Ad Radar
Car Craft
Click here to find out more!

Project Light Speed Part 3 - 49hp LS1 Engine Cam Swap

Got an LS1? Got an itch for more power? A simple cam swap is your answer! GM Performance Parts comes to the plate with their venerable Hot Cam and 49 extra hp for your LS1.

Photography by

Knowledge Is Power
We continue to find out more about the complex factory computer that runs our LS1 engine. In talking further with Steve Cole and also with TPIS' Myron Cottrell, we learned a funny thing happens on the way to wide-open throttle (WOT). The factory computer is designed with what are called short-term fuel trim and long-term fuel trim. Let's say our LS1 engine is running at part-throttle with a short-term fuel trim condition that requires fuel to be added to the base fuel map, and let's say that number represents 5 percent additional fuel.

If the engine goes to WOT at the same instant it adds 5 percent part-throttle fuel, the computer is programmed to add this same 5 percent of additional fuel to the WOT fuel trim. This is done to compensate for a possible weak fuel-delivery situation, a slightly clogged fuel filter, or any other condition that could possibly reduce fuel flow both at part- and full-throttle.

Given this situation, let's say that in an attempt to tune our engine, we reduce the fuel pressure, which is a common approach. Since the lower fuel pressure reduces the amount of fuel delivered, the oxygen sensors at part-throttle will see a leaner air/fuel ratio as well. The computer will compensate and add fuel with the short-term fuel-trim setting, which appears as a negative number if you use a diagnostic-link scanner like the EFI Live system we use. Increasing numbers like -5 or -8 will dictate this same amount of correction when the engine experiences WOT. This is the main reason why our baseline tends to shift over time. In an attempt to have as consistent a baseline as possible, we have resorted to warming up the engine, then shutting it down and disconnecting the battery to clear the computer memory of any "learned" fuel trims. However, if the computer is adding fuel at part-throttle when we hit WOT, then the WOT tuning will go richer by that amount.

One trick you can try is to increase fuel pressure to ensure a positive part-throttle trim number. When the computer generates a positive short-term trim number, it does not reduce the base fuel map for WOT operation. This way, the computer never delivers a leaner base fuel trim than what the engineers programmed in, and there is less of a chance the engine will run lean at WOT and burn a piston.

This explains why our engine will baseline with different power levels: When it rolls into WOT, the short-term fuel trim could be in many different trim modes adding varying amounts of fuel. The more we learn, the better our engine will run, because we can make this engine work for us rather than against us.

TEST NUMBERS
Test 1: New baseline of LS1 with stock cam, stock intake, and 13¼4-inch headers
Test 2: Added GM Performance Parts cam, retained stock 1.7:1 rockers
 
TEST 1
TEST 2
DIFFERENCE
RPM TQ HP TQ HP TQ HP
2,000 323 123 338 128 +13 +5
2,200 330 138 332 139 +2 +1
2,400 336 154 335 153 -1 -1
2,600 341 168 343 170 +2 +2
2,800 344 183 354 189 +10 +6
3,000 349 199 364 208 +15 +9
3,200 354 215 373 228 +19 +13
3,400 360 233 380 246 +20 +13
3,600 367 252 384 263 +17 +11
3,800 375 271 386 279 +11 +8
4,000 382 291 387 295 +5 +4
4,200 389 311 387 310 -2 -1
4,400 394 329 388 325 -6 -4
4,600 396 347 389 341 -7 -6
4,800 396 362 391 357 -5 -5
5,000 393 374 393 374 0 0
5,200 387 384 393 389 +6 +5
5,400 379 389 391 402 +12 +13
5,600 366 391 386 412 +20 +21
5,800 351 387 378 418 +27 +32
6,000 331 379 367 419 +36 +40
6,200 310 367 352 416 +42 +49
AVG 362 285 373 294    
Peak 396 391 393 419    
Lobe Prospecting
Dur. @
Lobe
Camshaft 0.050 Lift (in) Sep.
Stock LS1, Int. 199 0.497 119
Stock LS1, Exh. 208 0.498  
Stock LS6, Int. 204 0.550 117.5
12565308, Exh. 218 0.550  
Stock LS6, Int. 207 0.525 116
12560950, Exh. 217 0.525  
GMPP Hot, Int. 219 0.525  
12480033, Exh. 228 0.525  




With the cam in and the front dress all buttoned back up, the Hot cam and spring change was worth as much as 49 hp at 6,200 rpm, but average power and torque improved as well. This is a good swap.


Parts List
Component Source PN
LS1 crate engine, w/harness GMPP 25534322
LS1 crate engine, no harness GMPP 12568722
Stock LS6 cam, '02-'04 GMPP 12565308
Stock LS6 cam GMPP 12560950
Hot cam kit w/springs GMPP 12480033
Valvesprings, conical GMPP 12565117
Crank bolt, torque-to-yield GMPP 12557840
Pushrods, Hi-Tech Comp Cams 7950-16
SOURCES
Comp Cams Inc.
3406 Democrat Rd.
Memphis
TN  38118
9-01/-795-2400
www.compcams.com
Scoggin-Dickey Parts Center
Lubbock
TX
N/A
www.sdparts.com
GM Performance Parts
www.gmperformanceparts.com
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
0 comments
Car Craft