Re-Tuning G35 engines to run on lower Octane

[!979TransAm]

Good explanation Adren, sounds like your an engineer of sorts, so what kind of real life power loss are we talking? Percentage?

Sentient, air foilers go behind the wheel well and spoilers in front. Concept being that they will smooth air flow around the wheels to prevent turbulance. Look at the spoilers on this trans am, the foilers are behind the wheels and spoilers in front.



Also notice the air extractor on the fender. It allows air to exit the engine bay, preventing the car from lifting. You really notice lift at higher speeds but not with the air extractors. The G is equipped with a comparable idea, the plastic underside shields the air away and preventing it from building up.

[Sentientbydesign]

Very interesting. Thank you for the picture and explanation.

[rn79870]

adren77

Your post and explanation is interesting because this is precisely the results that I have experienced with my G using regular 87 octane. Many G owners have posted getting very poor mileage using premium fuel and driving their vehicles hard.That has not been my experience. Day to day I get between 22 and 24 MPG with up to over 28 MPG on long trips. My 50 mile one way commute is mostly on cruise control between 70 - 75 MPH. There is no need for me to push my vehicle as traffic is light in the early morning & I usually shift between 2k & 3k rpm. Most of the $ssholes that clog our roads are not up yet. So I guess the point is that we can have our cake and eat it too, it just depends on how you want to drive your G

Telcoman

telcoman,I googled 91 octane vs. 87 octane mpg and got a lot of information, much of it supporting the claim that you would get better mileage from the 87 octane as it contains more energy. This goes against my gut feelings and the way I understand it, but there is quite a bit of authority supporting this premise. Maybe it is worth a little test on my part.

[zozoka1212]

My cars love the cooler weather!!! Feels faster.But, my tires do not. They just want to spin.

Humidity may be clogging up your paper air filter.

You need an X. No spinning tires.

zozo

[rn79870]

You need an X. No spinning tires.

zozo

I think I've got it now....



This close???

[zozoka1212]

LMAO

zozo

[C-Kwik]

C-Kwik...

The belows in the intake tubes are not there to reduce the vibrations/noise.

The reason for the belows is to induce turbulence. Turbulence plays a key role in the combustion dynamics inside an engine. More turbulence inside the engine, the better! Engineers try to induce turbulence inside the engine at every possible opportunity, and intake runners is one way.

The reason why turbulence inside the engine is important has to do with the combustion characteristics inside the chamber. Turbulent air will cause the flame front to propagate faster!!! We want the flame front to propagate as fast as possible. Faster flame front = faster combustion inside the chamber => less chance of knocking to happen => means we can get higher compression ratio => higher power + efficiency. Also faster combustion means the engine comes closer to having "constant volume combustion" (just as in the Otto cycle)... which will yield higher thermal efficiency.

Turbulence in the intake will cause more drag which is a negative side effect, however in this case, it is greatly outweighed by the positive gain explained above.

Uhh? While the right amount of controlled turbulence in the combustion chamber is a good thing, the bellows in an intake are way too far from the combustion chambers to actually be effective in adding any turbulence in them. Simple swirl control valves would be much more effective and provide more controllable results at different RPM's than some bellows that might prove to be only a minor restriction that exists a good foot in front of the throttle body, the plenum and the runners. It would be likely that any turbulence the bellows might induce would have been dissipated by the time it goes through each part of the intake.

The turbulence you speak of is really desirable once the fuel is mixed with the air. So at or just before the ports would be the ideal place for this turbulence to be added. Some motors offset the openeing events of each intake valve to induce some level of swirl. But any turbulence prior to this point would really just be a restriction to flow.

[Jacko3]

Telcoman:

Nice conclusion---how then do we drive the G-35? Remember, i had asked that question on another topic?

From my experience so far, my car is getting exceptional gas mileage for the power output. My car is burning less gas now, then before I installed all the mods. Of course I use Mobi 5w-30 synthetic. And the mods I have on are Mrev2, JWT Pop Charger, 5/16" spacer, and Stillen Exhaust. I also use 93 Octane.

My car only drinks a modest amount of gas when i push the car. The car is now so fuel efficient especially in the 4th and 6th gears, usually between 3K and 4K RPM. However, i get the best mileage in the 6th gear at or below 3K RPM.

In fact, I don't look to often at the gas gauge anymore because the car is now using gas in a manner I would find acceptable for a V-6. I am now amazed at how fuel efficient a G-35 can be when al the mods are installed and when all the fluids running through the car are made of synthetic. This is why I am going to change my differential and transmission oil to synthetic, to further increase its fuel efficiency.

Until anyone has the money to buy a supercharger, which I am looking forward to buying someday, my advice is to mod out your G-35 and change your oil, transmission, and differential to synthetic fluids. The Stillen TD Cat-back exhaust alone is lighter than the OEM exhaust, and thus saves you some gas. I am also looking at changing the drive pulleys to non-underdrive unorthodox pulleys, if I don't get the money I need to buy a vortech supercharger. Again, the lightness of the non-underdrive pulley would shave some weight from the front part of the car.

I am also amazed at how inefficiently the G-35 was built given all I am experiencing with the changes I am doing to the car. It would also seem reasonable to buy those lighter after-market rims as well. I think shaving off any excess weight from the G-35 does improve performance, handling, and fuel economy.

I cannot figure out for the love of Jehova why Infiniti did not do these simple things to give the customer what they need. Of course I understand the noise issue with the exhaust. Was infiniti trying to skimp on costs or are the materials they used on the car really better than the after-market parts?

I truly beleive Infiniti intended for the G-35 to be modified by the customer for better handling, performance and efficiency. Time and time again, as i visit the philosophy behind the car's design, I see nothing but modifications. So, why Infiniti?

[!979TransAm]

What makes the plenum biased to the rear cylinders?? Is it leaning back?? could a beveled spacer help to fix that?? Could be a simple fix.

No idea on the turbulance you guys talk of, I'm not in my core classes yet for engineering, taking some general credits. I would think though a smoother intake would allow better airflow into the car and I'm sure the internally the motor does enough mixing.

Something else to think about, Gasoline burns more effectivly when atomized. Any way to do that? I do know some guys in australia are making more power and better economy by converting cars to LPG. LPG easily atomizes and burns efficient, yeilding higher compression which is the easiest way to increase power

[telcoman]

Telcoman:

Nice conclusion---how then do we drive the G-35? Remember, i had asked that question on another topic?

From my experience so far, my car is getting exceptional gas mileage for the power output. My car is burning less gas now, then before I installed all the mods. Of course I use Mobi 5w-30 synthetic. And the mods I have on are Mrev2, JWT Pop Charger, 5/16" spacer, and Stillen Exhaust. I also use 93 Octane.

My car only drinks a modest amount of gas when i push the car. The car is now so fuel efficient especially in the 4th and 6th gears, usually between 3K and 4K RPM. However, i get the best mileage in the 6th gear at or below 3K RPM.

In fact, I don't look to often at the gas gauge anymore because the car is now using gas in a manner I would find acceptable for a V-6. I am now amazed at how fuel efficient a G-35 can be when al the mods are installed and when all the fluids running through the car are made of synthetic. This is why I am going to change my differential and transmission oil to synthetic, to further increase its fuel efficiency.

Until anyone has the money to buy a supercharger, which I am looking forward to buying someday, my advice is to mod out your G-35 and change your oil, transmission, and differential to synthetic fluids. The Stillen TD Cat-back exhaust alone is lighter than the OEM exhaust, and thus saves you some gas. I am also looking at changing the drive pulleys to non-underdrive unorthodox pulleys, if I don't get the money I need to buy a vortech supercharger. Again, the lightness of the non-underdrive pulley would shave some weight from the front part of the car.

I am also amazed at how inefficiently the G-35 was built given all I am experiencing with the changes I am doing to the car. It would also seem reasonable to buy those lighter after-market rims as well. I think shaving off any excess weight from the G-35 does improve performance, handling, and fuel economy.

I cannot figure out for the love of Jehova why Infiniti did not do these simple things to give the customer what they need. Of course I understand the noise issue with the exhaust. Was infiniti trying to skimp on costs or are the materials they used on the car really better than the after-market parts?

I truly beleive Infiniti intended for the G-35 to be modified by the customer for better handling, performance and efficiency. Time and time again, as i visit the philosophy behind the car's design, I see nothing but modifications. So, why Infiniti?

Jacko3

Can you provide some MPG numbers? What MPG were you getting prior to your mods and what MPG are you getting now?How does the high heat & humidity of the Florida summers compare with your MPG during the winter?

Telcoman

[Q45tech]

Since EPA MPG tests are conducted between 50 and 70 mph why would any engineer waste time at speed beyond these. At least the range has been expanded from 55 mph limit used until 2008 test.

Displacement times rpm is 90% of the equation weight only applies to acceleration.

When displacement is rolled back to 1.9999999 liters as it was in the G20 of yore fuel sipping will return.

[C-Kwik]

What makes the plenum biased to the rear cylinders?? Is it leaning back?? could a beveled spacer help to fix that?? Could be a simple fix.

If the data that the guys who make spacers and plenums publish are accurate, their speculations are that the tapered plenum shape restricts the flow of air to the front cylinders as the plenum is narrower there. Spacers and aftermarketupper plenums are supposedly the solution for this...

[!979TransAm]

So if that were the case wouldn't they build a tapered spacer, so to counter act the bias? Instead of just a flat one it makes more sense.

[Jacko3]

Telcoman:

I don't have exact numbers prior to mods installed. Anyway, engine is still new (5,000 miles) while rest of car is about 17K miles. However, prior to mod I was always going to the gas station to fill up all the time---my wallet was leaking cash like a gambler in a casino.

What I did was to ensure that my gas never went below a quarter tank. Then, I monitored how regularly I was going to the gas station to fill up. Well, at the time before mods I was using blend from Castrol, which did help with reduced noise and smoother acceleration. Fast forward a week after installation, and now I am smiling very happily--not worried anymore about gas.

The car is seeping gas like a 4 cylinder--not bad for a G-35--remember, I have another car that is a 4-banger manual transmission whishc I compare it to. In fact, the fuel measuring device on the GPS at 60 miles per hours read something beyond 26 miles per gallon. I had to reset it quickly because I thought it was an error. Give me this weekend to monitor it some more and I will post several numbers based on RPM and speed. This time I will use cruise control at varying set speeds to determine gas consumption with mods. I hope this helps. I am extremely pleased with the gas consumption at the moment, given that it is a V-6. I am also getting this improved gas mileage at higher RPMs with the mods than the slightly less RPM I received without the mods, given the same pedal input.

Only time it drinks gas is when I stomp on the gas pedal for hard driving---it doesn't matter the gear or RPM. The gas consumption is real and immediate. You will see the gas gauge needle move. So, I feel I am in total control of my gas usage now than at anytime before. However, I am finding that the 5th gear of the 6MT coupe is very inefficient. When I get to the 5th gear, I burn gas a lot more than in any other gear. So, now with the mods, I try to quickly move from 4th gear to the 5th gear and then the 6th gear. I enjoy the 4th and 6th gears the most, this is with the Stillen exhaust. With the OEM exhaust, without the mods, I enjoyed the 5th gear the most, eventhough it burned a lot of gas. But the 3rd gear burns as much gas but at much higher RPMS of about 5 - 5.5 K RPM. below this, the 3rd gear is okay and good. This is my experience so far with the car.

My mechanic also increased my timing by 2 degrees and the RPM at idling increased by a small and insignificant amount of 50 RPM. What this is doing is that it stops the RPM needle from dropping back to zero very quickly when I am shifting. Does anyone know what this slight increase in timing and RPM does for a car with high compression? My mechanic says it helps with immediate acceleration and power.

Let me note that the first three days of using the synthetic oil, I saw no difference in improved gas mileage as my car was shifting from a synthetic blend to a full synthetic oil. After about 3 days of hrad driving, I began to notice the difference in gas mileage. As at today, the gas station is not my friend anymore as it used to be. Any thoughts?

[telcoman]

Telcoman:

I don't have exact numbers prior to mods installed. Anyway, engine is still new (5,000 miles) while rest of car is about 17K miles. However, prior to mod I was always going to the gas station to fill up all the time---my wallet was leaking cash like a gambler in a casino.

What I did was to ensure that my gas never went below a quarter tank. Then, I monitored how regularly I was going to the gas station to fill up. Well, at the time before mods I was using blend from Castrol, which did help with reduced noise and smoother acceleration. Fast forward a week after installation, and now I am smiling very happily--not worried anymore about gas.

The car is seeping gas like a 4 cylinder--not bad for a G-35--remember, I have another car that is a 4-banger manual transmission whishc I compare it to. In fact, the fuel measuring device on the GPS at 60 miles per hours read something beyond 26 miles per gallon. I had to reset it quickly because I thought it was an error. Give me this weekend to monitor it some more and I will post several numbers based on RPM and speed. This time I will use cruise control at varying set speeds to determine gas consumption with mods. I hope this helps. I am extremely pleased with the gas consumption at the moment, given that it is a V-6. I am also getting this improved gas mileage at higher RPMs with the mods than the slightly less RPM I received without the mods, given the same pedal input.

Only time it drinks gas is when I stomp on the gas pedal for hard driving---it doesn't matter the gear or RPM. The gas consumption is real and immediate. You will see the gas gauge needle move. So, I feel I am in total control of my gas usage now than at anytime before. However, I am finding that the 5th gear of the 6MT coupe is very inefficient. When I get to the 5th gear, I burn gas a lot more than in any other gear. So, now with the mods, I try to quickly move from 4th gear to the 5th gear and then the 6th gear. I enjoy the 4th and 6th gears the most, this is with the Stillen exhaust. With the OEM exhaust, without the mods, I enjoyed the 5th gear the most, eventhough it burned a lot of gas. But the 3rd gear burns as much gas but at much higher RPMS of about 5 - 5.5 K RPM. below this, the 3rd gear is okay and good. This is my experience so far with the car.

My mechanic also increased my timing by 2 degrees and the RPM at idling increased by a small and insignificant amount of 50 RPM. What this is doing is that it stops the RPM needle from dropping back to zero very quickly when I am shifting. Does anyone know what this slight increase in timing and RPM does for a car with high compression? My mechanic says it helps with immediate acceleration and power.

Let me note that the first three days of using the synthetic oil, I saw no difference in improved gas mileage as my car was shifting from a synthetic blend to a full synthetic oil. After about 3 days of hrad driving, I began to notice the difference in gas mileage. As at today, the gas station is not my friend anymore as it used to be. Any thoughts?

Jacko3

Forget what displays on your Nav.1- Fill your tank early in the morning when it is still cool. Add a little more after the pump shuts off to round off the price.2- Set your odometer A to zero3- Drive until the fuel light comes on which should be around 350 miles and fill the tank as in step one.It will probabily take about 16 gallons with 4 gallons left in the tank.

miles traveled divided by gallons to fill the tank equals MPGFor example 350 miles divided by 16 gallons = 21.875 MPGI am kind on anal on my mileage and I write down everything everytime I fill up including the price per gallon.After a few times of doing this you will have an idea of how your G is performing just by noticing how many miles you've traveled when the fuel gauge reaches the 3/4, 1/2, and 1/4 marks. If you manage to go 400 miles before the fuel light comes on & you fill up taking the same 16 gallons your MPG is 25This is the only accurate way to determine your MPG. I keep a cheap calculator in my glove box.

Let us know

Telcoman

[adren77]

Uhh? While the right amount of controlled turbulence in the combustion chamber is a good thing, the bellows in an intake are way too far from the combustion chambers to actually be effective in adding any turbulence in them. Simple swirl control valves would be much more effective and provide more controllable results at different RPM's than some bellows that might prove to be only a minor restriction that exists a good foot in front of the throttle body, the plenum and the runners. It would be likely that any turbulence the bellows might induce would have been dissipated by the time it goes through each part of the intake.

The turbulence you speak of is really desirable once the fuel is mixed with the air. So at or just before the ports would be the ideal place for this turbulence to be added. Some motors offset the openeing events of each intake valve to induce some level of swirl. But any turbulence prior to this point would really just be a restriction to flow.

My bad, When you said "bellow" i thought you were talking about Intake runners.

Regardless, turbulence would not be dissipated throughout the rest of the intake... instead it would be amplified even more. It is true what you said about offsetting the intake valve events to create swirl, however swirl is not exactly turbulence (thought it does contribute to it).

Uhh? While the right amount of controlled turbulence in the combustion chamber is a good thing, the bellows in an intake are way too far from the combustion chambers to actually be effective in adding any turbulence in them. Simple swirl control valves would be much more effective and provide more controllable results at different RPM's

What you said here really doesn't make sense. More controllable results? Right amount of turbulence? We don't want to control turbulence in the engine, we want to get as much of it as possible, always. More turbulence = higher fuel conversion efficiency. The reason many cars suffer at low RPMs is because of low level of turbulence at low RPM.

[G_whizz]

CK is probably one of the most helpful and knowledgeable people here at NICO.

Play nice..

[SVTCOBRA]

telcoman, I was told a long time ago that you should never run out of gas. In addition, you should never run low on gas cause you start sucking up trash at the bottom of the tank. Anybody else heard this???I never go below 1/4 of a tank. Most of the time I refill at 1/2 tank cause I heard that you loose more to evaporation the less you have in the tank. Somebody else made a good point about filling up early in the morning.....isn't the gas in a tank in the ground which would have a more constant temp?? Making it really not matter??

[Jacko3]

Telcoman:

I just went out for a spin the ride. I averaged 23.9 miles per gallon for a 40 mile ride with my G-35 coupe. This was in 6th gear and no more than 3K RPM. The least gas mileage I obtained was 22.5 MPG. Now that is good for a new engine with about 5K miles on it. New engines tend to be very inefficient. I only hit 24. 4 MPG once.

However, I also noticed that the G seemed to get better gas mileage at between 80 - 85 miles per hour.

I then decided to run the car a little hard to see how the MPG would change. Well, well, well, the car was producing at its very worst, 20.4 MPG, and this was when I revved up a couple of times above 5,500 RPM. I was impressed. Remember, I have my timing set 2 degrees above normal timing and my RPM is now at 850 RPM instead fo the usual 800RPM at idle. I really love the MPG of this car now. Also remember that all this is with the mods on (Mrev2, spacer, JWT Pop Charger, and Stillen Intake).

On top of that, the synthetic is making the car seem cooler than normal.

One problem I did notice this evening about the G-35 is that the OEM clutch gets tired when it gets heated due to many revvs and take-offs. After it cools, it is good to go. My mechanic mentioned this but I did not understand until this evening after many revs and take-offs. I beleive the wearing of the OEM clutch starts when the clutch gets too heated. In this regard, I will suggest to anyone to replace their clutch with after market sports clutch if they can or if they can afford it. I intend to do the same when the time comes. Of course if you intend to install an SC, this would be an even better idea.

So, what do you think? Remember, I am totally in touch with any car I drive. I even feel the smallest pebble the tires go over.

[C-Kwik]

You really shouldn't try to argue points you don't understand.

Perhaps. Lets just assume I have no idea what I am talking about. And that's perfectly possible. But feel free to argue with this guy then:

http://www.fuelsaving.info/turbulence.htm

Feel free to read the whole article, but I'll quote some excerpts of particular interest to this discussion.

"Unfortunately turbulence is a very short-lived phenomenon; turbulence is generated whenever air flows quickly past a stationary surface, but rapidly decays away through viscosity once the bulk air speed reduces."

"Since generating more swirl requires more restrictive inlet ports, values around 0.5 to 1.0 are usually found in production engines."

"But let's ignore all that for a moment and imagine that adding more turbulence does help fuel economy. Can a "bolt-on" device really increase the turbulence in the cylinder? The simple answer is no - the flow in the intake system is already highly turbulent at part load, with air speed past the throttle in the region of 200-300 metres/second. A device upstream of the throttle may make the air swirl there, but the swirl pattern will be destroyed as the flow squeezes past the throttle blade."

Enjoy.

[adren77]

Perhaps. Lets just assume I have no idea what I am talking about. And that's perfectly possible. But feel free to argue with this guy then:

http://www.fuelsaving.info/turbulence.htm

Feel free to read the whole article, but I'll quote some excerpts of particular interest to this discussion.

"Unfortunately turbulence is a very short-lived phenomenon; turbulence is generated whenever air flows quickly past a stationary surface, but rapidly decays away through viscosity once the bulk air speed reduces."

I am guessing this is suppose to prove to me that turbulence dies inside the intake as you mentioned previously. Let me explain why this quote does not support your argument. He says that "[turbulence] rapidly decays away through viscosity once the bulk air speed reduces." This statement is true, however it does not pertain to the intake system. The "speed" of air does NOT reduce inside the intake. Assuming that the engine is running at a constant speed, then air is entering the intake system at the same rate it is exiting. This is the simple continuity equation most people see the first day of fluid dynamics class. Anyways, this means that the inlet mass flow rate = outlet mass flow rate. Assuming that the runner has the same diameter at both ends, then the speed of air entering it will = speed at exit (which right at the intake valve). Since the speed is constant throughout the runner, the turbulence does not "rapidly decay" but instead it increases! If you do a simple calculation, you will see that inside the tube Re >>2300 which is when it transitions from laminar flow to turbulent. This means that the air entering the the chamber is already turbulent. It does not have to be swirling, but it is still turbulent. The two terms are not synonymous.

"Since generating more swirl requires more restrictive inlet ports, values around 0.5 to 1.0 are usually found in production engines."

How does this pertain to what I was talking about? Yes generating more swirl does require more restrictive inlet ports... which is counter productive. This is why you would like to have turbulence even before it reaches the chamber, so you don't have to restrict the flow too much to cause swirl.

"But let's ignore all that for a moment and imagine that adding more turbulence does help fuel economy. Can a "bolt-on" device really increase the turbulence in the cylinder? The simple answer is no - the flow in the intake system is already highly turbulent at part load, with air speed past the throttle in the region of 200-300 metres/second. A device upstream of the throttle may make the air swirl there, but the swirl pattern will be destroyed as the flow squeezes past the throttle blade."

If by "bolt-on" device he is talking about the intake runners... well then he is plain wrong. Intake runners can (and do) cause turbulence. If you ever looked inside the intake runners you will find the surface is not flat, but has bumpy/dent pattern... This is done to increase turbulence! If you look at your headers at the exhaust... the surface will be smooth and have no such pattern. This is done to reduce turbulence and this less drag (Less back pressure).

Then he talks about how flow is turbulent at part load. Yes this statement is true. Then he says how the throttle will "destroy" the swirl pattern. Yes this may be so, but once again this does not destroy the turbulence. In fact, the throttle will only induce more turbulence by tripping the boundary layer.

Look at video of the flow through the tube. You can't really tell if the swirl is destroyed but you can tell that the flow gets more turbulent down the stream.

Turbulence is one of the most complicated and least understood topics in all of engineering. Excuse me if I trust a source a little bit more reliable than "Tony's Website"

[!979TransAm]

I can't really understand the real benefit of of turbulence outside of the cumbustion chamber? I mean wouldn't turbulence lower the amount of air that could reach the cylinder because it slows the velocity of air.

I'm pretty sure people port heads to reduce turbulence and increase airflow SO would that count as proof?

[Sentientbydesign]

Adren

I have to disagree with your assesment of turbulence decay.

A perfect example is a river. Rocks and other objects may introduce turbulence into the water, but the water will return to a calmer state past those turbulence inducers.

TransAm also brings up a valid point. People wouldn't port and polish their heads if the turbulence was such a benefit. It is true that there are areas that are left "bumpy" intentionally for turbulence, but to say that massive accumulations of turbulence will improve efficiency is sadly misguided. One of the biggest issues with classes are that many of the topics are cover singularly and not in conjunction with other systems. A perfect examle is university Physics. The first semester pretends that there are such things as mass-less pulleys and frictionless surfaces. It is not until further in the series that those systems are added back in.

The "bolt-on" device is more likely a Tornado. It's a piece of sheet metal that supposedely swirls the intake air allowing for better fuel economy AND HP.

Jacko,

Using the navigation to estimate fuel economy is a nice guideline, but unless you use Telcoman's suggestion, your estimates will most likely be wrong. Also, a 40 mile drive is a poor test for fuel economy. Anything under half a tank is kind of a joke.

Saying that pushing your car resulted in a minimum MPG of 20.9 is laughable. When you accelerate, your MPG drops significantly sometimes under 10 MPG.

Also, please be careful doling out advice regarding an aftermarket clutch. The factory clutches are typically built for longevity. They also have a smoother bite to them. Going with an aftermarket clutch will make the car less easy to drive especially if coupled with a single mass lightweight flywheel which will make the pedal much stiffer and engagement will be much more touchy (this is from experience, not just speculation).

There are probably numerous reasons why Infiniti chose to design the G35 the way they did.

One reason is because it would give NISMO a large sum of business. Another reason is definately noise. The drivetrain is already louder than an F250 adding a loud exhaust note and significant vibration from under the hood would turn away a lot of buyers. Especially since there are quite a few who bought the car for looks, not performance.

How do you validate that 5th gear is inefficient? I stongly doubt that it is heavier and it is definately shorter than 4th.

SVTCobra,

I don't see how you could be sucking up crap from the bottom after your tank got low. The fuel pump should be pulling from the bottom of the tank at all times. Is it possible that the junk you're referring to is floating on the surface of the gas and when it gets too low you'd suck it up then?

[SVTCOBRA]

SVTCobra,

I don't see how you could be sucking up crap from the bottom after your tank got low. The fuel pump should be pulling from the bottom of the tank at all times. Is it possible that the junk you're referring to is floating on the surface of the gas and when it gets too low you'd suck it up then?

Maybe so. Just something I was told by a mechanic friend when I was a teenager and I've always kept 1/4 tank because of it. Will have to ask another mechanic I know about it. I just thought somebody else would have heard of this......

[C-Kwik]

I am guessing this is suppose to prove to me that turbulence dies inside the intake as you mentioned previously. Let me explain why this quote does not support your argument. He says that "[turbulence] rapidly decays away through viscosity once the bulk air speed reduces." This statement is true, however it does not pertain to the intake system. The "speed" of air does NOT reduce inside the intake. Assuming that the engine is running at a constant speed, then air is entering the intake system at the same rate it is exiting. This is the simple continuity equation most people see the first day of fluid dynamics class. Anyways, this means that the inlet mass flow rate = outlet mass flow rate. Assuming that the runner has the same diameter at both ends, then the speed of air entering it will = speed at exit (which right at the intake valve). Since the speed is constant throughout the runner, the turbulence does not "rapidly decay" but instead it increases! If you do a simple calculation, you will see that inside the tube Re >>2300 which is when it transitions from laminar flow to turbulent. This means that the air entering the the chamber is already turbulent. It does not have to be swirling, but it is still turbulent. The two terms are not synonymous.

Are you still assuming the bellow is the intake runner? Last I checked we were discussing the effects of a turbulator ahead of the throttle and it's affects on the amount of turbulence in the combustion chamber. And between the bellows and the combustion chambers, there are many changes in volume (or cross sectional area) and direction. So speed is not constant.

If by "bolt-on" device he is talking about the intake runners... well then he is plain wrong. Intake runners can (and do) cause turbulence. If you ever looked inside the intake runners you will find the surface is not flat, but has bumpy/dent pattern... This is done to increase turbulence! If you look at your headers at the exhaust... the surface will be smooth and have no such pattern. This is done to reduce turbulence and this less drag (Less back pressure).

The rough surface energizes the boundary layer of air. Essentially causing air that would otherwise not be moving to be moving. Or to put it more simply, it reduces the boundary layer that isn't moving.

Then he talks about how flow is turbulent at part load. Yes this statement is true. Then he says how the throttle will "destroy" the swirl pattern. Yes this may be so, but once again this does not destroy the turbulence. In fact, the throttle will only induce more turbulence by tripping the boundary layer.

Please explain what you mean more clearly.

Look at video of the flow through the tube. You can't really tell if the swirl is destroyed but you can tell that the flow gets more turbulent down the stream.

The video also shows that there is much higher velocity gasses at the throttle as the air goes around the restriction in it's path of flow. The turbulence that ensues well past this point occurs as the velocity decreases. The higher velocity areas are going to direct and convert any turbulance or at least a significant portion of it into laminar flow.

Turbulence is one of the most complicated and least understood topics in all of engineering. Excuse me if I trust a source a little bit more reliable than "Tony's Website"

Absolutely, turbulence is not as highly understood as most other obsevable physics. But, I find it a bit hard to ignore someone with this type of background:

http://www.fuelsaving.info/biog.htm

But look. I'm not here to try and just win an argument. If you feel I am wrong and/or this "Tony" is wrong, then provide clear concise explanations as to why.

[Q45tech]

Why would you assume a mechanic or even a Master certified Technican knows anything about the DESIGN of an engine or how to make one better. For that you need those MS/Phd in Automotive Engineering.Those few thousand specilaists in the WORLD who actually design engines.

Most [many] aftermarket guys are in the same boat they create some dubious science then fake up some dyno graphs and razzle dazzle with promises to get yor money. They usually do create improvements but never meet or exceed expectations.

[rn79870]

Maybe so. Just something I was told by a mechanic friend when I was a teenager and I've always kept 1/4 tank because of it. Will have to ask another mechanic I know about it. I just thought somebody else would have heard of this......

I was taught that with the FI Fords that the electric fuel pump was in the fuel tank. And that the pump was lubricated by the fuel it pumped. If you ran out/low on fuel you ran the risk of burning out the pump. I never liked the idea of having an electric pump in the fuel tank. That made for the best anti theft device, splicing a on/off switch in to the power feed to the fuel pump and hiding the on/off switch. Engine would start, run about 1 1/2 seconds and die. Flip the switch back to on, and she would start right back up.

[Jacko3]

Sentientbydesign:

My engine was replaced due to oil consumption problems. New engine is superb and more connected to the transmission.

[Jacko3]

So, I have been used to speed since I was a kid. I probably would have become a race car driver, but, my parents wantd me to get an education. So, I just drive cars to see what they are capable of doing. I don't do doughnuts or burn outs. I might racxe, and I only do so after taking tin to account so many other factors like the state of my tires, how my body feels and is responding, how my car is responding on that day, the way the other driver is behaving--whether they are mature, complascent, or just reckless--I can tell from the way the driver seats in the car, a littel bit about their minds set, and the risks of getting a ticket.

For me, driving is not about holding a steering wheel and stepping on the pedals. It is a lot more involved than that. For example, each steering input, dependinig on the car, requires a certain level of braking if going fast. You can't apply the brakes the same way with different steering input.

Another example is when I am driving and I start smelling the clutch burning, at speeds in excess of 80 miles per hour, I hold down the clutch pedal for about a few seconds, while placing the stick in neutral. This way, you allow the clutch to dissipate heat for a few seconds before letting it go back to the fly wheel. Then, you go ahead and engage the gears again. All this is happeneing at high speeds.

I don't drive for luxury. I drive because it gives me much joy to know how a car behaves under different driving conditions, inputs, and mechanical conditions.

This is why I am always skeptical of those magazine remarks about each type of car's drining behavior. Very few of those magazine drivers drive their cars very slowly to see how it feels at slow speeds versus at high speeds. And by slowly, I mean 20 - 25 miles per hour for about 30 minutes. and then, stomp on the gas pedal to see how it behaves in instantaneous and unpredicatbale way. Of course, the tires and suspension will react to the instant request of power. And of course, you demand that power without stop until you reach a 100 miles per hour, and then you brake instantly back to 25 miles per hour and continue driving for another 30 minutes to see how the cooling system and transmission is behaving under such stresses. Manufacturers never write of this type of behavior when you buy a car. Drivers have to find this out by themselves.

The same is done in the rain and in the snow. In fact, I enjoy driving n the sno with my little car. I love loosing control of the car in the snow and then working hard to wrestle control back. I found my little nissan to be more capable in the snow and rain than my G-35. When it rains, my G-35 is locked up in the garage. I just love torturing cars. A good car will smile back at you when you torture it enough. Thats why i love my little Nissan becasue she has been tortured ofr years and she still holds up.

[Jacko3]

For those who car to know this, I have taken the liberty to drive a 2007 3.5 SE Altima Coupe manual transmission and a Honda Accord 3.5 V6 manual transmission coupe. The Honda Accord is a far higher quality car than the 3.5 SE Altima. The Honda Accord really raises serious questions about the soundness of buying an Acura TL. This Honda car really shines. And its handling characteristics is very close to that of the G-35, if you know what you are doing behind the steering.

I felt very afraid with the 17 inch Altima wheels. But the ALtima was more fun to drive. There isa big distinction between the G-35 coupe which the Altima Coupe tried to copy than there is between the Honda Accord and the Acura TL. The Honda Accord, clutch pedal felt too smooth and too perfect for a stick. I felt I was driving an automatic car. The interior is built of higher quality material than the Altima, but the buttons were totally scattered an unseemly to the eye. The altima's buttons were better arranged.

Just my 2 cents on another test drive.