Eddieb's DR build thread.

[5150]

There's been plenty of oil threads throughout history, what about a DR petrol discussion?

What do you run in your DR, 91, 95 or 98?

I ran 91 in the mighty cheap DR for the first half dozen tanks then for the last 3 tanks I have been running 95. Unfortunately I don't have any firm economy figures to compare between the 2 grades but anecdotally I'm getting about 1-1.5km/l better on 95. As an added bonus the butt dyno indicates the bike is far more responsive when running on 95, especially in the mid range.

My car was in the shop yesterday for a wheel bearing and the garage owner asked if I was running on 91. After taking the car for a drive he had noticed it was low on power. He also claimed running my car on 91 would clog the oxygen sensor requiring a significant repair, and delivery lower economy. His opinion is that 91 is a crap fuel and shouldn't be run in anything. We then got into a DR discussion as he has a DR250 and a XJR1200 and is looking for a cheap DR650 for his son. His recommendation for the 650 was to run it on 95 also.

What say you?

JET FUEL!!!!

Just kidding.

I was told by my mechanic that DR650's were designed to run on 91. Being that people take them to 3 world countries where petrol is less then desired grade, they werent designed to run on anything high octane. It kind of makes sense, but I do agree in that I would not even run 91 in my lawn mower if I can help it.

[Phreaky Phil]

JET FUEL!!!!

Just kidding.

I was told by my mechanic that DR650's were designed to run on 91. Being that people take them to 3 world countries where petrol is less then desired grade, they werent designed to run on anything high octane. It kind of makes sense, but I do agree in that I would not even run 91 in my lawn mower if I can help it.

I run mine on 91. Seems to go well enough !

[bart]

I always go for higher octane when available. I don't think 98 has much advantage over 95 unless tuned for it. 91 is crap. I've owned a few cars that wouldn't run well on 91.

The only thing I run on 91 is wifey's car It's modern and should handle it.

In saying that, the DR is so lowly tuned it could probably run on donkey piss.

[NordieBoy]

I only run 91.

Tried higher octane but 91 gave the best bottom and mid range performance and better mileage.

The Nordie was the same but the VT250 hated the stuff.

[Eddieb]

More Fuel Analysis

To earn a crust I sit at a desk all day and pretend to do a job that has the word 'Analyst' in the title.

With that in mind I had a think about this today and the results are below. Bear with me, doing the calculations is easier than explaining it. Prepare to be geeked:

Some people run 95 because they believe that 95 is a better fuel, and some people run 91 as they believe that it's a sufficient fuel but cheaper and hence their running costs are lower.

I checked todays average petrol prices for Shell service stations in Wellington on pricewatch.co.nz.

91 is $2 18.8/litre, so 16 litres = $35.00
95 is $2 25.9/litre, so 16 litres = $36.14

So first off the price difference between filling with 95 vrs 91 for a DR650 is only $1.14 (IMS tank, 16 litres = full to reserve).

Now from recent riding I know:
On 91 I’m getting about 20.00 km/l so 16 litres takes me 320km.
On 95 I’m getting about 21.17 km/l so 16 litres takes me 338km.

(The 91 economy is estimated based on mileage I was getting with the stock tank but if anything I've been a bit generous and it's likely to be closer to 19-19.5. I was mostly getting 180-190km to a reserve of 10 litres)

So for the same quantity of fuel the distance travelled is greater, I'm getting better economy to the tune of an extra 18km. This straight away would support the theory that 95 is a better fuel.

So, if we ran the DR on 91 gas, how much more does it cost to do the extra 18km to equal the distance 95 gives us.

18km @ 20km/litre means we’d need to buy an extra .9 of a litre of 91 to do the extra 18km.

So the cost of 91 gas to do the extra 18km is $2 18.8/litre x .9/litre = $1 96.9

As we found above the cost difference to fill the tank with 95 = $1.14

So to do the same distance on each fuel $1 96.9 for 91 minus $1 14 for 95 = 82.9 cents per tank difference

This means it's cheaper use 95 than it is to use 91 by 82.9 cents.

So for me that settles it, I’m better off running 95 over 91 because:

• I get better fuel economy which equates to more distance per tank. In real terms I have less reliance on finding a fuel stop while out on rides and can explore a bit further down tracks before I have to worry about gas.
• It's 82.9 cents cheaper to cover the same distance on 95 than it is on 91. Over the long term running costs are lower on 95, even though it's a marginal difference it shows that running on cheaper 91 gas is a false economy
• A Less quantifiable but just a valid result is that I get better responsiveness from the bike, particularly in the mid range on 95.

YMMV, don't sue me if your findings are different.

[GSers]

Yeah and if you got rid of that FCR you would get even better Kms to the litre.
But its all about compression ratio and octane rating the higher the compression the higher the octane you require hence racing engines use Avgas with lead in it. So if you where to used 98 you should see even better mileage given you ride in the same style. The higher compression and higher octane gives a better flame burn across the top of the piston and better throttle response
GSers

[bart]

Good stuff.

Now try a couple of tanks of 98 and see what happens.

[bart]

Yeah and if you got rid of that FCR you would get even better Kms to the litre.
But its all about compression ratio and octane rating the higher the compression the higher the octane you require hence racing engines use Avgas with lead in it. So if you where to used 98 you should see even better mileage given you ride in the same style. The higher compression and higher octane gives a better flame burn across the top of the piston and better throttle response
GSers

Hey GSers....how about diesel, or does that only work in BMW's???

[Eddieb]

Yeah and if you got rid of that FCR you would get even better Kms to the litre.
But its all about compression ratio and octane rating the higher the compression the higher the octane you require hence racing engines use Avgas with lead in it. So if you where to used 98 you should see even better mileage given you ride in the same style. The higher compression and higher octane gives a better flame burn across the top of the piston and better throttle response
GSers

The FCR isn't fitted yet, I'm still running the stock BST40.

[GSers]

Good on yeah Bart, actually it sucked all the way across the Gentle Annie. Even though it was all drained out it was pinking across there. Much better once it got a top up of 98 in Taihape.
GSers

[GSers]

The FCR isn't fitted yet, I'm still running the stock BST40.

Best you stop worrying about fuel economy now then, because as soon as you fit it everytime you twist the throtle you dump a spoon full of petrol down its throat. There goes the fuel economy.

Guys have a good weekend ride safe

GSers

[NordieBoy]

Best you stop worrying about fuel economy now then, because as soon as you fit it everytime you twist the throtle you dump a spoon full of petrol down its throat. There goes the fuel economy.

I'm getting better economy from the FCR than the BST.

[bart]

Good on yeah Bart, actually it sucked all the way across the Gentle Annie. Even though it was all drained out it was pinking across there. Much better once it got a top up of 98 in Taihape.
GSers

Me and Mark both had the same problem after filling at the same gas station (not the filling up with diesel thing). I kept unscrewing the fuel cap, thinking I had an air lock/fuel starvation problem, but it was obviously just crap gas. I wonder how often that happens???

[warewolf]

Good analysis Eddie, if a little convoluted. Fuel comparison is simply km between fills, L to fill, $ to fill; yields L/100km and $/100km. Tank size doesn't matter.

Sydney taxis only ever talk about costs in $/100km, so early on that's the unit I adopted. Data gets punched in to a spreadsheet with the calculations already in it, I just record date, odo, and cost; and then point it at the last row with the same item (eg rear tyre, or fuel). The spreadsheet then shows things like distance and $/100km for that item. Too easy, and beats the hell out of anecdotal comparisons and fishing tales.

Another way to look at it: 95 is almost always 5c dearer (although now we are seeing 7-8c often) so at roughly 200cpL the price difference for 95 is 2.5% increase. So if your mileage improves by > 2.5% then 95 is worth it.

[Woodman]

I always go for higher octane when available. I don't think 98 has much advantage over 95 unless tuned for it. 91 is crap. I've owned a few cars that wouldn't run well on 91.

The only thing I run on 91 is wifey's car It's modern and should handle it.

In saying that, the DR is so lowly tuned it could probably run on donkey piss.

For a non DR perspective.

My non DR gets better kilometreage on 95, but the bottom end is terrible. On 91 the bottom end is great and the motor runs a lot nicer with a broader spread of power meaning I can generally run a gear higher on my non DR.

be careful with cars on 91 bart, my old Focuses only ran on 95 cos they had a 12.5 to 1 compression ratio. If you run these sort of motors on 91 the knock sensors take over and retard things to buggery.