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Old 07-01-2002, 05:13 PM   #1
Kevin Thomas
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Question SR20DET Injectors and Legacy ECU

I just recently bidded on some SR20DET injectors on Ebay that are 440cc. I've read here that the 2.2ltr OBS has 240cc injectors. I will have an Apex SAFC installed very soon. Also, yesterday I took out my Legacy 2.5ltr ECU because I just recently moved and finally (after a couple of years ) found my stock 2.2ltr OBS ECU that was lost. Lol!

Anyway, my question is that since I'll be going to injectors that are twice the size of my stock injectors and that I've read the SAFC only controls up to 50% more than stock, would the 2.5ltr Legacy ECU be better suited for the new 440cc injectors? I ask because the Legacy ECU is programmed for larger injectors anyway (I'm assuming the Legacy has larger injectors than an Impreza). The ECU is from a 1999 2.5ltr Legacy GT.

I just want to hear/read what some of the 'techies' here might have to say so I have a better insight to what I'm getting into.
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Old 07-01-2002, 05:32 PM   #2
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The S-AFC should be ok for fuel, but I'd question the timing issues. When you adjust the fuel by modifying the Airflow Sensor signal, you will be changing the load that the ECU sees, so it'll in turn change the timing it puts out as well.

Split Second has a unit that'll modify them both, but I'd say it'd be very near what I'd call a "programming nightmare" bouncing back & forth with adjustments. *shrug*
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Old 07-01-2002, 07:10 PM   #3
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Kevin,

First of all, you're going to have to be very careful about leaning out the fuel map. If not, you'll run so rich that you'll clog up the O2 sensors in mere hours of highway driving. You probably know about running too lean, so I won't go there. The 2.2L ECU tends to run much richer and goes into open loop much sooner than the 2.5L ECU, which does not help the situation.

(Warning: hair-brained observations from hundreds of highway miles to follow.) The 2.5L ECU also seems to be a lot smarter about doing a self-cleaning cycle or so once the front O2 sensor does get clogged up. I believe it uses the rear O2 sensor during this procedure. I think the 2.2L ECU also has a similar feature, but I could not readily duplicate it.

Another problem is the occasional backfiring when starting the car. The ECU's crank enrichments during engine starting ignores the MAF completely, which makes the S-AFC useless during this time. You'll get twice as much fuel as you'll need - great when it's really cold out, but annoying when the engine is even slightly warm. If it happens, just keep it cranking until it finally runs on its own. I predict that you can disconnect the MAF/S-AFC during cranking and it would not affect anything. On a related note, cold start enrichments will be thrown off, and the car may have slight driveability issues until the coolant temp sensor reaches operating temps and the ECU finally enters closed-loop mode.

The good news is that big injectors will work if you can put up with the fuel enrichment bugs. And for optimum adjustability, the S-AFC works better for leaning out large injectors than for adding fuel to stock injectors. If not for the odd self-cleaning feature of the 2.5L ECU and the extra 200 rpm redline, I'd say that it performs very similar to the 2.2L ECU, and used about the same S-AFC settings. I didn't notice any difference in ITC or J&S settings when switching between injectors and ECUs.

Maybe you'll get lucky and have none of these issues...

-WaC
Wayne

P.S. One day I'll just get a standalone.
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Old 07-02-2002, 08:14 AM   #4
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Kevin ~~ Good to "hear" from you. (You, too, Wayne.)

If you have a fuel pressure riser, don't use it with the larger injectors. The S-AFC should be able to reduce the fuel enough at normal fuel pressures, but it won't be able to if the fuel pressure is very high. Wayne has covered most of the other stuff.

On a slightly different note, you still tinkering with the OBS? I thought you had moved on to the XT6?

Steve
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Old 07-02-2002, 02:27 PM   #5
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Originally posted by SteveS
On a slightly different note, you still tinkering with the OBS? I thought you had moved on to the XT6?

Steve
Steve,

I must be going through a mid-life crisis or something. Seeing all these WRX's getting faster and faster is eating at me so I'm just spending all my $$$ on both cars. Ask Dave and Greg of RalliSpec what my plans on my XT6 are. I took it to them with a bunch of parts and now it's just a matter of leaving it with them for them to put all the parts together. Think RichL! Nice to 'hear' from you also.
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Old 07-02-2002, 02:50 PM   #6
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Kevin

If you do find the 440s are just too much, I'll be more than happy to swap my 370's with you. I'm only offering because I'm such a nice guy.....

Best of luck to you. Let's see, we now have three people with '97 wagons on this thread. Let's demand our own forum!

Jeff
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Old 07-02-2002, 08:48 PM   #7
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Default Make that 4

I also have an MY97 wagon. Turbo is in the basement waiting for me to finish up installing all the nessary things, hood and clutch. I was going to go the 2.5 ECU route as well but it seems you better off not.
Joshua
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Old 07-03-2002, 06:45 PM   #8
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Quote:
Kevin ~~ Good to "hear" from you. (You, too, Wayne.)

If you have a fuel pressure riser, don't use it with the larger injectors. The S-AFC should be able to reduce the fuel enough at normal fuel pressures, but it won't be able to if the fuel pressure is very high. Wayne has covered most of the other stuff.
Awww... I miss you too, Steve.

I tried both with and without the RRFPR. For some reason, the stock FPR maxes out at 50 psi even though it should theoretically go up to 59 psi with 9 psi of boost. Supporting data: The fuel pump primes at 50 psi at 0 psi boost (0" Hg vacuum). If I remove the RRFPR, fuel pressure stays at 50 psi from 0 through 9 psi of boost. This causes some lean spots around midrange.

So I've left the FFPR in, and turned it to minimum rate, which gives me about 70 psi at 9 psi boost. The injectors don't seem to go static until above 80 psi. Using the RRFPR evens out the lean spots a bit, at the expense of running richer than I need to at the top end, and some funny oscillations with maintenance throttle under boost. The RRFPR can introduce an instability in the fuel control loop in the midrange/mid-throttle region - can be interesting on the track or a tight auto-x course. The biggest downside of using an RRFPR is that fuel pressures can shoot past 80 psi when the engine backfires during cranking.

Another fuel pressure case in point: Fitz' MY00 fuel pressure only varies from about 50 psi to about 53 psi. And this is throughout MAP pressures from 20" Hg. to 12 psi of boost. If the stock RRFPR was a true 1:1 riser, he should be seeing over 60 psi at 12 psi of boost.

YMMV.

-WaC
Wayne
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Old 07-03-2002, 06:58 PM   #9
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I have a slightly different experience. First off, I think the stock FPR used in the MY99+ is different from that in my MY98. When I installed the larger injectors with the TEC2, I removed the Bell RRFPR. During idle, my aftermarket FP gauge reads 30psi with just the stock FPR. At atmosphere it is reading just about 43psi, and it appears to go up 1:1 with boost from there. Note that this was with both a Supra TT fuel pump and the STi fuel pump assembly which I'm currently using. I haven't been running over 7psi of boost, though, so I'm not sure if it'll max out at 50psi of fuel. Either way, 50psi should be plenty with my current injectors.

Steve
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Old 07-04-2002, 01:08 PM   #10
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Default Here's where my ignorance comes in

I thought with the Apex SAFC, you could do without actually having to get a FPR or RRFPR. *Here's where my ignorance comes in*

If you simply purchased larger injectors that you could lean out during part throttle and richen during WOT, wouldn't that satifsy all of your demands? I mean as long as it just touches 80% duty cycle at the boost your are running at WOT you should be fine right?

Using RC engineering's website, I caculated that with a 70 shot of nitrous and running 6.5lbs of boost at 75psi of fuel pressure (shooting for 270hp [137 stock, 65hp with turbo, 70 hp with nitrous]), I would need around 419cc of flow. The injectors wouldn't be maxed out and would only have to be opened up some but could be really leaned out during part throttle to compensate for running rich around town. What am I missing?

Note: People, please excuse my turbo psi and nitrous figures on stock internals. I am nuts I know.
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Old 07-04-2002, 07:16 PM   #11
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Steve: yes, that was my point, that the MY00 at least, has a FPR that does seem have a maximum pressure limit, and I seem to have found the limit with mine also. Apparently, you've been lucky enough to be able to run under whatever limit of your FPR, and I envy you for it. Mine idles at 30 psi as well (~20" Hg.), so I have no issues with the low end.

Kevin: how are you going to get 75 psi of fuel pressure without an RRFPR? The idea of using large injectors is the right direction, but it doesn't solve everything. The S-AFC is controlled by TPS, although I think it would have been a little more useable if it also had a MAP input. I've been toying with the idea of switching the TPS signal to the MAP signal to see what will happen. I can't see why it won't work. But it's too hot outside these days and I'm also too busy with my other hobbies.

-WaC
Wayne
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Old 07-04-2002, 10:31 PM   #12
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Default How?

Quote:
Originally posted by wac
Kevin: how are you going to get 75 psi of fuel pressure without an RRFPR?
-WaC
Wayne
I would get approx 70-75psi of pressure when I am using the NOS nitrous. I'm not speaking about everyday fuel pressure like driving around town. That would be 35-38psi or so like it is now.
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Old 07-04-2002, 10:59 PM   #13
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Kevin, I take it they are upgrade injectors for the Silvia SR20DET then? Reason I ask is if they were stock 440cc injectors then they would likely be out of a GTI-R which uses a top feed style of injector where the Silvia uses the side feed setup.
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Old 07-05-2002, 12:21 AM   #14
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N/A

I believe they were out of an S15, which appears to have larger injectors than the S13 & S14. Assuming Kevin receives the same injectors which were pictured on Ebay, they are indeed sidefeed.

Link to the Ebay auction were Kevin bought them:
http://cgi.ebay.com/ebaymotors/ws/eB...tem=1840440502

Jeff
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Old 07-05-2002, 08:23 AM   #15
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http://www.power-enterprise.co.jp/
they sell injectors as well as turbo kits for the EJ20 as well as alot of other cars plus they ship to the US. Just thought I would point that out for you guys.
Or directly to them at http://www.power-enterprise.co.jp/ex...p/inj_pump.htm
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Old 07-05-2002, 08:26 AM   #16
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Wayne, the MAP signal would be useful, but I don't know if it would be a good primary signal since it's "slow". I understand what you're looking for and it sounds like you need true engine management.
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Old 07-06-2002, 02:56 PM   #17
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Thumbs up

Daaa-AM Kev!

I cant wait to see that project come together!

When do you expect completion?
What about your timeline for an Atco test and tune night?


Keep us posted!
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Old 08-16-2002, 09:20 PM   #18
Kevin Thomas
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Originally posted by Rich L
Daaa-AM Kev!

I cant wait to see that project come together!

When do you expect completion?
What about your timeline for an Atco test and tune night?


Keep us posted!
Sorry man, I never responded. I'll send you a PM.


I just have a quick question about the SR20DET injectors. I just sent them out today to RC Engineering to be balanced and blueprinted and I'm expecting them back sometime late next week.

Once back, I'm going to have them installed. I forgot that I need some 'special connectors' to have them fitted to our fuel rails. This is correct right? If so, where can I get these 'special connectors' from? How much are they? Can RC Engineering put these 'special connectors' on for me so they can be plug-n-play once they get back? WAC, you did relay this info to me before but I forgot what you said. Being married makes me senial. What's my son's name????? Thanks

Last edited by Kevin Thomas; 08-16-2002 at 09:27 PM.
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Old 08-17-2002, 01:03 AM   #19
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Kevin

I don't think there's any problem fitting the injectors to the fuel rail. It's the wiring harness that has the issues. You could track down the correct connectors from a Nissan, or rig up some sort of universal connector I imagine.

Jeff
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Old 08-17-2002, 06:49 AM   #20
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I've got a set of the stock S13 370cc SR20DET injectors and the injector plugs cut off of the harness. Anybody interested? I am going to go with some aftermarket units after all.
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Old 08-17-2002, 06:04 PM   #21
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Quote:
Originally posted by Portly
Kevin

I don't think there's any problem fitting the injectors to the fuel rail. It's the wiring harness that has the issues. You could track down the correct connectors from a Nissan, or rig up some sort of universal connector I imagine.

Jeff
Thanks Jeff I appreciate this. What bothers me is I thought it was a simple matter of going to a certain website and/or calling a phone number, ordering this part and having it installed. Now I have to track down the correct connectors (which I don't have a clue which is what) from Nissan or rig something up?

If this is the only option people have in order to have Nissan injectors installed on their Impreza, than I highly do not recommend buying them unless you either know someone who knows what they are doing or you do. They are not plug-n-play (and I understood that) and you have to find out what connectors will work and track them down. There is no certain place you can just order these connectors.

If there is a place you can order these connectors from and it's been told what connectors you need, than my apologies. I'm not a mechanic so I don't have a clue.

Hey Jeff,
If push comes to shove and this isn't a simple matter to be resolved, than I'm just going to sell these injectors for ones that will fit without any drama connecting them so I can continue on. I won't be able to use them anyways.
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Old 08-17-2002, 07:30 PM   #22
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Since the connectors for the DE and DET model SR20 are the same can't you just use the connectors from the non-turbo cars which are easy to find in junkyards. Well at least here they are.
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