Greetings...I am new to the forums so this is my first contribution.

I took my G35 to a shop today. Dyno conditions were 5543 miles on the car, 4th gear for 1:1 ratio, 65 degrees F, 53% humidity, pressure 30.31 inches, and as I live in Houston (pretty much sea level) I do not know if they used SAE correction or not (it just says SAE Horsepower and SAE Torque). I apologize for my ignorance.

Hot Result: 200.3 horsepower/211 lb ft torque
After 10 minutes cooldown: 209 horsepower/216 lb ft torque
Air/Fuel Ratio: Consistantly 13.6 every run
I am baffled as to why my vehicle makes more torque than horsepower as advertised by Infiniti. The dyno is a Dynojet.

This reminds me of the other 2005 G35AT dyno I saw on the forums, where the poster was wondering about his low horsepower numbers after modifications (216 horsepower I believe). However as you can see my car does not run rich as his did. As I have forgotten what his torque numbers were I do not know how it compares with my dyno result.

I am unsure if it is the dyno or if it's the car. I have pulled off a best quarter mile time of 14.02 seconds (the other 2 runs being 14.2 to 14.7), so if these numbers are right something is off. Of all the cars I've dynoed each one displays the same characteristic...a substantially higher torque output than advertised. My 2005 Altima SE-R dynoed 193 horsepower/201 lb ft torque and is rated at 260 horsepower/251 lb ft torque at the crank by Nissan. However, my 2001 Galant dyno showed 138 horsepower/153.8 lb ft torque, and is rated 190 horsepower/205 lb ft torque which is on par with Mitsubishi's claims. I hope these numbers help you guys with whatever you're looking for.

 

that is pretty low....

i got 227HP on my stock engine.... and mine is a 03. I dont know about now, havnt got a chance to dyno,my estimate is that i should have 245+ at the wheel with the mods i got.

 

you ran a 14 s 1/4 mile with an automatic?? wouuu.. I bet u something was wrong with that dyno... and arent u supposed to be in 3rd gear for automatics? 4th gear for manual?

 

Something's off. 200hp is a bit low. Do you have any pics of the dyno graph?

 

Your quarter mile time alone should tell you that your car is actually stronger than most G35s. I think your dyno is questionable. Perhaps another shop would have better results.

 

Those numbers do look a bit off. Some observations:

Dyno Gear: 4th gear in the auto is indeed the 1:1 gear, but I believe (someone correct me if I'm wrong) that the torque converter will lock up in 4th, whereas it will not in 3rd. Therefor the results can be artificially low when dyno'ing an auto in 4th.

Fans: Were fans used? Was the hood open or closed? Did you have a fan going over the hood, and another fan running underneath to scavenge the radiator?

Car prep: did you monitor coolant and intake charge before/between the dyno runs?

Dyno prep: did the dyno operator "warm-up" the car, then shut it down and retighten the dyno straps?

Wheels/tires: What wheels are on your car? Are they the stocker 17's, or 18's? What kind/size of tires? What was the pressure in the rear tires?

Dynojets are great, easy-to-use dynos. But just like any tool, how one uses it can greatly affect results. For example, because it is a roller-based dyno, tire pressure, camber, and toe can all affect the numbers. If the car was not re-strapped after the warm-up run, it can show low numbers. If the hood was closed, then obviously you're going to have lower numbers. Even if the hood is up, the majority of dyno shops don't have fans that move enough air. If you don't believe me, read this article(orginally posted by pasta): http://www.dinancars.com/whitepapersFile.asp?ID=9

Hope this helps.

 

I'll keep the 3rd gear in mind next time.
One fan placed at front license plate. Hood up.
Car prep - no
Dyno prep - no
Everything is factory on the vehicle, 17 inch wheels, tire pressures are at recommended.
I have my actual dyno graph, but I have no scanner so I cannot show it to you guys. What I'm seeing though is max torque comes as claimed at 4800 rpm but the horsepower peaks at 5950 rpm and falls from there. I may take the vehicle to SGP Racing for a dyno on their Dynapack chassis dyno, and this time request a 3rd gear pull. Of course this will tell me nothing because it's a whole different dyno...

I'm not concerned about the numbers really. I know dynos are only a tool. Just trying to provide you guys with information. Too bad my first shot is kind of buggy.

 

It's good information to share, even if it *might* be inaccurate. The fact that the numbers fall off at 5900/6000 is weird, I must say.

So, two things. First, call the shop and ask if they saved your run files. If so, get them to email the run files to you. You can either download the trial version of winpep and do your analysis yourself, or zip up your run file and post it here. That way, we can look at everything that's going on.

Second. Contact the shop and ask if you can re-dyno for free, or at least get a break against another dyno. It's not up to the dyno operator to know to dyno the AT in 3rd. However, it *is* up to the operator to do a proper warm-up run and retighten the straps. If the operator did not do this, then I can imagine the tires might have spun a bit on the roller at high rpms.

I'd be concerned with using only one fan, and one aimed at the front license plate. If they don't use multiple fans, or larger fans, then I would not use them in the future. Air flow is really, really a big factor. Again, refer to page one of the link I posted. Dinan uses a very large fan, capable of 38,000 cubic feet per minute at 75 miles per hour. Dinan attempts to emulate actual road conditions, meaning monitoring temps and airflow that the car actually operates under on the road or at the track, and attempting to reproduce those same conditions on the dyno.

Here's a picture of the fan they use:

 

14.02 for a stock 5AT? That's a record. Was this a G-tech or was this done at HRP? I want to see a run down of the slip because I'm very curious.

 

you will see lower numbers if the torque convertor is unlocked. You always want the TC locked when you dyno an auto vehicle to get more accurate numbers. You also want to dyno in whatever gear is 1:1 - I believe this is forth for the auto trans - so you were right to dyno in that gear. Dont believe everything you here on these boards.

 

Me too.

 

Could you explain this statement? I'm not challenging you, I'd just like to know. I'm not the most mechanically inclined person, and I'm just learning the whole "car" thing, including details about auto trannies. When I made the statement that the torque converter does not lock in 3rd, and it does in 4th, I was just repeating what I remember reading elsewhere. I did not get that knowledge from the FSM. In fact, I might have had the conditions reversed. That's why I included, in parentheses, the request for correction.

So, how would the torque converter locking, or not, affect numbers on a dyno?

This is traditionally a true statement. But could you elaborate on the reasons *why* you want to be as close to a 1:1 ratio as possible?

There are only two reasons that I know. The first reason is to minimize torque multiplication to the wheels in lower gears. The second is to reduce drivetrain loss, though I admit I don't fully understand this second reason.

In the case of a Dynojet, theoretically the dyno gear will not affect the actual numbers. As I've stated elsewhere, a Dynojet calculates a relative "to-the-drum" ratio by comparing the monitored engine rpm's versus the roller's rpms. This way, number are supposed to be repeatable, and within very close percentage, regardless of the gear used. However, I must admit that I have seen first-hand differences. When I dyno'd back in November, I had back-to-back pulls in 4th gear and 5th gear. My fourth gear run yielded peak numbers of 250.3/227.38, versus my 5th gear run of 249.6/234.06. 4th gear was .2% stronger in peak HP versus 5th, but 5th was 2.9% stronger in peak torque.

And I assume this was directed at me. I don't have a problem with that statement, and I don't take it personally. But I have to challenge it. I'm not an authority on anything having to do with our cars. But I do try to share whatever experience I may have, and I try to qualify points of confusion(as I did). So in this case, if I spread misinformation regarding 3rd/4th when dyno'ing an auto, at least I qualified it and left it open for discussion.

However, when you make such a statement, at least have the ***** to name names.

Along those lines, could you be more explicit in what the OP shouldn't "believe"? Again, not being an ***, just curious. Are you aware that SportsZ Magazine's official dyno procedures dictate using 3rd gear for the g/z when the vehicle is an auto? Are these procedures wrong? If true, then would not every published dyno by the magazine that include autos, be they baselines or measuring a mod's effectiveness, be invalidated?

I'm not calling you out on this topic. Dynos interest me quite a bit, the peculiarities of dyno'ing even more. This is a discussion that honestly needs to occur.

 

The torque converter won't stay locked under WOT acceleration. The lock-up clutch does not engage until the throttle is used at a steady rate. It use to be that the lock-up clutch activated in relation to engine vacuum. When there is engine vacuum (part throttle) and the car is at a cruise and under minimal load in 3rd+ gear, the lock-up clutch engages and the tranny forms a direct connection to the engine as if were a manual tranny. With no engine vacuum (WOT), the clutch disengages. With today's drive-by-wire systems and such, I'm not certain as to how the lock-up clutch system operates. I'm pretty sure it still uses engine vacuum as the base of operation.

In the drag racing world, a lot of automatic cars (Grand Nationals and Supras with GM TH350-TH400s come to mind here) use manually operated autos and the guys have control over the lock-up clutch and they can engage it when they want. It's not uncommon for these guys to lockup 3rd at WOT in order to gain lower ETs and more MPH. FYI, in order to do this, you really need a race-built tranny because locking up the TC at WOT is hell on a OEM TC and tranny.

The JATCO 5AT in the G35 (also used in the Subaru Legacy GT) has a very seemless and smooth lock-up clutch. It's hard to tell when it's locked and unlocked hence the reason many people post that their 5AT doesn't lock-up when in manual mode. Same goes for when the clutch unlocks. It's nearly instant.

You're completely right. Depending on auto or 6MT, using 3rd, 4th, and 5th on the dyno isn't going to make a huge difference. All the dyno reads is the cars rpm in relation to how quickly it spins up the rollers. It really doesn't care what gear you're in. The main reason most shops use as close to a 1:1 gear is to:

1) Reduce "noise". If you dyno in too low of gear the car may spin the rollers too fast and the dyno might not be able to read the data quick enough and you'll get jagged lines and missing data.

2) If you use too high of a gear, you end up putting excessive load on the engine and may spike the engine temps which may effect the ultimate numbers. On low torque cars like NA Hondas, it's not uncommon to dyno them in 3rd in order to keep reduce load on the engine as it tries it's best to power away at WOT from 2000rpms. If they use 4th, it would take a lot of time to spin those rollers from 2000 to 5000rpms.

 

That dyno seems to be off for all his cars. A 05 Altima SE-R dynos around 230 to the wheels as well.