ 6,600 RPM
- Torque (lb-ft) 371 @ 5,200 RPM
- Maximum Engine Speed (redline) 6,800 RPM

All Dyno's of the IS-F R&D car we used, were done independently by SP Engineering here in Southern Ca.
- Which means when we go there, we hand them the key & they dyno test the car, while we stand by and watch.

As others have stated, many DYNO testing machines across the USA and abroad will vary in many ways...
Even when the same brand is used.

For example here is "Automobile Magazine's" independent dyno test of the IS-F, from earlier this year..
Seems they achieved 333 Rwhp as well (Rwhp = rear wheel horse power)



The gains we posted for the exhaust, were again approx. 22 rwhp on our R&D IS-F.
I will & do expect that number to vary from other IS-F's and Dyno's across the spectrum.

"8speed", you bring up a somewhat valid question. In the future I recommend you properly post a direct question in the appropriate thread. We have a whole R&D thread dedicated to answering questions that members may have.
Unfortunately, it is not fair to others if you chose to post misinformation in various unrelated threads..

Thank You
- Joe Z

P.S. - Sorry to take this thread further off Topic, but if any other members would like to discuss the dynos or the exhaust, please post in the appropriate thread.