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sensor mods for 98 suburban-5.7l 1/2 ton 4wd
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Sartech Offline
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Post: #1
sensor mods for 98 suburban-5.7l 1/2 ton 4wd
[mikes comments are in green]

Mike,
Thanks for your input......I will summarize in a condensed format:

1-first I would very much appreciate the graph if you can lay your hands on it.

2-I have the doc you referred to and have accomplished all of the mods-a 1k ohm resistor on my IAT gives me about an 80° increase in my temp signal read at the ECU which translates to approx. 5-6° retard in timing. I get this result whether in open or clsd loop.

3-2.2k resistor on CTS for an increase in temp signal at the ECU of about 30°. Seems to be the same in clsd or open loop also.

4-Have built and installed the MAP trimmer and dialed in about .5 volt offset. Drops the indicated MAP about 1.5 psia.

5-Concerning the MAF-i have installed a MAFT GenII translator (info at http://www.maftpro.com/tgen2info.shtml) to modify the MAF over the complete range of operation. This allows me to intercept the signal from the MAF and increase it or decrease it to suit my needs. Unfortunately, this signal will only have an affect when in open loop. This is the primary way I am able to get my open loop AFR to18/1-but I can only do it in open loop. Ex: 1350mhz in from sensor---1180mhz out to ECU to simulate less air than is actually going to the intake.

6- 6-I don't use the scanguage for mileage calculations. You are correct it is not very precise for that with what we are doing. However, it is a great tool for seeing the results of mods on the sensors.....in real time by the way.

7- It is my estimation that I could conceivably run afr's in the range of 18-20-in clsd loop-with brown's gas and not adversely affect my engine. The assumption is that head temps would be significantly cooler due to efficient combustion resulting from bg and the resuting exhaust gases would contain more O2. If I could force the afr to that in clsd loop, I could prove my theory with an EGT pyro (which I have) and verify the effectiveness of bg in the combustion process.

Currently, I am unable to get results in my mpg in any consistent manner. I have gotten a couple of mpg gains in a few runs but that does not in any way suit me as I can almost do that with driving habits alone.

Am seriously considering taking a huge step and moving into the full scale ECM programming arena. This will alleviate all these concerns with sensor mods, inadequate devices for modding signals, and the general head scratching that i've been doing. These guys (http://www.hptuners.com/order.php) seem to have a pretty good product and I will be contacting them to see if I can rebuild the fuel maps on cars to accomplish predictable results. I'll let you know.

In the meantime, I may be trying a run of 100 miles or so with the vehicle in open loop and sensors modded to give me a consistent 18/1 and see if I get results.
That will at least verify the bg effectiveness.

Onward, I guess. I'll be interested, as always in any further comments and would certainly like to see the graph.

I'll run across it again. I've seen it so many times. The only ones I found when I was looking for you were not actual data but representations that didn't show the numerical relationships. But I'll get you one.
Thanks,
Steve

Hi Steve,

Ok, I added my replies down below where appropriate too. Forgive me. I'm sure some of my explanations are things you already know. I just don't know what you do and don't know, so sort of brain dumped. I've given you a reference that I think you'll find explains much about what you are experiencing now.

Please write me back if your questions are not answered satisfactorily.

Sincerely,
Mike


steve smith wrote:
Mike,
Have answered your questions below. Let me know if you have anything further to add.
Steve

From: Mike Kehrli [mailto:mike@fuelsaver-mpg.com]
Sent: Sunday, March 23, 2008 11:19 PM
To: steve smith
Subject: Re: 98 suburban results with efie installed


Hi Steve,

Thanks for the attachment. The embedded image has something else in it. I can't make out all the smaller text, but I don't think I need to. The symbol in the sensor with the diagonal arrow through it is the sensor, and the other circuit is the heater. The high side is the signal and the low side is the signal ground. The high sides of the circuits are 19, 22, 21, and 20. I can't tell if any of these are upstream of the cat though. As you probably know you only have to treat the upstream sensors.

Please read my responses below, and answer the questions.

It may be that you'll need to dig into your other sensors in order to lean your mix further. But I'd like to see your answers before making that assumption.

Also, you have 4 oxygen sensors, yes? Are 2 upstream and 2 downstream of the cat? I couldn't read everything in the graphic.


Mike,


I have attached the O2 wiring diagram for my vehicle-98 suburban, 5.7l 1/2 ton. Please note the following for proper installation.\:

terminal 19 is hi signal to ecu from bank 1 sensor-I spliced here and my efie white is going to 19.......my efie green to ppl/wh from sensor.

terminal 21 is hi signal to ecu from bank 2 sensor-I spliced here and my efie blue is going to 21.......my efie brown to ppl from sensor.

I read normal cross counts on these terminals at the ecu when efie is off (with an analog vom). The signal lo on both sensors (terminals 25 & 7) read negative when operating in closed loop-engine running.

What do you mean by "cross counts"?

OBDII talk for the voltage swings on the O2 signal. The computer actually counts the number of times the voltage swings from 600mv to 300mv (approx)-across the 450 baseline and will give a code if not within predtermined range.

Totally got it. Thanks.

When efie is on-with 100 mv offset dialed in--I can see the offset on the vom at the ecu-(difficult to read exact due to oscillations). When efie is off, reading drops back.

Appears to working normally, correct?

Yes, this appears to be normal

Here is my problem...............I have a dual wideband A/F meter (made by F.A.S.T) installed in the exhaust after the bank 1 O2s to read A/F on the fly. With a 100mv offset to the sensors I would expect to see a significant increase in A/F ratio. There is no change at all. When I dial the efie up to 275mv offset, I can get about 15.2-15.4/1 average at best. Any higher on the efie and I will get an SES light - sensor signal out of range-so 275 is about as high as I can go.

Sorry if you already told me this, but what kind of fuel saver are you using? HHO? Other? I'd like to know what your afr meter is telling you when the HHO (if you're using that) is on, but the EFIE is off. You should note that the efie is not for leaning your mix. It's actually for un-riching a falsely rich mix due to another fuel saver confusing your ECU. Also, a change from 14.7 to 15.2-15.4 is not insignificant. But the bottom line is that even if it's reading 14.7 with your fuel saver running, you should be in good shape. What you don't want is to run your HHO and then have the ECU dump gas into the mix and richen it and you then lose your mpg savings.

I have Georges HyZor on the car. It works flawlessly-about 2-3 amps and good gas production. O2 is telling me the actual A/F ratio in the exhaust after the front O2's. It reads 14.7/1 ratio when efie is off, and 15.2-15.4 when efie is on and set to about 275mv offset. If I set it down to about 100-there is effectively no change in the A/F ratio. My point is I should be able to drive the computer to retard fuel enough to get a 17/1 ratio (leaner) reagardless of whatever else is going on if the efie is doing its job. This is not the case.


This is an incorrect assumption. If you look at a graph of air/fuel ratio vs oxygen sensor voltage, you'll see that it's very steep at the 14.7 volt make/break point. An A/F ratio shift of .5 to .7 is correct for a .275 voltage shift.

The point is that it's quite steep, so when you raise the voltage of the sensor by .275 volts, you raise the whole graph. And if you then find where the new "stoichiometric" point is, you will see that a shift of AFR of about .5 - .7 is about right.

However, if you want to lean the mix further, and your car (as it appears to be) is programmed within very tight guidelines (evidenced by throwing a CEL when you go above .275), then you'll have to get into further tuning. I wanted to refer you to a doc on this subject in last email, but the site was down. I copied the data and stuck it in my own page (for the time being - I've separately email the author asking his permission). You can find it here. You can read it at your leisure, but it tells you how to adjust the other sensors of your vehicle, which will then allow you to take the EFIE to larger amounts (without throwing an error), and also how to increase the air/fuel ratio by use of the other sensors directly and in conjunction with the EFIE.


When in closed loop, A/F is determined primarily by the computer assessment of the O2 signal. So a 200 mv offset (for example) should push the signal high and cause a "go lean" condition. I cannot get the vehicle to respond this way. I should mention I have a scanguage II installed which is invaluable in seeing a number of parameters in live operation. I can see the same coolant temp, IAT, timing, rpm, whether clsd or open loop and others that the computer sees while in driving mode.

It seems the ECU on the car will not let the A/F ratio go lean in clsd loop for some reason. It was my hope that you might have some idea why. I apparently am going to have to research this out further and find a reason for failure to respond to my efie.

The doc above should be an excellent start on that research. However, don't minimize the value of the .5 to .7 gain. Try driving with that setting and see how you do on a tank of gas. I should tell you that when you monkey with the sensor signal your mpg readings on the Scangauge are no longer valid. It uses the "fact" of it's known air/fuel ratio in its mpg calcs. So you'll have to measure by miles divided by gallons, the old fashioned way.

My objective, and the thought I am following here is that we can run much leaner than stock with brown's gas in the combustion process. We can also run with lower timing advance due to shorter combustion time-all without a loss in power but a significant gain in mpg. My target A/F ratio is 17.5/1 lean as I think that is a moderate number and should produce results without damage to the engine.

Just as one other note on lean running. Any engine can run leaner. The reason the engines run as rich as they do is to (hold on to your hat) cool the engine. The liquid gas in there, evaporating, cools the engine. You could run any engine at probably 20 to 1 right now, and it would run great, right up until the time it burned out the valves.

In your case the computer just won't allow it any more than an AFR shift of .5 or so. Once the other parameters it uses start getting shifted too, then it can shift the air fuel ratio. The doc discusses this in detail.


When in open loop, my A/F ratios will shoot to 17.5 - 18.5 due to all my sensor mods which affect open loop.

I should clarify--the above are good results I get when I am in open loop. It demonstrates that I can get the vehicle to run at the ratios if I keep it in open loop and don't rely on the efie. When in closed loop and running on O2's and efie setting, I can't get these results. Therein lies the problem. I prefer not to run the vehicle in open loop if it is not necessary.

I cannot get my A/F ratio up (lean) no matter what I do with the efie. I suspect my wiring is in error due to the hi and lo connections on the ecu, but doesn't make any sense. I should be able to dial in offset and see a measurable result in A/F ratio..........correct?

Can you look at the diagram and tell me if you think my installation is correct? Any suggestions you have for changes would duly noted.
It appears you are hooked up correctly.


Thank you,

Steve Smith
(This post was last modified: 03-25-2008 07:57 AM by mike.)
03-25-2008 06:48 AM
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xcite Offline
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Post: #2
RE: sensor mods for 98 suburban-5.7l 1/2 ton 4wd
Quote;

Am seriously considering taking a huge step and moving into the full scale ECM programming arena. This will alleviate all these concerns with sensor mods, inadequate devices for modding signals, and the general head scratching that i've been doing. These guys (http://www.hptuners.com/order.php) seem to have a pretty good product and I will be contacting them to see if I can rebuild the fuel maps on cars to accomplish predictable results. I'll let you know


I looked at that product and it is very expensive, not to mention that you have to buy credits to tune vehicles. Could be very expensive if you had to retune several times. You should look into the free software that is out there, from what I have read on some of them they work very well and hardware needed is about the same price as what hptuner wants for their base program.
03-25-2008 08:22 AM
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Sartech Offline
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Post: #3
RE: sensor mods for 98 suburban-5.7l 1/2 ton 4wd
xcite Wrote:Quote;

Am seriously considering taking a huge step and moving into the full scale ECM programming arena. This will alleviate all these concerns with sensor mods, inadequate devices for modding signals, and the general head scratching that i've been doing. These guys (http://www.hptuners.com/order.php) seem to have a pretty good product and I will be contacting them to see if I can rebuild the fuel maps on cars to accomplish predictable results. I'll let you know


I looked at that product and it is very expensive, not to mention that you have to buy credits to tune vehicles. Could be very expensive if you had to retune several times. You should look into the free software that is out there, from what I have read on some of them they work very well and hardware needed is about the same price as what hptuner wants for their base program.

Can you send some links of any that you know of?
03-25-2008 11:29 AM
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xcite Offline
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Post: #4
RE: sensor mods for 98 suburban-5.7l 1/2 ton 4wd
http://www.moates.net/

Has hardware and blank chips, ect. Also lists some software.

In their documents section there are several how to quides and more. There is also many sites listed on their links page.

Hopefully this helps you out some. Alot of reading and learning to start reprogramming chips ect.
03-25-2008 01:39 PM
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