ajahearn

iTrader: (3)

I had my car (02 M/T) dyno'd earlier this week. The graphs look pretty typical (208HP, 225 TQ) for this car (stock). What I'm hoping to discuss is some comments made during the testing by the crew of the testing place. The HP/TQ graphs look pretty good up to about 4900RPM. At this point the relatively flat TQ line starts dropping (consequently the HP line flattens out). Everything stays this way up until ~6300RPM where the testing was stopped.

Several of the technicians there felt that the ECU or something was mechanically limiting the engine. The argument was made that oxygen starvation would have the torque falling much faster (along with the HP). I checked around and the only thing I can find that improves torque is the additional of variable intake runners (which the 02's supposedly have). So my question is this an indication that the runners are not working or are they simply working but not as well as one would hope (perhaps the VIAS prevent the fall off on the HP curve). Anybody have any ideas?

Bags

iTrader: (3)

OK, from what you said the HP curve flattens out not falls off. If you VAIS is not working your peak HP should be about 4900-5100 rpms.

Where is your peak HP and TQ?

Can you scan or take a pic of the dyno graph?

ajahearn

iTrader: (3)

As I understand things, HP is really derived from TQ, and TQ is more meaningful (as its what drives the car). The TQ line is relatively flat (200 to 225, averaging about 215, peak is 225.8) up to 4900RPM's. From 4900 to 6300 it drops about 43 ft. lbs./1000RPM (which is to say that @6300 RPM, I'm getting about 165).

This means the HP line basically flattens out from 4900 to 6300 @ 205HP. The HP peak varies for the 3 tests and occurs anywhere from 5100 to 5400 RPM.

I have to plead ignorance to engine graphs. Is it normal to expect this kind of graph? My original question is would the HP drop if I didn't have the VIAS? Or should the VIAS keep HP climbing (slowly perhaps)?

I'd like to understand why the engine basically flattens out at this point. And if there is something that can be done to change this. Thanks for the help.

Bags

iTrader: (3)

I have a 97 maxima WITHOUT the VIAS, so what help I am trying to provide is from what I know/seen of other dyno's of 5th gen max's

The HP SHOULD go to redline... I think.. here is a post showing a dyno graph with and with NOS.. look at the without nos HP and TQ lines

http://forums.maxima.org/showthread.php?threadid=128371


how does this look compared to yours?

Your numbers seem to be slighty, 5 hp/9 tq , than the other stock 2k2 6 spds I have seen

The dyno pic seems to peak at about 5700 or so

just trying to help..have you tried the 5th gen forums?

ajahearn

iTrader: (3)

The non-NOS is a good example of my graph. You can see around 5K RPM the TQ drops down and the HP flattens off. The NOS seems to simply bump this line up (granted by almost 100). But still the graph drops around the same point. This again indicates that something inherent in the design causes this to happen. This leads me to believe my car is normal. The addition of a cat back, UDP, etc. may account for the small difference in the non-NOS setup (confirming my suspicion that only a SC or NOS setup really makes a difference).

La Jolla Max

4th gens have intake manifolds with longer intake runners. These help optimize the engine for mid-range (which the 4th gen delivers aplenty). Consequently, at higher rpm's the engine severely runs out of breath: peak power occurs at 5600rpm, and by redline power has dropped severely.

3 liter 5th gens (which of course have said variable intake manifold) make peak power at (or I think it may be past) redline. US spec 4th gens that have the middle east-spec variable intake manifold fitted show a similar power curve to these 5th gens.

So, your 3.5 liter Max is making peak at around 200rpm shy of redline. I wouldn't be worried, as that's far closer to redline than most other cars on the road I think it's due to the extra engine displacement the 2k2 has: that manifold may need even shorter runners to the larger engine breathing properly.


btw, the horsepower = (torque * rpm)/5252

ajahearn

iTrader: (3)

I'm assuming you didn't typo, as my peak HP is nearly 2000 RPM's short of redline (7K). That's pretty far in my mind. I'm wondering if the VIAS setup on the 3.5 liter is the same as the 3.0 liter and if that might explain why its off so much.

Keven97SE

You just described every 2002 dyno plot I've ever seen (~4-5). That's just the inherent power/torque band of the engine. Yes, the torque falloff around 5000 rpm does indicate the engine is starting to get inefficient, but it could be due to numerous things...intake manifold not optimized for high rpms, mild camshafts, etc. I don't think it's the ECU, because I saw one 2002 dyno plot that also showed a air-fuel ratio plot, and it was pegged right around 13.5-14.0 from 3000-up, which is just about ideal (slightly richer than stoichiometric 14.7).

It's not your car, it's just the way Nissan designed it.

brianw

iTrader: (3)

He's absolutely correct. I suspect the cams on all the VQ's in the Maximas are pretty mild, actually. I'm curious about the MEVI in the stock 2002's though, especially when compared to the `02 Altima. SCC showed a big difference (Maxima had 15 more HP, curves looked similar though), but others aren't reporting much difference at all.

dwapenyi

iTrader: (3)

Yeah, the 3.5 Maxima seems to be not fully optimized. I used to think that maybe Nissan was gettng lazy, having built such a great V6 for a long time. But, it seems, it may have always been part of the plan. They must have saved all the good stuff of the VQ35 for the 350Z. Can you say 287 HP from 3.5 liters?

Nissan did it before. They built a variable intake manifold for the 95-99 Maxima, in 98. So 98-99 Maximas could have been built with it. But no, they saved the glory for the 2000 Maxima. You can sum it up in one word: Marketing.

DW

emax02

iTrader: (1)

With 208 FWHP there is nothing wrong with your VIAS. Reason power drops off at around 6K RPM is becasue your car is not moving enough air. If you want your car to put down 217 FWHP at 6500 RPM like mine then do a complete exhaust, intake and most importantly a Y-pipe conversion. I'm currently worken on putting the Z Manifold on now, this should help a lot up top.

Gears & Crosses

Ajahearn,

You are right, HP is derived from torque. Here is the mathmatical equation:

HP = Torque x RPM / 5252

As you can see from the formula; the more torque you make, the higher the Horsepower.
Also, if you keep the Torque amount the same, but increase the RPM, then HP will also increase. This can be counter productive however, if you cannot change the car's gearing to get the engine quickly into the elevated RPM range.

I hope this helps,
Gears