Why would our ECU's retard timing. I can think of bad gas as being one reason. Granted Knock Sensor is functioning properly what are some reasons the ECU would retard timing?

 

Generally, the ECU advances timing as far as possible until knock is detected.

 

I guess my first question is how do you know it is pulling the timing?

You need to know what your stock curve is first for a given MAF and RPM before you can establish whether timing is being pulled or not.

As far as I know, the only input that affects ignition timing (other than injector pulse width, based on MAF and fuel maps, and rpm) is the knock sensor.

Show us some data. Let's get specific.

 

According to the FSM, ignition advance comes from fixed maps based on rpm and injector pulse width. These maps maintain the ignition timing wihin the anti-knock range of the recommended 91 gasoline under most driving conditions.

The knock sensor circuit normally does not come into play unless conditions exist that lead to engine knock. (eg. WOT on an extremely hot engine with low octane fuel).

 

Ok this is kinda long so please be patient...
On Sunday the 21st i had my car dynoed again. This is the 3rd time i have had the car dynoed.On my most recent dyno prior to Sundays dyno i had made 176whp and about 186wtq. On my first run on sunday i Made 164whp and 17Xwtq. These numbers were made after adding UR underdrive pulley and new Denso Iridium Plugs (IK16). My previous plugs were Brand New NGK PFR6G11. So i dynoed again and agin and the car kept making hp in the 16Xwhp and 17Xwhp range.I checked tire pressure to ensure they were equal and adjusted accordingly. So myself and the dyno operator were very confused. He suggest that maybe there was an inatake leak so we checked and i dynoed again but same results. So he then asked what kind of Gas was I using and i explained i had Shell 93 Octane V-power gas but my tank was on 1/8, Gas light was not yet on. He said that maybe my fuel pump was not getting sufficent gasoline or that the gasoline in the tank was "Bad Gas". So i was like ok and went off to get some Mobil 93 octane. I added 5 gallons and dynoed again with same kinda of #'s High 160's whp and Low 170's Wtq. so we dynoed again and again and kept getting the same numbers so i was fed up and wanted to pull the car off the dyno. From looking at the graphs he suggested the car was pulling timing since Af ratio was the same on all the runs including my run where i made 176whp and 186wtq. I said i wanted to try dynoing with my AC compressor on so he was like ok and i did then suddenly #'s hopped back up to 175whp and 182wtq which is still less than last time but atleast wer were getting back there. Anyway long story short we kept dynoing again and again. Finally on the last two runs the car started making 182whp and 192wtq(3rd Gear) and then 179whp and 193wtq (4th Gear). So we decided to shut it down. these numbers were made on the the last 2 pulls. i Made 14pulls over 4 hour time frame. Car did not have cool down time between final 5 pulls. So i have concluded a Couple reasons for the power the car was making.
BAD Gas that took a while to exit the system.
The Engine was heat Soaked.
My Coil Packs suck (look How Jagged the graphy is 0 correction Factor)
The VQ30DE does not like Denso Iridium Plugs (enven thought they are $12.50 a plug)
Car doesn not like me.

I do not have copies of all 14 dyno's but i will have them once i get them e-mailed by dyno shop. i have copies of the last two dynos which the car made good power
here are the dynos. You can see how there is a dip in power around 5300rpm , which i am guessing is timing related.
http://www.cardomain.com/memberpage/633706/10

 

I don't quite understand why your numbers increased when you turned the A/C on.
At WOT, when starting and at high engine speeds, the compressor is supposed to shut off.

 

You could have spent 10 dollars less a plug, and filled up your tank with "good gas". Get your timing results using some sort of consult II type of program and graph out the reasings the next time you dyno, and compare.

What were the results after you turned the A/C compressor off? Did they drop back down to the 16x/17x? If they did, then the dyno shop could have been valid in stating that the "bad fuel" was purged out, but even at that some soprt of software program to veiw timing readings would have helped out a lot.

What were the A/F ratios?

 

Good point, I forgot about that , you can hear it shut on or off when going WOT/letting off.

 

Nope they stayed the same when i switched the AC compressor off. about 175whp and 18Xwtq. As i kept dynoing the numbers kept getting higher and higher. Eventually peaking out at the #'s in my sig. At that point there was no more cool down between runs. i would let the car idle for a couple while i looked at the dynos with the operator on the computer screen.
i wasn't sure about that maybe it was just a Coincidence that the numbers hoped back up when i tured on the AC. It was a couple pulls after i added the MObil 93 octance, so maybe all the bad gas was gone. I don't know what to make of it but still looking at the last couple of graphs on my cardomain page you can see that there is a dip in power around 5300rpm's.
What do you think dave? Could have been just bad gas?

NmexMAX the gas that was in there was 93 octance how am i to know if its good or bad?

 

1999 Nissan Maxima SE-L
5speed and California Emissions
JWT Popcharger
Warpspeed Y-Pipe
Sun Automobile Hyperground System
Greddy SP Catback
Catco Highflow Catalitic Converter
Mobil 1 10W30 Synthetic
New Knock Sensor
New NGK PFR6G11
New Fuel Filter
4th Gear

1999 Nissan Maxima SE-L
5speed and California Emissions
JWT Popcharger
Warpspeed Y-Pipe
Sun Automobile Hyperground System
Greddy SP Catback
Catco Highflow Catalitic Converter
UR Underdrive Pulley
Mobil 1 5W30 Synthetic
New Knock Sensor
New DENSO Iridium IK16
New Fuel Filter
4th Gear

1999 Nissan Maxima SE-L
5speed and California Emissions
JWT Popcharger
Warpspeed Y-Pipe
Sun Automobile Hyperground System
Greddy SP Catback
Catco Highflow Catalitic Converter
UR Underdrive Pulley
Mobil 1 5W30 Synthetic
New Knock Sensor
New DENSO Iridium IK16
New Fuel Filter
3rd Gear

 

The Af has nothing to do with it because they were the same for all the dyno runs. My car runs rich anyway. Once i get all the runs e-mailed to me i will be able to import the data in excel format for comparison.
It was sunday and he forgot his laptop so we could not read the timing. that is why i am trying to figure out what other than bad gas can control timing.
Tell you one thing i am not getting Shell Gas anymore and i am going to replace my plugs with the correct NGK plats (NGK PFR5G11). Right now the iridiums will stay i can't justify pulling them when i just paided to replace them $70 down the crapper. I would have put my platinums back in but they were one step colder NGK PFR6G11 so another $66 down the crapper (never trust mechanics).

 

Because you were the one who referred to it as "bad gas" on your long post.

 

Sorry man. I am not trying to argue> When i read this post i thought you were saying i was cheap on gas and i spent the money on the plugs. I did Use 93 and i only use 93 i can't help it if that gas station has gas that is inferior to other gas stations. I am not sure how much gas is where you live but its kinda expensive here $2.20-$2.39 a gallon. Which i don't mind paying if i get 93 octane that is 93. anyway i will just wait to see what Dave has to say.
I am hoping it was just the gas, although i do suspect my coilpacks are on the way out. I have had no signs of them going bad but my car is a 99 and they are Hanshins (not sure how you spell it). I posted this to try to find out what are possible reasons the car would pull timing. that is all.

 

The ECU pulls timing when it senses knock as mzmtg stated, so with cheaper, lower octane fuel it would pull back timing earlier, (less degrees), than it would burning better burning higher octane rated gas (+ more degrees).

 

Maybe it was your NISMO radiator cap. j/k

 

I guess that's it then BAD GAS. I just wanted to see if Gas was the only Variable that ECu retards timing based on. Is it possible to Hear knock. i mean the hood was open the whole time we didn't hear any weird noises from the motor.

 

Usually you can hear a ping/knock, I've heard mine when in the car, but when at WOT w/ I/Y/E, it might be hard to hear.

Fuel is not the only variable tht can cause it, temperature can also do it.

 

Excessive carbon deposits in the combustion chamber can cause hot spots which can lead to knocking.

 

Sounds good but i had the B&G intake cleaning done at nissan about 5k ago.
i am going to chop it up to bad gas. From eng92 and NmexMAX said this seems pretty logical. since nothing else really affects timing. The motor was warm but it wasn't that hot. If anyone wants to comment on why 5200-5300rpm there seems to be a slight dip i wouldn't mind.

 

Well the first one doesn't have that dip and it was with the NGK plugs. The 2 with the dips are with the Denso's. That might be it since that was the only variable that was changed from what i can see other than oil and fuel filter. The torque curve looks alot more jagged in general.

 

Could using the wrong spark plugs cause retarded timing? He says he was using denso's.

So the only differences between the two dyno sessions were the UDP and the plugs. I've never heard of a UDP making you lose power. Looks like proof that you should ONLY USE NGK. I say switch to either NGK plats or coppers and try again. Why did you switch out the new NGK's anyway?

 

I was trying to cheat, any extra power from anything. Denso Claimed extra power with the plugs so i decided to give them a shot. Man what a bad idea. nothing was wrong with the NGK's i only removed them to install the Denso's but when i pulled the NGK's i realized that they were One step colder plugs NGK PFR6G11 instead of the NGK PFR5G11. The two variables were UR pulley and Denso Iridium plugs. I will eventually switch back to NGK plats but for now i am going to keep the Denso's. Too damn expensive to dyno everytime i switch something so it will be a while. She runs goodand pulls hard. whatever the car is doing its making decent torque, wish i could say the same for HP.
i am planning on getting Auterra for myself and SAFC II then i will head back to the dyno.

Any comments Dave.

 

Sure.
When are you going to rewire your ecu harness so you can drop in a JWT or TS unit and then you won't have to bother with the SAFC?

You do realize that the SAFC modifies your MAF voltage to the ecu in order to change the injector pulse width and hence A/F. This will effect your ignition timing. I thought of going that route but it made more sense to change the actual baseline WOT maps for timing and fuel right in the ecu and then do some minor tweaks with an SAFC if necessary.
The AUTERRA is definitely a useful tool. I just wish we could monitor injector pulse width.

 

Yeah i did think about that but after there was no sucess on chuckies part i decided i wouldn't thinker too much with the ECU. I actually decided that i am not going to do anything drastic to the car anymore. ECU and MEVI combo would be another $1200 atleast and i just don't really feel that i wanna invest that kinda money into the car. The SAFC II is only $250( on ebay) and all i would need is an hour of dyno time. I am under the impression my car is very Temperamental so i don't wanna mess with it.
SAFC II will be my last official mod and i will fix anything that breaks. I am planning on getting AUTERRA, just kinda pissed off i have to buy a PDA since i have a LAPTOP. I am going to keep my maxima as a daily driver and just buy a 350Z this summer but i wanted to ensure the car was running to its peak ability.
I sometimes forget it has 113K. So therefore the Power it is making isn't that bad 180WHP and 193WTQ.

My old techtom MDM100N used to monitor injector pluse but it didn't work with my maxima so i sold it.
http://www.technosquareinc.com/mdmnis.htm

 

Why do you insist on buying mods that don't do crap?? Your's is one of the few cases where i wouldn't mind seeing someone sell their maxima...

 

As far as I know, Chuckie gave up because he couldn't get the pins out of the ECU harness. If you are serious about doing your own mods, you need to have a little perseverance.

If you do not have a PDA, then why would you go for the Auterra? There is equivalent software out there for laptops. I already had a Palm Tungsten, that is why I went with the Auterra.

 

i am going to get a palm zire 71

 

thanks for sharing man. i am glad to see you feel that way.