Drive-by-wire throttles

[GeaugaFletcher]

The DBW throttle on my '06 Miata is pretty good, but noticeably less responsive than the 'antiquated' cabled throttle on my '97. It's most noticeable in two situations:
1.) blipping the throttle (purely entertainment, not a real drawback)
2.) in mid corner, especially with a little drift, the throttle doesn't let me make adjustments quite as well as the old one

I have no interest in stability control / nannies / etc. I just barely came to grips with ABS on the new car... It's paramount to me that the car reacts instantaneously (as much as possible) to my input.

 

[mpvue]

Originally Posted By: Kestas

I'm starting to see a pattern with many automotive designs where a technology is introduced to save gasoline, only to cost the owner more when the unit needs to be diagnosed, serviced, and repaired. I believe the added cost of initial production and future repair of these features far exceeds the cost of gasoline that it saves. The only winner is the manufacturer, who scores points with the federal government on CAFE ratings.

The goal should be low cost of owning and operating a vehicle, not just good gas mileage.


saving MONEY on gas shouldn't/isn't the goal; saving GAS is. as the oil supply dwindles down, it's cost will go up, and as mfgrs try to get their cars more fuel efficient, their cost will go up as well. we're trying to hold on to an unsustainable lifestyle, that is, trying to have our fun cars just like we always have. well, things can't go on forever just like they always have. I'm not happy about it either, but more technology is a fact of life. and as for gearheads, we ARE better off now then we were 20 yrs ago; cars across the board are more fuel efficient and have higher hp than they used to (and quieter, handle better, brake better, etc). gone are the days (I hope) when a guy would rip the TBI and electronic ignition off his engine and go back to a carb and points.

 

[Kestas]

I think gas can be factored in when I talk about initial manufacture of a technology, and also factored in when the part needs to be repaired. Mechanics consume a lot of gas also (getting to work and running their shop). If we had fewer mechanics - or the need for them - we'd save a lot more energy.

We're talking about complicated technology to replace a simple cable. A small percentage of the populace spending $1200 to $1400 to replace a part that didn't even exist 15 years ago is a dubious application of technology, especially when the benefits are marginal. When I look at the cost/benefit curve for this, I just don't see it on the benefit side.

My comment aren't just for throttle-by wire, but also for a lot of other technology that has pervaded our engine compartments. We made a decent leap from carburators to electronic ignition and MPFI, but little has advanced since then.

I'll have to be honest here, a lot of my rant comes from owning a used 95 Mercedes, but I think my comments are food for thought on American vehicles as well.

 

[brianl703]

Have the underhood wiring harness started rotting out on that Mercedes yet?

 

[Kestas]

That was updated as soon as I bought the car 5 years ago. I recently updated the ETA (throttle-by-wire). I don't wait for problems to happen. More importantly, I understand the entire car uses this wiring. It's just that the engine provides the heat for fast decomposition of the wiring insulation. With thirty-some computers in this car, future ownership will be an adventure!

 

[brianl703]

Typically, underhood wiring harnesses are supposed to be made with wire that uses crosslinked polyethylene insulation. This insulation can stand up to the heat found there.

The wiring harnesses in the rest of the car can be made with wire that uses standard PVC insulation.

The difference between the two types of insulation is obvious if you put them in a flame. The PVC burns, the crosslinked polyethlene does not.

My Ford Contour had this issue, Ford replaced all the underhood harnesses for free under a 10 year, 100K warranty. The replacement harnesses were made with the right insulation.

Apparently the issue with PVC insulation is that it becomes brittle when exposed to heat. This was, incidentally, a problem with the 60C-rated Romex cable used in houses built prior to 1985 or so--the insulation was being damaged by the heat of light fixtures. Later Romex cable uses conductors rated for 90C. (That's why when you buy a light fixture it says on the box to call an electrician if the house was built prior to 1985. They haven't tested the fixture to see if it will be OK with 60C Romex cable).

 

[PandaBear]

I think if designed correctly, DBW is a good system. A magazine I read while waiting in my mechanic's shop said that DBW eliminates the WOT surges in over lean and from WOT back to idle over rich. This increase the maximum "safe" compression the engine can be designed with.

Of course, on top of that many models design the DBW to be 1) cheap to make but not durable, 2) over efficient to discourage fun driving, 3) too slow in response to cut cost, or 4) never spend enough time in R&D to get it right.

Just like RWD should be more reliable, but it is usually model specific.