KyleH

Well, last weekend I finished the vaccum modification. While I was at it, I changed the spark plugs and wires as well. I still have the stock fuel system. In fact everything is still stock on the car aside from a cat back.

I took the car out for it's first drive yesterday. I found that at low RPM ( below 4500) if I roll into the boost, i hear the turbo(s) spool but the car feels like it is running n/a, all the way to redline. If i smash the gas above 4,500 it pulls very nicely. This is the case in all the gears. I understand the 2nd turbo comes online at this point, but that alone doesn't help me any.

Any ideas on what could be the problem?

EDIT: I should add the car idles pefectly, and seems to run great other than this issue. Also, it is of note that I broke the outlet to the airbox where the air pump would hook in. I don't think this should be much of an issue though.

Mahjik

iTrader: (1)

If your primary boost worked fine before the modification, then it's something you did. Re-check your work.

KyleH

Heh... well it took me a whole weekend to do this. Just wondering if anyone could point me in the right direction. I checked and re-checked the vaccum lines before I buttoned everything up. Like I sai,d it idles very well, but I have this issue... What reason could there be to cause this? If I can get that, then I'll at least know where to start on the vaccum lines.

Thanks!

Mahjik

iTrader: (1)

Start by looking at the Pre-Control the Charge Control components.

KyleH

I'll have a look at that, thank you.

KyleH

I put a boost gauge on it. If I go WOT around 4500rpm, it will give me 8-9psi. If I go wot before that it will stay at 1-2psi. I launched it once and in first gear it read around 6-7psi somewhat holding, in second it shot up to 8psi but the boost fell down real quick. Then, in third and forth it held 8-9psi the whole way. I have pulled the manifold and going over the hoses again.

KyleH

Okay, went over everything again. All hoses checked out.

I'm at a loss. The primary turbo is obviously not coming online in the lower RPMs. What is it that controls this initial stage? Or what multiple things happen to cause it to start spooling.

I will say that I replaced the hoses down on the boost control line and pre spool down at the bottom. I did not at the time know there were restrictors in there, and they are now in the trash somewhere. I however, can't believe that these would cause the issue I'm experiencing.

Any help would be greatly appreciated.

WaLieN

The turbo pre-control actuator mainly controls the primary boost. If it's stuck open, you won't get any (or possibly very little) primary boost. Take a look at the actuator and make sure the rod is connected to the gate.

http://www.autosportracetech.com/RX-7/rx7stuff.htm

Read through that.--^

KyleH

Thank you, I will have a look.

I suppose it is worth mentioning that before I did this mod the boost was falling off at the top end. It would come on strong (normal) down in the lower RPMs. After the mod, the low rpms are totally dead, but it does pull strong to redline if and when it actually does boost.

wstrohm

"I will say that I replaced the hoses down on the boost control line and pre spool down at the bottom. I did not at the time know there were restrictors in there, and they are now in the trash somewhere. I however, can't believe that these would cause the issue I'm experiencing."

Believe it.

KyleH

To the point, but I wish I could say insightful. Please explain if you would.

KyleH

Still haven't gotten this issue under control. I added a boost controller to the wastegate control, and shut it all the way (turned boost up as high as it would go) and hooked an in line reducer into the pre-spool control. I also closed this all the way off in hopes of gaining boost.

Nothing. Notta.

I hear the turbo spooling, but get none of it. I feel it's probably heading out the wastegate.

Heeelllllp!

POS7

Your boost is falling off at the top probably because you still have the stock precat and cat. They're probably somewhat clogged.

Also, your boost is limited if you dont have the pills in. Those two lines are marked with white dots I believe. How are your checkvalves?

In all honesty, you shouldn't have done the vac hose upgrade if your car was boosting fine before 10-8-10-8 (the last 8 is a result of clogged precat.) I haven't even done mine yet primarily because I haven't had problems with my system. A lot of people do the vac hose job and screw something up (like breaking a solenoid or switching vac hoses) which makes your car worse off.

KyleH

I didn't have a boost gauge before the vaccum mod. But the car was having issues holding boost when running through the gears.

I stated earlier those lines are now gone, the restrictors (pills) are gone as well, and in their place were regular vaccum lines. I still could get no boost (which I should have gotten SOME) and so I put in a boost controller and flow reducer in the pre spool line... still with no results.

quicksilver_rx7

Something doesn't sound right. In the 1st post, you stated that

dgeesaman

iTrader: (7)

There is a path of dependencies you can trace and troubleshoot. Let's start with the vacuum and pressure chambers. If you can get a Mityvac, by all means do so. It will save you hours and probably save money so by testing all of your solenoids and re-using the good ones. An OK version can be borrowed from Autozone, but the best is to invest in a Mityvac Silverline Plus kit (find it on the web for about $60, about the price of a single new solenoid).

First, you need vacuum in the vacuum tank to feed some of the solenoids and actuators. Leaky check valves, broken/popped hoses, or a cracked vac tank are possible failures. With a Mityvac, tee into a line or just past a check valve leading to the vac tank, and apply 20"Hg vac and see if it holds. Without the Mityvac, tee your boost gauge into similar place, start the engine, and verify that it loads up with about 20inHg and holds it after you shut off the engine.

Second, do the same for the pressure tank. With a Mityvac, pump it up to 10psi and see if it holds pressure.

That's the first set of things to verify.

Dave

quicksilver_rx7

Let me try to finish this one now. You stated that you get no primary boost but you get secondary boost depending on the specific conditions that you mentioned in post #1. You could possibly have a problem with the Turbo Control 1 solenoid (located on top of ACV) This controls the exhaust flow to the second turbo. It is possible that this solenoid is open and all of the boost pressure is flowing to the second turbo. Thus, you hear the turbos spooling, but don't "feel" it until the exhaust pulse is strong enough to spool both turbos.

Disclaimer: If this has been covered already, then it's obvious that I didn't read the whole thread. I'm also not an expert on the turbo control system.

Joe

KyleH

I was doing some reading about the charge control solenoid/actuator/valve.

It says to test it, start the engine and let it idle, the actuator rod should be pulled in. Shut off the car and take off the hose and the rod will be out. Basically, the actuator is a 2 piece mechanism with some sort of diaphram that can recognize pressure differences on each side (chamber A and B). When the pressure is less (vaccum) on chamber A, the valve will be "sucked" toward chamber A, and be in the "in" position. This should happen all the way until 4,500 RPM. When the valve is sealed, ("in") it closes the air passage way b/w the 2 turbos.

The point is, I did the test and it failed. The rod stayed out all the time except when i shut the car off (it would go in and pop right back out when the ignition was shut off).

So if someone can help me understand why there's no vacuum from the vacuum chamber, this would give me a start. You would think I could daisy chaine directly off the line running from the vaccum chamber (which has multiple Ts in it) directly to chamber A, that I would be fine. While in fact the way it happens is that there is no vacuum at all..... Any ideas?

dgeesaman

iTrader: (7)

Possibilities:
1) Bad check valve. Also make sure all the arrows on the valves point toward the UIM.
2) Popped off hose. Look at the vac. diagram and study any hose in coming off the vacuum tank. (inspect all the others, too)
3) Misrouted hoses causing a leak.
4) Bad solenoid.

If you don't find 1 or 2, I suggest ordering that Mityvac and spend some time testing the parts.

Dave

wrankin

except for the one that leads to the pressure tank, which should point *away* from the UIM (or rather away from the Y-pipe).

-bill

KyleH

Well, I made some progress for what it's worth. Now when idling, the rod is still in the "out" position. However, when I shut the car off, it goes back to the "in" position and stays here.

Does the car have to warm up before this mechanism works propery? Because when I "idled" it, the car was idling on it's first cold startup of the day (been 12+ hrs since started).

I'm making progres.. I think.

Does it matter when I'm testing that I have the airbox off?

What I changed was I put a different "check valve" in, and also there are 3 T's off the vacuum chamber. When I first did the mod, I didn't really pay attention to where each device was T'd off. This time I went back and made sure that the solenoids were T'd off in order as they are shown on the diagram... although I can't really see how this could matter.. .

Any idea as to why the rod isn't in the "in" positiong while idling, yet it goes to the "in" postiion and stays when I shut the car off?

KyleH

I found that I have vacuum going to the charge control solenoid. From here the vacuum is supposed to go to the nipple on the intake and then over to the charge control actuator. However, as state earlier, this is only happening (IE, the rod is only moving inside the chamber) when i shut off the car. I tested the solenoid with a 12V source, and if you put vacuum into the solenoid, it will only allow it to pass through when the 12 V source is OFF. So when there's a 12V source hooked to the solenoid, the air passage is blocked, meaning no vacuum exits this solenoid until I turn off the car, which then causes the rod to be sucked "in."

So my new question is what is going wrong here? The test says that below 4500 rpm the rod should be in. This is only possible if there's vacuum on that side of the chamber, which there isn't b/c when there's a power source to this solenoid, it locks out the vacuum that goes to the charge control actuator. So then the question is, when is this solenoid supposed to get power? Are they powered at all times when they key is "on" or are they all controlled independently? If so, what has to happen to allow this one to open the gate to allow vacuum to the charge control actuator?

KyleH

So i went out, just for giggles, and T'd right onto the vaccum chamber straight to the solenoid. As expected, at idle the valve was closed. So I went for a drive. Sure enough, for the first time in weeks i started getting power on the low end. I was getting A LOT of power too... no intake + strom just blew through + boost controller set to max. I however got out of it by 3 grand so as not to blow anything up...

Anyway, now the issue is this.

- Can someone confirm that the white plug is the one that plugs onto the charge control solenoid, and that

-All solenoids that have the same part number are the same? I know I broke one or two when removing the hoses, and I know one of them was an important one. Since they had the same part number I just swapped out a good one for the broken one.

I did get a mighty vac and tested the solenoids... they're working fine. I also did a 12V test, and the relay's are working.

If all of the above are true... why is the charge control solenoid not letting vacuum through at low RPM?

KyleH

No replys... this is discouraging.

In the reduced vacuum line drawing, can someone tell me where the orange hose that runs from the nipple located above the turbo's (right beside the outlet for the pipe that runs to the I/C) goes for certain? In the drawing, it is chopped off and never says where it runs to.

dgeesaman

iTrader: (7)

The orange hose looks like it should go into the top of the 4 pass-thru fittings of the LIM. On the other side of the pass-thru it feeds into the pressure chamber.