slvrstreak

iTrader: (3)

unless you're FI
I can't speak for the turbo guys but, my power just keeps rising and rising
I'll post up an old dyno sheet when I get home

TeamRX8

iTrader: (25)

not entirely true depending on the engine mods and overall setup

my peak is 9000 and it doesn't fall off anywhere near as much as the OE curve

I would suggest using actual datalogging over a dyno regardless for accuracy under real conditions. Generally speaking, a dyno is a fixed load device that doesn't approximate real world acceleration through the gears with an ever increasing aero load, ect.

TeamRX8

iTrader: (25)

back on the clutch subject, I didn't really consider the sintered iron discs and wasn't familiar with their greater TQ capacity compared to other material options. Also, the reason I steered away from QM is my frustration trying to find information details on them as compared to other suppliers. So a 2-disc setup makes sense in your case. Sorry for mistaking this.

cwatson

iTrader: (1)

I am using a scaled version of the curve below (correlated to real-world velocity vs time curves) when saying the lap sim indicates a 0.5-1s/2min improvement in lap time with reasonable shift times. Area under the curve is clearly greater when shifting at redline:



Also, while MAF is not WHP, the correlation is strong for a constant AFR. You can see the nuances in valve-openings in the data I posted earlier. There is an average of 4 lbs/min (15%) airflow improvement over 500rpm by shifting later. The correct shift point is approximately the intersection of each gears' power curve on a power vs velocity graph. When they don't intersect, shifting at redline is appropriate.

Arca_ex

iTrader: (10)

Yeah I stumbled upon one of their old catalogs which have way better information than their current catalogs. It includes part number, weight and MOI for each unit, and oddly enough lists way more parts than their current catalog. All of the 1x23 splined setups aren't even in their current catalog but they are in the older one and can be ordered from major retailers online still. They definitely need to straighten out their current catalog...

TeamRX8

iTrader: (25)

MAF flow can be misleading. I pull peak MAF flow at 10k, but obviously power and torque is well on the decline then

You really need acceleration rate data to determine the proper shift points.


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MagnusRacing

iTrader: (2)

While it is true that power drops off about 9000rpms (or earlier on a stock motor) that doesn't mean that having the extra rpms doesn't help. When racing sometimes it's great to be able to not have to shift if you're trying to get past someone or if the braking zone is right about where you'd be upshifting anyway. I frequently run my motors to 9500 rpms or more with no apparent adverse effects.

etzilon

I agree. You can set your target RPM but track and conditions will dictate actual shift points; glad our engines are pretty forgiving about this.

cwatson

iTrader: (1)

Agreed. I've always found the best way to extract WHP from road data is to assume a curve shape and correlate to a velocity vs time over 2+ seconds. Below is data from a morning session, showing the uncertainty in estimating power from instantaneous acceleration data. P=FV = (M*Ax+D)*V. GPS dV/dt was used for Ax. Drag assumptions are on the left. Elevation change was not considered. Only data with >95% throttle was considered. Data was binned in 1 lb/min intervals and the statistics are stdev (67%) for the big bars and standard error (stdev/sqrt(n)) for the small bars.

TeamRX8

iTrader: (25)

You are playing theoretical games based on incorrect assumptions. I don't even want to waste my time on pointing it out to you any more, let alone try to understand where you come up with this stuff or are attempting to do.

cwatson

iTrader: (1)

The discussion before was how MAF correlated to WHP. So, I presented a plot of MAF and WHP on track showing there is correlation, but the uncertainty is high. What could be more specific? Which assumptions are incorrect? Where is the theory applied (data above is on-track)? Where is it flawed?

To review:
The question is whether or not it is good to shift at redline.
First plot I showed demonstrates clearly higher airflow by shifting later.
Statements were made that MAF does not correlate to WHP.
I plotted MAF vs WHP showing a correlation but large uncertainty.
You pointed out that all we really need to look at is acceleration in one gear vs another at the same speed, which I am working to generate but worried the data will be hard to interpret without heavy filtering.

Can you provide track data that confidently shows the difference in forward acceleration between two adjacent gears at the same speed? I forgot to log RPM for the weekend so I can't use the standard method to back out gear. I'll have acceleration data vs gear plotted once I sort that out. However, it's going to be hard to read without some additional filtering. Also, samples were not taken at standard intervals (Track Addict logs everything it sees 5-600Hz) which would have to be considered when applying a filter.

I'm thinking the easiest thing would be to some acceleration pulls with different shift points and overlay the velocity data.

TeamRX8

iTrader: (25)

My prior reply is poorly worded as usual. It doesn't make sense to me why you are doing it this way, nor does it seem at all correct in concept, but it is certainly your prerogative to do so.

cwatson

iTrader: (1)

Please be more specific, what is "it"? If I have a concept wrong, I would like to understand why. I originally intended to plot speed vs power to determine shift points but only had clean flow data available, so I looked at that. Yes, flow is not a direct measurement, but it is a good indication of power. I've agreed that we really want to know the acceleration in different gears at the same speed, and am working to get that data but concerned it won't be readable. Please explain the method you would take to determine the correct shift points from track data.

Arca_ex

iTrader: (10)

Like I said before, until you figure out how to factor in the rate of RPM increase at every given RPM and how much time you spend at each RPM in that rev range, AND find an actual way to measure power and not just air intake, you will never be able to find your answer of what is the best RPM to shift. I guess i dont understand going through all the trouble to collect the data and try to analyze it even though the conclusions drawn from it are nearly meaningless.

TeamRX8

iTrader: (25)

Not sure what you don't understand about this? It accomplishes exactly what you are trying to do theoretically with actual direct data instead. This is for general accel shifting. As Magnus pointed out there are times when you need to deviate from may be optimal for competitive strategy.

j9fd3s

isn't acceleration just gain in speed over time? why not just graph rpm, which is automatically over time = acceleration. we don't care about the airflow, we care about power.

simple is better sometimes, especially since we kind of know where the power is, and aren't always going to be shifting there anyways.

this one time at the 25 we put a a steering angle sensor, and brake pressure sensor in the car, so in addition to RPM, gps, yaw, etc etc, we thought we could overlay our drivers data on top of each other and find "the perfect lap"

the problem of course is that the track has width, and a so the length of the lap varies, and if each lap varies, the data doesn't line up, and this is in addition to variations in braking and turn in and stuff.

we sent the truck around infineon/sears point/sonoma raceway and found out that driving on the inside vs the outside is like 1/8th of a mile difference in length, which is where the variation comes from, the laps ARE different lengths.

the engineering dept went to look at textbooks, and found that they are really thick and written people have whole careers analyzing this kind of data, i talked to a rocket scientist and he told me this was the same problem that they had on the saturn 5 rockets guidance system.

with data you can get way over your head really quickly, and we've scaled it back a bit and we look at the braking into turn in, into acceleration now, smaller stuff, and we can do it in the pits without a team of people in lab coats.

TeamRX8

iTrader: (25)

it has to be analyzed on a differential mathematics level which is not so simple in reality depending on how accurate your datalogging is

an accelerometer will make your life much easier, you just need a long enough straight to determine the overlap rpm points between each set of consecutive gears

j9fd3s

oh yeah forgot the gearing

i always forget some mundane detail

-michael bolton

blu3dragon

iTrader: (1)

I think the simple way to do this is to plot speed vs time. You can then fit a straight line to each part of the plot either side of the gear change and use the intersect point of those lines to determine the optimum shift rpm.

EDIT: just looking at a couple of my own plots, I am shifting 3->4 at ~8600 rpm and the optimal shift point looks like it is a slightly higher rpm than that. Car is stock, but no cat so might have slightly higher relative top end power compared to a 100% stock engine.

TeamRX8

iTrader: (25)

simple, yet inaccurate

especially if using a Cobb AP. There is a lot of lag on it's data capability. Often the data on the same line is not really all on the same time increment even though the log indicates that it is.

etzilon

FWIW, AiM RaceStudio uses throttle pos (threshold), linear acceleration (from accelerometer), GPS pos/speed and RPM to estimate HP/torque.

blu3dragon

iTrader: (1)

I think this method should be reasonably accurate. Obviously, the further you are from the optimum shift point, the less accurate it will be, so if you are e.g. 500 rpm off, then it might take a couple of iterations to get close to perfect.

Didn't know that about the Cobb AP. I'm not using one, but even if I was I'm only suggesting use of a single channel (speed) so lag should not matter anyway.

Oh, and looking at a graph of speed vs time is the same as looking at acceleration data so I think we're in agreement anyway

etzilon

OK, fellow rotards... RENESIS gave up after my first lap... Because racecar.

SilverEIGHT

Sorry to hear that. Been there, done that! Completed the warm-up lap, past the start finish and exit of T-2 I lost the engine. So I can understand your pain. That weekend cost a lot of money.

TeamRX8

iTrader: (25)

EC is such a lousy track layout too, but if she's gonna blow then that 's the place it will happen since its pretty much just a series of drag strip straights connected by tight turns. I'm a bit shocked you'd drive all that way to run there.