Tires have nothing to do with it. The gear ratio is the relationship of the engine RPM to the wheel speed as measured by the ABS sensors. I don't know which wheel is used, or if there is some averaging going on. The most correct would be the average of the driving wheels. The OBDII knows nothing about actual road speed.Speedy3 said:
MAZDASPEED 3 CAI Gains Comparison Depot
- Thread starter Speedy3
- Start date
Bast525 said:I wasn't arguing it, just said I thought I remember that. I do remember reading SOMEWHERE (maybe SCC?) about limiting in third as well. But that wasn't my point. My point was in reply to someone saying they saw less boost in 3rd than in 4th and up. And I was saying, this is normal. I've seen this on ALL turbocharged cars, whether they had a computer controlling the boost levels, or a simple ball-and-spring valve set manually with no computer control. I ALWAYS see higher boost in higher gears.
__________________
'07 Mazdaspeed 3, red, MS CAI only mod for now
SOLD: '05 Dodge SRT-4 (yes, a Neon), red, lightly modded
SRT-4 interiors are teh slow
Second toy: '07 Civic Si coupe (wife's car), red (the funny thing is I really don't like red....), stock (for now).
I know Bast. Sorry if I came across harsh...wasn't trying too.
True...true... I let my friend (he is a DC cop) drive it for the first time last night. He has taken several professional driving courses, so I know he could really handle the car. I told him to open it up and have some fun. He was grinning from ear to ear....he loved the car.
Rotus8 said:
Ah, Rotus, Rotus....As the tires wear, the numbers will change. Smaller circumference, faster they turn with the same engine RPM. Come on buddy, I know SW Engineering curriculum doesn't include dynamics, but you should have caught this!
This brings up a question I wanted to ask, but I don't want to sabotage this thread.
Does the ECU use the front tires, rear tires, all tires or the drive train to measure the speed that is reported on the OBDII?
(drinks)
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No, no, no. The engine turns the tranny and each gear has a fixed ratio to the output shaft. The output shaft of the trans has a fixed ratio to the axles. The axles are connected to the ABS wheel speed sensors. Done. No tires involved. The OBDII has no idea of the road speed which will be affected by the tires.Speedy3 said:
Good question about what the ECU uses; I was thinking about this myself earlier. Only the software geek who wrote it knows for sure. I would hope it is the average of the fronts. I can imagine an experiment with a couple of jack stands...Speedy3 said:
Gear Ratios
From the service Manual
Gear Ratio Final Drive Combined
1 3.538 3.941 13.943
2 2.238 3.941 8.820
3 1.535 3.941 6.049
4 1.171 3.941 4.615
5 1.085 3.350 3.635
6 0.853 3.350 2.876
R 3.831 3.350 12.834
And yes, due to the construction of the transmission, the final drive ratio is different between 1-4 and 5,6,R.
There is no room for variability here; these are gears, you count the teeth and divide.
From the service Manual
Gear Ratio Final Drive Combined
1 3.538 3.941 13.943
2 2.238 3.941 8.820
3 1.535 3.941 6.049
4 1.171 3.941 4.615
5 1.085 3.350 3.635
6 0.853 3.350 2.876
R 3.831 3.350 12.834
And yes, due to the construction of the transmission, the final drive ratio is different between 1-4 and 5,6,R.
There is no room for variability here; these are gears, you count the teeth and divide.
Rotus8 said:
works for me.
actually, speedy3's derived numbers weren't too far off the real numbers. good info to have and might explain why my friend's MS3 dynoed only 200 HP at the wheels. i believe since they didn't know gear ratios, they just input it as 1:1 and used 5th gear.
1st Gear: 14.384
2nd Gear:9.060
3rd Gear: 6.173
4th Gear: 4.731
5th Gear: 3.730
6th Gear: 2.930
Rotus8 said:
I did take Dynamics.....But I stand corrected. (hand) You Rock! (yippy)
Rotus8 said:
If it is just off the front, then the dyno feature of Auterra Dyno-scan is not going to be accurate with all the wheel spin we get, especially with the acceleration test.
desperado-c
Member
- :
- Mazdaspeed3
camrycev6 said:
Sure, if you believe every word printed by the mags is the gospel and written in stone. Also, that may refer only to boost being limited by the waste gate. The MS3 also limits power and boost by reducing throttle angle. This definitely takes place in 3rd and probably takes place in 4th as well. Check out the AMS thread on Mazda Three Forums MS section for documentation. CPE has also documented this and will only release their piggy back with a 2nd gen board that can control it as an additional factor.
Someone else (a Mazda dealer tech, I think) pointed out that limiting throttle angle is a good way to limit power because it keeps the turbo spooled up. Nevertheless it is a limit on power. So you're not getting 100% in 3rd-4th. Definitely not all the time. The limitations may simply depend on wheel angle to counter torque steer, but they are definitely there.
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I was basing my power quotes on a straight line. If you are not turning at the time, you get 100% of your power in third.
And no, I don't believe everything I read, but I could also quote two more magazines that say the same thing. If you don't believe ANYTHING you read, nor trust multiple respected sources, then you could never trust anything but personal experience. Since I have neither the time nor equipment to test this myself, I am going to have to go with what multiple experts have stated. I will take my chances.
And no, I don't believe everything I read, but I could also quote two more magazines that say the same thing. If you don't believe ANYTHING you read, nor trust multiple respected sources, then you could never trust anything but personal experience. Since I have neither the time nor equipment to test this myself, I am going to have to go with what multiple experts have stated. I will take my chances.
desperado-c
Member
- :
- Mazdaspeed3
camrycev6 said:
Sure, rely on the magazine writers if you wish. But, since most of us have neither the time nor the equipment to test things ourselves, here's some data and commentary provided by AMS regarding throttle angle and boost anomalies they noticed during their tests:
If you take a look at what is going on above you can see a very erratic red line. If you take a look at the key on the left hand side you will see that this red line corresponds to the throttle position angle. Notice, this is not the throttle position from inside the car, this is the actual throttle valve position, as controlled by the ecu. For this entire run, the throttle pedal inside the car is being held to the floor. The yellow line indicates boost pressure and the green the RPM range. At what appears to be about 2000 RPM the throttle valve closes rapidly to about 50% holds there until full boost, which is just after 3200 RPM. ....
.... As can be clearly seen, throttle angle is tapering off and the line directly above it, boost pressure, is following suit. .... The boost pressure would most likely drop in the higher RPMs anyways, but it would also most likely follow the trend in-between the RPM ranges of 3200 and 5000 RPMS, dropping to something slightly over 12 or 13 psi most likely. A stock Speed3 drops the boost pressure all the way to 5lbs by the end of the run! ....
Presumably this data was obtained during a 4th gear run on the dyno (ie., with the wheels straight). So who ya gonna believe, the car mag writers (who are probably just regurgitating what Mazda has told them) or your lying eyes?
desperado-c said:Sure, rely on the magazine writers if you wish. But, since most of us have neither the time nor the equipment to test things ourselves, here's some data and commentary provided by AMS regarding throttle angle and boost anomalies they noticed during their tests:
If you take a look at what is going on above you can see a very erratic red line. If you take a look at the key on the left hand side you will see that this red line corresponds to the throttle position angle. Notice, this is not the throttle position from inside the car, this is the actual throttle valve position, as controlled by the ecu. For this entire run, the throttle pedal inside the car is being held to the floor. The yellow line indicates boost pressure and the green the RPM range. At what appears to be about 2000 RPM the throttle valve closes rapidly to about 50% holds there until full boost, which is just after 3200 RPM. ....
.... As can be clearly seen, throttle angle is tapering off and the line directly above it, boost pressure, is following suit. .... The boost pressure would most likely drop in the higher RPMs anyways, but it would also most likely follow the trend in-between the RPM ranges of 3200 and 5000 RPMS, dropping to something slightly over 12 or 13 psi most likely. A stock Speed3 drops the boost pressure all the way to 5lbs by the end of the run! ....
Presumably this data was obtained during a 4th gear run on the dyno (ie., with the wheels straight). So who ya gonna believe, the car mag writers (who are probably just regurgitating what Mazda has told them) or your lying eyes?
I appreciate the data. I will have to take some time to consider it. I do want to point out that boost pressure is not the only factor to determine overall power. You have to consider the A/F mix, rotational velocities, etc. I could have lower boost pressure is some cases and still make more power. So just saying that boost pressure was lowered doesn't necessarily make the conclusion obvious. Speaking of that, I wasn't sure of your conclusion based on the data.
Are you saying that the car constantly modifies the available power in all gears? Why wouldn't you have all of your available power in 4th? (Assuming you aren't turning or the wheels are slipping...aka traction control kicks in...)
smoknspeed3
Member
- :
- 2007 Mazdaspeed 3
Ok, ok, I'm pretty good with mods and understanding most stuff related to cars but for the love of god! Speak English! What is the bottom line with the CAI? Good investment? Not worth the money? I built up my previous car with everything except FI. And to get more then 5 whp was a good gain. 20 hp average is damn good for $300. Also why doesn't Mazda just reflash the damn ECU if it runs so rich? The SVT Focus had a factory reflash that solved a ton of problems. I just bought my MS3 and I can tell the suker runs rich as hell the damn tail pipe is black after 100 miles.
smoknspeed3
Member
- :
- 2007 Mazdaspeed 3
camrycev6 said:
Did a search, man I have read so many dynos on this my eyes hurt. LOL The only reason I asked is there seemed to be a a lot of arguing and no real wrap up post saying this is the real results.
