cruiser

Hi !

I have following performance mods on my car:
- APEX'i power intakes
- Pettit downpipe
- midpipe with 2" 1/4 restrictor plate
- catback
- M2 Stage3 ECU

I had my car on the dyno yesterday and they measured 253hp at 10psi and 284hp at 12psi AT FLYWHEEL. My friend has stage4 300ZX and he should be around 400hp but this dyno only showed him like 320hp at flywheel (he dynoed around 380hp at some other place, but this tuner claims that other dyno is crap). We think that the dyno is showing bad results. I have perfect 12-8-12psi boost pattern.

Could there something be wrong with the car ? Or is the dyno just off ?

Thanks !

Fast Car Slow Driver

just curious, how do they dyno at the flywheel?

T88NosRx7

iTrader: (1)

yeah, I thought that the engine had to be out of the car in order to measure flywheel hp.

cruiser

They measure rear wheel hp, then at redline they press the clutch and wait for the rear wheels to come to full stop. From this they can measure the horsepower lost through transmission. They add up the loss to thw measured rwhp and you get flywhp.

But back to the original topic, I thought that Stage3 mods should be good up to 330-350hp (280-300 at the wheels) ? Oh... and the stock IC was very cool after the dyno - they have a good vent.

RX7SpiritR

iTrader: (1)

ummm....that flywheel BS is just...well, bs! Where did you get the idea that you could measure flywheel horsepower this way?! You can't measure flywheel horsepower accurately that way, It doesn't even make sense! There are calculations, but every car is going to be different in drivetrain power losses. I think there is something really wrong somewhere.

rynberg

Their method for determining drivetrain loss has validity....

What type of dyno was this? A "mustang" dyno or "dyno dynamics" will show lower results than a dynojet -- usually 15-20%.

cruiser

The system is MAHA LPS 2000. It's some German dyno.

evot23

iTrader: (17)

Sounds poor to me. With similar mods I was at 276 at rw. with 10 psi

Conv.WS6

Dyno numbers can vary. Just get your trap speed at the end of the 1/4mile, take your car to be weighed, and then you can pretty accurately know what kind of HP you are putting down, and whether it's matching the dyno.

911GT2

My car put down 260 with a dp, intake, and Power FC @12psi. Add in a cat-back and a midpipe and I'd expect to be about 280-290 RWhp. Maybe they forgot to do their crazy calculations for flywheel hp?

SPOautos

Different dyno's read differently. I wouldnt worry about comparing your readings to day a dynojet. Sounds like there are 2 VERY different dynos and I'm sure they get different readings.

Just do like WS6 said and go see what your mph is at the track.

Also, you have to remember that restictor plate is cutting hp as well!!!!

STEPHEN

cruiser

Well, I'm getting my GTech back next weekend. How accurate is that thing for measuring 1/4mile and speed ?

My car feels fast. I think the dyno is off

Restrictor plate is keeping my engine alive

jantore

Just for comparison i got 321 RWHP on a dynojet with these mods. And at 15 psi

HKS intake
DP, MP, Catback
Greedy FMIC
Re-Amemiya uppgraded ECU

And a half working fuel pump . Changed it a week ago and the car runs much better now

teamstealth

the Gtechs can give you a ballpark for all that stuff, but they arent highly accurate. My car with its current mods in the sig got 213 rwhp on 6-7psi of boost (my manual controller took a **** on me the day before the dyno run).

turbojeff

iTrader: (30)

You need an IC for sure. Otherwise like others have said, dynos actually seem to vary a bit. Do a google search someone has done a comparison recently, same car different dynos and the difference was actually alarming.

boostedrotor

a long time ago in a galaxy far far away, when my car was just in its infantile stages of modifications, it dynoed @ 276 with just an intake, cat back, downpipe, high flow cat, and streetport.......but like i said, that was a long time ago, and 200 less hp than now..

DaiOni

US dynos (usually dynojet?) generally read higher than those used in other areas - so using hp ratings from this site is a bad rule of thumb.

It's also very important to regard a dyno as a tuning tool, not a bragging tool. If you want to brag on a dyno ('my hp is better than yours'), you need to do it back to back on the same dyno.

persuasio24

Hmm, how's your compression? I had similar mods except for the midpipe,and I dynoed at 265 rwhp, but compression is down at about 5 all around (thus the tidbit in the sig about the rebuild).

Mahjik

iTrader: (1)

Moral of the story here:

If you are happy with your car, don't put it on the dyno.

Why? You'll rarely get the numbers you expect or want. Now you are unhappy with your car for no reason.

ttb

what kind of gas do you guys have in europe?

VortechPony

Another difference is what it is measured at. Ex: SAE , Din , Corrected and Uncorrected etc. etc. Pretty much no 2 dynos will give the same numbers even if same brand do to how old that are and what they set the car weight up to. A dyno that is set up if a cars weight is 3500 lbs will give a different reading than one that is 3000lbs. The weather will also play a huge part, if it is hot out your numbers will be lower. I have run a dyno jet for 3 years, and I do not belive in numbers at all. All numbers are for is who's d*ck is bigger. Because a car that makes 400 at the wheels will not always out run a car that makes 350 at the wheels do to suspension and driver error. Belive me on this because I have handed alot of people their asses when they have made more than 100 more horses at the wheels than me (in my Mustang).

P.S. most shops use 15 % for a stick and 20% for a auto to convert flywheel horse.

cruiser

I always use 98octane gas for my Rex.

Mahjik : I'm not unhappy about my car. Quite the opposite. I'm very happy with it but a bit pissed for paying for something that wasn't done as it should be. 2 days later now the tuner thinks me and the buddy with 300ZX had wheelspin on the dyno (speed recorded by the dyno is like 20mph lower then actual - indicating wheelspin) - although he said his dyno is good for up to 450hp. He wants us to measure again, this time with loaded backend - ppl in the trunk or some weight.

I didn't get my compression tested, but guessing that I have NO starting problems (I only start it up - drive on weekends) or idle problems (idles smoothly around 500-600RPM) I would rule that out.

I guess its really an issue with the dyno's measuring up to %20 different results.

That 300ZX is around 400hp and I'm about 35hp down on his power (from this dyno measurement) - seems I have around 350hp or even more - so that keeps me satisfied

Ahh... I forgot to add that I have an Efini Y-pipe also.

inis

Frankly, im more interested in what it put down at the wheels. THe shop you dynoes at should have that. And if they dont, i wouldnt spend much time there anymore. I think if you post that we could all give you a better responce.

Is the ECU tunable to the point where you can raise the boost? Im not saying i would suggest it with the full exhuast, but its something worth checking into.

cruiser

They measure hp at wheels. Then after they hit redline, they press clutch and let the wheels come to full stop. This way they get drivetrain losses and can get crank hp.

M2 ECU is not tunable and I can set boost with my ProfecB - on low I run 10psi and on high I run 11.5-12psi.

It's about 15hp hp increase for every 1psi of more boost.

artguy

yer still running rich Id assume...probably lean in some spots too...those chipped ecus are a joke and are at the very best a GUESS at what you should be tuned for. lose that ecu and tune it properly. you will see the power you expect. trust me on that. I had a gforce ecu before my pfc...then i had the car tuned and tuned and tuned and finally got it close to where i should be. one more session to go.


cheers

j

PS...its not always 15hp per lb of boost...its not just the boost that is the factor..ITS THE TUNING. another case would be when your turbos operate past or before their efficiency level. power gains on the bnr stage 3s (leaky or not) actually go down past 18psi....thus more power at 17psi than 19 (which is what brian explained to me previously). I found similar patterns with my turbos. in the end though...its tuning tuning tuning...and yer car is not tuned. period.