READ NOTES UNDER THE DYNO.



YES, looks like I have a problem. Starting to work through this with Nissan now. Car is BONE STOCK, oil consumption issues notwithstanding. Make note of the dates of each run.

 

haha wow.

 

how many miles you got? it might just need a tune up you can lose a lot of power with a dirty air filter and used plugs. my .02

 

you are losing power eh....according to the dates your baseline should be on the earlier run and not the latter...?

 

Baseline is just a title the shop gave the file this time. Has nothing to do with the power deficit.

 

Temperature, weather, humidity, elevation, same dyno? Have you changed oil recently? More/less weight in the car? Clean air filter? New spark plugs? New wheels/tires/sizes?

There are a TON of things that can make a dyno do weird $hit man; what does your butt dyno tell you? Less power than when you got it? How did you break in your engine?

I guess the point I'm trying to make is that dynos are inconsistent at best and usually not a very reliable tool from dyno to dyno if not done back-to-back on the same day, and even then most performance mods need to break in a little before they show max gain. I know you don't have any HP mods, just pointing out how finicky dynos can be.

 

Just under 23K miles. It does not need a tune up. The air element is changed every time the oil is. I've spent a ton of money on preventative maintenance well in advance of schedule and the car has been very well taken care of. My service record is a dozen plus pages long at the dealer.

 

Yes, those are all things I've considered. Same dyno. The temp on the first dyno in March '03 was 70.01 degrees. The temp for the Feb '04 dyno was 44.78 degrees. The VOLKS weigh LESS than my stock 18s. NOTHING has changed on the car. Same type of oil, same brand gas, same air filter. Oil changes every 3,750. I looked at all of the varying factors. My engine is simply down on power and I need the dealer to run a compression test which they (or Nissan) do not want to do at this point.

A 14 HP loss is staggering considering that NOTHING has changed about the way I take care of the car.

 

The thing with rims is that its not necessarily that lighter rims reduce rotational mass. Its where on the rim the weight is. For example: if two sets of rims have the exact same weight, but one set of rims has most of the weight in the center, while the other set of rims has most of the weight at the outter edge, then the one with more weight in the outter edge will take more power to spin. Since your rims are 8.5 and 9.5 that means that even if they are lighter, there is more weight in the outer edge of the rims, also, since your tires are 245 and 275 that added additional weight over the stock tires, because of the obvious increase in size. Also, if you have a break-kit where the rotors are heavier than the stock rotors thats additional power lost to the wheels to spin up the rotors.

 

How do the A/F print outs match up?

 

Why are people trying to convince him that there's no problem? If it were me, i'd check to be sure, so that I know my **** is running tip top.

 

It's hilarious, the polar opposite of a, "I made 15HP at 6599 RPM!" discussion. It's a power loss across the entire RPM range. It's not the wheels, for ****'s sake.

 

have you been to the 1/4 mile track back then & more recently??? Does the car feel slower?

 

My $.02

Since the curves are virtually identical, I'd write it off to dyno calibration. "I" wouldn't put so much faith in the #'s. They're just #'s. Dyno's should be used for tuning....NOT as an absolute.

Relax & enjoy you're Z.

 

I'll throw something out here. Was the car run in the same gear both times? The chart has different gear ratios listed

Would that make a difference?

 

Tell them your motor chokes sometime when you drive it. Bog as we say it...lolz...although its not turbo. And see what they do. Maybe they might do a leakdown test. Who knows. Well have you been running the $hit out of the car lately? If you keep that rev up in the redline range and for long period of time, you might warp the damn rings. Could be losing compression. Definitely persuade your dealer to do a leakdown / compression test. And make up some other $hit such as when you drive for like half an hour or more, at 70 mph, engine makes some popping noises. Just make it up. Cuz I don't think they will take your car out and drive it for 1/2 an hour to find that out. Good luck and keep us all posted!

*I respect the other fellas for saying dynos are different and we do have to take all of the other things in to account. But be smart homie! It's your ride. Make sure it runs "tip top" like Z-***** says.

 

What I am concerned with is that is DYNO #07, which was your FIRST run of the day since #06 was most likely your best previously.

MEANING - Your oil temps, etc were NOT up to spec... we've seen a 10hp difference between a first run, and a warmed up run.

How many runs did you make after 07? Show us ALL your runs!

Quit being so dramatic Droid.

*Edit - You're not dyno'g with the stock wheels??? Dude, you're adding in variables. Wheels/tires on a dyno ... KEEP THEM THE SAME. Don't say otherwise!!! Either way, I'm sticking to what I said originally.

 

when's the last time you reset the ECU? That makes a huge difference. I would dyno again, just to make sure.

Your car should be peaking at 20k miles, not the reverse.

 

every time? that doesn't seem right. You should spend $40 on a lifetime filter from k&n. they flow better and you're not tempted to throw your money away because the guy that changes your oil sees a piece of dirt on your element. Then again maybe you change your oil every 10k miles.

 

Comparing ONE dyno from ONE day...and ONE dyno from a completely different day when the car was not set-up the same as before doesn't hold much water.

Maybe if you had 4 or 5 dynos one day...and 4-5 the other day and figured an average difference that was more than around 5whp.

I had two pulls in one day within 5 minutes of each other and they were seperated by 5WHP and 7ft/lbs of torque. That's on the same day....get some more dynos....and if you find a huge difference...THEN make a stink...