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Author Topic: Top speed fuel consumption? How to calculate?  (Read 436 times)
stopintime
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« on: September 09, 2021, 12:22:27 PM »

Every annual Alps/Italy ride I get a few opportunities to floor it for 10-15-20 minutes. Autobahn and AutoStrada.

Track days almost double my consumption, but pushing air with 100% throttle opening is another thing. I have a feeling based on how fast I go from normal fuel levels to yellow light. My guess is somewhere around 4 liters pr 10km (~ a gallon per 6 miles?)

Anyone know the answer? Or how much per injection? How many injections per time unit?
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« Reply #1 on: September 10, 2021, 06:13:04 AM »

Injections per time unit? 1 per rpm. Iirc, most Ducatis have injectors that range from 150-195cc/min. That's a max that you can bump a little by raising fuel pressure.

It's considered that the tune should try never to exceed 90% duty cycle in most applications.

I wouldn't think as bad as 6, but you could easily be looking at 20-25 miles per gallon (not sure how that works out to liters per 10km)
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stopintime
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« Reply #2 on: September 10, 2021, 10:08:05 AM »

Ok - thanks a lot.

Assuming flat out means full injector capasity, so 175cc x 60 x 2 cyl = 21 liter / hour
Flat out (never 100% flat out for long) 200km/h
.... is 10 liter / 100km

Which is the same as my track day consumption and not nearly enough  Huh?

Dirty Duc: how sure are you about those cc per injector numbers?
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« Reply #3 on: September 12, 2021, 12:16:49 PM »

Krista at CaCW told me I'm on my own on this - trial and testing.

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« Reply #4 on: September 13, 2021, 01:06:48 AM »

With my NC30 race bike, I had a calibrated stick with a saw cut on it that corresponded to 5 litres of fuel in the tank when lowered into the fuel cap. The bike used 3 litres of fuel for 5-6 laps of the tight Broadford track. The stick went with bike when I sold it  Wink

Sounds like direction you're headed Grin
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« Reply #5 on: September 13, 2021, 01:29:26 PM »

Ok - thanks a lot.

Assuming flat out means full injector capasity, so 175cc x 60 x 2 cyl = 21 liter / hour
Flat out (never 100% flat out for long) 200km/h
.... is 10 liter / 100km

Which is the same as my track day consumption and not nearly enough  Huh?

Dirty Duc: how sure are you about those cc per injector numbers?
It's been 8 years since I researched it. So...

I was way off. CA-cycleworks says IWP 043 Brown band is for an S2R800. Here's specs for that injector according to https://www.thunder-max.com/techdocs/fuelinjectorspecs.pdf

Flow .................................................. Fully open
At 3 bar ..........................329 cc/min – 3.75g/s
At 4 bar ..........................377 cc/min – 4.30g/s
At 5 bar ..........................421 cc/min – 4.80g/s
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« Reply #6 on: September 13, 2021, 01:40:08 PM »

Also, "matched set"  Roll Eyes

I use a service like mrinjector.us for the stonking big LSR injectors. He flow tests them, cleans them ultrasonically, replaces any consumables like rubber o-rings and such, flow tests them, and mails them back with a before and after report and a couple of hard candies for not much $US. When they come back they are on advertised spec and match. Significantly cheaper than buying a new set every year, and methanol is hard on everything. They have always cleaned back up so far.
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« Reply #7 on: September 13, 2021, 05:51:49 PM »

Really handy specs.👍
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« Reply #8 on: September 14, 2021, 12:31:58 AM »

Since I really don't know; the injectors inject only during one stroke? Only while the intake valve is open? If so, it won't make the calculations easier.... 

Does a fuel map have numbers for this?
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« Reply #9 on: September 16, 2021, 08:18:52 AM »

You bunch of freakin' nerds  laughingdp




 popcorn
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« Reply #10 on: September 16, 2021, 08:28:46 AM »

I'm not sure how it's set up in a stock-ish bike, but it makes sense that each injector only fires once per cycle. I think one can adjust the injectors individually using guzzidiag or some other software.

I don't think the injections are particularly timed to the valve opening events, that tech has emerged in cars based on stringent emissions, but was not particularly common in the aughts.

The fuel map has numbers, but they are probably nonsense for a practical calculation. The map numbers are likely some percentage of a constant expressed in a number from 0-255 (0-100%). Some tuning software might translate that for you, but I have no experience with that.
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stopintime
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« Reply #11 on: September 16, 2021, 10:30:12 AM »

There are vehicles with 'live' consumption info. Previously based on a vacum instrument, but calculated now (I assume).

I can't remember what Stu/other guru told us, but amount of fuel can be injection duration and/or 'continuous' amount. I would guess duration.

If full flow is known and I apply it x degrees/%, then the correct answer can be calculated.


You bunch of freakin' nerds  laughingdp


 popcorn

What?
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« Reply #12 on: September 16, 2021, 11:42:18 AM »

What?
Precisely Cheesy
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« Reply #13 on: September 16, 2021, 01:48:57 PM »

How many what's?
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