Impreza build + STI engine...worth it?

[shinn497]

I'm wondering if it would be more impressive to get a DIRT cheap impreza donor and then spend all the money on a nice EJ257/EJ207.

I used to think that we would need to buy extra exhaust pieces, but I realized these would come with the kit (I think you would need a modified exhaust with a twin scroll however).

Would there be any other difficulties. The only thing I'm seeing is the transmission. Then of course the question would then be is tuning a wrx to 300bhp more expensive than upgrading an impreza transmission...

I've heard 500-1000$ for a NA donor + 4000 for the sti engine. With 2000-4000 for transmission upgrades. vs

5000$ for a wrx donor + 4000$ on mods to get it to 300 bhp.

It seems comparable, however the former gets you an sti engine with more upgrade potential or a JDM sti engine with all the goodies.

chime in I know I'm missing something...

[Etos]

The prices are waaaay off. A WRX trans is in the range of $300 for much older ones to 800-1000 for newer ones. Even an STi trans is only in the 3000 range.

If you get the engine/trans separately, it's not worth buying a donor car for the other bits. Most of them can be fund dirt cheap at junk yards and still pretty cheap on nasioc as people don't buy used OEM parts for much. You can even get an STi long block for about $2500-4000 depending on what's done to it.

http://forums.nasioc.com/forums/forumdisplay.php?f=149 For engines

http://forums.nasioc.com/forums/forumdisplay.php?f=151 for transmissions

I am actually going down this route myself as I have a spare STi long block, ECU, turbo, exhaust, intercooler, brembo brakes and other small bits here and there. All I'll need are transmission, control arms, rear brakes, hubs, axles and wheels. It's not worth getting a donor to me just to get all that which I can find very easily at a junk yard for dirt cheap.

Edit:
Right on the first page of the drivetrain forum:
http://forums.nasioc.com/forums/showthread.php?t=2313994
Entire 06 WRX tranny set for $850 which includes tranny, flywheel, clutch, rear diff, axles and hubs. That $850 can be brought down by taking out the flywheel, clutch, driveshaft, front axles and rear diff to probably $700-750.

[bugeye_fever]

I don't think it'd be a bad idea, but there are parts I wouldn't want to use from the cheap impreza donor, namely the suspension and brakes. But when you really think about it, nobody knows whether NA impreza brakes won't work well on this car. It seems the more I read the more it seems some are fixing problems that don't exist yet. Brakes that are decent on a 3000lb car ought to work great on one thats 1800. Also, I'm not sure you'd have to spend a lot on a "nice" EJ. Either of those you mentioned are way more than capable of putting out 300 at the crank with just intake/exhaust/tune on the stock turbo and fuel system, and since the intake and exhaust that will come with the kit should be pretty good(at least better than stock subie) it should just come down to the tune. I think the hardest thing about this whole kit will be putting the power to the ground. If my wrx can spin 4 slicks with 215hp/275ftlb the 818 with 300 will be able to smoke tires all day long.

Guess what I'm getting at is the suspension pieces need to be sourced carefully, because no matter when else you do to the car, if the suspension geometry isn't good. It'll never handle right. After that, why not source everything else from that dirt cheap impreza, even the engine. Once you've put miles on it and seen what items need to be improved, then find that nice EJ or upgraded brakes. I also think that at the 300 crank hp level, you won't need to upgrade the gears the wrx 5 speed, as long as your not driving like a 16 year old tard, lol. The only upgrade I'd entertain prior to actually driving the car is an lsd for the front diff.

...I think i got a little off topic there. Basically, the 2.5 turbo with any of the stock vf series turbos and the jdm 207 are only going to require a tune to get to the power level your talking about. The 205 with a TD04 turbo is the only one that will require upgrading the turbo to get there.

[shinn497]

The prices are waaaay off. A WRX trans is in the range of $300 for much older ones to 800-1000 for newer ones. Even an STi trans is only in the 3000 range.

If you get the engine/trans separately, it's not worth buying a donor car for the other bits. Most of them can be fund dirt cheap at junk yards and still pretty cheap on nasioc as people don't buy used OEM parts for much. You can even get an STi long block for about $2500-4000 depending on what's done to it.

http://forums.nasioc.com/forums/forumdisplay.php?f=149 For engines

http://forums.nasioc.com/forums/forumdisplay.php?f=151 for transmissions

I am actually going down this route myself as I have a spare STi long block, ECU, turbo, exhaust, intercooler, brembo brakes and other small bits here and there. All I'll need are transmission, control arms, rear brakes, hubs, axles and wheels. It's not worth getting a donor to me just to get all that which I can find very easily at a junk yard for dirt cheap.

Edit:
Right on the first page of the drivetrain forum:
http://forums.nasioc.com/forums/showthread.php?t=2313994
Entire 06 WRX tranny set for $850 which includes tranny, flywheel, clutch, rear diff, axles and hubs. That $850 can be brought down by taking out the flywheel, clutch, driveshaft, front axles and rear diff to probably $700-750.

Hmmm my price estimates for the tranny were based on shopping for JDM Sti engines. Sourcing one with a tranny almost doubles the price.

TBH, I'd rather source a donor than dig through a junkyard, best to have all the parts there. FFR stated they will use a LOT from the donor. IT is not the big parts I'm worried about moresoe the little ones.

FFR is going to be supplying Koni shocks and upper control arms/multi links with the kit standard so I think the suspension will be covered. No need to worry about bracing since this chasis will be their stiffest one yet...and this is comparable to their purpose built race cars!

Still wondering about a NA tranny attached to a STI engine. The non turbo trannies are different, so I'm assuming they are weaker. I should say that STI trannies are NOT wanted, so a tranny upgrade would be WRX + stronger gear sets or just the stronger gears into the NA tranny. The price for that was based on PPG sets. I hear legacy GT and STI gears are cheaper.

[Etos]

Hmmm my price estimates for the tranny were based on shopping for JDM Sti engines. Sourcing one with a tranny almost doubles the price.

TBH, I'd rather source a donor than dig through a junkyard, best to have all the parts there. FFR stated they will use a LOT from the donor. IT is not the big parts I'm worried about moresoe the little ones.

FFR is going to be supplying Koni shocks and upper control arms/multi links with the kit standard so I think the suspension will be covered. No need to worry about bracing since this chasis will be their stiffest one yet...and this is comparable to their purpose built race cars!

Still wondering about a NA tranny attached to a STI engine. The non turbo trannies are different, so I'm assuming they are weaker. I should say that STI trannies are NOT wanted, so a tranny upgrade would be WRX + stronger gear sets or just the stronger gears into the NA tranny. The price for that was based on PPG sets. I hear legacy GT and STI gears are cheaper.

You really don't want to mess with JDM engines. Alot are different from sensors, wiring harness, ECU, ability to tune that ECU, communications with other computers such as the drivetrain etc. All these things are very hard to come by here in the US. So that means you'll be waiting on parts for upto months, paying almost double their worth due to the yen to dollar and paying very expensive shipping. There isn't ANYTHING special about going JDM other then being able to say I have JDM har har. You are 10x better off just getting a USDM engine, figuring out how you want that engine to work and moving that direction. Subaru engines are highly modable from using 2.0 heads on 2.5 blocks, 2.0 cranks on 2.5 blocks(effectively giving you a 2.34 destroked engine which is AWESOME). Also you pretty much should double the milage from JDM as they are almost always city miles and US engines tend to be alot of highway most of the time.

FFR supplies the UPPER control arms, they are re-using the lower control arms in the front and rear. STis have alum and WRX have steel(cept the front from an 06). So yes you still need to worry about control arms. Also if they plan on using swaybars you'll need those too. I don't know if they plan on reusing the trailing arm in the rear or not either. Those little parts you are worrying about, I wouldn't. What else are they going to reuse that you can't find for cheap on nasioc or a junk yard? Factory headers are dirt cheap and believe it or not- are very very good. They are extremely thick and do not create a raspy sound. FFR is NOT going to supply their own header/up pipe and I even doubt they are making their own downpipe. So going with an NA impreza you STILL need to get those as well as a turbo which guess what- you need to get from nasioc or a junk yard or buy new if you get an NA donor. Steering racks are dirt cheap too. Steel control arms, yup dirt cheap. Standard calipers are dirt cheap brand new OEM. Don't forget that an NA donor WILL NOT have most of the little stuff you need like again exhaust, wiring harness, injectors, coil packs, TGVs(that's what the injectors stick into), intercooler, turbo, turbo inlet hose, radiator, throttle body(you have to make sure you match the ECU to DBW or DBC), and so many more things you just won't find from an NA donor when trying to use an STi engine. I just do not see the need to buy an engine/tranny then a donor ontop of that, let alone an NA donor that the only thing of value you can source are the lower control arms.

I don't know much about the NA trannys. I know the gearing is different from WRX so maybe the case is the same with different gears? Probably. Also you can't swap STi gears into a NA/WRX tranny as the STi gears are about double the width so they will not fit. Going PPG is expensive and overkill for an 818. When I say expensive I mean the gears alone are going to cost more then a full STi tranny swap set, that doesn't include a shop putting them in. Unless you are very good with trannys and are experienced with it- it's not something you want to under take. Just get an 06+ tranny, swap out the diff, brace the case and call it a day. I even gave you a link to an 06 tranny which includes front+rear hubs, axles and flywheel/clutch(though you should probably replace those 2) for $850, less then 1/4 you're expected cost.

I'm even going a step further again:

http://forums.nasioc.com/forums/showthread.php?t=2326082

That right there is a short block with forged internals, JE forged pistons(some of the best pistons in the world), balanced crank, eagle rods, ACL bearings and ARP headstuds for $2550. Another $700 gets you a set of 05 STi B25 heads with BC springs/retainers from the same seller. So $3250+ Shipping(US shipping at that) will get you a FAR FAR better BRAND NEW 0 MILES BUILT LONG BLOCK that will give you 1/4 the headsaches, be compatible with anything you can find here and is capable of making 500hp easy. Why in hells name would you still want a JDM engine with 100k miles(50k JDM = 50k city, city is FAR more stressful then highway) that will NOT work with anything USDM, not be any better then a USDM engine. And guess what- that was 1 engine from the first page. I didn't even bother scrolling down. Deals like these are found ALL the time on nasioc.

[shinn497]

What if I wanted avsc and twin scroll? I've found several JDM motors (http://www.ebay.com/itm/JDM-SUBARU-IMPREZA-WRX-STI-VERSION-8-EJ20-TURBO-ENGINE-MOTOR-/170822109992?pt=Motors_Car_Truck_Parts_Accessories&hash=item27c5ca8b28&vxp=mtr) that come with everything, turbo, intercooler, ecu, manifolds, for 4k. Mind you that turbo is vf37. Also from what I hear the Ej207 is much more smooth in comparison to a ej257 and many would much rather drive the former over the latter. Trust me I'm not going JDM for JDM's sake, I've researched this. Despite being a huge japanophile (lived there speak the language), I never got caught up into people rocking yellow headlights and soshinoya stickers.

The way you make it sound, if you can source a good trany and live near a junkyard having a donor is unnecessary.

[Etos]

What if I wanted avsc and twin scroll? I've found several JDM motors (http://www.ebay.com/itm/JDM-SUBARU-IMPREZA-WRX-STI-VERSION-8-EJ20-TURBO-ENGINE-MOTOR-/170822109992?pt=Motors_Car_Truck_Parts_Accessories&hash=item27c5ca8b28&vxp=mtr) that come with everything, turbo, intercooler, ecu, manifolds, for 4k. Mind you that turbo is vf37. Also from what I hear the Ej207 is much more smooth in comparison to a ej257 and many would much rather drive the former over the latter. Trust me I'm not going JDM for JDM's sake, I've researched this. Despite being a huge japanophile (lived there speak the language), I never got caught up into people rocking yellow headlights and soshinoya stickers.

The way you make it sound, if you can source a good trany and live near a junkyard having a donor is unnecessary.

STi B25 heads have AVCS on the intake. Any turbo EJ engine can use a twinscroll header.

I checked that ebay link. Well I don't know what to make of that TBH. $3700 for a complete engine setup with long block, headers, turbo, tmic from japan no less makes no sense. Dollar to yen is horrible, shipping is expensive so I have no clue how they could sell a kit like that at that price. If you do bite the bullet and end up with it, and it had no issues it sure is a sweet deal.

But I still don't see the point of getting an NA donor? The only thing you can even use from it are the lower control arms, calipers and wheel hubs.

[shinn497]

"Hi there,

A V8 complete motor with turbo, downpipe, ECU and harness with all accessories shipped to CA will cost $4250.00.

I getting a shipment in 3 weeks. I have no idea if I will be getting any spec cs. "

message I got from a VENDOR AT nasioc. I think that is comparable to the previous engine that you posted since it was sans accessories. Plus with a full JDM engine you don't to worry about building it. Honestly before I found out about the perks of an ej207 I was not even considering an STI engine since a donor sti is not worth it...

You should check the parts list FFR posted for the 818:

• Front spindles with full brakes and front lower control arms
• Rear spindles with brakes and parking brake
• Steering rack, tie rod ends, and upper steering column assembly
• Pedal box and throttle
• Master cylinder and brake booster, and clutch master cylinder
• Engine with turbo and intercooler (if WRX model)
• Transmission
• Rear lower control arms, toe links, and CV joints
• Seats and gauge pod
• Fuel pump
• Radiator
• Wheels and tires

I should note that it doesn't make any mention of exhaust, BUT it is also not mentioned on what you need. This is why I would want a donor. I am sure there are miscellaneous things that will come up. Driving back and forth to the junkyard would seem like a hassle. Plus there is the fun of ripping a car apart in your garage! apparently NA donors can be had for cheaper. And you can part out what you don't need. Some people have broken even doing this (some haven't). I would actually consider buying a donor vs dumpster diving to both be viable options. The point is your NOT buying a more expensive WRX.

MY goal is STI power/potential with least hassle/cost.

You do make a good point though. I'm begininng to think that sti power one would want bigger fat tires and that is one less thing to take from the impreza.

EDIT: another reason for sourcing a donor is registration. A ho hum NA engine should pass smog easy but abuilt engine won't. JDMS WILL but you have to do a lot to it and run the stock ecu which causes knock.

[Etos]

You should check the parts list FFR posted for the 818:

• Front spindles with full brakes and front lower control arms can be sourced from an NA
• Rear spindles with brakes and parking brake can be sourced from an NA
• Steering rack, tie rod ends, and upper steering column assembly can be sourced from an NA but longer ratio
• Pedal box and throttle can be sourced from an NA since you are using a DBC engine
• Master cylinder and brake booster, and clutch master cylinder I believe STi uses different brake booster and clutch master then NA though not sure
• Engine with turbo and intercooler (if WRX model) you got that covered
• Transmission can NOT be sourced from an NA for your engine, as well as clutch, PP and flywheel
• Rear lower control arms, toe links, and CV joints can be sourced from an NA
• Seats and gauge pod can be sourced from an NA, but do you really want NA seats and the NA gauge pod? The seats do a fair job of holding you in but do not look even decent and the gauge pod has MPH in the middle and RPM to the side- may not work with your JDM ECU as well
• Fuel pump can NOT be sourced from an NA
• Radiator can NOT be sourced from an NA since it won't do a good enough job to cool an STi motor
• Wheels and tires can be sourced from an NA but are tiny



There just isn't much you can take from an NA donor if you plan to use an STi engine. If you were planning on using an NA engine then everything can be used but the STi engine changes everything.

[StatGSR]

^ um you can totally use an NA trans with an sti engine. Just have to use the NA clutch and flywheel. Any ej trans will bolt up to any ej engine.

[Bacon]

You really don't want to mess with JDM engines. Alot are different from sensors, wiring harness, ECU, ability to tune that ECU,...
The jdm STi engines are indeed very different than the usdm STi, but are actually very close to the 02-05 usdm WRX. The only difference in the wiring is that the jdm doesn't have tumble valves but has AVCS. To swap a jdm sti into a usdm wrx is the easiest swap, only 4 wires to move! And most if not all sensors are the same as the usdm wrx.

I had a jdm sti V8 in my 99 RS and I'd choose this engine again over a usdm sti anytime!

[BrandonDrums]

4k to get a WRX to 300 hp is WAY off. Basically, for an 06/07 wrx donor all you'll need is a tune to get to 300 at the crank, if you want 300 at the wheels you just need a turbo and a tune. The injectors and fuel pump are the same which just leaves the intercooler which isn't 100% needed to get 300 whp on a 2.5L.

On a 2.0L wrx (02-05) you'll need a bigger intercooler, STI or larger injectors, fuel pump and turbo then tune (assuming on an 818 which will already have a higher flow exhaust). You can get used STI injectors for 150, TMIC for 200, VF39 for 300 and the fuel pump for 100. At most with the tune your looking at 1k gross to get 300 whp and you can still sell the old parts for about 300 total.

Now, if you want AVCS to work on a N/A subaru Donor you're going to have to have an ECU that can control the AVCS and that will require swapping harnesses too. Sourcing a complete harness and ECU alone is a pretty penny, perhaps not a terrible job to swap for an 818 since everything will be out already but it's a PITA. You're much better off with a donor that already has AVCS if you're going to be using an AVCS engine.

AVCS aside, a N/A Subaru ECU doesn't have any boost control tables enabled nor the electronic leads to a boost control solenoid. You'd spend forever trying to wire up the boost control unit or will have to add an aftermarket stand-alone boost control unit or do a manual boost controller which works but leaves a lot to be desired. Yet another issue to deal with.

I have an EJ257 swapped into my 05 WRX with the AVCS disabled and frankly the AVCS makes little to no difference, on the stock tune the AVCS has 0 offset by 3k rpm. It only translates to about 10 ft-lb of additional torque below 3k rpm and you get that by swapping the exhaust. The newer engines have variable valve timing on the intake and exhaust which makes a bigger difference though.

My .02, if you want a built engine just by a WRX donor with a blown one and swap from there. Messing with ECU's and re-configuring wiring harnesses isn't going to save you money in this scenario. That's something you pay a premium for if you're swapping into an older Subaru Chassis, for example.

[Twinspool]

For those of us in utopian-occupied CA there's no way to run a JDM engine aside from SB100 right?

I've quite nearly decided on a plain-ol 2.5L WRX drivetrain. Rancho Cordova is a mecca for salvage yards.

[Nuul]

4k to get a WRX to 300 hp is WAY off. Basically, for an 06/07 wrx donor all you'll need is a tune to get to 300 at the crank, if you want 300 at the wheels you just need a turbo and a tune. The injectors and fuel pump are the same which just leaves the intercooler which isn't 100% needed to get 300 whp on a 2.5L.

On a 2.0L wrx (02-05) you'll need a bigger intercooler, STI or larger injectors, fuel pump and turbo then tune (assuming on an 818 which will already have a higher flow exhaust). You can get used STI injectors for 150, TMIC for 200, VF39 for 300 and the fuel pump for 100. At most with the tune your looking at 1k gross to get 300 whp and you can still sell the old parts for about 300 total.

I would add STI cams and a TGV deletes to that list. $100 for the cams and nearly free for the TGV delete if you're comfortable drilling them yourself. So total parts list and tune we're looking at $1500 tops for ~350WHP.

[shinn497]

For those of us in utopian-occupied CA there's no way to run a JDM engine aside from SB100 right?

I've quite nearly decided on a plain-ol 2.5L WRX drivetrain. Rancho Cordova is a mecca for salvage yards.

HEy I'm in CA what is wrong with obtaining an SB100? I don't mind camping out that one magical day.



^ um you can totally use an NA trans with an sti engine. Just have to use the NA clutch and flywheel. Any ej trans will bolt up to any ej engine.

It is less if the tranny will fit and more if it will break. Though that was discussed at length in another thread.

@brandondrums

300$ for a VF39 0.o I guess that is because that is a STI turbo. How much hp can that run? I expect at most 350whp.

[bugeye_fever]

A vf39 won't get you 350 at the wheels, maxed out on pump its more like 330ish on an STI. Maybe it could be more on an 818 with less drivetrain loss, but I really don't see a point with shooting at a certain whp number. Also there's one thing you could use from the NA donor that i think gets missed, and that is the intake manifold. It's already tvg-less and some believe flows better than the sti intake, you'll have to run top feed injectors though which would be a problem on the earlier years of EJ257's if you got a complete engine to swap in. But I think top feeds are the way to go.

[NonProfit]

I really don't see a point with shooting at a certain whp number.

I agree. Obviously, there is a whole lot more to driveability than just power and weight, but using Wikipedia (http://en.wikipedia.org/wiki/Subaru_Impreza) and torquestats.com (http://www.torquestats.com/modified/index.php?pid=calculator) I came up with approximate performance times.

2.0 L 93 kW (126 PS; 125 hp) (GX)
RWD - 125bhp & 818kg
Power to Weight: 155 bhp/ton
0-60: 6.5
0-100: 20.1
60-100: 13.6
1/4 Mile ET: 15.29

2.5 L 123 kW (167 PS; 165 hp) H4 (2001–05)
RWD - 165bhp & 818kg
Power to Weight: 205 bhp/ton
0-60: 4.7
0-100: 14.2
60-100: 9.5
1/4 Mile ET: 13.82

2.5 L 129 kW (175 PS; 173 hp) H4 (2006–07)
RWD - 173bhp & 818kg
Power to Weight: 215 bhp/ton
0-60: 4.6
0-100: 13.5
60-100: 8.9
1/4 Mile ET: 13.61

2.0/2.5 L Turbo-charged 169 kW (230 PS; 227 hp) H4 (WRX 2002–07)
RWD - 227bhp & 818kg
Power to Weight: 282 bhp/ton
0-60: 4.2
0-100: 10.7
60-100: 6.5
1/4 Mile ET: 12.65

2.5 L Turbo-charged 224 kW (305 PS; 300 hp) H4 (WRX STi 2004–07)
RWD - 300bhp & 818kg
Power to Weight: 373 bhp/ton
0-60: 3.8
0-100: 8.8
60-100: 5.0
1/4 Mile ET: 11.99

350hp:
RWD - 350bhp & 818kg
Power to Weight: 435 bhp/ton
0-60: 3.5
0-100: 8.0
60-100: 4.5
1/4 Mile ET: 11.67

400hp:
RWD - 400bhp & 818kg
Power to Weight: 497 bhp/ton
0-60: 3.3
0-100: 7.5
60-100: 4.2
1/4 Mile ET: 11.43

If you're building a street car, the problem won't be lack of power, the problem will be crafting something that's more scary than fun.

[PhyrraM]

Don't forget when doing our internet maths that whatever an engine/turbo/tune/etc puts 'to the wheels' in an AWD Subaru is likely to be measurably greater 'to the wheels' on a 2WD 818.

Edit, already said. Should read to the bottom first. :o

[Nuul]

A vf39 won't get you 350 at the wheels, maxed out on pump its more like 330ish on an STI. Maybe it could be more on an 818 with less drivetrain loss, but I really don't see a point with shooting at a certain whp number. Also there's one thing you could use from the NA donor that i think gets missed, and that is the intake manifold. It's already tvg-less and some believe flows better than the sti intake, you'll have to run top feed injectors though which would be a problem on the earlier years of EJ257's if you got a complete engine to swap in. But I think top feeds are the way to go.

Good info, thanks. I wasn't aware of the vf39's limitations or about the NA intake being TGVless. Do you much about the vf34 by chance? That's what came on my donor car, I've been looking for its specs but not came up with much.

[shinn497]

For what it is worth, I don't think I would actually go for 350 whp. I did some calc's a while back and figured that 350 whp, taking into account drivetrain lossess and increases in efficiency due to it being 2wd would be equivalent to a ferrari enzo or some such nonsense ( around 400 bhp). I'd rather get used to that first before upgrading.

The second reason I posted this thread, besides wondering of a cheaper way to get an sti (especially JDM engine), is to figure out the potential of a NA build without a rediculous price. I could see myself starting NA and then upgrading as I get more used to the power.

[bugeye_fever]

I know the VF 34 is ball bearing, and i believe it is just slightly larger than the 39, I know a few guys who have swapped in the 34 on the ej205 and love it. With all honesty i think the jdm motor is they way to go if you want to end up turbocharged. The ej207 comes from the factory with a closed deck block, not semi closed like our 257 or open like the 205. It also has fully forged internals from the factory, and much better flowing heads. I also like it for the potential power band. You'll see many many tuned sti's with smaller turbo's(by that i mean smaller than a gt30) make a big slug of torque right off the bottom end. My own makes 275ftlbs at 3000rpm, which is amazing in a subie. That thats just gonna spin the tires on an 818. With the 207 you lose some of that bottom end torque, but gain the ability to rev to 8000+ rpm. Tuning with the jdm ecu would be difficult but if you've got the cash to import one from japan, might as well just put a standalone like an aem in it.

Me personally, I would like to rebuild my 257 with like a 9:1 compression ratio(it needs a rebuild anyway), rotrex supercharger at lower boost (10psi) and e-85. For the trans I'd use my wrx's, put a diff in it and see how long the gears last.

[Nuul]

With all honesty i think the jdm motor is they way to go if you want to end up turbocharged.

Agreed, the EJ207 is a beast. If money were no object though I'd be calling Dom at MPS and getting a 2.34L engine from them. Great low end punch and makes power allllll the way up to 9K. Perfect engine for the 818 in my opinion.

[shinn497]

Why is tuning with the jdm ecu difficult? I looked at other threads and found 4 tuners that work on JDM engines.

[bugeye_fever]

I recall someone saying it was, it very well may not be. But it is outside my knowledge base.

[BrandonDrums]

Why is tuning with the jdm ecu difficult? I looked at other threads and found 4 tuners that work on JDM engines.


I don't think there's any difference tuning a JDM engine to my knowledge. I actually have JDM injectors from a V7 Sti pulled the values from an OEM rom just to be sure and poked around a bit to see the differences. The ECU tables are actually more or less the same as US ECU's and have only about the same variation in the different controls and tables as there are between different model year US Subarus. I pulled a lot of base values for my tune from a USDM 05 STI and there's as many differences between my wrx and the sti maps than between any tubro JDM and USDM maps.

See for yourself, go download http://www.romraider.com/ it's free.

Download the latest ECU definitions for Romraider so you can open ECU map files
http://www.romraider.com/forum/topic360.html

and then download a couple OEM ECU maps to compare
http://www.romraider.com/forum/viewtopic.php?f=35&t=7591

Not only that, but JDM EJ motors are still EJ series motors. They have some nicer parts and different specs here and there but they are still internal combustion engines that use pistons rather than rotors or turbines to create power so all the otto cycle principles apply. Variable valve timing is something else to consider for sure but even USDM engines have that. I can't help with tuning AVCS but the principle isn't hard to digest, you just adjust the opening of the valves to correspond with the firing of the injectors and the speed of the intake charge to maximize the air swallowed. How that translates into degrees of offset though is something you'll have to research.

I will say the tuning styles are very different. JDM tunes are very rich but run more timing than US models from the factory. I guess lower quality gasoline and more steady/cooler temperatures would get someone to tune that way. Regardless, I still see no reason to run AFR into the 8's on a factory tune if on any tune. That's just horrible for the car, the cat and the air.

Don't be fooled by all the crazy random variances in timing and fueling across load and RPM. From the factory it seems they do that based on large-scale statistical data logs where they test the engines over all possible weather and fuel conditions over an entire market and find all the knock thresholds over millions of virtual miles. Then they jostle those numbers between base and additive tables to make them look more random than they are in effort to perpetuate their obfuscation of consumer knowledge. After spending countless hours logging and tuning my rex over the last few years that's my crazy conspiracy theory about how wacky factory tunes look. There's really absolutely no sense in making an engine which should behave relatively linearly have non-linear inputs unless you're trying to confuse people who like to tinker on their cars under warranty

...anywho when looking through the tables, especially for timing, just add the base timing with the timing advance max tables to see what the final applied values are to compare different tunes.

I feel an itch to write an intro to tuning with respect to the Subaru ECU systems but I'll stop here for now.

I can't wait to see the plethora of boost issue threads we'll have when people start building these cars lol.

[shinn497]

Nice post brandon. In the spirit of DIY that a build such as the 818 would have I encourage you to write such a thread.

As I understand the AVCS on USDM engines is less sophisticated and only on the newer moedels.

[Nuul]

There's really absolutely no sense in making an engine which should behave relatively linearly have non-linear inputs unless you're trying to confuse people who like to tinker on their cars under warranty

That wouldn't surprise me in the least. :)

Good post by the way. Once the kit gets released and people start bolting these things together there's going to be need for a guy who knows the ins and outs of open source tuning - I see a sticky in your future lol.

[Evan78]

Why is tuning with the jdm ecu difficult? I looked at other threads and found 4 tuners that work on JDM engines.Depends on what you're using to flash the ECU. I'm not very familiar with open source, but I don't think the Cobb AccessPorts sold in the US work with JDM ECUs.

[BrandonDrums]

That wouldn't surprise me in the least. :)

Good post by the way. Once the kit gets released and people start bolting these things together there's going to be need for a guy who knows the ins and outs of open source tuning - I see a sticky in your future lol.

Thanks! I have never made it to real sticky status but that's over on NASIOC where I'm by no means the most experienced person on anything. I'll certainly try to get something together when the time comes!

Just to elaborate more on my logic to why the OEM tunes on Subaru's look so wacky, look at the difference between the base timing tables for an 04 STI which was the first STI in the US market a good bit before the explosion of aftermarket modding and opensource tuning vs. an 08 WRX. Both are 32 bit throttle by wire EJ25X engines with intake only AVCS. They could be tuned identically with the wrx running less boost than the STI and the numbers and fuel economy values would be the same.

Here's the 04 STI's tables, notice there are 2 tables, A and B aka a primary and a fallback. Note both tables are linear and they both share the same values.
http://i996.photobucket.com/albums/af89/BrandondrumsWRX/04STITimingBase.png

Here's the 08 WRX's tables. There are Cruise and Non-Cruise tables then AVCS related cruise and non-cruise tables with several other tables determining which table is used based on who knows what. Any aftermarket tuner would make all maps the same and just get the values correct the first time not unlike the 04 sti tune.
http://i996.photobucket.com/albums/af89/BrandondrumsWRX/08basetiming.png

[Oppenheimer]

Isn't it more likely that they were chasing better mileage and/or emissions with those changes? Or trying to make sure the car works in all environments, all conditions? A tuner has the advantage that he is trying to build a map for one person, that is going to use their car in one way, in one place, with one set of environmental variables and one set of mileage and emissions goals. An OEM has to build for all conceivable drivers, in all conceivable environments, with strict governmental regs.

Those maps could even be a result of trying to tune for the EPA mileage and our emissions test sequences. They know that those tests invovle driving at specific speeds, shifting at prescribed points. Maybe they tuned for those, knowing that those interested in real performance would map their own tunes anyway. Maybe they aren't trying to work against tuners here, but with them. Tune just for the tests, just for the non-performance oriented drivers, so that they can keep all the cool hardware intact, knowing that tuners would take full advantage of that HW with their custom tunes.

[BrandonDrums]

Isn't it more likely that they were chasing better mileage and/or emissions with those changes? Or trying to make sure the car works in all environments, all conditions? A tuner has the advantage that he is trying to build a map for one person, that is going to use their car in one way, in one place, with one set of environmental variables and one set of mileage and emissions goals. An OEM has to build for all conceivable drivers, in all conceivable environments, with strict governmental regs.

Those maps could even be a result of trying to tune for the EPA mileage and our emissions test sequences. They know that those tests invovle driving at specific speeds, shifting at prescribed points. Maybe they tuned for those, knowing that those interested in real performance would map their own tunes anyway. Maybe they aren't trying to work against tuners here, but with them. Tune just for the tests, just for the non-performance oriented drivers, so that they can keep all the cool hardware intact, knowing that tuners would take full advantage of that HW with their custom tunes.

Well, they might be trying to eek out more MPG but they've failed, the STI has had the same EPA fuel economy ratings dating back to 2004 in the US along with close to the same power output ratings.

Aside from that, fuel economy is improved more by running the engine with higher timing and closer to STOIC AFRs. The latter is done by keeping the cars running in closed loop fueling more which is certainly something that has taken place but arguably is responsible for a notable uptick in ring failures from 08-10. I'll try to find some AFR logs from the bad years but those tunes would keep the car running in closed loop until 4k rpm even at full throttle and 12 lbs of boost.

I can keep going with more conspiracy theory evidence but just look at how silly the throttle by wire tables have gotten. I'm not even talking about the values but just the metrics on which they operate. The first DBW maps on subarus were just % pedal angle which directly corresponded to a % throttle opening. Now...well, now it's even crazier than this which is taken from an 08 wrx.

Stare at this all you want and try to figure out what the BENEFIT this system might provide lol...

http://i996.photobucket.com/albums/af89/BrandondrumsWRX/nutsothrottlemapping.png