What to do with my two Marks
- Thread starter treysviii
- Start date
Haha, definitally NOT under thinking it.
I was thinking that if you set the cruise on the "non calibrated" car it would have affected the entire comparison, expecially if you set each car to 60mph, you wouldn't be able to pace each other and than the rpms would have been off.
Did you guys ever notice how you're MPG on the message center doesn't change in different gears? As long as the throttle position stays the same, the MPG stays the same no matter what gear you're in. Strange, haha.
Go test it...turn on your instant MPG and drive in o/d, hold the throttle steady and turn off o/d, your instant won't change. The load isn't really different, per say, but you'd think that with the higher RPMs(expecially with your guy's IMRC theory) that your instant MPG would drop. More air more fuel, but I guess the computer doesn't read the MAF perameters. Huh...
I was thinking that if you set the cruise on the "non calibrated" car it would have affected the entire comparison, expecially if you set each car to 60mph, you wouldn't be able to pace each other and than the rpms would have been off.
Did you guys ever notice how you're MPG on the message center doesn't change in different gears? As long as the throttle position stays the same, the MPG stays the same no matter what gear you're in. Strange, haha.
Go test it...turn on your instant MPG and drive in o/d, hold the throttle steady and turn off o/d, your instant won't change. The load isn't really different, per say, but you'd think that with the higher RPMs(expecially with your guy's IMRC theory) that your instant MPG would drop. More air more fuel, but I guess the computer doesn't read the MAF perameters. Huh...
First off, you keep assuming the IMRCs regulate air delivery. The air volume is the primary function of the throttle body. The IMRCs dictate air velocity more than air volume. At lower rpms the air is closed off in the secondary ports forcing the velocity to be increased and flow volume is sacrificed. At higher rpms, the secondary ports open allowing maximum flow and velocity is sacrificed.
Second, the message center does not "measure" the fuel, it calculates from what the fuel tables in the PCM are at the time of the fuel demand and issues a fuel flow voltage 'signal'(~2 to 12 VDC) from those parameters to the message center...
Since no rpm signals are utilized in the economy calculation, the gear selection will not matter.
You were right, just for the wrong reason.
They DO regulater air delivery.....to EACH cylinder!
So....if you're cruising with a 30% TPS position in O/D and you turn the O/D off and the rpms go ABOVE 3250, the IMRCs open(still doesn't seem right), you're mpg should go down, right? More air into the cylinders, more fuel.....When I first figured this out, I thought I was "tricking" the message center and I wasn't getting "exact" mpg figures.I knew this much....I was just saying that with higher rpms, you'd think the engine would use more fuel, in turn lowering the MPG. I think the PCM uses the VSS and TPS sensors MAINLY for signal, but thats just an assumption. I was also thinking it might use injector pulse width but it would probably "know" that info based on the voltage/load% of the TPS.
We actually paid no attention to MPH because MPH was a moot point in what we were seeking.
We put both cars on cruise and matched speeds, the actual speed was irrelavent.
Then in the stock geared car we turned the OD off and compared RPM's as measured on the TACHOMETER, which again is not really relevant to "SPEED or MPH".
The reason for purley for curiosity because people are always asking the question,
"how many rpms are you turning at X MPH"?
we were trying to come up with a solution that was easier to understand and to pass along to other folks, WHILE satifying my/our own curiosity at the same time.
When people wanted to know if 410's were "too steep" for hiway use now it's easy for them to determine for themselves.
Go out on the freeway
Set cruise to desired speed
Turn off OD..
If that RPM isn't too high then 410's will work for you.
Same for 373's
307 to 373's are less of a change than turning your OD off on a stock geared car.
I can assure you the PCM pays particular attention to MAF parameters, extensively, not only in engine management but also proper transmission function as well, you guess wrong.
I'm not sure I understand what you are saying though in regards to the the instant MPG scenario
If I go 60MPH with cruise on and switch from 4th to 3rd it drasticly affects my instant MPG as displayed on the message center.
Of course the throttle position increases as the cruise control matches the RPM's required to maintaind the desired speed.
Now is what you are saying is "at a non particular speed" at a steady throttle position if I switch from 4th to 3rd gear my instant MPG will stay the same?
If I dont change the throttle position when switching from 4th to 3rd, isn't the car going to "decelerate"? to a lower MILES per hour? MILES being the key word as that is what the message center is referencing.. MPG.
I think your drawing to many variables into the equation, hence my confusion.
I wasn't talking about the PCM watching the MAF..I know these cars rely VERY heavily on the MAF sensor, I was talking about the PCM using the MAF readings to estimate the instant MPG on the message center....which was the topic at hand.
I think I'm MAJORLY confusing you XLR....all the MAF talk has you overthinking what I'm thinking, haha. Go out and try it, maybe its just a Gen 1 thing, but you can have the car in ANY gear at a certain speed and no matter what the rpms are, the position of the throttle seems to mediate the instant MPG. Like I stated above "if you're cruising with a 30% throttle position and you shift gears, the MPG will stay the same in 3rd vs O/D" I'll go video tape it.
Yea you got me confuzededed..HAHA
last night I made some changes to my tune and went for a short ride.
I thought about what you had said and..tried it.
I saw almost exactly what you described, ya..that's weird.
I did the same sceanrio with cruise control on and it did like I said.. made a huge difference in the instant.
atleast i'm not confused... now
Thanks for the inciteful, thought provoking conversation!
Trey? are you still reading this thread or have we hi"J"acked your thread into oblivion?
HAHA
Hi"J"acked!
last night I made some changes to my tune and went for a short ride.
I thought about what you had said and..tried it.
I saw almost exactly what you described, ya..that's weird.
I did the same sceanrio with cruise control on and it did like I said.. made a huge difference in the instant.
atleast i'm not confused... now
Thanks for the inciteful, thought provoking conversation!
Trey? are you still reading this thread or have we hi"J"acked your thread into oblivion?
HAHA
Hi"J"acked!
LMAO, I find it very easy on this site to get off track, haha.
Now you see what I'm talking about...its hard to describe, but its almost like you can "trick" the message center. With cruise on, its trying to match your speed when you shift, but without cruise on there is a small change in speed, but keeping your foot in the same spot keeps the throttle % the same, hence the same MPG. Strange, haha.
Is yours a Gen 1 or 2?
loupalskip
Registered
Don't feel bad about the sunroof. They all eventually have problems (electrical, or simply leaking). So, if yu're planning on keeping the car for awhile, you're better off without the sunroof.
I've met trey, and even in his drunkest hour "just before new years eve" he never struck me as a liar.
I did the math came up with 31ish MPG.
with my 373's I could do that on a road trip if I kept my speed below 65.
At 65 my gas mileage goes to CRAP
Below 65 I can reset the average and it'll be a long time before it falls below 30MPG with the AC off.
I did the math came up with 31ish MPG.
with my 373's I could do that on a road trip if I kept my speed below 65.
At 65 my gas mileage goes to CRAP
Below 65 I can reset the average and it'll be a long time before it falls below 30MPG with the AC off.
I got 29.2 on a trip from Santa Rosa to Lincoln (just north of Sacramento) obeying, for once, all speed limits. As anyone who has made that trip knows the milage takes a hit coming from marine world onto 80. Give me a flat road and I'd hit an average of 35-36 easy. When I owned the "land shark" I got 27.7 round trip Santa Rosa to Reno and I wasn't paying attention to the speed limit, so I believe 31-33 is real.
Yeah, the mpg is real...but 600 miles for 18gallons is hard to believe, and thats using every bit of gas! I could imagine it if he was taking the trip freeway only, but any city driving to stop for food/gas/restrooms would change that number substantially. And...if he did hit the city, he'd be getting 40 mpg on the freeway than, haha.