supercharged 392 hemi liquid propane injection

[remcolent]

I'm building a 392 hemi with a 6-71 supercharger.
8.0 compresion ratio with 14 psi boost.
I want to run the engine on liquid propane ,
Becouse propane is a cheap fuel overhere , injecting liquid propane will cool the temp below the supercharger nicely.
8.0 compresion with 14 psi boost is to high for gas but great for propane .
I'm thinking of using a megasquirt ECU but I found the next problems.
1: The standard LPI pump gives a LPI presure of about 50 psi
above tank presure and tank presure is not constant.
how to get a fixed fuel presure about 150 psi.
The LPI injectors from vialle are rated at 50 hp per injector
this way I would need 2 injectors per cilinder , and the injectors have a ultra low Z , this is way to low for the megasquirt ECU.
Are there high volume injectors with a high to med Z ??

The other option is to use 16 vialle LPI injecors and let the megasquirt ECU controll the vialle ECU.

Thanks for any advice
Remco the Netherlands

 

[patprimmer]

You might want an ECU that has more power/features than the megasquirt.

You need to have the ability to adjust for variations in fuel pressure or you need to control the pressure to keep it consistent.

Heating the tank to a constant temperature that is a little over the highest possible ambient temperature will reduce pressure fluctuations.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dcasto]

I did a mixing similation and with 120 F aftercooled air and 100F propane mixed at 14 psi boost, the temperature entering the cylinders is 80F. With gasoline the temperature is 30 F. Both assumed a 15 to 1 mixing.

 

[franzh]

Heating the tank is not the answer since the tank will absorb heat from the return fuel line anyway, the current problem is how to shed excess tank heat.

Liquid injection injector flow rate based on temp is handled through injector pulse width. The only injectors I am aware of (in the US) that can handle liquid are the Siemens Deka II, please, please, do not even try to use a gasoline injector, it will NOT hold up.

The Vialle system is pretty good but rarely installed on your size engine application, especially when supercharged. 16 injectors may be the way to go, with a master/slave setup.

Franz

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[TStaples]

Another option would be to use a plate type injector manufactured by SMP. These are available in low volumes through a company called RC Engineering. They have a picture of 5 SMP produced injector variants plastered on their home page, with little RC Engineering labels wrapped around the injector's body location groove, listed as "high flow injectors". These should be robust enough for liquid propane use. I used to work at the facility that SMP now owns. I know we used to sell that injector type as a trimmer valve for LPG powered buses, although we didn't warranty it for such. We had no propane durability test capabilities, and chose to let the customer buy it, test it, and ensure that it would work.

There are both low impedance (Z - approx 2 Ohms) and high impedance (Z - 12-16 Ohms) variants available. If you want to stick with the Megasquirt, then this may be an option.

http://www.rceng.com/

-Tony Staples

http://www.tscombustion.com

 

[remcolent]

Thanks for the great info
the rceng injectors looks great .
if they can handle a 20 bar fuel presure I think that is the way to go.
Next problem will be to get the liqued propane at a stable 20 bar presure.

Remco

 

[franzh]

Hmm, a quick look at my temperature/pressure curve for propane at 20 bar shows about 140 degrees F. Toss in that US grade motorfuel tanks have 312.5 psig pressure relief valve ratings and there isnt much room for error.

The trick with liquid propane injection is controlling tank temperatures.

Now that we have a tank pressure of 280-300 psig, you have exceeded the refueling facility outlet pump pressure of about 90% of the refueling facilities in the US (typically 50 to 75 psig above saturation pressure). What this means is you will not be able to refuel your vehicle until the tank temperatures drop to a nominal pressure.

Liquid injection is without a doubt the next generation of propane fuel systems but there are a few teething problems. As for the injectors, they will have to hold the pressure you identify and retain an effective response at low engine speeds, something that is VERY difficult to do.

For what its worth, I have found that top feed injectors do not perform as well as bottom feed injectors at these pressures.

Franz

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dgallup]

I can tell you for a fact that the RC/SMP/SAGEM/Lucas plate valve injectors will not work at 20 bar. I know, I'm the design engineer.

 

[JimCasey]

remcolent: How is this engine to be used? Supercharged 392 Chrysler engines are drag-racing engines to me, meaning it will only run for 6 seconds at high revs. Possibly it is for a powerboat where it may run longer times and you will be able to stabilize the temperaures, revs, etc.

WHat you are doing with it effects the methods you can use to stabilize the fuel pressure.

 

[TStaples]

remcolent,

The RC Eng. (SMP) injectors won't do 20 bar. That's well above the normal operating range any traditional top, side, or bottom feed, liquid fuel port injector. Most run in the 2.5-5 bar range, with a few going a little higher (maybe 7 bar, but that's iffy.) I don't want to say that there aren't any out there that can do 20 bar, because there may well be. However, in 25+ years of working in fuel systems (gasoline, diesel, propane, CNG, biogas, syngas, hydrogen, etc . . ..), I've never come across one.

The main issue is that the magnetic circuit, especially on a high impedance (saturated drive) injector cannot produce enough force in the opposite direction to overcome the force vector that is the result of pressure times sealing area of the valve. Obviously, there are direct injectors that can handle much higher pressures, both liquid and gaseous, but I'm assuming you are only looking at port injectors.

I'm just curious. Why do you want to run such high pressures at the injectors? I've designed OEM injectors, and complete gaseous propane and CNG fuel systems for OEM's, and we never needed to run above about 35-50 psi for gaseous propane, and 75 psi for CNG, at the injector. The higher pressures complicate refueling as was mentioned above. I've never done a liquid propane system, so I'm curious if there is a special need (i.e. to prevent vaporization in the rail and/or lines?) or some other driving factor.

50 hp per cylinder is achievable on gaseous propane without much issue, at 3.5 bar injector delta, with commercially available hardware. It should be a snap with liquid propane because the fuel is so much more dense. However, I'm experienced enough to know the devil is in the details, and I'm guessing there is a gotcha with liquid propane at say 3-5 bar.

-Tony Staples

http://www.tscombustion.com

 

[remcolent]

@ patprimmer
What would be a suitable ECU that can handle the fariable fuel presure. I do prefer the megasquirt becouse there is a great forum and tons on info about this ECU.

@ dcasto
Are your numbers corect? I want to inject liqued propane not gasious, when injecting around 4000 cc of liquid propane a minut at max power this sure would cool the inlet temp a lot


@ franzh
If possible I would like not to use the vialle ECU vialle don't giva any info at all and even the injectors have to be placed by them .
The vialle system works verry wel but only on smaller engines with a max output of about 50 hp per cilinder
I'm aiming for at least the double of that.

@ jimcasey
It's not a drag or powerboat engine .
It is my daily driver!!
If used for dragrace only I would just go for alcohol engine.
I might go to the strip ocasionly but also tow my 32 ft airstream trailer with it.
I'm realy close to the german autobahn ( no speed limit there) The car is a 1957 imperial with all around porsche 32 mm thick brake rotors with 4 piston calipers , 4 link rear suspension , modern jaguar stearing setup , dry sump oil system , manual shift 4L80E transmision etc etc.

@ tstaples

Would it be possible to use a direct injector as a port incector ( GDI injector ) propane will not stay liqued at the low 3 to 5 bar.


Remco

 

[remcolent]

PS sorry for my not to good english typing I'm dutch

 

[patprimmer]

I don't know specific capabilities of various ECU, but Motronic, Microtec, Haltec are a few that spring to mind.

I am sure if you do a google search you will find plenty.

You will also find plenty advertising in car racing and hot rodding magazines.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[franzh]

I am personally aware of at least one liquid propane project that uses the OEM GM PCM to operate the injectors (already mentioned Siemens Deka II bottom feed) and the Rousch Propane truck uses almost an identical platform. Both of the manufacturers reflash the PCM for optimized performance but the OEM fuel look up tables will run the engine. The injectors and outlet orifices are specifically tailored for the engine displacement/HP levels.

In order to get liquid propane to operate at conventional pressures of 2 to 3 bar the temperature will have to be lowered to around -20 degrees F.

Franz

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[turbocohen]

Remco, forget about "fixed" fuel pressure. The deka II and other orifice plate injectors are flow limited as pressure increases. above 9barA the flow increase mapped to pressure starts to level off. Doubling the pressure does not double flow. If your injector is designed for lp as the Deka II LPi just might be (this is a hint) then as pressure increases so does opening time. These accidental engineering triumphs minimizes the calibration complexity and facilitates a wide range of pressures above 30barA.

On another note, your 392 with blower needs more flow than the std deka calibration is setup for but there is a high flow version out there for dodge viper v-10 racing calibration that might work if daimler will share them.

Lotsa o luck with your project dude, Turbo Cohen

 

[TStaples]

remcolent,

Theoretically, you could use a GDI injector as a port injector. However, the lower seal design on GDI injectors is usually optimized for high pressures and temps. It's usually teflon, instead of an elastomeric o-ring. That won't work very well as a vacuum seal in an intake manifold.

It sounds like turbocohen is familiar with an injector variant/family (Deka II LPi) that I am not. I'm familiar with the original Deka's and the Deka 4's, but not the Deka II LPi's. It sounds like they could be an option that's optimized for LP.

Since you are in Europe, you should check out AG Autogas, which is part of Teleflex GFI. I know they have an LPG solution. I'm not certain whether or not they have an LP solution.


-Tony Staples

http://www.tscombustion.com

 

[turbocohen]

Deka I, II and especially the IV will not open under typical LPi pressures. The Deka II LP version in concert with peak hold drivers will open well above the fuel tank PRD pressures on a hot engine with a weak battery/failed alternator.. The Pressure / volume flow rate is not linear but easily mapped for a PV correction as long as fuel rail pressure and temperature tables are available in the ecu's operating system. In fact the temp sensor is only really mandatory at startup but for OBD it should be there. Your 392 hemi project would be well served by a Tec3 ecu from Electromotive.

http://www.electromotive-inc.com/products/tec3.html

They have assignable channels that will do the job well.. That is the best aftermarket ECU for competition minded individual tinkerers in my opinion. Remember to go closed loop all the way to WOT unlike gasoline applications that require enrichment and use pyrometers during calibration.

Keep the board updated with your progress.

Regards, Turbo
Ask for Jim who owns the company and tell em turbo sends his regards.