A little experiment, Ljet cold start Options

[Van B]

@Porschef my original tested good. It heated up, I cleaned it and everything moved from full cold in the freezer to heated while connected to 12v. Looking back, I never confirmed the actual amps sent through the harness. So, when connecting to a battery for testing, it’s possible I was giving it more current than it would normally receive.

That said, I think that 50yrs of heat cycles had fatigued the spring steel and probably the heating element… it was tired and needed to be retired.

There was a considerable amount of time where I was convinced that my AAV was fine. But changing the part was night and day. But the journey was good, because I found a lot of DAPO items that needed to be addressed… like spark plugs that didn’t seat lol.

[Van B]

BTW, your AFRs are perfect!

[Porschef]

BTW, your AFRs are perfect!

Thanks, it does seem happy there. And no pinging since the 123 install.


I only ask to verify the functionality of your original AAR because I’m somewhat reluctant to pull the trigger on the BMW unit unless it’s virtually certain to remedy this last little bugaboo. But seeing that you also did the same bypass (and here I was thinking it was a original idea of mine (IMG:style_emoticons/default/rolleyes.gif) ,not so much) and got the same results does make me wonder.

Anyway I’ll look into it Monday. Thanks (IMG:style_emoticons/default/beerchug.gif)

[Porschef]

@Porschef

There was a considerable amount of time where I was convinced that my AAV was fine. But changing the part was night and day.

Got it (IMG:style_emoticons/default/beerchug.gif)

[StarBear]

Thanks for the summary @porschef .
Based on your numbers, looks like I might still be running a tad rich at rpms.
Will do another little experiment and temporarily install a borrowed larger BMW AAV and report back. (IMG:style_emoticons/default/biggrin.gif)

[Porschef]

Thanks for the summary @porschef .
Based on your numbers, looks like I might still be running a tad rich at rpms.
Will do another little experiment and temporarily install a borrowed larger BMW AAV and report back. (IMG:style_emoticons/default/biggrin.gif)

Great! Looking forward to the results (IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

(ps i just read a story that the b52s are going to be stationed in darwin and they are expanding the runways. might have to take a trip up north and watch them take off, never seen a b-52, what a plane. seen a f-117. but never a b52. things are getting interesting down here in the southern hemisphere. too old to join the airforce, but it sure is getting kind of curious and reassuring down in these parts). (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/beer3.gif)
keep up the good work on the paint specs etc. at least some of us care about it.

Back in the 80s, Carswell Air Force Base in Fort Worth (Now Carswell Joint Reserve Base) was a SAC base with B-52s on alert there 24x7. When I got my pilot's license, the field was due north of Carswell. We would be up flying and an alert would come on the radio, and we would have to vacate the airspace at maximum speed either east or west. The B-52s were scrambling and headed out at max speed in 2 second intervals. It was an an awesome site watching all the BUFFs headed out like someone kicked an anthill.

FYI... and the BUFF is the nickname for the B-52. Big Ugly Fat Fellow/F**ker. It is amazing that a military airplane that had it's first flight in 1952 is still operational in 2023. I read an article online a while back about how a new B-52 pilot was assigned to the same plane his Grandfather had flown when it was new.

(IMG:style_emoticons/default/hijacked.gif)

i wouldn't classify that as a hijack or off topic. but not an administrator or mod. (IMG:style_emoticons/default/smile.gif)

strikes me the bee five two ( (IMG:style_emoticons/default/smile.gif) auslish) is just like a 914 (nine one four).
rebuild rebuild rebuild. keep the air frame going.
because its.............just so good?
not that i would really know, but it must be or the USAF would not bother?

classic. also the 914 was once considered ugly. (still is in some circles?).
so the car and the plane have a lot in common.

huge fan base as well?.

(IMG:style_emoticons/default/beer.gif) (IMG:style_emoticons/default/beerchug.gif)

[Geezer914]

Rock Auto 1988 BMW M5 idle air control valve $215.79

[Porschef]

Rock Auto 1988 BMW M5 idle air control valve $215.79

Thanks, yes, I saw that, I’m gonna wait to see how Steve’s swap goes.

(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/biggrin.gif)

Oh, the suspense...

[Geezer914]

I second that.

[wonkipop]

down here in north antarctica we have this bloke here.
he is up north in queensland.


my mechanic mike found him.
but he doesn't really sell new/replacement. he is an exchange reconditioner.
he wants mne on exchange basis.
which i am slightly reluctant to do.
but what am happy for him to do is sort out one i can find on something else.
ie a SAAB or BMW.
apparently he has the original airflow and time duration specs for all the different models.
so theoretically he might be able to adjust one from another model to suit the 914.

https://k-jet.biz/auxiliary-air-valves/

[Porschef]

Very interesting Wonk, that’s the site I used to pick off both the Bosch and BMW part numbers… (IMG:style_emoticons/default/beer.gif)

Just waiting for the results from StarBear before the next step (IMG:style_emoticons/default/smile.gif)

Thanks (IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

Very interesting Wonk, that’s the site I used to pick off both the Bosch and BMW part numbers… (IMG:style_emoticons/default/beer.gif)

Just waiting for the results from StarBear before the next step (IMG:style_emoticons/default/smile.gif)

Thanks (IMG:style_emoticons/default/beerchug.gif)

apparently he is a genius.
working away in his little shop.
i have no doubts as to his credentials.
but i just don't want to be left AAV-less if some kind of accident happens.
like lost in the mail.

so i will only be sending him a sacrifice he can cut the head off and eat the flesh of ancestors (which happens the closer you get to papua new guinea! (IMG:style_emoticons/default/beer.gif) )

[StarBear]

Here are the results of the AAR temp tests - OEM Bosch/VW 101 vs NOS Bosch/BMW 125 units:

The BMW unit starts with a much bigger opening (expected). When 12V source applied, while the 101 unit is closed completely at about 2 minutes the BMW unit is maybe 80% closed. In 20 minutes the BMW unit was still just a tad open, but that can be adjusted by the little screw on the backside (I didn't, as it's a borrowed unit).

Videos of warm up with Bosch 101 unit coming soon in another (or a few) post). Videos and results of Bosch BMW unit after I swap it in and fire it up.

[StarBear]

Results of current AAR (Bosch/VW #101) unit testing during warmup provided below.
Air temp 80F, 65% humidity, in the shade.
Dwell 48 degrees; Timing a bit advanced with red line about 1/2" to the right of the V notch.

@15 seconds - ~600 rpm; idle not stable
@1 minutes - ~600-650 rpm; idle not stable
@2 minutes - 700-750 rpm; idle not stable
@3 minutes - 800-850 rpm; idle not stable
@4 minutes - 900 rpm; idle stable
@6 minutes - 950 rpm; idle stable
@7 minutes - 950-1000 rpm; idle not stable
@9 minues - 1150 rpm; idle stable.

Otherwise, I just let it sit for a minute in the driveway, then with stumbling idle I back into the street, and take off happy as a clam. Idles fine and stable by the time I get to the end of the block.

A great 30 minute run this A.M. with cassette of Doobie Brothers and Jefferson Airplane complementing the air-cooled engine sound perfectly.

Have tried to post videos of the engine analyzer but dont have software to edit and reduce file size (or site doesn't load .mov files)

Will install the borrowed BMW unit in later today and post results. Stay tuned (pun intended)!

[Porschef]

A little Sunday afternoon suspense...that’s pretty much what I got going on from a cold start. Read through a couple old BMW forum threads that showed a small adjustment to the AAR making a difference. The pics look encouraging.

I’ll be here waiting (IMG:style_emoticons/default/biggrin.gif)



(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/popcorn[1].gif)

(IMG:style_emoticons/default/smile.gif)

[StarBear]

Ok; second test, with bigger BMW AAR. What a difference!!!! Here’s the data:
Temp 84F; 45% humidity. In shade.
Started right up with authority. Way up to 1500 rpm. Turned TB idle screw down to 1000 rpm.
15 secs - 1200 rpm idle stable
1 min - 1000 rpm. Idle mostly stable; a bit of swinging.
2 min - 925 rpm. Idle stable.
3 min - 920 rpm. Idle stable. Opened TB screw 1/4 turn
4 min - 920 rpm. Idle stable. Opened TB screw another 1/4 turn
5 min - 940 rpm. Idle stable
6 min - 920 rpm. Idle stable. Opened TB screw another 1/4 turn
7 min - 880 rpm. Idle stable. Opened TB screw 1/2 turn
8 min - 900 rpm. Idle stable.
Opened TB screw to set at 1000 rpm.

Will let it cool a while then do a third test with the initial TB screw set at desired final idle rpm.

One thought - maybe this BoschBMW AAR is better aligned with my new Bosch AFM, while original AAR is better aligned with my original (failed temp sensor) AFM?

Stay tuned for the thrilling concluding episode!

[Van B]

@StarBear , you gotta set the TB air screw when the engine is at full operation temp ( after driving) and then leave it. Otherwise it just remains a variable. That's how I discovered that my TB is worn with the infamous groove. Once I left the adjustment screw alone, I knew the slight variation in idle had to be coming from a change in metered air flow.

[Porschef]

Very promising Steve!! (IMG:style_emoticons/default/piratenanner.gif)

Couple things, and I could always be wrong... Your ultimate idle speed shouldn’t be affected, so I’d think that closing down the AAR opening with the nut would be the ticket to bringing down the initial start RPM’s . I understand why you wouldn’t want to as it’s a unit you’ve borrowed. If it’s remaining open just a hair that’d bring the idle up, but also let in unmetered air that you don’t want.

Second, I don’t think your AFM would know the difference, it’s kinda like a few components working as one. But yeah, looks really good! (IMG:style_emoticons/default/beerchug.gif)

Thanks for all the info (IMG:style_emoticons/default/smile.gif)


*Edited* What Van said!

[StarBear]

@StarBear , you gotta set the TB air screw when the engine is at full operation temp ( after driving) and then leave it. Otherwise it just remains a variable. That's how I discovered that my TB is worn with the infamous groove. Once I left the adjustment screw alone, I knew the slight variation in idle had to be coming from a change in metered air flow.

Yep; will do the third test then a short drive to confirm all and do final TB screw setting.