JyRO

iTrader: (3)

Guys,

I have fabricated 3 restrictor plates. One with a 2.5" hole, a 2.25" hole, and a 2.0" hole.

Last night I put the 2.5" restrictor plate in and took it for a drive (without the tailpipe/muffler). It was loud, but I took it easy in the neighborhood and let it warm up. I tested it out on empty country roads outside the neighborhood.

The spike is gone! But I am still getting creep. I saw it making its way toward 13 p.s.i. so I backed out of it. That's the highest I saw, and it didn't spike up there, it creeped. For those who haven't read anything from me before, I bought the car crashed, halfway fixed up, but with no boost. I fixed the boost leak, but then it would spike to 17 p.s.i. and hit fuel cut. I have since been working on resolving the overboost.

So tonight I'm going to put in the 2.25" plate and try again. I figure if I can get it to stay at 10 psi, or even creep up toward 11 psi, putting the muffler back on should put it about where I want it.

BTW, when I had it up on the jack stands, I adjusted the front end alignment. With the steering wheel straight up before, the RF looked aimed straight down the road, but the LF was toed WAY in. I adjusted toe on the LF only. During my test drive last night the steering wheel is now dead nuts straight up with the car going straight down the road. Granted, its not scientifically straight, but MUCH improved. I will have a full 4 wheel alignment done, set to Pettit spec's before I autocross the car.

Sorry for the long post, but I don't get on here very often.

P.S. - I could fabricate a set of these plates for others who don't have their main cat and have boost creep / spiking problems, for a reasonable cost.


- JyRO

1wide7

iTrader: (1)

i just bought an exhaust silencer that slides into the tailpipe and no more creep

Force13B

iTrader: (19)

Good luck with all that sounds like your headed in the right direction.

trini

iTrader: (2)

you will get creep also if its cold out. might b ok with the 2.5 restrictor and the exhaust back on. but make sure

JyRO

iTrader: (3)

1wide7 - I thought about what you're saying. I don't know the system you have, but there was a super-trapp exhaust for motorcycles, it could tune your back pressure with various discs. I image they made super trapp exhaust for cars too. Its a good idea.

However, the plates I'm making are much smaller, lighter, simpler, won't go bad like cat, and cost way less than a cat or the exhaust system like you have. In essence they are providing me the backpressure that were available with the cat. I can switch plates until I get it where I want it.

Trini - I thought about trying it with just putting the tailpipe/muffler back on. But since I'm able to creep up to 13 p.s.i., my opinion was that I don't think the muffler (from Pettit) will resist flow THAT much. Not enough to hold it to 10. I'm going to put on the 2.25" tonight and see what happens. Might have to have a 2.375" plate made if the 2.25" easily holds it to 10 p.s.i. If the 2.25" hold it down good tonight, I will be concerned that I may be making too MUCH back pressure.

Thanks for the good words guys!

- JyRO

trini

iTrader: (2)

ohh sorry i thought you were trying to keep it at 12psi my mistake.
yea the 2.25 might work better.

try this if you have not done do already. take out the boost pill from the wastegate line .... this way it will open the wastegate earlyer. around 7 and den it will creep to bout 10

JyRO

iTrader: (3)

Guys -

This car is riddled with problems. But I'll get them all figured out. As soon as I'm done posting, I'm going back to the stickies to try to figure out what's going on. Here's what happened last night.

I put the 2.25" restrictor in and drove it. The first time getting on it (not quite full throttle) it did the 10-8-10 thing. I was pumped! I tried it a few more times mashing full throttle in 2nd. This is what I think was happening.

The boost would quickly go to 13 psi, I would back out of it and ease back on it again. When I eased back on it, I would be above 5,000 rpm, and I could full throttle it and it would stay at 10 psi. Meaning the 2nd time I eased into it, both turbos should have been puffing.

If I just rugged it from 3,000 rpm, it seems like the primary turbo would hit 13 psi, but once the secondary turbo came on it would dip pressure and hold at 10 psi.

My guess is that I have enough restriction, but that my wastegate is not opening quick enough to prevent the primary turbo from overboosting. Does this sound logical? And any words of advice and I'm all ears.

Plus, its back to the stickies for me. Previously in the stickies I was looking for answers to slightly different questions. I bet the answer I'm looking for is there, so I will read deeply.


Also, I eased it home through my neighborhood and when I got it home I noticed the temp was way up. I took it back to the neighborhood roads to blow air across the radiator, and turned the inside fan and heat full blast to blow off heat. That brought the temp back down. Doing this I realized that the radiator fans were not coming on at all. So I've got to figure that out. As it stands, the next fix is the fans, and to figure out what I can do about the primary turbo overboosting.

Any advice is appreciated. Meanwhile, I'm hanging out reading the stickies.

- JyRO

JyRO

iTrader: (3)

OK, I think I've read what I need to know. Pills!

If I increase the pill diameter from the primary turbo to the wastegate actuator, that should increase the wastegate actuator's reaction time. Is this correct?

What I don't know is if there is a pill there from the factory. I'm assuming there's not. If there's no pill there now, there's no pill to increase a diameter. Back to the stickies to find out if there's a pill there.

- JyRO

Force13B

iTrader: (19)

I don't know if this pictuer will help you but it sure helped me.
http://www.davidgeesaman.com/rx7/93v...lor.edited.jpg
I'm haveing an over boost problem right now as well. It's pissing me off.

JyRO

iTrader: (3)

Appreciated, although I have it already!

- JyRO

dgeesaman

iTrader: (7)

The 13psi is probably boost spikes. The stock system works well at the stock airflow but with just a few mods it is now working outside of its 'sweet spot'. The result is boost spikes when it can't adjust fast enough, or boost creep if the wastegate is simply overwhelmed. Even if you increase the size of the pill orifices (which is what lowers the maximum boost - a common issue when adding a few flow mods), it will not affect the spiking problem.

The best solution IMO is either a ball-spring manual boost controller or an electronic boost controller. No more wastegate/precontrol solenoids, no more pills.

Dave

JyRO

iTrader: (3)

Hey Dave - Thanks. You've been a great help from the beginning. Since I'm still totally green on this, answer the below for me.

If increasing the size of the pill orifice lowers the maximum boost, wouldn't the spike be lowered as well?

As I read it (my comprehension is slow), using a pill with a larger orifice would allow more air FASTER to the actuator. I figured that with the right size pill, the spiking would equal maximum boost. But even if it is exactly like you say, lowers the maximum boost, that would still work well as long as the spike is equal to the maximum boost. But then again, I guess it wouldn't be categorized as a spike at that point. Sorry to ask such dumb questions.

For my clarification:

1) Do FD's come from the factor with pills in the lines from primary turbo to wastegate actuator?
2) Would lowering the maximum boost (by changing pills) lower the spike?

Thanks again.

- JyRO

BMike

I'd try putting the exhaust back on with the 2.5" restrictor, I think you'll find the problems your left with will go away. I assume you haven't done any wastegate porting? Thats the most ideal solution to your problem really.

Force13B

iTrader: (19)

This helps me out. I need to trace my wastegate line and see whats up. On my drive home yesterday i was bosting 1bar (14psi). Thanks for the info Dave.

JyRO

iTrader: (3)

I dunno Mike - I don't think the Pettit straight through muffler is going to do much about a 13 psi spike from the primary turbo. The WG has not been ported (to my knowledge). From what I have been told about the car, the turbos are totally stock. Porting would help the creep, but I haven't yet learned what it would do about the spike. All I know is the WG actuator would still need to react quickly, not sure if porting would help much there. And my restrictor plate was a lot simpler than porting the WG. I'm saying that my creep is cured. Once I get the spike cured, I will tune with the plates more.

- JyRO

BMike

I think the exhaust still being a small pipe will slow down the exhaust from hitting a smooth and efficient flow a little longer which should reduce the chances of a spike occuring, I'm by no means a fluid dynamics expert, but I did do engineering for fire protection piping systems for quite a while. But obviously the advice may not be worth any more than you paid for it, lol.

JyRO

iTrader: (3)

Mike - I'm no fluid dynamics expert either. But from my engineering classes, I remember that pipe length had more influence on head loss then bend in the pipe. So you may be on to something.

I'm onto another idea, kind of like a infinitly adjustable pill. I'll see where that goes. When I get this spike taken care of, I'll go back and try the 2.5" with the tailpipe and see if the creep is still controlled. Thanks.

- Jason

dgeesaman

iTrader: (7)

The size of the orifice controls the amount of air flowing into the actuator, yes. The solenoid controls the amount of time the exit path is open, which then determines the air pressure in the actuator.

1) Yes, they come with a pill in the pc and wg lines. On some later turbos, there is no pill, but the restriction is built into the nipple on the turbo.

2) Depends on the spike. One kind of spike is caused by the secondary being prespooled too much, so that there is a spike because the precontrol was venting too much air into the secondary. A smaller pill in the pc line will help this, or installing a different boost controller on the precontrol line. The other kind of spike happens when you mash the throttle, especially when the turbos are already in parallel mode (e.g. 4500+ rpm, or 3500+rpm immediately after having been above 4500) - this kind of spike I don't know much about, except I *think* it's caused by lag in the stock boost control system. A faster-responding manual or electronic boost controller on the wastegate will usually fix this, but I wonder too if porting the wastegate will help.

Dave

JyRO

iTrader: (3)

Thanks Dave,

I wonder if increasing the pill orifice size will not only allow the WG to react quicker, but the extra air volume heading to the WG actuator will slightly reduce the air going to the PC. Maybe increasing just the WG pill could control the spike both on the primary turbo WG reaction time (pre-changeover), and lower the change over boost spike?

I'm going to go the needle valve route on the WG for now. That's basically an infinitely adjustable pill. In the meantime, I've got cooling fan problems to sort out. They're not working. I tested them last night. I could get the driver's side 4 fin fan to come on, but not the 5 fin. But when driving, they never come on.

- JyRO

dgeesaman

iTrader: (7)

I think ball-spring valve is superior to a needle valve. It is most likely to help with the spiking.

Dave

JyRO

iTrader: (3)

Dave - Do you happen to have a link to more detail and/or where I could buy one? I want the best fix for the problem. Thanks.

- JyRO

dgeesaman

iTrader: (7)

Just run a seach for 'ball spring' - DaveW and Damian both have spoken plenty about their setups.

Dave