SR20 overboosting problems
 

First I'll list my set up.
T25 Sr20 turbo 7 psi actuator with a 3 inch downpipe vband to a 2 foot pipe. Rx7 460 cc injectors, eBay bov, diypnp ms2.

Problem:
My car is overboosting way past 7 psi. My overboost settings in ms are set to 205kpa. I'm really kind of clueless to what's my problem and this set up has only been on my car for a week.

I'd appreciate any input from you guys thanks.

I'm sorry, but 3 inch downpipe to a 2 foot pipe?

I think I see your overboosting problem right there if you are using the stock SR20 internal wastegate :(.

Yea I was kind of thinking that was my problem. Do you think if I had a straight pipe added it would fix it?

It might.

What I'd do is port the SR20 internal wastegate as much as I could, then go from there.

Ok well how much do you think I should port it?

205 kpa = ~15 psi. That's your problem. In terms of overboost protection.

https://www.miataturbo.net/attachmen...1&d=1332035037

Do what he said. Port the wastegate. Also, make sure your wastegate flapper can open ALL THE WAY.

What downpipe do you have?

I'm fully aware of what 205 kpa. I raised my overboost protection up that high to see why my turbo was boosting so high.

I will pull the turbo out soon and port it. The downpipe I have looks like it was custom put together. It came with the turbo and manifold.

Does your wastegate flapper open all the way when it is not connected to the actuator arm?

I bought a china turbo and even though the listing said the wastegate is rated at 7PSI, it wasn't opening until 10psi and probably fully opened around 13-15psi. You can disconnect the wastegate and do a quick check.

my real question is why do you want to only run the SR20 turbo at 7psi?

anecdotal evidence - when I ran my SR20 turbo it was spot on at 7-8psi without any boost control. To get more boost I had to tighten the stock wastegate actuator with some washers and run an MBC.

He does't the overboosting problems get worse with the MBC in, that is why over boost was set for 14 we were shooting for 12. Spike and spool were WAY to fast with the MBC so it was removed to drill the breather bigger.

After the MBC was removed we were STILL seeing 14psi. The car can't be run WOT or over 4k, just hits overboost.

check for full articulation of the wastegate arm.

are you sure it's a 7psi can? but a 3" DP to an open dump will probably cause overboosting issues.

Port your wastegate dude.

Hell, check how the RX7 people port their wastegates if you need more. Also, make certain your wastegate actuator can reach it's full range of movement - very important.

Should I be able to move the arm fairly easy?

Without the wastegate actuator attached? Yes.

Put an air compressor to the actuator. Started at 10, nothing kept going up to 60 and it just sounds like its leaking through the actuator. Is there a diaphragm in the can that may have busted?

Well, you may have found your problem.

Disconnect the wastegate completely, then try to run the car. See if you still have the same problem. If you don't overboost like crazy, your wastegate actuator was fucked.

With the wastegate arm disconnected can you open the flapper? Are you sure the flapper is not hitting the downpipe? When I first got my chinacharger installed I had a similar issue.

Well this turbo and downpipe were used together by Wayne curr. I bought the turbo, manifold and downpipe from him. I don't see why the flapper would be hitting the downpipe now. I'm letting the car cool down before I remove the actuator arm from the flapper.

It can have to do with how wiggle room you give all the bolt holes. Just moving it slightly can make a difference. With mine I believe I just had to move it slightly to the left and it worked fine.