When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Here are some additional pics as I installed mine today too.
Here's what my AAV plumbing looks like currently. Just a plastic connector between the 2 sections of rubber hose. Here's a 90 Holley jet before threading into the restrictor fitting. Threaded all the way in Restricted opening Restrictor fitting installed in place of the plastic coupler Wider view in engine bay
I did some other work today that had me disconnect the fuel line from the cold start injector and the injectors on 5-8 so the first cold start after install had a low and unsmooth idle, but I think that's from the Fuel lines being empty. I'll try it again next time I drive the car and see if I need to change the jet size for my setup.
Hi Pete,
Carl raised the issue of your K-jet AAV having a different aperture than my L-jet AAV. If that is true, you may need to adjust. As a test piece, I thought of putting a piece of aluminum foil duct tape over the AAV hose nipple, then punching a hole in it. Then put the hose over that, and test warm up idle. Keep dilating the hole in the tape until you get the idle you want. Then build to that size.
If the empty fuel lines are the problem, not a different AAV geometry, then you should be fine eventually.
Good luck, and thanks,
Dave
Damn great idea, you two. Pete, your sample arrived here today and I thank you for it. It's well made, and I love the idea of exchangeable orifices using Holley carb jets. This thing is super-easy to install too, going right in the hose like it does. Smart!
Damn great idea, you two. Pete, your sample arrived here today and I thank you for it. It's well made, and I love the idea of exchangeable orifices using Holley carb jets. This thing is super-easy to install too, going right in the hose like it does. Smart!
Glad it received the Carl Fausett stamp of approval and that you like it. Happy to provide something to you for all the assistance you've provided to me over the past few years of my 928 ownership !
Damn great idea, you two. Pete, your sample arrived here today and I thank you for it. It's well made, and I love the idea of exchangeable orifices using Holley carb jets. This thing is super-easy to install too, going right in the hose like it does. Smart!
Thanks, Carl. Not only has Pete developed this idea, remember he made a practical cold air intake for the supercharged 16V engine. I have a few ideas but Pete really has ideas, and he can execute them at a high level.
Good luck,
Dave
Hi guys,
The cold start/AAV system worked perfectly at 40 degrees F. tonight, 1100RPM dropping to 800RPM when warm. Now when the weather gets warmer, I can drive the car more regularly, and make any tweaks that are needed. So far, this is a big improvement over the high 2000RPM warm-up idle I was experiencing.
Good luck,
Dave
Quick Update....the K-Jet AAV must be quite different from the L-Jet AAV as Carl mentioned, as I tested mine today and with the 90 restrictor jet (0.090") installed the car dpesn't start or run well at all without milking the throttle pedal. Once it warms up again it's a perfect idle at 800 RPM where I have it set so definitely just tied to the restrictor that's installed. I've ordered 120, 135, and 150 jets to try a significantly larger opening. Until they arrive, I might just remove the jet and run it with the empty opening in the restrictor assembly. Figure that will still be too high, but better than the rough cold start until I get the orifice size dialed in.
I'm also curious as to why Dave was getting a high 2000 rpm cold-start. I've never had that on a supercharged 16v L-Jet. It's peculiar. That said, he has it adjusted where he likes it now, and the adjustment came by putting a restrictor in the hose. No argument there. Just a curiosity to me.
Sorry, Pete. I was afraid there might be a L-jet/K-jet AAV difference as Carl indicated. Hopefully a larger orifice will solve the issue.
Good luck,
Dave
Hi Pete,
You might try the same experiment that I did. With standard AAV, no restrictor, jumper your fuel pump relay for 5 minutes. Fuel will recirculate to the tank. Engine will stay cool. AAV will close due to bi-metallic strip that controls its aperture. Start your car, and see what RPM you get, and what are the idle characteristics. You could use different time periods of AAV heating, to get several data points. Your valve is very accessible, so you could even look at the valve to see opening size. That may help you determine restrictor size. Just an idea.
With your generous production of these restrictor, I would have thought you had banked some big karma. Maybe it just has to be scaled to the opening of your AAV spec.
Good luck,
Dave
Hi guys,
My car is functioning well. The cold start system with AAV are working as I want.
I was wondering why I had this high RPM warmup problem in the first place, and also why Pete did not have the same results as I did with the same flow restrictor. I need to take a few things apart to prove my theory, but here's what I'm thinking:
The AAV that I'm using is a used replacement from 928 Intl. They list their item as 1978 thru 1984. However there seems to be a difference between early and late valves. 84 ends in 02. 80 ends in 00, and I don't know what the PN is for Pete's 78. Carl seemed to have spotted a difference in a picture of the aperture. So maybe my replacement is an old one with a larger aperture. My restrictor simply converted it to something more like the later valves. Now mine works fine. Pete's 78 needs a larger aperture so the restrictor didn't work the same. If I had the correct AAV maybe I wouldn't have had the high RPM warmup in the first place.
Update: With an endoscope I see the current Bosch number ends in a round number such as 8 or 9. My old valve was the proper one Bosch number 0280.140.227, so that fits with my theory. I would have to see them both side by side to inspect their apertures.
Since my car is running great, I'm reluctant to pull the spider to get to my AAV to check for PN, but the next time I will.
Thanks,
Dave
Last edited by j.kenzie@sbcglobal.net; 04-18-2020 at 02:59 PM.
Here's a photo through the AAV from another recent thread where the owner is doing a Top End Refresh on a '78. This is at rest without power to it. Thought it might be of interest since it shows the cold aperture opening.
Here is a picture of the 1984 spare AAV from my L-jet car. Not sure if the total aperture area is smaller than the K-jet or not, but I think so. Furthermore it closes in two sections: the full window, then the smaller slot. When I powered it the first 2 minutes closed the full window, then two more minutes until the tiny slot was closed completely.
Thanks,
Dave
Last edited by j.kenzie@sbcglobal.net; 04-18-2020 at 05:43 PM.
Update on mine. I completely removed the jet from my adapter and the cold start idle is still too low. Took one of them and drilled the orifice bigger. I think I'm at 7/32" and on the first test I did, think I'm good. Cold idle was about 1,100 when it used to be 1,800 but I've only cold started it once. It's the first time that it didn't start and die though since installing the restrictor.
I'll update the thread again after the next cold start and let you know if I'll be going 1 drill bit larger through the restrictor.
Good news, Pete. You certainly deserve a good result. Hopefully you style of AAV/cold start system just needs a slighlty larger restrictor.
Thanks,
Dave
Update
Mystery solved:
Well, my AAV + restrictor has been working fine. However, it has bothered me that this was needed to make the car behave like I wanted. I mentioned that the AAV I am using was a replacement from 928 Int'l. It behaves properly when 12 volts is applied, and their website only shows one entry for AAV's. Carl, earlier, had pointed out that there is a difference between the AAV on a CIS car and an L-jet car. This made me wonder if I had put a CIS AAV into my car, without knowing it. I decided to pull the intake spider and pull the AAV. I found it is indeed an inappropriate CIS model, with a much larger orifice. So my restrictor essentially converted the CIS model to an L-jet AAV. This gave the proper warmup behavior.
I decided to put the original L-jet AAV back in place and see how it worked. Well, low and behold, it works perfectly. God knows why I swapped it, but it didn't seem to do much, and it was too much trouble to revert to the old one, since I didn't know it was any different.
Now I have the proper, original AAV in place. Startup is fine. Warmup goes from 1100 RPM to 850 RPM in about 3-4 minutes. Just like I wanted.
So I was right and wrong at the same time. A couple of you guys said they didn't like fixes like I did without know the root cause. Now I see why. I had the wrong AAV, and I added a "wrong" fix, to end up with a rightly functioning system. Could have been avoided, and could have been much simpler just to examine the AAV to begin with. I guess it was just inconvenient enough that I started down a crooked path.
Above is the larger orifice on the CIS AAV.
Picture above shows the reduced orifice on the L-jet AAV. Both valves are in the full open, cold condition. Both valves close completely in 3-4 minutes when 12 volts are applied.
Thanks for your patience,
Dave
03-22-2020, 06:37 PM
