As seen in Speedboat Magazine’s March 2020 Issue.
Force Feed or
Pump to the
I have noticed that you run 2- or 3-stage raw water pumps on your supercharged EFI engines. What compensations do you make in the program that addresses the fuel puddling in the manifold under the intercooler? Are you just adding more fuel at idle or is there some
I am currently force feeding my intercoolers but intend to rebuild the engines
and outfi t them with 2-stage water pumps, and a sea strainer for both the intercoolers and engines and remove the intercooler pickups.
The engines are custom built 509 cubic inch big block Chevys with WhippleChargers and MOAIC intercoolers.
Kim Bomanson Finland Aland, AL
Our first-generation TCM800 EFI engines were 509 cubic inches with a 3.3 liter WhippleCharger. Most of those were built with a single stage water pump and the boat was outfitted with a second water pick up and sea strainer for the intercooler. At that time, the program was developed for that set up and it worked well. The TCM800 EFI was built on the same well established and validated platform as its predecessor which was basically the same motor with a 10-71 roots blower and a pair of carburetors on top of a SuperChiller intercooler. With the roots blown motor, we found that the idle quality was better without water fl owing through the intercooler at idle. So, the same concept was initially followed with the first EFI engines.
As the power levels increased through the range of production motors, multistage water pumps became necessary to provide adequate engine cooling. Monitoring the manifold inlet temperature revealed that it was quite elevated at idle, so we changed to a standard of always pumping the intercooler with one stage of the pump.
It is a common occurrence for fuel to puddle in the manifold after the engine is shut off. This is especially the case when the fuel injectors are in the throttle body which means the air/fuel mixture is passing through the intercooler core. When the engine is shut off, the vapor turns into liquid and drips off the intercooler core. When the engine is first re-started after not running for 30 or more minutes, it draws the raw fuel that has puddled in the manifold which causes a momentary rich condition. Usually there is a puff of smoke out of the exhaust that some people mistake as burning oil. It is fuel.
The best way to tune your engine is the way it is set up with either water pumping through the intercooler or not. Honestly, I have not seen much difference in programing requirements related to pumping water to the inter-cooler. But I am sure it is better to have the water pumped to the intercooler all the time. Whenever
we do a Stage III or IV Whipple on a 600 SCi or 700 SCi, among other modifications, we add a 2-stage Latham pump that we developed to accommodate the Gen VI serpentine belt set up. The advantage is increased fl ow to the intercooler without robbing vital cooling water needed for the engine. We do not have a special program for the upgrade.
On Bravo-based installations, a Latham 2-stage pump has become our standard. But we still use two pick-ups per motor. One is the pick-up through the drive and the other is a remote pickup. Both of the water sources jointly feed a single sea strainer which feeds the raw water pick-up. We have found that redundancy of the two pick-ups feeding the motor ensures adequate water flow. Water that just enters through the drive pick-up is sometimes not enough because of restrictions caused by the smaller passages and hoses in the gimbal assembly. It is desirable to pass water through the drive which helps keep it cool. If only a hull pick-up is used to supply the sea strainer, then the gimbal should be modified to allow water to be force fed through the drive while under way.
Normally, each sea strainer is also outfitted with a pressure relief valve that dumps overboard. It is best to incorporate a flush system for each sea strainer that is plumbed to the bottom of the sea strainer below the screen. We normally install a flush fitting set-up on the transom in a discrete location that a flush hose can be connected to. This way, when the flush hose is connected to run the boat on the trailer, it flushes the sea strainer debris out through the pick-ups before starting the engine. Twin engine applications should have the sea strainers cross connected with an equalizing hose. This hose is connected to a bung that is below the screen. A valve can be placed in this line to isolate the motors for flushing purposes. The advantage of having the cross-over hose is to equalize the pressure from one engine to another during turns. This is especially important for catamarans. Having a crossover line also provides emergency cooling water to a side that somehow has the pick-ups plugged.
If the installation is on a boat with M6 or M8 drives (or any drive that does not pick up water), we use a Latham 3-stage pump with two stages feeding the motor and one stage feeding the intercooler. These motors are typically higher horsepower engines requiring more cooling. On these applications, larger pick-ups on the bottom or transom provide water supply through -20 to -24 hoses to the sea strainers. Adjustable transom pickups are the best way to go making it easy to dial in the correct water pressure without grinding or welding on the pick-ups after they are installed.
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