Hi Everyone, I'm wondering if anyone who knows the operation of the air injection system on a Ferrari 308QV can assist with this question. The basic operation I think is pretty clear from the diagram below, but I was wondering if someone could tell me what activates solenoid #2 and what the pressure switch diaphragm #18 does? Thanks in advance, BB
Electrovalve #2 is controlled by the water thermoswitch mounted in the coolant expansion tank (item #64, 121777, on TAV 18). When cold, the water thermoswitch is closed which actuates Electrovalve #2, which allows vacuum to reach the cut-off valve #1. This opens the cut-off valve allowing air from the airbox to be drawn into the pulse air injection system. (When warm, the water thermoswitch opens = unactuates Electrovalve #2 = no vacuum reaches cut-off valve #1 = cut-off valve closed = air injection system disabled). Differential pressure switch #18 is not part of the pulse air injection system -- it just uses the same intake manifold vacuum source for its operation. If the intake manifold vacuum drops quickly, a set of contacts inside the differential pressure switch close briefly = actuates the cold start injector briefly (but only during cold-running IIRC) = gives a squirt of fuel into the intake manifold. This is similar to how the accelerator pump on a carburetor works (i.e., adding a squirt of fuel if you open the throttle quickly).
Thanks Steve. I knew you'd have the answer A follow up to this, is there any benefit of the air injection system if I'm not running a cat? Or are the two not interdependent? Thx BB
I'd say this as "there's virtually no performance penalty with the pulse air injection system being in place". The nozzle doing the air injection does not obstruct the cyl head exhaust port (like it does on the US 2V models), there's no belt driven air pump, and it only operates during cold-running. No benefit to removing it, and just makes the car more incomplete IMO (but, without a cat, it could be removed with no functional issues).
However, when left in place, the injection pipes and sampling ports tend to collect water and rust to hell. Then it causes an exhaust leak, as well as being impossible to remove.
+1 -- I should've included: either 1) leave it all in place and working, or 2) remove everything, including replacing the air injector nozzles with the appropriate threaded plugs.
Thanks gents. You both make solid arguments. My sampling ports were removed by previous owner, and I always found the engine bay of the 308 very cluttered. So always looking to remove useless junk
For the older systems, with air pump and diverter valve, for roughly how many minutes is air injected at the exhaust manifold before the diverter valve diverts it to the cats? Is air injected at the exhaust manifold only when the engine is cold or are there other situations?
See page 74 in your 260/83 OM for the description of the system operation (it's a coolant temperature thing that triggers the changeover, not time)
I’m going down the same route. I’m just thinking on how to reach the air injectors from the front bank without removing the engine. Let me know the progress please Sent from my iPhone using FerrariChat
I don't know about collecting water but the air injection manifolds on the '83 models are going to "rust to hell" no matter what you do. On the '84 and '85 models they went with a much improved manifold that I believe is stainless.
Ricambi America carries them for both QV (QVAIP): https://www.ricambiamerica.com/qvaip-308-4v-air-injection-plugs.html and 2-Valves (308AIP): https://www.ricambiamerica.com/308aip-308-2v-air-injection-plugs.html
Hi Nuno, At this point I've just removed items #1, #9, #10, #11, #12 and #14. I've put a blanking cap on tee piece #8, blanking cap on port of #2 and on the bottom of the airbox. This gave me more room to work near the oil adaptor housing and cooler line, and cleaned up some of the messy hose work. Hose #11 was saturated in oil so it was good to say goodbye to it! I'm going to tackle the air injection ports once I have the plugs in hand. Not sure how hard the front will be? Between access issues and how corroded on they might be .... it will be an adventure into the unknown BB
Hello and Happy 4th, Hoping to get some more info on this topic in this thread as it looks like a few of you have do this by now. Otherwise I'll post a new thread... On my 1984 308 QV US, I just put my engine back in and I'm in the process of reconnecting everything. However I did remove the injection tubes while it was out. I plugged the holes with the correct plugs (from unobtaniun). And I plan to do the following unless there are any other things I need to know, or do differently.... I wont put the cut off valve and various associated hoses back in, nor the solenoid and its small hoses. I'll plug the two holes where two hoses go, one under the airbox and the other under the throttle body. I do have a question about electronics: Are there any wire connections that need to be disconnected or modified? Am I missing anything? Advice and direction appreciated, Marc
All I've ever heard about removal of the air injection injectors is that it is a nightmare. I'd love to hear some step by step advise on this. I can't believe at 70 years old I'm going to attempt this. Last year I did timing belts and it took me a week..........mostly because of back pain. The first time I did them was 8 hours!!!!!!!
The 2-valve air injection nozzle can be much more difficult to remove because it extends farther into the exhaust port, and the end of it can deform such that it can't be withdrawn out the same hole in the cylinder head that it was installed thru. The 4-valve air injection nozzle is less troublesome. The attached article describes the steps that I had to use to (destructively) get my ex-308 2-valve air injection nozzles out. What F model are you working on? Of course, in both cases, getting the (rusted and thoroughly baked) air injection manifolds off of the air injection nozzles can be not so easy, too.
FWIW, when I removed the air injector nozzles from my 2V 308 last year, they all unscrewed without issue. I tried doing this with the engine in situ after I removed the exhaust, but found it too difficult, so in the end I did it with the engine out (for other reasons), which of course really helped with getting a socket solidly on the injector hex. At the time my car showed a credible 39k miles, and the nozzles were not distorted in any way. They actually appeared very reusable.
You shouldn't have much difficulty getting the air injection nozzles out a 4-valve QV -- the nozzle end doesn't protrude as much and is rather well protected by the surrounding cylinder head material (and is not located directly below either exhaust valve): Image Unavailable, Please Login Versus this typical (damaged) 2-Valve air injection nozzle (that is): Image Unavailable, Please Login
I don't really know (but can't think that it would be easy to do with the US headers, and their insulation, in place) -- perhaps someone with more direct experience doing/trying that will comment.
I tried to remove mine ('77 GT4) but couldn't get an adequate purchase on them, lots of interference with the head and exhaust manifold and that's on the rear bank (the easy one). I later pulled the engine for a major reseal and they were easy to get to although I was worried that they would he seized in the head or the hex would strip. Fortunately they all came out easily and none had been damaged over the years of not being connected to anything.
