Plugging exhaust air injection passage
 

Can anyone tell me how important it is to plug the air injection passages in the rotor housings when removing the ACV? I imagine that, without air being injected, that exhaust gas would work its way back up those passages. I don't know how big of a concern that should be.

Thanks
Shane

thats what the block off plate is for

mike

The block off plate will not keep exhaust gas from coming up to the intake area both heating the intake and causing turbulence in the exhaust port.

Racing Beat plugs them.

If enough people just disregard this and get along fine, I will too. I don't care about getting 1 more HP or anything. I do care if there have been measurements taken that show an increase of 5 degrees on intake charge or something. In the stock configuration, these passages are under pressure, eliminating the issue.

Actually, I guess at WOT, the air pump shuts off anyway... I just thought I'd ask anyway. If I don't get any other replies, I'll just leave them open :).

When I was putting together the Quasi-Evil Engine ('83 12A) I bought some 5/16" steel dowel rod, which fit in the 8mm air passages in the exhaust ports. To keep them tight, and sealed, I chewed the rod up with the serrated faces on a vise, cut 1" or so lengths off, coated them with muffler mud (that high-temp putty that allegedly seals exhaust leaks) and used a hammer and punch to put them in place.

I wasn't worried about exhaust turbulence very much - at the high pressures and vlocities seen in the exhaust system, the flow is rather much like water streaming from a fire hose. I was mainly concerned with blocking off the passages so I wouldn't require spending money on an ACV blockoff plate. :)

I don't know which engine you're doing, but on mine there were some passages from the ACV area that are in communication with the manifold runners. JB Weld fixed that.

The reason why racing beat sells the plugs are for us guys who go so big on exhaust porting that we have to remove the sleeves, and in order to remove the sleeves you have to take out the screw in nozzels that are there stock. once you take those out then there is just big hole that go down into your oil sump. So you have to either buy those or i made my own out of AL rod. If you use anything other than AL to plug those you run i high risk of the metals not expanding at the same rate and then you will crack your housings and thats a bad thing.

CJG

the racing beat block off things are for the early engines that actually had screw in nozzles. it would be best to weld up the hole, but its not super improtant

mike

I don't think we are talking about the same thing. RB specifically talks about heating the intake manifold. The exhaust sleeve thing, I saw them discuss seperately, but it doesn't affect me.

My application is a 13B-REW, single turbo, track only application. I was mainly concerned about the heating of the intake charge and the loss of the all-important expansion energy of the exhaust gasses pre-turbine.

Thanks for all the replies. It sounds like it's really not a very big deal. I figured it couldn't be with all the people I've heard of removing their ACV with no mentions of plugging these passages but I figured I'd better ask rather than act on assumption.

shane
plugged mine..figured it this way....without actual definitive measurements in either case...and most speculations has a tendency to lean negatively towards leaving it open....and most of the tuners have blocked it off....
im still maintaining sequential...hence...outside of emmision solenoids....most still exists under my UIM....so an increase in temp in that area is NG for my application...
if your hesitating due to cost....its easy enough to get aluminum stock at the local HD and manufacture the plates yourself....i did

I'm afraid that you are talking about something completely different than what I'm talking about - see the beginning of the thread.

apologies...my reference was with the secondary air injection that provides air for the maincat...for some reason my thoughts were on the passage left open upon removal of the secondary air piping....