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Tunnel Ram Engines

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Old 11-09-2006, 10:35 PM
  #61
bob
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Default Re: Tunnel Ram Engines

EFI driveability is super. Works super on the highway. When water/moisture come into the equation it becomes a different situation. You really need O2 sensors in the exhaust system and they don't mix with moisture. Played with a pair of the motors below for two years...went to blowers with carbs and life couldn't be better
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Old 11-10-2006, 01:43 AM
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Default Re: Tunnel Ram Engines

Did somebody say "automotive environment is more hostile than the performance marine environment"? Did somebody REALLY say that?

Did somebody say that the additional hours required of an automotive motor were one of the factors? Did somebody say that underhood temps of -30 degrees to 175 degrees were one of the factors?

Excuse me while I go drive my car to the market and back, never seeing over 2600 rpm, and never seeing more than 80 of its 320 available horsepower.

I guess I will touch on the temperature claims first...
If an automobile engine is started at -30 degrees, then it will obviously be in need of running a winter grade of oil, preferably a synthetic. It will be in need of a fuel control system that will take into account some pretty dense cold air, and adequately richen the mixture for such a cold stat in such dense air. Aside from that, and the proper antifreeze concentration and a good thermostat that doesn't leak, once she is spinning, it is a short time before the INSIDE of the motor is running in its familiar temperature envelope. Regardless of whether it is -30 or 175, the INSIDE of a car motor stabilizes at a specific range of temps. Maybe ten or fifteen minutes of cold weather warmup and it's all academic. Same thing goes on the high end. Closed cooling system temp is around 205 in modern computer motors. The OUTSIDE temp of the motor is not a significant factor.

Hours? I guess the average car with 100,000 miles has averaged 30 mph or so. That's 3,000 hours. 200,000 miles is like 6,000 hours.

But a car motor only has to put out around 45 horsepower to cruise at highway speeds on level ground.

The same 454 Chevy has been used in boats and cars for years. A pickup truck will usually have no problem getting 150k miles out of a 454.

A houseboat will go around 1500 hours of 2500 rpm cruising with a 454.

A performance boat that is run the way most are, will only give around 800 hours.

It's not hard to see why: The power requirements of a boat are a purely loaded curve. There is no "cruising" where you get to speed and the motor relaxes. This simply does not occur. For a given boat, X rpm = Y power. You can plot a graph, and then whenever you are spining the motor that rpm, you can rest assured tht it is being aked to put out that much power. Every time it is spinning that rate.

Performance boat application is HARD on a motor. It is asked to give a lot of its self in that duty.

Now to tunnel rams.
Straight is good. The less turns the intake charge has to make, the less fuel you "paint" onto the port or runner walls. In a "wet" intake (all carbs, plus TBI) any time you change the direction of the intake charge, the intertia of the fuel causes it to try to travel straight, thus taking out of suspension and slamming it against the outside wall of the intake. Textured surfaces encourage the air to pick the fuel back up, but you are going to have uneven distribution of the fuel in the air once it is slammed out and then pulled back into the stream. Best way to introduce fuel into the airstream is through an atomizer. A carb or injector does exactly that. It sprays tiny droplets into an accelerated stream of air, right into the middle of the stream. That's good. But once it slams out of suspension onto a port wall, it is now a puddle. Forced evaporation, and turbulence induced kinetic action is then required to pull it off the wall.

So straight is better. More fuel efficient for SURE, since you now don't have to overcompensate with extra fuel for the stuff you slam out of suspension and have to waste by adding more to get a decent amount in the final charge.

Port injected motors can make do with weird runner shapes because they have nothing in the air to get slammed out of suspension. The turns DO offer a more restrictive path than straight, but for packaging purposes you can give a little here and gain a lot there for dry intakes.

But there is STILL a good application for port FI with a tunnel ram. Gravity assists a small amount. Don't forget that air and fuel DO WEIGH something. They have mass. The gravity aspect is a minimal one, but it is still real nonetheless.

The long runners tend to focus the intake pulsing of a given cylinder more towards a particular venturi. You can tune for this and usually get an idle quality that is better than the shared plenum of a single plane intake.

You're gonna have some rpm ranges that benefit from the complimentary pulse tuning of the intake, and you are going to have some ranges that do NOT benefit from it. It is a matter of tuning and matching, just like anything else.

Carbs VS EFI?
You can tune EFI on the fly.
You can map EFI for a wide range of atmospheric/elevation deviations.
EFI will always be capable of better cold starts.

But if you run at a given elevation, and tune for a summer weather condition, then you can have great performance with known old school carb technology.

No need to argue about it.
mc
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Old 11-10-2006, 08:16 AM
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Default Re: Tunnel Ram Engines

Quote:
Originally Posted by dmaxx3500
with efi you still ck the same things as a carb,but you need a scanner or a laptop[which most of us allready own] i can most times ck an efi problem as fast or faster then a carb,the scanner just gives you more info faster,which usually helps
HA HA now that's funny. I know 3 people personally that have nothing but problems with their black efi motors and the scans come up clean. It's a complete myth that the scanner makes it an easy fix. One guy is going on 4 years with a crappy running boat after taking it to several merc dealers who all say "the computer thinks everything is fine." I'm with carcrash on this one, give me my Dominators and I'll always get home.

As for cold start, I've never had a cold start issue with my dominators. One pump, turn the key and idle at 1200 for 3 minutes and I'm good to go. Even if it ran like crap for those 3 minutes its just not worth putting up with the EFI issues that I have seen.
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Old 11-10-2006, 01:26 PM
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Default Re: Tunnel Ram Engines

Quote:
Originally Posted by mr_velocity
HA HA now that's funny. I know 3 people personally that have nothing but problems with their black efi motors and the scans come up clean. It's a complete myth that the scanner makes it an easy fix. One guy is going on 4 years with a crappy running boat after taking it to several merc dealers who all say "the computer thinks everything is fine." I'm with carcrash on this one, give me my Dominators and I'll always get home.

As for cold start, I've never had a cold start issue with my dominators. One pump, turn the key and idle at 1200 for 3 minutes and I'm good to go. Even if it ran like crap for those 3 minutes its just not worth putting up with the EFI issues that I have seen.
Agreed.
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Old 11-11-2006, 02:01 PM
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Default Re: Tunnel Ram Engines

Mcolliston;

I am glad your back (although less prolific). Very acerbic wit.

Wouldn't the O2 sensors now available help you tune old tech carbs even better than before?

On a related but different topic, Anyone know the CFM capability of the largest Weber Carbs (I think they are referred to as 48 ID which I assume means 48mm diameter throttle body)??
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Old 11-11-2006, 04:23 PM
  #66
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Default Re: Tunnel Ram Engines

Here is that topic as addressed by Pro Systems followed by a response from Darin Morgin of Reher-Morrison
-------------------------------------------------
Pro Systems
Carburetion Vs. Injection

One of the most oft asked questions is why do carburetors make more power then EFI and why do the car manufacturers use EFI if carburetors make more power?

A few years ago we used some contacts at General Motors to verify some simple facts from some dyno data we had received from a head to head comparison.

An engine was being constructed for Comp Eliminator style racing and the program was going to be electronically fuel injected. Well the system was giving the engine shop some questionable numbers. The shop removed the EFI system and installed some of our Pro Stock carburetors on the EFI manifold top so they could quickly compare systems.

The engine responded immediately with much faster acceleration rates and a 5 percent improvement in power.

The EFI designer was brought out to the site and try as he might he could not out perform those carburetors. When the session wrapped up carburetors were king by 24 horsepower.

I've heard similar stories and similar claims when comparing systems.

So when we analyze this information it really comes down to a simple fact. Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.

EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.

Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.

The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.

Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.

Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see itís not only a perfect machine for atomizing fuel, it also has another advantage. The joule-thompson effect.

Edit:
http://en.wikipedia.org/wiki/Joule-T...29_coefficient

Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.

So when your neighbor with EFI is ingesting 85-degree air, your power plant could be ingesting 65-degree air.

That's a nice advantage.

But let's not skip over the atomization advantage. In a high-end designed carburetor the fuel is emulsed to lift it. Itís a controlled froth. I won't kid you; it's very difficult to control. Itís much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builderís carburetor as they look basically the same? Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.

The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.

Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.

Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.
-----------------------------------------
Darin Morgan

Everyone needs to read that at least two times. Itís all correct and hits the nail on the head! EFI cannot and has not come close to carbs when it comes to making top end power. It will ET slightly better IF everything is correct because it can feed the engine on the gear change with a larger plenum. Induction lag is always a problem and that is the major advantage to EFI in my opinion. Your charge density goes down the tubes with EFI. Every time I raise the injectors as high as possible on the runner or even put them in the plenum, the engine responds with MAJOR power gains. You canít match the atomization of a pre-emulsified booster with EFI.

Land speed guys are stuck on EFI and mechanical fuel injection. Especially mechanical fuel injection. The main reason is that they can lower the profile of the car or stream liner. We built an engine for Earl Wooden. Taking that crap mech fuel injection setup off and installing carbs and switching to racing fuel instead of alcohol was worth 125HP and 40 MPH. He put it in a stream liner and went 377MPH with 525cid. Mechanical fuel injection is the worst thing in the world as far as I am concerned. I have converted a couple more of those guys over to carbs and the results have been anywhere between 25 to 45MPH increase in trap speed!

Hope this helps,
Bob

Last edited by rmbuilder; 11-11-2006 at 05:10 PM.
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Old 11-11-2006, 06:20 PM
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Default Re: Tunnel Ram Engines

MColllinstn writes:"Did somebody say "automotive environment is more hostile than the performance marine environment"? Did somebody REALLY say that?

Did somebody say that the additional hours required of an automotive motor were one of the factors? Did somebody say that underhood temps of -30 degrees to 175 degrees were one of the factors?

Excuse me while I go drive my car to the market and back, never seeing over 2600 rpm, and never seeing more than 80 of its 320 available horsepower.

I guess I will touch on the temperature claims first...
If an automobile engine is started at -30 degrees, then it will obviously be in need of running a winter grade of oil, preferably a synthetic. It will be in need of a fuel control system that will take into account some pretty dense cold air, and adequately richen the mixture for such a cold stat in such dense air. Aside from that, and the proper antifreeze concentration and a good thermostat that doesn't leak, once she is spinning, it is a short time before the INSIDE of the motor is running in its familiar temperature envelope. Regardless of whether it is -30 or 175, the INSIDE of a car motor stabilizes at a specific range of temps. Maybe ten or fifteen minutes of cold weather warmup and it's all academic. Same thing goes on the high end. Closed cooling system temp is around 205 in modern computer motors. The OUTSIDE temp of the motor is not a significant factor.

Hours? I guess the average car with 100,000 miles has averaged 30 mph or so. That's 3,000 hours. 200,000 miles is like 6,000 hours"

My point was the "environment" was tougher on an automotive engine due to the wider range of conditions. The inside of the engine may get to operating temp but the exterior is still at an OUTSIDE ambient temp. The marine environment is tough also, especially in salt water. I know full well marine engines run at sustained higher loads, if your read my post carefully it's there. Do you see Mercury SC 850's lasting 3000 hours? Hell no, only a diesel can last those kind of hours. Yet car engines last a long time because they are designed to even with the ride range of evrionmental conditions they run in. Marine engines are designed differently. You cannot pull a V8 engine out of a stock truck drop it into a boat, it will burn up quickly at sustained high loads.

The point is EFI has come to marine engines, even builders like Sterling and Chief have it available now. You are going to see more EFI. I AM NOT trashing carburaeted engines. They have a place and are very reliable. But some people have their head in the sand to think there aren't more advances to come. When gas is 3-4 $ a gallon again, saving 5 or 10% will make a difference.

Back to Tunnel rams- A really good tunnel ram will produce a cooling effect. Properly designed, if you put your hand on the side of the plenum it will be cold.

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Old 11-12-2006, 02:50 AM
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yes it is
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Old 11-14-2006, 05:13 PM
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Darn good posts!
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Old 11-14-2006, 06:04 PM
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Default Re: Tunnel Ram Engines

There are some working on custom efi tunnel rams placing the injectors over the runners + in /over the plenum. Trying to close the gap in hp between carb/fi - other words trying to use best of both.

Here's a good example of injectors placed above the thottle blades. Okay, way above - this is a stack system (not tunnel ram, but you get the idea)

http://video.google.com/videoplay?do...763&pr=goog-sl
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