UK RV streamline a brick challenge. (Aero + other mods)
 

Hi,

set myself a challenge of improving the mpg of a 33' long 8' wide 11' high brick, aka my coach based motorhome / RV

last run had us getting 11.5mpg at a pretty constant 65mph on a motorway across england. It was late, I was tired, and I wanted to get home as soon as possible.

The next day, I started looking for ways to improve mpg - and for forums to help me. This one came up time and again, so I joined.

Starting with some simple bits

1) rear wheel covers
2) Tyre pressure to max sidewall (well, 105psi is all my compressor will do)
3) mirrors delete, camera replacement
4) Cold air intake - its a turbo diesel 5.8litre straight six


heres some pics of the delete mirrors. Note the steampunk use of copper pipe to house the ebay special mini cameras. The idea is that if I clip something, the pipe will swivel round on the munson ring holder.

Cold air intake - see how the air intake is right in front of the radiators? The air comes in from under the shelf the maglite is on, and is directed up to the radiators. However - in sunny climates, there is so much air coming in, that the blower for the cabin can only get hot air (the intake for this is 12" above the top of the rads). My only solution to this was to remove the front bonnet. The next, better, solution will be to separate the air for the rads from the air for the cabin. I will have to add a second blower for the rear of the camper as there isnt enough heat from just the cab blowers.

See the huge gap above the rads? that stuff you can see behind it - especially the silver blanket, is the engine. The engine sits between the driver and the passenger, so all that hot air, or cold air, depending on the weather, is being blown into the space around the engine. I think Ill block it off somehow.
Do I:-
a) 'join' the top of the rad to the top of the grille?
b) just block off where I have written 8"
if I do A, then theres no air for the blowers - that could be resolved with another grille though.
Need to do a grille block, but it has to be on a wire of some sort, as getting in and out is a pain.

Dumb q - how do I link to pics in another thread? - I dont want to double upload the same pics.

Simplest way is to right click in the other thread on the picture, select properties, copy the url for the pic there, then come here and click on the Insert Image icon that looks like a little mountain with a yellow sky up there, hit paste, Bada Bing....thats it.

ah - ie chuck {IMG} tags round the url then. some forums dont support that unless its a jpg etc.

right - heres the wheel covers, and the original mirrors for comparison.

http://ecomodder.com/forum/attachmen...2&d=1356624393

http://ecomodder.com/forum/attachmen...p;d=1356624556

(Thread relocated on request).

And... I'm subscribed.

So! We all know where the biggest single gain is to be found - dealing with the rear of the vehicle, aerodynamically. How far away is that on your list? Are you planning or even allowed to do it where you live?

as far as I know there is no practical length limit to a motorhome - bar percentage of overhang, which im nowhere near.

Plastic continuous hinge has been ordered, sheets of ally and rivets in the garage. Just how to attach it to the back is a differnt matter. I have the original blueprints for the vehicle - including the description of the framework.

on this scale, would it matter if the boat tail started a few inches inboard of the vehicle? the framework might be (I have yet to look) inboard, as the corner is just relativly thin fibreglass that offers no real structural support.

Boat tails are 15 degrees arnt they?

Have you seen this thread?

http://ecomodder.com/forum/showthrea...d-e-18151.html

Optimal Boat tails are more organic (ie. curvature) than a single straight angle.

Starting the tail inboard from the edges a few inches will work, but isn't optimal -- you'll lose some energy to trapped vortices/turbulence in the "gap" between the RV and where flow re-attaches to the tail.

yeah - read all that. amazed at the lack of change of the under body streamilining.

Anyone know if the top is really important with a boat tail in my config? considering the really rough surface with a pile of vents and three skylights....

Here's a free idea:
http://i.imgur.com/n67oH.jpg

You're welcome.

Wow, nice RV you have there to ecomod! I would try to make an airdam and pannel the underside. I think that's a spot where also a lot can be won. The wheelcovers are nice and ofcourse the Kammbach :) .

My major worry though, YOUR MIRRORS! You have huge blindspots without mirrors, I would say very very dangerous. Maybe some small round (concave?) mirrors can be put on just for safety? But it could also be that your camera systeam will be very good. With both a wide angle camera for the maximum viewangle and a normal camera for a more detailed view (tele).

I would be a bit concerned about the mirror-to-camera conversion but if you have the same field of view it could be fine I guess.

Have you considered a diesel performance chip and high-flow exhaust?

A vehicle that size sort of overpowers mirrors. I see you have smaller ones to view the front wheel and the bumper area. Do you just have the two? I could see one at each corner and one in the middle of the back.

If the cameras are low-light/infra-red capable they could be better at night than the stock mirrors.

I have a wide angle 120 degree camera on each side. My drivers side (right) has pretty good visibility, my passenger side has just the one camera at the moment, but I have spares, Im not sure where to put them at the moment - half way along? at the back looking forward / down?

The cameras feed a security camera type quad splitter, with easy buttons on it to select any one camera or split 4 ways. This then goes to an upscaler iScan Pro, which again has nice easy to use brightness / contrast knobs on it. This should allow me to adjust the picture quickly for best view given the circumstances (night time countryside, or in town). this then goes to a 15" monitor about where the sun visor is. I am going to keep the actual mirrors in a locker for a while, and then maybe sell the mirrors and get some smaller emergency ones. Maybe fit a single wide angle to the inside passenger A pillar.

The UK truck regulations specify that you need a plain flat mirror, plus a wide angle, plus a look-down mirror on the passenger side. I am not subject to those regs though.

Oh - and I have a normal reversing camera, on its own screen.

Chip? hahhahaha - no this is a 1996 vehicle with mechanical injection - a Bosch VE pump, so no electronics. High flow exhaust? Not exactly available off the shelf, and its pretty big - 2.5 or 3" diameter, but its limited by the exhaust brake (a valve that shuts the exhaust off for massive engine braking down long hills in the Alps)

OK, I understand your vision is good from the cab. I then guess streamlining will be the way to go. Give it a maintenance job and have fun. Drive safe and slow ;).

Which engine does it have, a Cummins?

No, there are other manufacturers in the world apart from cummins and chevvy.... ;)

Its an iveco / fiat "aifo" engine, number 8060.45b 5.8litre inline six. It is glow plug, bosch ve injection, but im not sure if its direct or indirect injection, some of the smaller versions (8040) which are just 4cylinder shortened versions are indirect.

How about boosting the turbo?

Iveco has some ties with Cummins anyways :D

Probably it's direct injection.

I have been doing a bit if researching, and there are several variants of my engine. They are all the same basic configuration, and use the same turbo, but the power output varies from 140 to 230hp, as stock. The only difference i can find is the lowest powe version hant got an intercooler (mine has). Mine is the 180hp version. Im not any good with diesels, but i do know that vw made several versions of the 1.9 tdi lump, and in england you can tell which someone has by how many letters are red on the boot badge, all black is 70hp, i in red is 90, etc. Correspondingly, and contra-instinctivly, the more power, the greater the mpg rating. so, is upping the available power on mine possibly going to improve mpg?

THere are times that the extra power would be welcome, like up long hills.

I hate typing on a tablet, its really awkward to edit.

Edit, its direct injection, as found in the genuine iveco workshop manual.... Poo, that means an awkward twin tank setup for veg oil.

how do other people with turbo-diesels with intercoolers fare with grille blocking? Surely blocking the air to the intercooler reduces efficiency, or does the rad get moved? My intercooler is directly in front of the main coolant rad, so one or t'other would have to be moved - I suspect the coolant would be easier / better to move as pipe length doesnt matter on water, but does on air.

The fuel-efficiency benefits from a higher power may also apply to your motorhome, it's all about how the engine is tuned. Injection timing, injector nozzles, camshaft, boost, there are many things that can be tricked to improve it for both power and fuel-efficiency.

It's more reasonable to move the radiator. I'd only move an intercooler if it was top-mounted like in my grandpa's Toyota Hilux - a front-mounted intercooler is always more effective due to the better air flow and lesser effects of the hot air convection inside the engine bay. But that leads to another question: where to move the radiator?

Yes, where indeed to move the rad. I have however fitted a duct to try to make most of the air go through the rad, rather than round it. Its pretty miserable here, so a partial grille block should be liveable with.

Got a mobile alignment company out, and for 60 quid ($97) he found a misalignment of 4 and 5 degrees, toe out. Wow. Set back to zero now. That should help.:rolleyes:

6" front air dam in place, with about 5" showing under the front bumper.

Hi Guyd I have a similar shaped brick only smaller. It is an all alluminium kurbmaster camper with a 6cyl 292 petrol engine. So far I have installed a camback, a partial boat tail if you can call it that, wings down the sides at the back about 150mm angled in at 15% forming a box shape, a grill block, a small air dam, fender skirts.I have found no noticeble improvement in mpg after testing for around 1000 kms I am still on or around 16 mpg (imp) there has been improvement in the stability of the van and I find myself driving 10% faster. I am in the process of installing a full belly pan and skirts down the side which I have not tested as of yet as it is not quite finished. I plan on changing the front bumper and scooping the air under in a smoother fashion. From my experience so far, I have a feeling that my gains will be minimum. I also plan on replacing the clutch fan for an electric one and removing the air polution pump this is where I think I will see some gains. All these aeros have made it quieter and nicer to drive but have done little so far to improve my fuel economy. I think you are looking in the right direction focusing on the engine and drive train. someone pointed me to a TExas study that said by installing a 140mm radius above the windshield on busses like yours would reduce drag substantially, how that will reflect on you fe with your roof is anyones guess. Good luck

Right, i know its not scientific aba testing, the traffic in the uk precludues that most of the time, but a several hundred mile drive reveals a new mpg - 14.75uk mpg which is about 12.2 usmpg from a uk 11.5, so an immediate 28% improvement from the last run.

Anyone know about allison at545 gearboxes, im sure mine isnt right, as i can do 50 to 65mph in fourth, at 2200rpm without the engine changing revs at all. Sure, theres going to be a bit of slip, but that much? 50 mph up hill, 65 on the flat, more than that downhill.

Edited to correct way round conversion, after 5 hours drive im tired.

I think you're going the wrong way with that conversion. 14.7 MPG UK is ~12.2 MPG US.

Still respectable for such a huge brick though.

Sam

There's your problem. :)

If your speed goes up while the RPM stays the same, it seems to me the clutch needs some work. Maybe take a look at it and try to find a new one?

Thanks btracing, but its an auto, not a manual.

Ok, that changes a lot, haha. Maybe a transmission flush can do some nice improvements than?

The weather is now pretty bad too, I guess no updates for the next two weeks or so. It's snowing right now here in The Netherlands, but you should be getting the motherload.

Its pretty miserable here too.

The tranny is supposedly reconditioned - well I should hope so - it cost me two and a half thousand pounds, plus a thousand to fit. eek.

Tranny will be fine than, it's a closed system. Good luck on the weather and aero :) .