gcthree

I know, I know, RX7's are tempermental- but I think I've had about enough at this point, and before I do something drastic, I thought I'd throw it open for input.

To set the stage, here's the work done on my car: street ported motor with 1,000 miles on it (compression check is OK). Supra fuel pump, 1,300cc injectors, Power FC, HKS downpipe, high flow cat (500 miles on it), Racing Beat cat-back, PFS stock mount IC, JDM Y-pipe, PFS intake, stock NGK plugs (the colder trailing plugs all around), stock turbos in great shape, and all else is stock equipment.

Jason plugged-in some mapping that accounts for the above modifications, and I know that the car needs to be tuned to extract the best power/drivability (unfortunately, there's no one close here in NYC to handle this except for KDR- but I'd rather not take it there....). Given all this information, the car, in my mind, should run reasonably strong. And it does....sometimes! I'll take it out and run it, and the boost comes on, and then a couple of minutes later, I'll dip in, and there's absolutely no boost! Zero. The car revs-up like a normally aspirated rotary!

I've checked all hoses and clamps, and ensured that there's no problem there. I bought one of the Ebay hard pipe intake kits (don't waste your $!, buy the real thing from Jason!), and only the upper pipe fits. The lower pipe isn't even close, so I still have the stock ribbed rubber elbow in place.

So, either I get this figured out, or one of the nicest condition (35,000 mile) 3rd gens is going to be up on the block. Thanks for the help in advance.....

Herblenny

iTrader: (13)

I am also having similar issue (crazy boost).. Do you know if your secondary is kicking in??

First check all your one way valves.. they are essential in building vacuume or pressure in the "rats Nest".. If one of them fails, your vac or pressure is doesn't build.. in turn most of your actuators that controls your turbos and etc are not functioning correctly..

I'm currently having problems with holding vacuume to control my secondary turbo actuator, that opens the little gate by the y-pipe.. My primary spools but the boost leaks to the secondary turbo.. then eventually the pressure from primary closes the flap.. but then I'm already up to 4K... so the secondary turbo kicks in..

Engberg

Yes, I think you should drive around and pay attention to rpm. You may be able to narrow it down to the secondary turbo only, the key is to take out as many variables. Do different runs from low rpm to red line, from 3k to redline, 4500 up, 5000 up etc just to get a feel for what is wrong and where.

gcthree

What is particulary odd is that it will establish a perfectly normal boost pattern on one run, and then, for example, if I'm part throttle in, say, 2nd gear- full throttle will provide no boost whatsoever.

However, I do need to make a few runs with an eye on boost and tach to establish exactly what is happening and when.

the_saint

How much are these one way check valves? part number?

I have the exact same problem.

1. Intermittent boost on primary turbo. i.e. WOT gives no boost sometimes, other times makes full boost.

2. Secondary turbo always make full boost.

3. When everything is working fine, the boost pattern is normal.

4. Free revving gives 4 psi of boost like it should.


thesaint

gcthree

Having replaced all the check valves when I did the vacuum hose job last year, I assume they're all OK. However, I did have the motor streetported recently. Is there a chance of a misplaced hose creating the same effect?

What puzzles me is the intermittent boost. If a check valve was not functioning, wouldn't it be a constant boost problem? As I mentioned, it's most noticeable with part throttle driving, and dumping full throttle from that position; most of the time it produces no boost. Let it all settle down, and then tip in full throttle, and you get boost.

Engberg

Sound like (remember I'm still a noob too) a vacuum leak.

inis

Fred (im going to call you fred because gcthree just isnt very personal for this advise and i dont know your real name). I have alot of experience with problems and these cars.

First-I want you to grab a lage tool such a cresent wrench, or side cutters. I want you to throw it as hard as you can against the side of your house you care the least about.

Second-I want you to get a lawn chair, and sit in front of your baby for at least a half an hour. Remember why you love the car so much. Then go to work on it because its worth it.

lol, sorry, i was feeling like a pointless post.

FYI: dont throw tools in areas with heavy brush or trees. I lost my best socket wrench and only 10mm (which you all know is like "the socket" for the RX-7). Didnt find it till the next summer when the lawn mover guy almost **** his pants from the gun shot.

gcthree

Remind me to not let you even come near my car, no less work on it......

rynberg

Please post more detail re: rpms/situations...

One thing to remember with the Power FC is that it likes to go into non-sequential mode and stay there.....for example, once you go above 4500 rpm and both turbos are active, until you drop below 3000 rpm, you are running non-sequential.

Let's say you are accelerating on the freeway -- you go over 4500 rpm in 4th and then shift into 5th but your revs don't drop below 3000 rpm (80 mph). Your car will be locked in non-sequential and will feel really slow and be slow to build boost. It will stay like this until you drop below 3000 rpm (I usually just push in the clutch until the revs drop enough). Is this what is happening to you?

gcthree

I do need to go back and document rpm's/throttle position/ boost.

However, your description is much what I'm dealing with, and I was not aware of the Power FC moving to that mode. With moderate throttle tip-in (likely 4,000rpms+), when I give full throttle, there's no boost. Now, I haven't run it all the way out to see if, ultimately, boost will build, but your explanation seems plausible. I'll post again after I've done a few runs.

Herblenny

iTrader: (13)

Very Interesting.. I have never knew that.. That might explain part of my problem.. Thanks!

the_saint

Any idea on the cost/part number of the one-way check valves. My parts department looks at me funny (for many reasons) with a ****-eyed look when I mention them.

thesaint

gcthree

I need to dig out my invoices. I replaced all of the check valves when I did the silicone vac hose job a couple of years ago. As I recall, they're not cheap, but it's not like you have much of a choice. I'll get back to you as soon as I go through my records.

As for the erractic boost issue, Rynberg read seems right. I just had my car out for a battery-charge run, and the no-boost situation occurs in the 4,000+ rpm/moderate throttle condition. Correct boost pattern is there from below the 4G mark. Thanks for the enlightenment- I feel much better.....

alberto_mg

Hey gcthree - I'm in Mineola if you want to take a ride in my car and compare.

Joe at smokinjoeracing.net in Elmont rebuilt my motor and tuned my car and I can't say enough good things about how the car runs. Touch base with him if you want a trustworthly local source.

Shoot me a pm if you want a ride

r1owner

Is there a way to test these "check" valves?

I was running my car down the strip this Tuesday, and something happened on the last run. The first turbo boosts just fine, but at 4.5K the second one doesn't come on line, and there is some wierd (hard to describe) noises coming from under the hood.

gcthree

Found the invoice. These prices date back to April 2001. There's two different check valves needed. Alltogether, if you're replacing all the valves, you'll need a total of 5 valves:

Part #: HE41-13-995 cost $21.68 - need 3 valves
Part #: N390-13-995A cost $20.24 - need 2 valves

I bought mine through The Gallery Group in Norwood, Mass. @ 1-800-339-5768.

As for determining if they work, you can hook a Mighty Vac up to it, and apply vacuum. It should hold vacuum on one end, and not the other. Alternatively, you could just use your mouth, but don't let anyone see you do it, because they could come to some unflattering conclusions....

Herblenny

iTrader: (13)

When you go simplified seq turbo.. you only need 2...

So, did everything work out??

gcthree

All's well in rotary land. Rynberg was on the $; above 4,000 rpm with light throttle, the PFC stays in a non-seq configuration, and creates a slow boost build situation. Drove the car around and it boosts fine coming from a low-rpm position; get it above 4g with tender throttle application, and then call for some boost, and there's nothing there. I'm satisfied. Thanks for the explanation and interest.

I also got around to putting a new set of NGK Iridium plugs in....I'll post that separately.