View Full Version : For a fee...(I want to blow up your CX-7)...One of many Juan threads of doom
Before I purchase a CX-7 I would like to know how much additional FE could be attained via permanently "wiring" the wastegate fully open. Anyone in the Seattle eastside willing to provide a CX-7 test mule for a reasonable fee..??
Owner drives, I simply provide the fee, the modification and complete restoration in return for a detailed MPG record of your normal everyday driving.
bscar
12-27-2008, 08:20 AM
If fuel economy is the only thing you're thinking about, why are you looking at an SUV-type vehicle? Go buy a Prius or a TDI New Beetle.
ottoblotto
12-27-2008, 12:03 PM
i drove a 2.0l tdi audi a4 in germany about two weeks ago. went 300+ km and only used about 23liters of diesel. ya, that IS the way to go... oh did i mention i was averaging 160kph? mmm... audi... NOT OFFERED IN THE STATES! :(
If fuel economy is the only thing you're thinking about, why are you looking at an SUV-type vehicle? Go buy a Prius or a TDI New Beetle.
"If fuel economy..."
If fuel economy were the ONLY thing that I'm interested in I would OWN a Prius....
Oops, sorry, I already own one of those....
If the Lexus RX had the SH-AWD system, and the CX-7 DFI engine, my interest would PEAK. Good looking upscale SUV, STELLAR AWD system and decent FE with the turbo wastegate wired open.
Actually I would probably purchase the visually appealing CX-7 if it had the SH-AWD system. But then I would immediately set out to modify the DISI engine to not bring on the boost so quickly if the gas pedal were s..l....o........w........l..........y depressed.
yellowbee
12-27-2008, 01:01 PM
I don't understand why you don't just get an Acura RDX. It has the AWD that you want and is essentially the same car as the cx-7 for alot more $$.
I will admit that the navigation and voice recognition works 10x better than in the cx-7 though.
Superstretch18
12-27-2008, 02:12 PM
I just want to say that this is not a mcx7.com endorsed activity. If anyone goes through with this, the forum is not responsible for the results (positive or negative). I will admit it's an interesting experiment though...
Juan, it might be helpful for those even considering this for you to list your qualifications/previous experience in doing this type of work.
Alpha Wolf
12-27-2008, 07:48 PM
Why do you guys keep responding to this guy.
He does not own a CX7 nor will he. He is just jacking everyone around here wasting space and time.
I don't understand why you don't just get an Acura RDX. It has the AWD that you want and is essentially the same car as the cx-7 for alot more $$.
I will admit that the navigation and voice recognition works 10x better than in the cx-7 though.
CX-7 simply has more visual appeal for me vs RDX.
RDX dash is too busy/complex.
DFI is a significant technological advance.
Provided I can avoid it I will NEVER again buy a captive GPS/Nav. Only got the one in the RX because of "package" bundle.
MAZOOM
12-27-2008, 11:03 PM
lol
Experience....
wwest at Strobedata.com
or Google images:
willard west
ottoblotto
12-28-2008, 04:13 AM
Why do you guys keep responding to this guy.
He does not own a CX7 nor will he. He is just jacking everyone around here wasting space and time.
dont be so harsh. he is looking for a new car and is interested in the one that most of us on this site have spent the time and energy to research. i know it took me a few months of research before i finally decided on the cx7, and so far im pretty happy i did.
let him post here so i can get my laugh on!
juan, i dont think you will have much luck on finding someone that is willing to partake in your experiment. if you really want to find out these things, go get a grant, buy a cx7 and do the tests yourself. if your tests ruined someones engine, would you buy them a new one? warranties are at jeopardy, money spent, loss of transportation, ect ect ect...
"If your tests ruined...."
Personally I suspect anyone agreeing to the deal might not only have a keen interest in the outcome but have a substantial enough knowledge about what is being done to understand the risk, or lack thereof.
I know I'm not considered to be very bright around "here", but I fail to see how eliminating the boost "feature", or mostly so anyway, of a turbocharged engine might/will damage the engine, short term or long term.
It seems to me that the modification is much more likely to extend the engine life than otherwise.
Oh, we once flew our T210 to Reno from Seattle just after a 100 hour inspection and only on the ground in Reno did we discover the cause of the niggling engine problem. One of the "hose clamps" allowing the intake manifold to be pressured was left loose.
Tightened the clamp and went on the Los Vegas, Amarillo, Memphis, Wichita, home.
Don't remember now how many hours we put on that engine afterward but I do know it was substantial and WOULD remember if an engine failure had resulted....
Oh, those were the days, '78(??) when it was legal to fly below the canyon rim which is what we did for the first hour or so upon Los Vegas departure, BEAUTIFULL scenery.
Raider
12-28-2008, 02:25 PM
I would think that is the wastegate is 100% open, you will not have any boost.
Unless you have a standalone, I'm sure doing this will cause some problems/CELs. The ECU will be expecting boost, and with it not there, your timing and fuel will be off.
MAZOOM
12-28-2008, 04:58 PM
Not to mention it would still run rich under WOT.
Unless you have a standalone, I'm sure doing this will cause some problems/CELs. The ECU will be expecting boost, and with it not there, your timing and fuel will be off.
The ECU has, will have, NO expectation of boost.
With the throttle wide open, or nearly so, the ECU responds ONLY to the engine RPM & temp and the MAF/IAT sensor outputs. And of course the knock/ping sensors.
Not to mention it would still run rich under WOT.
Under acceleration the MAF/IAT sensors are the SOLE determinants of the amount of fuel injected into each cylinder. At idle and cruise the upstream oxygen sensor(s) are the sole A/F mixture determinants.
The ECU will NOT enrich, overly enrich, the mixture absent a flaw in the MAF/IAT or the upstream oxygen sensor(s).
The only function of the turbo is to "bring"/force more airflow through the MAF/IAT intake aperture/opening.
MAZOOM
12-28-2008, 10:29 PM
No.. on this car part-throttle it runs lean, WOT it runs rich.
No.. on this car part-throttle it runs lean, WOT it runs rich.
Well, yes...
At idle or in cruise mode, non-acceleration, the ECU relies on the upstream oxygen sensor(s) to determine the optimal, for emissions purposes, A/F mixture ratio. Neither LEAN nor RICH, just simply right in line, on the cusp between rich and lean.
Depress the gas pedal enough to indicate to the ECU that you desire a RISE in engine RPM and the A/F mixture control switches over to the use of the MAF/IAT for controlling the A/F mixture within a tight range around 12:1.
Running LEAN would imply not enough fuel to completely use, burn the available oxygen, a highly undesirable condition if you wish to hold emissions within reason and keep the catalyst "alive".
Take note that the actual compression ratio is not really a consideration when running a stoichiometric mixture ratio. On the other hand open the throttle a bit and now you're more fully filling each cylinder, the compression ratio begins to come into play, and the mixture must be changed accordingly to avoid knock/ping.
MAZOOM
12-29-2008, 01:12 AM
A/F mixture within a tight range around 12:1
The DISI runs no where near 12:1 when you're at full-throttle.
ottoblotto
12-29-2008, 02:31 AM
Well, yes...
At idle or in cruise mode, non-acceleration, the ECU relies on the upstream oxygen sensor(s) to determine the optimal, for emissions purposes, A/F mixture ratio. Neither LEAN nor RICH, just simply right in line, on the cusp between rich and lean.
Depress the gas pedal enough to indicate to the ECU that you desire a RISE in engine RPM and the A/F mixture control switches over to the use of the MAF/IAT for controlling the A/F mixture within a tight range around 12:1.
Running LEAN would imply not enough fuel to completely use, burn the available oxygen, a highly undesirable condition if you wish to hold emissions within reason and keep the catalyst "alive".
Take note that the actual compression ratio is not really a consideration when running a stoichiometric mixture ratio. On the other hand open the throttle a bit and now you're more fully filling each cylinder, the compression ratio begins to come into play, and the mixture must be changed accordingly to avoid knock/ping.
um... what?
The DISI runs no where near 12:1 when you're at full-throttle.
So, "where"......does it run...?
Superstretch18
12-29-2008, 01:43 PM
So, "where"......does it run...?
Closer to 10:1 at WOT...
here's one.... 9.6:1
http://i529.photobucket.com/albums/dd334/VMS_Cue/AFR-964.png
MAZOOM
12-29-2008, 04:29 PM
Pig rich!
Sorry, I don't understand the chart/graph.
It seems to be indicating that at sample 204 the A/F sensor (SENSOR..??)readout is 9.64. Being as how THERE IS NO A/F ratio "sensor" I fail to understand. You might be able to compute the A/F ratio from the output reading of other sensors, fuel pressure, duty cycle of injectors, cylinder pressure (oh, sorry, no sensor for that, another computed "sensor"...??) intake manifold pressure...
Hmmm..
Does your recording device "know" about DFI...??
Or was this "all" based on the SFI assumption...??
Superstretch18
12-29-2008, 10:38 PM
Sorry, I don't understand the chart/graph.
It seems to be indicating that at sample 204 the A/F sensor (SENSOR..??)readout is 9.64. Being as how THERE IS NO A/F ratio "sensor" I fail to understand. You might be able to compute the A/F ratio from the output reading of other sensors, fuel pressure, duty cycle of injectors, cylinder pressure (oh, sorry, no sensor for that, another computed "sensor"...??) intake manifold pressure...
Hmmm..
Does your recording device "know" about DFI...??
Or was this "all" based on the SFI assumption...??
O2 sensor #1 is a wideband, so it can record accurately enough to reliably calculate the A/F ratio. The device is a dashhawk and it is recording directly from the OBDII port. Seeing exactly what the ecu sees. MSD programmed this PID specifically for the Mazdaspeed (& CX-7) application. I would say it's damn accurate...
Re: Reading the chart. Red line is rpms, along with the associated red scale on the left. Teal line is A/F ratio; teal scale on the right. If you follow the line, you will see that A/F ratio trends (in this example) to about 9.6:1, with a little variation, of course.
For the record, at cruise the ecu is shooting for just about stoimetric...
Why do you guys keep responding to this guy.
He does not own a CX7 nor will he. He is just jacking everyone around here wasting space and time.
This is getting ridiculous....
Superstretch18
12-29-2008, 11:30 PM
This is getting ridiculous....
+1
I'll keep watching the threads, but this is me turning off:
***
O2 sensor #1 is a wideband, so it can record accurately enough to reliably calculate the A/F ratio.
Prior to wideband oxygen sensor development the upstream oxygen sensor had only a "binary" output that was used to keep the mixture at the stoichiometric level. These early sensors were of the "on" or "off" sensor type, the presence of oxygen or not. So to provide accuracy, resolution, of A/F mixture measurement the ECU varied, "dithered", the A/F mixture back and forth (very slightly) between "rich" and "lean" using PWM of the injectors. If the resulting sawtooth waveform wasn't "seen" in the oxygen sensor output then the appropriate mixture corrections were made depending on the sensor output being "on" ("some" oxygen in the exhaust), or "off" (no oxygen).
With the advent of the development of the new wideband sensors there is an analog output from the upstream oxygen sensor that denotes the level, within a fairly narrow range(***), of oxygen remaining in the exhaust gases. So the dithering of the mixture is no longer required.
Now, anyone who has advised you that the new wideband oxygen sensors can be used to "measure" the A/F mixture ratio is quite bonkers IMMHO. They can be used to detect, within a very narrow range, how much oxygen remains in the exhaust but with a mixture of even 12:1 there would be NO oxygen left in the exhaust, only unburned hydrocarbons.
But as one can readily see even were the analog output such that it could be used it still goes "blank" when there is no oxygen left to burn in the exhaust stream, which is ALWAYS the case when the mixture is "rich" beyond the stoichiometric.
The device is a dashhawk and it is recording directly from the OBDII port. Seeing exactly what the ecu sees.
Please take note that the engine control ECU has no reason, basis, for computing the A/F mixture ratio. On the other hand it is an important sales and/or marketing aspect of your data logging instrument and so who is to care, one way or another, of its accurracy..??
MSD programmed this PID specifically for the Mazdaspeed (& CX-7) application.
And I would bet good money that were you to ask they would tell you that the "firmware" in your Dashhawk is a production prototype, if not just simply a prototype.
I would say it's damn accurate...
Re: Reading the chart. Red line is rpms, along with the associated red scale on the left. Teal line is A/F ratio; teal scale on the right. If you follow the line, you will see that A/F ratio trends (in this example) to about 9.6:1, with a little variation, of course.
For the record, at cruise the ecu is shooting for just about stoimetric...
Yes, otherwise it would never get past the EPA for sales in the US
I'm not saying that a 9.64:1 is impossible, say in a drag racer, but given the "net" compression ratio, native + boost, and direct fuel injection advantageous aspects of the CX-7 engine I would guess that the "standard" POWER mixture would suffice.
Another possibility is that the vehicle was somehow modified in a way that the RICH mixture HAD to be used to prevent knock/ping.
Why was the data logging run made, for what purpose..?
***the MAF/IAT module signals, NOT the A/F mixture oxygen sensor(s) are used to "control" the A/F mixture with the engine under any level of loading wherein the mixture must be enriched above the stoichiometric level.
Superstretch18
12-30-2008, 12:52 AM
I know I said I was bowing out, but this:
Please take note that the engine control ECU has no reason, basis, for computing the A/F mixture ratio. On the other hand it is an important sales and/or marketing aspect of your data logging instrument and so who is to care, one way or another, of its accurracy..??
This is the dashhawk calculation vs. an NGK tailpipe sniffer:
http://www.redcx7.com/images/read-1.jpg
Just a tidbit, but that's all I'll offer. Whatever you want to believe is fine by me. I will offer though that the Infinity EX35 is a very nice vehicle. NA from the factory, but not DI; well worth a look though. Now, I'm officially done. Have fun everyone...
now, i'm officially done. Have fun everyone...
+1...
Note that I have never said that the, any, OBDII reading device, data logging device, could not display a calculated AFI, fairly simple task/calculation, especially with the engine at idle or with light/constant loading, wherein the EPA DIRECTS what the AFR must be within a VERY TIGHT RANGE.
Just to clarify what I have said...The ON-BOARD engine control computer has no need for calculating AFR...At idle or cruise its task is to keep the upstream oxygen sensor signal within certain tight bounds. The result of that control, obviously, will be something very close to a stocihiometric ratio.
Now, if a device manufacturer wanted to work from that point, say use it as a reference, and calculate an approximation of the AFR with WOT all the to max RPM, who is to question the resulting "numbers", what would be the factual basis for ANYONE to question the calculation.
So yes, ANY ODBII reader worth its salt would know to display a 14.7:1 mixture ratio with an engine idling and the upstream oxygen sensor signal within an acceptable. range.
http://www.max-boost.co.uk/max-boost/internet_articles/Air%20fuel%20metering.htm
Good read, maybe even GREAT.
shadow1
01-03-2009, 02:50 PM
OBDII regulations only measure emissions under closed loop (not WOT) conditions. At WOT, OBDII emissions controls are no longer in effect. And yes, the CX7 like most turbo vehicles runs rich under WOT conditions.
Do you know...
A thermometer can be calibrated at home with two simple procedures.
An ice bath/bucket, properly prepared, for the 32F "point".
Boiling water for the 212F "point".
You can even calibrate an RH "meter" with a bit of salt and a small enclosure.
So, any A/F mixture reading with the engine running and the upstream oxygen sensor(s) "satisfied" had best indicate, compute, a stoichiometric reading.
"closed loop and open loop" terms are no longer valid.
Methinks the "open loop" term with regards to A/F mixture is an obsolete term left over from the days that only the oxygen sensor was used for engine "light load" conditions.
At idle and in cruise mode the A/F mixtures are controlled to/at the stoichiometric level via the upstream oxygen sensor(s). At WOT, or under extra engine loading, the A/F mixture is controlled, "closed loop", via the use of the MAF/IAT against the factory parametric mapping.
And I stand corrected. With a cold, COLD engine just having been started the A/F mixture under load might be in the range of 10:1 due to the poor vaporisation of fuel.
But I am still of the firm opinion that enriching a road-going vehicle beyond 12:1 in normal circumstances would be extremely unlikely.
shadow1
01-03-2009, 03:36 PM
Go read up on turbo engines and tuning if you do not believe that forced induction motors run rich. My Evo is tuned for approx 11:1 AFR under boost. Under cruise and idle the ECU keeps things stoichiometric. You are entitled to your opinion but I encourage you to read up on the topic.
gear head
01-12-2009, 01:59 AM
[ But I am still of the firm opinion that enriching a road-going vehicle beyond 12:1 in normal circumstances would be extremely unlikely. ]
You should try you're opinion out in the real world & see how long the engine lasts......
The extra fuel in a turbo engine is mainly for heat control. I've tuned my evo to 11:1 like the post above for safety.
shadow1
01-12-2009, 09:56 AM
Hey another fellow Evo owner!
gear head
01-13-2009, 12:26 AM
Yeah buddy, I love the little black 4 door:D
[ But I am still of the firm opinion that enriching a road-going vehicle beyond 12:1 in normal circumstances would be extremely unlikely. ]
You should try you're opinion out in the real world & see how long the engine lasts......
The extra fuel in a turbo engine is mainly for heat control. I've tuned my evo to 11:1 like the post above for safety.
In the "real world" the extra combustion chamber cooling via the vaporation/atomization of fuel sprayed directly into the combustion chamber allows the compression ratio to be raised to ~12:1.
Are we confusing compression ratio with A/F mixture ratio...??
shadow1
01-13-2009, 06:38 AM
No confusion. Go learn about forced induction.
No confusion. Go learn about forced induction.
In what context.... TC or SC...???
TC relies on using "waste" energy, or at least what was once thought of as "waste" energy. The new Atkinson engines are proving that one need NOT waste that energy.
SuperCharging, on the other hand, undeniably requires, uses, a portion of engine power to BOOST engine power....
SuperCharging has the advantage of providing INSTANT boost as soon as one opens the throttle above idle. The disadvantages, traditionally, being the need for a wastegate and/or a BOV, pressure bypass. Studebaker disproved the need for the wastegate approach clear back in the mid-fifties. Studebaker used a "CVT", variable V-belt engine drive.
It would be nice if, during compression within the cylinder, the mixture/charge could be "force" cooled. In the alternative a TC or SC can be used to partially compress the mixture/charge, then cool the now already partially compressed mixture before it even enters the cylinder via an intercooler.
The more compression you have that can be cooled before entering the cylinder the higher the cylinder's "effective" compression ratio might become.
Mazda Millennia "S" Miller cycle engine. Perfection would have meant varying the rotation rate of the positive displacement SC as a function of engine power requirements and LIMITS.
Back to Studebaker and their "CVT" driven SC.
DFI is simply a new, novel, way to "force" cool the atmospheric charge after FULL compression, cooling and ENRICHING just prior to ignition.
Someone is bound to soon come up with the idea of using "surplus" A/C capacity for cooling the 2000 PSI DFI fuel charge.
shadow1
01-13-2009, 07:49 AM
Your responses are about general tuning. Doesn't matter whether SC or TC in this context. There are textbooks on the subject.
gear head
01-14-2009, 12:00 AM
In the "real world" the extra combustion chamber cooling via the vaporation/atomization of fuel sprayed directly into the combustion chamber allows the compression ratio to be raised to ~12:1.
Are we confusing compression ratio with A/F mixture ratio...??
Not one bit, you were clearly talking about AFR.....
Do you know...
A thermometer can be calibrated at home with two simple procedures.
An ice bath/bucket, properly prepared, for the 32F "point".
Boiling water for the 212F "point".
You can even calibrate an RH "meter" with a bit of salt and a small enclosure.
So, any A/F mixture reading with the engine running and the upstream oxygen sensor(s) "satisfied" had best indicate, compute, a stoichiometric reading.
"closed loop and open loop" terms are no longer valid.
Methinks the "open loop" term with regards to A/F mixture is an obsolete term left over from the days that only the oxygen sensor was used for engine "light load" conditions.
At idle and in cruise mode the A/F mixtures are controlled to/at the stoichiometric level via the upstream oxygen sensor(s). At WOT, or under extra engine loading, the A/F mixture is controlled, "closed loop", via the use of the MAF/IAT against the factory parametric mapping.
And I stand corrected. With a cold, COLD engine just having been started the A/F mixture under load might be in the range of 10:1 due to the poor vaporisation of fuel.
But I am still of the firm opinion that enriching a road-going vehicle beyond 12:1 in normal circumstances would be extremely unlikely.
Why don't you do some tuning on you're own & actually learn rather than using the google machine.
Raider
01-14-2009, 10:28 AM
This thread is going nowhere. Original posted is not being discussed, and the thread has become of no value. I am closing this up to let it sink to the bottom and go away.
Raider
08-14-2009, 02:44 PM
Back from the dead, and part of our initial offerings in our Epic Fail section!