Hey everyone! This is my first post asking for assistance on tuning. I'd like help or guidance in doing this properly and would like someone to review my current tune. With this website I have tuned and built my Miata with all the knowledge available here. I've had this Miata boosted for years running 91 octane at 15 psi boost. I am now delving further into this and have since changed a few things. Now I have a assembled a fully forged motor with a GT2876R which has a few thousand miles on 91/15PSI and now am going to run E85. I have the car running pretty well and it does hit boost at 20-22 PSI but I'm legitmately scared due to the amount of money now into this car and feel like I'm making mistakes.


Questions
While looking into my logs on E85 that visually shows AFRs like regular gas, I notice my AFRs are hitting 10.8 and my Duty Cycle1 while it raises past 100% yet it still shows rich. My Duty Cycle1 Goes above 100%, I expect it to lean out the AFRs yet it does not lean out much. I see it going 10.6, 10.8, 10.9 above 100% duty cycle which is leaning out but seems safe? This is confusing me because in the MS3 Manual says, if Duty Cycle1 goes above 85% recommended to change your injectors. Which I definitely will and am doing.

Another question, I really don't understand how to tune Spark. I've stuck with the basemap from trubokitty. Today it just dawned on me I should probably take a look at my ignition table. My table is maxing out at 235 kpa. If I run my boost to 22-24 psi I believe this has to be higher. Possibly up to 265 kpa for saftey margin? I'm not even sure how to start here or if there is a base map I can use that is higher or if it's something that gets interpolated or doesn't change after a certain point. Please any guidance on my tune/setup will be greatly appreciated. I'm started to get into a territory that isn't commonly found as far as I am aware.

Another question, is a flex fuel sensor required if I plan on only running E85? I understand that ethanol content can range from 55-85 roughly. I imagine it may flow more or less, which EGO could potentially help with the range to keep AFRs in check. From what I can tell a Flex Fuel sensor is only needed if running a blend or switching up with gas. Am I leaving horsepower on the table by not running a Flex Fuel sensor?

My setup
1996 Mazda Miata 1.8L non-vvt, Motor is from a 1994
Started with MKTurbo intercooler kit, swapped intercooler with CXRacing 18x12x4 for eclipse eagle

Block
-Manley Forged H Beam rods
-Wiseco pistons 83.5mm 8.5:1
-Boundary Oil pump
-ARP studs, ACL Bearings
-Baffled oil pan

Head
-Supertech double heavy duty springs
-New but stock lifters for a 94 head
-Stainless steel valves
-NB valve retainers

ETC
-MS3 built by Reverant
-Flying Miata exhaust/manifold with GT2876R .86 AR from ATP Turbo
-255 LPH Walbro FP
-FF 640cc injectors > I have 1050ID on the way due to my logs
-Stock FPR
-Skunk2 throttle
-6 Speed NB
-LSD 1996 Miata
-6 Puck ACT clutch rated 400 or 500+ HP (ballpark of my memory)
-Catch can setup (CarPassionChannel)
-AMP EFI Big Spark kit






Bonus cat

 

Once you go past the top row in your spark map then those values in the top row will be used for anything past that row. IE if the map only goes to 200 KPA then the 200 KPA values are going to be used for anything above that, be it 220 KPA or 350 KPA. Usually you'll want to build the map to the highest KPA you plan to run and then have another row above that drops off steeply in case you go past your target for some reason. So if you're planning to hit 265 KPA you'll probably want a 280 KPA row above that where you drop timing by a good 3-4 degrees (assuming the values aren't negative or something like that).

You're absolutely out of injector at this point. DW has a calculator here Injector Calc that should help you get an idea. 640 CC injectors on E85 are going to be pushed around 300 CRANK horsepower, which I'd have to assume you're considerably above given your setup. I wouldn't drive it turned up that high until you get your injectors.

I'm also not sure how Megasquirt does it, but if you haven't set up your fueling for E85 and it's still assuming pump gas then I would assume your AFR readings are off in some way or another. You don't necessarily need a flex fuel sensor, but it can be handy if you get a batch of E85 with a different percentage than you're expecting. Around here I usually see our pump swing from E65-E75. You also get fuel temp with a flex fuel sensor, so that's a bonus. Again, not required, but something to consider.

FWIW I have not looked at the tune/logs, but without your table scaled properly and your injectors maxed out I'd definitely turn the boost down until you're more confident in the setup.

 

Did you change the tune after taking those logs? The tune has a 9.8 Stoich ratio in it which makes sense for E85, but the rest of the tune (mainly the AFR targets) don't seem to be corrected for that. I'd expect EGO to be pulling everything super lean due to the AFR targets being based on 14.7 stoich, but the log makes it look like the car is running pretty well. Could be a MegaSquirt oddity though, I'm not too familiar with Megasquirt.

Also, you should rescale the spark map (IE get the spark and fuel tables to go to whatever boost level you're running) but if it was safe on pump gas it should be very conservative for E85.

I'd still turn down the boost until those new injectors get there. I see 120% duty cycle (I'm assuming that's injector duty cycle but MLG just says "duty cycle") and 11.5 in some of those pulls. Honestly I'd expect that to look a lot worse. 15 PSI/200 KPA looks like it's probably about as far as you'd want to run for the 640s. Just my $0.02

 

Understood, I gave an attempt to modify the spark table to reach 280 kPa. I unfortunately do not currently have a knock sensor or EGT sensor which at this point am beginning to think I need one. Can you tell, if this spark table is gonna blow the motor instantly? I think it looks okay, but I've never messed with spark before. I live at over 5000+ elevation with E85 so I imagine this would be safe?



I figured I am out of injector. I have AFR safety setup so I expected if it got out of range it would have enabled the safety. Surprisingly it kept feeding fuel and the car kept going faster. Hitting 20 or so PSI it felt like my body was floating. Feels like some serious power and got me worried since common knowledge is 640cc is not enough, my AFRs read okay, Duty Cycle1 does not look happy lmao.

When I switched to E85 I went into "Engine and Sequential Settings", Selected "Required Fuel..." Changed my "Air-Fuel Ratio" to 9.8. I followed OGPedXings video doing the "level 2" technique for the switch to E85 since I don't plan switching back and forth. I believe it is setup correctly, just reads as gas afrs on paper. Megasquirt reads Lambda and converts it to either Gas or Ethanol readings. Since I know gas I kept it to display as such. I could totally be wrong about all of this, but this is what I know. I don't know anyone else that knows how to tune.

Injectors will be going in tomorrow, I have modified my tune for them so I can simply drop them in. The VE table maxes at 84 VE when I interpolated down with using .60 as the value in the multiplier. It's looking much nicer.

 

I've never been on a dyno, so I can't say this is a good spark map, but this is what I've been running on ~E65 around 2700 ft. FWIW I'm on 9:1 pistons and have only run this up to about 240 KPA, and usually closer to 220 KPA. I don't see anything concerning on my knock sensor with this map.
I haven't seen a ton of E85 maps posted on here so maybe someone else will chime in with another data point.




Gotcha. I haven't watched that video but I assumed I was missing something because I'd expect the car to barely run if all the fueling was out of whack by that much. Lambda definitely seems like the better system IMO, but it takes some time to get used to. I use lambda but still have a better understanding of things based on 14.7

 

Hmm... Looking at your table I may want to pull 3-6 degrees from everything 180 and up as a start. Then get some detcans or wire in a knock sensor and take it to a dyno. I think we can get away with alot of timing on E85 though. No longer can I be afraid of tuning spark at these levels haha. I appreciate your input and hope someone else can chime in as well!

 

E85 is a lot more forgiving, but you can still go too far with it, just ask bloopdog. He cracked a piston about a day after that post (not guaranteed to be related to the timing, but just as a data point).

https://www.miataturbo.net/engine-pe...9/#post1673291

 

can confirm


though it may have been mis measured tight rings but i was running wayyyy too much timing. Car feels faster with way less timing and boost than it did with.

 

Gotcha, I've been looking at a bunch of ignition tables. Mine is looking scaled a bit weird. Makes me think I played around with it in the last several years. I'm thinking I could simply use the trubokitty ignition table, rescale the ignition load kPa and pull 2 degrees from 180 up.



Looks a bit easier to read and close to how your table is setup.

 

Oh yeah that is one spicy looking ignition table. 200 kpa hitting 30-32 in high rpms. trubokitty has it 20ish or so!

 

I've got it tuned up to hit around 20-22 psi now with the new injectors. These 1065 cc injectors hit like 60-70% duty cycle, car runs great no issues other than I gotta dial my IAC when letting go of the throttle. Sometimes it dies, sometimes it sits perfect at 950 and sometimes its chillin at 1500 rpm until I blip the throttle.