Fred Sickert

I'm trying to fix my low transition boost. I've got a 10-6-10 pattern with the PFS on 10. I've attached my boost gauge at the back of the Y pipe to measure pre spool. I'm only getting to about 5 psi (at 4500) on the pre-spool with my HD valve all the way open. I've even removed the valve and disconnected the pc solenoid (This cuts the primary down to 7psi). I'm still only getting about 7 psi of pre-spool. What could be causing this ? I should get a big spike, right ?

Flybye

Turbo Precontrol valve is the one you need to adjust. Assuming everything else is working properly......

This is how I eliminated my dip at 4500rpms. Just gotta open it up to allow more exdhaust to get to the 2nd turbo before transition.

adam c

iTrader: (2)

The HD controllers don't work very well on the prespool. It can be nearly impossible to get them working properly together. I believe the extra length of the hose causes the problem.

I had a prespool controller on my car and tried (for a month) to get it working right. Eventually, I gave up and reinstalled the stock hose (with the pills). My boost pattern went back to 12-8-12. I think the ECU tries to keep prespool at a stock level of around 8, regardless of where the primary spools.

dubulup

Hallman RX-Pro

cruiser

Have same issue as adam. Cant get to 12-10-12 pattern... and am stuck with 12-8-12. There is quite some powerloss at transition because of it (by the feel of the seat of the pants).

Flybye

I MANUALLY adjusted the flap.
The rod end of the actuator has threads where it connects to the flap which allows you to adjust its position.

adam c

iTrader: (2)

If you would provide a detailed explanation for this procedure, that would be very helpful.

Thanks, Adam

reza

I found that the prespool HD valve, needs to close as much as only 1/2 turn. This will give more flow to the secondary prespool. If you close it, you will get spike.

cruiser

Flybye.... please elaborate
More explanation would be highly appreciated.

Flybye

https://www.rx7club.com/showthread.p...ool+adjustment

This thread should help.

When I get home, I'll post a diagram of the flap system so that you can easily visualize it.

Fred Sickert

Well, I just wired the precontrol open and the charge control closed. Still only 7 psi on the secondary before transition. Could the precontrol be clogged ? Anyone know how much secondary boost should be generated by a fully open precontrol ?

Aristo

iTrader: (8)

Just curious Fred...have you had your turbos rebuilt?

Fred Sickert

Yes, I have. Turbo City.

Flybye

Ok quick summary of what does what here....

As per the factory ECU, the Prespooler acts as a mini wastegate for the primary turbo. Wastegate stays closed and the prespooler pretty much regulates primary boost. As you can see, the more the prespool rod pushes out, the more it opens the flap to allow exhaust to get to the 2nd turbo.

During prespool, the charge relief valve vents any boost from the 2nd turbo before 4500 rpms. At 4500rpms, the prespooler opens up all the way. Also the Turbo control actuator is still closed not allowing any exhaust to get to the 2nd turbo.

Now here's where it gets tricky....

The charge control actuator relies on boost from both sides of the charge control valve in order to open. The Charge control solenoid is what allows this extra pressure to reach the other side of the actuator. Once that little sucker sees boost pressure almost the same on both sides of the charge control valve, it opens the valve.

The turbo control actuator is the big bitch that causes the most headaches. That **** needs vaccum AND boost to operate properly. Which is why we have a vacuum and pressure tank. The solenoids regulate how much of all this gets sent to the actuator.

Now do you understand what you are doing? Wiring the charge control closed you are basically putting a wall infront of the 2nd turbo. Wiring the precontrol open still might not be enough to open the flap ALL the way since you still may be able to adjust the flap at the rod by turning it out a bit so that the door opens up more. Look at the diagram and make sure you didn't accidentally wire the prespool flap closed

I haven't been down there in a while, but I think the Turbo control can also be adjusted.

Yes, our exhaust manifold is an extreme bottleneck

Flybye

I forgot to mention that it doesnt. The stock ECU blindedly opens and closes stuff without even knowing what boost is coming out. This is why people get mad spikes during transition on modded cars. ECU doesn't know that you have a free flowing exhaust and instantly gives you headaches.

It takes a while to adjust the flaps to a point where you will be happy. Adjust.....run....adjust....run.........adjust.... ext.

You have to adjust it so that you get minimal drop at 4500rpm and still get max boost on the primary meaning getting full boost (12psi) by around 3000rpm. My 4500rpm drop is hardly 1/2 a pound. I mean it happens so fast you almost don't even see the needle move

gdnimr0d

iTrader: (4)

NON sequential is the only way to go man it owns!!!!

Fred Sickert

Well, my CRV closes at 3500. Others have observed this as well. This makes sense, because you wouldn't see any boost pressure at the back of the Y pipe if the CRV was open. I popped the PS actuator rod off, so I know I had the prespool all the way open. Also the rod is actually set up a little long (supposed to overlap, then you pull it to attach). I'm looking at pre transition boost, so I wired the charge control just to make sure it wasn't opening prematurely. I also read in the thread you posted that with the rod too long (too much ps) you should only see 5 psi on the primary. So I think maybe I need to take my precontrol gate apart. Turbo control seems good to me. The spool up from 6 to 10 is pretty fast.

t-von

iTrader: (8)

I use to have this same problem as well until I installed my Home depot Style manuel boost controller. I used 2 valves, one to control boost and one to control precontrol. My new pattern is 10-9-11.

Flybye

Before you start taking things apart, remember there is still a solenoid for the charge relief, charge control, and prespool control.

A line causing a leak or even a bad solenoid could still be the problem. The precontrol flap doesnt simply clog up. At least I've never seen one clogged up

For example, a bad hose with a leak between the precontrol valve and the precontrol actuator would cause not enough boost to get to that actuator causing it not to open up enough or at all. Same thing with the charge control. The flap may be opening up TOO slowly or may be sticking.

Non seq is for the sissys
Besides, I've known several guys who went non seq and they regreted it. One of them ended up going to a small single and the other went back to sequential

The Home Depot valves sometimes work. They didn't work for me. Besides, you do this right and it will be one less valve in the engine compartment. They won't work at all if you have something wrong with the control system.

Flybye

Fred Sickert

I'm hooked on the low end/part throttle response of sequential. I wired the pc and cc and blocked the crv. So the solenoids weren't an issue. This gave me the situation for max prespool: cc closed, crv closed, ps all the way open. (I also tried it with the crv normal - open till 3500). I am going to try lengthening the tca rod to see if that helps. I suspect, though that the key to a good transition is seeing 8 (or 10) psi at the back of the Y pipe, then quickly spooling to 10 (or 12) after the transition. Anyone with a spike or even transition know what they get at 4400 on that line ?

rpm_pwr

Same here, just as it says in the Yamaguchi book. My CRV closes about 3500, then from the 3500 to 4500 you can hear the secondary go ballistic and the boost gauge barely moves at transition.

-pete

$150FC

this is a very informative thread about how the sequential system works. thanks guys.

Flybye

Opening everything up, inlcuding TC actuator, and you are basically running nonseq. You shouldn't even see or notice anything during transition.

Keeping the charge control valve open, you shouldn't feel anything either. The reason we all get a dip or spike at 4500 rpm is because when that little valve open, if the 2nd turbo is creating more boost than the 1st, that will cause the spike. If it has less boost than the 1st, that is what causes the dip.

Fred Sickert

I've got the non-seq switch. I get full boost by about 4500. I've been thinking about the charge control. It's supposed to open when secondary boost is more than primary (Either side of the diaphram). But there is also spring pressure pushing it open, so it wants to open, even if the secondary is lower. With pc all the way on the transition is 7-7-8. Its hard to tell exactly where the drop to 6 is, I guess I need datalogging to really tell. I'm going to try a much shorter line on the pc and see if that makes a difference.