Subaru ECU

mycar has a stock ecu and I am chasing down an intermittent bucking horse around 3200rpm and above

I have been to my tuner many times and I get there and it hides on us.

He says that an Atom Ecu that they use a lot give them so many more options ... I asked about the stinger  and he said they take those out all the time ... they did a spyder, with a 2.5l n/a and did just that recently... anyway just thought I would post this info

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Ray..........John at Outfront here in Buena Park Ca has been using Stingers all along.  I think I got his last one because he can't get them any more. He seemed to like them and is regretful that he can't get them anymore. Maybe I'll suggest to him to look at the Atom if he hasn't already.  Can you give me more info about the Atom ?.....Bruce

Link atom,  it handles all sorts of 4 cylinders and they have different models but my guy says stinger is like fred flinstone compared to this unit

It has a cold start set up as well and accorsing to him  it simplifies your life tremendously but you have to install it and do a proper set up to tune it 

he does all sorts of race cars and dd.

it can even do cruuse control if you have drive bu wire pedal  


I agree. MS has come a long way and is available all cased up, verified good, and with a wiring harness. Doesn't get much better than that. Microsquirt with a harness is less than $400. I keep thinking about it. I have CB(IDF type) throttle bodies, TPS, fuel injectors, rails, pressure regulator and fuel pump. For me, after the initial ECU investment, it would be down to wiring, plumbing, then programming.

Megasquirt, with a Mario-made harness, would be about 1000 all told for ECU and pre-made harness, and most probably a start tune installed already.  

I’ve got a MicroSquirt controller and the harness (but none of the other stuff), Danny. MicroSquirt (for those of you who don’t know) is just MegaSquirt in a totally sealed controller, suitable for mounting in a wet location (like an engine bay or motorcycle).

Back in the day, you had to solder together your own controller to do this. It hasn’t been like that for quite some time.

I’m not sure if the controller has drive-by-wire capability, but certainly has provision for a warm-up circuit, etc.

I’m looking pretty hard at doing this next on the Type 1.

OK...I'm totally a dumb a$$ when it comes to all the new electronic stuff. ECU's, drive by wire,  even the etc. stuff.  So where do I start ?  This next year is going to be a real serious learning spike given I've invested thousands already and only have one component  so far. Any  Basic Books out there ? Do I rely on you guys to coddle me ?(my pride surpassed right now)  Need some guidance to start out in the right direction. My Father always said that if you are serious about learning to play Poker, put your money out in the pot ! You will "pay" attention !


Bruce, are you doing all the wiring/plumbing and programming? It's a steep curve, and while very well versed in wiring, electronics, and programming, I haven't taken the plunge yet myself. There are books out there, I'm sure. Probably a good thing to read at night. I'm sure they'd put me to sleep. I'd read them in the morning with a cup of joe.

I've been thinking about it for a while Stan. I was looking at Speeduino(you solder or get one built, but still have to case it up and wire plugs in). I don't think Microsquirt can do drive by wire, but maybe. I think it's best to do batch fire on injectors and wasted spark for a first attempt. You could always add a cam sensor and a couple coils for sequential later. You know, once that learning curve flattens out a little.

Probably good advice, Danny-- but you know me. In for the penny, in for the pound. If I'm doing this, it'll absolutely be sequential. I've never had any desire for drive-by-wire, so that's not an issue.

I know a single TB is better by every metric, but I can't bring myself to do it. It'd have to be nice 4-pot TBs, sitting there looking cool. I know that means you sinc the TBs, etc.-- but I care not.

The thing that keeps me from it is that my set-up (when working well) works so well. I really, really like the "evolutionary dead-end" aspect of the carbs, getting way down in the weeds on something that nobody cares about any more. I suppose if my health holds and I still have a fun-bucket at the end of all this, I'll do the full-meal deal EFI, but there's a big part of me that likes the analog aspect of it. A lot.

I ran down to the bank today in my speedster. While I was motoring around, I saw a guy today at a gas station with a '70 428 Mustang fastback, and wheeled in to talk to him. The guy had owned the car since he was in high-school in 1971. Big-block FoMoCo power backed with a 4-speed. No air, factory wheels. It was a great story, and the car was stunning.

I stood there admiring his car and asking questions, while he pretty much ignored my funny little furrin' car. The whole time I'm thinking, "This guy's car is stupid-cool, has a great story, and is worth a fortune. I'd still rather have my little troublemaker". 


Analog or ECU there is always a learning curve and if your doing it like at the level of Stan or Danny then why move out of that environment, you know that system well.  

Moving to an ECU for me is learning another kettle of fish.  When the system gives you an engine light or it may NOT  and you have to trace down a symptom and the ECU is not really telling you much it can drive you crazy just as much.   ECU's are not necessarily adjusted for each car made in a model year.  So you can end up requiring minor adjustments while the ECU is reading within range.  The usual dealer set up is to start changing modules.  (when you get to $1500 in new parts you hope it works, MAF, EGR, Air Fuel mixture, sometimes O2 as well ) 

In the case of an engine even with stock ECU in a speedster you may or may not have the air intake pipe the same with a K&N, it could also be a different diameter for airflow for the MAF sensor then other sensors may not be there etc.

 Not to mention the headers and exhaust being custom may again give you different Air Fuel readings.  All of sudden your running lean or rich. 

All this to say you may require an Ecutek program to tune a stock ECU from Subaru and/or you might goto another ECU like a Stinger or Atom and your tuning it again at least in the initial set up.  

Conclusion, pick your poison or medicine and I'll dispense with anymore talk, for now about my journey in the ECU world. 

I am going to ECU because I'm using a 200+ HP Subaru power source. Even though I totally relate to Stan's affection for the look of "four holes" VS one, I  just want to move on after 40+ years of playing with the VW/Weber stuff.

Having been trained ("A" School & experience) in the Navy as an Aviation Electrician, I am confident of my wiring and electrical skills so that part is not an obstacle for me. Electronics and modern engine controls have passed me up over the years due to lack of interest or application so now it's time to catch up enough to get involved. I won't even start my build until early next year so I'd like to take this time to "go to school". Are there "complete idiot" books on this subject out there ?

Another thing, since I live in SoCal, there are lots of places close by that I can go to if I really get in trouble so this is a confidence builder for me to enter into this endeavor. It's just that I really want to learn about this technology enough to make most of the right choices the first time........Plus keep my 77 year old brain from fading into the dirt (or is that sunset??)..................Bruce

Pretty good for a 77 y.o. Bruce keep going... my mother only started to slow down after 90  Another friend's dad slowed down only after 97 due to his hips he died at 100 last year.  His attitude was stellar, he said to his 65 y.o. son, I will work until I die, not wait to die.   BTW , he had 3 wives and 18 kids while living. 


I sure hope you don’t stop talking about this stuff. You are a font of information. I’m still curious regarding most of the Subaru guys avoidance of MS stuff. Please enlighten me, I really do want to learn. 


I hope to be half as mentally agile as you when I am 57, let alone 77.

I'll be there in 3 years, Stan, and have 30 at my job.

Keep this going, I enjoy the thinking, Ray and Bruce.

Stan, totally agreed about the ITB situation.  If you do take the plunge and end up with a different ECU, I'd be willing to make a deal on that Microsquirt. That might be the last piece of the puzzle that drops into place for me. If I had that, I don't know if I could find a reason NOT to EFI it. I think the only thing I would need after that is a wideband controller to feed the ECU, I've already got a couple O2 sensors.

My type 1 is fast approaching 50K. Almost time for a valve job and new pistons and cylinders. Oil pressure is awesome, as is end play, so the bottom end is good. Before you tell me I'm wrong, do some research on the subject. Stroker and 94mm bore and LOTS of abuse. Yes, it's time.

Danny I would do some serious reading on the Atom as it seems the simplicity of having only two sensors makes set up and future diagnosisDX much much easier. It looks like it logs everything as well not like the stock ecu

Lastly if my stock ecu gives me any more issues I will go there but first my plan is ecutek tune then instead of replacing MAF air fuel and EGR 

i will move to atom like the spyder guy did in montreal 



I like the Megasquirt/Microsquirt just fine. It will use a TPS, MAP, IAT, CHTemp, crank VR and WBO2. Maybe I'm forgetting something but possibly a cam position sensor as well.

Remember, I'm doing a type1 while you are Subaru. I'd stick with the stock ECU on your car.

If the ECU only has two sensors, I'm sorry, but it is not enough for good warmup, mixture control, and driveability. Ask Lenny, he had the SDS and could never get it to run right. It was either too rich or too lean, never just right. That had head temp, IAT, TPS, MAP, and crank position. He ran open loop. But honestly, the SDS is meant for steady state. It's PERFECT for airplanes.

 This discussion is becoming interesting especially with all the abbreviations it reminds me of some guy on the lists Fam Name  


It would be really nice to be able to try some of these ECUs before committing to them you can easily drop 3K with a full conversion and tuning etc. just saying

I think it would be incredibly cool if, as a group, we settled on one particular system, like a Mega/Microsquirt or something, someone came up with a tailored retro-fit kit for any air cooled; 1,600 up to a 2,332 and could make the kits available. Two versions, single TB and 4 separate TB's would be perfect.  It might be a big-ish investment once, but would make these cars so much more civilized to drive.

@Stan Galat LachutePerformance in Brownsburg Quebec is the Rally racing tech, the owner won all kinds of rallies. English site.... this is the site that they sell product into the USA,  this is the original site where they do engines and run a tech shop, rebuilding all sorts of engines...   

If you can read french on the news area the owner Julien is still actively racing and placed third in the time trials with a Subie LP400 they call it ... crazy horsepower track car.  The whole speed shop started with his racing career and they now produce all sorts of products for Subies.  So if @Bob: IM S6 wants that winged machine of his to fly he can opt to go from 300hp to 600hp and hang on.  

Gordon, I think the variables with what you’re talking about would be too great to be feasible. It’s a cool idea, but there are just too many divergent branches on this particular tree for one or two packages to work well on any of them. I think it would end up being one size fits none.

However, I think the world could be ready for turnkey EFI Type-1, if the price were right. I think the only way it would really work out as if it were a fully dressed engine. A 2110 with a W120 and Panchitos with a 1-1/2” sidewinder would probably be “just right” for 95% of the people out there who would be interested.

The problem is, it would probably cost north of $12,000, and I think the market would be pretty slim/non-existent .

The stock ECU works just fine in early-mid 90s subarus whether bone stock, cammed or embiggened Frankenmotor style. Run all the sensors, and an intake and/or header give no trouble, as the stock map will adjust air/fuel ratios as needed. The stock unit also gives good idle (so long as the idle-air control valve and the vehicle speed sensor are good). If you get all the wiring and fiddly sensors andplugs and whatnot out of the donor car it’s the efficient way to get a reliable 140 (stock 2.2)—185 (cammed Franken 2.5) hp at 5500 rpm, with easy revs to the limiter. Downside: the 1995 ecu limits you to 6000. All other years are higher.

Thank You for all the positive comments and likes. I know what most of the nomenclature is that you guys have been talking about except for MS. What is MS ??  Also John at out front said that my engine warm-up idle is now resolved with something he did to it and the Stinger ECU it comes with. Does this sound plausible ? Does anyone recommend any books on this subject or is there a website with a lot of basic info I could read up on ?...........................Bruce

I cannot have a technical conversation with this group about this particular topic.  But being an owner of an EJ25 equipped car I would like to make a comment.  The subaru engine is the future of the speedster/spyder replica.  I think its important to have a reliable easily adjustable ECU.  I know some will say that the stock ECU is the way to go with these cars.  But the stock ECU creates a detuned 165 hp.  These engines even naturally aspirated easily create 200 hp.  My 2003 spyder with its 165 hp DOHC 2.5L suby was nice.  My current 200 hp EJ25 SOHC spyder is breathtaking.  The stinger ECU works great after the car is warmed up but it does stall easily before its up to temperature.  Type 1 and Type 4 engines will continue to get more expensive and subies will remain dirt cheap.  And I'm sorry to say that the folks that can work on air cooled engines will get fewer.  I can tell you that my millennial sons love my car.  And I can see them buying a P replica some day.  But it would NEVER be an air cooled engine.  The future is water cooled.  And there needs to be a company out there that can develop a nice ECU.  The demand will increase.

I am having my Fiberfab Speedster Converted to Suby  power by Special Edition. I like their approach. The use a Ej253 engine from a 2007 Imprezza. This engine has the variable valve lift and a stock 173HP. They buy a donor car to get the ECU heads and other engine accessories. They buy a brand new short block from Subaru. They send the ecu and wiring harness out for rebuild and modification. The heads are rebuilt. They set the car up using the stock ECU, air box, MAF and drive by wire. The end result is a dependable engine that starts up like it was meant to from the factory, drives and performs smooth and flawlessly. The 173HP (probably more because of running an A-1 header less CAT.) is going to be plenty for my needs. It takes a majorly tricked out Type 1 to deliver the same seat of the pants feel. The difference is the type 1 built to this power level is prone to over heating and can break easy. (Always worrying while driving) The Subaru built to stock specs running a stock ECU is well under it's potential and in the safe zone ready to deliver 100,000 miles of happy motoring.  So, I am not going to screw the pooch and soup up the Suby when it is better off stock. Carey has convinced me of this.  My humble experience and opinion.  My conversion had its first start up 1 am Sat. morning. It didn't have the MAF hooked up yet but still is a thing of beauty. Look how smooth the engine runs, it doesn't rock or vibrate at all.


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Speedster Subaru conversion first engine start 9-15-18


FYI, almost all Subaru tuning shops tune Subaru engines that use the stock ECU.  There are dozens of them throughout the US with 2 or 3 different types of dynos.  In my opinion, there is no need for a Stinger or other aftermarket ECU, especially if the builder is using a donor car with complete engine.  

It is common for a Subi tuner to almost double the HP on a stock EJ engine with add-on parts and not touch the bottom end.  Pretty wild, eh?  Not many platforms can make the same claim.

The newer than 2007 stock ECU causes trouble because they require all the inputs from sensors we don't use in the conversion to be present before the car will run. I hear they have some ways of making it work like having the stock gage cluster hooked up and hidden in the front trunk area as some SAS cars or a conversion box to hook inline that have varied reviews. This is the reason Special Edition only uses 2007 donor cars if they can help it. The 2007 is new enough the have the variable cam lift engine that puts out 173HP as opposed the 165hp that the earlier 2.5 liter engines offered. This may be a reason for after market ECU's.

550 Phil posted:

 Type 1 and Type 4 engines will continue to get more expensive and subies will remain dirt cheap.  And I'm sorry to say that the folks that can work on air cooled engines will get fewer.  I can tell you that my millennial sons love my car.  And I can see them buying a P replica some day.  But it would NEVER be an air cooled engine.  The future is water cooled.

Jim Kelly posted:

It is common for a Subi tuner to almost double the HP on a stock EJ engine with add-on parts and not touch the bottom end.  Pretty wild, eh?  Not many platforms can make the same claim.

 Phil's statements are irrefutable facts. As much as I love the air-cooled engine, it's a dead end. I envision a time coming VERY soon when nobody will order a $35K car with a glorified lawnmower engine. I think it's amazing that they can be made to make 200 hp, but that's really kind've a yawner in today's world. A Subaru can make SCADS more power for pennies on the dollar.

And Jim's statement regarding the bottom end of a Subaru EJ engine is something very, very important. No matter how much a guy spends, the VW bottom end is rickety. I'm fully shuffle-pinned, have a forged, welded, counterweighted crank, H-rods, 911 piston squirters, etc. I threw everything I could think of at it, and it'll never, ever be even half as robust as that EJ short-block.

I'm sure you can get more hp out of a suby engine without touching the ECU but why would you bother.  Its much cheaper to just alter the ECU program.  Anyone running a stock suby ECU will see no difference in 87 and 93 octane.  Why?  You've done nothing to the engine compression.  But alter the fuel mixture, air intake and compression of the engine and you can take advantage of the 93 octane gas. 

I put a larger cam in my VW/Audi IM, reprogrammed the ECU, changed to premium fuel and my car was noticeably faster.   

My daily driver is an Audi A3.  Its 220 hp.  An Audi A4 is 250 hp.  What is the difference in these engines?  Nothing!  Only the ECU programming.  I can't wait for my car to go off warranty.  When it does I'm going to get the ECU reflashed by APR and it will magically be 300 hp.  Just with computer reprogramming.  

Like I said before, my previous Spyder had a stock ECU.  It was very nice.  But it was not stupid fast.  Maybe stupid fast is a bad idea.  Just call me stupid.

These engines have SO much potential and in stock form they are detuned by Subaru for reliability.  Sure they might benefit from better cams and head porting (like my car) but the key is ECU reprogramming.  Its the difference between YES and HELL YES.  Trust me I've owned both.

My car has a 1776 cubic inch air cooled is trouble free ….if I want to go fast, I have cars that will do that......I ordered this car to replicate the original 356 not only in appearance but in performance….and to mow the lawn... 

I been to a lot of car shows where there is a lot of VW stuff and it's "YAWN" for me anymore. Nearly all are weber carb'd and many variations pretty things attached. They sound the same, look the same, probably cost about the same and are pretty much fun to drive. But...They are old and done over and over. I want to get out of that rut now. Greg says he'll be ready to start on a Spyderfor me next Spring. He thinks he will be ready to build me a Roller with a Sub trans and IRS. Suby engine of course. I'm pretty excited about that ! I'm pretty excited about getting into all this electronic stuff too.

You all are right about the BEEF in the bottom end too !!  FIVE...count them... FIVE Main bearings !  Installed in an aluminum vault for a crankcase !  The flat six cyl. has SEVEN main bearings. It's only 1.5 inches longer than the 4 cyl !  I have not seen such a compact and strong piece of engineering like this. (not that I have looked a lot) After taking a close look I like what I see.  7500 rpm occasionally should be feasible.

Hats off to all of you that have taken the leap already !!  I am now paying more attention to your particular posts on your Suby experiences...........Bruce

PS. Here's a nice Spiny Lobster I bagged down in Mexico a couple years ago. 12 lbs and ready for the pot !  


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