dsmdriver

iTrader: (3)

I've had my '04 for about 2K miles. It's used, and I've had it from 5000-7000 miles.

In my normal commute, I get 14MPG, every time, no matter how I drive. It's a 7 mile drive each way that takes 15-20 minues, and involves probably 5 minutes of waiting. I live in Seattle, and temps have varied from 25-50 degrees on my commutes.

The thing I noticed was that the 8 seemed to take forever to warm up. It was really only really warm after 10+ minutes. I was used to my old piston engine car being warm in half that time.

I finally decided to try something to see if the long warm up time was part of the MPG equasion. I blocked off the radiator and oil coolers. I have the Hymee grills, so I just stuffed a plastic bag in front of them and then I blocked off the lower half of the nose with blue speed tape. The car heats up much faster now, but the temp needle still stabilizes about 10% down from the middle, which is exactly where it stopped before. It doesn't seem to overheat or be working extra hard, and I have double checked this by meauring the temp out of the heater vents and it always stabilizes at about 60 degC, just like it did before.

My car pretty reliably hit the 1/4 marks every 50 miles beforehand. I've driven it 120 miles so far (that's 8-ish days of commuting), and it hasn't gone down 1/2 yet. It looks like it's getting about 16-18 MPG, a signifigant improvement, but only a full fill-up will tell.

So I have a few basic questions:

1) Is this a bad thermostat, or is it just the way the car is designed? The tstat seems to be working in that the temperature stabilizes, but it warms up much faster with everything blocked off, so clearly some overcooling is ocuring while it's cold. Anyone know how much the thermostat is supposed to bypass when it's "closed"?

2) Is it the tstat or the oil coolers? I guess I'll have to unblock just one and see if I can figure out if it is one or the other or a cumulative effect.

3) How do I convince a dealer to look at this and fix it? This is the first car I have ever owned that is under warranty. I'd normally just rip into it and replace the t-stat, but it's more of a pain on this car than most, and why do I have a warranty if I'm not going to use it? I just don't know what I should say to the dealer to get some action not just "no codes, it's fine." I kind of don't want to tell them I blocked off the radiator even though I have carefully monitored the temp and it has never overheated.

So any ideas? I'd be a lot happier with the car if it got 16-18 MPG in the way that I used it, and it seems like it can. I just can't tell if it's really broken right now, or if it's just the way it's designed.

strokercharged95gt

Being that I live in Florida in the winter some days it can be in the 30's and the next day in the high 80's. I always keep a mental log of my MPG and when its cold out for a few day stretch I at best see 18 mpg. On hot stretches I see 21 mpg. Its like clockwork. I know that a 30-40 degree swing will change my mpg significantly. Im not sure if the 8 has a regular thermostat since I have never worked on the motor. I would imagine that the 8 would have the failed open thermo because its a much safer design. I bet your thermo is fine and it just takes while to heat everything up in your whether. Hell it takes a good 3-4 minutes here to see the needle to move off the edge on a cold day

dsmdriver

iTrader: (3)

I figured that when summer comes around here, I'll see better MPG. But it seems like a broken design to allow so much overcooling, especially when the ECU waits for the temp to come up before going closed loop.

The 8 does have a regular thermostat. It also has a thermostat in each oil cooler, so there are 3 possible points of failure. I also wonder if it's just the air moving through the radiator and into the engine compartment that is cooling the motor.

Another thing I wonder: Why does the ECU stay open loop until warm? Is this just an emssisions thing for cat light-off, or some other reason? My previous cars all went closed loop as soon as the O2 sensor was heated up, which only took about 30 seconds. I'm almost tempted to lie to the temp sensor with a resistor and see what that does.

zoom44

it has to wait for the cat and Wide band to warm up. id bet your last cars didnt have a wide band o2.

it is a fail open but in your case it doesnt seem to have failed but its worth a check.
its cold, you have a short trip and oxygenated fuel. do you drive out for lunch as well?

dsmdriver

iTrader: (3)

Only go out for lunch about once every two weeks, or about once per tank. Haven't done that on this tank yet.

My last car didn't have a WB O2, just a single, pre-cat O2.

What would people's best guess be as to where the extra cooling is coming from?

zoom44

the outside temp. do you park in a closed garage overnight?

dsmdriver

iTrader: (3)

Yeah, in a garage at night, usually around 55 deg F these days. Outside during the day.

I'm mostly suprised that the airflow over the radiator and oil coolers has that much effect when the thermostats should theortetically be shut, which leads me to wonder if they are actually shut.

zoom44

hmmm get it checked then. its not sitting in that 20-30 temp its sitting in 55. so should be warming much quicker.

Blue87Sport

I live in Seattle too and I haven't noticed that it takes longer for the 8 to warm up. Of course, my previous car was a rotary too.

From your commuting profile, you're clearly doing "in city" driving so at best you should get 17-18 mpg. You also have to factor in the oxygenated gas we're using over winter. I've lost about 1-2mpg (from around 20 to 18) due to that. So 14 mpg isn't really too far off given the situation. So I don't think that anything is broken. It would interesting to see if you get consistent improvement from your test. There's so many factors affecting mileage its hard to isolate a single factor without a lot of data.

There's one part of your post I wonder about though. If you read the threads about the engine failures last summer in hot climates, it seems that most of them were in hot and *dry* climates. Our winter climate here is cool and moist. So if hot and dry overheats the car and cool and moist underheats the car, could it be that something in the design of the cooling systems is extra sensitive to humidity?

dsmdriver

iTrader: (3)

I am clearly doing "city" driving. I don't expect the EPA city numbers, and my commute does have a lot of stops, but it also has a 2.5 mile highway section (out of the 7), so something close to it seems reasonable.

The difference between 18MPG and 14MPG is about 25%, which would be the same as saying 30 and 38 MPG are about the same. It's signifigant that the car can throw that much fuel away. I would think all that extra fuel would help it heat up! I'm suprised that I can get the EPA numbers with the front of my car taped over but get 25% less with the stock airflow. That seems to me like a major design flaw or something broken. I wonder what temp the EPA does their tests?

I really do trust that I am getting better fuel economy. I've driven the car for two months on this commute, and my MPG hasn't varied by more than .2 MPG at any fill up that didn't involve lots of HW driving. Suddenly I'm 120 miles in and seeing a drop on the fuel gauge that I expect at under 100 miles. I totally agree that I'd need to do this test for a few tanks to be sure, but given how stable my MPG was before, a change looks pretty likely.

One thing I didn't mention before: On the HW I only get about 17-18 MPG, with the cruise set @ 75. This is one of the things that made me wonder if it was never going closed loop.

One thing I am thinking of trying: instrumenting the oil coolers and the radiator. It would be interesting to see if I see much heat rise before the thermostats are supposed to open up. Before I go to that length, I'll probably un-cover each cooler for one tank of gas and see if I can isolate it. If I can keep my MPG up with only one part blocked off, especially if it's one oil cooler, that would be an obvious failure.

The humidity isn't suprising. The "wetter" the air is, the more energy you can give off to it, since the air is denser. For any given temp, the dryer the air, the more the cooling system has to work. So dry, hot air is clearly bad, and cool, damp air will also be the most likely to overcool if anything will.

zoom44

epa test http://www.fueleconomy.gov/feg/how_tested.shtml

does it take you 4 minutes to do the 2.5 miles or 14?

define the "HW" trip in which you got 17-18

dsmdriver

iTrader: (3)

Takes me 2 minutes to do the 2.5 miles on the highway. It's wide open, cruise @ 75. I do the full 7 mile trip in about 15 minues most mornings.

The highway trip that got me 17-18 was two trips. One was when I first got the car, driving up to Vancouver, which is about 150 miles each way, with a stop at the border for about 20 minutes each way. This was basically a no traffic drive each way, 65-75 MPH cruise control. This trip netted me 17 MPG overall, but it did have 40-ish miles of heavy city traffic out of 400 miles.

The other trip was 110 miles of running around Seattle highways one day. No traffic jams, and that tank, which would usually get me 190 miles on 13.5 gallons, got me 215 miles. That's 16MPG overall, but 105 miles of that was @ 14 MPG. Thus 18.33 MPG for that 110 miles of highway action.

The trip to Vancouver was 40 deg F and solid rain, versus dry and 60 deg F in the Seattle run.

Thanks for the link to the EPA test. Unfortunatley, no info on environmental setup. For all I know, they're allowed to do the test at a perfect outside air temp and humidity for efficency.

zoom44

neither of those trips is HW. HW is - fill up. go directly to th highway. accelerate to cruising speed. when you get off the highway go directly to fueling and check mileage. any more non hwy miles then is necessary to get to/from a gas station makes it not usable to compare to HWY mpg from epa or anyone.

2 times now i have driven from portland to wenatchee and back. every Hwy mileage check ihave been over 22(80+mph) and usually closer to 24(65-75). i dont count any tank that is partially used in wenatchee or home.

dsmdriver

iTrader: (3)

I'm not saying those were full HW trips. But if I was getting anywhere near 20-22 on the highway, my combined mileage would be higher. If you know how much you get in the city reliably, then you can back-calculate what you got on the different portion.

I understand that the EPA numbers that are highway, mean highway only. I also know that if you are getting 24 MPG on the highway and do that for 150 miles, and then you run out of gas (14 gal) at 220 miles, you only got 9 MPG on the last 70 miles. You probably didn't get only 9MPG in the city portion, so by definition, you didn't get 24MPG on the highway. Even if you didn't drive a full tank on the highway, you still have a good sense of what you got on the highway portion. In the end, MPG is instantaneous- you don't have to drive a full tank at cruise to get 24 MPG on the highway. You can do 100 miles on the highway and then 150 in the city and still get 24 on the highway, and your mileage when you run out will reflect this partial tank increase.

Here's one more example to prove my point:
Drive 13 gallons at 24 MPG. That's 312 miles.
Drive 312 miles in 14 gallons. That's 22.3 MPG.
If you get 24 MPG on the highway, drive 312 miles, and then go CRAZY in the last few miles on and off the highway, you can't get your average below 22.3 MPG. The reality is, the last few miles don't make that much difference. The requirement to pull right onto and then off the highway to really measure HW MPG isn't real. If you do a good portion of a tank on the HW, your overall MPG will be pretty close to your HW MPG.

In my case, I drove 150 miles to Vancouver, and then 40 miles around the city, and then back home. I filled up (13.5G) at 230 miles. If I got 22 MPG on the highway portions (190 miles), I only got 8.23 MPG in the city. I really doubt that happened.

Anyway, I know the 8 doesn't get great mileage, and I'm not here for another one of those threads. I'm not trying to compare my mileage to EPA numbers or really to anyone else. I'm really just interested why blocking off the cooling bits appears to be having so much effect, and why my HW efficency doesn't seem to be that much greater than my city efficency. Currently my theory is that the car is being overcooled somehow and staying open loop. Hopefully I can figure out if I'm right, and if there's a permanent way to fix it.

zoom44

actually kevin (nemisis) and i have proven that not true. we together ran back from 7stock with a couple of others. when we stayed in cruise the whole tank we got 23-24(he got a tank over 24 a time or 2) but play for part of a stretch and we could shove it down to 18-19.

if you spend alot of time going nowhere in town you will obviously reduce your mpg.

but you are correct we digress.

you are blocking off the cooling so the engine is heating faster and going to closed loop sooner. maybe it is sticking open but it hasnt failed or the guae wouldnt settle in the normal spot(which is slightly left of center)