Archives

Now the weather has gotten warmer here, clearing 20'c and sometimes getting to 30'c, i was expecting the mpg on my diesel kia cee'd to improve. However, it has dropped and all i can think of is my grille block. I put in one over the lower opening below the licence plate and it blocked it entirely. I figured the top opening was sufficient for cooling.
It could be something else but its a new car and should be ok.
I suppose my question is this: Does a less efficient intercooler LOWER mpg in a diesel?

ollie

I didn't think that diesel engines responded the same way to increased temperatures as gasoline engines...(they're a bit more unphased by higher engine temps). Anyone?

I would say No, because you have a diesel , and the warmer diesels are the better they drive and the better they consume, noe this all has limits, you do not want to be overcooking your engine. do you have oil temp gauge ? is the engine overheating ?

Also what is the design of this covering, if its a big flat surface on the front of the car, you may have increased resistance, make sure that the air has a way to flow better, not just block it.

ttiwwop !! :d

I can't say about a diesel. On my civic, I'm noticing a loss of power above about 85F with a full block. I removed 1/4 of it (about 25 sq in) and it responds better. I'll be playing with it back and forth over the summer.

(ttiwwop - pics for you by clicking on My Rides)

Thanks for the replies. I dont have an oil temp guage so am flying blind there. I do have a water temp gauge(everyone has!!) and with the block, it never goes above half. I opened the block up on the intercooler side to a size a little smaller than a cd box. The Mrs was driving it today and said it dropped back to HER usual 5L/100k(i can do better!!). Having said that, the weather cooled from 25 to 15 deg c. so that may have also assisted the opening in cooling the intercooler.
The block is made from 5mm black sign board. It's light and slightly porus on the inside but smooth on the surface. It cuts with a stanley knife easily and looks smart. It is a flat surface but so is the surrounding bumper. I'd like to be able to submit pics but haven't a clue how. Any help there would be great.
Regarding staying out of boost, isn't the turbo always spinning, however little. It is in the airflow and exhaust flow after all. Is it just freewheeling in slow flows , thereby not pressurising the air? If it IS slightly pressurising the air at low revs then a complete block over the intercooler would result in it slowly heating up over time. The hotter air is less dense and therefore there is less air there. Which is where i thought there would be less fuel present to keep the mix right. Apparently not. I have a lot to learn....

ollie

Ollie, look for the "Gallery" link in the green menu column on the left. After that loads, look at the far right side of the 3rd horizontal blue bar from the top to find a link labeled "Upload Photos." After that it should be self explanatory. :)

Once you've uploaded, you can click on the thumbnail of the picture and you'll see the full sized version of it with two text boxes below. One has the url of the picture, the other has IMG tags already wrapped around the url so you can just copy and paste into a post.

Hope that helps!

Unlike spark ignition engines, diesels don't have a constant air/fuel ratio. They run extremely lean when load is low. Hot air intakes won't decrease fuel the way they do on gasoline engines.

http://www.cleanmpg.com/photos/data/522/medium/IMG_6434.jpg

Looks good, Ollie! :thumbs_up:

Thanks. I'd like to cover some of the top grille but to make it look stock will be tricky without removing parts for access as i don't want to upset the warranty; it's 7 years parts and labour.

ollie

Hi ollie, I am guessing your car has some auxiliary fans for the radiator? If you have blocked airflow to a degree where the fans have to come on, they could be sucking a lot of power and some of your fuel economy. I would probably unblock the intercooler as temperatures get above freezing. Blocking at low temperatures apparently helps power a little, but blocking at high temperatures hurts it. I generally assume that for diesels, better potential for power means better combustion is taking place, which means improved fuel economy as long as the increased power is not used.

Higher temperatures at the intake manifold = lower dynamic compression ratio and diesels are all about compression. Since a diesel also does not have a throttle plate they run at full air flow all the time. The turbo will always spin and if there is any type of load on the engine at all it will have some amount of manifold pressure, which is not bad. HP per fuel consumption is always lowest at full load with a diesel, HOWEVER more HP uses more fuel, so keep that in mind.

I don't know of any studies, but even in winter they do not want an intercooled semi to have a completely blocked grille. They usually leave a small hole for the intercooler to get some air.

Hi ollie, I am guessing your car has some auxiliary fans for the radiator? If you have blocked airflow to a degree where the fans have to come on, they could be sucking a lot of power and some of your fuel economy. I would probably unblock the intercooler as temperatures get above freezing. Blocking at low temperatures apparently helps power a little, but blocking at high temperatures hurts it. I generally assume that for diesels, better potential for power means better combustion is taking place, which means improved fuel economy as long as the increased power is not used.
There is one electric fan and i don't think it's coming on during a drive. I wouldn't hear it anyway at speed so i might make a summer grille block with more open. The weather is getting hotter here by the day. I've had to open up the civic grille block too as the fan was coming on regularly (every 10 mins or so for 30 sec approx) I opened the block that night in work and the problem has gone.
Thanks to all for the very informative replies.

ollie