For a couple of weeks I'd been wondering about the boost levels in my '03 with an FM2 kit. Boost target set for 12 psi and running electronic boost control. Seems like the boost would spike and then taper off. I confirmed this with a couple of data logs showing boost reaching about 11.5 at about 5500 rpm and then dropping off.

I tried tocounter this by pushing the boost target up to 12.6 and, later, upping the minimum duty cycle. Nothing changed except the initial spike got a little higher. A friend with a similarly equipped Miata challenged me to a showdown at the local dragstrip so I really wanted a fix.

I decided to check my intercooler connections and all the piping connecting turbo to throttle body. Bam! Three clamps that were not completely tight although they had been ( I thought ). Boost came back, rock solid. Moral of the story, don't overlook the mechanical when chasing what appears to be an ECU issue.

1/8 mile time on street tires. 8.74 @ 84.5 mph.

Paul

 

Pretty quick. Congrats. Yeah back in my dsm days I start having issues above 20psi and went to t-bolt clamps. Issues solved. You can also build a tester out of pvc pipe of similar diameter of turbo inlet. Put a pvc cap on one end with a air hose/air compressor fitting drilled and screwed in. The other open end gets rubber hose to attach to turbo inlet. Put motor @ TDC and pressurize intake track above the boost you run. Pop and fix.

 

Example: https://www.miataturbo.net/diy-turbo...-tester-82894/

 

Thanks for the replies. I already have the parts to make a tester. Just never occurred to me to do it. I used T-bolts but something changed or I wasn't aggressive enough when I tightened them the first time. I never thought about a leak at 12#. Now I know.

Paul