VQ loses power as rpm's rise?
 

Someone said this on a forum I frequent. I've never heard this before, ever. I have heard the VQ can be soft under 3500, I know it's gas thirsty, I know it's not the most efficient engine, but I've never heard anyone even infer that it doesn't have a really flat torque curve or loses power at high rpms.

Any insight?

Our engines don't have a very flat torque curve. The torque rises up to about 5500 rpm and then starts to fall off. Does the engine "lose power" at higher RPM? No, it loses (some) torque. Power probably peaks within a couple hundred RPM of redline. Find a dyno graph, it tells the whole story.

http://66.228.67.107/images/g35/dyno/dynorun.jpg

Every dyno I've seen has been very flat to 6400. I understand what the guy means if he is saying VQ's don't normally have a redline of 9,000 rpm, but I've never heard it faulted for losing power near the redline.

If that's a true dyno graph then they've seriously retuned the 05 engines in a way that I was not aware of. That motor loses neither hp nor torque at high rpms.

FYI, all VQs have always had a very flat torque curve until about 6300~ rpms then it starts to drop. I mean ALL since the day of the 1995 Maxima.

I can post my 04 Dyno tonight if needed.

Dudefish - I'm not disagreeing with you, I've just never seen a dyno that indicated a drop-off at 5500 rpm. We used to own a '96 Maxima and it was almost exactly the same as above, +/- 3 or so all the way from 2400-6600. Just weird I guess, until the poster on that other forum mentioned a power decline at high rpms I'd never heard anything of the sort before. Perhaps he was talking about HP, or was referring to cars that redline at 8-9k.

So one anonymous guy somewhere on a board said something about the VQ and you took it as gospel ... good lesson not to believe everything you read or hear

Heh. Stop and think about what you're saying for a second.

If I took it as gospel I wouldn't be asking, would I? Unlike most of the troll-like whack jobs that frequent internet forums, when someone says something I haven't heard, or disagree with, I don't just call them a down-syndrome kid then run away giggling to my mom. I check it out and make sure I'm right before I let them know that they're wrong. Interesting concept, isn't it?

I will post my 05 Dyno when I scan it tonight. Keep an eye out for it. I had it dynoed today, and its the highest 05 I have seen dyno yet! I am happy that I must have a rare one! But back on topic, the TQ curve is straight across.

Had my 05 Dynoed today for other reasons I can not say at this moment. I needed a baseline. The car is stock except for a ztube. The car is exceptionally powerful. Even more powerful than my 04 G35 6mt.

Basically the dyno speaks for itself. Take a look.

FYI:

Stock DYNO for 2005 G35 Sedan 6mt with 7351 Miles, outside temp 60 degrees, shop temp 75~ degrees. Car could not go above 6800 rpms due to speed limiter at 145 mph kicking in.

Car was dynoed in 5th gear for 1:1 ratio.

http://www.sah2o.com/russ/g35/05g35dyno1.jpg

One above shows rpms, one below shows speed.

http://www.sah2o.com/russ/g35/05g35dyno2.jpg

http://www.sah2o.com/russ/g35/dynotune1.jpg

http://www.sah2o.com/russ/g35/dynotune2.jpg

259/236... I hate you! Really though, that's awesome. And thanks for the dyno's. I'm pretty certain at this point that that guy was just talking out his ***.

On my last dyno TQ nose dived from 250 at 5000rmp to 225 around 6300rmp... HP climed all the way through rmp range to 271 at 6500 (and was still going up - would have been higher if continued past 6500).

I am trying to find something to help my TQ (maybe converter some day).

Those are good numbers but they would be a bit lower if SAE corrected, which is standard. Your numbers are STD corrected which makes them higher than they should be. Despite that fact, your engine is still abnormally strong. Congrats...

STD numbers are worthless for comparison purposes. Have the shop give you the dyno files. You can then download the Dynojet software off their web site (free) and you can convert to SAE corrected.

Just to give you an example, my Mustang GT numbers in STD form were 260/300 and 250/292 in SAE form.

Your car probably ran about 250/230 in SAE corrected form which makes sense if you consider about a 15% drivetrain loss.

Your torque curve looks pretty flat to me which is good.

STD is only 2-3% off. So really its not WORTHLESS. lol

Here is the SAE ones I picked up today.

http://www.sah2o.com/russ/g35/dynosae1.jpg

http://www.sah2o.com/russ/g35/dynosae2.jpg