Although it has been suggested that some of the '05 HP difference is due to "variable exhaust timing", I'm wondering if anyone has actual confirmation of this. I find it difficult to believe that the Infiniti corp. website wouldn't mention this feature, if it indeed were on the '05. The ONLY reference to variable exhaust timing I've ever seen is on an old news release (and the various discussions on this forum). Some quotes for the Inifiniti website:
"A computer continuously fine-tunes the opening of the intake valves to feed the engine with more air at the perfect moment for combustion"
AND...
"DOHC, 4 valves per cylinder with microfinished camshafts and Continuously Variable Valve Timing Control System (CVTCS) for intake valves."

Then take a look at this:
"A pressure valve automatically opens the exhaust flow wide at higher rpm to boost high-end power output and gives the G35 the growl of a hot rod. When rpm is reduced, as during idle, the valve adjusts to hush the muffler to nothing more than a soothing hum"

So, my suspicion is that there has been confusion over this "variable exhaust valve", meaning simply an electronic bypass valve in the EXHAUST system. I think many on this board (and elsewhere) have mis-interpreted this to mean variable exhaust valve timing (i.e. exhaust camshaft timing).

Can anyone shed further light on this?
BTW: The fact that Infiniti thought it necessary to incorporate this bypass valve in the exhaust system seems to me to contradict several posts on this board stating that the stock exhaust system is NOT restrictive and that aftermarket exhausts do essentially nothing.

 

Barry (correct?)

I think the "electronic exhaust valve timing " truly is variable exhaust valve timing on the exhaust camshaft. I guess until someone can confirm with concrete evidence such as documentation or part no's or such we won't know for sure. Not sure how Nissan would be able to get 18 more HP for the 6MT G coupe and 13 more HP for the 35th Aniv. 350Z by sticking a bypass valve in the muffler. Here's a quote from Nissan's website.

"The 35th Anniversary Z��s engine has been modified using revised pistons and camshaft and the addition of electronic exhaust valve timing control. The same engine will also be available as standard equipment on the 2005 350Z Track model (6MT only), which also goes on sale in early 2005."

The fact they say revised camshaft in the same sentence with the exhaust valve timing control would lead me to beleive it is indeed variable timing on the exhaust camshafts.

Darren

 

If true it will be listed on the window sticker.

 

well, from nissan news web site

http://www.nissannews.com/infiniti/2...overview.shtml

For 2005, several modifications have been made including a new electronic exhaust valve timing, improved cooling and air flow and strengthening of several components, resulting in an increase of horsepower and torque to 280 horsepower (from 260 hp) and 270 lb-ft of torque (from 260 lb-ft) for models equipped with the advanced 5-speed electronically controlled automatic transmission with manual shift mode.

but the exhaust timing seems to only cover the boost from 260 to 280HP...
from the coupe section...

http://www.nissannews.com/infiniti/2...pe/index.shtml

The G35 Coupe 6MT model receives an additional 18-plus horsepower and a red line increase to 7,000 rpm compared to the automatic transmission-equipped G35 coupes� standard 280 horsepower and 6,600 rev limit, bringing its power to 298-horsepower. The extra power comes from the addition of electronic exhaust valve timing and numerous structural improvements to the engine block. Torque is rated at 270 lb-ft for the G35 Coupe and 260 lb-ft for the G35 Coupe 6MT.

so nissan does mention it on their web site...

Gary K

 

I checked under the hoods at the dealer - 6MT cars have intake and exhaust timing, 5AT's only have intake timing.

It is obvious when you look at the front of each cylinder head.

I was surprised the site didn't mention this as well... Maybe they feel if people know it would detract from the 5AT's stature??

Who knows!

 

Quoted directly from the Nissan Press release:

For 2005, several modifications have been made including a new electronic exhaust valve timing, improved cooling and air flow and strengthening of several components, resulting in an increase of horsepower and torque to 280 horsepower (from 260 hp) and 270 lb-ft of torque (from 260 lb-ft) for models equipped with the advanced 5-speed electronically controlled automatic transmission with manual shift mode.

For the AT cars, the HP has been increased by the addition of the Exhaust Variable Valve timing. This is not just some marketing BS. I've driven the 04 5AT sedan and now we bought my wife the 05AT. Havnig driven them both, I can honestly tell a difference in the stock sedans back to back. Just my $.02

 

I believe that the timing on the intake valves on our engines is continuously variable, not the exhaust valves. I have no proof of that except that on our VQ engine specs, and on the M45/Q45 engine specs (the VK engine), there is notation to that affect.



This reference refers to the valve in the exhaust (at the muffler) that regulates flow by opening and closing a valve. This feature has been on the Sedan from day one.
My understanding of this is that by restricting flow, torque and thereby performance, is enhanced, while allowing a qieter, smoother operation at low performance rpm's. High performance operation allows maximum flow, thereby maximum performance.
That valve may have been modified on later version/year Sedans but to me the principle is the same.

In a recent discussion here, it was suggested that the extra power in the newer VQ's was realized from further tweaking the ignition timing, intake valving in the ECU, along with intake flow, and exhaust flow.
I don't know if any of that was based on any fact, but perhaps Q45Tech can shed some light on it for us.

C.

 

I don't beleive the '05 AT cars have variable valve exhaust timing. But then again I could be wrong.

 

That is correct. Only the MT models (Sedan and Coupe) will have the added Exhaust Variable Valve Timing.

For those that are still confused, this has been clearly outlined in one of the *official* Nissan/Infiniti press-release. Some of the lines quoted above are refering to the variable flow muffler that's standard for all sedans.

I was also able to confirmed the above by cross referencing the '05 Engine/ECU service manual.

Finally ... these are the cold hard facts:

For '05 model years ...
- all 6MTs (sedan and coupe) rated at 298hp and have variable valve timing at the Intake AND exhaust side.
- all 5ATs (sedan and coupe) rated at 280hp and have variable valve timing at the Intake side ONLY. The previously detuned 5AT sedan now finally enjoys the same ignition timing maps as the rest of the family ... accounting for the uprated hp.

For '04 model years and prior ...
- all MTs and ATs have variable valve timing at the Intake side ONLY.
- AT/MT coupe and MT sedan have identical ignition timing maps (which btw are also identical to the 350Z ignition maps). This group is rated at 280hp. The MT sedan was never officially rated at 280hp.
- AT sedan has detuned timing maps. It is rated at 260hp.

 

Why would they "detune" the timing maps? What is the advantage to the 5AT dirver? They wouldn't cut performance just make the MT look better... That would hurt overall sales of the vehicles.

So why would you want a detuned map???

 

Clint, thanks for the clarification and verification. Your post should definitely be a sticky so that there won't be a billion threads on this subject.


IMO I think they did cut the performance of the AT to make the 6MT look better. In general, a auto enthusiast is going to want to go for a standard transmission over an auto. Plus most of the auto mags like C&D, Road&Track, etc. are going to do tests with the 6MT for their articles. For the sedan in the '03 and '04 model years, since the engines were exactly the same, the way to differentiate the cars was to detune the auto a bit on the ignition maps. But for '05, since the 6MT has a different engine per se with the new variable valve exhaust timing, they didn't need to detune the AT anymore. Overall this strategy is not going to hurt sales. Even if the 6MT was 30+ more hp than the auto, most buyers would still get the auto. It's just a fact that only a small percentage of the customer base is going to look for a manual transmission.

 

Your welcome dklau33.
btw ... I just figured out that dklau is your first initial, middle inital, and last name. I use to read it as 'De-Claw' ... thought may be ya didn't like cats or something .



Cleverclaire,
That is better answered by the Nissan/Infiniti marketing folks.
It should come as no surprise to you however. Too often, corporate marketing strategy goes against the thinking of the general public and specially true to the enthusiasts (like yourself and I) that represents only the top 10% of the buying population. I agree detune is lame, but business is business and there are bigger fish to fry. By simply participating in this topic (as well as knowing how to turn on a PC and find this site) you are automatically NOT the targetted Joe Schmoe and Jane Doe that comprise the bottom 90%.

The MT sedan was a very special case. Nissan/Infiniti could have easily chose to leave the MT sedan detuned, but according to my 'contact' ... it remained such a low forecast in their planned production, they've decided to make a gem out of it (no detune). With the pressure from the new Acura (TL) equipped with 270hp standard, they now have no choice but to also bless it with 280hp.

But don't frett just because you've got a 'detuned' AT sedan. It only takes Techno Square 15-minutes to erase what Nissan did and give you back that 20hp and then some. The down side is a 600-dollar hole in your wallet.

 

Haha... yeah, people on the club3g.com (3rd Gen Eclipse) boards thought that too until I told them. I know, I know, my sn is unoriginal but thats the email prefix I got when I was in school and it just kinda stuck. Oh well. No discrimination against cats here.

 

From the nissan press release:

For 2005, several modifications have been made including a new electronic exhaust valve timing, improved cooling and air flow and strengthening of several components, resulting in an increase of horsepower and torque to 280 horsepower (from 260 hp) and 270 lb-ft of torque (from 260 lb-ft) for models equipped with the advanced 5-speed electronically controlled automatic transmission with manual shift mode

From what I understand by what they've wrote was that the electronic exhaust valve is not referring to the valve in the muffler, but if you read carefully it states that it has Electronic Exhaust Valve Timing which has been added according to the last sentance the 5 speed AT.

Just from interpretation they are indicating that it is NOT detuning and infact the added feature that they gave the 350Z's just brought over into the Sedans. I'm not trying to start an argument, but I believe that it is clearly stated that the 5AT got more HP due to the addition of Variable Exhaust Valve timing.

 

That's a good point but more of a bad editing job on Infiniti's part. Read the following.

This statement clearly states the additional power of the 6MT coupe comes from the addition of the electronic exhaust vavle timing that the AT coupe does not.

The statement regarding the sedans was a bit poor and should have been more clearly seperated. It just wouldn't make sense to give the '05 Sedan AT, the '05 Coupe/Sedan 6MT the variable exhaust timing, but not give it to the '05 Coupe AT. That's just a waste of money on Infiniti's part. Anyways you can trust that THX723's cold hard facts are indeed the facts. Only the '05 6MTs got the variable valve exhaust timing. In fact it was verified by him looking in the '05 Service Manual.