Well the main reason to dyno is to see gains of future mods. Not for bench racing so if your not happy with the current dyno go to the same one everything being as equal as possible (before you do more mods). Or go to another one and be sure all factors are in place before they do the pulls. ie. fuel cut 7200, and be sure they are in the 1:1 gear. You basically need a solid baseline dyno done properly and then your all set.

 

Stick with the same dyno. Since this was a Dynojet, the only thing they can change is the correction factor for ambient conditions. I've personally seen this at the shop I go to. The operator was showing us how aftermarket companies can make power magically appear by simply inputing fake ambient conditions. You could make a G show a 30hp gain from an air filter if you really wanted. It's that easy.

A Dynojet is a terribly simple device. It's just a weighted drum. The drivewheels are strapped to the drum and an electronic pickup is placed on an ignition wire. From here the engine rpms are read, the tranny is placed in a gear that closely matches a 1:1 ratio, the rpms are brought up to the desired rpm, the operator hits the "record" button, and then goes WOT. From here the Dynoject measures how fast the drum is accelerated in relation to rpm. From there it measures torque from which HP is calculated. It's very simple and there's really no error. A Dynapack or Mustang style dyno is different because the operator can vary engine load by using a brake on the drum. These dynos are excellent for tuning cars, however lots of variance is introduced and you must have an operator that knows what they're doing because the ending numbers can be greatly influenced.

 

It's all based on torque/rpm and the gear you're in. A lot of people fail to realize that a dyno torque number is the torque value for a 1:1 gear ratio and that in a gear like 1st, a car with a measured 200wtq in 4th gear (1:1 ratio) could actually making 600+wtq in 1st gear (3:1 ratio). Gearing is a torque multiplier. The basic goal of calculating shift points is to start each upshift gear with fractionally more torque than the last gear left off with.

Here's a calculation for a 97 Maxima so you can see how's it's done and how shift rpms can vary depending on gear:

http://www.boostaholic.com/maxima/dyno/shiftpoints.html

Having a dyno printout of your power for every 100rpms is crucial for calculating the correct shift points. Since you said your power peaked at 6500rpms and since I've seen and calculated a whole host of other VQs with similar powerbands, it's safe for me to say your shifts need to be in the rpm range I stated.

A good example of how shift points can change is my old 96 Maxima. With the stock intake manifold and aftermarket intake and exhaust, the car made 183whp@5500rpms and 193wtq@4400rpms. Power fell off like an anvil after 5800rpms. The car ran a best of a 14.6@96mph. The calculated shift points were:

1-2 6600rpms
2-3 6300rpms
3-4 5800rpms

Then I added a variable intake manifold from the overseas Maxima. Now my car was making 190whp@6300rpms and 185wtq@4800rpms. Peak power held on right to the 6500rpm limiter. The calculated shift points now became:

1-2 7100rpms
2-3 7000rpms
3-4 6800rpms

One problem though, I only had a 6500rpm limiter!!! Even though the car had more peak power, I couldn't execute the correct shift points. As you can also see, the new intake manifold traded low rpm torque for topend HP, much like the 298-300hp "high rev" VQ does. With the new intake manifold, my Maxima still ran 14.6s@96mph as it did before. Reason being the car didn't get off the line as hard and I couldn't utilize the full powerband with the stock limiter.

I then ordered the JWT ECU which extended the rev limiter to 7000rpms and added ~10whp/10wtq in the midrange, right where my car needed it. Now the car made 200whp@6300rpms and 195wtq@4800rpms. INSTANTLY the VQ was transformed. The car went 14.3-14.4@99mph+ at the next track outing.

Hopefully that shows you how crucial shift points are to a car.

 

I agree with you 100%. Sad thing is a lot of guys on this site only care about a peak HP/TQ number so they can put it in their sig and win the bench race.

 

The only reason I want to try another dyno is to make sure they do it properly, not for bench racing. If what you say about the 1:1 gear is true, then that would be 5th IIRC. They definitely did not run it in 5th. Also, after talking it over with some of the other owners there Saturday, I'm pretty sure they only ran it to 6500/6600 then let off, which would explain the sudden drop.

I'm not interested in getting a better PEAK number. But I am curious to see if the curves match.

 

It's nice to know that they're easy to operate. But as I've stated in my reply to Gting, I just want a "second opinion" to weed out operator error. As easy as they are, you pointed out that the rpm pickup could have been off, or the operator possibly could have even let up too early. If I go to a second location, it will be purely to see how they perform the pulls, and to see the curve.

There's another dynojet a few miles from my work, so I might try to go there during lunch sometime. The only problem is that it's like $60 for 3 pulls, and you get a graph with hp/tq, but not a/f mixture.

 

DUDE... that is exactly the kind of information I've come to expect from you. Thank you very much. Maybe somebody can write up a synopsis of your response, and a few of your others, and "sticky" it. Some type of "best of" thread. I'm sure this stuff will be repeated again and again, but I'm really getting tired of researching information on this site when every search term I use causes the search engine to just give up.

I'll definitely take a loot at that calculator.

Again, thanks man.

 

Ok cool. Double check what 1:1 gear is and do some runs right to 7200. I am pretty sure the peak power on a 05 6spd is 6500+ so if they let off 700rpm too early it really isn't accurate. If you can post up the graphs and Mr. DaveB will give you the accurate shift points!

 

Well, if the pickup wasn't on the right wire, they'd know it right off the bat. The rpms will dance around on the computer screen if the pickup is getting interferance or is attached to the wrong wire.

I think you're completely right in your assumption that the operator did let up early. He probably figured since the other Gs were tapping the limiter at 6600rpms, yours would too. When you get redynoed, tell them to take it to the limiter. It won't harm anything.

Honestly, I wouldn't bother going to another shop. The numbers can't be compared between the two machines. I'd just stick with this shop and tell them to go to the limiter next time.

The differences between using 4th or 5th won't be much. If they used 4th gear the first time, then use it for all other comparison runs. Remember, reduce the bias as much as you can. For fun you might want them to run in 5th just to see what the car will do. Chances are there won't be a ton of variance (maybe 3-5whp).

Don't get too caught up in the numbers. You've run at the track and your numbers are pretty good for an 05 with low mileage, running in hot air, and a relatively new driver. I'm certain you'll be close to 14.0s when the cold weather rolls around and you've got some more passes under your belt. Hell, it took me about 50 runs to get my Maxima to go from consistent 15.4s down to consistent 14.7s with absolutely no modification changes. The problem was I had never raced a FWD car, I couldn't figure out how to launch effectively, and my shift points were all wrong. With a little practice and cooler air, I knocked off .6-.7 seconds and gained 3-4mph with no changes to the car.

 

Thanks for all the input guys. I've decided to go back to the same location during lunch sometime. The original rate was $30 for three runs, but now I'm gonna have to pay the normal $55. Oh well.

Anyway, here's the scan. Let me know if you guys can glean anything that hasn't been covered yet.

 

Ya you can see that at 6500rpm your HP has not yet dropped off. Go back to the shop and see if they can give you a deal again just explain that they didn't go to fuel cut off. They might give you some sort of deal...

 

Honestly, I'm really not trying to run this thread into the ground, but...

I've spent the last few hours trying to track down dynos from other 05 6MT, coupes or sedans. I was mainly interested in seeing the curve beyond 6500. Anyway, I've noticed that almost *everybody* dyno'd much, MUCH more torque than I did. I'm not trying to compare numbers directly, just the deltas. For example, at 241/210, that's a different of 33. Many people dynoing in the 240 to 245 range were also putting down 220+ ft lbs. Why am I running so low?

And lastly, I have scanned and attached the wife's dyno run. It's an 04, 5AT, bone stock. No ztube, middy, anything. I was kind of disappointed; she was downright pi$$ed. The graph is out of scale(the peak it at the top of the graph), but what's got me so curious is the fact that she's running right about 190hp at 3800/3900, right up to 5k. Then it ??dips??, then rises again to peak @ 6300/6400...

Can anyone explain the curve here?

 

Thanks for the posting the plots. You're right about the conditions, they downright sucked. The correction factor (CF) was a 1.04 which is pretty high for a CF. The higher/lower the CF the more the data can get skewed because of the amount of correcting that needs to be done. Ideally you want the CF to be within .1 of 1.00.

Everything looks fine on both your plots. Your wife's car is putting out pretty normal numbers for an 04 5AT. Your numbers seem pretty much right on two. I think heat soak and crappy weather is probably why you're seeing the lower torque. I wouldn't be surprised for your car to hit 245whp/220wtq in 60-70 degree weather.

Your wife's 04 power curve with the power spike at 5000rpms is normal. I think it's either the variable cam timing kicking in or the flow characteristic of the intake manifold. It's interesting to note that your wife's 04 5AT is basically making the same power as your 6MT till about 5500rpms.

 

First time I've heard a wife being pissed at a dyno. My wife isn't even sure what a dyno is, she just knows that it takes up half my day when there's a dyno day.

The dip at 5200 is very common on G35s, possibly a valve timing switch over.

You can also see what people mean by stock VQ35s having poor top end. From 5000 to redline, it's only about a 10 HP again. Some mods on the intake side of the engine will help fix that.

 

Just as reference, the red line below is after a 3/8" motordyne spacer, blue is before. My power stays nearly flat up to 7000 RPMS with a plenum spacer, drop in K&N and z-tube. The blue line still doesn't drop that much after peak HP.