PFF - Pennock's Fiero Forum, PDA Edition

Supernatural 3.7L 9,000RPM Project (Page 13/20)

Notorio

FEB 15, 10:30 AM

And folks like me appreciate being exposed to the thinking going on in the Forum. It's encouraging to see what can be done with the lowly 3.4 PR block, with 1 cam and valve train, and NA.

Just wondering if actively cooling the fuel, instead of the air, would help with timing/detonation ?? The incoming air has so little heat capacity compared to the liquid fuel, so (without the benefit of doing any calculations) it seems like a thermo-electric cooling block mounted on the fuel rail (?) could lower the temp substantially. Perhaps with a pre-cooling zone before the fuel rail?

sanderson231

FEB 15, 11:43 AM

quote

Originally posted by Notorio:

And folks like me appreciate being exposed to the thinking going on in the Forum. It's encouraging to see what can be done with the lowly 3.4 PR block, with 1 cam and valve train, and NA.

The heat capacity of air is about 0.25 btu/lb-'F and the heat capacity of liquid gasoline is about 0.6 btu/lb-f. At wide open throttle there is about 12 times more mass of air than fuel. You would have to cool the liquid fuel substantially to have a meaningful effect on the mixture temperature.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

lou_dias

FEB 15, 04:20 PM

No problem...we'll just add a freezer's heatpump to the fuel tank to keep it at 0C.

Oddly...this is the opposite of what Smokey would do...

[This message has been edited by lou_dias (edited 02-15-2023).]

ericjon262

FEB 15, 11:44 PM

the latent heat of vaporization of the fuel is what does the majority of the cooling, but reducing the temperature of the fuel can make a not insignificant difference in power. Moroso used to make a product called a "cool can", it was a can with coiled tubing inside that could be filled with ice water, for cooling the fuel. realistically, the idea of cooling the fuel is only really viable for short duration operations, your heat sink has to be colder than the heat source to adequately remove heat. if you fuel temp is above ambient temperature, a small liquid to air heat exchanger could remove some of the heat, but would only be marginally effective.

Fuel vaporization is extremely effective at reducing charge temperatures, which is why carburetors can sometime outperform fuel injection systems when properly sized. that said, injectors placed further up the runners in the intake tract, or even above the intake tract, can have the same effect. the downside to moving the fuel source that far from the port/valve, is that it has longer to travel to get to the chamber, and can make throttle response and tip in tuning a little more difficult, along with requiring larger acceleration enrichment or pump shot to get a smooth transition from idle. a good compromise could be to run staged injection, with small port or direct injection handling transitional fueling, and high mounted injectors handling steady state fuel, I'm not sure there's currently support for such a fueling concept at the enthusiast level yet though.

For a while, I considered building a heat exchanger to go inside my A2W intercooler reservoir that would have a loop off of the air conditioning system to provide cooling to the intercooler water below ambient. if I were to do this, I could also install a small liquid to liquid heat exchanger in the fuel line, and run the supply from the intercooler pump through it, but, this seemed like a complicated solution, to a fuel temperature problem that doesn't really exist. I still may implement the AC mod though one day.

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"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."

I invited Lou Dias to trash me in my own thread, he refused. sorry. if he trashes your thread going after me. I tried.

zkhennings

FEB 16, 01:02 AM

quote

Originally posted by ericjon262:

Fuel vaporization is extremely effective at reducing charge temperatures, which is why carburetors can sometime outperform fuel injection systems when properly sized. that said, injectors placed further up the runners in the intake tract, or even above the intake tract, can have the same effect. the downside to moving the fuel source that far from the port/valve, is that it has longer to travel to get to the chamber, and can make throttle response and tip in tuning a little more difficult, along with requiring larger acceleration enrichment or pump shot to get a smooth transition from idle. a good compromise could be to run staged injection, with small port or direct injection handling transitional fueling, and high mounted injectors handling steady state fuel, I'm not sure there's currently support for such a fueling concept at the enthusiast level yet though.

Actually I am pretty positive the MS can do staged injection, it is used on some motorcyles.

ericjon262

FEB 16, 01:40 AM

quote

Originally posted by zkhennings:

Actually I am pretty positive the MS can do staged injection, it is used on some motorcyles.

it has the availability to do staged injection, I'm just not sure it can do it in the manner I described. because my engine isn't anywhere near a power level that could possibly require it, I haven't really explored. it. it could be very interesting to explore, and I might on one of my next builds. but I suspect that won't exactly need the fuel flow either.

sanderson231

FEB 16, 11:09 AM

quote

Originally posted by ericjon262:
For a while, I considered building a heat exchanger to go inside my A2W intercooler reservoir that would have a loop off of the air conditioning system to provide cooling to the intercooler water below ambient. if I were to do this, I could also install a small liquid to liquid heat exchanger in the fuel line, and run the supply from the intercooler pump through it, but, this seemed like a complicated solution, to a fuel temperature problem that doesn't really exist. I still may implement the AC mod though one day.

See this:

https://www.electrifiedboos...ling-with-freon.158/

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

ericjon262

FEB 16, 10:47 PM

quote

Originally posted by sanderson231:

See this:

https://www.electrifiedboos...ling-with-freon.158/

right, and I agree with the ideas of that thread, the capacity of the water would only be good for a short duration, similar to adding ice to the tank, the key advantage I see, is that you don't need to add more ice between runs, or drain water out as you add ice. that said, I don't think the juice would be worth the squeeze.

sanderson231

FEB 17, 10:28 AM

quote

Originally posted by ericjon262:

right, and I agree with the ideas of that thread, the capacity of the water would only be good for a short duration, similar to adding ice to the tank, the key advantage I see, is that you don't need to add more ice between runs, or drain water out as you add ice. that said, I don't think the juice would be worth the squeeze.

Compared to a standard liquid to air intercooler freon chilling should be able to decrease the charge air temperature by over 60 'F which will increase the density by over 10%. Mass air flow gain is probably something less say 7%.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

ericjon262

FEB 17, 04:43 PM

quote

Originally posted by sanderson231:

Compared to a standard liquid to air intercooler freon chilling should be able to decrease the charge air temperature by over 60 'F which will increase the density by over 10%. Mass air flow gain is probably something less say 7%.

but how long that could be sustained would depend on a number of factors, and typically, PCM's disable the AC at WOT, so the system would only function at some threshold below that. it also takes power to run the system, so the gains from the reduced air temps, and increased air density need to surpass the drag caused by the compressor, and the compressor needs to be able to maintain the system at the lower temperature, while not operating at WOT. for a true racecar, the system is also heavier, on a car that's already heavy, the difference might be negligible, on a stripped down lightweight chassis(without AC), it could make a difference.

For drag racing, IMO, the system is too complicated to be worth it, ice is cheap... For other types of racing, I would want to review data logs and see how the air temp changes over the course of a lap(s) with and without ice, and see how high steady state is once the system is heat soaked, and how long lower temps can be maintained with ice in the water box. I would also want to optimize the cooling capacity of the radiator for the intercooler as well before adding additional cooling measures.