you needto move to Newfoundland, Canada = all types of fireworks, alcohol served in gas stations at like 2am and 30% tint

 

and 90 something odd percent isopropyl alcohol...

 

Ok guys update:

Compression is fine here are the results:
I let the car warm up fully and drove it for 20 minutes or so, unplugged the fuel pump, took all spark plugs out, and cranked it on the starter with the throttle wide open until the readings leveled out.

Here they are in relation to where they are in the engine bay, going left to right looking at it from the front. Or passenger side to drivers side. The arrow points to the front of my car


V
V
V
V
V

4 ... 5..... 6
163 170 171


1... 2..... 3
160 159 168




It held the compression on all these as well, letting it sit 10-15 seconds still held the same pressure. They maybe dropped 1 psi at most.


One other thing, sometimes my car will be sluggish in acceleration and I noticed with my friend in the car one time, it "came alive" at around 5800rpm and ran really strong to 6500. This definitely shows me something is holding back or out of tune because due to the nature of the USIM, the car should be producing less power up here, going to show my engine was really cutting a lot of power down low. Also I have noticed when running through the gears, sometimes it will randomly "come alive" and feel like it really has some oomph to it. This definitely means it has the capability of higher output and isn't a physical issue that is present all the time. This leads me to another thing IGNITION TIMING. I have a theory this is my problem, the computer is cutting timing. I was using my laptop to datalog my timing while accelerating, and unfortunately I don't have a high sampling rate, but here it is based on the points it captured. And this is with my foot at the floor the whole time in 2nd gear.

1563 RPM - 25 degrees
1888 RPM - 25 degrees
2263 RPM - 27 degrees
2600 RPM - 25 degrees
2975 RPM - 22 degrees
3325 RPM - 19 degrees
3700 RPM - 18 degrees
4075 RPM - 17 degrees
4438 RPM - 18 degrees
4800 RPM - 22 degrees
5138 RPM - 25 degrees
5460 RPM - 26 degrees
5763 RPM - 25 degrees
6038 RPM - 27 degrees

During this 2nd gear pull, my power curve felt flat as a brick from 2200 on. Which might have something to do with the timing. Because in theory, if everything were running optimally, I should feel a pretty large surge in power start to come on from 2800 till I approach the torque peak for the USIM which is about 4000 and die off by 5200. Instead, it was the same sluggish power the whole way through.

This was run using shell v-power gas. A fresh fillup.


Here is a youtube video of someone's max running very similar mods to my own, just an intake and catback exhaust:


http://www.youtube.com/watch?v=a2e9U...eature=channel


I was blown away by this, I can barely peel away launching in first with my ****ty worn down stock tires and with a good shift can barely get a chirp into second. This guy is spinning good tires (or so he claims, but they cant be worse than mine) through first AND through most of second.

Not to mention later in the video when he does his downshifts, you notice he punches it in the higher gear before downshifting, his acceleration still in the higher gear was amazing, are all Maxima's performing like in this video?

 

those ignition timing figures are normal for a stock ECU. actually a few degrees more advanced than I would expect.

 

Hmm interesting, that pretty much rules it all out then. The only other thing that it could be is perhaps the computer messing up my a/f ratio or one of my coil packs getting a bit weak and intermittent.

Either that or maybe I am just paranoid and/or unwilling to accept such a massive decrease in performance from my altitude.

Hmm...might be time to 00vi swap it with the DEK injectors and tune with a VAFC to compensate/get a bit more timing out of it.

 

check the echuast or cat and check ur plugs and oil pump

 

Well this happen to me, my 98 i30t was going very slow compared to normal and my rpms wouldnt pass 4500rpm (i have an auto). Turns out my floor mat was stuck under the pedal.

 

I cleaned the TB this past weekend...was just bored I guess...best,cheapest thing I've ever done..the car feels smoother, my idle issue has gone (would drop and sometimes cut off when coming to a stop). When cleaning the TB make sure to get the VERY TINY hole at the bottom of the flap..that's where extra air comes in for cold starts...I guess mine was clogged pretty good...

Whoops...saw you did this about 2000 miles ago..sorry..vacuum leaks? It might just be the car man. Stock 4th Gen's with high miles will probably not run close to what they did when they were new..

 

I have an auto and I am stock and I will tell you what the stock timings for an auto was a 7.1 but I am getting a constant 6.0 and If It's cool outside I can squeeze a 5.5 and I am not modded I am a stock FED and I have been on my maintaince and so on. I know the stock timing for a manual is a 5.5-6.6 If the car is having trouble take out the subs so you can get your timings back. It's really funny how the weather plays a big role in our timings.

 

Sounds stupid, but ive never liked Shell gas. Try different gas. Still no avail, test that knock sensor. Have you checked your MAF? See what the MAF readings are at WOT etc.

Dont feel bad. Sometimes i still feel my car is slow, sometimes it just feels like a dog, other times it feels fast as hell. But a faulty but dyno will do that.

 

Could be a ypipe issue. Unbolt your ypipe and shine a flashlight in it and check to make sure the flex section hasn't collapsed. Used to be a common problem with Y pipes.

I still don't think your times are so far off as to be considered abnormal, given your elevation though. Call it a 0-60 time in the low 7s for an average driver, and you're only a second off that at 6000' elevation. I think your car is fine.

 

yeah it was definatly raining in that video

 

I have noticed in my GLE after the y-pipe install, real low end 0-2000 rpm on accel it seems a bit slower but gained some top end. I guess its hard to tell on a car with 230k but maybe try throwing the stocker back on a take it for a rip.

 

Are we saying the youtube video is typical 5 speed performance? That guy had more lights than a christmas tree happaning on his dash

I'm in a similar boat to the OP but yet to do all the maintenace stuff yet - which I AM going to do

 

dude I just watched your video (didn't see it before). your car is running in a perfectly normal fashion. you're chasing a problem that doesn't exist.

 

I don't think the video is his car if you mean this one http://www.youtube.com/watch?v=a2e9U...eature=channel

 

you are correct. i didn't read his post well enough apparently.

 

that video is tight. i mean that car has power..my SE just chrips a little when i shift into 2nd. i did 0-60 on bald tires, and i got 7.5 with 190k on my car

 

Ok, I am feeling a bit less worried, I think it does just have to do with the altitude mostly. I did do some more tests though. I datalogged the readings from my mass airflow sensor. After flooring it in 2nd at about 2500RPM it started off at about 6.4lb per minute of air and increased linearly to about 16lb per minute at 5700RPM. One interesting thing though is:

5138RPM -> 15.27lb per minute
5438RPM -> 15.21lb per minute
5700RPM -> 16.04lb per minute

The interesting thing here is why would that reading go down slightly from 5138 to 5438 RPM? I kept my foot planted the whole time. Could this be a sign of a MAF going bad?

It seems like these numbers it is reading are a bit low. I remember messing around with this whole thing on my dad's 99 legacy with a 2.2 liter engine while he was driving in the mountains, and I vaguely remember the Subaru Legacy pulling in about 15lb per minute of air at roughly 4500RPM and about 85 percent throttle. Not to mention that was at about 10,000 ft of elevation in the mountains too.

Could my MAF be reading much lower than it should be? It is hard to imagine a 3.0 DOHC VQ30 pulls in less air than a 2.2 SOHC flat four.

 

Also, I datalogged my manifold pressure.

At idle it is roughly 7.5inHG. At 1500RPM and very light load around 8.6inHG.

Full throttle at:
2800RPM gave me 22.7inHG
3063RPM gave me 24.2inHG

stayed at 24.2 until:
3975RPM gave me 23.9inHG
4300RPM gave me 23.6inHG


EDIT: BTW, the barometric pressure outside was 29.6inHG at that time according to weather station history.

And it held that till redline.


Curious, why did this change throughout the RPM range? Shouldn't the manifold pressure be the same at full throttle regardless of RPM?

 

Bump, what do you guys think about those MAF and pressure readings?

 

make a video of ur car and post it..

Iv drive cross country many times in various cars.. altitude is key here... iv driven on pikes peak.. and you can have a 300 horsepower car on the bottom when ur on top you loose like 50%...

 

Modena ...

Those readings are likely due to the mapping of the ECU. And the altitude / barometric pressure / fuel quality / possible vaccumm issues ... a number of things. Not trying to discredit your findings at all ... I just think there are too many variables in play to get a dead zero finding. I would bet that if you changed the MAF (from another 4gen) you'd find the readings to be alomst exactly the same.

Just my thoughts ... hope I didn't come off as 'harsh'

 

my car sucked at 5xxx feet of altitude, so i think its all ok

 

hey so ive been having a similar problem as far as i think ive been having decreased performance, not sure tho. i do think i have a bad O2 sensor and could that affect performance? also could someone PLEASE explain to my my check engine light wont go off??