engine and drivetrain Adventures in 73 Tii throttle/afr tuning

[gliding_serpent2]

After a long time I finally got around to ordering my new linkages from Jack.  I just need to get the car out of storage and try them out.  My only complaint was that the kit does not come with the long linkage from below the firewall/pedal.  Mine is not

original, and i think it is a source of some throttle pedal slop (but not the source of my issues).  

 

I will need to refresh myself on all of this again as it has been many months.  I think verifying i have the cap for the butterfly shaft is also key.  

 

Here is to hoping for an easy fix.  

[jgerock]

Visit the big box hardware store for some nylon washers to help reduce the slop in the (2) linkage pivots.  New BMW pivot bushings will not perform the magic that everyone hopes to see/feel.

[gliding_serpent2]

You win some, you loose some

 

So replacing the middle throttle linkage was a bit of a disaster.  As you all know, it is fiddly to get to.  Being a bit new to this and prone to brute force, I popped it off, but along with the "door knob" press fit linkage head (the end closest to the KF fuel pump on the middle linkage).  Just before I did that my brain was saying... "that looks pretty locked on, you might bend something, maybe you should leave it alone and just replace the other linkages, and see if that does the trick."  Sadly my primitive brain overrode logic and here we are.  So I used a very small vice grip to press it back on in-car, and then I used lock tite (which I imagine will not do much good as the parts could not be cleaned well in the car0.  It seems to be holding, but I know full well I need to get it properly replaced or fixed, otherwise I could easily lose throttle mid drive.

 

I should have used less force, more wd40, and started off by removing Plenum #1 (i removed it to press fit the piece back in).  

 

Good news is that my cap for the butterfly shaft is there, and in great shape. 

 

So I guess my next question is, how do I remove the butterfly shaft so that I can get access to the lever that needs repairing?

[xferboy]

56 minutes ago, gliding_serpent2 said:

how do I remove the butterfly shaft so that I can get access to the lever that needs repairing

I pulled the throttle body off.  The bottom of that shaft (as long as we're talking the same thing) has a ball on it, so there is room for movement.

 

Other may do it differently.   Hope that helps

[gliding_serpent2]

thanks. 

 

 

[jgerock]

Hmm- wonder what happened to the op in that thread link?  

[gliding_serpent2]

I took things apart.  rob's instructions in the linked thread were helpful.  Removing the air filter housing is key, but i did it without plenum removal.  But, my fingers are long and thin and my knuckles are a but raw in places.

 

i brought the throttle body shaft (bottom part that connects to the linkages) to the local machine shop and quickly had them spot welt the press fit linkage anchors (because i popped one out, and the other just in case), and straighten the one i bent.  I figured it was better than a bent linkage anchor that was risky for popping out.  

 

Now it is time for re assembly and tuning

[gliding_serpent2]

So far so good.  Oddly, the cam in the tuna can was lifting with the throttle application, but after loosening the screws in the shaft, and tightening them as part of the kf tuning procedure, this seemed to settle.  

 

My issue now is that the linkage from the firewall to the pedal can not be adjusted short enough from the top to permit full throttle.  Will see what i can adjust behind the pedal... And under the car.

Edited May 6, 2016 by gliding_serpent2

[gliding_serpent2]

This is another good thread.  

so far so good.  Engine warming up for the idle and mixture tune.  

 

An issue i ran into last year was my linkage from the pedal lever up the firewall being too long.  I could not get it short enough to allow full throttle with everything set.  With the new linkages i had the same issue.  So i popped the linkage out... Heated the bottom hockey stick end  with a torch, bent it shorter, and cut off the old end.  Perfect.  

 

Car is near full temp.  As it warms up i needed to screw in the idle screw to keep rpm's from dropping and causing a stall.  Not sure what afr to set the mixture at, but i will start with 12 for idle when hot, then drive and lean it out (or richen it) as needed.

[gliding_serpent2]

Deja-vu

 

so we what is old is new again.  I set idle to 900rpm, get my air fuel to 10.5:1 (remember i am useing a self calibrating aem wide band air fuel ratio gauge).  Without load, going up the rpm range, everything looks great, maybe afr goes to 14:1, then 13:1 wot.  Everything is warmed up.

 

get in gear and things go from 10.5:1 idle to 12-13:1 light throttle, up to 16:1 near full throttle (rpm independant).  Wot is 13-13.5:1.  Things go a bit more lean in 4th gear than they do in lower gears.

 

 No matter how much i fiddle with the idle and richness screws, no change to the above afr patterns.  The more i richen the mixture, the more idle rpm drops, the more i need to increase the idle... Repeat.  I dont think this is my solution.  

 

The warmup regulator is in the proper 10mm position.  

 

So i am back to square one.  My thought is that maybe this is a timing thing... but i am grasping at straws as i am no expert.  Another thought is that things are good, but that the throttle body continues to open faster than the kf pump lever can increase fuel.  But this seems to be odd given wot operates just fine.  A near correct wot makes me think there are no leaks, and that the injectors and pump are fundimentally fine.  Or am i wrong?  

[willys]

does it pull hard to 100mph?  if so you are fine.  For me the AF gauge is just a guide.  From what I have read, Tii's like to run rich, I make adjustments at the mixture screw (verboten screw) and the cam inside the tuna can.  As you cover the hole with the cam in the tuna can, you will run richer - it becomes a dance, one move affects another and you will then have to readjust your AF ratio at idle.  little changes in the cam location or the mixture screw at the pump will have a big impact.  Little is the operative word.

 

I am by no means an expert - but I like to drink and read others posts - 

Jeff

[gliding_serpent2]

I reread the two page tuning article i linked to on page 1.  

 

I note the same issue they note in the "captn says" section.  That is, i can set my idle, and then rev the engine, and the idle csn change a bit.  This surprises me that my advance springs might be worn, as advanced distributors redid my distributer a few years ago when the engine was done.  

 

I also did not do 1000rpm and 3000 rpm tests as they suggest.  I need two people for that, and my wife is in bed.

 

i guess my frusteration is in not knowing if i need to be fiddling with the timing, eccentric cam, or both.  

 

Also funny to read my page one observations... History is repeating itself.  

Edited May 7, 2016 by gliding_serpent2

[jimk]

42 minutes ago, gliding_serpent2 said:

My thought is that maybe this is a timing thing

Video on the dyno showing what affect A/F ratio vs timing get or don't get you.

 

[gliding_serpent2]

JimK, I guess I understand the concept of what you get form AFR's vs timing.  Power i generally best around 13:1 (engine dependent) with less losses in power as you go rich, but power drops off faster, and eventually you go off a cliff if you go too lean.  Optimal timing is based on many factors, including cams, compression, fuel.  I believe my compression should be stock for my Canadian bought car (9.5:1) and in theory my combustion chamber diameter is larger due to my oversized pistons.  The larger piston diameter should require slightly advanced timing due to longer flame propagation times.  If my compression were up, that would require a reduction in timing.  If memory serves me.  

 

I am just not sure how to evaluate if my current problem is a timing one, or a eccentric cam adjustment issue, or other.  I guess I feel like I am taking shots in the dark. 

 

One thought is that I have never tried adjusting the eccentric cam beyond the factory setting to get it to tough the 4mm pin (drill bit) in the tuna can.  Maybe I need to fiddle with that.   

 

Edited May 7, 2016 by gliding_serpent2

[gliding_serpent2]

The restoration guide talks more about the warmup regulator and adjusting that. They also talk about the base mixture screw on the pump.  I hesitate to fix that as I presume it will not fix my throttle position dependent lean issue, but rather shift the entire problem to the rich or lean spectrum.  Mind you, I may richen it a tad, given that my WOT when warm is leaner (13-13.5:1) than I would like (12.5-13:1). 

Edit, my base mixture screw is as lean as rich as it will go.  Mind you, I might need to adjust the warmup regulator washer/nut as this will influence the base mixture screw at warmup. 

 

I wish there was one resource that kind of covered an approach to it all. 

Edited May 7, 2016 by gliding_serpent2