Lil Dog

Engine water temp will affect performance for sure.. I was dealing with only one part of the cold air theory..

AkTallPaul

And that is like 90 degrees warmer than it is here now...
Can't wait till it gets to those temps so I can blow mine out real good.

Tree DR

I constantly monitor my intake air with a scan gauge. The intake temp with the stock air box runs around 10-14deg hotter than outside air all the time when driveing.
From what was said earlier it's more important to know the air temp after the intercooler.

XLR8R

Tyler, I brought this subject up on the board last spring and didn't get much of a response... glad to see that someone else has observed this phenomenon! There's a straight piece of state highway on the way to the shop that we use to test 1/4 mile runs, 5th and 6th gear accelerations, etc.
There's no doubt that the '05 runs best in the 70-90* F range, and it runs stronger when the weather is too hot compared to when it's too cold.

That's right, Rusty - I think the ideal is to draw cool outside air into the 'charger and compress it enough so the intercooler only cools the charge air back down to an efficient temperature.

We've had an intake manifold air temperature probe on the '05 shop truck since early last year, and it's been a great tuning aid.

Good point on the heat sink effect of the intake system's mass.

The '05 mods let it breathe really well, so with stock fueling it's tough to get intake manifold air temps up that high; I think the largest differential we've seen before running out of RPM, road or both is about 25 degrees F.

The '05 has an ambient air temp gauge, a pre-CAC pyrometer, and an intake manifold pyro (along with a pre-CAC boost gauge and intake manifold boost gauge) so you can really track what the air is doing on the way to the cylinders.
Normal driving yields a differential of 5-10*F, and as stated above, 32psi only makes for a 25*F differential; the temps climb quite quickly with high boost though, so I'm interested to see how much more the differential will get with 45 psi.

Tree DR

Great information. I had noticed the diference in performance as well. I don't understand your temp defferentials though? 5-10*F, between what points? Is this on a stock truck or moded?

BigBlue

5-10* difference in incoming air temperature and outside air temperature.

Mike, I didn't notice your post last time and I never really bothered to think about it but the more I do the more I think I've got something here and that's why I've been dynoing low lately. When I did 496 it was pretty warm outside. When I did 462 it was blistering cold. Next saturday I'll be able to get a pretty good idea since it'll be warmer.

infidel

Talking with a Cummins engineer several years ago he said ideal intake temp at the air horn is 50-90°F. This was for 12 valves, don't know about the others.
I have a temp gauge on my air horn, intake temp is most always a consistent 20° above ambient.

Tree DR

The '05 has an ambient air temp gauge, a pre-CAC pyrometer, and an intake manifold pyro (along with a pre-CAC boost gauge and intake manifold boost gauge) so you can really track what the air is doing on the way to the cylinders.
Normal driving yields a differential of 5-10*F, and as stated above, 32psi only makes for a 25*F differential; the temps climb quite quickly with high boost though, so I'm interested to see how much more the differential will get with 45 psi.[/QUOTE]

Where is the intake pyro located? What was the 25*F differential between?

BarryG

My Juice monitors IAT temp. In summer the highest I have seen is 143, but on a hot day 100 degrees normally in the low to mid 130's. Once the weather cools (down into the 60's or 50's) it runs in the high 1teens to low 120's. Once it gets below 32 it is in the mid to upper 1teens. Below zero it is in the low 100's. If it is really cold say below 10 deg and am cruising empty at 65mph for long distance say through the mountains I have seen it in the low 90's. Also it does not fluctuate much once to operating temp. If city driving then highway it might drop a few degrees within a couple minutes and maybe another couple degress within 30 minutes. Those temps are all with the engine at operating temps. I have not noticed any real decrease of engine oil temp of more than 10 degrees from the hottest day to the coldest. Water temp can run colder when it is really cold outside but still not more than 20 degrees difference from hottest temp ambient to coldest.

Haulin_in_Dixie

Ok Blue, you khow that I drive for a living. I did it several years with the dodge and now with a freightliner. I do not have dyno figures on any of my vehicles, but I do have efficiency comparisons.

You know that in the winter the fuel is mixed and gets less mileage. I believed that and in fact that is somewhat true. But the last few screwed up winters have made some changes to my thoughts. The milege drops off late in the year and picks up again in the late spring. All fuel changes? I thought so for a long time, but.

From time to time including this week we hit the 70's with over 50's at night and guess what, my mileage went up about 3/4 mile per gallon. Now it is about freezing and the mileage is back down. The only thing that has changed is the temperature. On this truck I have the computer readout on the dash at all times showing the fuel use and press a botton for the mpg currently. It has proven quite accurate.

So I have come to the conclusion that the lower temperatures cuts fuel economy. That means that the engine is less efficient and would also produce less power. Matter of fact, I have a couple of hills that I just barely make over without shifting, leave it on cruise, but when it is colder, I have to drop cruise and downshift.

Hope all this helps your thoughts some.

6speedcowboy

I'm sure the cold air has to do something to it cause i've noticed that my motor is noisier and seems to have less power at night than it does during the day. I've felt my intercooler outlet and it isn't much warmer than my bumper. Right now the temp around 30 degrees F at night. I found a place that still has lsd and noticed a noise reduction and power improvement compared to ulsd

Tree DR

Would it be benificial to have a opening on our air boxes that we could open to the engin compartment to get warm air in the winter? Or is it more important to block off part of the intercooler?

DBLR

The newer winter fronts fit under the hood on the crawl and cover the radaitor, the intercooler and block a lot of cold air to the engine. So I would assume it would help keep the intercooler warmer in the cold winter temps. I think it would be nice if we could get some warm air for the airbox when the temps drop below zero or colder some of us drive in during the winter season.

BigBlue

Haulin that's a good assesment and really helps further my thinking. I don't think we get winter fuel down here in central texas but who knows. I do know that this ULSD stuff isn't as strong as LSD.

I'm really anxious about next week. It should be interesting.

Yall keep the ideas and theories coming. I have a feeling that we may all be on to something. Where's HOHN when you need him?

XLR8R

The differential is measured between the outside ambient air temperature at the driver's side of the charge-air cooler, and in the center of the intake manifold air horn just above the grid heaters. There is another pyro mounted just ahead of the intercooler in the pre-CAC ducting, but I don't have enough data to report from that sampling point yet:


The pyro probe is just behind the boost gauge.


The intake and exhaust have been heavily modified for maximum flow within the stock sheetmetal envelope (i.e. no stack through the bed, hood scoops, etc.). The exhaust is comprised of an Aeroturbine welded to the downpipe, followed by the cat-shell, which has a 65 degree downturn welded on the end.
Soot exits at the rear of the cab, underneath the H2O/meth injection pump.
As for the intake, this picture sums it up best:



Normal driving yields about a 5-10 degree F differential (in any temperature), while WOT (stock fueling) results in as much as 25*F differential before running out of road or RPM. On the dyno, delta differential is much faster than the street, since there's no airflow to speak of to delay the onset of heat soak. Of course, these values correspond to 32 psi max boost, so later this spring we'll have the data for boost in the 45 psi range.

p.s. Tyler, ULSD has 1% less energy content than LSD, which is essentially un-measurable on a commercial dyno.