Just so you know - I had a problem with my map sensor failing on my MS3x with MapDaddy.

I metered the actual voltage coming out of the sensor and got a completely different number than was expected.

It may be worth investigating.

 

Thank you! I will find the correct setting my citys current pretture is like 730 torr so that would be like 97 kpa! if my calculations are correct. I just studied gas laws in my chemistry class last month...

I also performed a leak test on the cylinders. while I did lap the hell out of the seats with good round valves they appear to be leaking when I put each cylinder at TDC. I can hear hissing through the exhaust and the intake side. I did get the head resurfaced before i assembled it as well so i am currently guessing that torquing the head to 80 ft/lbs like arp says could possibly warp the head enough for the valves to not seal properly.

I tried loosening the bolts and re torquing them to 60 ft/lbs but they did not seem to change the outcome.

I next plan to remove the cams and do the test to be sure the valves are up as far as possible.

 

here are some pictures of the car by the way!

 

Although the 80 ft lbs they recomend is too high, I don't think it would cause valves to unseat. It would just crack the head. In the very few Miata heads I've done, the valves have always been leaky (including mine). My machinist was able to "touch the seates" and leakage was back to a max of 4% or so.

If you can hear leakage in the intake or exhaust, pull the head and get a valve job. But I still don't think that is your problem with misfire under boost.

Has your car always done this? Or has it just started happening without any changes? If it just came out of the blue, I highly suspect ignition components. I thought I read you replaced the coils. Was it new? OE or aftermarket? New to me means never been tested. Especially if not OE. If used, who knows what you got?

 

I can hear it through the intake and exhaust but I have yet to take the cams out and test it that way (although I shouldnt have to) but I will perform a leak down test and post my results.
Also the coils I swaped out with were from another motor I pulled out before I built this one. so they were used.
the misfire did just come out of the blue, i made two pulls to redline and on the third one it started misfiring terribly.

 

Can you check to see if you are pumping oil out either of your breather hoses....we did 4-6 runs on the dyno, each one lost power (dived) at 6250 rpm...then the last run just belched oil out the exhaust side breather in to the catch and back out of the catch can everywhere else....i.e. engine became highly pressurized.

 

No oil comming out of the breather, i only had that happen twice and once was a broken piston allowing cylinder pressure to go into the crank case, the other time was my cracked cylinder head and coolant mixed with the oil and caused a white substance to come out of the breather. but i dont have anything comming out except for minor condensation that gathers in my catch can. typical of a e85 car running in 0 degree Celsius weather i believe...

 

Sweet, hopefully that means you got away with it!

 

Just wanted to post an update. I solved the missfire problem with coil on plug ignition, i made a set using the COP thread on here and that seems to have completly fixed the problem! however my lc1 started to act up and stopped working tonight while i was tuning it... now i wonder if it has to do with the COP's or the capacitor I wired in...

 

Hang in there, frustrating I know!

 

for those of you who are still experiencing misfires while running COP i decided to go the route of coil near plug and IGN-1A ignition coils. make sure you make the plug boot long enough to go over the ceramic part of the spark plug and you should have ignition coils that will have enough spark to arc across Canada.