I've always had this boost spike, at first I thought it was because I had my actuator line coming from the intake manifold, today I moved it to the turbo outlet and I've still got the same 2psi boost spike to 9 psi then it goes back down to 7 psi.

I've got a sr20 t25 on my 1.6 engine. The WG has not been ported yet, didn't know if it would need it or not being that it's off a nissan and I'm sure they don't make their cars with boost spikes. The nissan it came off of normally runs 7psi stock. At the time that was my goal. I also tried to up the boost a little to 8 psi, same result of a 2 psi spike to 10 psi. I have a slight preload on my actuator, it's not adjustable, however I would think that releasing some pressure off the rod would only lower my boost and still have the spike.

I can't think of anything else that would be causing it right now, I do have 3" straight through exhaust, I've read on here that free flowing exhaust makes boost spike worse but I don't have anything to restrict it right now. If I could make a baffle to stick in there to restrict the flow to see if the spike goes away it would pin point that it is indeed the waste gate being too small right?

I'd like to fix this asap so I can boost 10 psi this weekend weeeee!

 

Not much you can do. You can try porting the wastegate, or just accept the fact that it's boost spiking. My 300ZX T25 would boost spike to 18psi, and then settle in at 14. I wouldn't worry about it going to 12psi for a short time then settling at 10.

 

With 430cc injectors you could run that little turbo to 14 or 15psi without issue, just raise up the boost and ball hard.

 

The injectors are only running 46% duty cycle so your right there. I'm more worried about the motor, it's completely stock except for the turbo stuff. How much can that engine take anyway? I've heard more than 220hp is risky but I don't know how much boost I would need to be at that level.

 

On a good tune, 250hp is easily doable on a stock block. I would guess that 14-16psi would put you at 230whp+. Show some mechanical empathy and the motor will be fine.

 

On a sr20t25 14-16psi would probably be about 200hp.

 

...

That's sad. I guess I've been giving those too much credit.

Edit: To be fair though, from the dyno sheets I've seen, it looks like 16psi on an sr20 t25 + 1.8 would get you close to ~220-230whp. 1.6....not so much.

 

 

T25 s love to spike. Fairly normal to get a 2-5psi spike.

Most just live with it because it doesn't really hurt anything with T25 on the SR20. External gates get rid of the spike and gain some power. 38mm works great for that.

 

I guess I'll deal with it for now. It's not a massive spike anyways, just very annoying to watch. I'll port out the waste gate later.

 

I got 156hp at 6.5 psi without an intercoooler. I installed the intercooler and changed nothing else and I gained a very very nice amount of power, how much is unknown. It did drop the IAT's 40-50* or about 3* above ambient. Time for a redyno for sure.