post here when you experience this phenomenon-[PAD]



-I think it's hi-larry-us when i see/hear someone fire their new (in this case D-max) with a generous throttle amount.



sigh.

2/4/2009 4:24:17 PM

actually on the new diesels with throttle plates, it can make them easier to start in cold weather

2/4/2009 6:26:21 PM

BAH

2/4/2009 6:31:26 PM

you do realize that the duramax's have a rediculously high cold idle right off the bat too don't you? mine hits about 1600 before it comes down to about 950 on high idle

2/4/2009 6:35:22 PM

only when i fuck up and flood it

2/4/2009 7:06:47 PM

^^nah, If it's not 6 cylinders i dont acknowledge it's existence [goddamn that picture]



^I'm talkign about new cars, like 2004 and newer

[Edited on February 4, 2009 at 7:15 PM. Reason : -]

2/4/2009 7:14:29 PM

drive by wire, pushing the gas pedal to start the car does nothing

2/4/2009 7:47:26 PM

until key is on, on position

2/4/2009 7:49:27 PM

The only reason one should even think about pushing the throttle on a newer, EFI car is if, for some godforsaken reason you've flooded the damned thing. Or if you have just flooded the intake with cleaner or Sea Foam or something and choked the bitch out. Then you mat that pedal; doesn't change the amount of fuel being injected very much (dependent on rpm and mass airflow; speed density changes a little bit more), and the volume of air sweeping through the cylinders helps to clear the flood.

Either that or you wait for about 15 to 30 minutes and give'er another go.

Pushing the pedal or pumping the pedal on a fuel injected car with modern electronics and all else in good shape accomplishes exactly jack shit...except for that much more wear on the rotating parts and bearing interfaces where the oil pressure hasn't built up enough.

2/4/2009 8:07:31 PM

I remember working on an old volvo once where you could actually hear the injectors clicking when you'd pump the gas pedal with the ignition in the on position and engine off

i'm guessing it doesn't work that way anymore

[Edited on February 4, 2009 at 8:10 PM. Reason : asf]

2/4/2009 8:10:30 PM

You're right on the money. Doesn't work that way any more. The Volvo you're probably talking about was likely a 122 or 142 or the like with Bosch D-Jetronic fuel injection. Crude by today's standards, to say the least.

The throttle position sensor on the old D-Jetronic actually had about 20 contacts. And each time the wiper crossed one of the contacts, it fired the injectors. Kind of like a substitute for an accelerator pump in a carburetor. D-Jetronic also used an arrangement of two sets of contact points in the base of the distributor to signal the injectors to fire under normal running conditions...this is obviously before the advent of transistorized electronic ignition, hall-effect triggers or AC waveform stator/reluctor triggers.

D used some interesting means of sensing and control. Airflow was a crude speed/density setup that incorporated an LDVT (Linear Displacement Voltage Transducer) coupled to a diaphragm instead of the much more common Wheatstone bridge manifold pressure sensor. Older engines tended to run rich unless the LDVT was recalibrated due to less manifold vacuum. Also, fuel pressure was modified by means of a vacuum line run to the atmospheric side of the fuel pressure regulator. This continued all the way through L-Jetronic and LH-Jetronic. Motronic I think is different.

2/4/2009 8:26:25 PM

yep. 142.

i was gonna post on the throttle position sensor it has exactly what you're talking about but a.d.h.d. kicked in and i forgot

i had a hell of a time getting all the injectors unfrozen after it sat for about 10 years.. ran decently after that though surprisingly. hell, my parents still have the thing and would probably give it away to anyone interested.

2/4/2009 8:46:59 PM

on my cobra, when you press the gas all the way to the floor it opens the fuel system and will not pump any into the injectors. had to do this when i put a timing chain on it.

[Edited on February 4, 2009 at 9:02 PM. Reason : lolspell]

2/4/2009 8:47:09 PM

timming chain


but... i do this..... my dodge cranks for about 70% less time in the warm with some throttle, and wont start without a little pedal love in the cold.(or rather, it will start, but dies immediately)


the comanche needs pedal when it is warm outside to start, but when it gets below freezing you cant touch the pedal if you want it to start

[Edited on February 4, 2009 at 9:01 PM. Reason : d]

2/4/2009 9:00:35 PM

haha- the case in point for this thread was our company's owner firing up his LBZ? (sharp angled headlights) this afternoon, as soon as it fired off he had to have been at like 1500+

2/4/2009 9:05:02 PM

without letting off and less than a second later it was in drive and rolling out

2/4/2009 9:36:15 PM

on a drive-by-wire car there is a good chance that the ECU won't open the throttle if you press the pedal during cranking anyway.

or alternately, it will open it a bunch.



Here is a main throttlebody duty cycle map on a Subaru boxer engine (courtesy Cobb Tuning). X axis is how much the accelerator pedal is pushed down, y axis is rpm, and the value itself is how much the throttlebody is actually opening. Notice there is hardly a linear relationship.

So at 800 rpm and 18% throttle (according to the pedal position sensor), the throttlebody will open 50%. This creates a feeling of low-end torque and throttle response. It would also make your car rev up easily on startup if the ECU allows it to do so.

[Edited on February 4, 2009 at 9:51 PM. Reason : 50 pager]

2/4/2009 9:43:03 PM

^

Interesting.

2/4/2009 10:04:31 PM

arghx is coming up with a 50 page response

2/4/2009 10:08:17 PM

Quote :

"arghx is coming up with a 50 page response"

2/6/2009 7:24:51 AM

I floor the gas to start mine on cold starts.

I have no idle air control

and am completely guessing on my starting enrichments

2/6/2009 9:54:07 AM

Hell, if I had my way, I'd use a throttle stop solenoid and a pushbutton switch on the dash to momentarily inject a lil fuel in the manifold. Or a simple bypass with a needle valve and a solenoid valve, with a simple timer circuit to energize the injectors for a second or so when the ignition switch is turned on.

2/6/2009 11:03:49 AM

I agree with everything that's been said. However (and interestingly enough) the owners manual for my S2000 mentions, under the section for starting that car, that if you're having difficulty you can push the gas pedal down a bit to help. My car has drive by wire though, so I think this little tidbit was accidentally left in the manual from God knows when

2/6/2009 1:06:15 PM

every car has drive by wire, there is a wire thats hooks the pedal to the throttle plate

2/7/2009 9:40:18 AM

the SuperDodge once had a piece of string, and it was tied to my hand. Temporary nigrot fix.

2/7/2009 11:30:22 AM

^ i know mine isnt as badass as that, but I'm running a section of bicycle brake cable as my throttle cable


sigh, ive got trans fluid all over the underside of the truck, gonna be fun locating the leak.

2/8/2009 10:38:49 PM

^^I've done that. You have to adjust for the stretch of the string as you drive, and it's very difficult to keep one hand on the wheel, one on the shifter and one pulling the string.

2/8/2009 10:59:06 PM

^^Dude, I had a similar issue, and it wasn't my pan leaking, nor was it the output shaft seal or front pump seal.

The SD had MASSIVE cooler lines (like either 7/16 or 1/2 I can't remember). Places here and there where there were support brackets holding them to the tranny. One had chafed a pinhole in the actual steel line. I got a big-ass piece of fuel line to patch it, but it still leaked (cause I had cut out a piece of tubing, and hadn't swelled a barb into the existing ends for the hose/clamps to deadhead against). Eventually got me a piece of copper tubing and two compression unions and scabbed that bitch to the point of no leak no mo'...

2/8/2009 11:08:07 PM

^

^^

2/9/2009 7:52:38 AM