I was just wandering what causes boost spike on turbos and how can one fix it? I am thinking of going turbo in next few months if my business deals go through.

 

Depends.. Cold weather can cause a spike of ~2PSI

A MBC can cause a spike of 5-10 psi

Electronic Boost controllers have about a 1 psi spike

 

From reading JAY's turbo facts, exhaust that's too small can cause bad spikes. That is if you're running over 6psi on stock or 2.5" tubing.

 

So If I run an EBC and 2,5 exhaust with 6psi I shouldnt spike too bad. Any other way to keep it from spiking?

 

Setting the Gain feature in the EBC will also keep the spiking under better control. I am greedy, I have my set at 90% gain. The 3 inch exhaust combo helps the spiking issue.

 

Hummm stupid question, but what exactly is a "boost spike"?

 

If your wastegate or boost controller is set @ 7 psi and you see ANYTHING higher than 7 PSI that is a boost spike.

 

Now I know why your dyno is so WaAVvvvYYyy.

That plus too high a dump and too small a WG.

 

is the EBC trying to control and keep up. 10.2, 10.0, 10.3, 10.2. Remember I did not design my stuff. thats the wavey you see up and down. I aint changing jack on this setup. 353 untuned @10.2 PSI. I wonder what I will get at 11PSI tuned?

 

IIRC...you have the limit(how much is dumped?) set at 7%, which might be high, but necessary with that high gain to bring the overshoot down quickly.

IMO what is happening is that the EBC gain of 90% causes quicker spool by not opening the WG until VERY very close to your desired limit of 9.7psi?. Once that limit of 9.7psi is hit, the EBC solenoid attempts to open the WG in time, but it's too late and you overshoot. Then the limiter kicks in and dumps 7% to bring it back down spike #1. Then the EBC slams shut WG to build boost back to 9.7psi, but because of the 90% gain it overshoots the 9.7psi, triggers the boost limit, and dumps 7% again, causing spike #2. This keeps happening over and over causing the wavy line.

I think a bigger WG would allow the EBC to dump more pressure in a shorter amount of time to reduce the overshoot and you could also reduce the limit ratio down from 7%. Or it could cause it to get worse, I don't know.

I think a 90% gain is too much for the EBC to react in time and your limit ratio isn't too high, but higher then necessary. It has been a LOOOOONG time though, so I don't remember what "typical" setting are. I know Kev with his T4/60-1 didn't have that high of a gain though. You might try to lower the gain down some and adjust your boost ratio(target max psi) higher?

What is your boost ratio set at?

 

I have it set like that because of the hot heat. Air is not so dense. It holds shut until 8.5PSI after that it hits 9 instantly and starts to blink red at 9.4PSI which explains your theory up there so by now is dumping but it climbs to 9.6PSI very very fast and thats when a minor spike occurs. I have something up my sleeve so stay tuned