As I go back and forth between a vehicle that has a conventional throttle (the Miata) vs. a vehicle that has throttle by wire (the Sentra), I find myself becoming increasingly aware of the the intrusive characteristics of the throttle by wire system. (slower response, holding revs after I let off during a shift, etc).
I’ve never put much thought into how throttle control actually works up until now. It seems as though the pressure change caused by the opening/closing of the butterfly valve in the throttle body gets sensed by the MAF/MAP, then fed back to the ECU which changes fuel delivery/timing/etc. Is that really all there is to it?
If this is the case, then couldn’t I eliminate the throttle by wire by putting in a conventional throttle body and just leaving the electronic unit somewhere out of the way but still connected to the ECU? I’m thinking the ECU is responsible for the electronic nannying by controlling the servo in the throttle body. If I leave that servo intact but not actually in the intake path, the ECU may still think it has control, when in reality it wouldn’t. Fuel delivery would still be controled by the MAF/MAP readings. Or maybe it uses the throttle position in the electronic unit to change the fuel, in which case, my idea would probably not work very well.
Only problem I would forsee is somehow making the computer friendly with the manual TB’s Throttle Position Sensor. I dunno how drive by wire works but you’d have to be able to let your ECU see whats happing via TPS signal. Good question, i’m going to help you do more research on this.
Even if you get it working for an early generation throttle by wire, I’m guessing the newer systems are only going to be more complicated. As more cars have stability control and traction control integrated I’m sure the ECU’s control over throttle is only more integrated and advanced.
his TPS sensor is in his pedal… thats how the ecu knows how much to open the valve… so moving the valve will make no dif to that…
what he will have a problem doing is making the attachment points for the throttle cable from the pedal to the Tb and making it work ok … does your car have any traction/stability control that it uses the tb for?
Yes, but often the tps will aid in the control of fuel management. Meaning, if he does do this, this may really fuck up how the car delivers fuel in closed loop mode. Unless by some grace of god, it’s matched up nearly perfectly. Now if the said car a stand alone system, it wouldn’t matter because fuel could then be compensated for, still not to a perfect value, but much smoother than without.
This also really only depends on if ur cars tps aids to information being sent to the ecu which is used for fuel correction. If not, then everything I said, was just completely useless.
Yeah, the TPS was the piece of the puzzle I was forgetting about. It sounds like there are only two ways for me to go about this:
Standalone engine management, or use an ECU from another car that uses the same engine without the drive-by-wire. Altima maybe, or convert over to the fivespeed and ECU from the regular '02+ SE-R, which would also eliminate my three biggest gripes with this car: the gearing, the need to run 93 octane, and the throttle by wire, which the SE-R does not use. I don’t know if I can get a LSD for that tranny though.
This is probably something I would not end up doing unless my tranny takes a shit.
really you don’t like it? My '03 Chevy 2500HD had the 6.0L w/ DBW and I love it. Wasn’t intrusive at all and the throttle response was amazing! I guess it really goes back to the PCM and how well it is programmed. Like for example the IAC table is holding your revs up in between shifts, but then again your Mazda probably has a completely different approach to things. I like the DBW in the vehicles I have driven but I guess I need to try some un-domestics out sometime.
I think if I was driving an automatic, I wouldn’t even notice it. Where it is really annoying is when rev-matching my downshifts. In the Mazda it works perfectly, both due to the quicker response and the fact that the pedals are actually properly placed for heel-toeing. In the Nissan, I almost always end up with the car lurching forward a bit because it was holding the revs, plus they drop much more slowly after the blip.
You ought to be able to change to a cable driven system, I know the swap on the BMW S54 engines and the gen II 996’s is pretty straight forward. If your TPS reads normally on your throttle body it should be almost as easy as adding the cable. Atleast that’s what I understand from reading about the Porsche/BMW systems.