Turbo diesel dilema!

[JQmile]

I did this a couple years ago with my Dodge Ram and drove from Vegas to LA and broke 30 mpg. The grille block alone was worth about 2 mpg at highway speeds. I wouldn't worry about engine temps, the new trucks run 230 degrees all day long and they're the same basic engine. Also with the part throttle conditions you truck will be under it will only need to make about 40 hp to propell the vehicle, so I wouldn't be worried about an efficiency drop--you'll only see a big effect under full power. If you do tons of highway driving and don't tow or go up a lot of hills I'd leave it on. Just be mindful of those engine temps if you're in the throttle too long. Here's the 30mpg dodge 1-ton article link:

1997 Dodge Ram 3500 Dualie Cummins - Diesel Power Magazine

[tasdrouille]

Exhaust temps shouldn't be an issue unless you are heavily modded and/or towing in extreme conditions. If anything you're just doing your turbo a favor keeping everything nice and hot so it doesn't soot up as much.

The difference from the higher IAT will be minimal on fuel economy. I know it's been for me.

Worry less, drive more.

[Christ]

Frank - Yes, diesels experience knock, but it's a different symptom. Over advancing the fuel pump can cause it (Injection too far before TDC, kind of like ignition over-advance.).

Too much heat (I mean REALLY hot) can open up the cylinder walls away from the pistons, making too much clearance, which causes piston slap, which sounds like knocking. This typically happens when the cooling system can't keep up with overheating cylinders, the upper ends of the cylinders will expand slightly, giving clearance to the pistons to slap against the cylinder walls on compression and power strokes (due to stresses). It's a semi-metallic clack noise (different than the normal diesel clack) that usually indicates that your pistons/rings are about to grenade.

I'm aware that diesels run on the knock principle, however, they do it in a controlled fashion.

[nubbzcummins]

JackMcCornack: Could you explain pumping losses that occur with my setup running in boost other than at idle and going down steep grades? Also how does warmer air make it more efficient vs cooler air which makes more power and requires less boost to achieve the same required power to overcome all drag/losses on the vehicle?

Frank Lee: I'm loosing power at all times so explain why it will not be noticeable in mpgs. Refer to my statements to JackMcCornack.

JQmile: Thanks for the input. Explain how cool/warm intake air alters mpgs from your experience. Do you think a liquid/air intercooler vs air/air with grill block would be beneficial? The highest engine temps I have seen so far has been around 200-205 degrees with low 90's ambient.

tasdrouille: Please explain your experience with IAT and mpgs.

Christ: When you speak of the knock are you talking about the same thing that happens when you advance the timing? If so I know exactly what you are talking about. Also please share your experience with warm/cool intake air and mpgs.Thanks.

My way of thinking is that if the truck is as aero as possible and get as cool air as possible (to a certain point) the mpgs will go up.

[Christ]

Yep, that's one way that you get knock. It's the same thing that happens when you advance the ignition timing in a gasser. It can seriously re-format your pistons and rods, and could break your crank/main caps.

The other thing that I was talking about is waht happens when the coolant can't work fast enough to take heat away from the upper part of the cylinders in the block, and the heat causes expansion, leaving the pistons loose while they're at the top of the cylinder. As the piston reaches the top of the compression stroke, it "slaps" the cylinder wall, and as the initial injection of fuel occurs, the pressure rise on the top of the cylinder causes it to slap in the other direction, against the opposite wall. Extended operation under this condition will cause out-of-round in the cylinders, and can cause piston/wrist pin damage.

I don't have too much data on cold/hot air MPG's, because most of my diesel experience comes from utility engines, such as farm equipment, and it's limited at that. I"m not the 100% diesel guy on this forum, by any means. I just know what happens when you don't keep them happy. (boom)

Regardless of what you've been told, any engine that runs on uncompressed air (has to suck in it's own air supply) has pumping losses, and even those which run on compressed air and fuel have pumping losses. They still have to compress the mixture in the cylinder, and then exhaust the burnt mixture, which requires work. Diesels are no exception to this rule.

My best experience with efficiency (not necessarily economy) with a Diesel is just tuning it until the exhaust is mostly clear. When that happens, you're getting a clean (haha) burn, and as little particulate emissions as you can. This might mean turning up/down the fuel, heating/cooling the intake air, etc. It all depends on the situation, but again, this is dealing with utility engines, and efficiency, not economy. (There is a difference.)

[JQmile]

I've never messed with IAT much, but I think the gain would be minimal. I remember reading an SAE paper that said it affects power, but that was in big rigs pulling lots of weight under 50-80% load. Heck my 89 Dodge gets 25+mpg with no intercooler at all (didn't come with one from the factory) if I keep my foot out of it. If you're looking to get stupid mpg, I'd check these guys out:

DeLuca Fuel Products

Website doesn't look like much, but the guy knows what he is doing.

[Frank Lee]

That's some crazy ****, every other overheated engine I've ever seen had the piston get too tight in the bore, causing it to score then seize. Since, yah know, alum expands faster and more than fe and pistons are usually alum and cylinders are usually fe.

As far as I can tell nobody and no thing is screwing with the injection timing.

[Frank Lee]

Originally Posted by nubbzcummins

Frank Lee: I'm loosing power at all times so explain why it will not be noticeable in mpgs. Refer to my statements to JackMcCornack.

My way of thinking is that if the truck is as aero as possible and get as cool air as possible (to a certain point) the mpgs will go up.

Well how much power are you losing- lots or not so much? If you're not deep into the throttle then I don't know why it would matter. But then, I don't have a turbodiesel so you can see what's going on better than I. I have run NA diesels for ag and road so have exposure to them though.

[blueflame]

I'm driving a non turbo diesel Toyota Townace Noah van every day now. No ECU in this.

I bought some aluminium flexible ducting and redirected the cold air intake to the exhaust manifold, I modified the manifold tin plate on top by welding on a tin tube to fix the flexi tubing on to. My warm up times got way quicker, running temp the same.

I blocked the grille by about 75%. Running temp the same, even quicker warm up times.

I removed the thermo clutch actuated cooling fan, its non electric and locks when warm air thru the radiator heats the thermo clutch thingy. Even engine cold there was lots of windage when the fan blades were supposedly mostly slipping. I reckon I got an extra hp by losing the cooling fan. Yes. No cooling fan at all!! (its winter now)

Even quicker warm up times and same running temp.

But fuel economy really got better when I tweaked the air/fuel ratio screw on the injector pump, nearly 3/4 turn out. Massive 20% improvement!! Averaging 5.8l/100km now in a 1440kg automatic van @60psi with no FAS but neutral glides where possible.

After adjusting fuel/air ratio I had to up the hot and cold idles and adjust auto trans kick down. Dead cold engine has nearly no power, and overall power is way less.

But hey, I'm an ecomodder. 40.5mpg US in a 3100lb diesel van

The earlier Townies used to overheat easily as engine and rad were tucked under the seats, well in from the front of the vehicle, with auto tranny cooling radiator immediately in front of the engine radiator. Toyota made up for this by overcooling the new model with the same 2c engine. Thats what auto engineers are paid for I guess. Roll eyes

I reckon I can go all summer with these mods, maybe open up the grill a bit if temps rise....or 5 minutes to put the cooling fan back on.

I aint hauling loads, sitting in long stopped traffic or travelling fast....Above photo not of my Townie

[tasdrouille]

My experience has been that IAT did not affect MPG on my TDIs. If anything in the winter higher IAT helped. The only thing I can think of was the ECU pulling injection timing back 2 degrees when IAT were above 100 F for emissions purposes. But then I just spliced a resistor in line with the IAT sensor so the ECU thinks it's always -10 F in the intake.