Does anyone know how to replace the Drive by Wire TB for a mechanical one? Or is there any way to some how take apart a Q45 TB and use the factory drive by wire (the gearing inside)?

As you may know the Q45 TB is 90mm and has been used in the past on a Z32.

I don't think anyone has come out with a larger TB for the Z. (I know Crawford is working on something)

I found this on Jtuned, but can't find anything else on the car.

http://www.jtuned.com/content/templa...id=34&zoneid=2

The heart of this system revolves around a single Garrett ball bearing snail mounted to custom manifolds which produces a maxed out 410 horsepower. A custom front mount intercooler helps feed the modded 90mm Q45 throttle body. As many of you know, the new G comes with a “drive by wire” throttle system which makes it quite difficult to tune due to the computer having so much control. Blast ditched the stock unit in favor of a mechanical throttle body and custom plumbed throttle cable. Fuel duties are handled by 600cc injectors and a Bosch fuel pump controlled in unison by the famed HKS FCON VPRO fuel management system. Monoxide is sent into the atmosphere through a custom downpipe leading into a Fujitsubo exhaust system. 13psi of boost is regulated by the new HKS EVC which also serves as an in cabin boost gauge.

 

Mechanically that would be a fairly strightforward project. I've done basically the reverse here:
http://www.engineswaptech.com/forums/thread/60.aspx

I've done this so I could use the stock 350z throttle body but with cable operation, it may give you some ideas.

The main question on your project is how to keep the computer happy.

Fred

 

is it a standard -5/+5 volt TPS?

 

I believe they are 0-5V+ range, I was able to use it no matter the range as the MegaSquirt ECU I'm running allows you to zero it out at closed throttle and then again at WOT to calibrate.

Fred

 

would be possible via stock ECU and a piggyback then? Q45 throttlebody hybrid stock TPS. Connect the stock TPS to ECU to keep ECU happy and use the mechanical Q45 for tuning purposes. Its basically the stock w/ a mechanical portion driving the TPS, rather than TPS driving the mechanical portion

edit: i read your posts and looks like thats exactly what you did

 

As long as your stock ECU still sees a TPS signal it will probably be happy.

My only concern how smart the stock ECU really is. In other words, if it tells the throttle butterfly to close and then doesn't see that it did infact close (because you ditched the motor that used to close it for a cable) what would it do? Maybe nothing, maybe put you in some kind of limp mode, etc.

Fred

 

Would it compare throttle position to MAF saturation? If then, its possible it would dump to limp mode. MAP mode would fix that though.

 

That I'm not sure on, I'm out of touch with MAFs. But, my instincts tell me that it (like most ECU's) just uses the TPS to detect WOT (so it can got into closed loop and ignore the 02 sensors) and any sudden changes in throttle position (for acceleration enrichment and possibly deceleration enleanment (fuel cut for better economy)).

The only time I've seen ECU's use both TPS and MAP for fueling is in hybrid EMS schemes typically for cars with large cams and individual throttle bodies where getting a good clean vacuum signal at idle is hard. I've never seen it done with a MAF.

Maybe somebody w/ some stock ECU tuning experience can chime in.

Fred

 

Thanks Fred, excellent DYI. Good luck with the mag.

 

Did you loose driveability outside of WOT for your car?

I think you're right about the TPS for WOT. TPS is for fuel tables. Would it be possible to emulate a fuel table?
I can imagine it would be. The cross section of air x MAF will give you volume.
Hope some ECU savvy folk can come in

 

My car's not done yet so I can't comment on the driveability. But, since I'm using an aftermarket computer it wouldn't really compare to your setup anyway.

I really don't think your ECU uses the TPS to calculate fuel tables, that's left up to the MAF I believe. I'll dig around the FSM and see if I can prove myself wrong.

Fred

 

Fred,

From what i have read on your tutorial you have done the conversion based on instructions from another forum?

"Got a throttle body mounted tonight. Instead of making an adapter to mount the pathfinder TB farther forward I was able to modify the Z's cable-less TB. Using examples seen on another forum I was able to convert it to cable operation but then took it a step farther and was able to keep the Z's throttle position sensor."

Can you forward us the link to the conversion? I guess the only way to see if it will do the trick with our OEM ECU's is just testing and see if it will work.

 

Your driveablitily is going to suffer. The DBW system control the idle speed and cruise control. CC is no big deal, but the idle control will be noticable. You will have the keep the car alive with your foot on cold starts. You will also drop idle or stall the car when you turn on the headlights and or A/C.

 

Idle will change a bit but trouble on cold starts or A/C and headlight turn on problems sounds like an exaggeration to me.

 

Here ya go:
http://forums.maxima.org/showthread.php?t=430880

Fred

 

what part of missouri are you in Fred? this state needs more car litterate people.

 

I'm in the SW corner, Joplin to be exact. Where are you from? Most around here are still into hotrods and carburators and of course 33" supper swamper mud bogger tires, etc!

Fred

 

Before you decide to spend much time on a conversion, why not do a flow bench analysis on the oem TB or baring that expense acquire a few ACCURATE manometers and measure the resistance at different WOT RPMS.

16 Years ago in our search to increase the 90 Q45 power output we spent months redesigning throttle bodies [sharping/knifing the plate, grinding the screw heads, thinning the support shaft] destroyed a dozen or so in the process. Any way the best we came up with was maybe 1-2-3 HP above 6500 rpms out to 7300 rpms........The TB was already too large and unrestrictive for 274 cubic inches. Nissan usually leaves some reserve for future engine displacement bump ups so they can get more model life out of TB so they are already oversized by 15-20%.

If the oem G35 shows less than 4-5 inches water column resistance... little will be gained with the larger unit.

A suitable differential manometer* sensitive enough to read in 0.1" increments would need protection from idle vacuum [a valve to device that only open at WOT otherwise you would suck the sensitive guts out of the device.

27.7 inches of water is 1 psi and 1 psi ~~=6.8% air flow depending on air
temperature and density/humidity.

* Manometer has 2 ports and you rubber hose each before and after the TB thus measuring the negative pressure [the drop across the TB plate/housing].

http://www.dwyer-inst.com/htdocs/pre...plications.cfm
http://www.dwyer-inst.com/htdocs/pdf...e/2000_iom.pdf

I have a lab full of these devices, you select the full scale and resolution for what you are measuring..............air filters a few inches, intakes a few inches, MAF around 7 inches, duct work a few inches. Even measure cat/exhaust component backpressure [higher psi limits required].
Anyway the standard for flow benches is no more than 28" and the typical restriction from atmosphere to plenum is only around 18 - 20" water column.