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Guest Message by DevFuse
 

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My EA82T->EJ20G conversion


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39 replies to this topic

#26 Nico

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Posted 21 June 2012 - 11:19 PM

just so you know i used ej20g heads on a build back in the day on a ej22t built motor and the heads dont flow past 6000rpm well.

so 7400rpm would be point less to rev to.

#27 presslab

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Posted 21 June 2012 - 11:34 PM

just so you know i used ej20g heads on a build back in the day on a ej22t built motor and the heads dont flow past 6000rpm well.

so 7400rpm would be point less to rev to.


Yeah that's true, my shift points are not all at 7400 RPM. There are pretty large jumps between gears, so it's a trade-off of the power falling off and then setting up for the next gear. So generally I have the 1-2 shift rev out pretty high so once in 2nd it's in the meat of the powerband, but 2-3 shift is a lot lower RPM.

Also it builds boost faster if I let it downshift for overtaking, even though it will shift up pretty soon.

#28 presslab

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Posted 11 November 2012 - 10:10 PM

Quick update.

I replaced the downpipe with an aftermarket WRX one from eBay. 3" stainless, and I did a few cut and welds to get some more clearance. I also put on a high-flow 3" cat; although my car would never pass CA smog due to the JDM motor (and doesn't need to) I am considerate of the environment. This solved my high RPM power loss that only happened when the exhaust was cold. An odd problem; after noticing that with a warm engine (cruising slow) it would occur, yet when I was in the gas for a minute it went away, I figured it was not the coolant temperature but something else warming up. The stock WRX cats (my old downpipe) when hot would apparently flow much better than when cold. Anyway now with 3" from turbo-back I don't think the exhaust will be a problem. :-p I might even bump up the shift points as it's very strong at high RPM.

Over the summer it didn't overheat at all while driving, but I did notice if it was close to 38C (100F) outside the coolant reservoir would overflow. This would only happen a few minutes after I'd parked due to the radiator heat soaking. The WRX has a bigger reservoir, but rather than go that way I put in a higher temp thermoswitch (105C) that is enabled even when the key is off. So I still have the ECU controlling the fans, but if the thermoswitch kicks in it will turn the fans on high as well. This way when it would heat soak it would cool the radiator down before it would push coolant out the reservoir.


Finally I got around to correcting the coolant temperature gauge. It read a bit low with the EJ conversion, and most importantly it wouldn't indicate overheating when I tested for this. There is always the common fix with the resistor in parallel with the thermistor. But this creates a voltage divider and although the gauge might read correctly when at cruising, it won't be a good indicator of an overheating condition. Modifying the current source is the correct fix.

I traced out the circuit and found the resistor in the digidash instrument cluster that provided the current source to the thermistor. It was 160 ohms, and I settled on a 330 ohm replacement. This puts the gauge in middle at 80C (cruising) and when it lights the red mark it's 105C. I read the newer factory Legacys tripped the gauge into the red at 120C. This seems much too hot! However maybe a 270 ohm resistor would be ideal here. We'll see how it goes after I get some time on it.

#29 Gloyale

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Posted 12 November 2012 - 03:01 PM

I've used the divider resitor in mine. When they get hot, the gauge goes almost to the red, and is way higher than normal so it's easy to tell.

Mostly I've used a 270 ohm resistor. However, on a recent swap that was inadequate. Using a 47 ohm resistor placed the gauge in the correct range. Not sure why that one was different? Any guesses?

As for your car.......105 C = 221 F

Definately getting warm, but not "overheated". I would want the red zone to be over 230F so I wasn't worrying every time I climb a steep pass.

At any rate, do you think a similar modification like yours could be made to an Analog dash. Would it be the same?

#30 presslab

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Posted 12 November 2012 - 03:23 PM

I've used the divider resitor in mine. When they get hot, the gauge goes almost to the red, and is way higher than normal so it's easy to tell.


So have you measured any temperatures when the gauge is close to the red mark, with the 270 ohm divider resistor? How hot is hot?

Based on my calculations an EJ sensor will be 1/(1/19 + 1/270) = 17.75 ohms at 120C. The EA sensor is 16.1 ohms at 120C. So that means the EA gauge will read lower than it should when overheating, with the 270 divider resistor.

Not sure why that one was different? Any guesses?


No idea, sorry. As far as I know all the EAs had the same thermistor, and the same goes for the EJs.

As for your car.......105 C = 221 F

Definately getting warm, but not "overheated". I would want the red zone to be over 230F so I wasn't worrying every time I climb a steep pass.


The high speed rad fan comes on at 100C. If the gauge goes to 105C that means that the coolant system is not sufficient, and unless something is done soon the engine will be damaged. Yeah it might be a bit conservative, but I was just using an IR gun on the upper rad hose so I'm not 100% on the 105C. Maybe I should hook up my SSM cable.

Like I said we'll see how the 330 ohm cluster resistor does... There are two pips that are red on the digidash, so I can still see if the temperature climbs further. 105C would just barely turn on the lower pip.

At any rate, do you think a similar modification like yours could be made to an Analog dash. Would it be the same?


It would be very similar I imagine. The resistor value will likely be a bit different. It's not hard to find though, just trace the wiring on the PCB until you find a resistor of similar value. On mine there was a 10k resistor, the 160 ohm resistor in question, and a small capacitor on the circuit that connected to the sender.

#31 nncoolg

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Posted 13 November 2012 - 07:00 AM

What is the theory of the cold / warm cat? that sounds interesting...

#32 presslab

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Posted 24 December 2012 - 09:30 PM

Well keeping the pipes warm (and the cat too) keeps the flow up. It's the reason that racers wrap their headers to keep the heat in. The hot exhaust gasses flowing by the colder pipe creates turbulence.


I checked my highway mileage the other day, going about 72 MPH, and getting on it to pass a few people here and there. It was 25.3 MPG, better than the car's rating yet with three times the horsepower. I could probably get 1 or 2 more MPG if I didn't pass anyone, and didn't use oxygenated gas.

#33 Turbone

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Posted 25 December 2012 - 02:22 AM

I looked for pics here of Turbone's CAI but I haven't found anything yet. Maybe he will chime in. ;) My buddy was trying to give me some old computer cases just the other day, perfect timing! Something to play with my new TIG welder too, sounds like a nice project. Thanks for the idea.


Sorry for such a late response, but heres a couple pics.

Posted Image
Posted Image

Eulogious is correct, I made it from the side of a computer case. Its about 14gauge I think, real thick.

#34 monstaru

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Posted 25 December 2012 - 06:06 PM

Sorry for such a late response, but heres a couple pics.

Posted Image
Posted Image

Eulogious is correct, I made it from the side of a computer case. Its about 14gauge I think, real thick.


Incidently, That looks like about 16 guage. :)
cheers

#35 nncoolg

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Posted 25 December 2012 - 06:14 PM

what kind of top hose is that, never seen one of those one a subie?

#36 presslab

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Posted 25 December 2012 - 08:31 PM

Thanks a bunch Turbone! I haven't had a chance to work on the air filter setup. I like what you've done there. :)

Is yours loud? Mine does the PSSSSSSSHHHHH when I let off the throttle, it's the WRX BPV I have installed; maybe a little too ricey for me, heh!

#37 Turbone

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Posted 26 December 2012 - 12:16 AM

I have a AVO recirc valve, its real quiet.

#38 Turbone

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Posted 26 December 2012 - 12:18 AM

Incidently, That looks like about 16 guage. :)
cheers


The tops are rolled a little bit, but it could be 16. I dont deal with sheetmetal as much as you do.

#39 Turbone

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Posted 26 December 2012 - 12:18 AM

what kind of top hose is that, never seen one of those one a subie?


Are you talking about my car?

#40 nncoolg

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Posted 26 December 2012 - 05:10 PM

Yes




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