Hot intake air (and the contributing hot engine bay) is really a separate issue from true throttle lag / unresponsive-ness though, it's best not to confuse the two. Killing VDC and running a modified throttle map will help.

Another thing that helped me (but may not apply to everyone else) - my dyno tuner had intentionally set the area of the A:F table that deals with low rpm + low throttle input (top-left-ish) fairly lean to conserve fuel on the highway. It's just a standard thing they do. I bumped those values back a little bit richer and it helped some (a bit more fuel available on initial tip-in from low throttle).

Reducing heat in the bay and focally in the intake tract is helpful in general; colder air makes more power. It's not a throttle-specific issue, however. FWIW, I'm pretty happy with Stillen G3's sitting on top of LTH's, but I've also made some minor related heat mods. Mostly, I've shielded the intake tubes with a thermal wrap (Thermo-Tec : Cool-Air Tube Heat Shield), and I also bypassed the throttle body coolant lines.

since i have read on here how to disable the vdc 100%,there is more power for sure.i was thinking the lag also had something to do with how hot the 02's were getting.but now that you have stated the afr issue.it makes perfect sense.but i wonder if putting non foulers on the 02's would help at all without a tune with minor bolt on's ? it seems that after the 02's gets so hot,the afr's go too lean from the factory setup ?this is all speculation as the little lag i have now doesnt start right away.

Killing VDC doesn't do a DAMN thing for those of us with the serious problem. It sounds like you guys just don't like the throttle mapping. This thread has to do with a serious problem where occasionally the car falls flat on its face with the pedal to the floor then gives you whiplash.

The basic problem with the stock throttle map is that it refuses to fully open the throttle when you nail the pedal at low RPM. It gradually lets the real throttling open up as the revs rise. This is a form of pedal delay that tuners try to fix, etc. Your problem does sound different...

How long is the delay before the car reacts? Is it from a standing start in first, or rolling in some gear? What RPMs and pedal position did you start at? Getting data on that particular issue is the key to understanding it. I wonder also if there's any commonality in setup between people that have a large, complete delay? Perhaps large intakes (G3) without going through the procedure to re-learn the intake tract's Idle Volume after install, or something like that?

I read the updated post in your thread. You're right about the gradual throttle ramping with the RPMs. It's so unnatural and feels artificially held back. That explains my boost gauge gradually getting out of vaccum and slowly or barely building boost at times. I do feel the roughness of the throttle similar to rough engagement of the clutch and not being able to keep my foot still on the pedal haha.

What's interesting is that when the car is fairly cool I can get boost to build up at half throttle and low speeds since the BOV flutters at light loads. It's pretty fun in the neighborhood. After awhile I can't get boost to build up unless I hold down the throttle and let it rev past 3-4k RPM, which is not good in the neighborhood (easy to exceed the speed limit).

I even showed my friend by punching it in 1st while turning out of the parking lot with VDC off. The car slowly ramps up, but doesn't spin out of control. His Lotus is so much better on the throttle response even after some hard driving.

This year is definitely a bad year. We're breaking records over here. The car gets so hot that when I press down on the pedal the throttle opens up, and then it hits a ceiling and refuses to do anything else.

Also, do you guys feel it's difficult to quickly rev match with this car? I usually bog on the downshifts because I end up not revving it high enough.

Yeah that's troubling. My car's NA, the breathing mods aren't ideal for very-low-end torque, and I'm on 11" wide rear rims (295 tires), and I can break the rear end loose in 1st every time if try, regardless of hot weather or runtime. I usually don't though, I like my tires to last a bit.

Edit: although I should add, it probably helps that I have a very stiff rear sway and some weight loss in the rear :)

My Z was basically stock. After the car got hot, no way I could break out in any gear without revving to 4k RPM and dumping the clutch. And yes DIGI, rev matching was affected when I had my car.
Hopefully gonna test drive a BRZ this week =D I'm really missing a sports car (and will not buy another 370 until this issue is resolved). I really wanted to love that car.

so something is dumping too much heat in the im causing this bogging.i cant get on the car too long without stopping before i experience this bogging.there has to be one thing that is dumping too much heat into the im besides the obvious heat soak. pcv hoses are not helping for sure.i plan to remedy some of that heat with oil catch cans.i will be looking to see what else i can do to eliminate as much heat as possible.

has anyone done a egr delete or is it even possible on this engine ? that would eliminate more heat from going into the im.and does anyone have a link showing the schematics and what is what on this engine ? i would surely appreciate it !:tiphat:

on a side note,when i have had the bogging,i stopped,popped the hood, and immediately put my hands on the tb's and they were cool to the touch in 82 degree ambient temp.so i know the intake and tb's are not the blame.pcv hoses on the other hand were hot.what is that thing on the back of the engine towards the top that looks like a small motor ? that thing gets very hot.sorry for some of these questions.i have done alot of research on here already and these few things is all i need the answers too por favor.

edit;and my oil temps were 195-205

Is it possible that the PCV valves are getting stuck open when the engine gets hot? That will cause a leaning effect, probably more pronounced at low RPM's.

possible.i will be trouble shooting everything i can think of to resolve this issue.i will find the culprit eventually.

EDIT; come to think about it,those pcv hoses ARE dumping extra heat into the front two piston holes.i will do something about this, this weekend and see what my results are for that.

Are the PCVs active? Or are they a standard passive valve on this car?
(I sold my Z, so I don't really have a way to check anymore)

i will have a better understanding of them this weekend when the car is cold to investigate and work on.ive only had this car not quite 6 weeks yet.

What do you mean by active or passive? There are PCV check-valves screwed into both head covers, which connect to tubes that go straight to the intake manifold for vacuum sources.

Then there are unvalved lines going from elsewhere on the covers to the air intake tubes for crankcase fresh air supply, which have baffles (presumably to prevent catastrophic problems w/ intake backfires).

I pinched a pcv line today on lunch and i didnt hear any click of the pcv valve like i would on other cars when the pcv valve is operating correctly.that tells me there is an abundance of heat being sucked into the im.i am pretty sure these pcv hoses are the culprit for my bogging or hesitation after a couple of spirited runs.add hot oil mist into the equation and there you have it.i'll find out soon enough after i put some cans on.this is my next mod for sure.anything to stop a direct heat path coming from my valve cover to the im.:shakes head:

Well, there is a proper PCV valve on those lines, assuming you're playing with the right ones (the ones that run to the pair of outlets on the front of the intake manifold). Maybe the valves have gone bad?

I do run an Al catch can way over in the battery compartment, but I wouldn't think the relatively small volume of hot PCV air would be a significant factor anyways. An actual failed PCV valve could cause all kinds of problems, though.

Meaning is it a normal check-valve, or are they electronically controlled (sensor + actuator hooked into the car's computer).

yes ,the ones i checked are the ones going into the front of the manifold.im still a noob with this car so if i dont hear a click by pinching the pcv hose,how can i tell if the valves are bad ?

Good question, no idea :). They're cheap, and I'm at 30K miles. I just put in an order for a pair of them from courtesyparts because, hey, why not.

Edit: parts list from the order (2x rubber O-rings, left/right PCV valves):

2 x [11812] RUBBER PCV,VALVE - 370Z (Z34) 2009+ (11812-Z34001) = $4.92
1 x [11810PA] VALVE ASSY-CONTROL - 370Z (Z34) 2009+ (11810-Z34004) = $14.57
1 x [11810P] PCV VALVE - 370Z (Z34) 2009+ (11810-Z34003) = $14.57

Well its really hard to judge why the lack of response if you start messing with the car's internals. My engine is completely stock and if I keep my revs at 3 k and slam on the accelerator, my wheels spin and i am pushed to the back of my seat. Its such an amazing feeling.. I can't and will not touch the engine because I have it warrantied up to 100 k miles 7 years.

i had the bogging issue after spirited runs around curves and such while i was stock.i have eliminated alot of whatever this issue is and when im done,i wont have this problem anymore.if i drive the car normal,i dont have a problem.but i didnt buy this car to putt around curves and keep revs under 5k

Oh I missed this earlier. No sensor/actuator, just check-valve.

This issue is whats keeping my 370 from being as enjoyable to drive as my 350z. Hopefully someone will be able to find a way to make the throttle response as responsive as the 350z.

call it bs or whatever but i grounded the tb's last night and today i noticed the response has improved even further on the same 2 mile stretch that has 4 sharp turns in 93 degree heat with the ac on.so far,i have noticed an improvement from the stuttering or lag or whatever.anything to help with that hesitation.i feel when i get my catch cans on and change plugs,i should be good.

edit;check this page out.its on a mazda but still.
http://www.mazdas247.com/forum/showt...udboxer)/page9

I'm dubious of the benefits of grounding the TB's. Maybe if you had an existing wiring problem with the throttle position sensors and/or actuators in them or something. Seeing as how the TBs aren't naturally grounded (connected to plastic intake), I'd imagine they wouldn't bother having the body of the sensor/actuator ground out to the TB to begin with (meaning, grounding the TB may do nothing electrically regardless), but I have to admit I haven't pulled the sensor/actuator out and looked.

The only thing less reliable than a butt dyno is a butt impression of gas pedal responsiveness issues :)

If you want to try the grounding thing, do not pay the crazy $ for a kit. Do a hack job yourself first for trial. Any 12ga or bigger speaker wire will work FINE.
Source: I am an electrical engineer.

I've can honestly say I'm lucky and don't have this problem. In manual mode, throttle response isn't an issue; it just sucks waiting for the downshifting. VDC or no VDC, it's all good. Just my .02.

seriously, you can get the necessary wire from home depot for 20bucks with all the connections you'd ever want

If you read through the thread, for the most part you'll see this problem doesn't plague automatics for the most part.

Well there's certainly nothing in the 6MT itself that would contribute to the issue, seeing as it's just a gearbox. If anything more people would complain of something like this on a 7AT than a 6MT, as there's a whole host of additional possible problems with the 7AT that could cause similar effects, on top of whatever's going on prior to the trans that some 6MT guys are seeing.

Read through the other 52 pages.

I have done some datalogs my 370 and noticed that the throttle never opens all the way until RPM is above 2000. Is this what you guys are experiencing?

interesting link here.from my understanding of how the vvel works,it is my assumption that in the higher rpm band,the intake valves are letting more blowback in via higher valve lift vs lower rpm band via lower valve lift.could this be the culprit ? letting too much blowback in ?
Nissan Introduces New Engine Valve Control Technology - Variable Valve Event & Lift (VVEL)

My statement was based on logic, the other 52 pages are irrelevant in that sense.

Lol, that's actually a valid statement.

Pretty sure that's the issue. MT guys can just ride the throttle and then drop the clutch so they don't really experience the delay in the same way. Which makes me wonder why the AT is always rated as having quicker accel.

Well the AT's first gear comes out at a lower ratio than the MT's, even given the worse ratio in the final drive. That's probably most of it. The lockup torque convertor works great, so you don't see as much slippage loss as traditional ATs. And of course 7ATs have the torque multiplication factor going for them too when you first engage.

I've been suspecting something to do with this, but it isn't all the time which leads me to believe some sensor is malfunctioning under certain conditions, causing erroneous data to be input to the computer.

i agree.this morning my car was losing alot of power and what seemed to be missing like i was running on 4 plugs periodically.maybe in my case,its the cats.this is twice now since ive owned it that this has happened.

tb grounds are coming back off today.last time i ran the car it was 95 with a heat index of 102.this morning it was 75 degrees.is it possible to run the car with vvel unplugged for testing purposes ?

what about the people that run test pipes,do they have this problem also ? i want to try an eliminate troubleshooting the 02's before i waste my time unhooking the exhaust to have a look at the cats

The only sane way to disable VVEL is to replace the heads. VVEL is an oil-pressure-driven mechanical system with an eccentric shaft, etc. The electronic servo just controls the angle between the shafts. Somehow disabling the ECU's control of it would probably be catastrophic.

Have you gone over all the basic maintenance/inspection stuff? PCV system, air filters (not clogged, not leaking air around them from a bad seal, etc?), clean the MAF sensors, reset the idle air volume, check for exhaust / intake tract leaks, etc. There are a lot of "little" things that can adversely affect engine performance.

the only thing i havnt done yet is to replace the spark plugs.

edit;on lunch today,i took the grounds back off the throttle bodies and i believe the grounds were hurting more than helping.this car is like a woman.moody as hell lol