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Anyone have RWHP numbers

linda

By linda
in 2000-2014 Silverado HD & Sierra HD

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linda Enthusiast

linda

Posted
Posted

Chevy rates its 2003 8.1L (RPO L18) @340hp/455lb/ft torque. Im assuming thats at the crank. Anyone have RWHP numbers for the 8.1L? Trying to find out what my actual RWHP will be after the westers tune gets installed. Lyndon told me to expect a 52-54 RWHP gain and a 76-80 lb/ft of RW torque gained. Just trying to convert that to total numbers at the rear wheels. Thanks

o4yukonxl Enthusiast

o4yukonxl

Posted
Posted

Your stock RWHP numbers have a lot of variables. First, the type of drivetrain you have. The Allison is supposed to be less effecient than the 4L80 and so your RWHP will be less than a Suburban. Also, 4wd vs 2WD, then add in altitude, barometric pressure, humidity, temp, etc. and you get the idea. Best way is to find a dyno and test your change same day, and close to the same time. Everyone's RWHP will be different.

linda Enthusiast

linda

Posted
  • Author
Posted
Your stock RWHP numbers have a lot of variables. First, the type of drivetrain you have. The Allison is supposed to be less effecient than the 4L80 and so your RWHP will be less than a Suburban. Also, 4wd vs 2WD, then add in altitude, barometric pressure, humidity, temp, etc. and you get the idea. Best way is to find a dyno and test your change same day, and close to the same time. Everyone's RWHP will be different.

 

okay.....

8.1L/Alli combo

4x4

0' - 500' max altitude where i live

4.10 rear

average winter temp 30- 40 degrees, 30-50% humidity

average summer temp 80-90 degrees, 70-80% humidity

 

................but i was just looking for an average number. Thanks for the help "o4yukonxl".

tmf6902 Senior Enthusiast

tmf6902

Posted
Posted

Doesn't the allison rob you of something like 23%?? 28% of the HP?? for some reason I thought it was around 240-270 at the rear wheels....that's a total guess of something I think I remember reading though. I really have no idea

linda Enthusiast

linda

Posted
  • Author
Posted
Doesn't the allison rob you of something like 23%?? 28% of the HP?? for some reason I thought it was around 240-270 at the rear wheels....that's a total guess of something I think I remember reading though. I really have no idea

 

Is this because of Torque management? Or is it just the auto robbing us?

SOM Truck Enthusiast

SOM Truck

Posted
Posted
Your stock RWHP numbers have a lot of variables. then add in altitude, barometric pressure, humidity, temp, etc. and you get the idea. Best way is to find a dyno and test your change same day, and close to the same time. Everyone's RWHP will be different.

This is why we have SAE correction factors actually... to normalize our power curves for comparisons. For example my TA will generate over 450 rwhp NA in cool weather with low humidity, but the correction factors will normalize it back to around 405 rwhp SAE.

 

Your drivetrain comments are valid although not the 4x4 / 4x2 comment... unless you intend to dyno in 4x4 high on a all-wheel dyno.

8100HD Enthusiast

8100HD

Posted
Posted

Allison=36% loss. :shakehead: Which should put you in the area of 255-260 rwhp and 330-335 rwtq stock. Again this is just a ballpark and will vary from dyno to dyno, day to day. Just FYI my truck dyno'ed 300 rwhp/440 rwtq on average, and thats spinning the rollers with 35's. My plans call for a 100hp boost this spring. :nono:

tmf6902 Senior Enthusiast

tmf6902

Posted
Posted
Allison=36% loss. :shakehead: Which should put you in the area of 255-260 rwhp and 330-335 rwtq stock. Again this is just a ballpark and will vary from dyno to dyno, day to day. Just FYI my truck dyno'ed 300 rwhp/440 rwtq on average, and thats spinning the rollers with 35's. My plans call for a 100hp boost this spring. :nono:

Out of curiosity...what are the specs on your truck besides 8.1 and 3.73's.....What does "Loaded" mean??? :D

linda Enthusiast

linda

Posted
  • Author
Posted
Allison=36% loss.  Which should put you in the area of 255-260 rwhp and 330-335 rwtq stock. Again this is just a ballpark and will vary from dyno to dyno, day to day. Just FYI my truck dyno'ed 300 rwhp/440 rwtq on average, and thats spinning the rollers with 35's. My plans call for a 100hp boost this spring.

 

im confused, If allison = 36% loss....then how did you dyno at 300/440? You have the same setup as me except i have the ext. cab not crew cab, and i have a 4.10 rear.

8100HD Enthusiast

8100HD

Posted
Posted

TOG headers/DirectHits ignition/Flowmaster 50 cat-back/UPD (NSV) intake/ de-screened mafs/Superchips custom tune/3.73 rear

 

"LOADED" means way too much to list. here's a couple pics.

374975_20_full.jpg

 

374975_15_full.jpg

 

374975_13_full.jpg

linda Enthusiast

linda

Posted
  • Author
Posted

okay, that makes sense now. Thats a tough looking ride you got there. Looks like you have upwards of about $150 - $175 invested in that rig... :shakehead:

boomer 33 Enthusiast

boomer 33

Posted
Posted

Got my Westers done last week, I only have SOTP to go by, but doubt that the gains were that much. Don't get me wrong, but that would be a large increase. Would do it again though. I know a couple of guys with the same set up except they have 3:73, trying to talk them into lining them up but so far their ego is manifesting itself in "gee I don't know if I should " ways. I will wear them down though.

I'll let you know when I get one of them to play. :shakehead:

boomer 33 Enthusiast

boomer 33

Posted
Posted

I don't know, it does run really good, and just to test the limiter, I just exceeded what the top speed USED to be by a GOOD margin, and it did it without effort. I can also get a little first gear scratch now and it would not before. Anyone know how many miles it takes to break in an engine to where it really gets to the "sweet spot"? I have about 7000 on mine now.

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