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Discussion Starter · #1 ·
We enjoy good discussions about turbos, describe their performance, recommend to others what they should buy for what uses, etc, etc. We often mention that one consideration is to maximize the "area under the (torque) curve" but I have never seen it actually measured, listed or compared. I thought it might be interesting to see what the differences might be.

The simplest way would be to just note your engines torque at 500 rpm intervals across the rpm range and add them up from your dyno plot. As this "area" is supposed to give a broader picture of overall performance than peak power or a point at which it hits 200 lb.ft., I thought it made sense to look at the full operating range. As 2500 rpm is shown on most dynos, and is the engine's speed at 55 mph cruising in top gear, that looked like a good place to start. Most dynos are run out to at 7000 rpm or more, and the more spirited driver would consider that important as well.

Since dyno results vary from dyno to dyno, day to day, and factors like temperature, humidity and altitude all affect results, not to mentions non-turbo mods and car setup, this is not going to be a definitive guide but should provide some useful insight. Those with specific performance goals can break down the data to suit there own needs and compare. List torque at each 500 rpm point from 2500-7000, add up the total and show it along with information like your particular turbo, mods, dyno type, boost level, etc. Mention your peak torque, hp and 200 ft lb stats if you like also!

Bruce
 

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Discussion Starter · #3 ·
To give you some target practice I'll kick it off with my set-up and see how long it takes to be beat :)

Garrett GT28RS, .64 AR.
17 psi with 94 pump and WI, Dynojet 248 STD correction close to sea level.
Intake, 3" DP and exhaust, Greddy IC, EBC, G-Force ECU upgrade (partially tuned), water injection, upgraded fuel system, AFM and unopened engine.

Torque at 500 rpm points starting at 2500 rpm is 150, 220,
250, 270, 275, 275, 265, 230, 220, and 195 at 7000rpm. Total torque is 2350.
 

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Discussion Starter · #4 ·
That was fast Jeff! How about some more info.
 

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wow ive been thinking about this for awhile now.... I was wondering if you can use anti-derivitives to find the total area under the curve, but since dyno graphs is not a functions I guess we have to do it the long way. But with the interval of 500 RPM i think that is too wide and the uncertainties of area under the curve is bigger than what it has to be.
 

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Discussion Starter · #6 ·
DR3AMR2 said:
wow ive been thinking about this for awhile now.... I was wondering if you can use anti-derivitives to find the total area under the curve, but since dyno graphs is not a functions I guess we have to do it the long way. But with the interval of 500 RPM i think that is too wide and the uncertainties of area under the curve is bigger than what it has to be.
I'm not exactly sure what you just said, but this is probably a reasonably straight forward method to get comparative data for our limited purposes. Only pretty small spikes and valleys could fit in between 500 rpm increments and really wouldn't skew the results.

Also, it would be great to get numbers from all kinds of setups including stock turbos at stock boost and high boost. I lost/misplaced my old dynos and can't do that.
 

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Here is a picture of the dyno plot:



Here is the data I eyeballed:

2500 130, 3000 160, 3500 185, 4000 230, 4500 2500, 5000 260, 5500 255, 6000 250, 6500 220, 7000 195

If I sum the torque figures that yields: 2135

Power mods: CT-26 46-trim compressor with 12-degree clipped turbine at 19.5psi, 93+100 octane mix, MBC, Greddy IC with 9" HP Spal fan, gutted and port matched TVIS plate, 2.5" KO DP, 3" B-pipe, 3" Borla muffler, 550's, Aeromotive FPR, Walbro 255lph pump, SAFC down low (stock head, block, pistons, AFM...)

Not quite as fast spooling with the clipped turbine and no TVIS.
 

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just use a Reiman sum. It is just adding up the area of the rectangles, or trapezoids under the curve. To get a more accurate result you should use the smalles rpm interval.
 

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The only problem I see with this Bruce, is that not all dyno operators start at 2,000rpm's. I have the raw data for mine and he didnt start going until 2420rpm's. So my first point of 2500 only has 63ft.lbs. It built extremely quick after that but I just wanted to state that this cant be completely accurate unless all dyno's were started close to 2,000rpm's.

2500=63, 3000=142, 3500=144, 4000=168, 4500=212, 5000=290, 5500=312, 6000=284, 6500=254, 7000=228

TOTAL = 2097

Mods: Gen3 motor, supra fuel pump, Greddy IC, Apexi GTspec Exhaust, Murbonracing T4 50trim Turbo Kit, Blitz Flywheel, Blitz Intake. This was done @17psi. If this dyno pull had started at 2,000rpm's Im confident I would be at around 2150+.
 

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Interesting post Bruce. Here are my results...



Thanks to Ken for the graph...I don't have runfiles handy. Runs done on a Dynojet 248c, 4th gear.

TQ readings @19psi, 500RPM increments. I just eyeballed them, so they are not exact...

2000=125, 2500=165, 3000=235, 3500=310, 4000=320, 4500=330, 5000=325, 5500=310, 6000=280, 6500=250, 7000=220, for a total of 2870.

TQ readings @ 25psi...

2000=125, 2500=165, 3000=235, 3500=360, 4000=405, 4500=415, 5000=400, 5500=375, 6000=340, 6500=300, 7000=250, for a total of 3370.

200Ft/lb by 2740RPM
300Ft/lb by 3300RPM

Mods: 2.2L, ATS TD06, 850cc injectors, Intercooler etc....
 

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Discussion Starter · #11 ·
93smgturbo said:
The only problem I see with this Bruce, is that not all dyno operators start at 2,000rpm's. I have the raw data for mine and he didnt start going until 2420rpm's. So my first point of 2500 only has 63ft.lbs. It built extremely quick after that but I just wanted to state that this cant be completely accurate unless all dyno's were started close to 2,000rpm's.

2500=63, 3000=142, 3500=144, 4000=168, 4500=212, 5000=290, 5500=312, 6000=284, 6500=254, 7000=228

TOTAL = 2097

Mods: Gen3 motor, supra fuel pump, Greddy IC, Apexi GTspec Exhaust, Murbonracing T4 50trim Turbo Kit, Blitz Flywheel, Blitz Intake. This was done @17psi. If this dyno pull had started at 2,000rpm's Im confident I would be at around 2150+.

That's a good point and I'm glad you mentioned it and included it along with your other info. I'd suggest that anyone else also point it out and even show a reasonable estimated (est.) number to make it more comparable. There's no prize or award so it doesn't have to be 100%.
 

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Discussion Starter · #12 ·
ATS_Scott said:
Interesting post Bruce. Here are my results...

Thanks to Ken for the graph...I don't have runfiles handy. Runs done on a Dynojet 248c, 4th gear.

TQ readings @19psi, 500RPM increments. I just eyeballed them, so they are not exact...

2000=125, 2500=165, 3000=235, 3500=310, 4000=320, 4500=330, 5000=325, 5500=310, 6000=280, 6500=250, 7000=220, for a total of 2870.

TQ readings @ 25psi...

2000=125, 2500=165, 3000=235, 3500=360, 4000=405, 4500=415, 5000=400, 5500=375, 6000=340, 6500=300, 7000=250, for a total of 3370.

200Ft/lb by 2740RPM
300Ft/lb by 3300RPM

Mods: 2.2L, ATS TD06, 850cc injectors, Intercooler etc....

Yikes...awesome numbers! We're starting at 2500 though, not 2000, so your total at 19 psi would be 2745 and 3245 at 25 psi. You should post some others with different setups and the CT27(s).
 

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If we want to actually gauge acceleration, we should measure area under the torque curve in the powerband where we'll be racing.

A car that revs to 9,000 rpms will have almost 2,000 rpms of torque curve, which doesn't necessarily accurately reflect it's ability to accelerate.

Measuring the area under the torque curve from (redline - 3500 rpms) to redline would be the best way of doing this, I think.
 

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The only plot I have access to right now was with the CT26, Apexi intake, TKS sport exhaust and a MBC at 15lbs running out to 6500.

2500-130
3000-170
3500-220
4000-255
4500-230
5000-220
5500-195
6000-170
6500-160
Total=1750
 

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What's also interesting about this thread is that by calculating the area under a curve at a given rpm, you're close to calculating the power: area = (x axis increment) * (y axis value) = rpm * torque = power.
 

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Discussion Starter · #17 ·
oldster said:
The only plot I have access to right now was with the CT26, Apexi intake, TKS sport exhaust and a MBC at 15lbs running out to 6500.

2500-130
3000-170
3500-220
4000-255
4500-230
5000-220
5500-195
6000-170
6500-160
Total=1750
Let's add 7000-150 (est) so it can be compared.
Total=1900
 

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Bruce H. said:
Let's add 7000-150 (est) so it can be compared.
Total=1900

I would have added 350 but what the heh, it's your thread............. :smile: I'll look at my runs after the upgrades and post after I get home.
 

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Discussion Starter · #19 ·
This is going to be very interesting and I'm already surprised by some of the results. I don't think there's always going to be a strong correlation between this measure of power and others that we've been using. Hopefully someone will come up with a way to organize and/or summarize these results in a meaningful way.
 

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Discussion Starter · #20 ·
oldster said:
I would have added 350 but what the heh, it's your thread............. :smile: I'll look at my runs after the upgrades and post after I get home.
You must be good friends with Scott :smile: We're watching you guys!
 
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