This is a premature question for me, but I am logging and collecting as much info as I can in the old brain carrier group before I start in on this next motor. From a stock block/factory set up, to a tunnel ram on the same thing...What is the change in the air efficiency? I know "bigger carb"...but how do you calculate for a tunnel ram?
You don't really calculate volumetric efficiency, you measure it on a flow bench. When you upgrade a carb, you move to the next restriction, usually the intake. Upgrade that and you shift to the exhaust restriction. Then the cylinder heads or cam profile. If you want to estimate VE of a tunnel ram engine to choose a carb, you will still not approach 100% VE without tremendous improvements to intake flow of the heads with exhaust flow to match and cam selection to make use of it. A really well built motor will still not exceed about 90-95% VE without forced induction. What are you looking to accomplish?
Good info, thanks. I'm looking to accomplish a 500+horsepower streetable motor, and for the money it takes for us poor folks, I'd like to try to maximize as many aspects as I can.
Sorry. This thread took a wrong turn. I guess a better way to ask the question would be....What is the best way to choose the correct CFM carb or carbs for a tunnel ram intake? Is there an unknown variable, or is it a+b=c? I know the generic range of carbs on each application, but just want to understand better if there is a proper way to figure for it to get optimum results? I'm sorry if it seems like I am "trying to sound smart". I thought maybe the correct keywords would attract the attention of people that know something. Trust me....I am an ***hole and **** where I eat often. I'm really trying to be good here. It's hard once you are in a habit.
What's the application? Here's the deal- You're talking about a large plenum here. You can choose a cam to maximize performance at WOT, or you can choose a cam to work well with it on the street. If you intend to race it, stuff like idle rpm and vacuum signal aren't really that important. If you intend to street drive it, they are. Big plenums change everything. Now more than ever before, tunnel rams can be made to work really well just about anywhere. But not everywhere. To answer your question directly- the addition of a tunnel ram on an otherwise mild/stock engine will aid the efficiency of the engine at a very limited rpm range. It will also become less efficient than the factory parts you're replacing at a much wider rpm range. I hope that helps.
I will tell you one thing, in 20 years of car hobby and racing, some professional work, I have never seen very few engines making 500 HP that I would call "streetable" that weren't running a very sophisticated EFI. Most carburated engines at that power are a handfull. High idle, lurching in and out of gear, etc. Tunnelrams look neat, but they are narrow focus, high rpm parts. They generally kill throttle response off idle because it takes a moment for the air/fuel mix to reach the cylinders when you crack the throttle. I have seen a couple of small volume rams on small displacement engines that were tollerable, but they didn't make 500 HP. I would suggest something you have a firm understanding of, unless you enjoy swearing.
I work better w/ swearing, and bath in it daily. I don't want' to build a motor that isn't atleast obscene, and a giant plaster ****** doesn't create 500hp.
Come on guys,,give him a break. Tunnel rams can be made very streetable,,with the right application. Tommy
Whats it for, a bathtub? No one can help untill we are told what this will go on. If you want the mathimatical version, it can be given. Or do you want to be helped with a general "what will work" on my motor.
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