993RUF

Great writeup Mike, very educational. Thanks

Mike J

Maybe I can decribe the path from where the air feed pipe joins the cam tower. The air will take a quick 90 degree turn right at the base of the threaded inlet in the cam tower and run in a cast tube inside the cam tower. Almost immediately there will be an outlet to the first head. The second head is half way down the tube and the third is at the end (of course). The tube in the head looks larger than the tubes that run to each head. See the 8th picture I posted which is the rear-most piston. That show shows the air inlet to the upper right. If you can make out the little ball bearing that is the access hole to clean the tube that runs across the cam tower to feed each head.

In other words your wire would have to turn a quick 90 degrees and then turn to the head side about 30 degrees to enter the tube to the head. Once in the tube heading down to the valve chamber it would have to do another 10 degree turn at the interface between the cam towers and the heads and then a straight shot down to the heads.

Most of my carbon was in the cam tower tube from the head interface to the main feed pipe on the upper side of the cam tower. not the heads..which is wierd. I don't have it in the records but I am suspecting that the PO might have had the ports cleaned. The air tube from the valve chamber to the top of the head was not bad and my SAI check valve was operational. This is after 75,000 miles. However there was much more carbon in the cam towers which indicates that either my engine was cleaned before or the carbon tends to gather at the hardest location to clean.

I hope that kindof answers your question...

Cheers,

Mike

tam993

Yes, it does Mike thanks. your thread is great. Explains the design well. My car has 75K on it too.
Not a lot of crap on the exhaust valves though. But the check valve was completely trash. I've got 5 of the 6 ports open really well just by flushing. The only way do to properly do things is the way you've done it.
I'm going to try and get that last one open from the feed pipe if possible. You're right the build up was not in the cylinder head part....

For those that want to know,
I'm not sure what this chemtool b-12 stuff does to the carbon build up but evidently over time.. like a week or so of soaking it kind of breaks it up with air pressure I guess. The carbon blows out like granulated junk, like sand kind of. I don't think it dissolves anything.

epj993

Tam993, you're correct. The cleaner doesn't fully dissolve the deposits, but does enough to loosen them. The air pressure gives it the push to clear it out.

I had a similar problem with one last port not wanting to flush. I was getting blow through from a clear cylinder with both valves open back up through the VarioRam. I turned the crank to close (or nearly close) those valves which allowed enough pressure to build up to finally break it free. Once all were free, I did one more soak & flush to make sure the ports were flowing freely.

Once you get them clear, include the check valve in your periodic maintance every 10-15k miles. With the valve working properly, there's good evidence that the build up will be kept to a minimum.

Good luck - you're almost there!

Mike J

Another observation point...when you pressurize the system you are putting a large amount of pressure on the seal between the heads and cam towers...which is not usually pressurized at all, it just holds the oil from leaking. I am not sure if its designed for 125psi of air pressure and not that I have seen it I would hesitate to put that much pressure there. Then again several people on this list have done that with no problems so mabye its ok...

Cheers,

Mike

Toga

Thanks for a great write up Mike. I learnt a lot here...and I'm happy not to have that system on my car

epj993

Good point, Mike. I wonder what pressure is generated by the electric SAI pump? It would have to be enough to overcome the exhaust pressue and enough the force through those small passages. Probably not 125psi, but I would think it's more than a few psi. Just speculating...

tam993

I'll let you know if anything was damaged by 100 psi. I suspect nothing, or you'd be blowing cleaning fluid out from somehwere. Plus I don't thing the oil at that point is under pressure is it? After it leaves the cam it's gravity drained, right? or am I missing something?

Reynard38

Soaked my SAI valve with PB blaster the other day as it was VERY tight. While I had the airbox out I noticed that the snorkle tube connects to the airbox just opposite the hose for the SAI air. This always seems to be where the air filter gets the dirtiest.
Question? Could the SAI system be pulling in soot and oil from the crankcase ventilation snorkle. That carbon has got to be coming from one, or both ends of the system.
Until be can fix the problem it will be recurring.

Dan V

If that were the case then I would expect to see a lot of that soot in the top part of the SAI check valve when you remove it.

dutchcrunch

I think Reynard is right on the money. the reason you do not see the the carbon deposits on the sai check valve is because it does not get hot enough. the sai valve is in the engine compartment which is the coolest part of the motor. once the contaminated air containing oil vapors passes thru the passages along with time and heat it starts to build layers upon layers till eventually the passages are cloges. bet you if you were to take the supply air for that system from a cleaner air source you could get rid of this problem. its all a money making scam and i am sure they know how to fix it . nobody want s to say so they can keep milking everybody wallet.

dutchcrunch

after reading more into it it look like a design flaw . air injection should have been put futher down stream past the exhaust valve.

tam993

Yeah, may be I'm wrong but, if you wanted air in the exhaust just pump it there instead of some wet dream of some engineer....
what a joke.

Tom Pepper

Just doing the engine project is daunting enough. That Mike is also thoroughly documenting the process with photos and a running narrative while answering myriad questions from appreciative Rennlisters is mind-boggling.

John D.--I think it would be appropriate to give an occasional award or recognition for DIY information above and beyond the call of duty. Perhaps called the " Robin Sun DIY Award"


I hereby nominate Mike J.

epj993

I second that!