Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

General engine tech -- Drag Racing to Circle Track

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby joe 90 » Wed Sep 13, 2017 3:26 pm

EGR is more for emissions.

There's plenty of engines made without EGR but maybe not in US of A.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby turbo2256b » Wed Sep 13, 2017 5:02 pm

EGR is more for allowing more advance at steady speeds. It allows what vacuum advance could back in the days of good fuel. Its one of the reasons my 87 grand marquis with a 3.55 rear got 32.9 MPG highway and 23 or so in town. wITHOUT IT had to reprogram the computer like it was all mechanical advance

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby Brian P » Wed Sep 13, 2017 6:10 pm

turbo2256b wrote:Without EGR fuel economy will never be all that great.


Lots of engines to this day don't use an explicit EGR system. The Chrysler Pentastar in my van doesn't have an EGR system, the Fiat MultiAir engine in my daily driver doesn't have one. Mazda Skyactiv engines don't have EGR.

But - these engines are using variable valve timing, and may be playing with the valve timing to achieve a similar effect.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby Circlotron » Thu Sep 14, 2017 6:49 am

NewbVetteGuy wrote:If I understand correctly, David's statement left out the 4th major factor which is the starting droplet size (although he spoke to it later); surface area to volume ratios are much higher with smaller droplets, hence my desire to focus on an injector that flows enough fuel with the smallest possible starting droplet size.

Some people say that small amounts of acetone + xylene mixed with gasoline lowers the surface tension, allowing smaller droplets to be produced by the injector. Never tried it myself.

Edit -> seems it's a bit of an urban legend, and acetone can be harmful to some fuel system components.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby integrale Evo » Thu Sep 14, 2017 7:37 am

Injector Dynamics are one of the best around and based on Bosch injectors. The 1050cc is the smallest they do now though as they reckon they've got it down to such a fine art that it will be ok even for lower power applications than before.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby mk e » Thu Sep 14, 2017 11:03 am

integrale Evo wrote:Injector Dynamics are one of the best around and based on Bosch injectors. The 1050cc is the smallest they do now though as they reckon they've got it down to such a fine art that it will be ok even for lower power applications than before.


Yup, as long as you have a set up that can accept their calibration data.
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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby panic » Thu Sep 14, 2017 12:59 pm

Read Vizard on displaced charge factor: complete atomization (vs. coarse droplets) replaces air molecules.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby MadBill » Thu Sep 14, 2017 3:28 pm

The definition of atomization is "to reduce a liquid to a very fine mist". A mist is liquid particles suspended in a gas, so they must in turn be vaporized before they displace any charge air. In practice of course potential conditions are more of a continuum from big coarse drops with little vapor at one extreme to nothing but vapor at the other.

Some years ago David Radzus produced some formulae here that correlated air density increase due to the latent heat of the vaporized fuel vs. its charge displacement effects. AIR, in most cases the latter somewhat outweighed the former.

Of course, lighting it off in the cylinder can only occur once it's a vapor...
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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby Firedome8 » Thu Sep 14, 2017 5:25 pm

Brian P wrote:
turbo2256b wrote:Without EGR fuel economy will never be all that great.


Lots of engines to this day don't use an explicit EGR system. The Chrysler Pentastar in my van doesn't have an EGR system, the Fiat MultiAir engine in my daily driver doesn't have one. Mazda Skyactiv engines don't have EGR.

But - these engines are using variable valve timing, and may be playing with the valve timing to achieve a similar effect.


EGR also reduces pumping losses at part throttle increasing efficiency.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby Newold1 » Thu Sep 14, 2017 7:45 pm

The suggestion to talk to some injector builders is the best one. Injector Dynamics, Five-O-Motorsports, Maren, RC injection, etc. these companies can give you some worthwhile data and suggestions to improve the "atomization" and please realize many brands of injectors can have various tips and nozzles changed for different delivery sizes, strengths and patterns that all affect "atomization.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby Brian P » Thu Sep 14, 2017 9:12 pm

Firedome8 wrote:
Brian P wrote:
turbo2256b wrote:Without EGR fuel economy will never be all that great.


Lots of engines to this day don't use an explicit EGR system. The Chrysler Pentastar in my van doesn't have an EGR system, the Fiat MultiAir engine in my daily driver doesn't have one. Mazda Skyactiv engines don't have EGR.

But - these engines are using variable valve timing, and may be playing with the valve timing to achieve a similar effect.


EGR also reduces pumping losses at part throttle increasing efficiency.


In the days before variable valve timing, that was done using an explicit EGR valve. Nowadays, a common approach is to delay all cam events at part load and cruising revs. Delaying EVO makes the piston extract more of the expansion energy. Delaying IVO and EVC well past TDC recirculates some exhaust into the next stroke, giving "internal EGR" without actually having an EGR system, and by displacing some of the following intake charge, it requires less (or no) throttling in order to reduce engine torque output. Delaying IVC well into the compression stroke allows it to push some of the intake charge back out again, thus reducing engine torque output without having to throttle it. The engine torque output can be varied by varying the cam timing without having to use the throttle much.

This doesn't have much to do with injectors and atomisation ...

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby tt 383 » Thu Sep 14, 2017 9:43 pm

I haven't seen anyone mention the billet atomizer injectors from Moran Motorsports... might be worth a look?

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby chimpvalet » Thu Sep 14, 2017 11:46 pm

Regarding displacement of air charge isn't the air-fuel ratio usually referred to weight based? In terms of volume a weight-based 12-1 AFR would perhaps be more like 450-1 as I understand it.

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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby mk e » Fri Sep 15, 2017 6:43 am

chimpvalet wrote:Regarding displacement of air charge isn't the air-fuel ratio usually referred to weight based? In terms of volume a weight-based 12-1 AFR would perhaps be more like 450-1 as I understand it.

Yes, normally by weight but molar ratio is what you're really after from a combustion stand poiny....but can be different from a hp stand point .

Rhe required amount of fuel as a liquid takes up very little space in the cylinder, but quite a bit as a vapor. If we call gasoline octane at c8h18, you need 17 O2 molecules to burn it, O3 is 20% of air and the ideal fas law says eqch molecule takes about the same space, so about 1 in 86 is fuel, or 1.1% if its fully vaporized...but it's really a little more than that because gas is not really all c8h18.

That is the argument against vaporizize.

The argument FOR vaporizing is that you can cool the intake charge....about 10-15C which eill increase the air density by about 5-7%, minus the volume loss to the fuel yields a ney 4-6% up gain. But this only eorkd if you vaporive in a fliwing air stream so you ate actually cooling the air. If you vaporize by spraying against a clised intake valve you are cooling the valve and port take a bit of load of the radiator not cooling the air much and not adding up. This is why big carbs on a tunnel ram generally out hp port injected setups and why shower injectors are used, and why place like injector dynamics sells HUGE injectors with well defined short pulse info to allow them to by used at 30-40% duty cycle so they only spay into a moving air charge.
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Re: Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

Postby Cutlassefi » Fri Sep 15, 2017 8:11 am

NewbVetteGuy wrote:
digger wrote:


I remember reading that some injectors respond well to more pressure (maintains a good spray pattern with smaller droplets) and some respond poorly. Correct From what I've seen and heard both from FIC and on here, the Bosch IIIs seem to be injectors that "like" more pressure. They may be designed to operate at a specific pressure, that's the difference. I am mildly concerned that their response times / latencies aren't great to start with and increase the pressure from 3 bar to 5 bar is only going to make that worse, though... not necessarily, again depending on the design of the injector.

Adam


And don't forget about inj timing. If it's injecting at exactly the wrong time (right around overlap) it will effect fuel consumption more than most anything else.
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