autometer air/fuel ratio gauge. [Archive] - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum: DSMtalk.com

: autometer air/fuel ratio gauge.


Red93GSX
11-19-2002, 01:07 PM
i have 1g eclipse with k&n filter and cut air can, 3inch turbo back exhuast, and boost control. its currently set at 16 psi, on stock fuel.... and my autometer gauge shows me a ways into rich side when i floor it... does this mean i can safely boost more? i run 92 octane gas.

Blackboost
11-19-2002, 01:19 PM
Nope...

The A/F gauge will always tell you that you (all the way to the green side) that you're rich, but that isn't the truth. The ECU uses the O2 sensor to monitor the a/f on the engine everytime, except at WOT. This is called closed loop operation and that's why you always see the light on the A/F gauge moving back and forth very rapidly in there. When you go to WOT, the ECU switches to open loop mode and dumps a lot of fuel on the motor to protect it, she also ignores ther O2 readings at WOT. That's why the gauge at WOT is always on the green side. Because of this the A/F gauge is useless as a tuning tool. Save some money and get an EGT gauge...

Before you raise the boost...
1. Get an aftermarket fuel pump (and rewire it)
2. Get an EGT gauge (exhaust gas temperature). Watch those EGT's and never let them go higher than 1650F. I always recommend staying in the 1550 to 1600 range just to be sure.
3. 550 injectors and a S-AFC are a great investment too.

BTW, it's always nice upgrade the upper intercooler pipe and remove the lower honeycomb of the MAS before proceeding with any of the above mentioned mods...

Red93GSX
11-19-2002, 01:23 PM
already removed the lower honeycomb. but ill start saving thx much!!

iameatingpez
11-30-2002, 04:24 PM
there is though, an a/f gauge that is redone and ONLY works at wot. read about it somewhare online, its an autometer and i believe machv.com carries it.
*nick*

Blackboost
11-30-2002, 10:27 PM
That's true. But keep in mind that you have to learn how to read what the leds mean. I still think that an EGT is a better gauge...

slow car
12-01-2002, 03:27 PM
why should an aftermarket fuel pump be re-wired??

broadypunk
12-01-2002, 03:42 PM
yes...there is a modified a/f gauge (discussed on here plenty of times) but to read for yourself...check out www.gadgetseller.com (under a/f gauge theory)... as for the fuel pump needing the rewire...as you will see when you install a fuel pump...the pump won't actually receive all the voltage it needs (or that we want it to receive) so with a thicker gauge wire, it'll receive those volts...which means more power to the pump....which means more pumping.

NewB2DSM
12-01-2002, 06:45 PM
That's why the gauge at WOT is always on the green side.

I have the modified one and it works well.. Not that i would ever use it to tune the car but it does give you a pretty good idea of what your car is doing. To really tune the car you need either an EGT guage or a wideband o2 dyno to tune. And on cold nights my guage does read stotch a little...:D

vlaar
12-25-2002, 12:07 PM
So basically if one is looking at protecting his car, he or she should look at getting an EGT guage RATHER than an A/F guage??? Thanks. Best EGT guage and where is it the cheapest:)

broadypunk
12-25-2002, 12:31 PM
there aren't really "crappy" egts. they all do the same....you're gonna pay more for greddy, hks, blitz etc...as opposed to autometer. i bought my autometer c/f gauge with probe for 75 bucks brand new off of ebay...so you just need to look around. there are a few on the traders now.
www.dsmtrader.com
www.thepartstrader.com

vlaar
12-25-2002, 12:34 PM
Thanks. I guess if I have an Autometer CF boost guage, it would be best to get the same kind EGT wise. Also, if I have a triple pod pillar, should I fill the third spot with a fuel pressure guage? I figure for now, a boost guage, EGT, and fuel pressure should be fine... Thanks.

Gopherhog
12-26-2002, 08:35 PM
I have heard that the autometer brand EGT gauges aren't very accurate, due to slow response and general inaccuracies in the temperature..

That was why i was opting to go w/ the Greedy EGT gauge.. It looks like a quality piece, and have heard nothing but good things about it. Lowest price i found was about $150 for it though, as compared to the $75 you quoted for the autometer..

I guess it's up to you what you spend your money on.

Blackboost
12-26-2002, 10:05 PM
Originally posted by Gopherhog
I have heard that the autometer brand EGT gauges aren't very accurate, due to slow response and general inaccuracies in the temperature..


The gauge itself is very accurate indeed. The probe however is not a super fast reacting one. Get a TRE probe and problem solved...

harry99GSX
12-26-2002, 11:38 PM
Originally posted by Blackboost


The gauge itself is very accurate indeed. The probe however is not a super fast reacting one. Get a TRE probe and problem solved... Yeah this is actually true with alot of EGT gauges. The gauge itself is accurate but only as fast or reliable as the probe thats being used.

Gopherhog
12-27-2002, 05:53 AM
Are most temperature probes interchangeable with other gauges? If that is the case, i'll just get 3 autometer gauges.. i was going to do an A/F, 30-0-30 boost from autometer, and then the greddy EGT. But if i can keep the same scheme the whole time, that'd be great.

EasyTvelve
12-27-2002, 11:51 PM
I just wanna come back to the first post.
if you're already running 16psi of boost, you brobably don't wanna increase it with stock turbo cause you'd just be blowing hot air.
As a matter a fact before you even start messing witha boost controller you should look into a pocketlogger or something, to see at what boost your car is producing the most amount of power. For example, when I had my car at 16psi my time was 16.9 (1/4mile)
when at 12 PSI 16.0
Just my .02cents.

FastRthenU
12-28-2002, 06:39 AM
Ok, if the Ecu goes into open loop, at WOT and ignores the O2 readings, why does that make the gauge usless?? Just because the ecu isnt using the 02 readings, doesnt mean that the readings that you are getting from the air/fuel gauge are false, and unusable. even if the ecu goes open loop and starts to dump fuel, you are still getting a proper reading from the gauge. You still know if you are rich or not. Thats not usless in my mind. Maybe i dont know what my accual A/f ratio is. but atleast i know im not running lean.


No i would never tune off of a led a/f gauge, but its not usless. I wouldnt want to tune off of a EGT either. doing both is a bad idea. You want to do real tuning get a data logger.

Blackboost
12-28-2002, 06:12 PM
Originally posted by FastRthenU
Ok, if the Ecu goes into open loop, at WOT and ignores the O2 readings, why does that make the gauge usless?? Just because the ecu isnt using the 02 readings, doesnt mean that the readings that you are getting from the air/fuel gauge are false, and unusable. even if the ecu goes open loop and starts to dump fuel, you are still getting a proper reading from the gauge. You still know if you are rich or not. Thats not usless in my mind. Maybe i dont know what my accual A/f ratio is. but atleast i know im not running lean.

The led A/F gauge will always go to the rich side at WOT regardless if you're running rich or lean. For example, you could be getting an EGT reading of 1800F (kaboommmm!!) and the dumb A/F gauge will always be on the rich side. That's one example of why that gauge is a real POS...

FastRthenU
12-29-2002, 01:30 AM
Well thats just not true. Why yould you think this? I have been at wot and seen my gauge go to red. Once i blew off the vaccum hose that went to my FPR. So when i got boost it didnt raise fuel pressure. Guess what my gauge went red. So i think you are worng about this. why at WOT would all of a sudden you gauge just go green? It goes green because it goes open loop and dumps lots of fuel causeing a rich condition.

Taboo
12-29-2002, 04:53 AM
Originally posted by FastRthenU
Ok, if the Ecu goes into open loop, at WOT and ignores the O2 readings, why does that make the gauge usless?? Just because the ecu isnt using the 02 readings, doesnt mean that the readings that you are getting from the air/fuel gauge are false, and unusable. even if the ecu goes open loop and starts to dump fuel, you are still getting a proper reading from the gauge. You still know if you are rich or not. Thats not usless in my mind. Maybe i dont know what my accual A/f ratio is. but atleast i know im not running lean.
It's not the accuracy of the A/F gauge at WOT but inaccuracy of the O2 sensor above 1400' EGT what makes the A/F gauge useless. I've seen the O2 sensor output voltages as low as in the mid .70s (which would show on the A/F gauge as lean) while the engine ran pig-rich at 11.8:1 of actual A/F ratio and 1580' EGT at WOT. The "A/F gauge" should be actually called "O2 output gauge" since it does not display an actual A/F ratio. Accurate O2 sensor output voltage that can't be accurately translated to A/F ratio is completely useless. It's like claiming that you can tell if you run rich or lean from your spare tire pressure or the level of your windshield fluid.
Originally posted by FastRthenU
Once i blew off the vaccum hose that went to my FPR. So when i got boost it didnt raise fuel pressure. Guess what my gauge went red.
No kidding.. The vaccum hose goes from the intake manifold through the normally-open fuel pressure solenoid to the fuel pressure regulator. If you blew off the vacuum hose to the FPR (which is something I've never heard of or witnessed in the 12 years I've been working on DSMs) and had a huge leak in the intake, how exactly did you get boost in there? If you want to know what would really happen in case the hose would ever come off, you'd hit a fuel cut due to pushing huge amount of air through the MAS once the WGA would not open due to the boost loss in the intake plenum and the turbo would keep spooling faster and faster - if the ECU would not retard the timing while dumping tons of fuel to the cylinders first - due to the knock caused by the hot air the overspooled turbo would produce.
Even if your A/F gauge actually went red, it means literally nothing. The gauge will go red even if the O2 sensor mulfunctions or dies. It does not necessarily mean you run lean. One can tell if he's running lean or rich just from the EGT and timing (dirrectly affected by knock), that all one needs to tune the car. No O2 sensor voltage - unless it's wide band...

Stock TSI
12-29-2002, 12:14 PM
Regular o2 guages are very inaccurate and concidered "usesles" due to the level of inaccuacy(in most cases) and the amount of damage that can be done by the time the readings are obvious. You can use a voltmeter that you already have and not have to spend any money. Wideband o2 work much better and you can tune a car off these but only to a limited extent. Further how do you know if your 02 is grounded properly? You can have the best o2 sensor on the market and hav it be useles if its not grounded properly. Further in a post by Todd day in 1998 the ECU samples o2 reading bt coil fire bc the coil fire screws up the ground giving inaccurate readings. You can see why the sentiment is that they are very in accurate to tune by....Its kind of like going outside to get a tan. Just bc its hot outside doesnt mean your going to be getting direct light; you need more info if you not going to dyno your car

EGT guages are more of an accurate way of tuning, But "even the better tuners forget you can high EGts from agressive timing BUT still have a rich o2 readings, thus not getting you the best power." Thats an indirect quote from SCC February 03 issue.

Speaking with regard to a knowledgeable mechanic you might meet on the street, some say use EGTs in conjunction with a dyno. However you have the best(more accurate if you dont have a dyno) option(at least on a 1g) buy a pocketlogger set up for $200. Its the best thing you can do for your DSM in conjunstion with a pressure tester(make sure you car is running good before moding). Many tune by knock and watch their EGT guage and the o2 readings on the logger for strang anomalies as mentioned above. Although, there are plenty of very fast street cars who only tune by logger(knock and actual ECU 02) without the EGT guage.

vlaar
12-29-2002, 03:16 PM
Great input guys. So basically, I should be looking at buying a pocketlogger and palm for my dsm--around 225 dollars total? Since I'm budgeted and don't have a ton of mods (yet), can I hold off on the EGT guage for now? I do have an Autometer CF boost guage though. Thanks.

Kevin
'90 Talon TSi FWD

Current mods: small 16G, MAS mods with K&N,
2.5inch testpipe, Arospeed muffler
Soon to come: Pocketlogger and m100 palm!

FastRthenU
12-29-2002, 04:20 PM
Yah, maybe if the car that this happend to was a DSM. It happend to my supra. So, im my years of working on supra's, i have seen this happen, and i have seen it happen to differnt cars also.

I would never use any gauge to truley tune a car. A wide band, and a data logger is the only things i would use. Even a egt gauge can give you high readings, and its not because of fuel but because of timming.

Yes i agree, that the led air/fuel gauge is not the best gauge to have. But it has saved me a few times. (hose to FPR blown off)

As for the o2 being inaccurate at 1400 degree's. Not all cars hit such high temps as dsm's do. If i hit 14500 of my supra its way to hot anyway. So incunclusion, they arnt that great. But i would not say complete usless.