Nope, thats not what i mean. I know the "throttle" cut is the throttle, not brakes. What im saying is, the usual instance is for the throttle to be cut PLUS your pressing the brakes (what activated throttle down) to help slow the car down, and your foot is totally off of the accelerator.

Brakes + Throttle down + foot off accel is normal situation, i didnt mean throttle down = brakes + foot off accel. The throttle down only assists and is activated by the brakes in slowing the car down, but what if:

The throttle down activated while brakes not depressed and foot on accelerator. This cannot be simulated without the help of the ECU. guys who try and burnout do this:

Brakes depressed + throttle down + foot on accel. Take them pressing on the brakes out of this equation and you have the situation im trying to hypothesize.

Brake pedal NOT depressed/pads not hitting rotors + throttle down activated by glitch + accel depressed. This event is what im saying might cause the fall off in power at certain RPMs. The car is throttling up and throttling down at the same time, no brakes in the equation whatsoever.

I understand this as mentioned above. The cut of fuel is only activated by brake light, other than that, the brakes and the cut of fuel (throttle down) are not related in any way or are two seperate events that dont interact with one another except at throttle down activation via the brakes.

 

that is actually exactly what i'm talking about. If you take the 2 wires on your brake switch that operate the rear brake lights, hook them together and you have constant brake lights. Once that circuit is closed (switch connected) then the next part is slightly unknown. Either at a set TPS percentage or at a set rpm (not sure which) the ecu will tell the VDC that it's not going to allow this and the VCD kicks in cutting fuel just like it would if you had wheel spin. Again, very easily testable if you would like to try it out.

Have you ever had the vdc enabled and hammered the gas and felt how hard the car jerks when vdc kicks in? THAT is exactly what this circuit will do. If your car isn't doing that exact vdc action then something else is going on. That is the fuel cut operation when the brake like circuit is closed (brake lights on). Like i've stated, there isn't a reduction or maybe a slight decrease in throttle response, there is a full vdc cut just like when you lose traction and vdc is on.

Since you are getting a "reduction" in power or sluggish response this makes me think there is more going on than just that since it's not giving you the normal vdc effect.

 

^ I kinda understand what you are trying to say here, so bear with me.

Basically your saying you cant have both throttle up and down, when the fuel is cut, its a hard cut that wont allow a throttle up, so "sluggishness" is not possible. Is this correct?

I know that when i get multiple wheels slips around a tight turn my VDC will cut for a second then let off and i can accel then cut for a second then let off and so on until i straighten out. (back when i was running a smaller tire in rear than front, so VDC kicked all the time)

Is it possible that this above mentioned event is happening during fractions of a second like what i said above but much faster? Like its cutting then letting off then cutting again all in fractions of a second so you never feel a "hard cut" because your foot is on the accel and its not cutting long enough to be recognized?

Or is the fuel cut a set time thing? In other words, the ECU/VDC fuel cut is timed...it always cuts fuel for no more and no less than exactly one second before it will allow fuel feed again?

Also, your missing a BIG point here.... I WAS getting random sluggish responses, but after i took the taillights off it went totally away. WHY? The car is a dream to drive again, i was in on my way to work today with a huge grin on my face, throttle response is at 100%, 100% of the time. It hasnt driven this good in a LONG time, and there is NO WAY this is a placebo effect.... the changes in response/smoothness are just way too great.

 

The LEDs could be different from the regular bulbs by having either: more current draw OR less current draw...

I can tell you that they have a lot less, and are actually 'invisible' to the ECU, which depends on current draw to sense various events. So it's the same as having no bulbs at all, and you can pull all the bulbs out to see how that goes (won't rev past a certain RPM)...

By adding a resistor across the LED bulb lines, you are placing a measured current load back onto the circuit, simulating the presence of the original higher load bulbs. This works...

Now, moving onto the next issue, I think the ECU reads an on/off condition on the brake lights, since that's all they do anyway. I suppose you could try different resistor loads to find the transition point though.

I also think sluggishness and hesitation are more related to relative humidity, ambient air temp and barometric pressure than anything else really, but that's just a guess...

And this is very close to the classic topic of: "Do I need a grounding kit???"

HAHAHA

 

yes exactly!

I can't say a full no to that because anything is possible. Usually when vdc kicks in even for the shortest blip the rpms will drop and the vdc light will come on. I don't see vdc kicking in and cutting power without giving the signal that it was used. I can't say 100% this is the case, but it's highly unlikely given the nature of how vdc works.

It's not a set time per se. If it's wheel spin that it gathers then it cuts until the wheel spin is gone. With the brake light switch as long as the brake light switch is closed (brake light on) then it will cut. As soon as that circuit opens again it will go away. I'm pretty sure there is a small buffer time (like a dead time) for slight errors. Usually computer responses like that have a set time the event has to happen (usually in miliseconds) before it takes action just to prevent something from kicking in on accident.

I have never missed that point. Never once in my responses did i say that you aren't experiencing those things. If you thought that then you misread my statements. I am only explaining the logic behind how that system works and how it doesn't physically correlate to that being the source. Logically with how the system works it just doens't fit the bill. Maybe there is a .0001% chance but truthfully i think if it is the tail lights causing the problem it cannot be from the brake light circuit. It has to be causing an electrical problem in another circuit. Maybe it's causing a ground loop which is screwing with the ecu and the voltages of other sensors. IDK, electrical problems on vehicles are the worst things ever and make me want to bang my head on the wall. In a situation like this, if you know for a fact what it is i would eliminate the source and not even try to figure out what the source is doing to cause the problem.

whatever resistor someone used might work, but that doesn't mean there isn't still a problem that could maybe further damage your car over a period of time. who knows. I'm thinking the brake like circuitry isn't the path this glitch is taking to cause your sluggish response though.

 

Nope, this is not a gentle fluctuation in response i felt like associated with atmospheric conditions, and this happened in the span of 1 hour, same location. I drove it, switched tails, then drove again in the span of 1 hour. The car clearly responded differently immidiately after removing tails, and has been consistant ever since. The fluctuations used to occur multiple times within 1 driving period, however since removing tails, it no longer greatly fluctuates, not even between different driving periods and different days, and weather has greatly fluctuated here over the past couple days. Heavy storms yesterday = low barometric pressure, great weather last night and today = higher pressure, lower humidity, and temp change.

Your example of removing tails and car doesnt rev past certain limit is not the case. Take this guy's situation for example. I understand my claims are hearsay until proven, but this is NOT a gentle change I am talking about here. This is a very noticeable one. He says when he unplugs them, car acts normal:

 

Negative, lol, resistors will NOT be used to 'band-aid' this problem, as they can give out.

I agree with you 100%, the problem should be totally eliminated, which is what i intend to do. Those tails will not go back on the Z, unless for further testing of this anomoly, which i might just do if i can figure out a way to test this. Any ideas?

 

I pm'd ZAW117 just now to try and get him to chime in here in more detail on what happened with his tails. He has the identical tails i do and described the situation closest to mine.

 

wow, i applaud you for this.

most people just quick fix so they can use their nice looking goodies and go about their business. Then a year later when the ecu is burnt up from come crazy circuit they wonder why.

Honestly, i work with electrical problems as little as possible because they will make a person go crazy. Raj (RCdash) on here seems to have good knowledge on circuitry. Some others do as well. Not sure if they would be able to fix a problem that wasn't right in front of them though. Electrical grimlings take troubleshooting and testing the entire car to find the issue.

I would see if you can get them returned and try a different brand maybe. It sounds like it's a defect in some of their led circuit boards. maybe you could take that board out, look up the reisistors and all that jazz and solder yourself a new board in place with higher quality parts.

 

Personally, I like the JDM and OEM LED tails.... I would say, take one of those lights apart and see just how they are wired up internally... or test/measure the amperage load etc of those units. I'm sure someone here has an extra taillight laying around.

 

maybe find some busted tails from a g35 and use the led circuit from them?

i have a g35 so i couldn't help in providing numbers for the oem 350z tails. sorry

 

Ya, but how do we know the G35 ECU isnt programmed for a different voltage level for their LEDs, unlike our non.

Which begs the question, i wonder what the 06'+ OEM LEDs put out compared to 03-05? I wonder if Nissan manf those to put out the same current.

 

Now we're getting somewhere... I KNOW someone has a taillight laying around