View Full Version : Seasonal blend considerations

11th May 2012, 12:17 PM
There's not much going on right now on the forum so I thought I'd spark up a conversation on blend ratio differences between seasons and see if anyone would like to chat.
Southern hemisphere is coming on winter and I've been up early enough to see at least one frost so far. I notice the difference with the cool ambient temps in that the engine runs slightly noisier till it gets hot. I reason that this has to do with the fuel viscosity being heavier at the lower temperatures. The IP lift pressure at startup is showing up to 140psi at idle in frosty conditions. (For comparison, ordinarily 140psi is only at 100kph and hot running.) The heavy blends give more injection timing advance and consequently the diesel rattle we've all heard at some stage.

My fuel is normally mixed to a "whatever I can get away with" basis for the bought components. Normally this is petrol and diesel.
So, to explain, I add enough petro-diesel till my mix performs satisfactorily at the cold running temps. A max of 15 % petrol plus 10 % diesel. If I need more thinning, I add diesel till I get the sweet spot.

OK. Has anyone any comment? Or anything being done or trialled re season blends. Please remember the approach is from a blenders' point of view. Thanks.

11th May 2012, 05:33 PM
I have changed my blends a bit over the seasons over the years but doesn't
seem to change the performance at all on my Rodeo.
Maybe I'm in the sweetspot for whether conditions being near Sydney.
My normal blend 50 percent wvo 40 percent diesel and 10 percent petrol.
I have had the wvo up to over 60 percent and have not seen any changes.
I think it also comes down to the car you have, I recall my experience with
a Toyota hiace always having issues just on diesel and the different servo's
I would use, I could tell almost immediately if it was good quality or not
however with the rodeo it seems to run on anything and never notice a
performance change.
Have never been game to go much over the 60 percent wvo to see if it would run
any differently on a single tank blend .

Hey Mods:

Eeverytime I would use the percent symbol next to my numbers I get this %
instead of the percent symple hence the reason I have had to spell percent.

11th May 2012, 08:57 PM
Thanks for the reply.
Sydney wouldn't get the vicious frosts and the chilling breezes off mountains quite the same.
The 50-40-10 blend you speak of is in the 'well safe zone', at least it would be in my Hiace. I have run 80-10-10 before today, though not in winter.
But you're so right about the vehicle making a difference. Then there's the difference in the set ups as well.

I can spot the limitation in a blend by observing the IP lift pressure guage. If the blend is too thick for the ambient temp, the needle will give quick flicks or gyrate.
Give the motor and IP more time to warm and the problem will disappear completely. It could be that the extra viscosity is too much for the IP strainer, filtration or fuel lines.
It's surprising how small that IP strainer is. Fine for diesel no doubt, but push the boundaries with our fuels and that could be a bottleneck right there.

The percent thing, I find more chance of it working if you leave a gap between number and symbol. Doesn't always work. Admin knows about the issue. No drama

13th May 2012, 09:41 AM

With my 1980 300D I use 85/15. The car is starting fine after full cycle glow in our current nippy mornings. What has made a significant change to my morning starts recently was reaming out my glow plug chamber.

Cheers tbird650 and Neil


Happy Mothers Day MUM!

14th May 2012, 03:16 PM
Yes, it amazing what a good set of glowies makes. My van has no problem starting from cold on most any blend ratio I care to throw at it.
Hot restarting isn't quite as good, but it appears if I keep the petrol portion of the blend to less than 15 &#37; , it's much happier.
Another telltale sign that the ratio isnt as good as it could be is tailpipe smoke while idling at traffic lights. Driving, no excess smoke can be seen.
Amount varies depending on blend viscosity it seems. Is anyone getting the idling smoke??

15th May 2012, 09:42 PM
Yes! With the glow plug clean I timed the IP. I use to get Nil smoke at idle but now get minor white smoke. My merc mechanic told me (by memory, but don't hold me to it) too far retard is rough running and black smoke, too far advanced is white smoke .

16th May 2012, 06:05 PM
Ok. I've had the white smoke too. On one occasion it turned out to be exceedingly low IP lift pressure.

The warm up period is a time that I'd like to hurry through. The heavy fuel makes for slightly noisy operation when cold but settles once heat has soaked through the engine bay, IP etc.
For this reason I look to shorten the warmup phase. Another thought for cold running was to add extra diesel via a valve, perhaps after the filter. This would effectively thin the cold fuel and I could control the amount and duration. It wouldnt need much of a percent swing to make a useful difference.
In this way I could have a certain percent blend for start/warmup and another percent for hot running.
Just thinking out loud....

16th May 2012, 09:35 PM
Please forgive a biodiesel user from chiming in. Have you thought of using a veg therm kit ? I know we only have about 3 maybe 4 months of cold but it could make a lot of difference to your early morning starting.
For a little over a hundred dollar you could have quicker starts in the morning or any cold days.
I am considering one for my ML270 on bio to get the fuel up to temp earlier so there is less smell.


17th May 2012, 09:31 AM
Michael, thanks for the thought.
I've pondered over the idea of 12V heaters and I've made various ones a few years ago. One of the downsides is the amount of fuel per minute that these have to heat. I tested vehicle fuel flow once and it surprises. It was 500ml a minute, which I think I recall was at driving speed. There needs to be a serious amount of watts to make any meaningful impression on temps.

One possibility could be to loop the return during the warmup phase and so compound the generated 12V heat. Once everything is up to temps, the 12V could be cut and the fuel circuit unlooped and away we go. This has some good advantages in that the heat is applied from.... even before the engine is cranked if you choose to.

Also possible could be looping without any 12V heat assistance. This way means the fuel heat generated by the IP alone isnt lost to the tank. It would take the longest time of the methods to work.

Idea#3 is to loop the return but run through piping around the exhaust manifold/head area. There's been a lot of talk about how hard it is to control exhaust heat to the veg however it'd be only for a short time, can be done for almost nothing and it would be quick heat. Downside might be would any oil left in the piping could carbonize and could the pipework fracture with constant hot-cold. A carefully chosen spot to attach pipework may be a good compromise here, like for example bolting to the head in close proximity to the exhaust manifold. One other caveat to this method is that any fracture causing a leak would/could go un-noticed for the duration of the trip and a considerable amount of oil could be spilt on the road endangering motorcyclists amongst others.

More than ever, I need to know at what temps does my engine like it's fuel in the IP at. I've been trying to get to adding the temperature thermocouple to the IP and log the temps here but these Hiaces are difficult to work on so the idea keeps being put off. I hope to get to this shortly but it can't be before the weekend as then we celebrate our Dragbike racing Nationals win, so I've got the Team and supporters coming. Should be good fun though a seroius amount of organizing.
For those interested in a nostalgia dragbike win against the modern bikes, look here: Triumph Bonneville 750 Nostalgia Drag Bike Excalibur (http://triumphbonneville.blogspot.co.nz/)

17th May 2012, 06:14 PM
well done on the win, on such an old bike too looks like a real handful did you know Mark Miles and their Mitsubishi Lancer gsr? Looks like an EVO but its not.

20th May 2012, 09:47 PM
Thanks smithw
Yes, and a great night celebration it was too!

Oh, and a setback is my thermocouple I use for temperature monitoring has decided to become eratic. I guess it's time for a new one. There's some cheap ones on Ebay from HongKong or China. Anyone any experience with these suppliers or products? Thanks.