Brap-Brap

Need some help diagnosing/moving forward.

Car: https://www.miataturbo.net/build-thr...7/#post1508776

EDIT: Am extremely dumb.

NB2 injectors flow about the same as NA8 at 45psi, the NB2 uses 60psi rail pressure. I didn't install an AFPR and WBo2 or else I would have realized its been running lean and could have corrected my fuel pressure.

So, how bad of an idea is it to build a motor and install and learn MS at the same time?

Resume thread:

Full motor specs:
2001 Bottom end 93k miles
99 BP4W head refreshed before use
Square top intake
NB2 injectors cleaned and flow matched by FIC
Roadstersport header
CX racing intake with an Apexi Power filter, with a heat shield to separate the header from the intake and a NACA duct headlight lid feeding fresh air to the filter.
Cams are stock BP4W
Supermiata reroute with 195* Tstat
Supermiata crossflow rad
Rtheory hood vents
LRB Speed undertray
I was running 93 octane at the time on stock ‘97 timing of 10 degrees base timing.
Always bled with a spill-proof funnel, using the bleed nipple on the reroute and having the front end jacked up while the rear is on the ground.


Last year I put a hole in my #2 piston while on track. Car ran hot-ish (like 220-225 peak) on track and exit of a turn I went to accelerate and got nothing but smoke. Motor was a stock NA8 motor with 94k. I had an FM catback, CX intake with a Apexi power filter, same Toyota COP kit.

Now a year later I put a hole in another piston, this time Cyl #1. Car got VERY hot (I saw 245 on the gauge one time). This was a hybrid motor built from a stock 01 bottom end with 94k miles and a refreshed BP4W head. I was using NB2 injectors. Square top intake, Roadstersport header, same intake and same exhaust as before. Same ignition.

Only things I didn’t change were the radiator, reroute, ignition system and fuel system (except for injectors I had them cleaned and flow matched for the new motor). I do have a Toyota COP setup with a harness I made myself. It does have the 10000uF 25v capacitor across the power leads as recommended by MiataTurbo. I am on the stock ‘97 ECU. Coils are OEM Densos about a year old.

I do occasionally get a P0420 code however I was assuming this was due to NB2 injectors. I did get the code occasionally on the old motor as well. I have a magnaflow high flow cat.

I do also occasionally get the P0300 random misfire code as described by the TSB for the ‘96-‘97 however the car has run great, and it only shows up when doing a pull in 4th gear after I reach 5k RPM and it’s not 100% reproducible. And both of my ‘97s had that issue and ran great with it. I did an entire track season in 2020, 14 track days on the old motor with this issue and did not experience any motor issues. I blew the stock motor in 2021.

What should I check and what further diagnosis should I do if any? Is my ECU suspect? How should I be checking my ignition and injection harnesses?

Alejo_NIN

iTrader: (2)

get yourself a real temp gauge and monitor the temps.

have you hot tanked the block?
it sound slike you may have some blockage. do a radiator flush.

Brap-Brap

I do have a real temp gauge, that’s where the temps I was mentioning came from.

And no after the ‘01 motor was pulled from the junkyard car I just took the head off, cleaned the block up and reassembled the motor with my fresh head. I did flush it in the car however I think I need to do some more serious cleaning.

Alejo_NIN

iTrader: (2)

yes, it looks like as some passages may be blocked

even from the junkyard, i would never ever just throw it in there...at a minimum i would knock out the coolant expansion plugs

LeoNA

Detonation. Most likely it’s the trifecta at a low level, a little too lean, too much timing and too hot. Also making it work very hard. The ac condenser is not helping those temps. I read through your build post, but fairly quickly due to its length, ha.

Have you checked the fuel pressure and what fuel pump are you running? These engines all had egr system’s which reduce the combustion temps. With the stock ecu you may have to run a few degrees less initial. Have you been setting the timing by using the a jumper on the diag plug? Im guessing that you have stock fans because of the ac, if so I would go to larger un-shrouded fans with better wiring. The oe wiring can trigger the aftermarket relays.

The under tray and sealing around the rad is important. I made sealing gaskets from the gray Harbor Freight floor mats. Coolant concentration can be an issue. I have been using a splash of the reg green, maybe 80:20 with a bottle of water wetter. If you are not running the egr and would like to run a fuel cooling strategy you could go with an adjust fuel pressure reg and a wideband. Check the oe pressure and afr’s first before making this change so you have a bench mark.

Brap-Brap

It was quite quite rusty when I was flushing it... Well now that I'm rebuilding it I've got a chance to fully tear it down and see. Also proper cleaning.

Also need to take a good look at the radiator.

I did delete EGR just before the track day and know how/when it triggers (and then triggers the CEL). It doesn't affect anything track related as its not on in that running environment.

I didn't check fuel pressure, just used the NA8 FPR. NB2 injectors, cleaned and flow matched by Fuel Injector Clinic before install on the new motor. Stock NA8 pump.

Honestly some super smart people ( @doward ) and some friends said I should have installed a wideband, Adjustable FPR and a gauge to at least quantify and maybe tune/ adjust the fueling. I did none of that. I honestly slammed it together to try to make a track day, then didn't go, then promptly kept driving it and not worrying about it.

I was setting the timing with the diag box.

I have 2 Spal 12" fans that are the same fans as the FM stage 2 kit, but no shroud they're just ziptied to the rad.

I do have an LRB tray but its not fully sealed. I should probably do that. LRB tray should give me a good start though.

I do run 70/30 water/coolant and a half bottle of water wetter.

My current plan is to rebuild the motor, and start with an AFPR, WBo2 and an oil temp sensor for instrumentation. Maybe record some OBD2 logs with my phone.

I will be sealing up the rad, maybe having a thought about running just one fan.

The most important thing to me is to get the cooling in order because that's a more serious issue.

If the stock ECU is being too funky I will go MS, its a large enough investment of time and money that i'd like to try the hack way before I go full standalone.

curly

iTrader: (25)

I’m tired of the hondata honestly. Can’t adjust idle without speed input, can’t adjust cold idle speed, can’t adjust AC idle up settings, x12
fuel tables and x12 spark tables is obnoxious. I started with MS, now tune link, aem, Haltech, a few others. Like them all, but the hondata is very annoying.

Brap-Brap

So as I'm looking through stock rebuild engine parts and thinking "well while i'm in there"

I'm very very quickly moving away from stock ECU territory. How bad of an idea is it to build a motor and install MS at the same time?

Or, should I be looking at another used bottom end for a known quantity to sort out my cooling and then running stock ECU with an adjustable fuel pressure regulator and a wideband?

Gee Emm

I wouldn't do it - unless I used as a starting point a map ticked off by a pro/very experienced tuner. In fact I wouldn't be doing very much at all except running down whatever is the problem leading to your piston issues. YMMV of course.

Brap-Brap

Noted, I do have several experienced tuning resources local to me and will consult them.

I just edited the first post, I ran NB2 injectors on stock NA8 45psi base pressure. NB2s run 60psi rail pressure. No wonder I ran lean and melted a piston.

curly

iTrader: (25)

Sorry, this old man's been frustrated with one too many Hondata projects and mis-replied to your thread.

OP, I actually read your original Facebook post, and I agree with everything Emilio said there. You're in desperate need of a wideband and a FPR at the least. Most stock cars run at 14.7 until around 4000rpm, when they slowly transition into the 11s. If you've leaned out your car at all with intake, injector, or other changes, you'll bring those lean numbers into dangerously lean territory.

Brap-Brap

I appreciate it.

I'll do you one better, I ran my NB2 injectors at 45psi base pressure and not the 60psi they were designed for. Definitely beyond dangerously lean territory lol.

I'm putting together a rebuild parts spreadsheet, the more I look at how much a rebuild will cost the more MS appeals to me.

LeoNA

I don't think that is an issue. I believe they are about the same lb/hr, The difference in operating pressure is accounted for by the NB2's ECU programming.

Brap-Brap

https://www.miataturbo.net/prefabbed...nfusion-32655/

According to Brain they flow the same at the same operating pressure, however I suspect Mazda spec'd 290+CC injectors into the car for a reason. I think I found said reason.

LeoNA

How much fuel is dispensed depends on the ecu. Maybe Mazda did run a richer AFR in the upper range which necessitated a higher fuel pressure to get more output from the injector because of the higher compression and heavier car. This is why I would run a AFPR and wideband. Especially if you're tracking the car. If you don't switch to a stand alone then you have to get some metrics before implementing the AFPR. Most likely -2deg's of timing and a few psi across the board will solve the problem. I would run a better pump as well. If you switch to a stand alone you will have the option of logging.

Ted75zcar

iTrader: (2)

NBs have static rail pressure, which means that as load increases, the effective flow rate of the injectors decreases. If you run manifold referenced fuel pressure (3bar relative, NA style return system) then at sea-level WOT an injector sourced at 3 bar relative will have 4 bar absolute.

Brap-Brap

The more I think about it and the more the costs on this project climb the more MS appeals to me. Especially logging. My previous internship supervisor (A Fracture mechanics test engineer) told me to think about it as a test controller and not an ECU. "If you're messing with an unknown you'd want as much data and logging as you can get... you really trust yourself to remember the exact AFR, throttle position and RPM from 3hrs ago when you're in the garage messing with the FPR?"

Right, but on this forum the data is the NA is 35psi normally and 45psi at WOT. Is it really 4 bar absolute? The way you're explaining this sounds like the NA and NB injectors flow the same even though the NB runs 60psi rail pressure.

To me, all of my engine damage points to extreme detonation and running very very lean. My entire fuel system is suspect (especially the pump since that's the only thing in the system I didn't change between the motors), but the fact I was running the injectors at 1 bar less fuel pressure than they're designed for seems like a pretty obvious oversight on my part and an easy explanation of my issue.

LeoNA

The increase with the fuel pressure and decrease in initial timing will be somewhat linear and will change the entire map. The areas that are lean will be richer and the areas that were rich will also be richer. It's not a very refined way to improve the fueling, but it will guarantee more fuel. You will not be able to compare the fuel pressure/afr's at many or enough different loads. You basically pick one reference, maybe idle and increase relative to that. You can observe the wide band AFR's at a few different engine speeds/loads to confirm the results. The decrease in timing might be the biggest factor in decreasing the detonation.



This might be a factor if the ecu was switched to the later ecu and run with the lower fuel pressure/referenced FPR. The ECU dictates the fueling not the injector or FPR..

Brap-Brap

The more and more I hear how hack-y the AFPR/WBo2 method of "tuning" is the more I don't like it...

I'm also planning on boosting this car eventually so familiarizing myself with MS from now seems like a good idea.

LeoNA

If a turbo is in the future go with a MS. I went with a MS3Pro PNP when I was NA for a few months before installing the turbo and it worked out well for me.