Electronic throttle staying open between shifts? I think yes!

[kaplooi]

So I just bought a Versa S Manual and I'm quite pleased with it apart from the revs not dropping off like they should when shifting as many others have posted about. The first thought is that it's got to be a super heavy flywheel preventing the engine from revving and the revs from falling between shifts, but I'd be willing to bet any amount of money that these are both consequences of the electronic throttle programming to help lower emissions. Installing a lightened flywheel (if there was one) would likely worsen the symptom since it's holding the throttle open slightly before eventually closing instead of closing completely like a cable throttle would.

I'm guessing that short of a factory re-flash that 'fixes' the problem, hacking the throttle control code in the ECU would be the only solution to this behavior. Too bad we don't have something like Flashpro for Civics.

There will never be such a re-flash offered by Nissan because it would effect emissions so I've been thinking of 'barn door engineering' alternatives. There's nothing that can be done to improve throttle response without re-flashing but I wonder if you could wire to the cruise control switch to feed a signal to the throttle to immediately close completely. It would be similar to how Maf sensor piggybacks work except you'd be intercepting the voltage signal to the throttle servo. The throttle plate is either open or closed when there's no voltage applied to the servo, so if simply cutting the power to it (and only it) or providing full current during the second or two you need to shift would actually make it drop like it should. (Hopefully the FSM indicates which condition = closed throttle but it's one or the other). Then when you release the clutch the cruise control switch is depressed and normal throttle control is returned to the gas pedal. It's just a thought but I'm 95% convinced this behavior is a result of the throttle remaining slightly open after suddenly letting off the gas to shift.

[kaplooi]

Ok, so after some further thought for it to work you'd have to use a combination of the cruise control switch and the clutch interlock switch to only disable the throttle during the duration of time where the pedal is traveling to the floor. Where when you hit the interlock switch the bypass circuit is disabled. Doing this would close the throttle only during the half-second or so between shifts, hopefully defeating the specific piece of code in the software that's so annoying. The first idea wouldn't allow you to start from a stop . Obviously the whole idea only works if there's a specific wire on the throttle harness that controls the servo. If it's all integrated then it is truly locked down and not modifiable the 'brute force' way.

[Promise Land]

Are you planning to manually use the CC switch to change the TPS voltage?There are 6 wires into the TPS. If you know which one you are looking for, I have the diagram if you can't find it.

[kaplooi]

I think if that's all that was needed then an aftermarket throttle controller would do just fine. The problem, I think is that the motor simply cannot respond quickly enough to drop the revs during a shift or the ECM isn't letting it, so cutting the power to the motor for an instant and letting the return spring close the valve would be the objective of this mod. My theory is that if the throttle control motor relay could be manipulated to cut power to the motor by releasing the CC switch and turned back on by the interlock switch, the throttle should close 'mechanically' via the return spring between the time when the pedal is depressed and traveling to the floor on its way to hitting the interlock switch. (Obviously this would require always clutching to the floor when shifting, or else having some sort of momentary timer switch or something) Looking at the FSM the trick would be providing a continuous 12V signal to the ECM via the throttle control harness so it wouldn't detect the open circuit and trip fail safe mode. Basically a relay would be needed to do the switching based on the clutch switches and probably another relay wired to the ignition switch the same as the OEM motor control relay is so that the ECM thinks all is normal.

It's all just an idea, but I think if done carefully it just might work.

[maxjax800]

I have the 2010 versa 1.8 s manual car. I too have noticed the rpms staying high between shifts.

Personally I hate it. With the rpms staying high, I have to let go of the gas during an upshift, wait a sec or so, and then shift the gear and release the clutch. It makes it difficult to shift fast.

I've noticed the rpms especially take a while to drop during a 1st to second shift.

Also, I notice that during a downshift, when I try to blip the throttle, there is a delay in the rpm spike.

[philipa_240sx]

My '05 Altima with 5spd did the same throttle hang between shifts. Extremely annoying if you drive fast. It also doesn't help that many modern Nissan engines use heavier dual mass flywheels. If you read other forums, you will find many other makes share this same throttle hang trait... in the name of reduced emissions.

As for ECU reprograms, check out UpRev Engine Management:

http://www.uprev.com/

They are offering some interesting products to the Nissan community. They recently did Versa +CVT tune:

http://uprev.com/uprev_blog/2010/03/ver ... vt-tuning/

[uprev]

Doing what you've mentioned will throw your ECU into limp mode with a quickness. If you wanted to have this working properly we'd need a development vehicle for a few months. It's something we can probably do, but we're fairly busy with more pressing issues currently like keeping the transmissions in the trucks from blowing up and GTR tuning support.

Frankly alot of that RPM issue you're talking about comes from the dual mass flywheel. Those damn things weigh like 40 pounds. Check out the design of them, you can google search it. They are pretty impressive and heavier than sin. The rotational mass is huge.

Yes it is an emissions thing, is it going to be easy to resolve no. There is much more to it than just throttle plate. There is fuel injector controls, timing controls, cam control. Adjusting one just throws all the others out of whack. So we'd need to address the larger issue of the entire package. Like I said we're capable but we'd need a development vehicle for a few months in order to reverse engineer it all and test it, make useable controls for it, add it into our software, write instructions on it, and then test it on other models to make sure the controls work there also.

[steed77]

I do agree with uprev on most points.

What you are experiencing is called "rev-hang". They do this for emissions control. It also helps for stalling, but it is annoying for sure. Throttle latency (quicker response) can be addressed by a tune or a throttle controller. VersaSpeed has 2 throttle controllers available, one is quite reasonable priced.