2.7 x-faktory PMO EFI Upgrade.

[rwest]

Hi Julian,

Thanks for taking the time to give me all the tips. I fully agree that the ITBs are super important to have perfectly balanced for the most power and smooth driving.

I absolutely love your vacuum rails and I want to replicate them at some point.

Best of luck on your car- I’m following your build as well.

Rutager

[BCLi]

Originally Posted by rwest

I really want an IAC in my system, anyone know a better way to plumb one in? I suppose that’s the reason that the high end systems use a common plenum on top of the ITBS?

Or I suppose I need a stepper on the butterfly’s to slightly open them at cold idle?

I was lucky in that I could design my system that had all of the vacuum lines connected into the same manifold, including the ITBs and the IAC. That being said, I actually capped off the IAC line since while I was struggling with the initial tune, as it was another variable. As I have no issue with starting and idle with the current tune, I haven't put it back in. This is a long way of reiterating the potential solution of a vacuum manifold that can fit all of your connections before going to the MAP sensor, rather than doing an allocation hoping for the best.

[rwest]

Hi Bert,

I can easily hook all of my cylinders and IAC up to the same manifold. Doesn’t the IAC behave like a large vacuum leak or am I missing something?

Thanks,
Rutager

[BCLi]

Originally Posted by Showdown

4.) A large manifold (with 9 ports: 6 for the ITBs, one for the ECU, one for the brake booster and one for the IAC) would be ideal for plumbing an IAC. That was the approach I was going to take until I decided on a hand throttle which has been ridiculously simple to install and operate. It also has the added bonus of being a poor man's cruise control

Originally Posted by rwest

Hi Bert,

I can easily hook all of my cylinders and IAC up to the same manifold. Doesn’t the IAC behave like a large vacuum leak or am I missing something?

Thanks,
Rutager

So I did what Julian suggested - put a large(r) manifold connection to get as much signal for the MAP. The IAC from my understanding acts as a small input of air, similar to the hand throttle, and to certain aspects of the WUR. That's why with my non-IAC'ed system, I have to use the accelerator to provide that air.

[rwest]

So, yup IAC is like a huge vacuum leak! I put it back online on my manifold with the MAP line and all 6 ITB lines and I got 94 plus kpas.

Back to the drawing board, I guess.

Open to suggestions, but really, really want this thing to start up like it was a Toyota in all temps and conditions.

Would taping another port into each ITB do the trick- one set doing IAC and the other getting a MAP single?

Open to all suggestions not involving hand throttle or holding the pedal slightly until it holds idle- sorry guys!

[al lkosmal]

While I prefer the simplicity of the hand throttle, an IAC will work very well, if calibrated properly. It is not like a huge vacuum leak unless it is wide open to its air intake/filter. consider it a controlled amount of air that gets introduced into the intake...and you are in control. The amount of air that it lets into the system is up to you and is based on the calibration that you apply. So, if it's open, it is most likely because your current calibration is telling it to be open. The intent is to have the IAC open a bit during cold starts, tapering off to closed (or very close to closed) as the engine warms. If , when you have it plumbed in you are at 94kpa.....it is very likely that the IAC is wide open, instead of partially or fully closed......it will introduce as much, or as little air as you want....and that, combined with a richer mix, tapering off as the engine warms will make it start/idle ....somewhat like a Toyota or any other car that uses an IAC for cold starts.. You're really trying to get it to emulate what you do with a hand throttle and the pedal.

[rwest]

Originally Posted by al lkosmal

While I prefer the simplicity of the hand throttle, an IAC will work very well, if calibrated properly. It is not like a huge vacuum leak unless it is wide open to its air intake/filter. consider it a controlled amount of air that gets introduced into the intake...and you are in control. The amount of air that it lets into the system is up to you and is based on the calibration that you apply. So, if it's open, it is most likely because your current calibration is telling it to be open. The intent is to have the IAC open a bit during cold starts, tapering off to closed (or very close to closed) as the engine warms. If , when you have it plumbed in you are at 94kpa.....it is very likely that the IAC is wide open, instead of partially or fully closed......it will introduce as much, or as little air as you want....and that, combined with a richer mix, tapering off as the engine warms will make it start/idle ....somewhat like a Toyota or any other car that uses an IAC for cold starts.. You're really trying to get it to emulate what you do with a hand throttle and the pedal.

Hi Al,

What box do I adjust to get a smaller opening?

Thanks,
Rutager

[Showdown]

The IAC will be controlled by the ECU.

Setup depends what IAC valve you have but unless it’s an open/closed variant it’s likely a stepper valve, and you create a curve based on temperature- that’s an open loop. A closed loop is more complicated as it constantly adjusts the IAC valve to try and maintain an certain idle speed.

You need to find out what IAC valve you have and get the calibration specs from the manufacturer or I guess, set the calibration in tunerstudio while looking at the valve or with the engine running so you can see when it’s fully closed and not allowing air to leak in. Then you can start building your curve to allow the air leak based on the engine temp. Of course you’ll need to make sure that your engine temp sensor is accurate too.

https://www.diyautotune.com/support/tech/other/idle-tuning-megasquirt/

[al lkosmal]

rutager,
your IAC valve is a stepper type and there is good information regarding the setup and testing of this type of IAC valve, both in the MS2 manuals and on the DIY Autotune website.
Here is a link to a good article by DIYAuttune, that will help you gain an understanding of how to get your IAC working.

https://www.diyautotune.com/support/tech/other/stepper-iac/

regards,
al

[rwest]

Thanks Al and Julian.

I’ll read up.

Here’s where I was/am, got the car working with no IAC in circuit and then a short time of giving it slight gas. I put the IAC in circuit and it would start and rest at 950 without any throttle input. IAC fed into ITBs 1,3,4 and 6 with 2&5 feeding the MAP sensor. MAP showed 50-54

Jamie mentioned that my MAP signal was bumpy and likely from an imbalance in my ITBs- I had thought they were just about even, so I thought maybe I wasn’t getting enough cylinders “weighing” in, so turned off IAC and ran all 6 ITBs to MAP and got a very smooth line and a car that drove nicer. MAP showed 54-60

Next step was to turn the IAC back on- now all 6 ITB vacuum lines are on the manifold as well as the IAC and MAP. Start up was difficult, super rich and needed constant pedal input- MAP showed 94.

So big question is can the IAC, MAP and all 6 ITBs live on the same manifold?

Thanks,

[al lkosmal]

Rutager,
The IACs I've installed and others that i've seen have all been plumbed into the same vacuum manifold as the ITBs.
I think that your experiment was a good one. If after adding all 6 ITB vacuum lines to the manifold, your map signal straightened out, it is likely due to having more signal averaging, resulting in a smoother signal. It also shows that your ITB balancing is not causing the bumpy MAP signal.
So, you could go back to your previous arrangement...if that was/is working for you...or continue with all 6 ITBs and the IAC plumbed to the vacuum manifold.......it is not clear if you have verified that your IAC is actually working. Based on your questions, you have not really tested or verified that.
I would recommend that you start there and.... at least that variable will be eliminated.
However, as I recommended from the start.....I would focus on getting your engine cold starting very well, so that it fires up with a single smooth pedal effort and will keep running with the throttle held open a bit until warm......this will verify that you have the cold start fueling correct, or close to correct....then I'd plumb the IAC in to emulate what you were doing with your foot.....I.E. adding cold start air, combined with cold start fuel.....

[rwest]

Hi Al,

Yes, I had disconnected the IAC until I got it idling with very light throttle application, so now I am adding it back into the equation.

Much earlier in the process, I verified that the IAC was open at start and closed once the engine warmed up, but as we all know, things change... today after it was warm, my finger was still getting sucked down on the intake, although it didn’t change the engine running.

I used the CAN bus testing function and with the IAC out of its port verified that it moved; except it moved to the piston separating from the valve! I got it back attached or at least it appeared to be and the CAN test on a running motor showed that it does operate and no finger sucking at closed.

Is that normal for the shaft to separate, or should I source a new part and do you remember the model? I think it might be the Jeep type?

Rutager

[al lkosmal]

Rutager,
I do believe that it is normal for that type of IAC to shoot the piston out of the motor assembly, if it is not assembled into the valve block, which stops/contains the travel of the piston at the closed end.

regards,
al

PS: From the DIY website:
Part Numbers for Compatible Valves (provided by DarkStar):
Niehoff Part# 21774 (this is what was used in all testing)
Wells AC320
OEM Application of this valve: 1991-1997 Jeep Cherokee, Grand Cherokee, Wrangler and Comanche (including submodels) w/ 4.0L Inline 6 VIN S

[rwest]

Well, the car hasn’t burned down accidentally or on purpose yet, but it sure is frustrating. I like to wrench, but not so much computer tuning especially since I only have a rudimentary understanding of what I’m doing.

I haven’t done much lately as we had a few warm days and I had some kitchen cabinet drawers that needed to be built so I could hang them out in the yard to spray the finish on. That is done and the temps are going back down, so I went back to the linkage...

Taking the ball joint rods off and swinging the crossbar down to the ITB ball showed large discrepancies in how the cross rod balls lined up with the ITB balls- regular adjustments didn’t help, so I slightly bent one arm, enlarged one set of mounting holes and added washers between one mount and the ITB body and now I’m lining up side to side nicely, but front to back has a slight gap on the drivers side so I will need to slot one of the mounts so I can get both sides identical.

Once that is accomplished, I will once again take by beloved IAC out of the picture and re-load an earlier tune. I have come to the conclusion that in my current setup, the IAC is not compatible with driving away from a stop- if the IAC is set up to hold idle on a cold start, it is about 3 times too lean in the section of the table that comes into play when driving off from a stop. Need a plan “B” or “C” or whatever letter I’m at now!

[Showdown]

Hand throttle is your answer. Purely mechanical, no wires, no computers, no funny stuff.

I sent this to another member but I'll post here for posterity, its specific to my 1977 with two heater levers and no stock hand throttle, but I'm sure it is applicable to many more cars:

Below are the parts I ordered:

1 x 901-424-037-00-OEM
1 x 901-424-317-00-M100
1 x 911-424-735-04-OEM
3 x 911-424-737-00-OEM
1 x 911-424-792-00-M253
1 x 999-523-006-00-OEM
1 x N-011-524-27-OEM
1 x N01-243-51-OEM
1 x 911-424-519-02-OEM (this is part 17-1 I reference later)

I've attached an annotated portion of the Porsche PET for 1974-1977 showing the handbrake assembly and the parts number. The stuff in the red circle is what you're using/building. The blue "X" are parts you don't need (#16, the spacer wasn't needed for my car- a 1977 but you might need it, I don't know) and finally, the stuff circled in green is NLA.

Part 23-2 is something that you'll need but it's also NLA. This is the part I had to make myself. Luckily, you already have one on the other side by the heater levers so you can make a copy from that. It's not all that hard with an angle grinder or metal saw and some pliers... I'm sure you could model one up and have it 3D printed or fabricated by SendCutSend but that seems like so much more work...

The other part that you need that's NLA is 17-1. This is also needed. Now, Pelican and Stoddard sell the part "911 424 519 00" but though it looks right, it's too short by about 1cm and that makes a huge difference; it works fine for card with one lever for heat control but not two. I cut off one of the threaded ends (on the right) and welded on a threaded metric bolt (after first cutting the head off the bolt) and that gave me the extra length I needed. If you have a mill and a lathe you could just make one of the bolts out of solid stock but I don't have a lathe and welding was a 5 min job. Again, this could be made by a machine shop but it was so much quicker to just weld it up.

Here's the link for the throttle rod collar:
https://www.thingiverse.com/thing:5447656

I printed it out of steel, aluminum and carbon reinforced nylon using Shapeways. The steel was not accurate enough, the aluminum was great but I lost it! and the nylon was what I ended up using. The opening for the throttle rod needed to be filed open a bit (like the thickness of two sheets of paper) but it's doing just fine. My design uses two set screws as opposed to Porsche's one... I figured why not double insurance. Those will have to be tapped. I ordered the screws and tap from McMaster-Carr:

https://www.mcmaster.com/catalog/128/3371
https://www.mcmaster.com/catalog/128/2793

Installation is a PITA and I did it with the seats in place which was stupid, but I'm a glutton for punishment; remove the driver's seat!

Be careful to not accidentally detach the heat levers or the parking brake as that will make your life much less pleasant...trust me, I know.

Best of luck and enjoy the hand throttle- it's super cool and also poor man's cruise control . (actually, don't use it for that, the parts can probably handle it but after you install one you'll understand why the notion of replacing it due to wear is a scary one)

[BCLi]

Originally Posted by Showdown

Hand throttle is your answer. Purely mechanical, no wires, no computers, no funny stuff.

I sent this to another member but I'll post here for posterity, its specific to my 1977 with two heater levers and no stock hand throttle, but I'm sure it is applicable to many more cars:

Below are the parts I ordered:

1 x 901-424-037-00-OEM
1 x 901-424-317-00-M100
1 x 911-424-735-04-OEM
3 x 911-424-737-00-OEM
1 x 911-424-792-00-M253
1 x 999-523-006-00-OEM
1 x N-011-524-27-OEM
1 x N01-243-51-OEM
1 x 911-424-519-02-OEM (this is part 17-1 I reference later)
...

Awesome. Wonderful if you can fabricate the NLA parts.

[rwest]

Originally Posted by Showdown

Hand throttle is your answer. Purely mechanical, no wires, no computers, no funny stuff.

I sent this to another member but I'll post here for posterity, its specific to my 1977 with two heater levers and no stock hand throttle, but I'm sure it is applicable to many more cars:

Below are the parts I ordered:

1 x 901-424-037-00-OEM
1 x 901-424-317-00-M100
1 x 911-424-735-04-OEM
3 x 911-424-737-00-OEM
1 x 911-424-792-00-M253
1 x 999-523-006-00-OEM
1 x N-011-524-27-OEM
1 x N01-243-51-OEM
1 x 911-424-519-02-OEM (this is part 17-1 I reference later)

I've attached an annotated portion of the Porsche PET for 1974-1977 showing the handbrake assembly and the parts number. The stuff in the red circle is what you're using/building. The blue "X" are parts you don't need (#16, the spacer wasn't needed for my car- a 1977 but you might need it, I don't know) and finally, the stuff circled in green is NLA.

Part 23-2 is something that you'll need but it's also NLA. This is the part I had to make myself. Luckily, you already have one on the other side by the heater levers so you can make a copy from that. It's not all that hard with an angle grinder or metal saw and some pliers... I'm sure you could model one up and have it 3D printed or fabricated by SendCutSend but that seems like so much more work...

The other part that you need that's NLA is 17-1. This is also needed. Now, Pelican and Stoddard sell the part "911 424 519 00" but though it looks right, it's too short by about 1cm and that makes a huge difference; it works fine for card with one lever for heat control but not two. I cut off one of the threaded ends (on the right) and welded on a threaded metric bolt (after first cutting the head off the bolt) and that gave me the extra length I needed. If you have a mill and a lathe you could just make one of the bolts out of solid stock but I don't have a lathe and welding was a 5 min job. Again, this could be made by a machine shop but it was so much quicker to just weld it up.

Here's the link for the throttle rod collar:
https://www.thingiverse.com/thing:5447656

I printed it out of steel, aluminum and carbon reinforced nylon using Shapeways. The steel was not accurate enough, the aluminum was great but I lost it! and the nylon was what I ended up using. The opening for the throttle rod needed to be filed open a bit (like the thickness of two sheets of paper) but it's doing just fine. My design uses two set screws as opposed to Porsche's one... I figured why not double insurance. Those will have to be tapped. I ordered the screws and tap from McMaster-Carr:

https://www.mcmaster.com/catalog/128/3371
https://www.mcmaster.com/catalog/128/2793

Installation is a PITA and I did it with the seats in place which was stupid, but I'm a glutton for punishment; remove the driver's seat!

Be careful to not accidentally detach the heat levers or the parking brake as that will make your life much less pleasant...trust me, I know.

Best of luck and enjoy the hand throttle- it's super cool and also poor man's cruise control . (actually, don't use it for that, the parts can probably handle it but after you install one you'll understand why the notion of replacing it due to wear is a scary one)

Thanks Julian,

I haven’t given up on my IAC yet...

[rwest]

So, been a bit as this has lost its fun... took a break to get home projects done and regroup.

I spend a bunch of time trying to get the linkages to be equal on both sides and can’t believe how bad the factory parts fit; I had to bend the crossbar slightly and enlarge the begeezus out of the holes to get the balls to be equally spaced on each side, but I think I’m there. Here’s how much I had to enlarge and slot the passenger side and I also had to make the holes one size bigger on the driver bracket.

Raining right now so I can’t see where my 3,000rpm sits yet.

[al lkosmal]

Rutager,
I've pretty much had to mod the PMO cross bar mounts on every install. First time I ran into the need to do that, I called Richard Parr to explain the problem and thought maybe there were different mounts for different years....but he basically told me to "just slot the mounting holes".......which I did. But like you, I was a little surprised that it was required. That being said, although it was a small PITA....it was one of the easier mods I've had to do when installing EFI.


regards,
al

[rwest]

So, I slotted the bracket to within inches of its life and got the cross bar balls to end up identically on each side in how they ended up near the ITB balls. I then made the linkages the exact same length and... it turn out the crossbar doesn’t swing symmetrically and the linkage was a 1/4” different to the bar on one side.

Back to the drawing board and I attached the linkages to the balls without changing their lengths and then adjusted the brackets so everything was sitting properly.

Live and learn.

I warmed the car up and balanced it at 3,000rpm.

This morning I decided to fill up with gas and then do some more auto tuning. Yea, right, apparently I had a lot of lean spots and everyone with a car was on the road too; luckily I was able to bounce from church parking lot to ice arena lot to nursing home lot to get out of traffic and do enough tuning to get back home.

I had a weird random problem where sometimes when I went to drive off from a stop, it would bog down badly, go super lean and want to die in the middle of the road. Didn’t always do it, but when it did, there was another car coming- of course.

May try tomorrow morning early.