I have a 6MT G35 Coupe. Car was just dynoed at an independent dyno shop that runs a DynoJet 224x dynamometer. Prior to the turbo being installed, the car was putting down 230 rWHP and 220 ft-lb TQ. The most recent dyno with the ST installed shows 290 rWHP and 315 ft-lb of TQ.

It would be an understatement to say I am disappointed. I am taking the car to the installer/tuner on Monday to troubleshoot, but figure I get some input from the VQ community.

These are the facts-

Dyno done in 4th gear

Installed:

APS ST
APS 2.5" 350Z exhaust with extension to fit G35
APS Plenum
SP Cams (not sure which ones)

Boost goes to 8 and drops to about 7.5 to 7 at redline. Running on 91 oct.

I'm sure dyno graphs would help, but my scanner is busted.

I know there is a thread somewhere with someone who had the same problem, but I cannot find that thread.

Given this information, any help/speculation is appreciated.

I just need enough info to hold me over for the weekend. I'm sure my installer will have everything resolved on Monday.

 

Sorry to hear it Vinh. Its nice to get a outside dyno every once in a while. Ive been saying that dyno puts off high numbers but no one wants to hear it. Its is nice to see that its holding boost pretty good though.

 

huh, i thought you were making around 400, didnt you post dyno numbers when it was first installed?

 

When you say the car is going to the "installer/tuner" on monday, do you mean that they have already attempted to tune your car once after the kit was installed? Or are you still running the default tune that comes with the kit, right out of the box? Either way something is wrong, but if the car has already been "tuned" to some extent, then something is more wrong than if you are running the default out-of-the-box tune.

 

car was tuned and it runs great, just not getting the HP/TQ numbers I was expecting.

i thought i was running 400, or at least that's what the numbers on the other dyno said. i always imagined 400/400 would feel differently than what i was feeling, so i wanted a different dyno to compare to. now i have some numbers to compare to.

i know dyno #'s vary day/day, but being off by 100 pts is a lot. i've had my car dyno'd 3 times at Modacar at different stages of my mods, so I'm pretty confident there numbers are good.

now i need to figure out if something went wrong between the tune and today or if the numbers from my first dyno were inflated.

i'm hoping it's the latter since my car "feels" fine.

 

Yeah damn bro hope you get that figured out. Shouldn't those be putting down a minimum of 370ish??

 

Speculation: Dyno is whack?

 

if everything is normal, what is causing the numbers to be so low?

if something is broken or not working, what can it be?

i also noticed during the dyno that when they got off the gas pedal at the end of the dyno run, a puff of white/blue (hard to tell) smoke came off the exhaust. is this normal?

car was warmed up prior to the dyno pulls. 74 degree weather, 29% humidity. 29.62 in-Hg barometric pressure. SAE 0.99

 

is the boost you are seeing on the dynojet the same boost you are seeing on the street? I ask because you will need load on your car to make full boost. Dynojets are not load based dynos so you may not be making full boost. What about your AFRs on the dyno vs the street?

Just thoughts and places for you to start.

your car is going back to the tuner so have them throw it up on their dyno again and see what numbers it pulls. What kind of dyno was it tuned on?

As far as the smoke goes, it could be A LOT of things. Could be something simiple like a lack of a catch can. Could be a PCV valve that is leaking under boost. Could be a bad ring. Could be a leaky valve stem. etc. etc

 

are you an auto?? why are you dynoing in 4th gear??

 

hmm....i think you're right Zivman. Until I speak to my tuner, all this speculation might make me worry more than I should. the car was tuned on a dastek dynamometer which I was told is a load based dyno.

the dynojet i ran on today is not load based.

i was not sitting in the car, so could not record my A/F or boost.

under road conditions and at full boost (4000 rpm), the car runs in the 11.6 range (wideband sensor in downpipe)

on the dyno chart, the A/F stays at 13 at 4k rpm, goes down gradually to 12 at 5k rpm, drops to 11.5 or so from 5k to 6k, and drops a bit more to 11 after 6k rpm. but of course the AFR measured on the dynojet is at the tailpipe, which is usually leaner than those measured close to the manifold.

i guess my concern is that others who have run their ST on a dynojet are getting much higher numbers.

in either case, more input/comments is appreciated. otherwise i'll just give them a call on monday and go from there.

edit: Modacar has always dynoed G35 6MT in 4th gear. I understand the 1:1 ratio, and the car was originally dynoed in 5th gear by the tuner, but i don't see it being the cause of the 100 HP and TQ discrepancy.

 

well if you're base numbers were at the same dyno then the gains you made are deffinitely weak... 70hp gain with boost and cams

I mean there are a few ways to manipulate numbers for better or worse on the same dyno, but not enough to account for the numbers you're making.

were the cams installed correctly? bad came timing can really jack stuff up, did they narrow your plug gap after adding the boost?

AFR seem pretty good, if its getting down to 11 at the top you could probally get a little more timming into it, but over all the AFR seems like a pretty safe tune.

 

last weekend mine made 375hp and 404tq, on a 5th gear pull. thats running the stock untuned maps for 93octane. and thats with a bad, bad, messed up turbo. half of my turbine is gone. boost peaks at 12 and drops all the way to 6 by redline. my afr is perfect tho.

 

I know a guy that made that same amount of power untuned,whenever i see cars dyno that are FI, theres always gonna be some smoke, if your tuning.

 

I'm running a similar setup. aps st, aam spacer, jic exhaust, scotts cams and utec. once we installed the utec and cams, the fuel pressure started acting funny. fixed that problem with a sard regulator and new pump. now with these cams, the boost is jumping around and we can't get consistent pressure numbers to tune the car. waiting on turboxs to send a boost solenoid they say is compatible to the utec. hopefully my shop will have some good news for me because i havent seen my car in a minute.

 

Something is wrong for sure,
You will know it for sure if you have anything near 400whp
400whp:
290whp:

 

my dyno sheet.

one is before the ST was installed and one after

 

Man sounds like a exhaust leak. My T- netics kit did the same thing and it had a couple of exhaust leaks.

 

here is mine to compare to. mine peaks earlier. remember this is with my jacked up turbo tho.

 

Id say try going to another dyno. If your hitting a consistent 7-8psi, u should be over 350whp.