xloki77x

iTrader: (3)

i have noticed since i started woekin on my 97 max 5spd that i haven't seen any large horsepower gains. the first mod i did was a place racing CAI and that, as far as i could tell didnt do much. when matched with a stillen catback, stillen y pipe, and a custommaxima straight racing pipe, i noticed a little difference but i still only dynoed at 176.6 whp and 183.3 ft/lbs. i prototyped a pair of headers and that only gave me 2.5 hp and 4 ft/lbs. i also have denso iridium plugs (saw no noticable increase in power). the one thing i have heard, though, is that the knock sensor could be playing a role in this restricted hp. i have an engine decoder that picked up from autozone for like $100 and that helps me turn my check engine light off because i have an EGR Flow Malfunction (the headers let more air through at the EGR valve so that doesn't concern me), an O2 sensor Malfunction (the racing straight pipe did that), and i have 2 codes for a malfunctioning knock sensor. i think that might be the problem. i have a new bosch knock sensor that i am going to put in as soon as it warms up a little bit outside (right now it's about 4 degrees). i also have a random tech cat that i think will help by created a little more backpressure for a NA car. The only other thing i could think of why my hp gains have been so small is that the air fuel ratio had been screwed with because there is just so much more air flowing through the engine. Any comments or suggestions?

Ceasars Chariot

iTrader: (16)

try the technosquare ecu upgrade .. while all our n/a mods are not transforming our cars into sometype of jet car, it seems it would help out a bit more with what you have.

seems like many of us should have just gotten a sports car

Vigo327

a knock sensor problem and youd be putting down closer to 140whp imo

I30tMikeD

iTrader: (8)

you complain about a loss in power yet your knock sensor is bad......

MrEous

iTrader: (11)

140whp on a stock Maxima...he is pretty much all bolt-on modded up.

It's funny looking at your #s cause mine are the same but I don't have a y-pipe or any other kind of exhaust work besides a testpipe.
(testpipes don't really give you any kind of gain, btw...)

Stephen Max

iTrader: (59)

Back pressure is always bad. Exhaust flow velocity is what you want to help with exhaust gas extraction from the cylinders. Unfortunately, it is difficult to build an exhaust system with good flow velocity and low backpressure.

I doubt you are flowing so much air in a NA engine that your afr is affected much, even in open loop.

Jeff92se

iTrader: (82)

You won't feel gains if your engine is not operating properly.

wickedmax

did you reset ur ecu after each mod....?

nismology

iTrader: (8)

It's your knock sensor...change it...

Dave B

I think your power problems are related to four primary areas (not in any particular order):

1) The Stillen Y-pipe. If you have one of the older Stillen Y-pipes, chances are the pipe has 2.25" primaries diameter and 2.3" main outlet. My Maxima dynoed 174fwhp/191fwhp with a Stillen Y-pipe, HKS muffler, b-pipe, and intake. My Stillen's flex section blew a few months later and I bought a Warpspeed non-mandrel y-pipe. I immediately noticed how much larger the piping was on the WSP (2.5" primaries, 2.5" outlet). With an intake, WSP y-pipe, muffler removed, and the addition of a UDP, the car made 183fwhp/193fwtq with substainial gains in the midrange. Another 4th gen 5 speed on the same day made 182fwhp/190fwtq with a WSP y-pipe, intake, and catback. It would be foolish of me to believe that the UDP created all the extra power and seeing that another 4th gen with same mods less a UDP made nearly the same power, I realized a lot of gain came from the y-pipe. I also noticed more power with the WSP y-pipe and my ET/MPH improved. I think some of your problems lie in the Stillen Y-pipe, especially if it's one of the older models with equal length primary pipes.

2) The knock sensor. If you've confirmed that the 02 sensor code has NOTHING to do with the two front 02 sensors and only the rear sensor, then you're pretty safe to assume you're not getting the "ghost" knock sensor code which typically comes on when one of the front two 02 sensors fail. A faulty knock sensor can definitely reduce power, especially under heavy load above 3000rpms. A bad knock sensor will show some jaggedness and relatively extreme drops in the power delivery. This could be seen if you posted a dyno plot.

3) The straight pipe. A straight pipe causes the rear 02 sensor to get an incorrect reading. Since the 02 sensor notices a problem with the way the emissions system is running, it changes the fuel delivery program to pollute the least. This almost always means reduced engine performance. Straight pipes are great for motors that move a lot of air (ie turbos), but on a NA V6 it's worthless and usually determental to performance. As for backpressure caused by the cat, todays cats produce very little backpressure or reduced power. Backpressure is never a good thing and it doesn't create torque. Good exhaust velocity is what creates power. Bigger is not always better. You want to keep the exhaust gases hot and moving quickly. An overly large exhaust allows the exhaust gas to cool and become turbulent in the pipes.

4) Dyno. Dyno machines are great, but they're not there for bragging about peak numbers. It's a tool to gauge your gains and losses. Every machine reads a little differently and that's why you should always dyno on the same machine and never compare your numbers to another car that's been run on a different machine. You really need to get to the track to see if your car really is lagging in power. The track tends to reveal the truth.



Dave

Stephen Max

iTrader: (59)

Sometimes some of the things you say utterly baffle me, Dave.

Dave B

What did I say that baffles you? I can elaborate if you need me too.


Dave

maxspeed96CT

iTrader: (9)

Ya i noticed my car is alot slower with the knock sensor bad. The thing is i remeber how it felt before it went bad and i had my mods . Im gona get mines dynoed soon and see my numbers after i fix my KS.

SleepyMaxxx68

What would that do....I've modded a bit and never have I once done it...then again my car isn't all that quick

Taken2DaMax

iTrader: (5)

You lose a good amount of power when the screw on the ECU is not properly in the right position.

Stephen Max

iTrader: (59)

I've never seen or heard anything that says that the Maxima ecu reverts to a least polluting fuel delivery if the rear O2 sensor signals are incorrect. This is news to me.