BREAKING UP BAD!!! TURBO MIATA!
 

Hello everyone I am so new to this form that infact this is only my first hour as a member. I have a 95 miata with a built motor, supertech forged pistons 8.6 to 1 Compression, manley forged rods, ported and polished head and ported intake manifold, flying miata fmII turbo kit with a gt3071r turbo, MSPNP2 ecu, 255 fuel pump, 700cc injectors but I increased rail pressure to 70 psi with no vacuum so they are closer to 850-900cc injectors "will be changed out for 1000cc soon" long story short I cracked the old cylinder head hand it pourd coolant into the oil "not much as i caught it immediatly." now I have Built a new head and installed it took the car out for a drive and due some fine tuning with the new head. the car ran and drove perfect and did not miss a beat, came home sat for a few hours as i re checked all the fluids, did an extra oil change and went over to make sure nothing was leaking. go out and drive it again and it runs perfect, go to work the next day and again perfect runs great onder boost makes a ton of power and no misfire. on the way home from work I jumped on it and it ran great again but when i let off it backfired " didnt seem unusual as i had it running a bit rich" still drove under normal conditions fine, BUTTTT!!!!after that when i go under boost "only happens under boost and is not in anyway rpm related" the car missfires and will not accelerate, like i said it drives completly normal unless i go under boost, i do not see any vacuum leaks. So i got home and checked compression C1 140 C2 135 C3 140 C4 130 now i personally thought those numbers were low and yes that is with the engine at about 100 Fahrenheit but i am running low comp pistons, old cracked head "before it was cracked" had comp test of C1 150 C2 145 C3 145 C4 140. and in my attempt to solve the miss fire i changed the plug gap in my NGK R5671A-7 from 30 to 25 and i also replaced the plug wires " all snapped on correctly as i double checked like 20 friggen times" which it still misfired. so i bought new plugs and nothing changed. so i took my old set of ignition coils and still changed nothing. not sure where to go next, CAM Position sensor? Fuel Filter? Clean Injectors? The car was driving perfectly fine under full throttle and all of a sudden it happpened. So hopefully one of you guys can shed some light on the situation i appologize for the long post but id rather you have all the information than not enough.
Thanks for any help!!!
Donald Jackson

Wow that's a wall of text. Take care writing your posts, you just lost half your readers with all that. It's very wordy with no spaces. Breath...

Have you checked all your charge pipes after the misfire for leaks?

Attach your msq so we can see if we see anything wrong.

Did you sync your timing when you initially installed it?

What's your over boost protection set at?

I was going to say the coils until you said you changed them.

Post a datalog from your Megasquirt that shows it breaking up. Maybe there is something that it can tell us.

Yeah, wall of text is hard to follow on the mobile application, too!

Sorry about that wall i just wanted to give you all the info that I had, i have not checked my charge pipes i will have to do that.
Here I did attach the file and yes I did sync the timing
Please excuse the file name.... haha

Maybe this makes things easier to read.

How much boost?
What does the wideband say when you do this?
Can you repeat the problem while datalogging and post the outcome?

15 psi of boost, wide band reads lean and here are two data logs.. im not sure how the data logger works as i have never used it.

Update Changed CAM Position sensor and timed it with still no change. here are two videos i made showing what is happening.

Quit buying and or replacing parts.

Edit*nvm

In your tune i noticed that you have "use cam signal if available"; it is checked "off".

Also, to record a log you hit Ctrl-L. Then just hit spacebar when you're about to go into boost as it makes it easier to find when going back through the log.

It sounds spark related as i've had spark related issues before. You said it went lean though, doesn't make much sense.

I had my dad drive it while I looked at the guages and it appears that it doesnt really go lean. i will try to see where that use cam signal is and check it

Update. I changed that ignition setting to use the cam and it didn't change anything. Do you guys think resetting the megasquirt would help?

Try and take a proper log. I don't know about anyone else but I can't see anything in it.

Tried my best to take a proper log and here is what I got not sure if they all worked but at least one of them should have something. i know the afr was jumping around like crazy and not sure if a data log should make the tach jump when you click stop but it did.

Try leaning it out. Right before it hits the wall, you're choking it with 10:1 afrs. Lean it out closer to 11:1 or 11.5:1. Although I see your target is 12.3:1 there, so it really just needs to be auto tuned.

But with the RPMs bouncing like that, it does look like a software rev limit, not a symptom of richness.

I will try leaning it out there but it should be going to that 12.3:1 because I was running auto tune or atleast going close to it. do you think it could be a problem with my software? it sure feels like an electric problem with the way it cuts out and comes back on, it sounds like the flat shift which i have disabled and never worked on my car anyways. i am wondering if possibly reloading the firmware on the ecu will fix the problem?

Swap out those plugs for ones with resistors. BKR7E is the defacto standard for a reason.

I didn't read your post, or watch any video, but your problem is spark.

edit: now that i've read, you absolutely have to replace your spark plugs!!!!!

I reccomend BKR6E-11.

I had a very similar problem, pretty much exactly like your car when I saw the video. It was my spark plugs as others are saying, changed them out to BKR7E and never had another issue.

Brain, why do you recommend heat range 6 rather than heat range 7? TSE recommends 6 for NA, 7 for forced induction.

because 1.8Ls have a heat range of 5 stock, and there's no reason to jump 2 heat ranges.

I'd run the hottest plug you can get away with.

I do have a set of ngk r5671A-7 and BKRE5ES. I will try a hotter plug and post the results

Also just in case i checked my cam timing to see it if possibly slipped a tooth and it did not.

I learned how to take better data logs and here is my most recent.

Well I ran the BKRE5ES gaped at .030 and it did not make a difference... could it be the megasquirt having a software or firmware issue?

BKR6E-11

They are about $2 apiece. What you have above is not a BKR6E-11.

I still think your tune is part of the problem. Your accel enrichment is WAY too high. Every time you touch the throttle in the logs your AFRs go to 10.2-10.3. That will flood out a marginal spark.

Get the right plugs and gap down to .025-.028

MAP sensor choice-- I don't think I ever got down to 12.4 KPA on decel with my car. That makes me wonder if you have the right selection for the MAP sensor that is in your MS.

I still think you have the wrong plugs, weak stock coils, still gapped a bit too wide, overly rich accel settings, and possibly selected the wrong MAP sensor in TS (there are several choices and it is easy to do).

That's my best guess so far.

I watched your videos. it's more likely a tuning issue.

I will say, last time my car acted like that I had water on the spark plugs (washed engine bay) and it was making my spark signal weak in boost.

But yeah, i still wouldn't run resistorless plugs with a MS. Members in the past have reported having tons of electrical issues when doing that.

I bought the BKR6E-11 plugs gaped at .025 and then in tuner studio I removed a lot of throttle enrichment and got the afr's while pressing the throttle down to 12.0-12.5

the MAP sensor is the one that comes in the ecu and I used the constants that DIY Auto Tune provided with my ecu.

with doing all of that the car seemed to pull harder (possibly because of not running so rich) but still when it hits more than 5 psi of boost or so it starts to missfire and rpms do not increase if you stay in the gas.

compression numbers were 150, 140, 135, 140 (running 8.6:1 comp pistons).

do I need Bigger ignition coils?

Well I did even more testing this weekend and this time I reaclibrated the O2 sensor, changed my tps, used the tune that DIYAUTOTUNE supplies with the ecu software cd. went out for a drive with the ve-analize running to make sure the ve table was being tuned to the afr table. and after a few miles of varing speed and entering low boost (0-3psi) I attempted to go a little higher into boost and it just started breaking up.

Before you tell me to change my plugs again i am running the exact ones you guys recomended BKR6E-11. gapped to .028 my coils tested good ( and i have swapped them out with other known good ones) my fuel system is definatly up to par and my sensors are all working properly, my cams are timed correctly and my compression is what is has always been.

so I plan to send the ecu back to get tested, i had a bad injector driver in the past so it is possible to have it go bad again.
Thanks for your help guys I will let you know what happens

I'm only a noob at tuning but in the summer when I got my car going and tuned by my friend and I we had something very similar in sound. Turned out that auto tune couldn't adjust quick enough and was running very rich. We had to modify the VE table not in auto tune. Cleared it right up. Just a thought.

I also had this.

OP get rid of that pig rich spike to 10.0 when you jab the throttle.

Also. Is your rear bumper all covered with black soot?

I am running on e85 so i do not get the black soot build up and the pig rich spike is now gone, i can try to lean it up some more. the car ran completly fine on the tune it had and all of a sudden it started out of nowhere.

Ahh duhh e85. Total brain fart.

OP's username is confusing me more than it probably should.

here is a data log from a few minutes ago logged in 4th gear and slowly getting on the throttle

Agreed. Using the "Jackson Racing" name is not a good idea IMHO.

Ahem.......you haven't changed to ARP head studs have you?

We had a similar problem you describe.......engine builder followed ARP instructions even though he thought it read high.....

we have the exact same compression figures you have on our brand new motor. our symptoms were a little different..but the instructions provided with ARP studs (from 949racing) were nearly double the torque required on our motors.

We believe it ovaled the bore, and probably ruined our newly rebuilt head...but have been to busy setting up and tuning the loan motor to pull it down and check.

may be wrong but thought it worth mentioning.

In your log at 4814.689 seconds it shows you are at 100kpa at 3530rpm at a very low throttle position. It shows you to have 12.2AFR there, which is still pretty rich. But I question if you really have 100kpa there. I still think you have the incorrect MAP sensor selected in your project setup menu.

Try an experiment for me. With the car off, turn the key to the "on" position and read in TS what the kpa reading is for us. And tell us your approximate altitude above sea level.

i had what felt like a miss fire and i was dumb it was over boost protection kicking in... hahah rasied the value that fixed it ;)...

Yes actually i am running ARP studs and they are torqued to 80 ft/lbs i believe factory torque is 60? the last head i had ended up cracking in a weird spot that i wondered if it had to do with too much torque on the bolts...

I did the test and I got 91.6 KPA at a level of approximately 790 feet above sea level.
i may have the wrong map sensor im not entirely sure.

And im sorry if my user name "jackson racing" offends you but honestly if it does i dont give a S#** because my last name is jackson and i do a lot of racing.
Thanks for the help guys i really appreciate it. i am new (by new i mean only been building this car for two years) to fuel injection.

You better search "miata Arp head studs" you will most likely experience that same sinking feeling we did...I think the warnings are 45 max...or similar.

We are about to tear ours down and measure up for any permanent damage.

Does anyone know if the valves leaking would cause the engine to misfire under boost? if that's the case then i will have to take my head off and see if any damage occurred. my previous head cracked (assumed from torquing the bolts too high) 80 ft/lbs seemed high to me as well.

91.6 KPA corresponds to about 2400 ft above sea level, and not 790.

Select the correct MAP sensor in tunerstudio and you will end up with much better fuel metering.

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.