BC

Yeah, you know, you'll really have to pardon me for that man. I just thought everybody should know about that New citrus additive to the gasoline that was supposed to add 500rwhp was just orange juice.... And that it was much cheaper from Walmart and actually added 600.

But my car got the runs, so....

sjsj

While I am pending an answer to "are new forum members welcome with new ideas" I'll assume the answer is Yes. So with that distraction aside, I'll repost the initial information posted so we can stay on topic, with the corrections to some information provided.

Q: Is there a cheap way and easy way of retuning air/fuel ratio [and if necessary timing] of cars when changing the intake, exhaust, fueling or combustion point [eg: exhaust, headers, boost, better-flowing MAF, firestorm plugs, water injection, etc]?

A: Here's a couple of suggestions of how this could be done on a 928.

1/ If requiring a scientific approach to the tuning process, the narrow or wideband sensor output should ideally be logged against RPM using a analog data aquisition device like the cheap DataQ [$25/50US DI-194RS/DI-148U $50US] on Ebay.

A practical example of this is shown the URLS below:
http://cyberdave.org/CarTest.html
http://cyberdave.org/carwb.html

Shareware/freeware to be used with the DataQ device is available at
http://www.ultimaserial.com/
http://groups.yahoo.com/group/ultimaserial_group/

2/ A cheaper way is to do open-loop tuning while monitoring the O2 sensor signal. Disconnecting the o2 sensor so car goes into open loop tuning [no O2 sensor correction, just using MAF/throttle position,.etc], then monitor the o2 sensor signal with a digital voltmeter for appropriate air/fuel ratio (AFR) at various different throttle positions (eg: increments of 500rpm). Adjust the MAF signal using techniques presented below until appropriate AFR is obtained. With normal plugs this may be between 12:1 - 16:1 depending on desired fuel/economy or performance. 14.7:1 being the point of minimal exhaust gas emission.

A table of O2 sensor voltage to air/fuel ratio http://wbo2.com/sw/20-tables.xls. "Nbsim" is the O2 sensor output voltage for row for corresponding Lambda and AFR presented. The NBsim worksheet providing a at a glance representation.

3/ Modifying the the timing and fuel maps can be performed a number of different methods. Three are presented below:

[i] Cheapest/easiest way way would be adjust the timing via the distributor position and adjust the fuelling curve for O2 signal and MAF signal using:

* O2 signal, for constant cruise conditions: a free mixture controller schematic is available at http://better-mileage.com/memberadx.html which changes the stoich point of a narrowband O2 sensor. Combined with water injection the author of the website claims 18% improvement in fuel economy!!

* MAF signal, for changing throttle conditions: cheap Jaycar Digital Fuel Adjuster (DFA) or or more expensive Apexi SAFC-II device on Ebay. DFA is in my opinion better as it provides up to 128 points of adjustment between 0-5V as explained at http://autospeed.drive.com.au/cms/A_2418/article.html. Available as self-build kit at URLs below:

[US/Canada]
http://www.jaycarelectronics.com/pro...Max=&SUBCATID=
$51US
http://www.jaycarelectronics.com/pro...Max=&SUBCATID=
$38US

[AUS/NZ]
http://www.jaycar.com.au/productView...Max=&SUBCATID=
$80AUS
http://www.jaycar.com.au/productView...Max=&SUBCATID=
$60AUS

[ii] megasquirt internet/forum developed ECU in piggyback mode using software provided. The fuel maps responding to the O2 and MAF signal. The great thing is megasquirt can be later extended to provide the ultimate tuning device: FULL ecu control of the fueling and timing, use wideband sensor input to allow self-monitoring of an AFR and can use A MAP sensor instead of a MAF. All available at a later date if comfortable in doing so. Less than $500US built. See http://www.megasquirt.info

Other piggyback or standalone ECUs are available too. Motec, Haltech, Autronic, Wolf3D. A good price/performance point being the PerfectPower SMT6/SMT7 piggyback ECU.

[iii] sharktuner to change existing eeprom ECU fuel maps. As per https://www.928gt.com/p-40359-928-sh...87-95-928.aspx
Pro: Cool idea, uses existing ECU, no wire cutting necessary
Con: bloody expensive ($1700), unless you loan out the equipment from someone. No idea of what the loan price is. Tuning limited to ECU capabilities designed a few decades ago. Also no ignition mapping abilities.

BC

The MS and the Sharktuner are the only things there that are not line conditioners, barring the 25 dollar data logger.

And since you're going to repost something 5 freaking inches down from where you did the first time, here you go.

SharkSkin

What new ideas? Sorry, I seemed to have missed that part.

Also, a note on culture. You mention "cheap" 5 times in your post. Quite frankly, the majority of people here with any interest in altering fuel/ignition maps will perform such tuning with the help of a dyno and/or a known, respected expert. When offered a "cheap" way to push the envelope, most will say, "yeah, but how cheap is a rebuild?". Answer: Not very cheap, you could blow up a couple Chevy motors or several Honda motors for the same money.

Most folks who have 928s whether they mod them or not are far more interested in doing things "Right" and value that over doing things "Cheap". IMHO there is nothing at all wrong with anyone presenting information here, different viewpoints are always welcome. I'm just trying to put it into perspective for you -- you will find a limited attention span here with regards to half-measures and/or methods that are not applicable to the car being discussed.

For example, I don't think that any of the 928s that have MAFs have distributors of a type that permits alteration of timing. I could be wrong, but if I am then cars that fit that description are the exception rather than the rule.

Bill Ball

sjsj:

You've thrown a lot of stuff out there about cheap and easy ways to do things - expect scepticism, even major scepticism. Also, you've made some statements that lead me to believe you are fishing for flame job a bit. Things like:

"* Tuning can be done without dyno and cheaply so, RE: Dataq, wideband. Easiest is using the stock O2 narrowband sensor and voltmeter." - Go read Louie Ott's extensive posts on this and tell us why he is all wet. He has tuned more parts on a 928 than just about anybody else and he has the engineering background to substantiate what he says.

"* Go too far and allow the knock sensors to kick in, no boom necessary, other than the loss of breath you get from fearing the boom whenever you turn the key." - Sorry but people with functioning knock sensor have blown up these cars. The knock sensor is not going to take care of serious detonation.

If you want to take my remarks as a hostile response and get your feelings hurt, fine. You're as welcome here as anyone else. Just understand that your somewhat cavalier, why can't people just accept new ideas presentation doesn't give you instant credibility. You may know exactly what you are doing. If so, then when questioned by us numnuts here, tell us why we are wrong rather than just get hurt.

I'm listening. If you can turn us on to some easy, cheap new ways that really work, fabulous. Don't give up if you think you are right just because you've encountered resistance. But don't just sit there and imply we are a close-minded group aiming to drive out anyone who spouts a new idea. We buy lots of new ideas for our cars all the time.

sjsj

Your words, not mine. Hurt? You wish mate. Disappointed, yes, is heresay rather than any proof.

For the rest of us that do appreciate such information, can a clear passage way of communication be provided that remains ON TOPIC? I believe that was the intent of a forum. If I am mistaken in believing this is an open forum of such discussion, please correct me. Again, the initial question stands "are new forum members with new ideas welcome here?" I'd like to add to this "and are appreciated here?". Unless the Gods of Porsche 928 have spoken and their word IS the truth and all should obey.

On TOPIC:
Have a read if you missed in the previous two times it was posted. A practical example of using "cheap" DataQ and a wideband sensor for DIY tuning without the need for a dyno, or fear your car is gonna blow up like that picture of a nuclear detonation, is shown the URLS below:

http://cyberdave.org/CarTest.html
http://cyberdave.org/carwb.html

Results and on topic discussion welcome. Any misnomers to rules. regulations and hierachy please take offline via private messaging for the sake of other forum members, if you value open ON TOPIC communication.

sjsj

AO

sj-

This is the 928 forum. If this is not specific to the 928, you should post to the Off Topic page. But you'll have to pony up the $20 or so to access. Let us know when you get your first 928.

sjsj

Some of the tuning steps presented are generic and apply not only to the Porsche 928, but do to any MAF, narrowband O2 sensor, ECU and fuel-injector equipped vehicles. That would mean quite a lot of early to mid-90s till today. So feel free to cross post to the other Porsche forums, or your Corvette, Ford, GM, Toyota, Nissan forum. The latest cars differing by changing the MAF to a MAP sensor and a handful incorporating wideband O2 sensors. There is no copywright on the summary of materials presented.

What is different from vehicle to vehicle is the ability to tweak the existing ECU fuel map based on how locked down it is. Sharktuner being the IMHO rather expensive choice for the Porsche 928 owner to change fuel maps while retaining the stock ECU with no need for piggyback ECUs. Megasquirt or the Jaycar DFA representing much better tuning value. The DFA being more limited in it's scope [see autospeed URL about it to know what it does and it's limitations].

I do not benefit from the sale of any of such items. Simply sharing the love of cars and how to easily and convenient tweak them for maximum performance/economy, upgrade their computer management to the 21st century, without allowing money to get in the way of a learning experience.

sjsj

John Speake

Hi Stirling,
You are correct, the Sharktuner does not have EZK remapping at present, this is being worked on at present. I agree that there probably won't be an Autotune facility on ignition timing - does anyone else offer that ?

Hi sjsj
If you think a SharkTuner is expensive, then you value our time very cheap ! The price reflects the substantial development time and the limited market. I will never make any money out of it to repay what we have put into it.

chris0626

sjsj,

Of course new ideas are always welcome.

But, as been said before, most are not willing to risk a motor of the 928's value to 'try' something that may or may not work. A typical rebuild on a 928 V8 has a substantial increase in cost over a comparable Chevrolet or Ford V8 and the parts aren't 'quite' as readily available (you can't buy rebuild parts at your neighborhood Pep-Boys).

A real EMS is only gonna cost in the neighborhood of $2k (if you wire it yourself) and the dyno-time can be had for less than 1/2 that. A very worthwhile 'proven' investment... and a rather insignificant amount in the grand scheme of things.

Cheap and 928 are 2 things that just do not go together.

sjsj

A good reason to loiter here then.

I do value the concern you place and no doubt others do too.. However, I , who could also be grouped into the "most" group, DO value such information as presented AND (as it is simply a summary of bits and pieces I've been exposed to), am aware that it is a rather inexpensive solution AND know first handedly that the DFA does work with ANY MAF equipped car.

Observing it's limitations, it provided a very cool solution indeed, with minimal risk if tuning along the 14.7:1 ratio with good coolant and good oil.
...
A new idea for you: "inexpensive and SAFE tuning IS available for the 928".

sjsj

Louie928

Since you know first handedly that the DFA will work with ANY MAF equipped car, I suppose you also have it figured out how to make it work on the 928. The 928 MAF outputs more than 5 volts, and unless I misread the data, the DFA does not. In fact of all the fuel injection tuners you mentioned, I don't believe any of then put out more than 5 volts except the Perfect Power SMT. I worked with Klaus from Perfect Power to develop the SMT-5 so it would work with the 928 and it took a lot of convincing him that the 928 did indeed need more than 5 volts. Tom Cloutier and I demonstarted that to him on a dyno. When he saw it, he believed. The SMT-5 and later the SMT-6 will work with up to 10 volts of load sensor output.

You mentioned about tuning the A/F ratio using the narrow band O2 sensor and a digital meter while driving with the sensor disconnected from the LH. Tuning the A/F on the road while monitoring the O2 sensor is possible and you can get a fairly close max power mixture reading. You can't really use a digital meter because the reading is jumping around so much you can't readily discern the 0.02 to 0.03 volt differentiation (with narrow band O2 sensor) you need to be within for best power A/F ratio. The RPMs are changing so rapidly you can't make much sense of it to get a relationship of mixture vs RPM.. It's much better to make a run and log RPM & O2 sensor voltage and analyze later. The SMT-6 will do that as well as any number of other data loggers. Make mixture tuning corrections and try again. Simple disconnecting the O2 sensor doesn't make the LH run in open loop in any useful manner. The LH will run open loop, but it's done differently.

As for the "Firestorm", the web site is quite a hoot to read. Lots of words, but no information of any value.

Run with A/F ratio of 24:1? You could get an engine to run that lean with a compression ratio of around 18 - 22:1. They are called diesels and can burn french fry oil and need no spark plugs. They actually work pretty good.

One thing to remember is that the 928 in stock form is already tuned very close to optimum. Those Porsche engineers were no dummies. You can tune timing a little closer to the edge and extract a litttle more. Mixture tuning doesn't get a lot more power since it isn't very critical except for needing rich at the top end of the power range for thermal safety. Until you do other things to the engine to get it to pump more air, and the stock A/F map doesn't quite fit anymore, you won't get a lot of gain. Some of the MAFs are getting "long of tooth" now and are no longer well calibrated so with some tweaking of the mixture performance can be restored.

sjsj

The DFA can be considered a general purpose voltage remapping device. It works within 0-1V (so can modify an O2 sensor signal), 0->5V and 0->12V range as per article http://autospeed.drive.com.au/cms/A_2418/article.html . From my experience it can also be set to intermediate ranges such as 0->6V for instance by changing the adjusting the onboard adjustable potentiometers.

The DFA allows +50% and -50% adjustment of a signal at any of it's points along it's range. The only thing it doesn't do is invert the signal if you are for instance mapping 0-5V to 5-0V, as is the case for me changing from a AFM to a MAF, yet the ECU still requires an AFM type signal. I'm playing with my DFA to do this.

sjsj

Imo000

I have this weird feeling that you have been kicked out off other boards for acting like a "know it all".

Keep mentioning the that you have first hand experience with some of these products. Tell us more about it. About the engines you built and not the shamelss plugs you keep pushing here. Let's see that resume of yours!

FlyingDog

...don't forget the pictures!