Adjusting timing?

[92Q45guy]

I know the timing can be bumped . I have a timing light but just dont know what notch on the crank pulley to go buy. Anybody advanced there timing a little. Would I get some better milage out of the car? I get around 350 miles out of the tank now. I would like to squeeze a little more power out of her also.

[maxnix]

Wise members never let their tank go below ¼ full.

Check Q45.org for timing how to.

[92Q45guy]

Thanks, I really dont let it get to empty all the time. When I fill up a put like 16 gallons in it.

[92Q45guy]

I just checked the q45.org about the timing. Is there anything you need to do before adjusting? Like jumping a pin or disconecting something. I know on most cars you have to do.

[carfrk666]

350 miles? daang, im getting about 220 miles till 1/4 tank

[Q45tech]

Static crank/cam CAS advance is just the base of the equation.

The ecu is programmed to assume the advance is 15 BTDC and then to add between 5 and 35 degrees as necessary based on rpm and TPS load factor.

Any advance that would have increased mpg would have already been used by Nissan to reduce the CAFE Tax they had to pay.

If you monitor the total advance at steady cruise you will see it is near 35 degrees already.

Too much advance just allows the knock sensors to fire too early actually reducing the light load advance to stop the knock.

If anything I would think extra advance above 15 would actually hurt MPG.

[92Q45guy]

Thanks, I read it somewhere it might help. But I guess I'm getting pretty damm good miles per gallon.

[DrewQ45]

Thanks, I read it somewhere it might help. But I guess I'm getting pretty damm good miles per gallon.

Word to the wise. If it ain't broke, don't try to fix.

[92Q45guy]

Word to the wise. If it ain't broke, don't try to fix.

thanks, But nothing is broke. I was just wanted to see if I could get more power out of it.

[db_autotek]

I wouldnt do it on my Qship but when I adjusted the timing on my Miata (few simple bolts + 5 minutes on timing light) my MGP went to $*** but my power went way up. Always always always, when you advance the timing, you loose gas milage but gain power. Ask any of the racers or hotrod dudes.

[DrewQ45]

thanks, But nothing is broke. I was just wanted to see if I could get more power out of it.

Exactly my point...which I think you missed.

[StarPD]

I know the timing can be bumped . I have a timing light but just dont know what notch on the crank pulley to go buy. Anybody advanced there timing a little. Would I get some better milage out of the car? I get around 350 miles out of the tank now. I would like to squeeze a little more power out of her also.

Older V-8s responded well to moderate static timing advance over factory. The amount depended n the kind of motor, and even each individual one. What we used to do was start at 3 degrees over stock, and increase 1 degree at a time after that, testing each time we increased it. We'd wait for a good hot day to do this, then after re-setting the timing, run the car up a long steep grade in top gear at WOT each time. When we got to where we got just the slightest almost imperceptible "tinkle", we backed the adjustment off 1 or 2 degrees and left it. That usually resulted in the optimum setting for performance AND fuel mileage.

My '94 "'t" model was re-set to 3 degrees over factory, and it gave me better throttle response and power, and I was getting 19-21 mpg in the city, 25 to 28 highway.

So, I had the timing on my new to me 2005 Q45 bumped by 2 degrees. BAD idea! For some reason, throtttle response and power went DOWN, and fuel mileage dropped! I had it re-set to factory, and it runs great now. Plenty of power, great throttle response, and I'm getting around 18 to 20 mpg mixed city/freeway driving, almost as good as my '94.

I suspect that I experienced exactly what Q45tech referred to, that factory is optimum already, and that bumping it made the knock sensors retard timing too much, and perhaps also changed fuel settings.

Bumping timing on F50/VK45s is apparently, at least in my case, not a good idea. Looks like in this case, the factory engineers knew what they were doing.

My suggesion is to NOT mess with ignition timing on F50s, but to try bumping it 2 or 3 degrees on G50s, and seeing how it works. Just be sure to check it like I used to on steep upgrade at WOT in top gear (no kickdown) listening carefully for the slightest "tinkle". If you get ANY, back off a degree or two. If you don't see any improvement in power, throttle response or fuel mileage, go back to factory setting. In no case would I ever recommend trying more than 3 degrees over factory.

[92Q45guy]

Exactly my point...which I think you missed.

Wow this thread is back? I ended up bumping it up a few last month. Drives great. I little more thottle response and I average 23 mpg now.

[db_autotek]

Yeah I guess it all depends on the veracity of the factory sensors.. i.e. the sensitivity of the knock sensors combined with the mathmatical curves of the factory timing curve + cam sensors. But it sounds like 2 or 3 deg over tdc is safe for G50s.. Maybe I'll give it a try. Here's the pun of the day: dont knock it till ya try it. Sorry.

[Q45tech]

Maximum effciency occurs WHEN 66% of the fuel mass is oxidized [burned] and the BMEP [peak pressure] occurs at 15-17 degrees after top dead center.

This is done by measuring the peak pressure vs crank angle on a lab dyno for every possible situation then creating equations which select ignition advance to correspond. These equations are modified by coolant temp sensor above 195F...............and all good wrok goes down the drain when you don't maintain coolant PRECISELY............this is an analog for head temperature........why sensor measures the coolant output just after heads.

Over advanced or a 2-3 degrees +- variation is not feelable by a driver, in that each degree at best changes peak torque by 1%.

Drivers cannot FEEL a +- 2% torque change even at WOT [+- 6 lb/ft at the highest]..................at cruise it would be +- 1 lb/ft UNLESS you overadvance and the KS removes 20% of torque which you can definitely feel.

Remember the ecu advances the add in advance until it senses knock and then backs off zeroing in on the optimium point every few seconds.

Lots of difference between iron cylinder heads and aluminum and wedge 2 valve heads and pentaroof 4 valve heads.

[StarPD]

Maximum effciency occurs WHEN 66% of the fuel mass is oxidized [burned] and the BMEP [peak pressure] occurs at 15-17 degrees after top dead center.

This is done by measuring the peak pressure vs crank angle on a lab dyno for every possible situation then creating equations which select ignition advance to correspond. These equations are modified by coolant temp sensor above 195F...............and all good wrok goes down the drain when you don't maintain coolant PRECISELY............this is an analog for head temperature........why sensor measures the coolant output just after heads.

Over advanced or a 2-3 degrees +- variation is not feelable by a driver, in that each degree at best changes peak torque by 1%.

Drivers cannot FEEL a +- 2% torque change even at WOT [+- 6 lb/ft at the highest]..................at cruise it would be +- 1 lb/ft UNLESS you overadvance and the KS removes 20% of torque which you can definitely feel.

Remember the ecu advances the add in advance until it senses knock and then backs off zeroing in on the optimium point every few seconds.

Lots of difference between iron cylinder heads and aluminum and wedge 2 valve heads and pentaroof 4 valve heads.

Agreed, with the exception that there is a small but noticable improvement in throttle response, again, depending on each different car, it's wear, and state of overall tune. Fortunately, or unfortunately, I am extremely sensitive to the slightst change in driveability and/or performance, including handling/tires. My techs all say I'm too picky, but I do notice thigs others don't. My imagination? Perhaps, but over the years, my perceptions have always proven to be accurate. Note that I admit that some changes for better or worse are almost imperceptible, but apparent to me at least.

Q45 tech, do you concur that bumping timing on at least most F50's is counterproductive? It was at least in my case. If so, do you suspect that it's because changing timing also alters other settings, or is it just because it causes the knock sensors to retard timing. When it does that, does it also alter the fuel settings on acceleration to further prevent detonation?

Not critical for me, since I learned it's not productive and am back to stock settings, but curious anyway.

[db_autotek]

Great info Q45Tech!! Just when I though I understood the inner demons of the ignition/timing concepts, LOL. Sounds like more trouble than it might be worth.. In the Miata I went from stock 12deg to 18-20deg and felt a big difference, but that car has much different physics, lol. 2000lbs versus 5000lbs. I agree a 2-3% increase wouldnt be noticable in a 5000lb car.

[Q45tech]

One thing to consider is that the cams become retarded from the crank as the chains stretch so periodic adjustment of CAS say every 100,000 miles is often necessary to maintain 15 degBTDC.

Unfortuntely you are assumming that the drivers bank has the same stretch as passenger bank.

[StarPD]

One thing to consider is that the cams become retarded from the crank as the chains stretch so periodic adjustment of CAS say every 100,000 miles is often necessary to maintain 15 degBTDC.

Unfortuntely you are assumming that the drivers bank has the same stretch as passenger bank.

Excellent tip.I'll keep it in mind, as I'm sure will others.Thank you.

Your thoughts on my questions?

[db_autotek]

Hmmm.. interesting. Q45tech, this might sound like a noob question, but does the VH have one CAS for each bank? Hmm I guess it would have to, maybe i just answered my own question. I couldn't find the article in q45.org. I assume it's in the "performance" tab that doesnt work?

[92Q45guy]

It only has one CAS sensor on the left bank.

[maxnix]

Only one crank, only one sensor, although it vicariously sensing the crankshaft position.

[PopPop]

Also keep in mind that the VH45DE VVT Sensors have an affect on your Timing also and all 90-94 VVT Sensors are not the same!

[Q45tech]

Because a chain doesn't stretch much in 70,000 miles and perfectionists would change the chain instead of misadjusting the CAS a degree.

The CAS cost $500+ how many do you want?

Think about the fact that old style rotor button distributors use to allow spark scatter of +- 5 degrees and modern CAS can resolve to 1 degree increments. Point of diminishing returns.

Modern engines use 2 NON ADJUSTABLE cam angle sensors and a NON ADJUSTABLE crank angle sensor plus extra sensors to determine if VVT is working. 5 vs 1 assembly