ajk4

i took my new db touring (1250 miles) to the dyno today and here is what i came up with. all three pulls were done in 4th gear. all in all i was pretty happy with the results, considering i've seen some 6mts dyno around the same or worse.

ajk4

here are the DIN numbers.

apex locator

iTrader: (5)

your torque #s are off. should be in the 220s according to the graph. i dont know why it started off so high.

ares

iTrader: (2)

no according to the graph it is correct. but theres no way its correct... way too high.

hp is about right for an auto tho, not bad at all.

mgl

iTrader: (10)

ajk4: got any mods on the car?? or just bone stock.??

ajk4

the car is stock, and yeah i noticed that the torque numbers were off. anyone have an idea why? maybe the dyno needs to be recalibrated or something? it was a dynojet so im clueless as to why the numbers were so high.

Resolute

iTrader: (2)

The tq was high because you dyno'd in 4th. The the tq posted is what was measured at the wheel, and then corrected for the graph taking into account the ratio to also calculate hp against the known resistence of the rollers.
EDIT: forgot to mention that I don't know the ratios of the 5at, but I'm pretty sure 4th isn't 1:1, hence my theory on the numbers being so high, and also, no matter what gear used, the tq converter is going to add some ratio low in the rpm band.

ares

iTrader: (2)

no gear ratio would add 40 or 50torque. but I guess the torque converter may have something to do with it. not sure how all that works on a dyno, but I thought autos could get proper numbers on dynos.

ajk4

Gear Ratios
M/T A/T
1st-3.794 3.540
2nd-2.324 2.264
3rd-1.624 1.472
4th-1.271 1.000
5th-1.000 0.834
6th-0.794 N/A
R- 3.446 2.370

so 4th is the right gear to dyno a 5at in. however, im still at a loss for why the tq numbers were so high, im gonna call them tomorrow and see if they have an idea why.

ajk4

anyone dyno a 5at and have problems with tq readings or get a normal reading? with the number of 5ats out there someone else has had to dyno theres.

havabooz

actually..i think ur the first

havabooz

ive been waiting for someone to do it....i would dyno mine..but it already has mods..plus there isnt a place near me

ajk4

in this thread https://my350z.com/forum/showthread....threadid=49800 , it says that mr. twisted dynoed 230/230 (hp/tq) with intake and exhaust. so i dunno what the problem was with the tq reading, so i'm thinking it was their dyno. but if thats the case then the hp reading should be off also.

acmw

iTrader: (2)

Doesnt acosta racing do dynos in wallington nj?

alex30327

This is messed up somehow. Torque numbers are wackey!

Resolute

iTrader: (2)

Dyno a MT in 4th, and all else being equal, you'd pick up an extra 73 lb-ft that would need to be calculated for. Not to mention the torque generated from the wheel's rolling diameter. Now, I have no experience running a dyno, but the gist is simple enough. Measure how fast a know mass can be moved, aka the rollers, and measure this torque over time and the machine can calculate power. Obviously this leaves tons of room for all kinds of errors, but the one thing that is actually being measured is torque. The gearing will have a significant measure of error then if not properly accounted for. Think of Suzuki Samurai running around Utah with 130:1 crawl ratios I would love to see one on a dyno and try to figure out how much torque the motor is actually pushing. I have personally seen dyno sheets that had the power of a SE-R as planned, while the torque was running over 1200 lb-ft, uncalculated due to an error with the dyno system. Now, with an auto, I have to say I have never seen an auto dyno sheet before. This actually surprised me to think about it, but in any case, unless the tq converter could lock-up, and I doubt ours does, it will never be 1:1. There will always be some reduction as the fluid is not efficient enough to transfer 1:1 ratio between the two halves. I used to have a book on Torqeflights for my IH, and I think the difference was marginal like 1.05:1 or something for non lock-up tq converters on average. This could be as much as 13-14 lb-ft. Still, not as far off as we have here, but perhaps the system did not account for this in addition to the tq converter stall ratio, which might start off as high as 2.5:1 until a designed rpm when the two halves are as up to speed as they will get without lock-up. So, all this jibba jabba to say the dyno probably did not calculate the torque reduction properly for an auto.

ajk4

your jibba jabba totally confused me. i dynoed in manumatic or e-shift mode so i shifted all the way from 1st-4th then punched it, so as nissan states that while in 4th gear the ratio would be 1.00 (which would be closest to the ideal 1:1 ratio) so i dont see how it would select a different ratio for the torque converter? of course my understanding of torque converters is very limited so i dunno.

Zyal8ter

here's the result of my Touring 5AT.

Mr Twisted

Ive dynoed ten runs now over 3 days and all the last runs are in the 237.4 hp 240.3tq/ 243.4 -235.7 tq/ 241.6 240.0tq

If someone has a Fax # Il'll fax dyno sheets so it can be posted for all to see.

Resolute

iTrader: (2)

My bad
didn't mean to confuse anyone. I assumed you were doin' this manu-matic. So, even if you shift up to 4th gear, and keep it there, you will still have some discrepency with your ratios. Here's why- on all automatics there is no direct link from the crank to the input shaft on your tranny. They are seperated by your torque converter. The TC is shaped like two bowls lip to lip with each other. Inside each half there are rows of fins that are angled in opposition to each other. The TC works by running fluid from one side to the other. As the crank turns, the fluid is pushed by the fins on one side of the TC into the opposing positioned fins inside the other half of the converter. The fluid movement and the shape of the TC causes the other side to move as well. To demonstrate this, put two house fans together, turn one on, and the air being pushed through the other one will cause it to spin. This is essentially the torque converter, except it is enclosed and more efficient. However, not entirely efficient. There is some loss between the two on start-up and in constant opperation. On start-up, the crankshaft side of the TC must spin several times more than the tranny side before the tranny side is up to the same speed. This is how come an auto will not stall the engine if the brake is applied like it would with a manual. The engine can keep rotating at low rpm without turning the tranny side very much, but it does still turn. So there is some power transmiting through the tranny at idle with the brakes on, but not enough to overcome the brakes hold. Now, the ratio for most torque converters is around 2.5:1 at idle. So, while you are at a stoplight the engine is rotating 2.5 times for every one rotation of the tranny, but the brakes hold the car from moving, so the driveline can't actually rotate, so the tranny side of the TC can't spin, and the temps in your tranny start to get very hot. Release the brakes and away you go.. now picture yourself on a hill, let go of the brakes, and the car can still pull ahead with no throttle, or at least hold itself steady. This is again because at 800 rpm or so, your motor is still blessed with a lower gear of 2.5:1, or so, from the torque converter. This ratio diminishes at a fairly linear rate until the stall point, or when the two halves spin at close to the same speed. This is usually by 1500 rpm, unless a high stall converter is purchased, which will allow your motor to take advantage of the variable low ratio for a period of higher rpm. Once, above this point, the TC is still not 100% efficient. The crank side will still rotate slightly more than the tranny side, unless there is some lock-up. Lock-up is the term used to designate any device to physically lock the two halves together during rotation. This is done to save gas mileage during cruising. Allison trannies have lock-up in the top 4 of it's five gears. So, with your car, or any car with an auto, my speculation is that the dyno failed to account for some gearing discrepency. However, as I stated, I never ran a dyno, so I am not sure how the program works, but I would be curious to see what happens if you ran on the dyno in plain auto mode with the OD turned off, if that is an option for the 5AT in the Z. I really don't know, sorry, but I hope the torque converter explanation and the reduction abilities makes sense now.