Losing boost
 

Hello everyone,

I have a 1994 Mazda RX-7 w/ only 66k miles. I'm losing boost and I'm only getting approximately .4 lbs of boost whereas I used to get around .75 to .9 lbs. I know there is some sort of leak somewhere because I can hear the air leak when I'm on the gas. Has anyone experienced this and can tell me how to fix it? These are my current mods: HKS downpipe, GReddy catback exhaust and stock mount inter-cooler. Thanks.

Get out there and get your hands dirty.....the first places to check would be the couplers in the intercooler piping and the BOV hose at the y-pipe. You'll have to actually remove the couplers and stretch them to check for splits.

Agreed, and the first one to check is the Y-pipe/crossover tube coupler, which is often the first to go. It's located under the plastic tube that "crosses over" the engine from the turbos to the IC. You'll need a good set of channel-lock pliers to remove the stock spring clamps and gain access to it.

Thanks for the tips guys. Do you think it has something to do w/ my stock BOV? I read somewhere that it could not be closing properly so it's leaking boost? I can really hear a loud air leak when I'm on the throttle and then hear the stock BOV when I release the throttle. My boost will not go above .4 lbs right now even through out my rpm. It doesn't seem like my second turbo is kicking in. I used to get 11-9-11 in 3rd now it won't even hit .4 lbs. Will a small leak in the IC couplers really make a huge difference like that? Thanks again for the help.

I doubt it's the BOV, the stockers dont typically go bad. I pushed 17-19 psi through them for years with my BNR turbos with no problems. Most likely it's a boost leak from a coupler or hose, as rynberg and kento mentioned.

Don't forget the throttle body gaskets/o-rings. Mine were basically demolished and I was losing 3-4 lbs of boost.

Yes, even a "small leak" will make a "huge difference", because once the stock rubber IC couplers start to crack and develop a tear, the pressure only rips it open even more, and it quickly goes downhill from there; the secondary turbo won't be able to do anything. It doesn't take much for literally all the pressure leak out. As Rich said, it's definitely not your stock BOV, especially if you can hear it when you release the throttle.

Thanks again for all the help guys. I love this site.

I hope it's the coupler right next to the y-pipe. I'm going to work on it today. I also noticed there was a lot of dirty oil residue around the area between the y-pipe and coupler so there is some definite leak somewhere.

My idle is currently at 300-350 mm Hg. Is this normal? Thanks.

It's low, but the reason why is because you have an intake vacuum leak, i.e., the broken rubber coupler.