yeah, but anyone can go in and edit Wiki to say whatever they want. it is great for a starting point for real research, and while the information MAY be accurate, it can't be guaranteed.
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Hmm, just joined here from the GA side 'cause I was bored, LOL.mphred said:
About the LY7 (3.6L DOHC)... As much as the pushrod ppl (I'm one of them myself, lol) might like the LZ8/LZ9 (3.9L "3900" OHV), the LY7 is quite a nice engine. I'm really glad/excited GM is offering the LY7 in the G6 and Aura for 2007.
The LY7 reaches it's torque peak at just 3200rpm (251lb*ft). It does kinda spike downwards slightly to 4000rpm but it slowly goes up again as it goes towards 5000rpm. The torque peak is not below 3000rpm but it's actually at a lower RPM than the 3900's torque peak.
The LZ8/LZ9 on the other hand reaches it's torque peak at a [relatively] lofty 4600rpm (240lb*ft). That's 11 less lb*ft and 1400rpm later.
Now you might think the 3900 has more low-end torque in general though, right? Not so.
The LY7 has very similar torque levels as the LZ9. In fact, right from the lowest RPM where torque figures appear on the graphs (looks around 1200 RPM to me), the LY7 is already making just over 200lb*ft of torque. The LZ9 on the other hand is at perhaps only 180lb*ft at that point.At 1500rpm, the LY7 is making perhaps 210lb*ft while the LZ9 is just breaking into the 200lb*ft level. At 2000rpm they are both making what looks like a similar amount of torque (~220lb*ft). The LY7 however continues more rapidly to it's torque peak (gets there at a lower RPM as discussed above) and it has more torque overall.
The LY7 does take longer to get to it's power peak (252hp @ 6300rpm v. 240hp @ 6000rpm) but looks like it has slightly more power at 6000rpm than the LX9 does anyway.
The only thing the LZ9 appears to enjoy over the LY7 is that the torque curve looks smoother. Oh, and of course, the fact that the LZ9 can be mated to a manual transmission whereas the LY7 is automatic only.
Anyway the proof, if you need it is in these graphs below, both SAE J1349 Certified
:3.6L DOHC LY7
http://media.gm.com/us/powertrain/en/product_services/2007/HPT Library/HFV6/2007_36L_LY7_G6.pdf
3.9L "3900" LZ9
http://media.gm.com/us/powertrain/en/product_services/2007/HPT Library/HVV6/2007_39L_LZ9_G6.pdf
[Note there is a difference in the torque scale on the side, so be careful when comparing them, you have to take certain RPM points and compare the torque levels, like I did above.]
I'd agree with you that performance of the cars will be quite similar and probably not worth "worrying" about if you have an 06; but make no mistake the LY7 is no slouch. Compared to the 3900 with 300cc more displacement, it's breaking the no-replacement-for-displacement rule if you ask me
Nice post Mantagreen97!
I do dispute the torque curve a little bit on the 3900 though. I happen to have my own evidence of it.
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Now, you'll notice that the torque peak is just around 3250RPM, but 95% of peak torque is available just above 2500RPM even. I'm sure it's even available sooner, but my Dyno sheet here only shows from 2600+. According to GM when I bought the car, 90% of peak torque is available from 1800RPM all the way to redline.
You'll of course notice that my numbers are lower, as this is WHP, rather than crank HP.
Overall, I'd say that BOTH engines are almost equal in terms of what they put out, with the nod going to the 3.6 (LY7) for having slightly more peak power. The LZ9 does have a smoother torque curve though.
edit: You'll want to look at my second run more than the first. My first run finished too soon due to the 115MPH limit on the car, so 4th gear topped out at like 5100RPM. Second run was done in third.
I do dispute the torque curve a little bit on the 3900 though. I happen to have my own evidence of it.
Now, you'll notice that the torque peak is just around 3250RPM, but 95% of peak torque is available just above 2500RPM even. I'm sure it's even available sooner, but my Dyno sheet here only shows from 2600+. According to GM when I bought the car, 90% of peak torque is available from 1800RPM all the way to redline.
You'll of course notice that my numbers are lower, as this is WHP, rather than crank HP.
Overall, I'd say that BOTH engines are almost equal in terms of what they put out, with the nod going to the 3.6 (LY7) for having slightly more peak power. The LZ9 does have a smoother torque curve though.
edit: You'll want to look at my second run more than the first. My first run finished too soon due to the 115MPH limit on the car, so 4th gear topped out at like 5100RPM. Second run was done in third.
Everything I've read says 2800 for the 2006. I've not dyno'ed mine, but my ass-meter (never get tired of saying that) confirms this
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