More torque more compression

[Silvermado]

I can’t find much on this but I’d like my truck to have more torque, I think it’d just be more badass and I tow close to capacity Not so much horsepower, I’m not trying to race , anyways from what I understand diesels have high compression which equals torque, so say I ported the intake on my heads and kept my stock exhaust manifolds, made my exhaust something like a dual H pipe, would that create more compressionand back pressure and in turn would that create more torque.  And 2 if possible, if it was too much compression could the engine take it and would I be able to replace valves and springs with heavier duty stuff in my heads if it was too much

2010 Silverado 1500 5.3 lc9 

[CamGTP]

No, none of that would increase compression. Back pressure stuff is a myth, you don't want or need back pressure. These trucks with properly working exhaust even with cats will make like ~1 psi of back pressure.

 

You have to change compression by changing the cylinder heads themselves, milling the heads to increase compression or putting in different pistons to increase compression.

 

 

If you want more horsepower and torque get rid of that stock camshaft and the AFM/DoD system. You need more airflow to get more power and that stock camshaft is small. Most mild camshafts with a good tune will gain an easy 35-40 horsepower and torque over stock.

[Silvermado]

5 minutes ago, CamGTP said:

No, none of that would increase compression. Back pressure stuff is a myth, you don't want or need back pressure. These trucks with properly working exhaust even with cats will make like ~1 psi of back pressure.

 

You have to change compression by changing the cylinder heads themselves, milling the heads to increase compression or putting in different pistons to increase compression.

 

 

If you want more horsepower and torque get rid of that stock camshaft and the AFM/DoD system. You need more airflow to get more power and that stock camshaft is small. Most mild camshafts with a good tune will gain an easy 35-40 horsepower and torque over stock.

Ok thank you but now on the case of cams, I’ve also heard going to big kills low end torque is this true

[CamGTP]

Yes, large camshafts move the powerband up.

 

Smaller camshafts keep it near stock. These engines make peak torque in something like the 3,500-4,500rpm range. A mild camshaft upgrade will still keep it there. Most will only increase the overall redline by about 500rpm too. The stock camshaft isn't making much power past 5,400-5,500rpm and a mild camshaft would let it breath out to 6,000rpm.

 

Most places call them stage 1 or stage 2 camshafts. They work with stock stall torque converters. Usually the sizes are 206/212ish or 212/218 at .050 lift when going by the quick spec sheet.

[Silvermado]

6 minutes ago, CamGTP said:

Yes, large camshafts move the powerband up.

 

Smaller camshafts keep it near stock. These engines make peak torque in something like the 3,500-4,500rpm range. A mild camshaft upgrade will still keep it there. Most will only increase the overall redline by about 500rpm too. The stock camshaft isn't making much power past 5,400-5,500rpm and a mild camshaft would let it breath out to 6,000rpm.

 

Most places call them stage 1 or stage 2 camshafts. They work with stock stall torque converters. Usually the sizes are 206/212ish or 212/218 at .050 lift when going by the quick spec sheet.

Yeah that’s what I’m seeing on Texas speed 212-218 and 216/220 would the 216/220 be to big where’d I’d have to start upgrading more parts?

[CamGTP]

Stick with the 212/218 or smaller.

[Grumpy Bear]

Torque = (BMEP X swept volume in cm3) / 2,473. The Gen V 5.3 L-83 has 383 pounds feet at 4,100 rpm. 

 

BMEP then is (383 * 2,473) / 5300 = 179 psi

 

HP @ Peak Torque = (179 * (5.3 x 4,100))/13,000 = 299 hp @ 4,100 rpm

 

To get more 'torque' at the same rpm you need more horsepower at that rpm which means you need a higher "mean effective pressure" or "increased thermal efficiency" or a "change of fuels". E-85 for instance. That will net you 416 pound feet at the same rpm. 33 pounds feet or 9%. 

 

To get a higher mean effective pressure you have two choices. 

 

1.) More static compression ratio.

 

The L83 has a compression ratio of 11.0:1. Multiply that times atmospheric pressure and you get 162 psi and as the BMEP is 179 the VE at this rpm is already over 100% and the BMEP at the limits of the base specified fuel. 

 

 

 

2.) Forced induction. 

 

You can get bigger peak torque at a higher rpm with cams etc. like you've been discussing but to make it useful you have to spin the motor harder for the same road speed meaning a gearing change. 

 

This all has a cost and more than the money you will lay out in parts and labor. It will cost more to operate and it will have a shorter lifespan.

 

In the 60's with power to displacement ratios were .75 hp/cid or less and fuel octane at the pump could be as high as 102, (Leaded SUNOCO 260) things like this were easy. Today your starting with an OEM design that is starting were hot street motors of past era's ended. 1.2 hp/cid and on fuels of 93, almost 10 points lower.