VQ35 VVT - getting it to work with a standalone

[fireslave]

Hey guys. I've been looking into doing a VQ35 swap into a s13, and one of the major issues i'm concerned about is the wiring and electronics. SpecDRacing did a pretty sweet swap using the stock computer systems, but there are a lot of components involved in getting the stock ECU to work for this swap.

I personally would like to use megasquirt, but I have yet to see a single example of someone using megasquirt to control the variable valve timing. I personally don't want to lose 20hp or so by not having VVT, so I'm looking for a way to make this work.

I've heard that the VVT is controlled with pulse width modulation (PWM) but I dont know whuch values cause which rotation and such. From what i've read on boards such as this, the cams are just rotated (in relation to their already rapidly rotating selves) to make the valves open earlier/later. Although, i have no idea if this is true... does this mean that the duration is the same (well, it would mean that, assuming i understand it right, which im not so sure of).EDIT: Just found this on wikipedia - http://en.wikipedia.org/wiki/N-VCTdoesnt say much, but it does say that its only timing, not duration or lift.

Anyone who has knowledge of this, or a good link to a technical explanation would be appreciated.

if someone has the PWM values i would love them, but I don't expect it to be that easy.

If it is just a simple matter of using different PWM signals to adjust the valve timing, I think I could build a module to control this, or maybe modify the megasquirt in some way. I've done embedded programming using PWM before, and i think this would be badass.

If it works, I'll either post the megasquirt code up for all to use, or sell a separate controller box for the VVT.... even if it does work, it'll be a year or two down the road. I still haven't got my hands on the car or the engine... but im starting my first real job in a few days, and intend to live my cheapo room-mate lifestyle for awhile, because i'd rather have a car than like... furniture and stuff.

Modified by fireslave at 1:11 AM 9/28/2008
Modified by fireslave at 4:50 PM 9/28/2008

[Nycist]

megasquirt supports vvt? i didnt know that....

[fireslave]

No, it doesn't support VVT that I'm aware of. But I think that there are certain versions of megasquirt that have PWM channels that you can use for whatever you want, and I think the VVT on the VQ35 is controlled via PWM. Either way, it wouldn't be terribly hard for a computer programmer to control the VVT with PWM (assuming it is PWM controlled, which would make sense), as long as the computer programmer knew what values caused what degree of advance. Even if megasquirt doesn't support VVT, a standalone VVT controller could be created by someone such as myself, as long as all the necessary parameters were there. Now, I don't know what parameters Nissan uses, but I assume it could be calculated based on the reading from the MAF sensor, the RPM's, and the throttle position. I don't actually know off the top of my head how to get any of these three parameters into the type of chip I would be doing this with (probably a microchip brand PIC) but I do know that if I could actually find out a general idea of how far the timing should be advanced in certain situations, and what signals to send to the VVT itself to control it, then finding out how to read RPMs, TPS and MAF would be a relatively easy matter of research or experimentation. It wouldn't necessarily be identical to the values Nissan uses (unless someone has some super-specific info somewhere) but it could be made to be user-programmable, which would probably net similar, if not more power than stock VVT in the hands of experienced engine tuners, and those lucky ones with dynos and such (which I, unfortunately, am not). Could also be tuned differently for Turbo vs. NA, or for different cams.

[gregfarz78]

Look into Haltech but be prepared to pony up about $2000+ for one...and just so you know you won't find a full standalone unless you have a ton of money to blow. Nothing is simple with newer nissan ecu's. Standalone is a lot of money you're better off making the stock ecu work b/c theres no reason for a standalone unless you plan to run high boost and need more control over various setpoints. My advice if you want a painless swap don't piece this swap together save up and buy an entire front clip engine/trans/ecu/bcm/nats/wiring harnesses.

[fireslave]

Yea, I just found that haltech one on the internet today... first one I'd even seen that controls the VVT. It totally gave me hope.

I was considering just bringing over all the 350z components that are required, but I really like the idea of the megasquirt, because it allows precise tuning for a low price. Initially, i plan on leaving the engine fairly stock... except probably a bigger exhaust because I'll have to custom fabricate that anyways. But it would be nice to be able to boost it later and have it properly tuned. I know you can buy turbo kits with various forms of engine management included, but I wont necessarily want to spend $6000 on a turbo kit when I'll probably have to make custom piping for everything anyways...

Besides, if I made a standalone N-VCT controller i bet could sell it for a profit and still appeal to the DIYers and megasquirt crew...

But yea, I know electronics on cars are scary these days... but I think I could figure this out eventually if i had an oscilloscope (which I can use, but definitely cant afford) or if i had some idea as to what the PWM values were...

If not, hopefully I can find a newish front clip with the trans. and all the electronics for 3000-4000.

[gregfarz78]

I'm not sure megasquirt will work with the complex electronics of the VQ35, the Z has been around since 03 so I'm sure someone would've figured it out by now if it was possible. If you can mess with it and make it work you'd probably make a nice chunk of money off that. I doubt nissan publishes those values you're looking for though you'd probably have to crack the code of the ecu to find them out. I'm going off of what I know of the QR25 which also has VVT no one has been able to crack that ecu yet either.

[fireslave]

I don't have any intention of cracking the ECU code, to be honest, I'm nowhere near that talented *yet*.

I was thinking more of a separate module to control the VVT that uses my own logic, as opposed to an exact copy of nissans. It would then be based off of parameters that are appropriate for controlling a VVT system - no necessarily in an identical manner as nissan, but something like a 3d map of TPS, MAF, and RPM values that would allow a tuner to take reasonable advantage of the capabilities of VVT. We know, for example that more overlap can provide us with better full throttle power at high RPM, but makes low speed idling difficult. we have all seen dyno gains from someone changing timing, with adjustable cam gears, for example, but on the very same graph, seen parts of the RPM range where power was lost instead of gained. Even if we can't tune it as good as nissan, im sure we could be better off than with no VVT at all.

Also, from what I've read in various places, megasquirt can be used with the VQ35 - you don't have to worry about the complicated electronics because you simply replace them - the spark plugs or injectors don't work any differently than on a car from 1990. You can get the engine running, but without being able to control VVT, you will lose 20 or so HP over stock.

There is a realistic chance that the physical VVT controller on the engine works with the same exact PWM specifications that a standard servo uses - it would make sense, because they both move a position within a range of rotation based on an electrical signal. Unfortunately I won't have a VQ35 to try it on for probably like a year, unless someone who did a VQ swap with megasquirt or something that couldn't keep the VVT has a leftover VVT actuator that I can play with...

[SERVQ]

Yea, I just found that haltech one on the internet today... first one I'd even seen that controls the VVT. It totally gave me hope.

I was considering just bringing over all the 350z components that are required, but I really like the idea of the megasquirt, because it allows precise tuning for a low price. Initially, i plan on leaving the engine fairly stock... except probably a bigger exhaust because I'll have to custom fabricate that anyways. But it would be nice to be able to boost it later and have it properly tuned. I know you can buy turbo kits with various forms of engine management included, but I wont necessarily want to spend $6000 on a turbo kit when I'll probably have to make custom piping for everything anyways...

Besides, if I made a standalone N-VCT controller i bet could sell it for a profit and still appeal to the DIYers and megasquirt crew...

But yea, I know electronics on cars are scary these days... but I think I could figure this out eventually if i had an oscilloscope (which I can use, but definitely cant afford) or if i had some idea as to what the PWM values were...

If not, hopefully I can find a newish front clip with the trans. and all the electronics for 3000-4000.

i got AEM standalone(2300 with harness), but the pulse doesnt work right. unfortunatly it would dip my torque curve at about 5-5.5k when it would switch on like Vtec. I made more bottm end torque with it on for some reason. 247whp w/o up top. I was told it is tunable but very difficult

[aceofspds]

using a utec and v-manage would probably be easier and more straight forward

[sr20goofus]

i got AEM standalone(2300 with harness), but the pulse doesnt work right. unfortunatly it would dip my torque curve at about 5-5.5k when it would switch on like Vtec. I made more bottm end torque with it on for some reason. 247whp w/o up top. I was told it is tunable but very difficult

is it at all feasible to use an AEM unit from some other 6cyl engine that has variable intake cam timing? repin the connector and such instead of going with the AEM universal unit or Motec, Haltech for that matter?

I have been reading through the FSM about the cam timing and how it works, but there is no difinitive answer to what the ecu output is that makes the cam timing advance or retard, at least that i have found yet, more searching to continue.

[turbo6]

is it at all feasible to use an AEM unit from some other 6cyl engine that has variable intake cam timing? repin the connector and such instead of going with the AEM universal unit or Motec, Haltech for that matter?

I have been reading through the FSM about the cam timing and how it works, but there is no difinitive answer to what the ecu output is that makes the cam timing advance or retard, at least that i have found yet, more searching to continue.

Yes, but Haltech (Platinum 350Z PNP EMS) is already programmed to control them on a VQ. This ecu has been used as a wire-in for multiple VQ35 swaps into other cars, such as the S13/S14. If you need any info, I have all of it available. Contact me

[irax]

yeah but will it make atleast stock power with that ecu or even as much or more than a tuned stock ecu?

[sr20goofus]

standalone > OEM ECU,...more tunability, on the fly changes, and more integration.

[irax]

standalone > OEM ECU,...more tunability, on the fly changes, and more integration.

that would be true for older cars, and some newer cars.. but deffinatly not the 350z or g35, what TS, JWT, and UpRev can do with the factory ecu is for the most part better than a stand alone.

[sr20goofus]

what makes it better than a standalone....a quality standalone that is?

everytime you change something you have to go back to them for a reflash, you have no control over any changes to the tune. For some who DD's their car and has no interest in wanting on the fly changeability, then yes reflash is perfect.

Otherwise for racers and swaps the standalone offers more to the user and owner.

[irax]

with the uprev's osiris system it changes on the fly and its way cheap compared to other ems's , but the fact of the mater is that not one stand alone out there can make at least stock power on a stock motor, and only a few can use 100% factory sensors and componants (HydraEMS is the only i can think of right now). or at least last time I checked.

[sr20goofus]

with the uprev's osiris system it changes on the fly and its way cheap compared to other ems's , but the fact of the mater is that not one stand alone out there can make at least stock power on a stock motor

i wouldnt believe this for a hot second. a plug-n-play unit is garunteed to help increase fuel efficiency, and your power band, even on a completely stock motor. Where did you hear that standalone wont net any gains? is this a 350z specific claim? or stock motor in general claim?

[irax]

it was 350z specific... but honestly its based on info that is a 2 years old. So basically prior the most recent update to haltech. That and seeing the few vq35de swapped 240sx's out there what what mods and what they dyno at and compaired to G's and Z's with the same mods put down more power and the only difference was tuned ecu vs stand alone. Like the issue of supper street where they pit an s13,14,15 against each other and one had a vq35de, one had a KA-T and the s15 was stock block and minor mods around a track. and the s13 with the vq had some stuff done to it and it only put out 285hp. P&P, cams, intake, exhaust, AEM. I know that G's and Z's with a tuned ecu alone put down 270 and with same mods(except ecu) as that 240 put down 315-320

these new ecu's that nissan makes are really freaking trick compaired to the older ecu's

[sr20goofus]

it was 350z specific... but honestly its based on info that is a 2 years old. So basically prior the most recent update to haltech. That and seeing the few vq35de swapped 240sx's out there what what mods and what they dyno at and compaired to G's and Z's with the same mods put down more power and the only difference was tuned ecu vs stand alone. Like the issue of supper street where they pit an s13,14,15 against each other and one had a vq35de, one had a KA-T and the s15 was stock block and minor mods around a track. and the s13 with the vq had some stuff done to it and it only put out 285hp. P&P, cams, intake, exhaust, AEM. I know that G's and Z's with a tuned ecu alone put down 270 and with same mods(except ecu) as that 240 put down 315-320

these new ecu's that nissan makes are really freaking trick compaired to the older ecu's

using one random VQ swapped 240 as your base isnt a fair judgement. the dyno could have been out of calibration, it could have been a chassis dyno instead of a dynodynamics, or dynojet dyno, maybe he had a bad tuner, maybe the 315whp Z's your claiming were SAE corrected for perfect day at sea level, maybe it was super hot in CA when teh test was done, etc etc...

If a simple reflash is so much better then why do the koni challenge teams who are running stock engine (350Z) with intake and exhaust all running standalone? one team makes ~285whp on a dynodynamics dyno and only 2 bolt on basic mods. If it was so easy and better for them to run a reflash why would they opt for standalone. Koni challenge is a spec series with limited modifications based on class, no p&p, no intake risers, just intake and exhaust modifications.

I am not 100% against a reflash at all, i have just never heard of a reflash being better then standalone, and standalone never being able to make even stock power. At least where i am on the east coast standalone opens up all kinds of possibilities for tuning, making changes based on gear, rpm, speed or throttle position. And you can makes changes to any of those variables. At least for tracking/racing in general standalone seems the better choice from my point of view. For hardparking, cruising or grocery getting a reflash would be beneficial.

[irax]

I see your point, but i did check the parts and dyno's to make sure they were the same. And the swapped 240's opt for the stand alone because it makes it easier to wire up, with a factory ecu you need to wire up a lot of stuff to not be limp mode. I guess I'm still adimet(SP?) about a tuned ECU because I am weighing the cost more than the benefit because I plan on sticking to one setup only. But if your constantly changing parts I guess the stand alone would be more beneficial.

[fireslave]

On a related topic, what do you guys know about the VQ35HR exhaust side VVT? I've read it's electromagnetic, but i dont really have any info on it.

I assume that if you unplug the wires, it just stays at the un-advanced setting, which should be similar to the non exhaust side VVT engines. Its possible that its retarded more, though, because the earlier one had to be a compromise. If it is retarded more, disabling exhaust side VVT would probably be worse than not having it, where as it wouldn't matter much if the default position was the same as those without exhaust side VVT.

(of course, if you did disable it and it was retarded, you could just use an adjustable gear to put it back in the neutral-ish compromise position)

Assuming it will run though. IMO it'd be stupid to have it do anything but go back to a neutral-ish position if the VVT was disconnected, but someone a few threads down is asking this very question. You never know though, so its better finding out sooner rather than later.