Open atmosphere = rich at idle

[vrg3]

I can't seem to find a tuning guide... There is the manual on their web site but I can't seem to read it. Probably because of the Japanese fonts or something. But what in that guide would demonstrate that GM, Toyota, and Mazda use 3D maps?

SAFCs are much easier to deal with than standalone ECUs because all they do is manipulate the stock ECU, so you retain most of the original mapping, programming, and safety features.

To properly tune a standalone you do definitely need to keep an eye on EGTs and on the air/fuel ratio (though I wouldn't trust a narrowband sensor, even if it is heated). And I'd hope that the ECU would be able to tell you its readings from the TPS rather than making you measure it yourself.

But that's orthogonal to the issue of how fueling is mapped. You can't really go every 1% on most systems, since maps are usually 8x8, 16x16, or maybe 32x32. You generally can specify the sample points between which the ECU interpolates, though. Every ECU I've looked at (the stock Subaru system, DTA, Link, MegaSquirt, TEC-II, etc) works this way.

When I start remapping my ECU I'll be relying mostly on an EGT gauge and a wideband air/fuel ratio gauge, and road tuning.

[FrmRgz2Rchz]

vrg3: How did you pull the code from the ECU. I thought about opening up one of my spare ecu's, taking out the integrated eeprom chip, and putting it on an eeprom reader/burner. Would this work?

The code is in assembily language, right? I have a little knowledge of assembly, but not much. My main interest in manipulating the ecu was to eliminate fuel cut when running too much boost. Any ideas on how to go about this?

[vrg3]

I brought up my inquiries into the ECU in this thread:
http://bbs.legacycentral.org/viewtopic.php?t=14066

I've made some progress since then, and I'll write it up shortly.

If you have one of the early ECUs manufactured by Hitachi (as opposed to JECS), then you could indeed pop out the 27C256 EPROM and scan it. It is also possible to dump the ROM through the Select Monitor connector, which is what I did with a JECS ECU.

Adjusting (not eliminating) fuel cut is also something I plan to figure out how to do. I'd also like to be able to increase boost using the factory boost control system. If I figure it out I'll be sure to let you guys in on it. :)

Wait -- so you have spare turbo ECUs? Any chance you'd be willing to sell one? :) As far as I know, all Legacy Turbo ECUs are Hitachi.

[FrmRgz2Rchz]

Well, I had 2 spares, I'm not quite sure where one of them went, the other spare is still in the car, and that is the one I plan on playing around with.

I read through the ECU thread, very interesting stuff in there. Can you send me the ROM output that you got. frmrgz2rchs@aol.com

[Redline Dreamz]

In the tuning guide it just kinda tells you about how everything comes together. How each adjustment effects the other and how it changes the fuel delivery overall. Its kinda hard to explain what it says because the one i read was a translated Japanese version so it was pretty garbled.

The 50-100% thing, i was measning throttle position. You could go lower i suppose but its rare to see too many people on race day under 50% throttle. I still agree with everything your saying about thte maps because ive read about the same stuff... maybe im thinking of a different interpritation of the same map but its called something else. Now if everything was still running on 4 barrels, things wouldnt be this complicated

[vrg3]

FrmRgz2Rchz - I emailed you. I'm actually considering just posting it, since now that I look at it, I don't see any copyright markings or anything.

Redline Dreamz - Oh, well, it's definitely true that the TPS and the oxygen sensor affect fueling. They're just not in the primary map.

Yeah... Carbs were much more accessible and everything. Just not nearly as capable.

[ciper]

Ooh, I want to play too!

I think all of us can agree that an atmospheric dump valve will cause a momentary rich condition. Forget about if this is good or bad for a moment

One thing we have to realize is the seperation between full throttle/power runs and daily driving.

Under full throttle/power you will momentarily run rich with EITHER valve since your car is already tuned to run rich (especially if its not stock and you have retuned it). The atmospheric dump will just make it slightly more rich.



During daily driving, especially in a manual transmision vehicle, the blow off will activate often. Think of how many times you would shift in a standard city drive with max speeds of 45 and stop lights every 3/4 mile. That would result in quite a bit of extra fuel.

Our oxygen sensors are narrow band. They are slow to react and older units just keep getting slower. This "momentary" rich condition will exist in the ECU and cause a reduction in fueling at the bottom of every gear.

If you could watch the ECU you could see that recovery from any non stoich event is a bobbing motion until its back to normal. These larger than normal rich conditions cause the longer "bobbing" sessions. You end up shifting quite often so the ratio of running stoich to running extrarich-lean-rich-lean-normal starts to increase.

You may not realize but smell the used oil from an atmospheric dump car compared to a similar recirc car. The atmospheric dump has more of a gas smell.

Personally Id want to run a recirc valve but the options are limited. If I cant find one that I like the second choice for me would be a silent atmospheric or combo. No bling/rice for me thanks

[LegacyPunk]

Back to the wanting the sound of an open atmospher BOV, with out the "weird" effects of an actuall open atmospher BOV, why not just stick the stock one right next to the intake? anyway, I ran an open air WRX BOV on my car and it idled fine, which was weird, but ran too rich for my likeing, and running too rich on a daily driver, kills gas mileage and im a poor broke college kid. Although I did find better turbo response with an open atmosphere. I say it just depends on what you want. ok ill stop trying to sound smart now, quite the informative topic though

[FrmRgz2Rchz]

I'm currently running an open valve. It doesn't reek of gas, nor does it idle horribly... idle isn't perfect though. I think it's running like this because I have a boost leak.
When I was trying to install an oil pressure sender behind the alternator, I broke a nipple off the plastic hose that was in the way. I did a temp fix, and havn't gotten around to fixing it. Gas mileage sucks, and idle is a bit funky.
So...if the car seems to run fine when you run open atmosphere, maybe you have some extra air getting in to counterbalance the richness.

[NuwanD]

I've been running an atmospheric BOV for a year now. My idle has not changed and is still great, and if i drive normally (which is fairly rare) i can still get 500+kms a tank. I tend to to get 300+kms due to my heavy foot and 15psi of boost. So i doubt my car is running any richer than stock.

Our cars don't seem to age identically, i have many friends with the same car and their motors behave quite differently when compared on a stock to stock basis. Ie: idle, richness... Obviously maintanence and driving styles have played major roles in the way the cars behave now.

[TurboLegacy]

i vented my bypass for a week straight, and then plugged it back in cuz it was running bad, now it hasnt been the same ever since. it runs horrible, it might be something else, but i dont know yet