throttle reponse seems more torqy.

Does ping if bogged real bad (20mph in 5th)

Seems to pull better up in rpms for me.( coming out of 2nd at 6600rpms my speedo used to say 70-71 mph now I noticed it said 72-73mph. When I shift I notice that the rpm's seem not to drop as much to.

who no's, but it feels different to me. I beat the hell out my altima everyday. I tack it out in 1st, 2nd and 3rd. Hit redline regular basis. I know what the car feels like and it aint the same.

When it cools down a little I will take it back to the track and see if I can better my 14.3 that I ran with just WAI.

Definitly keep you guys posted if anything that happens.

 

Quick overview:

Timing refers to "spark timing", this is the moment in time when the ignition system fires the spark plug and detonates the air/fuel mixture in the combustion chamber. Ignition always occurs some number of degrees (usually measured in terms of crankshaft position) prior to TDC (top dead center) of the movement of the piston for the cylinder in question. This detonation occurs prior to TDC because it takes time for the air/fuel mixture to really start burning after the initial spark is fired.

The computers in our cars can alter the advance/retard of the timing. This means the computer can fire the spark earlier or later (relative to TDC). The computer using a special piezo electric vibration sensor (called a knock sensor) to "sense" spark knock. Spark knock is caused by the timing being advanced too far for the fuel being used. Low octane fuels detonate/burn faster than high octane fuels. So, if the air/fuel mixture is detonated prematurely, then the piston is still moving upward, toward TDC, and the force of the combustion is pushing back down against the piston. This cause "knock" and can damage engine components. To avoid this, the computer will automaticlaly "retard" the timing. This means that the spark is fired later relative to the upward motion of the pistion. For example, the Maxima base timining is 15 degrees before TDC, with timing advanced, spark might occur at 18 or 20 degrees before TDC. With timing retarded, the spark might occur at 11 or 12 degrees before TDC. More advance is better because it usually translates into more power and better fuel economy.

I hope this answers your questions.

 

How far did you advance yours?

 

The tech only was able to advance it by +3 degrees from the orignal readings (which was -1/ now it is +2). When he would try and do +4 more it would just go back to the +3 setting.

Before it was reading 14-15 bdtc and after it was reading between 17-18 bdtc.

 

Was the engine running? Can the advancing screens ONLY be done while the engine is running?

I'm wondering if the +3 degrees limit is a "safety" limit, because the engine is running. Also, with some of the Nissans I've worked on(older mostly), you MUST disconnect the TPS sensor before adjusting the timing or idle speed. Maybe, there is an explanation to why there is a +3 degree limit.

Sounds like we need to track down a Consult-II Users Manual.

 

the engine was running.

 

Okay, now i am suffering from a loss of power right now...

I no longer can chirp 2nd and it tends to BOG alot...

This in conjunction with the feel of a broken tranny mount makes my car feel HORRIBLE...

NO POWER AND MASSIVE CLUNKS AND JERKS...

GOING TO THE DEALER FOR DIAGNOSIS..

ED

 

Was the engine REQUIRED to be running inorder to view/change the timing on the Consult?

 

I thought this would happen! I was really wondering about this mod because you adjusted the timing + so many degrees it may have jacked up your power curve. I mean the factory timing is set at 15 and the factory sets the spark to fire when the piston is at the top position when your exhausts valves are closed. Now you adjusted that the piston could be on its way down when firing and unspent fuel is leaving via exhaust valves and thats where the clunking, jerking, knocking, or pinging is from.
I though the only time you should be messing with timing is when you have modified the internals of your engine.

 

Most likely these two things are UNRELATED.

Wait to see what the dealer finds, BEFORE you jump to conclusions.

 

CIRCO may be right, but I have some of my own experience to share.

I had a 91 SE-R with basic bolt ons. I was running 16 flat in the 1/4. After having my timing advanced 3 degress, I dropped .5 sec in the 1/4 and ran a 15.5. I did no other mod and ran numerous runs before and after this mod so it wasn't just a fluke. I can testify that it does work and I did not experience any side effects. Maybe the SR20DE engine is not as sophisticated as the max's 3.5, so maybe that's why I didn't have any probs.

Just my .02

 

My GUESS is that he broke a motor mount from the wheel hop he experienced while testing his new mod at the track. Now, every time he hits the throttle the mount clunks and MAYBE the knock sensor hears that and retards the timing.

There is NO way that "clunking" has anything to do with the timing advance UNLESS he is actually describing preignition, ie pinging.

 

This is getting interesting! If changing the timing generates enough additional horsepower to break the motor/tranny mounts, then we might have a real winner! Hmmmm.

 

HAHAHAHA... that would be so cool!!

I know that they are two separate items..

But the clunking is one thing,

The loss of power, i can't explain why this is happening. It almost feels as though the ECU is trying to retard the timeing for some reason..

When i give it throttle in 2nd gear, the car accelerates but at a much slower rate and the all of a sudden it accelerates harder but with a feeling like a NOS boost or TURBO boost (like a downshift on an auto tranny) even though i am in 2nd gear the whole time!! WEIRD>..


ED

 

demon tweak I'm very interested in the final diagnosis.. My car is still perfect and I did one spirited pull to redline in 2nd and 3rd yesterday and my initial observations are still valid...the car pulls harder across the power band.

I'm contemplating going to PIR Saturday night for some runs -something I have not done in 20 years so...we'll if I go and how the numbers shake out.

 

Your motor mounts are controlled and monitored by the ECU. When I had the timing adjusted the tech (It was the master tech that was adjusting my timing) also showed my how he can check each motor mount seperate. so maybe the motor the Ecu is retarding the timing cause it detects a broken motor mount, so it dosnt break it more or something like that.

my .02

my car still feels fine.

and I swear I can feel a definate power increase.

 

check your PM.

 

Have you already had the accelarator pedal stop TSB done/checked?

 

I think you've got the situation reversed (either that or I do! ) because the factory timing of +15 degrees means that the spark fires 15 degrees BEFORE the piston is at the top position thus allowing time for the flame front to propagate and in theory be pushing down the most at the TDC point of the piston path. Advancing this timing a few more degrees fires the spark even SOONER before TDC. The theory is with the higher octane fuel the flame front moves slower but burns a bit more efficiently thus sparking it a bit sooner allows more fuel/air to be converted to thermal energy once the piston hits TDC. I don't think there is much chance of this fuel blowby you refer to if the timing was trully advanced.

 

Galo.....was your car still under warranty when you had the timing advanced? Do the techs care if they are responsible for any damages like detonation? Thanks for any info.

 

My car was built in 02, so its not applicable

ED

 

I totally agree, i definately felt a power increase after i got the advance last week. 6th gear pulls to 100mph revealed definitly more power than before.

But now i have a sudden dramatic loss of power.. I constantly down shift to accelerate now. It almost feels like my engine is dying!!

Even a 1st to 2nd shift full throttle doesn't chirp the tires anymore..

Which is odd because 2nd gear chirps were so easy to do before, even at half throttle i feel the chirp..

Strangely i thought it was because of hot weather but the weather right now is freakin freezing, so it rules out the heated air temperature theory..

I am making another appointment to Nissan to have this situation rectified..

ED

 

Hmmmmm. This thread is intriguing. I spoke with my Service Writer today and told him I was thinking about advancing my timing to the maximum setting allowable while remaining in spec. He said that wouldn't be a problem. But I think I'll watch this thread a little longer before I do. I'm particularly interested in finding out what happens when Ed takes his car back to his dealer.

 

What are motor mounts anyways? how can they affect how the ECU operates?

 

I think there are some important factors that are not really being discussed here, but need to be.


Computer controlled engines generally use a predetermined ignition/fuel map when in "open loop" mode (this occurs when the engine is cold). I would assume that this map takes into consideration inputs from the knock sensor and temperature sensor but probably ignores the 02 and MAF sensors to determine the appropriate settings.

Similarly, in closed loop mode, I would expect the computer to operate from a base map which is then automatically "tweaked" or "adusted" based on real time inputs from the various engine sensors.

Assuming this all to be true, a number of questions arise:

1. What is the maximum variation or range for each adjustable value when the engine is run in closed loop mode?
2. What happens if a vehicle with the timing tweak applied is refueled with bad or low octane fuel? Can the computer still adjust? If the computer can't adjust enough, then what happens?
3. Does the additional advance of the timing change cause other parameters on the map to become skewed as well? If so, which ones?

For people beginning to experience performance problems after the timing tweak, I would ask if they had tried to use an octane booster to see if this helps the problem at all. Also, does the problem occur when the engine is cold (i.e. open loop) as well as when the engine has warmed up?

Has anyone tried to install an aftermarket knock sensor (such as a Link sensor) to monitor spark knock?

Has anyone considered replacing the stock ECU with a high performance/programmable racing ECU which would allow us full control to really tweak this engine?

Just my .02 cents.

 

The motor mounts are a metal housing w/rubber type material center, that eliminates metal on metal contact thus allowing engine vibration isolation from the chasis. Got that? Basically, they ATTEMPT to hold the engine to the chasis, while minimizing the harmonics of the engine from the passenger cabin.

The Maxima however comes with fluid filled electric dampening motor mounts. The ECU reads the crankshaft position sensor(POS), crankshaft position sensor(REF), and vehicle speed sensor to switch the mounts from a "soft" mode at idle to a "hard" mode while driving.

All this is per the '01 ESM, but so far I haven't found anything related to a feedback signal that would cause the ECU to retard timing.

 

No one knows this except Nissan. However, the +3degrees is well within the +/- 5degrees the factory specifies for BASE timing(at least in my 2K1 ESM). Once, the throttle is applied the fuel/spark maps move anywhere from -10degrees to +60degrees BTDC.

Depending on load and ambient conditions it could cause slight predetonation, which the KNOCK sensor will pick up and if severe back of the timing PLENTY to prevent damage. You'll lose the snappy throttle response and slightly better mid range pull CLAIMED by this mod, but the ECU would still be able to pull timing back enough to control predetonation.

I'm not 100% positive on this withOUT knowing Nissans' design, but I'm saying no. This is a BASE idle ignition timing and it's within specified limits of +/- 5degrees. Once the throttle is applied the ECU advances the timing and will override the +3 degrees to the point it won't be noticeable. This is why it's typically claimed to improve LOW-end throttle response and mid-range torque.

Octane booster is crap. The "best" available ONLY raises it "3-4 points"(NOT OCTANE points!), which means if your running 92-octane and you add the "booster", your only at 92.3-92.4-octane. Trust me, unless you pour several bottles of it for one tank of gas it will NOT make a difference. I've tried EVERYTHING but making my own, which I'm now planning on doing. BTW, this is NOT on the Maxima.

I haven't heard of anyone trying one.

No offense, but this topic has been SEVERLY beaten to death here. Try the search feature and you'll find PLENTY of information.

 

Despite the fact that I have been active on the board since December, I have not really seen very much discussion of aftermarket replacement ECU's. I know that there HAS been discussion of swapping the Maxima ECU with the 350Z, etc.

I just checked my ESM and it confirms the +/- 5 degrees range from the base timing of 15 degrees BTDC at idle for the 3.5 VQ.

I wold probably try out a better fuel and see if that changes things. Getting an aftermarket knock sensor might also be a wise choice.

 

Wow!!! - you 3.5 guys have a lot more latitude with this than us 3.0 guys. You're within spec at 15°± 5° BTDC?????? (vs only ±2° on 3.0VQ's). That is yet one more reason to seriously consider trading in my 2K1...hmmmmmmm.......

 

The 2K-2K1 VQ30DE-K is also 15°± 5° BTDC.

 

hmmm the ESM I have (for 2K) says ± 2°???

 

yeah... spec for the 2k is 15 ± 2° according to the ESM

 

Is it a Nissan ESM? Or the ebay version? Does it specify for a FED or CALI spec?

Otherwise, I guess only for a 2K1(Cali of course) it's 15°± 5° BTDC.

So don't trade in your 2K1 just yet.

 

It's in the Nissan FSM.

 

...and it's independent of whether your car is cali spec/fed spec....

 

Then why would a 2K1 have different specifications than a 2K?

 

I got this from the Nissan 2K2 ESM. It does not specify Cali vs. Fed.

 

yeah....that doesn't make sense. Mine is also a Nissan ESM. I'm going to try and get to my dealer tomorrow morning to have it adjusted and I'll check this with them. ± 5° seems like a huge spread to still be within spec, though......

 

hmmm I wonder why? Maybe because there is only cali spec after 2K....

 

I haven't confirmed part numbers yet, but I'm guessing his ESM is for early 2000 model vin numbers and therefore ONLY specifies for FED emission spec cars.

The late 2K Cali spec models and ALL 2K1s are ALL going to be ±5°, since I'm pretty sure the part numbers are the same. Damn it, I should have asked DaveB today. Oh well, I'll put this mystery to rest once he gets my order in.