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Right now plan is to give Cerakote a try with my airbrush when I done sanding. I will try with my airbrush and compressor I purchased when I was 15 yrs old, over 30 years ago with my lawn cutting money. Long live Chicago based Paasche airbrush company! I can still buy parts for it. Interesting that Cerakote has an air cure "MICRO SLICK DRY FILM COATING" that is the exact gun metal type color I was looking for. "Cerakote Micro Slick is used to assist with friction areas and shedding of oil." Or I will just use their regular CERAKOTE GLACIER TITANIUM which looked cools in some photos.
Tonight I started taking apart all the little vacuum lines, removing rubber elbows etc and just checking things out. Most of my rubber bits are in pretty good condition and hoping the wintergreen treatment will freshen them up a bit. A couple of observations for documentations
I bought a new vacuum actuator that operates the smaller resonance tube. My original one seems to work fine just like the new one. Very little vacuum is required to actuate. I would like to test it out with the actuator connected to the resonance flap to confirm.
On this little solenoid make sure you transfer over the plug from your West German original to the new one.
Finally the barn door Air Flow Meter (AFM). This 2.4kg (5lb 4oz) brick is a marvel for 1989. Now in 2020, not so much. I can't believe no one has made a less than 1lb drop in replacement for this thing that uses modern air flow sensing technology. Here I am thinking to polish my throttle body and the air first has to move this barn door. WTF? I wonder if it has perceptible impact on throttle response. And I do wonder if a modern equivalent would have to replicate the slow dynamics of this thing or is all that in the weeds.
There are other solutions, last i was reading about an engine rebuild and update with this company https://www.scs-delta.co.uk/ including an other ecu, injectors and plug and play.
I've contacted them, because this barn door is is slowing the gas responce.
Nice work so far, excellent progress. I’ve only owned one 964 and haven’t done any testing... <This already sounds uncredible>, but my suspicion of the slow throttle response on my car totally points to that old barn door. I imagine any type of vacuum leak would only make it worse. There is no easy replacement though without retuning the fuel maps. I am amazed that Porsche used AFM’s up to 93-94, when most manufactures switched over to MAF in the 80’s.
I really can’t wait to go speed density with no barn door and throttle enrichment from a Hall TPS. That should improve the throttle response. Next winter...
Nice work so far, excellent progress. I’ve only owned one 964 and haven’t done any testing... <This already sounds uncredible>, but my suspicion of the slow throttle response on my car totally points to that old barn door. I imagine any type of vacuum leak would only make it worse. There is no easy replacement though without retuning the fuel maps. I am amazed that Porsche used AFM’s up to 93-94, when most manufactures switched over to MAF in the 80’s.
I really can’t wait to go speed density with no barn door and throttle enrichment from a Hall TPS. That should improve the throttle response. Next winter...
Porsche was hurting back then and they got away with many things. They still used CIS on the turbos till 94. You can improve throttle response with a chip. These were tuned for fuel economy and I find driving a stock 964 a bit anemic. A good tune will improve it tremendously. No doubt the barn door doesn't help but isn't that bad when tuned properly.
There are other solutions, last i was reading about an engine rebuild and update with this company https://www.scs-delta.co.uk/ including an other ecu, injectors and plug and play.
I've contacted them, because this barn door is is slowing the gas responce.
Yes, that system has peaked my curiosity. I may reach out to them after my car is up and running fully stock. I think the '964 Refurb' thread has use of that system. And I think the same ECU system was used on the recent 'homebuilt 382whp' The benefit of this type of teardown is really understanding all the bits that make up the system, not in the abstract, but in a "hold each part in your hands" type way. Then once it is all finished decide what if anything to change.
I will be making some changes once my sunroof delete is done. We will be dyno tuning my car and haven't quite decided what to do yet. We are looking into burning our own custom chip or possibly a new ecu and using a 993 mass air flow sensor I have leftover from my track engine. . Still a month or 2 off but will post when done.
Madness... madnesss (quote from the end of the David Lean masterpiece: The Bridge on the River Kwai).
Part of the joy I get from working on these cars and holding parts in my hand and understanding their function. Dare I say the work in my garage can often exceed the driving experience. I know enough about myself to state you want me on your race crew and not in your car. Poking around the internet I found a reference to an article on the 964 intake system in Christophorus, the official customer magazine of Porsche AG. May 1990, No 223, The miracle that is the internet and in a few clicks this edition was on the way to my home. So I present to you the latest chapter in intake madness by Erwin Rutschmann and Ludwig Theilemann. It is a wonderfully fascinating look at the technology of the time and the basic principles of the resonance intake system in the 964.
Thanks for that. I have the hard copy of that issue actually all the Christophorus's from 1969 through mid 90's and recognize this issue particularly due to the full turbo on front and back cover. Now I have to go dig it out and see. Although clearly they cleaned up those parts for the cutaway. I have been following along but just realized that the aluminum intake has 2 resonance flaps vs the plastic setups one in the center. I wonder how that impacts performace
Actually they do not have 2 flaps- not mine or Ricardo's or Rob's. But maybe the very first iteration in 89 did?? I did notice that with some of the 3.8 plenums that they went back to that idea though....
I have one of those early two flap bodies here. Discussed back in this thread- post #229, if anyone wants to see the pics...
Interestingly enough, it has the same part number as the later single flap version. And the location of the passenger side flap didn't change. They simply took out the driver side flap and the bits of the mold for the bearing.
My guess, given that the springs are the same on both flaps, is that there wasn't enough vacuum pressure to open both flaps consistently and that the system was too complicated. So they eliminated one flap to make it open and close more consistently.
Interesting to note, this leaves more air volume in the driver side bank than the passenger side. And in the yet later plastic version, they moved the resonance flap to the center, making the air volume the same on both sides once again.
Thanks for posting that Ricardo!
Keep it up. When do we get to see your extrusion honed intake manifolds?
Interesting to note, this leaves more air volume in the driver side bank than the passenger side. And in the yet later plastic version, they moved the resonance flap to the center, making the air volume the same on both sides once again.
I have unbalanced volume in my intake plenum, you are driving me crazy!!!!
Well it's interesting- from that article, you'd get the sense that the length of pipe and placement of the flaps would be important.
Ricardo. Can you measure the vacuum necessary to open the flap- like you measured the actuator- but once you have reinstalled the plenum with the springs...that would be interring to see. And also if you do that with the hose installed to the actuator, you could see if the paw is too soft and collapses under the vacuum pressure. I had thought to install a stiffer tube there, but used the oem in the end.
I doubt is was an issue with having enough vacuum as it seems to me that a given vacuum would operate an infinite number of diaphragms and if a higher volume or air (less air in this case) was required they could have increased the size of the vacuum tank- which looks plenty large to me. My guess is that with one flap closed with it being a dead end so to speak the volume was not significantly "active" enough to justify the expense and added complication.
That said if I had the double flap I'd use it just because....
05-04-2020, 08:02 PM
