Bolt On H.P.

[Tomtall]

A while back there was a discussion about bolt on horsepower. Nitrous Oxide kits, Turbo Kits, Big carb manifolds etc.

A few examples of this were the use of nitrous on the world record setting OMC V-8 outboard driven by Bob Wartinger. This engine was rigged with nitrous to give the engine an added boost just before entering the traps. 15 seconds of boost is all they gave the motor. But it seemed to be enough.

Land & Sea had their Turbo powered outboard record setter also.

Who on BRF has played with such things and what was your outcome?

[kevin beaulier]

I'm 98% sure the hydro in the ad was built by Tom Drozd in Dallas. Thats a really cool picture. Thanks for posting it.

[Skoontz]

Educate me here. In the olden days, when motors were motors and gas was mixed with oil as how it should be, turbo and supercharging was tried and it shoved the gas through the engine so fast that much of the combustable charge was pushed right through to the exhaust.

How are they making compressed induction systems work in this day and age? Unless a valve was used to hold in the charge, I'm having a brain fart here and can't visualize how this would work/benefit....

[Roy Hodges]

so let's say that a V-6 merc uses 40 gallons /hour ? ok ? (for an example) . o k. Now ,let's say that supercharged /turbocharged - it uses 3 times that much? That's 120 gallons/hour . for DRAG racing, who cares? That would be 2 gallons /minute. divided by 6=10 seconds . 8quarts/6=1 &1/3 QUARTS !that's affordable for just about anybody ,and you would not need a big fuel tank, for the drags , anyway .

[7500Blizzard]

There's tonnes of guys running Nitrous nowadays in drags and pleasurecraft. There's been a guy working on a twin turbo merc for a few years haven't heard much lately, this motor is from New Zealand

[Mark75H]

Educate me here. In the olden days, when motors were motors and gas was mixed with oil as how it should be, turbo and supercharging was tried and it shoved the gas through the engine so fast that much of the combustable charge was pushed right through to the exhaust.

How are they making compressed induction systems work in this day and age? Unless a valve was used to hold in the charge, I'm having a brain fart here and can't visualize how this would work/benefit....

You are correct, a normal belt, gear or shaft driven supercharger just looses pressure out the exhaust ports because they close last ... but ... a turbocharger causes a restriction that stops the pressure from falling to atmospheric pressure. One way of thinking of it is that the piston motor is now functioning completely inside the high pressure part of a jet engine; another way to think if it would be that the piston motor is now operating at the bottom of a great hole and the atmospheric pressure is much higher than sea level - the exact opposite of running your motor on a lake near Denver or Mexico City where you loose power at altitude due to reduced atmospheric pressure.

Supercharging a normal piston port spark ignition two stroke engine does not work ... unless it is turbosupercharging

[MN1]

You are correct, a normal belt, gear or shaft driven supercharger just looses pressure out the exhaust ports because they close last ... but ... a turbocharger causes a restriction that stops the pressure from falling to atmospheric pressure. One way of thinking of it is that the piston motor is now functioning completely inside the high pressure part of a jet engine; another way to think if it would be that the piston motor is now operating at the bottom of a great hole and the atmospheric pressure is much higher than sea level - the exact opposite of running your motor on a lake near Denver or Mexico City where you loose power at altitude due to reduced atmospheric pressure.

Supercharging a normal piston port spark ignition two stroke engine does not work ... unless it is turbosupercharging

Some how this doesn't sound right. Both produce pressure, how can one produce a different type of pressure that stays in the cylinders and the other doesn't?
Mark N

[Mark75H]

Some how this doesn't sound right. Both produce pressure, how can one produce a different type of pressure that stays in the cylinders and the other doesn't? Mark N

Both push in, but only a turbo has something hanging around outside the exhaust port. Its not that the pressure is different, its that a motor is basically inside it's turbo - and the whole inside system is at higher pressure

[mac19f]

In a 4 stroke engine supercharging or turbocharging results in a higher initial pressure inside the cylinder on the intake stroke before the compression stroke. That is its main contribution to increased power.

On a 2 stroke there are different factors at work. Other than on direct injected 2 strokes there is always mixing of the fresh intake charge with the spent exhaust gases. Normally the final charge in the cylinder during the compresion stroke has a significant amount of exhaust gases included. This is because the amount of fresh charge pumped from the crankcase into the cylinder is slightly less than the volume of the cylinder. This "dirty" charge results in less power per stroke than a 4 stoke engine would produce. That is a lower "break-mean-effective-pressure"(BMEP). Direct injected engines over scavenge the cylinder with clean air and then inject the fuel into the cylinder. The resulting clean charge is why they have significantly better performance than traditional 2 strokes.

Now if you don't care about fuel economy or emissions you can overscavenge the cylinder with a fuel/air charge with a supercharger, wasting a lot of it out the exhaust. But "BMEP" will be increased with a net increase in horsepower.

[Mark75H]

you can overscavenge the cylinder with a fuel/air charge with a supercharger, wasting a lot of it out the exhaust. But "BMEP" will be increased with a net increase in horsepower.

BMEP will be increased some because volumetric cylinder effiency will be increased to 100%, but the net power cost to do this (because of the loss driving the pump) will not be much above break even or will be a net loss. In other words, power will be increased at the piston, but not necessarily at the output end of the crankshaft

Complete cylinder scavenging is not always 100% desireable .... in some situations residual (or reintroduced exhaust) gas is helpful in reducing detonation and increasing power ... on a 4 stroke it is called exhaust gas recirculation or EGR. It was new to production cars in the 1970's but researchers had been using it on test motors for decades before we ever heard of it.