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Ballparking power gains

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04gtpnoob

New member
04 gtp. SD headers with dp and high flow cat to 3" custom welded cat back with new res (same length as stock), 3.4 pulley, colder plugs, 180 tstat, 3" HAI, hp tuned timing to 14 to eliminate all and any knock, richened afr slightly, raised rpm limit about 250. What kind of hp and torque gains would I see vs stock? I know all instances are different, but a range could be helpful, I want to see if I'm getting what I can out of the mods. I'm guessing 20-30 hp gain? Torque I'm not too sure. And how would this equate to 1/8 mile, 1/4 mile, and 0-100 times? I just want something to compare to before I go to the track myself. Thanks in advance for the help :th_jester:
 


Id be interested to hear also. we have similar builds. I have 1.8 Roller rockers and a beefed up Transmission and some other stuff. Once I get my next rounds of mods done I want to take it to a dyno just for ****s and giggles. I care more about street performance than anything.
 
3.4" with headers...

14* of timing.

Piggy AFR.

But to answer your question you probably didn't gain much horsepower at all...you might have gained 10-15 WTQ, but you lose it all because of the AFR, timing, and knock. So it's probably just as fast as a stock car.
 
How rich?

I got away with 14º of timing on 11.0 AFR with no knock. Better than the stock 10.7 AFR with 3-5º of knock on stock pulley with factory manifolds. 20-25hp gain is my guess and that's just a guess. So many factors can into play and every engine is slightly different.
 
his afr aint piggy, its maf tuned, 14 is all it would take with a 3.4 and gen 5.

theres no other mods, just headers & 3.4. 3.6 would be better im sure.
 


If 14* is all it would take, with less than stock AFR, then it needs a larger pulley.

Like I said, I'm sure it's no faster than a stock car.
 
But what if it isn't richer than stock AFR??

Because going richer than 10.5 to 10.8 would be wasted power.

Charts for reference on a stock GTP file.

gtp%20fuel_zpsta7vtoex.png
 
blueguy said:
If 14* is all it would take, with less than stock AFR, then it needs a larger pulley.

Like I said, I'm sure it's no faster than a stock car.
Click to expand...

I don't understand your logic here. I've driven stock GTP and GTP with mods like his and mine, and ours is way faster than stock.
 
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More timing and less boost is going to give you more power than less timing and more boost.

20-22* is "standard" from the tunes I've seen.

Don't chase the KR monster away on 04+. About 2* KR is normal. Something about a change in sensors from what I recall.
 


SgtMarshal said:
I don't understand why you are responding to that question.
Click to expand...

Because it's an easy question to answer. I'm sure at least 51% of the forum could answer it correctly, and that's saying a lot.

Let's take a quick look at rickisrad's setup:
2004 Comp G. Pacesetter headers, 1.8 roller rockers, Wizair CAI, Overkill'd, 3.4 pulley, ZZP transmission, fuel pump and alt rewire, poly mounts/performance suspension, Impala front brakes drilled and slotted rotors. blah blah blah

If you think that should be the same feel or quickness as a stock GTP, I don't know what to tell you.

Maybe everybody who has been putting money into modding has been throwing their money away (more than we know)...
 
i had that same set up but 1.95 rockers on a gen 3 blower. the 3.4 wakes it up. it cant be more then 20 hp tho. going from stock to lightly modded and no kr also wakes the car up a lot.

gen 5 is a better blower so a 3.4 is really to much with out rockers or a cam to help it flow better, why his timing is dropped.
 
That's why he should pulley up. 3.6 would be better suited for his current mod list.

A 3.6 on a Gen V is roughly equivelant to a 3.4 on a Gen 3.
 
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