Guys

Just wondering if any technically minded members out there may know what you have to do to an engine to make it produce more torque rather than more power?

For example, the new W427 7ltr Commodores produce something like 375kw of power and about 630nm of torque. On the other hand, I read a V8 supercar produces approx 450kw but 'only' 610nm. Now I understand the supercar may not have the same motor (ie not a 7ltr) as the W427 but regardless, what do engine builders do to give an engine more power but no neccessarily a proportionate amount of more torque?

Pete

I suppose different modifications will affect power and torque, and where the power and torque curves peak in the rev range, I prefer the torque rating as a better indication of performance in everyday situations, as most power ratings are at or near redline, which is not where you will be in everyday driving (well most of us!!) . a broad torque spread will be alot better than a narrow, peaky torque spread (In my opinion).

Stroke and reciprocating mass has alot to do with torque.

EDIT: AND cubes

to expand on that, its the bore x stroke ratio that determines whether an engine favours power, torque, or has a good amount of both.
a long stroke engine, undersquare, ie stroke greater than bore, will produce high torque compared to power
a wide bore engine, oversquare, has a bore greater than the stroke, produces higher power and less torque
then theres equal bore and stroke, square bore.

That would explain why the 3.0 is revvier and a bit more fun than the 3.5

Power of the engine is torque x RPM so it's about the torque curve and how hard it will rev.

When in doubt wiki

Machine torque

Torque is part of the basic specification of an engine: the power output of an engine is expressed as its torque multiplied by its rotational speed of the axis. Internal-combustion engines produce useful torque only over a limited range of rotational speeds (typically from around 1,000–6,000 rpm for a small car). The varying torque output over that range can be measured with a dynamometer, and shown as a torque curve. The peak of that torque curve occurs somewhat below the overall power peak. The torque peak cannot, by definition, appear at higher rpm than the power peak.

Understanding the relationship between torque, power and engine speed is vital in automotive engineering, concerned as it is with transmitting power from the engine through the drive train to the wheels. Power is a function of torque and engine speed. The gearing of the drive train must be chosen appropriately to make the most of the motor's torque characteristics. Power at the drive wheels is equal to engine power less mechanical losses regardless of any gearing between the engine and drive wheels.

Steam engines and electric motors tend to produce maximum torque close to zero rpm, with the torque diminishing as rotational speed rises (due to increasing friction and other constraints). Reciprocating steam engines can start heavy loads from zero RPM without a clutch.
[edit]

After all that my educated guess is that changing the gearing ratios would change the charateristics of torque. My reasoning being the low gear ratios of trucks and other heavy vehicles. Though I have no idea about rotary engines maybe that's why you have to keep them redlined all the time.

trucks have a usable torque band of about 1000 rpm. hence why they can have 18 gears to get em upto speed.
gears just multiply the torque, doesnt change it.

Hmmm....so trucks and vans use their gearing to make the most of the torque characteristics of the engine. But doesn't actually change torque.
So to actually increase torque you need to

There are two ways of increasing the amount of torque generated by an engine - either increase the capacity (or, more correctly, capacity times volumetric efficiency), or increase the length of the lever arm (or stroke).

http://autospeed.com/cms/title_Power-versus-Torque-Part-1/A_108647/article.html

Hmmm....so trucks and vans use their gearing to make the most of the torque characteristics of the engine. But doesn't actually change torque.
So to actually increase torque you need to

There are two ways of increasing the amount of torque generated by an engine - either increase the capacity (or, more correctly, capacity times volumetric efficiency), or increase the length of the lever arm (or stroke).

http://autospeed.com/cms/title_Power-versus-Torque-Part-1/A_108647/article.html

Are you refering to a 3rd gen?

If so, steve knight can tune your ecu to give more spark/torque down low if you want.
Very effective.

Advance the cams, and eliminate the different timing between the front and rear banks.
Get a Steve Knight ECU tune. Get this done after headers and a 2.5" metal cat change. If you don't have a sports rear muffler then change to this as well.

With the cam timing change you will gain lots of low down power, could be in the region of + 10% for a small drop at the top end.
Do a search on cam advance to see some comparative power curves that were posted last year.
Gerry

The initial discussion here seemed to be what produces torque, but Spud & FamilyWagon are touching on how to increase torque from your current engine.
I'll add to this later direction:

Mods like intake and exhaust generally have the intention of removing restrictions and thus provide an overall torque AND power increase. They don't always work on all cars - eg: apparently the exhaust manifold on the Magna is pretty good, so extractors might not make much difference, but the rear muffler is restrictive and a free flowing replacement will improve power.

However, these same items can be "tuned" to provide more benefit towards low down torque or top end power. The tuning requires either extensive scientific measurement & theory, or trial and error. It's like finding a harmonic frequency. The right length and diameter intake or exhaust pipe can improve power at a specific RPM. Generally it can reduce power at another RPM too, so there's frequently a trade-off somewhere.


Normally replacing stock exhaust headers with extractors provide a torque & power benefit but depending on the design, the gain could be at high rpm for power or lower rpm for torque.
On a 4 cyl engine, a "4 into 1" extractor is designed to improve high RPM power, meawhile a 4-2-1 design can provide more torque particularly with long secondary pipes (the 2-1 stage).
I'm not very familiar with 6 cyl engines, but I think the old school V6 boys would have a "Tri Y" design that might be the equivalent and this might be relevant to the Magna, although from memory all of the Magna extractors I've seen are 6-2-1, not 6-4-2-1.

Cheers!
Graham.

how the f$$k are you ment to make 6 pipes go into 4, then 2, then 1??

Pacemakers are IMHO the best bolt on design for torque.. there 1.5" mandril primaries, and 2.25" secondaries, (i havn't seen the RPW ones upclose)

BUT that doesn't mean they can't be improved upon.. the lengths were wored out to cam duration/lift, and compression ratio.. and honestly pacemaker had them pretty close to what we call a good 'street' design.. so we didn't feel the need to make a full set of customs..

all we did was make the 3-1 collectors a bit neater (the a die grinder, and we had to make some new sections cos they were crushed), and the 2-1 fabricated a 2.25" 15 degree tapered merge collector, expanding to 2.5".. the taper isn't very long, but for a street car that is all that is needed, it was worked out using the 'burns formulae'..

http://www.freeimagehosting.net/uploads/c456e5fc7a.jpg
http://www.freeimagehosting.net/uploads/9b765126d1.jpg
http://www.freeimagehosting.net/uploads/a66b225817.jpg
http://www.freeimagehosting.net/uploads/217021836e.jpg

Guys

Just wondering if any technically minded members out there may know what you have to do to an engine to make it produce more torque rather than more power?

For example, the new W427 7ltr Commodores produce something like 375kw of power and about 630nm of torque. On the other hand, I read a V8 supercar produces approx 450kw but 'only' 610nm. Now I understand the supercar may not have the same motor (ie not a 7ltr) as the W427 but regardless, what do engine builders do to give an engine more power but no neccessarily a proportionate amount of more torque?

Pete

They used to say that "Horsepower sells cars, torque wins races" and intuitively that used to make sense to me. Having high torque in the low-to-mid rpm range is what will accelerate you quickly if you're in the right gear. Torque after all means a turning force and that is precisely what the engine produces in the first instance. Power is a more abstract concept (defined as how much energy is being produced or consumed per second) and is derived from torque x rpm. Ergo, if your engine's torque curve is such that it peaks at higher rpm, your engine has higher max power (diesels usually have their peak torque at around 2000rpm and that's why their max power is often low compared to an equivalent petrol engine).

According to this analysis however, its not torque but high average power that wins races - http://craig.backfire.ca/pages/autos/horsepower (very readable).

So, the answer to your original question "what do engine builders do to give an engine more power but no neccessarily a proportionate amount of more torque?", lies in changing the torque characteristics of the engine such that its peak torque is produced at a higher rpm.

make the engine breath better at lower rpm = more torque.

how the f$$k are you ment to make 6 pipes go into 4, then 2, then 1??

Pacemakers are IMHO the best bolt on design for torque.. there 1.5" mandril primaries, and 2.25" secondaries, (i havn't seen the RPW ones upclose)

I couldn't view the images you linked to, unfortunately.

I imagined a tri-Y header as a 3 to 2 to 1 on each bank of the V6, but after doing a very quick search, found this page: http://www.pacemaker.com.au/faq.html#design
Tri-Y is in fact a 4-2-1 extractor - just I've never heard that around 4 cylinder engines, only bigger cars, and in that link, they're discussing it with V8 engines.


I imagined Tri-Y in a V6 as an unequal manifold, where 2 cylinders would join together, and the 3rd join in a little later.

4-2-1:
YY
Y

3-2-1
Y|
Y

:)

sorry, fixed the links

merge collectors and proper tuned length pipes WILL increase torque... only problem is that custom made pipes are very labour intensive...

i have added a few more pics of some of Extreme Custom Engineering's custom extractors, Craig will do custom tuned length extractors on anything.. the quality speaks for itself..

these are a set of 6-2-1's on a 3.8L (stroked) BMW straight 6... the lengths required involved some interesting bends..

http://www.freeimagehosting.net/uploads/671fbe374a.jpg

this is a set of 4-1's on a drag car that go up and over aka fenderwalls

http://www.freeimagehosting.net/uploads/945af3a20b.jpg
http://www.freeimagehosting.net/uploads/aa008ac21f.jpg
http://www.freeimagehosting.net/uploads/5d0c0a6fcf.jpg

the merge collector is critical in these designs... helps torque immensley...

very interesting article... this is what im leaning towards doing
http://autospeed.com.au/cms/A_111106/article.html