tomcat

jspeeddemon - What setup are you running? Carb, intercooler and compressor? Any pictures?

jspeeddemon

I am running a 540 BBC, Canfield 350cc Aluminum heads, Stage 4 Procharger with dual carbs and intercooler. The boat is a 26' Daytona with XR drive and 1.50 gear ratio, turning 32 Bravo 1.
Initially had trouble with tyhe setup, I was real green on blow thru blowers, hell I'm still green but I learn everyday. I feel these Prochargers are designed for the masses, a generic to fit all applications, which is cool. However I am working on customizing mine to my boat. As mentioned earlier, the box
Tomcat-Loved your thread reply about the intercooler efficiency. The box has an offset in it, the carbs don't sit directly over each of the plenums, they are offset by 2" forward, so the air has to go thru the carbs and either bounce off of a shelf or make a turn left, to get down to the intake ports. I put a crank trigger ignition on mine, turned the base box around and lined the carbs up with the plenums. With your understanding of air give me some insight into the increased efficiency aquired by doing this. Also I ported the intake runners, blending the ports up to the flanges. I think there is a misconception among performance guys that the air gets blown in the cylinders no matter what the restrictions. However if it is true that a supercharger increases the density of air versus more quantity of air, then increasing the ability of the motor to breathe should result in more power and more efficient burning of fuel.
May I pose a question to you Tomcat? If a naturally apsirated motor takes in a coffee cup of air per valve opening as a rule of thumb, and a supercharged motor takes in that same coffee cup of air, just packed more tightly, then my theory would be correct. The inefficiencies in the intake head combination would stand as impediments to making power. Tell me if you think I'm on the right track. I doubt I'll ever get this system to burn clean with carbs and will eventually fuel inject this motor, for now just making it the best it can be.

tomcat

Your instincts are right. Supercharged engines respond to all the same airflow improvements as NA engines. Air is air. It has mass and it takes force to accelerate that mass. This applies when the air mass is accelerated from zero to some velocity at the inlet, but it also applies every time the air is required to change speed and direction. When changes in speed and direction are sudden, further resistance to air flow is caused by turbulence. Because the force driving the air through the "pipe" is the pressure difference between the two ends of the "pipe", these sources of resistance to air flow are often called pressure losses.

I didn't realize the dual carb box was like that. Your solution was smart and will reduce resistance to air flow. Sounds like it may improve fuel distribution too.

I agree that these kits are built to a price point and require massaging by the customer. That's exactly what I'm trying to do with the improved intercooler configuration. If we had a large budget, we would design a new EFI intake manifold, purpose built for intercooled supercharging, but instead we struggle with existing hardware.

I like your coffee cup analogy. It's true. The engine is a positive displacement pump, it always handles the same actual volume (ACFM). When you add the compressor and force more than this ACFM into the system, pressure and temperature go up because the actual volume is fixed. When this air passes through the intercooler, pressure and temperature go down because the actual volume is fixed.

Don't confuse this drop in pressure due to cooling with "pressure drop" a term often used to describe the resistance to air flow of an elbow or contraction or for that matter, an intercooler core. The resistance to air flow is a separate characteristic, and is more properly called pressure loss.

Turbojack

Jetting is perfect (at least I think) Last sunday I made about 15 runs at different rpm's (started at 2100 & at about 200+ each time) & checked plugs. Color was perfect evertime. Of course max rpm was only 4200. Jetting I have now is 68 primarys, 6.5 power valves & 83 secondarys. When I went from 8.5-6.5 it fixed the rich condition in the 2100-2500 range. NO BLACK on transom at end ofl day.

I PMed elimi & he is taking it easy on his motor but he has 26" prop 1.26 gears Had it running 90 @ 5000. He has a standoff box also.

I picked up a 26 & 28 prop to try for weekend.

I read on the procharger web site somewhere the other night & they were saying that a carb procharger system will put out more HP because the carb setup cools the air charge by 20-25 degrees more that if EFI is used.

cobra marty

Are your fuel pumps boost referenced? At 4000rpm and 5lbs boost your fuel might be dead heading. Take the S/C belt off and open the box and see if it pulls the rpms- sure at a slower speed.

excaleagle42

tomcat

hi,
i think my understanding of this system is correct. basically, the procharger system is a centrifugal pump used to increase the net positive suction head or NPSH of the reciprocating pump , the engine for more displacement. the more laminar the flow, the less frictional losses and heat there will be because of decreased viscosity of the charge. thats where jsspeeddemon did help his engine work more efficiently by turning the box around. where you confused me was, when the pressure was increased and routed through the intercooler, the temp decrease and pressure decrease is due to the molecules slowing down and the suction of the reciprocating pump? and an engine likes laminar flow, a heat exchanger or intercooler, likes turbulent flow. turbulent flow would be like increasing an intercoolers surface area to increase heat removal through conduction. i don't run forced induction, yet. but my question is, about running intercoolers. could they have baffles to redirect the charge and increase the efficiency of the intercooler without causing a restriction? and if using centrifugal, could some guys in the quest for more power be actually hurting themselves by going to a smaller pulley and increasing the heat of the charge because of pump slip?
thanks,
Fran

Turbojack

Fuel pump is the big aeromotive one for EFI engines. Yes it is boost refrenced. & have pressure gauge on top of box & on fuel line. As pressure goes up in box, pressure goes up on fuel.

Last night I was thinking maybe the coil??? Problem is motor does not miss out, it is crisp & clear. I am leaning towards the MSD digital box.

jspeeddemon

TJ-I think if your jetting is truly correct then surely you have ignition trouble. I think you won't find your solution in the smaller prop. Dave has a 28' V-bottom and he is able to pull a 32 pitch Bravo 1 to 5200 rpm with a 1.5 gear last year. That was with a set of Stainless Marine manifolds, I am talking the little ones designed for a naturally aspirated 502 or smaller, this year he will have the Lightning headers. We are expecting this same combination to go 5500-5600. You should be past that due to hull efficiency at if nothing else. Your idea to try the different MSD box is a good one. You be back to the 30 pitch when you get it right.

tomcat

excaleagle42 - You're right about intercoolers liking turbulent flow but that only applies to the flow through the fins of the core, which are designed to create turbulence and improve heat transfer by "scrubbing" the air against the fins more. Before and after the core you want slower, laminar flow to reduce losses and help balance air flow across the face of the core. The precaution you have to take is not to use too much core face area and slow down the air velocity so much that the fins do not have turbulent flow. With core size restricted by the size of the average engine compartment this isn't usually a problem.

In industry we design cooling coils for a face velocity of about 500 fpm. A 540 engine with 90% volumetric efficiency will bring in about 850 actual CFM @ 6000 RPM. The Procharger 504 intercooler core has a face area of 12" x 7" (0.583 ft3). So the face velocity is almost 1500 fpm. I believe that should be plenty for turbulence within the core. This is the reason why Spearco puts cores in series rather than in parallel when they want to increase capacity. It keeps the velocity up, but at the cost of resistance to air flow. It's also easier to distribute the air flow across the face of a smaller core, which can be a problem with the typical ducted intercooler configuration.

The temperature decrease after the intercooler is obvious, the pressure decrease is due to the combination of resistance to air flow and the drop in temperature. For more on this, check out my post on what's really going on in an intercooled supercharged engine.

jspeeddemon

TJ-I think if your jetting is truly correct then surely you have ignition trouble. I think you won't find your solution in the smaller prop. Dave has a 28' V-bottom and he is able to pull a 32 pitch Bravo 1 to 5200 rpm with a 1.5 gear last year. That was with a set of Stainless Marine manifolds, I am talking the little ones designed for a naturally aspirated 502 or smaller, this year he will have the Lightning headers. We are expecting this same combination to go 5500-5600. You should be past that due to hull efficiency at if nothing else. Your idea to try the different MSD box is a good one. You'll be back to the 30 pitch when you get it right.

Tomcat thanks for replying to my question, it reaffirms my thoughts, I will let you know about the results, and once I get a baseline I'll would like to talk to you about your intercooler.