[CarsByCarl]

Just finished a dyno session with a stroker combo and got to thinking about how to best put that torque to use in a street application.

One very big advantage that I don't see discussed very often is how a stroker can put the same power to the ground with highway gears as a smaller engine with drag gears.

Stroker engine:
Torque at the flywheel: 700 lb/ft
Axle: 3.00:1
Torque at the wheels: 2100 lb/ft

Average engine:
Torque at the flywheel: 500 lb/ft
Axle: 4.11:1
Torque at the wheels: 2055 lb/ft

Which would you rather drive on the interstate at 70+mph?

 

[crittersf1]

Trick question? Right?

 

[Brad Johnson]

The driveline will have to be built to take the 40% increase in driveline torque. That much added twist between engine and diff is gonna be awfully hard on parts.

Would make for a nice high-speed highway cruiser or a long-haul pulling rig (long distances with few in-town power needs). Plenty of oomph in reserve for hills and traffic changes. A salt flats speedster also comes to mind.

Other than that, well... a high-torque mill running through a long-legged diff is kinda like sending Heidi Klum to a photoshoot in coveralls and a ski mask.

Brad

 

[big-n-bad]

With only the very limited information you have provided it would be a very foolish to assume they are equal. There is a whole lot more to it than the simple presentation you are making.

Weight of car, Cam used, Carb used, Compression, Convertor and the list goes on.

 

[79-6.9]

The driveline will have to be built to take the 40% increase in driveline torque. That much added twist between engine and diff is gonna be awfully hard on parts.

Does it not take the same amount of torque to break loose a set of tires regardless of how much extra you have on hold ?

 

[Brad Johnson]

Does it not take the same amount of torque to break loose a set of tires regardless of how much extra you have on hold ?

Correct. But while torque at the tire is essential the same in Carls proposal, stresses on the two drivelines are dramatically different.

Using the numbers Carl supplied a 3.00 geared diff requires 40% more power through the driveline than a 4.10 to accomplish the same torque as measured at the wheel. Given identical vehicle weights the axles, wheels, and tires will not know the difference, but everything from the crank damper to the differential carrier bearings will be under 40% more stress. More stress equals a need for better components to keep things from going boomn when you lay into the loud pedal.

An analog would be two torque wrenches, one with a three foot handle and one with a two footer. It takes 50% more force on the shorter handle to equal the same lb/ft reading at the bolt. The drive lug and socket at the wrench head may be experiencing the same force but the applied forces at the far end of the grip are not the same.

Brad

 

[Diggindeeper]

Only when your foot is to the floor guys, which happens about what, 5% of the time in a street car.

the stroker will give you the power when you need/want and fuel economy when you dont. Most people dont want to cruise on the freeway at 4000 rpm.

 

[The Pope]

Very interesting comments. Valid points on each side as well. But for the street I'll take the stroker as it fits what I would want in my truck.

 

[bbfhnj]

i pass on the stroker.

460" already makes almost to much torque to hook on a prepped street much less unprepped. i say put that money into a OD unit. and if you want to make BIG street'able power use a power adder. JMO (BTW i know i'm going to get flamed for this)

 

[bob460]

the stroker will give you the power when you need/want and fuel economy when you dont. Most people dont want to cruise on the freeway at 4000 rpm

Very true ive been to car shows 2 hour drive away sitting on the freeway at 3800-4000rpm its not fun, thank god for pearl jam lol!!! (just crank it up). I had a 351 cleveland which ran 11.9 with a 4200 stall and 4.11 gears on pump fuel now upgrading to a 545 which makes 635 hp and 640 tq going to use a 3000 stall and 3.7 gears, will be interesting how it will drive on the freeway and what times it will run, cant wait

 

[Brad Johnson]

Only when your foot is to the floor guys, which happens about what, 5% of the time in a street car.

the stroker will give you the power when you need/want and fuel economy when you dont. Most people dont want to cruise on the freeway at 4000 rpm.

Never said anything to the contrary. Was just trying to point out that legging out the gear would result in higher driveline stresses from the additional FWHP required to maintain the identical RWHP relative to a shorter geared lower FWHP combo.

Brad

 

[2slow]

big cubes vs small cubes . with only taking to specs given . it should be equal.

 

[DaveMcLain]

I had a circle track customer one time who needed a 5.43 gear but didn't have one. So he ended up running the trans in 2nd gear 1.68 ratio and a 3.25 gear in the 9 inch axle and this gave him nearly the same ratio at 5.46. He ran this setup for almost a SEASON on a 1/2 mile track running the engine up to 7200rpm. It didn't seem to hurt anything but what a strain on that little Saganaw 3 speed box. I felt that what it did was spread out the strain of the reduction moving some of it from the rear axle to the tranny, less than ideal but with 400 horsepower certainly workable.

If you think about it you're taking the engine's torque(about 400lbs/ft in this case) and multiplying it by 1.68 before feeding it to the ring and pinion (672lbs/ft) which certainly increases the strain on the driveshaft. I'm not so sure this is a really big deal but if you were making more power and that area was right on the edge it could cause a failure.

 

[tiger]

Good info Carl, thanks for the post.

 

[DaveMcLain]

This thread got me thinking about why OEM transmissions have gone to having a lower rear axle ratio with an overdrive transmission. This always seemed silly to me, why not have a 4 speed automatic yet keep high gear 1:1 and just make low gear lower, wouldn't that be better? It seems like it would be more efficient than what the OEM's are doing BUT their approach seems like it would allow the use of lighter and probably less expensive driveline components yet still have very good reliability.

 

[2slow]

the axles - front or rear drive will see the same power for a overall final ratio. the ring & pinion can see different power . I thinkthere would be a limt to what a automatic trans could have for a low gear and stay as a small unit and be reliable

 

[CarsByCarl]

Driveline stress? Sure. What's the big deal? Get yourself some better u-joints, maybe a stronger driveshaft. Anyone making this kind of power had better be prepared to upgrade the torque converter, trans, driveshaft anyhow. Doesn't matter if it's a 500 ft/lb 460 or a 700 ft/lb stroker.

"just add an overdrive", "just get a five or six speed trans". Ever priced that option? Ever talk to anyone that's seen it through to completion? Far more complex and costly than building more torque with the engine in my opinion.

 

[cwejr]

An analog would be two torque wrenches, one with a three foot handle and one with a two footer. It takes 50% more torque on the shorter handle to equal the same lb/ft reading at the bolt.

Brad

you mis-typed...It takes 50% more force.

cheers, claude

 

[Brad Johnson]

you mis-typed...It takes 50% more force.

cheers, claude

Yeah, my bad. Trying to type and talk on the phone at the same time. Corrected. Thanks for the heads up.

"just add an overdrive", "just get a five or six speed trans". Ever priced that option? Ever talk to anyone that's seen it through to completion? Far more complex and costly than building more torque with the engine in my opinion.

Yep. All goes back to "Build the engine for the vehicle or the vehicle for the engine." Nice thought experiment, though. Makes you think and consider lots of different options.

Brad

 

[2slow]

Driveline stress? Sure. What's the big deal? Get yourself some better u-joints, maybe a stronger driveshaft. Anyone making this kind of power had better be prepared to upgrade the torque converter, trans, driveshaft anyhow. Doesn't matter if it's a 500 ft/lb 460 or a 700 ft/lb stroker.

"just add an overdrive", "just get a five or six speed trans". Ever priced that option? Ever talk to anyone that's seen it through to completion? Far more complex and costly than building more torque with the engine in my opinion.

transmissions cost under $2000 for a 5 speed , ring and pinion $175 . looks like a lower cost to me . no machine work required