Stoutdog's GDE Experience, and more!

Lancer · **Posted:** Fri Aug 14, 2009 5:15 am

I have to say, my engine temps were the same - one tick below middle, until one day last week. The air temp outside was 30deg celcius and it was very humid. I was only driving about 5 miles to a garden supplier to pick up a lawn mower (I have an exciting life) and had the aircon on. Temp guage climbed up to 3 ticks above centre before I noticed. I switched ac off and it dropped back to just above centre. The guage was still reading one mark above base 5 hours later.

I'm due for a service in a month's time, and I'll mention it to the dealer then.

warp2diesel · **Posted:** Fri Aug 14, 2009 9:29 am

stoutdog wrote:

I've never seen my temps jump above stock levels (one tick below half). Is a fuel cooler really necessary in a Jeep that is used primarily as a DD and light off-road vehicle?

I may tow lightly eventually, but not for 3-4 years at least.

I can not remember the exact VM 2.8L CRD thermostat temp but I recall it to be about 195-200f. Temps under the hood are even higher than the coolant temp. Even some WVO heat the fuel to 140f but not to 163f+. Fuel likes to be cooler and closer to comfortable ambient temps. Fuel coolers help meat that objective.

nursecosmo · **Posted:** Fri Aug 14, 2009 11:15 am

warp2diesel wrote:

stoutdog wrote:

I've never seen my temps jump above stock levels (one tick below half). Is a fuel cooler really necessary in a Jeep that is used primarily as a DD and light off-road vehicle?

I may tow lightly eventually, but not for 3-4 years at least.

I can not remember the exact VM 2.8L CRD thermostat temp but I recall it to be about 195-200f. Temps under the hood are even higher than the coolant temp. Even some WVO heat the fuel to 140f but not to 163f+. Fuel likes to be cooler and closer to comfortable ambient temps. Fuel coolers help meat that objective.

Straight WVO should be heated to AT LEAST 160f in a common rail application. 180-200f would be even better. Of course the fuel temp sensor must be unplugged or bypassed. Like you say DinoDiesel doesn't like to lubricate at that temp.

stoutdog · **Posted:** Fri Aug 14, 2009 11:42 am

Wait, I'm confused.

Are you saying that, under normal driving conditions (with temp gauge one tick below center), the fuel is too hot and the engine cuts power?!? That doesn't make any sense! Why on earth would DC install a system which is supposed to heat to temperature "x" under normal driving conditions when then fuel temp sensor will cut power at temperature "y" ("y" being lower than "x", if that makes sense... I don't know the numbers).

According to GDE, the engine only begins to lose power when temps exceed 225f, way higher than the 163f mark that you claim. They say you won't even notice power loss until around 234f.

nursecosmo · **Posted:** Fri Aug 14, 2009 12:12 pm

stoutdog wrote:

Wait, I'm confused.

Are you saying that, under normal driving conditions (with temp gauge one tick below center), the fuel is too hot and the engine cuts power?!? That doesn't make any sense! Why on earth would DC install a system which is supposed to heat to temperature "x" under normal driving conditions when then fuel temp sensor will cut power at temperature "y" ("y" being lower than "x", if that makes sense... I don't know the numbers).

According to GDE, the engine only begins to lose power when temps exceed 225f, way higher than the 163f mark that you claim. They say you won't even notice power loss until around 234f.

Coolant temp and fuel temp are two vastly different things. Under normal driving conditions the fuel temp will never reach 163* unless possibly you are climbing a long mountain on a hot day with an almost empty tank. Even then I would still doubt that the fuel temp would get that high. The long steel fuel lines to and from the fuel tank provide all the cooling that we need.

Joe Romas · **Posted:** Fri Aug 14, 2009 12:21 pm

[quote="nursecosmo"
The long steel fuel lines to and from the fuel tank provide all the cooling that we need.[/quote]

Mine are plastic :shock:

nursecosmo · **Posted:** Fri Aug 14, 2009 12:34 pm

Joe Romas wrote:

[quote="nursecosmo"
The long steel fuel lines to and from the fuel tank provide all the cooling that we need.

Mine are plastic :shock:

[/quote]

Why did you add plastic fuel lines?

stoutdog · **Posted:** Fri Aug 14, 2009 1:23 pm

nursecosmo wrote:

Coolant temp and fuel temp are two vastly different things. Under normal driving conditions the fuel temp will never reach 163* unless possibly you are climbing a long mountain on a hot day with an almost empty tank. Even then I would still doubt that the fuel temp would get that high. The long steel fuel lines to and from the fuel tank provide all the cooling that we need.

Nurse, thanks for the explanation. Long story short, I don't need a fuel cooler. Good, that's more money for other mods.

ATXKJ · **Posted:** Fri Aug 14, 2009 4:30 pm

stoutdog wrote:

Long story short, I don't need a fuel cooler.

you might want to think about that some more - check locations nursecosmo is Wisconsin, you're in Tempe
I suspect a 90 would be a hot day in Wi and cool in Tempe -

I had friends in Phoenix when the airport shutdown because airplanes are only rated to 120

compressing the fuel for the injectors heats it significantly - when the outside air is over 100 long steel lines are not cooling it that much -
you're really depending on the fuel in the tank to absorb the heat.

and the smaller Tranny coolers are fairly cheap - designing a good install is the hard part.

Joe Romas · **Posted:** Fri Aug 14, 2009 4:31 pm

nursecosmo wrote:

Joe Romas wrote:

[quote="nursecosmo"
The long steel fuel lines to and from the fuel tank provide all the cooling that we need.

Mine are plastic :shock:

Why did you add plastic fuel lines?[/quote]

Actually after crawling under there they are only plastic back by the tank :oops:

nursecosmo · **Posted:** Fri Aug 14, 2009 9:19 pm

ATXKJ wrote:

stoutdog wrote:

Long story short, I don't need a fuel cooler.

you might want to think about that some more - check locations nursecosmo is Wisconsin, you're in Tempe
I suspect a 90 would be a hot day in Wi and cool in Tempe -

I had friends in Phoenix when the airport shutdown because airplanes are only rated to 120

compressing the fuel for the injectors heats it significantly - when the outside air is over 100 long steel lines are not cooling it that much -
you're really depending on the fuel in the tank to absorb the heat.

and the smaller Tranny coolers are fairly cheap - designing a good install is the hard part.

I've only lived here a couple of years. Tennessee before that and frequent trips to visit family in Texas. Tennessee gets up to 100 and over and has a lot of steep grades. Texas speaks for itself.

Fuel does not compress and thus does not heat up by compression. Nor do our injector lines run under the valve covers like in the Duramaxes and fuel does not run through fuel galleys within the head like in Powerstrokes, both of which benefit from return line coolers in some situations. The only place where heat is picked up (apart from ambient heat under the hood), is from the very brief contact with the injectors(the fuel pump is cooled by the fuel). I suppose that there are situations where extra cooling would be of benefit, but under normal conditions it isn't nesesary.

warp2diesel · **Posted:** Fri Aug 14, 2009 10:26 pm

Yes fuel cools the CP3 pump and other components in the fuel system.

How can the fuel cool the CP3 pump and Injectors with out getting hotter?

Explain why when you pull in to refuel in hot whether add the cool fuel goes into the tank, the engine runs better as you drive off?

Why does Bosch recommend fuel coolers for Common Rail Systems in their Diesel Engine Fuel System Management book?

Why would Bosch spend the money to put a fuel temp sensor in the fuel system if the fuel temperature made little or no difference?

To get rid of the heat, it needs to be dissipated some how, what the fuel cooler does is provide another way to do so.

By cooling the fuel the window of optimum performance is enhanced.

I prefer to have my CRD run just as well at 100f as it does at 65f, with the fuel cooler it does.

Fuel Cooler = Cheap Upgrade and Cheap Insurance.

nursecosmo · **Posted:** Fri Aug 14, 2009 11:21 pm

I'm not saying that the diesel doesn't pick up heat from the engine. Just that it should never ever approach 163*f under normal operating conditions. I know that a couple of forum members have added fuel temp gages, but did not report the fuel ever reaching the ECU de-fueling temperature. Adding a cooler certainly won't hurt anything, especially down in Arizona or other hot southern states. It can even conceivably make the IP last longer if a significant drop in fuel temp can be achieved.

On the other hand, higher fuel temps lead to better atomization of the fuel, which gives better efficiency and economy. The savings in fuel due to higher efficiency at high(sub de-fueling) temps may offset the price of replacing your CP3 a thousand miles sooner.

BTW I have never experienced an improvement in engine performance after filling up with cold fuel.

stoutdog · **Posted:** Sat Aug 15, 2009 1:35 am

To add to what Nurse has said -

GDE:

Quote:

A fuel cooler is not necessary on the KJ CRD. The temps rarely get over 130 F and only in low fuel level situations. Towing a 5000lb trailer with low fuel one can see up to 175 F with less than two gallons remaining in the tank...ie. with low fuel light on. Not something most people would ever consider doing. A fuel limitation starts around 160 F and progesses up to 195 F at which time the engine will only idle. We have never seen temps near this high.

A fuel cooler can be a drawback if living in cold climates, there is more potential for line freeze with a cooler and the fuel heater on the vehicle does nothing for frozen fuel lines near the tank.

Oh, and ATXKJ, I'm just a grad student in AZ. I should be gone in two years, possibly to the NW. Until then, I'm lucky - I get internships far, far away from AZ each summer (this summer I was up in DC). I may see 15 100+ days each year.

stoutdog · **Posted:** Sat Aug 15, 2009 1:48 am

Mileage update in original post, first tank!

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

nursecosmo wrote:

BTW I have never experienced an improvement in engine performance after filling up with cold fuel.

I have, when the tank is low and it is over 105. I would love a fuel cooler, but where? The front of the vehicle is the best spot-- plenty of cool air. It does not give me warm fuzzies thinking about the fuel line running up there in the event of an accident. Underneath the Jeep somewhere would be good-- if I never went offroad. Under the skids is pointless here, it would be more of a fuel heater than a cooler. So I am still going without. Perhaps next summer I will crawl under there with the infared temp gun and find a good spot.

stoutdog · **Posted:** Sat Aug 22, 2009 8:08 pm

Final update, above. Multiple monsoons and dust storms didn't help those last two tanks...

Cowcatcher · **Posted:** Sat Aug 22, 2009 9:16 pm

So, I haven't been proweling for a while. One reason some installed fuel coolers was related to the stall problems many of us have experienced in hot weather, generally solved by a fuel pump but presumably associated with overheated fuel from the CP3 to the bypass. With this great new tune that reduces fuel consumption is it likely that more hot fuel is being returned to the tank than before by the CP3? If so might those without in line pre filter pumps experience more stall issues?

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