Torque 101?

To my knowledge bigger displacement increase torque, and higher compression increases HP. You can also play around with the valve or cam timing, with a degree wheel.

 

There is no substitute for boost but if you want a torque increase the natural way, higher compression combined with proper cam selection and exhaust design will give you more grunt, not just compression alone (the gain would be minimal). This is a very expensive upgrade, but installing a 348 engine is another option, mating it to the 328 gearbox. The 355 engine wont fit the gearbox though. Yes, im off topic but these are options for more get up and go.

 

remember HP is a function of TQ so if you increase your HP you're in accuality increasing your TQ. now where on the power band you want it is whole nother discusion.

building engines is alot of math and calcs to make sure your money is spent effectivly for every HP.

 

Here's the very simple, qualitative Physics relation to keep in mind ---

[Torque x RPM = HP]

This is how F1 engines get 900 HP --- not much torque but reving at 19,000 RPM is going to produce substantial HP! Similarly, a diesel semi tractor engine reving at 2000 RPM but with a great deal of torque will generate some HP!

Torque is purely a function of how hard the piston is being pushed, and in turn how much lever it can put on the crankshaft.

These parameters increase the push on the piston --
Higher Compression (to a point, then self-defeating)
Larger Displacement
More Fuel / Air mixture (higher capacity injectors, bigger carbs, turbo, SC, etc.)
Increased Combustion Efficiency
More "explosive" fuel (higher energy content per given specific volume)
Less Friction
Intake / Exhaust Flow

These parameters affect the lever arm on the crankshaft
Stroke
Crankshaft Geometry
Cylinder to Crankshaft Geometry

Now, that is very simplified ---- all these variables interact with one another (the effects of piston stroke are particularly complex), including things such as number of cylinders and firing order / timing to influence overall engine power.

Also, deciding if more HP or more torque is needed is not a straight forward matter --- they each accomplish different results and simply increasing both simultaneously and equally is generally not possible with an internal combustion engine --- they must constantly be traded and optimised at different RPM points throughout the engine's range.

And finally, don't overlook the very important interaction between the engine output and the gearbox --- ratios are selected to optimize final performance at the road wheel (where it counts) --- as gearing is varied, so does final torque, RPM, and HP!

 

umm, you forgot to divide by 5252

 

SCOTT ---

Although I mention 'RPM' and 'HP' specifically, I'm not adhering to any set dimensional convention --- alot of different units out there for angular velocity, torque, and power --- and their associated proportionality constants vary, of course...hence the term 'qualitative relation' and the dimensionless '[ ]' notation, right?

RPM, ft-lbs & HP are most recognizeable to lay people ---

 

I'd add: better spark (or sparks). Dual magnetos in an aircraft generate 30+% more power than single magnetos; coil on plug in a car yielding perhaps 5% more power than 1 coil driving 4 plugs, etc.

For Increased Combustion Efficiency you can vary both the valve timing as well as the ignition timing, too.

 

I've never found all of this to be true on the dyno. spark is spark and as long as you can get it there at the right time, the hp will be the hp.

I have found the pistons with tall domes will tolerate more compresion on pump gas with dual plugs, and therefore make more hp, but on race gas the single plug version does just as well. I've also found that is the voltage of the spark is too low for the cylinder pressure, the timing gets uncontrolable and hp is low. But I have never found any particular ignition system to make more hp than any other. Coil on plug, which is all the rage these days seems to be more about emissions...everything needs to work for 100k miles and spark plug wires are generally bad by about 50k.

 

To all interested in this thread: Go to Amazon, or similar, and buy a used copy of Colin Campbell's long-out-of-print book, "The Sports Car Engine - Its Tuning and Modification" FABULOUS reference.

-rick
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Right. I understand what you are saying, but I have firsthand experience with back to back tests of the same aircraft with single magentos versus dual (had a set burn out on takeoff) and I can assure you that the second set of mags adds substantial power to the engine.

...and you do admit that coil on plug is all of the rage these days...better emissions means better efficiency, I'd think.

 

yes they are three factors, if given any two you can calculate for the third unit. given that time still needs to be accounted for. there is no variance for it since it based upon a time scale.

torque is the unit of force measured, horsepower is the unit derived based on time and RPM is the time unit. however it's like asking which is faster 100miles or 100mph? doesn't add up. when asking about HP vs TQ.

you are right, the gearing is a BIG factor in TQ effeciancy and output. i think alot of people miss that point. a simple chart would show them where best to shift for optimal TQ use in the RPM range.

not to insult anyone, there are alot of lay people here who may get confused on the technical aspects if we drop the specifics for qualitative relations.

no harm, and if i missunderstood you my appologies

 

Torque is what accelerates a car. Horsepower is just an indirect measurement of torque, in that it is a number that reflects how much torque can be provided at a specific RPM. Remember that torque x engine speed = horsepower.

 

The dual spark on an aircraft engine is purely for redundancy. On a before takeoff mag check, a "good running" engine will not lose any RPM (power) switching from one mag to the other, or on "both".

 

Negative. Pre-takeoff mag checks will *always* see a drop of 100 to 200 RPM's in properly functioning systems when switching from "both" to either right or left mags.

 

Technically, ft-lbs is not a unit of Torque, it's a unit of Work. Lb-ft is the unit of torque. Yes, I know, it's a subtle thing and there is even a relationship between the two involving a radian, but it won't matter in engine building.

However, in four cam motors, you can do a lot with cam grinds (P6 and P7), compression (high) and moving of lobe centers to get this all right. That is one (of several) advantages of a 4cam motor over the two cam. A 10mm lift Type 130 (2 cam) camshaft motor is really hard to drive on the the street. Yet, you can take a 10mm lift P7 (SOHC 10mm lift are Type 130 cams, DOHC 10mm lift are P7 cams) cam in a 4cam, move the lobe centers, and it is driveable on the street for the experienced.

I would put in P6 (9.3mm lift) cams, higher compression pistons (keep them under 10.25:1 if you plan to run it on the street), adjust the cam timing to get the right balance of HP to Torque for your needs. If you want to go nuts, you can put in ceramic liners, 14:1 pistons, different electronics, etc., but this would be a track only solution. That is the sort of stuff the cheater motors in vintage racing are doing these days.

Steve

 

Proper funtioning could easily mean an engine with 72/80 leakdown on all four with 200 rpm mag drop on 40 year old spark plugs burning a quart of oil every 4 hours. As long as it can pull static rated rpm and isnt leaking oil profusely its properly functioning. After some 400 plus annuals, many engine changes, teardowns, etc. I could honestly point at a lot of airplanes I never wanted to fly in, which is most of them. But I never seen one of our rentals with a mag drop over 75 rpm. I got to where I didnt trust flyin em, but at least they ran good.

 

Absolutely correct. It is standard on pre-takeoff check to see if rpm drops when single magnet is selected. If it does not, no take off.
Ciao
Eugenio

 

air pumps were eliminated from Ferraris in 1984 replaced with a "pulse" type system.

Dave