Another question...

MclarenF1 · #1 03-15-2005, 01:27 PM

Oh yes, I have another question, but not one related to a mechanical problem...

It's a well known fact that the turbo Z had variable valve intake timing until 96, when that feature was removed. However, it's not clear to me whether NA Zs also had variable valve timing. If so, did they drop the variable timing on the NA in 96 too? Everything I've looked at says horsepower and torque for the NA were unchanged throughout the entire production period. Anyone heard otherwise?

k3smostwanted · #2 03-15-2005, 05:33 PM

Quote:

Originally Posted by MclarenF1

Oh yes, I have another question, but not one related to a mechanical problem...

It's a well known fact that the turbo Z had variable valve intake timing until 96, when that feature was removed. However, it's not clear to me whether NA Zs also had variable valve timing. If so, did they drop the variable timing on the NA in 96 too? Everything I've looked at says horsepower and torque for the NA were unchanged throughout the entire production period. Anyone heard otherwise?

you know, that is a damn good question. im sure it was dropped also because of the OBDII and emission regulations but it did have the same HP rating and the TT has a myth behind it that says it lost some HP. but the TT is a myth that it lost 20hp...i have seen a 96 TT pull the same WHP as a 95 TT, but the 96 made the power a little different when you compare the graphs. but i cant go off of this for a fact because the 96 i am referring to i saw posted on the net so i dont know for sure it was completely stock, but i seen the 95 numbers personally. maybe someone else has some more info..,..

Hodo · #3 03-16-2005, 12:55 PM

I dont belive they did. The only things changed on the NA were the cam profiles and the ECU mapping and electronics additions... like OBD2. Otherwise same car.

MclarenF1 · #4 03-16-2005, 04:28 PM

Quote:

Originally Posted by Hodo

I dont belive they did. The only things changed on the NA were the cam profiles and the ECU mapping and electronics additions... like OBD2. Otherwise same car.

Do you mean the NA did not have variable valve timing to begin with, or did they keep it, but with a changed cam profile? Thanks!

Zgringo · #5 03-16-2005, 04:33 PM

Quote:

Originally Posted by Hodo

I dont belive they did. The only things changed on the NA were the cam profiles and the ECU mapping and electronics additions... like OBD2. Otherwise same car.

Dead on Hodo, The N/A has a wider overlap on the cams, whereas the TT has a narrow overlap so as to not lose boost.

MclarenF1 · #6 03-16-2005, 04:55 PM

Whoa... Sorry that I'm a little confused. Maybe my brain is fried today. So ya'll are saying that that NAs always had variable valve intake timing, but just changed cam profiles from 95 to 96. Right?

I knew the NA and TT cams are different, but I wan't sure how so. I actually figured lift would be different too, but I guess there really wouldn't be any point in that. I suppose that explains why the TT idles just as smoothly as an NA. Learn something new every day.

k3smostwanted · #7 03-16-2005, 04:59 PM

Quote:

Originally Posted by Zgringo

Dead on Hodo, The N/A has a wider overlap on the cams, whereas the TT has a narrow overlap so as to not lose boost.

i think he was telling the difference between N/A years, not N/A vs. TT...but yeah, that is true like you said.

anyways, what was the reasoning behind dropping the variable valve timing on the TT in 96'??? thats what doesnt make sense, why would they drop it in the TT and not the N/A??? does it cause more emissions maybe and they couldnt get the TT to pass but they did the N/A??? explain further hodo...it doesnt make sense to me.

MclarenF1 · #8 03-16-2005, 05:10 PM

I'd figure the emissions on the TT would be higher than on the NA simply because it has to burn more fuel to keep up with the increased oxygen supply from the turbos under boost. I'm sure that's at least part of the reason. But on the other hand, that only explains why emissions from the TT are higher than on the NA. It seems like variable valve timing would, if anything, help pre 96 motors run more effeciently and burn cleaner than the 96 models without variable timing. You'd think it would have been the other way around... the car would pass emissions with timing but fail without. Maybe Hodo or Zgringo know if there's more to it than that.

Hodo · #9 03-17-2005, 08:17 PM

Actually the NA has higher emissions than the TT..... in stock form.

The NA relies heavily on its cats and O2Ss to get the mix right so this means it is constantly telling the computer to adjust everything from inject pulse to timing and retarding. TTs have the same issues but thanks to the turbos they are often getting more air into the mix to help burn off excess HCs in the system. That and the inharent higher exhaust temps with a turbo this also burns off excess fuel too. This is also why a great many of the European companies have small turbos or superchargers on their cars, not to make a great deal of power but to make them run more effeciantly.

Hope that helps a bit.

k3smostwanted · #10 03-17-2005, 10:44 PM

Quote:

Originally Posted by Hodo

Actually the NA has higher emissions than the TT..... in stock form.

The NA relies heavily on its cats and O2Ss to get the mix right so this means it is constantly telling the computer to adjust everything from inject pulse to timing and retarding. TTs have the same issues but thanks to the turbos they are often getting more air into the mix to help burn off excess HCs in the system. That and the inharent higher exhaust temps with a turbo this also burns off excess fuel too. This is also why a great many of the European companies have small turbos or superchargers on their cars, not to make a great deal of power but to make them run more effeciantly.

Hope that helps a bit.

so what was the reasoning for the loss of the variable valve timing in the TT and not the N/A??? i hate mysteries!!!

Hodo · #11 03-18-2005, 12:44 PM

Most likely cost.... nothing to do with performance. Remember this car as much as we all love it was made by a corperation they are out to make money if that means cutting things they see they dont need to meet standards then they will get rid of them.

k3smostwanted · #12 03-18-2005, 05:05 PM

Quote:

Originally Posted by Hodo

Most likely cost.... nothing to do with performance. Remember this car as much as we all love it was made by a corperation they are out to make money if that means cutting things they see they dont need to meet standards then they will get rid of them.

i guess, but how much are we really talking for nissan to keep the variable valve timing...

you would think it might take more money to remove it because then they would have to re-calibrate there production line and re-engineer the engine.

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