Eric

Ok

I realize the 2k2's have continuously variable timing on the VQ35, but anybody else notice the jump in acceleration at around 4000 rpm?

I find that if I am accelerating hard in third or fourth gear, there is a noticeable increase in power at around 4000 rpm.

Is this the engine switching over to the different intake path or the muffler opening that fancy little valve?

Jeff92se

iTrader: (82)

The new 3.5 VQ has a few new goodies.
1) Varible cam timing(as you mentioned)
2) Dual chamber capacity muffler(as you mentioned)
3) Varible volume intake manifold. Now since this is an on/off device, this is what you maybe feeling(theory)

I doubt it's the muffler. As I have one on my 3-gen and don't notice any additional "kick" when the other flap opens.

irvine78

iTrader: (2)

same with the 5th gen VQ30DE. it's two stage intake manifold(or something)..it really opens up at 3,500rpm...from there on..bye bye VTEC..

MaxRPM

iTrader: (1)

I get the same 4000 rpm surge as well but I also notice one at just over 3000 rpm, reminds me of my 300ZXTT, I would get a rush of power at about 3500rpm (full boost) and if it was a cold day I would break the rear wheels loose in first second and sometimes 3rd gear.

SteVTEC

Gen5 VQ30's open the secondary runners at 5000rpm. (see dyno charts)
Gen5 VQ35's open the secondary runners at something less than that...

...maybe it's 4000rpm. If so, that's probably what you're feeling.

BTW, I think Nissan officially calls this "CVTC" (Continuously Variable Timing Control) - they can't use "VTEC" since that's a registered Honduh trademark or something. It varies cam phasing but not lift, so it's most similar to Toyota's VVT-i system.

irvine78

iTrader: (2)

i just looked at my dyno...
although i feel much rapid rpm increase starting at 3,500rpm, my car's power doesn't really jump up at that rpm..it's just one hell of a smooth power curve all the way up to 204hp.

Jeff92se

iTrader: (82)

Why would they want to use VTEC whan Nissan's VTC is completely different than Honda's vtec system?

irvine78

iTrader: (2)

who cares when u can smoke'em both cold~

SteVTEC

True

irvine78

iTrader: (2)

didn't mean to disrespect ur Accord...Accords are nice...just not fast enough...

SteVTEC

It's just another way of doing things I guess.

Nissan already has the variable intake manifold so they probably didn't need to go all-out on the VTC for the VQ35. I bet future higher performance versions of the VQ35 for the 350Z and/or G35 (and the next Maxima) will have more advanced systems like Toyota's VVTL-i or Honda's i-VTEC, both of which can vary cam phasing and valve lift.

SteVTEC

Also true. No disrespect taken

irvine78

iTrader: (2)

ur the coolest ex-Honda owner i've known yet!!

SteVTEC

Don't jinx me - I'm still the title holder.

[chant]please total...please total...please total[/chant]

If they don't total it, I'm gonna trade it in ASAP anyways, so either way it'll work out

Max2000

speaking of Dual chamber capacity muffler. which suppose to give the Max more HP.. how many of you with aftermarket exhause notice increase of HP?

Jeff92se

iTrader: (82)

Which out of what?

Since mufflers cannot really give that much hp anyway, it's really a non-issue question.

Eric

Steve,

I realize that VTEC is specific to Honda's, I was just making reference to the famous VTEC-"kick" when the system switches over to the more aggressive timing.

I've never actually felt VTEC myself but I think I'm feeling something similar in my 2K2 and its quite different in feel to my 2k SE. In my 2K, the engine does seem more eager beyond 4000, but its not a "jump".

Not sure if I'm explaining myself properly...

SteVTEC

You wouldn't feel any kick from the VTC since it's a more mild variable valve timing scheme. You might feel a kick from the secondary intake runners (not valves - the intake runners are part of the intake manifold before the valves) opening though. I'm pretty sure that on the VQ35 it's around 4000rpm - where the intake manifold (not valves) go into high performance mode. The torque peaks out at 4400rpm so you could be feeling that too.

Eric

Yeah, I'm thinking its the intake switching over to the secondary runners. I would think there wouldn't be any feel at all with the VTC as my understanding is that it varies continuosly throught the RPM range.

Does nobody else feel this kick?

Jeff92se

iTrader: (82)

Smart man! BTW the maxima doesn't have a second set of runners(ala Ford sho 12 runner set-up). It just opens another section of the manifold to allow more volumes of air in.

AudioMan

Jeff92se

iTrader: (82)

You probably don't want to do that

SkylineGTR

Maximas have a very mild version of "VTEC" only on the intake side, thats why we dont have that "jekkyl and hyde" feel to our cars. The variable vavle timing we have isnt the full package like on certain hondas i.e. Civic Si, Prelude VTEC, TegR, S2000. VTEC for hondas high output cars is pretty amazing, if u havent felt it, u should try it, just when u think the car is gonna like die cuz it cant pull any harder, the revs pick up and the car just pulls harder.

irvine78

iTrader: (2)

ditto.

ehughes

Whatever its called, my 2k2 pulls very quickly from about 4k! It is a noticable "jump".

Keven97SE

The 4000 rpm surge you 2002 owners feel is the variable volume intake manifold opening. You would not want that manifold valve to stay open all the time, though, as you would actually loose torque at lower rpms. The beauty of this type of intake manifold is that you can have good low end torque as well as excellent high end torque (HP) by having an intake that can switch optimization rpms.

The reason why the surge on the 2002's is more pronounced than the 2000/1's 5000-rpm surge is simply due to the fact that the 2002 has two more distinct torque curves, one that peaks ~3000 and the other ~4500. These correspond with the lo- and hi-rpm optimization points in the intake manifold. The 2000/1's have a far less pronounced bump...on those engines the intake manifold more just keeps the torque falloff at 5000+ rpm from being as steep and stretches out the torque curve.

Take a look at a 2000/1 and a 2002 dyno plot and you'll see what I'm talking about.

Nissan's continuously variable cam timing (CVTC) would not give any sort of torque surge because, as the name implies, the "tweaking" occurs continuously over a broad rpm range. It's more of a stretching or flattening out of an otherwise peakier torque curve. CVTC provides a pretty mild effect that you won't feel.

Jeff92se

iTrader: (82)

Maximas don't have ANY version of Honda's Vtec.

SteVTEC

True.

Honda doesn't have any type of VTEC system that varies only cam phasing. i-VTEC does it now, but that also uses multiple profiles that vary the lift as well.

I think Nissan's CVTC would be functionally equivalent to Toyota's VVT-i, which both only vary cam phasing and don't touch lift.

ehughes

I realize that it is all relative, but I "feel" the effect of my 2k2.

mattattax

ditto

DAREN

iTrader: (3)

if you want a nissan motor with Variable Valve Lift buy one of the following. SR16VE, SR16VET, SR20VE, SR20VET. they have VVL - nissans version of VTEC. it been around for a while but not in the north amerincan market. nissan has VVL and they know the pro's and con's, if they want to introduce it to the VQ series then fine. nissan seems to be happy with adding displacement and using moderate RPM's.

dont get me wrong 260hp from whats essentially a 3.2L VG30E is impressive. (the honda SOHC V6's accord,cl,tl)

FastCougar

I too noticed the surge at 4,000 RPMs ... it was very noticable. I am a former owner of a 99 Cougar with a 2.5L Duratec V6 that had a similar setup. Ford's Duratec line has a Dual Stage intake setup that has a little control box called the IMRC (Individual Manifold Runner Control) that would actuate a seconday set of throttle plates that blocked air from entering one intake valve. So, below a certain RPM, in the 2.5L Duratec's case about 3200 RPM, the car would start to pull harder. I must say however, the Maxima pulled MUCH harder. Of coarse, you guys have a full litre of displacement on us, but the setup felt similar in power deliver, but on a larger scale.

The idea behind this is is quite simple. You have 4 valves per cylinder, 2 intake and 2 exhaust. By blocking one of the intake valves, you keep the intake velocity high until it reaches it's threashold. Then open up the butterflies and whoosh, the low end torque gives way to top end HP. If you have ever looked at a Duratec dyno graph, you will notice a nice dip when the secondaries open ... this is due to the loss in velocity of the intake charge. This could be produced with the car in neutral and it would actually snap open ... kinda on/off ... I always wished it would be more linear and open gradually.

The new Jaguar X-Type uses a similar system, except it is a 3 phase system, not two. Perhaps this is to add the refined linear progression in power because yuppies wouldn't know what hit em Again, Ford sorced the Duratec to the Jag, so the 2.5L lives on since it was axed in the Contour and now the Cougar.

SteVTEC

Then it's definitely the secondary intake runner path opening up then that you're feeling. It couldn't be anything else (you wouldn't feel the CVTC - only the intake runner crossover)

Jeff92se

iTrader: (82)

Note: this is the first reply to the thread. Amazing!