Yeah. I will next time I’m someplace I can try work at it without being bothered, so maybe next week.
First impression towing with 6.9 NA
- Thread starter Cubey
- Start date
Yeah. I will next time I’m someplace I can try work at it without being bothered, so maybe next week.
Fixnstuff
Full Access Member
Rather than do a write-up with no way to produce drawings I decided to spend time searching for videos and websites to better explain your situation AND FIND SOLUTIONS. I've probably spent 8-10 hours doing that and I'll post links to a few of those videos and web pages here.
I've discovered something NEW to me and that is vortex generators. I've been seeing videos and articles about them for years but never looked into those until last night.
As a preface to all of this, I've read that side winds are the cause of 1/3 of tractor/trailer accidents. Also consider the instabilities caused by excess turbulence in truck & travel trailer combination which increases the instability whenever a tractor/trailer rig passes you <- that instability is substantially reduced when you can improve the turbulence areas of your truck/travel trailer combination.
Vortex generators
Scientifically [/u]THEY WORK[/quote] to very significantly or substantially reduce drag and increase stability. They were originally developed for aircraft wings, I think by researchers at Lawrence Livermore Labs in association with NASA research, that should be in one of the videos below. The MFR that makes "Airtab" brand for vehicles (their only product) was nominated for a NASA Hall of Fame Award which they did in fact receive for their work in improving aerodynamics in vehicles such as trucks and trailers.
One thing that RV/Travel Trailer owners and OTR truckers consistently report with vortex generators is "much improved stability," and "much less spray behind the vehicles in rainy and snowy weather" for better visibility behind the combination. Improved stability and safety is probably the biggest benefit. Fuel savings reported can range from negligible to about 4 % depending upon the rig and set-up - but even at minimal fuel savings it adds up to probably pay the cost of the vortex generators within 1 to 5 years depending upon how far you drive each year. I am going to get some for my truck, back edge of my canopy the trailer I tow now and future travel trailers, unless it urns ou that I find and CAN AFFORD anything better.
I almost NEVER trust advertising and marketing propaganda about how well such things will work but in this case I am impressed because I've looked at the independent science and I am impressed with these. Also they are very versatile as far as applications and relatively inexpensive compared to other solutions.
There are other methods that may be BETTER solutions but they are not as versatile and they are more expensive. If I had a shop put together I could make it all myself but I don't have that convenience yet.
^You can disregard my personal opinions aout the vortex generators^
First a couple of videos that illustrate most of what is going on with your set up. From that you can figure out what options are best for you.
You have a lot of resistance (drag) right now, excessive in my opinion. When you double your speed (X2) that resistance increase by FOUR TIMES, X4 NOT X2. So, the resistance or drag at 30 mph becomes 4 TIMES greater at 60 mph. It's equivalent increasing the dimensions of your truck, camper and trailer as you go faster. So whatever you can do to reduce it is going to have a significant pay-off in towing performance AND SAFETY. In your case I also think you'll have a significant increase in fuel economy.
Lets look at aerodynamics first (the easy way). If specific products are mentioned I am not endorsing those products, these are just videos that I think best illustrate the aerodynamic problems.
Actually I have a bunch of these videos and web pages open in tabs but I seem to have lost the best one so I'll have to look for it. MEANWHILE I have to take a break right now for at least a few hours so I'll post this much right now, 2 or 3 videos and post the rest of the information later.
I started out by rating the videos and web pages by the letters A. B. or C. depending upon how good the information is.
The following video I listed as 'A.' mainly because it is from NAVISTAR and Lawrence Livermore Labs. Wind tunnel testing was done at NASA in the largest and one of the best equipped wind tunnels in the world. There are two videos on Youtube of a NAVISTAR tractor & trailer being lifted by a crane into the wind tunnel (which is considerably above ground) but there's no significant information in those, only the fact they did it in their 'program to improve aero dynamics' and one video includes an interview with a NAVISTAR executive at the wind tunnel set-up about this program. Interesting to watch but not enough info to include here.
You can stop this video at 1:28 to see a super computer simulation image of wind turbulence and resistance on the rig. Those low pressure areas where you see the turbulence is acting as though it's pulling the truck backwards. It's creating resistance and drag to forward motion. Shortly after that it looks like they are putting a divider in the gap as part of the correction but I can't be sure of that. This video doesn't show much about specific ways to correct those conditions but shows that these are areas that need to be improved and how they are approaching it.
A. HPC in Action: Navistar.
A. This is a product video but at about 2 minutes in, it shows an accurate computer simulation of the typical airflow over a tractor/trailer rig which illustrates the two main areas where you have problems but in fact you have actually THREE OR FOUR of these areas instead of just TWO. They are: The GAP between your cab and camper and also where the camper extends above and out beyond the sides of the cab, the BACK of your camper and truck, the FRONT of your trailer and the BACK of your trailer. The resistance on the front of your trailer (which is increased by the negative pressure (or vacuum) and the resulting turbulence at the back of your camper and truck) is very similar to the GAP between truck and trailer in the video, so you can look at that gap in the video as being similar to the space between your tow vehicle and the front of your trailer.
Airtab® Fuel Savers
A. This is an old video, (2013) from NASA. It's not specifically addressing your issues. I am putting it here to show that vortex generators have some extensive research behind them. I am NOT suggesting that this is the best solution, I mentioned them earlier in this post and I think they are an inexpensive and fascination innovation and just one possible option. I would like to make some myself with a 20 ton shop press and a die but I won't have a press until I move out of this state.
A. Micro Vortex Generators
I've discovered something NEW to me and that is vortex generators. I've been seeing videos and articles about them for years but never looked into those until last night.
As a preface to all of this, I've read that side winds are the cause of 1/3 of tractor/trailer accidents. Also consider the instabilities caused by excess turbulence in truck & travel trailer combination which increases the instability whenever a tractor/trailer rig passes you <- that instability is substantially reduced when you can improve the turbulence areas of your truck/travel trailer combination.
Vortex generators
Scientifically [/u]THEY WORK[/quote] to very significantly or substantially reduce drag and increase stability. They were originally developed for aircraft wings, I think by researchers at Lawrence Livermore Labs in association with NASA research, that should be in one of the videos below. The MFR that makes "Airtab" brand for vehicles (their only product) was nominated for a NASA Hall of Fame Award which they did in fact receive for their work in improving aerodynamics in vehicles such as trucks and trailers.
One thing that RV/Travel Trailer owners and OTR truckers consistently report with vortex generators is "much improved stability," and "much less spray behind the vehicles in rainy and snowy weather" for better visibility behind the combination. Improved stability and safety is probably the biggest benefit. Fuel savings reported can range from negligible to about 4 % depending upon the rig and set-up - but even at minimal fuel savings it adds up to probably pay the cost of the vortex generators within 1 to 5 years depending upon how far you drive each year. I am going to get some for my truck, back edge of my canopy the trailer I tow now and future travel trailers, unless it urns ou that I find and CAN AFFORD anything better.
I almost NEVER trust advertising and marketing propaganda about how well such things will work but in this case I am impressed because I've looked at the independent science and I am impressed with these. Also they are very versatile as far as applications and relatively inexpensive compared to other solutions.
There are other methods that may be BETTER solutions but they are not as versatile and they are more expensive. If I had a shop put together I could make it all myself but I don't have that convenience yet.
^You can disregard my personal opinions aout the vortex generators^
First a couple of videos that illustrate most of what is going on with your set up. From that you can figure out what options are best for you.
You have a lot of resistance (drag) right now, excessive in my opinion. When you double your speed (X2) that resistance increase by FOUR TIMES, X4 NOT X2. So, the resistance or drag at 30 mph becomes 4 TIMES greater at 60 mph. It's equivalent increasing the dimensions of your truck, camper and trailer as you go faster. So whatever you can do to reduce it is going to have a significant pay-off in towing performance AND SAFETY. In your case I also think you'll have a significant increase in fuel economy.
Lets look at aerodynamics first (the easy way). If specific products are mentioned I am not endorsing those products, these are just videos that I think best illustrate the aerodynamic problems.
Actually I have a bunch of these videos and web pages open in tabs but I seem to have lost the best one so I'll have to look for it. MEANWHILE I have to take a break right now for at least a few hours so I'll post this much right now, 2 or 3 videos and post the rest of the information later.
I started out by rating the videos and web pages by the letters A. B. or C. depending upon how good the information is.
The following video I listed as 'A.' mainly because it is from NAVISTAR and Lawrence Livermore Labs. Wind tunnel testing was done at NASA in the largest and one of the best equipped wind tunnels in the world. There are two videos on Youtube of a NAVISTAR tractor & trailer being lifted by a crane into the wind tunnel (which is considerably above ground) but there's no significant information in those, only the fact they did it in their 'program to improve aero dynamics' and one video includes an interview with a NAVISTAR executive at the wind tunnel set-up about this program. Interesting to watch but not enough info to include here.
You can stop this video at 1:28 to see a super computer simulation image of wind turbulence and resistance on the rig. Those low pressure areas where you see the turbulence is acting as though it's pulling the truck backwards. It's creating resistance and drag to forward motion. Shortly after that it looks like they are putting a divider in the gap as part of the correction but I can't be sure of that. This video doesn't show much about specific ways to correct those conditions but shows that these are areas that need to be improved and how they are approaching it.
A. HPC in Action: Navistar.
xc_hide_links_from_guests_guests_error_hide_media
A. This is a product video but at about 2 minutes in, it shows an accurate computer simulation of the typical airflow over a tractor/trailer rig which illustrates the two main areas where you have problems but in fact you have actually THREE OR FOUR of these areas instead of just TWO. They are: The GAP between your cab and camper and also where the camper extends above and out beyond the sides of the cab, the BACK of your camper and truck, the FRONT of your trailer and the BACK of your trailer. The resistance on the front of your trailer (which is increased by the negative pressure (or vacuum) and the resulting turbulence at the back of your camper and truck) is very similar to the GAP between truck and trailer in the video, so you can look at that gap in the video as being similar to the space between your tow vehicle and the front of your trailer.
Airtab® Fuel Savers
xc_hide_links_from_guests_guests_error_hide_media
A. This is an old video, (2013) from NASA. It's not specifically addressing your issues. I am putting it here to show that vortex generators have some extensive research behind them. I am NOT suggesting that this is the best solution, I mentioned them earlier in this post and I think they are an inexpensive and fascination innovation and just one possible option. I would like to make some myself with a 20 ton shop press and a die but I won't have a press until I move out of this state.
A. Micro Vortex Generators
xc_hide_links_from_guests_guests_error_hide_media
Fixnstuff
Full Access Member
So far this is my favorite video on the subject of aerodynamics in trucks! The video was posted in 2013 and it shows what Mercedes Benz was doing at that time.
I happened to notice some vents at the front edge of a tractor cab, near the headlights, that appear to be vortex generators and a large vent at the lower back on each side that might be vortex generators. I'm not certain about that but those are sure nice looking trucks!
Mercedes-Benz Aerodynamics Truck & Trailer
I happened to notice some vents at the front edge of a tractor cab, near the headlights, that appear to be vortex generators and a large vent at the lower back on each side that might be vortex generators. I'm not certain about that but those are sure nice looking trucks!
Mercedes-Benz Aerodynamics Truck & Trailer
xc_hide_links_from_guests_guests_error_hide_media
Fixnstuff
Full Access Member
One thing that I think I forgot to mention regarding air flow and this might help you to perceive what is happening with air flow since under normal circumstances you can't *see* air.
Air has FLUID properties, just like water and air currents perform and react in the same way that water currents do. I'm fairly sure that aerodynamics and hydrodynamics in fact use mostly the same formulas.
For example, when you put your flat hand out of a car window on the highway, it behaves just like a rudder on a boat in a water current or if your hand was placed into a water current. It's doing THE SAME THING whether it's in an air current or a water current, but the water is much denser so the pressures and forces are much higher.
You can often *see* water currents and how they change under various conditions, for example a stationary rock or log protruding above the water in a stream or river. You can see the High Pressure forming on the up-stream side, pushing up a wave, which also pushes the wave out at an angle as the water moves downstream. On the Low Pressure side, the downstream side you can see back currents and eddies, (swirls in the water) and some of the water moving UP STREAM into the low pressure area behind the rock or log.
Those effects continue down to the bottom of the stream or river. I have actually observed all of those affects from underwater in fast moving currents and was fascinated by it, I watched it for hours because it also explains how erosion works over thousands and millions of years to shape the land on our planet. I was studying geology a the time. I could see the pressures and eddies at the bottom of the rock or embedded log by watching how fine pebbles, fine grains of sand and silt moved around the object. (enough about errosion). Actually it's also similar or the same as the Venturi Effect with high and low pressures.
SO. To help visualise the aerodynamics of your vehicle, or tow vehicle plus trailer IMAGINE THIS:
In your mind flip it all upside down and imagine it as a boat and an attached raft, o platform of some kind that the boat is pulling. Also imagine that the water line comes up to near the top,which is actually near the under-frame after you rig is tipped over.
So now you have a boat and raft in the water. Your objective is to pull the boat and raft UP STREAM. You should be able to see what the current is doing against the surfaces of your boat and raft that are most resistant to your efforts to pull it up stream. At the same time picture the wind tunnel diagrams.
As stated, the water being much much denser, the forces are much much greater so this analogy greatly amplifies or exaggerates all of the effects of air currents when your truck and trailer are on the road. It's only meant to help visualise what the air currents are doing and where you might best apply some corrective measures.
I could have written that better but I am burnt out on concentrating and typing. I think you'll get the picture though.
Air has FLUID properties, just like water and air currents perform and react in the same way that water currents do. I'm fairly sure that aerodynamics and hydrodynamics in fact use mostly the same formulas.
For example, when you put your flat hand out of a car window on the highway, it behaves just like a rudder on a boat in a water current or if your hand was placed into a water current. It's doing THE SAME THING whether it's in an air current or a water current, but the water is much denser so the pressures and forces are much higher.
You can often *see* water currents and how they change under various conditions, for example a stationary rock or log protruding above the water in a stream or river. You can see the High Pressure forming on the up-stream side, pushing up a wave, which also pushes the wave out at an angle as the water moves downstream. On the Low Pressure side, the downstream side you can see back currents and eddies, (swirls in the water) and some of the water moving UP STREAM into the low pressure area behind the rock or log.
Those effects continue down to the bottom of the stream or river. I have actually observed all of those affects from underwater in fast moving currents and was fascinated by it, I watched it for hours because it also explains how erosion works over thousands and millions of years to shape the land on our planet. I was studying geology a the time. I could see the pressures and eddies at the bottom of the rock or embedded log by watching how fine pebbles, fine grains of sand and silt moved around the object. (enough about errosion). Actually it's also similar or the same as the Venturi Effect with high and low pressures.
SO. To help visualise the aerodynamics of your vehicle, or tow vehicle plus trailer IMAGINE THIS:
In your mind flip it all upside down and imagine it as a boat and an attached raft, o platform of some kind that the boat is pulling. Also imagine that the water line comes up to near the top,which is actually near the under-frame after you rig is tipped over.
So now you have a boat and raft in the water. Your objective is to pull the boat and raft UP STREAM. You should be able to see what the current is doing against the surfaces of your boat and raft that are most resistant to your efforts to pull it up stream. At the same time picture the wind tunnel diagrams.
As stated, the water being much much denser, the forces are much much greater so this analogy greatly amplifies or exaggerates all of the effects of air currents when your truck and trailer are on the road. It's only meant to help visualise what the air currents are doing and where you might best apply some corrective measures.
I could have written that better but I am burnt out on concentrating and typing. I think you'll get the picture though.
So has there been any improvement with the changes you have made? What kind of hills are you seeing? The reason I am asking is because I just got back from towing my travel trailer over the weekend and my vehicle setup is very similar to yours. It is a 7.3 NA with a C6 and 3.54 gears. Only difference is that it is in a van body. I was able to maintain 60-65 mph during the trip. This included the time that I was towing into a 15-20mph head wind. The trailer water tank was full for this trip as well. My speed is EGT (no power) limited. I keep it below 1100*. The trailer I pull looks similar to the one in your pic. See below:
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We’re you on interstates or secondary highways? The hills are different. I do a little better on interstates because typically the hills are graded less steep. It’s a little easier to stay at 60-65.
It seems like I’ve gone up 1mpg since the small timing pump advance, getting about 11mpg (roughly 20-30% city) but I can’t say it feels much or any different. I caught sight of some black smoke when taking off from a standstill yesterday but nothing super thick. It’s probably running retarded still but there is only so much I can do without a little help from somebody experienced with timing these things.
It was probably 2/3 hwy and 1/3 secondary roads. With the headwind I ended up at 9.85mpg towing. Usually I am in the 11-13mpg range.
I take a lot of secondary highways due to more rural areas I go to for free camping. Actually yesterday was the first time I was on an an actual interstate since I started out with the trailer a month ago.
Any updates?
I just got back from towing my trailer to Columbus OH and back for the weekend. About 3 hrs each way. On about 85% of the trip I was able to stay between 60-65mph. I was fully loaded with my family of 5, luggage and a full water tank in the trailer. My speed was EGT limited. I kept it below 1100*. There was 1 large hill/climb where I was slowed down to 45mph by the top. If I didn't care about EGT's and black smoke I probably would have lost less speed.
No other issue. Trans never went over 185* and engine tempt would climb until the fan would kick in and then drop. I will say that the sides of the doghouse in the van gets pretty hot when working the engine hard.
I was going to post in a few days after I give it a good highway run with minimal city driving.
I rotated the pump more, maybe a bit too far, it black smokes more taking off from a stand still, but seems like it does a little better at highway speed.
I can’t tell if it’s doing better mpg wise, the last tank got corrupted by having to back up a bunch, with getting out to look. That probably ate half a gallon to be honest.
The last tank including about 25-30% city was right in 10.0mpg but yeah. Stop and go murders mpg because so much gets wasted out the tail pipe.
Oh I should also mention I have around 25 gallons of water in the trailer I didn’t have before. And it still feels a little better than it did.
The last 1/4 of the the pedal doesn’t really help on hills, it just makes black smoke so I stay at 3/4.
I rotated the pump more, maybe a bit too far, it black smokes more taking off from a stand still, but seems like it does a little better at highway speed.
I can’t tell if it’s doing better mpg wise, the last tank got corrupted by having to back up a bunch, with getting out to look. That probably ate half a gallon to be honest.
The last tank including about 25-30% city was right in 10.0mpg but yeah. Stop and go murders mpg because so much gets wasted out the tail pipe.
Oh I should also mention I have around 25 gallons of water in the trailer I didn’t have before. And it still feels a little better than it did.
The last 1/4 of the the pedal doesn’t really help on hills, it just makes black smoke so I stay at 3/4.
Is the 10mpg you mentioned while towing or just regular mixed city/hwy driving?
Towing my trailer with a full water tank I get about 10mpg depending on terrain, wind, cruising speed etc.
Mixed city/hwy I get 15-17mpg depending on the same factors.
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10 was towing with about 20% city. Tons of stop and go. I hit almost every red light.
This last tank with 97% highway was 11.1mpg at mostly around 55mph, no bad hills, little to no wind.
Actually it might have been slightly higher, the nozzle was more geared for semis so holding at minimal pressure kept it from shutting off. Some spilled from overflowing. So maybe 11.2-11.3?
Not taking into account the odometer counting about 1 mile extra per 60 miles. I filled up 64 miles away according to google navigation and my trip odometer shows 65.
This last tank with 97% highway was 11.1mpg at mostly around 55mph, no bad hills, little to no wind.
Actually it might have been slightly higher, the nozzle was more geared for semis so holding at minimal pressure kept it from shutting off. Some spilled from overflowing. So maybe 11.2-11.3?
Not taking into account the odometer counting about 1 mile extra per 60 miles. I filled up 64 miles away according to google navigation and my trip odometer shows 65.
The 12.1 included some without the trailer. So 10-11 is about the range I get with the trailer, mostly highway.
I was getting roughly 10.5 city/14.5 hwy without the trailer after I put all terrain tires on last year. City is just what suffered, as it was about 11.5 before.
I was getting roughly 10.5 city/14.5 hwy without the trailer after I put all terrain tires on last year. City is just what suffered, as it was about 11.5 before.
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Having the van body helps a bunch. It helps push the air over the camper. I took my dads little camper with two different trucks. A long bed reg cab and a short bed ext cab. Both had soft tonneau covers. With the long bed it felt like the brakes were coming on at much over 60. With the short bed, effort didn’t change much with speed. Dad had the same observation towing it with and without the old man camper shell on a different long bed truck. If you want to improve highway fuel economy either slow down or get a topper. As much as I hate them, I’ve considered it for mine if we get the chance to go on a big road trip towing. FYI I get about 10 mpg towing too but that’s not at 60-65. Lol. You’d get killed out here doing that speed.
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