Last post on Aug 23, 2008 at 7:41 AM
You are in the Mazda Mazda5
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Mazda MAZDA5, Van
#4 of 13 Re: Mazda5 and mountains [mattson3]
Jun 26, 2008 (9:18 pm)
Depending on how steep the hills are you can do 2 things if you are worried get gas with ethanol in it. Ethanol gas attracts oxygen to it hence why it helps with emissions but also lowers mileage, but as you go higher the amount of oxygen goes down. Try running up a flight of stairs in Mexico City you will know what I mean. Second higher octane gas will allow the ignition to advance the timing of the ignition as there is more anti ping in higher octane gas. The more advanced the timing the longer the gas has to burn plus with the extra oxygen from the ethanol will help. Just my 2 cents worth. I drove throught the mountains in virgina a while ago and had not issues. Do not use your cruise control in hilly terrain as your gas mileage will be affected greatly, you can accommodate the gas better than cruise i.e. you can see the hill coming after the down hill and can speed up a bit more going down to be used when going up the next hill.
Just my 2 cents worth.
#5 of 13 Re: Mazda5 and mountains [mattson3]
Jun 29, 2008 (8:20 pm)
As mentioned, avoid the cruise control on steep grades. You can use it but the car tries too hard IMO to get you to speed quickly so don't be surprised to see the TAC swing way up with the engine screaming at 5500 rpms as the vehicle shifts down and acts less smoothly than normal.
Doing numerous 6% and 7% grades recently the Mazda5 will continue to pick up speed if you need it to, albeit not the quickest vehicle but not bad. It has decent passing power and pull for a 4 banger on the steep grades. I was a bit surprised the Mazda5 would do 5th gear half the time on 7% grades and not work that hard.
I try to keep the rpms down and I noticed my M5 GT AT with about 750lbs of people and gear had a sweet spot somewhere close to 60mph to stay in 5th at 2400 rpms or 4th at 3000rpms on very long 7% grades. If I wanted to pass or do a faster pace it was there with 3rd gear.
One thing I have not figured out yet, when I crest a hill in 4th I haven't quite figured the trick to get the vehicle to automatically go into 5th on the down hill side. I notice sometimes I'm coasting down the hill at 60mph and my rpms are still at 2000 or so. Other times the rpms are close to 1000 rpms.
#6 of 13 Re: Mazda5 and mountains [jschner]
Jun 30, 2008 (12:07 am)
More than likely the reason the car stays in 4th gear is because of the coasting the computer 'thinks’ you want to maintain that speed and used the 4th and the engine to 'slow' the car. If you want to get it to go into 5th just give it just enough gas so that the engine breaking is not warranted (not sure if I am making my self clear on that part - so not accelerating but not coasting) for a few seconds then the car will shift and then the transmission will shift to 5th.
On a second note I am wondering if at this same speed you are going down hill and slightly press the break to slow down a bit will the transmission down shift. If it does then I would assume that there is angle sensor like on Honda’s and others. I only have a 4 speed transmission so can not test this theory.
#7 of 13 Re: Mazda5 and mountains [athenasius]
Jun 30, 2008 (5:53 pm)
In the 4AT there is no downshift when braking. The engine does do a good job of holding a lower gear for uphill grades though. For the 5AT, I am thingking if it doesn't shift into 5 downhill, try slipping it to the M gate, shifting to 5 and slipping back to the D gate.
As far as RPMs go, a couple things could change the coasting RPM. Once the Torque Converter locks, you will see a drop in RPMs. It may take a few seconds after cresting a hill to lock up. Also, my understanding is that the 5 can cut fuel (noticeable on cruise control especially). If normal cruising at a give speed = 2000 RPM and you see the tach drop to 1000 RPM, it could be the fuel cutting out .
#8 of 13 Re: Mazda5 and mountains [mrbwa1]
Jul 13, 2008 (9:15 am)
And when you're on a long downhill grade, being in 5th gear at 1000rpm or 4th gear at 2000rpm uses no more gas since the throttle is basically at the idle setting in either case.
#9 of 13 Re: Mazda5 and mountains [bobw3]
Jul 14, 2008 (8:21 am)
"And when you're on a long downhill grade, being in 5th gear at 1000rpm or 4th gear at 2000rpm uses no more gas since the throttle is basically at the idle setting in either case. "
That really depends on the % of grade and the engine load. Being that the throttle and fuel management are 100% electronic, you really don't know what position the throttle is in and how much fuel is being supplied to the engine to keep it running smoothly.. Effectively using engine braking does reduce fuel consumption and manufacturers are pursuing this to reduce MPG.
#10 of 13 Re: Mazda5 and mountains [maltb]
Jul 14, 2008 (9:05 am)
Even without any hill, if I'm coming up to a redlight and I let off the gas completly to allow engine braking to slow me down, there is no requirement of any combustion in the engine to keep the engine spinning, since it's the forward motion of the car that spins the engine, so that's why I'd think that the engine is at it's lowest throttle setting, unless it has a fuel cutoff setting.
But I'd say there's no reason that engine braking would use any more gas than putting a car in neutral and letting it coast, since in both cases both engines are basically ideling.
#11 of 13 Re: Mazda5 and mountains [bobw3]
Jul 14, 2008 (3:17 pm)
I dissagree but until we see a fuel system map or some real time injector pulse data, this one is up in the air.
Has anyone hacked their Mazda5 PCM?
Aug 23, 2008 (7:41 am)
Took a trip out west this summer, ( milwaukee to mount vernon WA, down through idaho, and back up through yellowstone and home), and went through several mountainous areas.
I found my 06 manual shift 5, despite being heavily loaded with about 800 lbs people and gear actually got slightly better milage in the mountains, about 31.5 instead of the 31 I'd been averaging, and zero problems with power.
In fact, at one point I was " racing " a group of harleys up the cascades doing about 75 mph up the 7% grades, ( 3rd and 4th gears) and the bikes simply did'nt have the power to get around me on the short straights.
When they finally did get around me on a long straight, ( prob doing 95 mph in the process), they found I was thereafter running up their tailpipes on every corner after as the 5 could get through the corners faster than they could. I still averaged 29 mpg for that tank.
It must have ben a bit embaressing for them to have such trouble getting around a obviously heavily loaded minivan.
As far as the discussion of fuel cutoff on throttle lift, all modern cars do this already for the purpose of emmisions control. A engines emisions go through the roof in these conditions if the fuel is'nt cut off. I would imagine the fuel mapping shuts off whenever it would be transparent to the driver, like in periods of engine braking over some minimum rpm.