I just installed a boost gauge today, and took the car out for a spin. Seems I am only getting 5-6 lbs of boost tops. Does this make sense? What is wrong?? The car has about 87k miles on it and is stock except for a downpipe. Does this indicate a bad turbo? Bad catyletic convertor? Any help would be much appreciated! I'd like to at least be able to take full advantage of the cars stock abilities....

Thanks
Chuck

 

r u serious? I do know the cap that was on the plenum was hard as a rock... So it wouldn't suprise me. How common is this? I'd be curious to know a little more about this problem. And how are you so sure that's all it is with my car??

Thanks
Chuck

 

You can go here https://www.rx7club.com/forum/showth...threadid=98645 and here http://home.istar.ca/~dvandit/rx7stuff.shtml for boost problem troubleshooting. You can also send me a PM for any more help. My suggestion is, before anything else, do the hose job. It's like a rite of passage for FD owners. You can go here http://www.rx7turboturbo.com/robrobinette/hoses.htm for a how-to on the job. It's not that hard, just make sure to take your time, and be gentle. It's pretty pointless to try to track down a boost problem on a car full of brittle hoses. Plus, the hose job may solve the problem completely for you. Peace.
--Danny

 

Cool, thanks for the help...

Later
Chuck

 

Ok, I think you guys are probably right about the vacuum lines thing... I just went a looked at a bunch of them, and they are hard, brittle, and slide off easy. So I bet that's the problem. Now for replacement. Does somebody make a kit? I noticed you mentioned in that other thread the use of silicone hoses? Tell me what and where to get the parts, and how much hours to expect in a complete hose replacement....

Thanks
Chuck

 

I just had the same problem. Just bought my FD and installed a boost gauge this last week and am only getting a boost pattern of 5-2-4. I was thinking of doing the hose job, just need to find some time. I have 55k miles and the hoses seem NOT to be brittle at all. The thing that I didn't get was that why does my second turbo kick in if it needs 8 lbs of boost to kick on if I'm only getting 5. Could this narrow down where my leak, if that what it is, could be at. I'm putting an M2 downpipe on this weekend so any info into this and the boost problem would be greatly appreciated. Thanks.

 

You can get a hose kit from:

http://www.hosetechniques.com

 

nerx, that's interesting. Mine is kind of the opposite. It goes from about 3lbs under 4500 rpm, to 5-6 lbs after 4500. Does anybody have a comment on this?


Thanks
Chuck

 

Chuck, there is not much to say until you start going down the list checking things (like in the earlier posted link):

https://www.rx7club.com/forum/showth...threadid=98645

There are so many possibilities that you need to get under the hood and start narrowing things down or take it to a shop.

 

Ok, I've done a little testing and here's what I'm thinking. Want to get your opinions. I haven't checked for vacuum leaks yet, but plan to. Just haven't got around to it..... But I have a feeling that's not it. The reason is because of my boost pattern. From what I am gathering I should be getting the same or a little more boost under 4500 rpm that I am above 4500 rpm. That is not the case. I only get a few lbs of boost under 4500 and it takes some rpm to get even that... Then when the second turbo kicks in I've got 5 lbs. So I'm back to the catyletic convertor. Like I stated earlier, the car has 87k miles w/ the original cat. From what I've read, the rotory and turbos are pretty hard on catyletic convertors. Oil consumption, heat, etc. Add in the fact that I only get a very small amount of boost under 4500 rpm and it only seems to make sense to me that it's probably a cat going bad. Lower rpm, less air going through the motor, hard to get through the convertor in the first place, equals slow spooling. Makes sense, so I went ahead and ordered the midpipe off ebay. If it doesn't fix my problems we'll do the vacuum lines next... even if it does fix the problem I still plan to do all the lines. Just seems like a good idea. Especially since I can tell all of mine are pretty hard and brittle.

Just thought I'd share what I was thinking and see what you all have to say about it.

Thanks
Chuck

 

A couple of things to think about, be careful about running lean with a midpipe and no added fuel. And a boost leaks symptoms are either low boost across the board, or a little less on primary, because the two turbos combined can make enough to overcome the leak(if it isn't too big). Also, a clogged cat's symptoms are good primary, but less boost in the top end, because it restricts the high amount of exhaust flow that doesn't exsist at lower rpms. Not saying "You have this" or "You don't have that." Just mentioning my experiences.

 

Ok cool, thanks for the advice. I'll look into it a little more.

Thanks
Chuck

 

I'm gonna jump on the bandwagon here. Mine goes 5-6-5, and I have new vacuum lines, but I also have a constant whoosh-type sound as I'm building boost. Any thoughts?

 

I would say my boost pattern is 3-5-5. Give or take. It's kind of inconsistent. How old is your catyletic convertor (miles)? I have a feeling that might be what we're dealing with........ but I may be wrong.

Later
Chuck

 

Sounds to me like a clogged pre-cat based on boost patterns, but at the same time, it sounds more like you popped a pipe loose. YMMV, of course.

If you're hearing a loud whoosh as the revs increase (and theoretically boost increases), then perhaps you've popped a tube. I had the problem the other day - the primary charge air tube (name? it's the one that comes from the turbo assembly and goes to the IC on the intake air path) popped off - it was held in place somewhat by the strut tower brace, so I was getting around 5lbs of boost peak. The harder I pushed the car, the louder the underhood woosh got.

 

Finding boost issues takes a very systematic approach. I've had my FD for about 5 years now, and didn't fix it right until I figured out exactly what the sequential system was actually doing. Then you check the 6 solenoids, 5 actuators, two chambers, 5 valves and hoses that make up the system and the problem is usually fixed. It's not that big of a deal.

Personally, I think it makes the most sense to figure out what the problem is before doing the 'hose job'. But I do agree with P'cola, as the 'hose job' is never a bad idea. Another option that is rarely mentioned is getting the hose kit from Mazda. It's got all the stock hoses which are nice because they have the appropriate bends. When they are brad new and pliable, they too can be tied off.

You can spend a lot of time and money replacing parts that are ok without fixing the actual problem. These guys are giving you some good advice.

You most likely have a boost leak. A clogged pre-cat is a lot more common than a clogged cat. You have a downpipe, so I would head down the 'boost leak' and 'control issue' road first.

If you don't have a manual, you need one.

 

Chuck,

Nobody mentioned this, but why not take the cap off the intake manifold spigot and measure your idle vacuum? Other posts here say 17-19 inches Hg is about right on a healthy 3rd gen. If you are running lower than that (our '94 with 72 K miles is about 14 in. at 700 rpm, 15 in at 1000 rpm) you could have a vacuum leak. I'm about to replace all our lines with Viton after seeing the 240°F, 1000 hr. hot oil soak test done on OEM, Neoprene, Silicone, and Viton hoses on this website (Item 7 on the page offers a download of the report, including pics before and after the test):
http://www.geocities.com/MotorCity/G...technical.html

---- Bill

 

I got a sample of Viton tubing a couple of years ago (Grainger catalog???) and the wall thickness was too thin and collapsed.

You might want to get a sample before buying 30' of this stuff. I think it was like $4.00/ft.

 

wstrohm- According to the boost/vac gauge I'm getting 17-19 inches at idle. So if you consider that an accurate way of testing the vacuum lines then I would assume they're not leaking.

My theory behind this not being a boost leak is that under 4k rpm I am not getting the same amount of boost I am getting above 4500 rpm. It is much lower... If it were a boost leak then I would think technically the primary boost would be the same as the secondary boost. So that is why I'm leaning towards the cat. I may be wrong, but we were going to put a midpipe on it anyways. So it's not a big deal if that doesn't fix the problem... If it doesn't I'm going to start looking into it a lot more detailed. I just want to try the obvious stuff first.

Thanks
Chuck