deschodt

EFI 02, Gas pedal setup regarding pedal travel ???

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Sorry for the mouthful title, trying to prevent people from wasting time clicking on this if they aren't in this situation...

My car was converted to EFI 11y ago. I don't even remember how the the carb linkage was setup or if any of it remains, it's been so long. 

Obviously the mechanic that did this made up some sort of linkage - the gas pedal pulls on a bent rod which it attached to one of 3 positions on a lever, which in in turn eventually gets to the throttle body. I'll add pic later ! 

 

I have severals problem that have been getting worse over the years. 1) It was always an on/off switch, but now it's really really binary. It feels like there is minimal pedal travel, like 1.5 cm tops, and out of that the initial 25% of the travel is just play and never reaches the TB, and 2) at full throttle, the last 25% at the throttle body never gets actuated... It's not bad on the flat, the car being very torquey, but on long hills it's a dog that tops out at 70 mph.. I bet the car will be a ton more fun when I fix this... 

 

I have some ideas - I started by removing the carpet under the pedal and gained 3mm of travel 😉 I will play with that bent rod tonight both on which hole it attaches to on the pivot arm, to eliminate the slack and possibly reach more than 75% WOT. But even if I manage that and somehow reach WOT and no slack, my entire travel at the pedal is still very very short... 

 

Just wondering how you EFI folks setup your gas pedal mechanism, for inspiration... If you have pictures of the mechanism, I'm ready to re-engineered the whole kitchen sink... 

Thanks !

 

 

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Not knowing how much of the original pedal linkage has been changed lets start with the basics.  The "bent rod" that is moved by that actual pedal goes through a bushing in the pedal box, under the car you will find an arm that is attached to that rod.  This attachment is a clamp on type and the end of the rod has been serrated to give it some grip.  If the arm is not tight on the rod it can slip and this will cause you to have a low throttle pedal and/or not fully open the throttle plate at the manifold.  You might just need to loosen the arm and pull the pedal up to normal height (have someone hold it while you pull down on the arm to take the slack out of the throttle cable) and tighten the clamp bolt on the arm. 

 

There is also the possibility that the throttle cable housing  has slipped in the bracket(s)  at either end

 

it sounds like this cable arrangement may not have been well thought out from the beginning if it has always been "ON/OFF" you might need to change the position of the cable where it attaches to the arm at the pedal box to change the ratio of pedal/throttle plate. 

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efi or carb....not much difference really.  it is all just a lever pulling on a cable.  it is a mechanical  connection.  if you don't have the stock style linkage, really need pics of what you have for us to help.

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first thing i would do is get rid of that pivot and pushrod on the firewall.  extraneous junk!

run the cable all the way down to the pedal box.  looks plenty long enough.  

 

2012-03-10_13-04-57_230.jpg

 

 

Edited by mlytle

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I used Marshall's post as a go-by and built a very similar bracket at the pedal box, a simple bracket at the TB and a Lokar 36inch cable. Only one photo available here at work but since it is the TB end, just match it to Marshall's. For travel, you can adjust where on the arm at the pedal box the cable attaches. I set mine to allow the accelerator to rotate about 30-40deg.

 

2018-10-11 16.40.27.jpg

Edited by pato2002

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Ok so now I fully understand the problem... Basically *Crap* engineering from the start from the mechanic who did that... It may be hard to understand on cropped pictures, hopefully you get what I'm saying below...

 

Look at Pic 1:

The gas pedal movement inside car pushes/pulls on that "bent rod" on the pic below...

That bent rod moves that "lever with 3 holes" that rotates the "rod to throttle body" tube....(I tried all positions, all suck for different reasons)

At the other end of that rotating tube,  (pic 2) the rotating "rod to throttle body"tube has a pin that contacts a makeshift welded bracket that in turn makes the TB open/turn... 

Forgive my nomenclature here, I did not learn engineering in english... 

 

Problems are several fold: 

- That spring on the lever is positioned wrong right over the DTA ECU and makes it so the lever is more or less horizontal at rest. For the gas pedal to be fully UP in the car (and restore full pedal travel), the lever would need to rotate higher up (see pic 3,   "note angle of lever"). But if it does, look at the "slack" at the other end, the pin is nowhere near the bracket, so there is a lot of slop and 25% pedal travel wasted...

- The leftover pedal travel (plus that dumb spring placement) is then insufficient for the lever to ever travel downwards enough to get full tube rotation/TB actuation...

 

- Seems like I should:

a) reposition the spring directly above the lever (not to the side like now)  to allow resting lever position to be near vertical (full pedal travel) - hard to do, there's some EFI sensor there... 

b) cut off and reweld that "TB bracket" half so it makes contact with the pin in that upper lever position, taking down the slack. 

c) that should get me full pedal deflection again, and ability to reach full TB opening (adjust as necessary to not go too far and put pressure on the TB mechanism)

 

- OR: ditch that whole $#%$#% mess and start over... You guys use cables... this is all rods.. and crap...

 

More thoughts ? 

throttle1.JPG

throttledown.JPG

throttleup.JPG

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or...do what we suggested.  get rid of all the rods and levers and just use a simple cable as in the pictures we posted.  MUCH better.

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16 minutes ago, mlytle said:

or...do what we suggested.  get rid of all the rods and levers and just use a simple cable as in the pictures we posted.  MUCH better.

 

I'm not against that at all, but it's not a simple deal..  Is there some sort of common conversion kit I can buy to start over ?  

 

Anyway, now I understand the problem at least... Dunno how I lived with it like that for so long!

Edited by deschodt

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IMHO rods are a better system than cable because it's bullet proof  but not in this case unless you are a math/geometry freak there is so much math that needs to go into what is a cumulative system that it's just a crap shoot for us garage mechanics, so go with the cable it's been done many times and it's stupid simple and is next to bullet proof.  

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^

Very nice.

 

For now, proof of concept, I have "fixed" it... 

I relocated some EFI related stuff elsewhere and moved the spring straight above the lever. That gave me back lever movement and full pedal travel... But also a giant amount of slop since the groove in the the TB bracket (pic 2 above) was too deep and too far to contact the pin immediately. I then inserted a small bolt with washers and double nut (on the side where it cannot touch the rod and jam). The washers stick out and allow pin contact way earlier... Wow... Full pedal (the spring complains a bit for now), and almost full throttle opening at the TB (90% I'd say - I'm not sure how far I should go opening the TB honestly, full extension OK?)

 

That's proof of concept... I need to drive it a bit like that.... if it's good I'll weld that groove shut instead, maybe find a better spring too. Then mull over a cable system...

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10 hours ago, deschodt said:

 

I'm not against that at all, but it's not a simple deal..  Is there some sort of common conversion kit I can buy to start over ?  

 

Anyway, now I understand the problem at least... Dunno how I lived with it like that for so long!

it acutally IS pretty simple...

pedal box bracket is just a bent piece of metal, as is the bracket on the TB.  the cable can be had from any speed shop(think carb throttle linkage) or a bicyle shop (same as components as bicycle brake/shifter parts), or i believe the throttle cable from an 80's honda civic works.

 

WAY simpler than trying to make a pushrod linkage work!!!!

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