Retarding the exhaust cams 24*....

[ryan.hess]

I'm curious if anyone has done it... I did it when I changed my timing belt, but changed it back after it was reving really high (actually turned out I forgot to connect the PCV hose) So I don't know what it idled like... (BTW - 24* = 1 tooth) I'm interested in testing it out again, as a sim on Dyno2000 showed a 40hp gain to peak at 250hp @6500rpm (probably a little high, but still promising) Any ideas? Will it run like shit?

[ryan.hess]

oh, AND: 227lb/ft at 5000rpm!

[grandprix34]

i'd want to try it for the hell of it too if any gains do come out of it.

[Gemmer]

Im not too sure, so understand Im not answering for him, but i believe sappy went to ?18? (I forget) and got too much KR.

[ryan.hess]

That does sound familiar... Why would it cause knock retard though? As I understood it, *advancing* a cam causes higher cylinder temps... Unless I'm thinking ignition timing here.. Wonder if that test was on standard 87 octane (and consequently if 93 octane would fix the problem)

[SappySE107]

I had KR with 17 degrees retarded, and it hurt low end quite a bit. What cam specs are you using that says 40 hp gain at 6500? Even so, low end and mid range will take a major hit and you will be slower than stock overall. Peak numbers aren't worth chasing when the powerband suffers so much. I only show stock at 192 and 24 degrees retarded exhaust being 222, the exact same as the 13* retarded with less power below 6500 all around compared to 13 degrees.

[jmgtp]

I know this has come up before but any ideas on why it was getting the KR? I got mine at ~16* retarded; I havent had a chance to do a freescan run with it to see if its getting any KR though. But I imagine if youre getting it with ported heads I'd be getting a hell of a lot more with stock heads since all the imperfections are still in the combustion chamber. I dont want to go back to 13* because my car seemed to just click at 16* and felt a lot stronger up top to the point that the loss down low seems worth it, but KR worries me. I wonder if it would have knocked running on premium, but paying that much more at the pump wouldnt be worth it,to me at least. I've thought of going even more, maybe 18* but I'm sure there is a limit to when the power up top wouldnt benefit, 16* may be pushing it as is.

[SappySE107]

it wasnt WOT only either...it was prat throttle as well. I couldn't tune the KR out either with backing the spark timing off. I only run 89 octane, since premium hasn't done anything for me. I do have the ported heads but im not sure how yours will be affected either. I timed it back and the car ran a lot better, with no KR as well

[ryan.hess]

What cam specs are you using that says 40 hp gain at 6500?

I'll be honest with you - I have no idea where the numbers came from... I just remember downloading a "3.4 DOHC Dyno2000 file". However, when I change the timing to -15* (all the cams), it still gets the same general 249hp @6500. Maybe you could post an accurate dyno2000 file? (or I could send you the file I have..)

[pocket-rocket]

What cam specs are you using that says 40 hp gain at 6500?

I'll be honest with you - I have no idea where the numbers came from... I just remember downloading a "3.4 DOHC Dyno2000 file". However, when I change the timing to -15* (all the cams), it still gets the same general 249hp @6500. Maybe you could post an accurate dyno2000 file? (or I could send you the file I have..)

He is using the ACTUAL cam specs given to him by a cam company that took them right off of a set of cams he sent to them. The specs in that file aren't quite right.

http://www.60degreev6.com/index.php?p=sections&sid=33

Notice the little note below the cam specs.

[SappySE107]

http://60degreev6.com/download/34DOHCDD2K.zip

[ryan.hess]

That looks better! Thanks! Have you noticed that retarding all the cams 13* results in 242hp@6500 vs just the exhaust's 230hp@6500?

[SappySE107]

look at the low end torque loss and the overall powerband. Idle quality takes a much larger hit with the intake cams retarded with the exhaust retarded. Peak numbers are fine but I was looking for a powerband that was solid vs peaky.