adanande

I posted at the end of that forum wher a z driver had intalled pulleys and a flywheel and experienced edreased engine braking jolt when donshifting. THis is because the proggrammed throttle input to maintain idle does not match and is meant for the old flywheel. When he sepresse his clutch the driver said that his rpm would jump, this is because of the decreased load, not as mutch throttle input is need to keep this light weight at idle and as a result the idle is lashing, this idle needs to be adjusted i used to drive an rsx type s and i also had a flywheel and although my idle avcter the flywheel was higher than before the dealer adjusted it. The engine is acutally accelerating because of its now didorportionate idle and thus not brakin. I guarrantee that once you get your idle adjusted by the dealer it will be fine. ps check my post at the end of the original dicussion it will be more clear. peace.

hfm

iTrader: (1)

That is really interesting. I will need to follow up with the dealership about this. I will add that I already increased idle from 750 to 813 and advanced timing by two degrees with consult II after flywheel installation. I'm not sure what needs to be done to adjust throttle imput as it relates to idle.

Thanks for your post.

FLY BY Z

My idle is in the exact same place as it was on the first day I brought the car home. Are you saying that the idle will actually be different or that it will be the same and this idle setting will affect engine braking and RPM jumps putting the clutch in? If this was my problem, would I be seeing higher RPMs at idle? Because this is my problem but I am not seeing an RPM difference at idle.

jreiter

iTrader: (6)

This is what I was wondering also. I would guess there are two settings you can make in the computer:

1) The minimum RPM at which you want the engine to idle.

2) Some sort of load compensation value (for lack of a better term) for the throttle when you take your foot off the gas while at speed. This would be different from the idle RPM setting.

Like FLY BY Z suggested above, I'm guessing #1 is not what we're after. When you push the clutch in and the RPMs fall all the way down, the car's computer is simply going to continuously keep RPM at the preset number when idling. (Such as 650 rpm, or whatever the stock setting is.) This is the setting being adjusted when people want their idle rpm to be faster. (Handy for when you get upgraded cams and such so you engine doesn't die as easily.)

Number 2, though, would probably be the one we are interested in to correct engine braking after lightening the load on the engine. (Via lightweight flywheels, pullies, etc.) I don't know if this is something we can simply set with a scan tool, nor would I even know what to ask a service tech so he would understand what I'm talking about. Anyone know the "correct" way to phrase this?

Zship

iTrader: (1)

It is the drive by wire system leaving the throttle open. For emission purposes it is desirable not to fully close the throttle. However, because you need to be able to decelerate, they just can't leave the throttle open. The ECU is probably being fooled by the lighter components and is actually slow to respond to the close throttle position. I noticed it when I put the UR pulley on. Push in the clutch and the RPM's would continue to rise 200 RPM then start to drop. The ECU is programmed with the known weight of the stock flywheel/pulley so it drops as soon as you lift the throttle. Lighten those components and you are going to get throttle overrun. Someone should call Technosquare to find out what they can do. They are already fixing the problem with the system only opening the throttle 85%.

FLY BY Z

Is this not dealer adjustable?

scubasteve

iTrader: (6)

I had a hard time reading that first post........but I do have UR pulleys and am getting the NISMO flywheel/clutch soon. I will also be heading down to TS early summer for the flash to go along with my SAFC II programming. Interesting how all of these issues arise with NA..........don't most of us avoid FI because of problems!!!!!! I, however, like working on my car. Please feel free to notify me with updates.

Zship

iTrader: (1)

Only idle RPM is adjustable. Unfortunately, that's not the problem.

jreiter

iTrader: (6)

Yeah, I'm worried it might take some deeper reprogramming as opposed to a simple adjustment via a scan tool. Hopefully someone can find out for sure how to deal with it.

As far as the 85% throttle thing, what's up with that? I'm wondering why Nissan chose to do that. There must be a reason.

Zship

iTrader: (1)

JR,

Because of the stock intake and exhaust flow, cam duration and timing no additional air was flowing after 85%. So why open the throttle any further and reduce air flow velocity? This just makes throttle response deteriorate.

Now do some mods that increase air flow through the system and you will want the throttle to open all the waaaay!

stx

When you push in the clutch on a stock 350Z and the rpm's will also rise around 200 rpm's and then drop. Adding a lightweight flywheel and crank pulley did not change that on my Z.

FLY BY Z

I think he was being conservative. Mine rise, at idle, mind you, about 3-400 RPMs. If I am moving at all, they will rise more.

stx

Geez, that is strange. My rpm's don't rise that much at idle. Mine rises about 150 to 200 on idle and also when I am moving. It seems to move about the same as when I was stock. Do you guys all have upgraded clutch assemblies? You think maybe an upgraded clutch and pressure plate might weigh less than the stock assembly causing the engine to jump more rpms?

jreiter

iTrader: (6)

Ah. So getting the throttle body to open further isn't helpful until you get hotter cams?

Sorry to hijack this thread.

FLY BY Z

Who knows. The bottom line is that it doesn't hurt it even for a stock car. With the throttle body reprog comes higher rev limits, etc. Even that can benfit from the little bit of air that will come with a straight throttle blade.

Z1 Performance

iTrader: (564)

huh?

Infern0

iTrader: (1)

Wow....lotsa technical mumbo jumbo in this one....lets get to the verdict. So, from what I got out of it, if you get the pulleys and the flywheel, you need to go to the dealer and tell them what...that they need to adjust your idle....and they will know what you're talking about? Just trying to get the main gist of all this.

hfm

iTrader: (1)

Adjusting idle only affects the revs at idle speed (about 750 rpm). This is something of a different problem. I'm not clear as to whether it is ECU related or something else or if this is infact what it's supposed to be doing but, I have a feeling it's not right.

I've PM'd someone who is very much in the know about the Z and hope to have something I can post. I'll do just that as soon as I hear anything further.

Bait-Fish

It makes a little sense. The last percentages of a valve opening do not change flow a considerable amount compared to the early stages of opening. The design team must have found that a remaining 15% didn't affect performance (everything OEM) so they set that to WOT. Now when the thottle is told to close off, it starts to constrict the air stream sooner not having to travel that 15%. The perceived reaction time is decreased. All theory but it sounds like proper reasoning. Once you start adding more flow into the equation with aftermarket parts, that 15% will be getting become more restrictive as the flow/velocity increases.

Re: ECU weirdness
Has anybody else noticed that while compression braking, the braking effectiveness and exhaust note increases and changes (respectively) about .5-1sec after letting off the throttle? This is best heard with windows down on a slow, steep grade in the lower gears (where the effect is more pronounced). Every time the throttle is moved any, engine braking diminishes. Then again, .5-1 second after letting off again it increases and slows down quicker.

Although I don't have the mods discussed here (stock Gc), it does make sense that the ECU may be the root of the problem.

adanande

all this deeply scare me. maybe i should convert the stock z plenum set up to tommy Kaira's individual throttle bodies. Does anyone know if thse are still drive by wire? How much do they cost? Will changing the 85 percent throttle opening to 100 percent help with forced induction. I think it will. Headers are needed to increase flow but they are an impossible mod. with my RSX type s i installed headers and it made a fluttering noise untill i traded it in because it always got loose when i reved into vtec. But all this aside it pisses me off that the 350z had te potential to have at least9 to 95 horsepower per liter and nissan chose not to have that. If our valvetrains were better and our plunum didn't suck and if we didn't have four catylytic converters we would have some marginal throttle response. Bye everyone, i'm annoyed, the car is too expensive to be this slow. I guess i payed for looks not a sports car. And for all of those that say a sports car doesn't have to be fast, my z can'candle either the left compression rod has been faulty since i bought it 8 months ago, the steering response is non existant and the alignment is way off. peace