Had my car on the dyno today. - The Saab Link Forums

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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 09-17-2007, 06:15 PM   #1
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Had my car on the dyno today.

Have decided never to use another mustang dyno again today. They just read way to far off from what should be seen at the wheels.

Mustang Dyno read WHP: 184 and WTQ: 214

My car on the dynojet did WHP 172.9 and WTQ 206.9 at SOC.

Even with the correction factor they told me to use to get crank numbers it still wasn't close so a quick call to Jak and based on his experience with Mustang dyno's he told me to correct the wheel numbers by 13% before using the correction factor I was given.

Succes. Crank number for horsepower came out to 270. Now my question though, about torque. Do you correct for this as well or is it something you don't correct for? I remember listening on a discussion about it at SOC that you don't but if I do with the wheel number unadjusted with the 13% I get 270 and with the 13% I end up with 314. Either could be right to me in my mind as I usually spike 22 to 24 psi before settling to 18-19 psi so weigh in all.

Final numbers: CHP 270 and CTQ 278-314

Air fuel at WOT bounced between 10.5 and 11.5 and idle was 14.5.

Now for the whole run. I ended up on the dyno for 2 hours for free. I did it at the local Ivy Tech school and the proffessor in charge of the dyno ended up getting his students out of there other classes to observe and run (I drove though). Normally they run chevy V8's and don't see forced induction cars so the professor had me talk about the car and the way the ECU runs the car and all sorts of other stuff. It was a fun 2 hours. I did end up with one casulty..........one of there heavy duty tie down straps found its way melted to my downpipe which explained the smell we had the whole time .



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Old 09-17-2007, 06:18 PM   #2
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My stock Linear pulled more than that at the wheels. Very confused.
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Old 09-17-2007, 06:20 PM   #3
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I read 210whp w/ stock software on a mustang dyno. They read fine. I'd say either the dyno was not calibrated well, or something is amiss with your car.

What model of mustang was it?

Remember, the true loading mustang dynos are MORE accurate than dynojets, this is WIDELY accepted.

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My stock Linear pulled more than that at the wheels. Very confused.
On a mustang dyno too!
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Old 09-17-2007, 06:21 PM   #4
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Quote:
Originally Posted by Topher View Post
My stock Linear pulled more than that at the wheels. Very confused.
Hence why I will never pull on another mustang dyno. Also the pull at SOC was with stock software and a t25. Today was to measure the td04 and Jaks software. I'm going out to Nicks on the 13th for the get together which I got off for today (week prior I'm gonna go see my son) to confirm what the true numbers.



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Old 09-17-2007, 06:21 PM   #5
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Here's what I don't understand-- what is with the correcting of numbers I always see on dynos. How is this even calculated and why isn't the dyno ever correct?
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Old 09-17-2007, 06:22 PM   #6
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Quote:
Originally Posted by JK View Post
I read 210whp w/ stock software on a mustang dyno. They read fine. I'd say either the dyno was not calibrated well, or something is amiss with your car.

What model of mustang was it?

Remember, the true loading mustang dynos are MORE accurate than dynojets, this is WIDELY accepted.
I don't know Jessop. Everything was running fine. A/F was good all the way through, boost held 18psi to redline and spiked 22psi everytime I started a pull. Like I said I talked to Jak and came up with an adjustment he thought was needed and got those numbers. Will confer them on the dyno at Nicks shop in October.



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Old 09-17-2007, 06:23 PM   #7
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And I am even more confused. If you pulled 184 hp at the wheels, factoring in a drivetrain loss of 13%, that would put you at ~208hp, not 270.

Am I reading this wrong???
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Old 09-17-2007, 06:24 PM   #8
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Quote:
Originally Posted by Deek View Post
Here's what I don't understand-- what is with the correcting of numbers I always see on dynos. How is this even calculated and why isn't the dyno ever correct?
Dyno's show whats at the wheel. If you want at the crank then you have to account for drive train loss. The other "correction" you hear of is to adjust for atmospheric conditions so that you can compare to somebody like JZW up in Colorado at altitude vs. down at sea-level.



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Old 09-17-2007, 06:24 PM   #9
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Deek, those correction numbers that you see on dyno slips are SAE corrections which account for atmospheric conditions (temp, pressure, altitude, humidity, etc). Converting WHP to crank HP is a different thing altogether.
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Old 09-17-2007, 06:25 PM   #10
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Quote:
Originally Posted by Topher View Post
And I am even more confused. If you pulled 184 hp at the wheels, factoring in a drivetrain loss of 13%, that would put you at ~208hp, not 270.

Am I reading this wrong???
Followed by a correction of 30% that the professor said to adjust for so.......

100/(184*1.13)=130/x...........solve for x and you'll get 270 crank horsepower.



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Old 09-17-2007, 06:25 PM   #11
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Why can't the dyno just factor that in automatically though? What I don't understand is how the figure of 13% or whatever % is arrived at.
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Old 09-17-2007, 06:26 PM   #12
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Quote:
Originally Posted by NahumCC View Post
Hence why I will never pull on another mustang dyno. Also the pull at SOC was with stock software and a t25. Today was to measure the td04 and Jaks software. I'm going out to Nicks on the 13th for the get together which I got off for today (week prior I'm gonna go see my son) to confirm what the true numbers.
The brand of dyno does not matter. To truly gauge power increase you need to do a baseline run on a dyno. Then do your modifications and run on the SAME dyno.

It isn't a matter of how high the reading is, but rather the % increase over the baseline.

And hp (especially CHP) is merely a penile lengthener, especially if you are quoting CHP off of non-mustang dynos.
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Old 09-17-2007, 06:29 PM   #13
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Quote:
Originally Posted by Topher View Post
And I am even more confused. If you pulled 184 hp at the wheels, factoring in a drivetrain loss of 13%, that would put you at ~208hp, not 270.

Am I reading this wrong???
You are actually figuring it backwards. To figurpe it correctly you have to think of it this way

X = crank HP
Y = whp
13% loss = .87(X)=Y

if you have Y you need to divide by the multiplyer, so Y=184hp then,

184/.87=211.5

The difference seems minor, but it compounds as the hp rises.
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Old 09-17-2007, 06:30 PM   #14
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Followed by a correction of 30% that the professor said to adjust for so.......

100/(184*1.13)=130/x...........solve for x and you'll get 270 crank horsepower.
I guess I am not following the correction, especially a correction of 30%. That is super high.

Just go some where and pay. I wouldn't trust these numbers. They may have been spot on or they may have been WAY off.

But I just don't see 184 whp translating to 270 chp. That's a huge jump (nearly 50%)
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Old 09-17-2007, 06:31 PM   #15
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Quote:
Originally Posted by Deek View Post
Why can't the dyno just factor that in automatically though? What I don't understand is how the figure of 13% or whatever % is arrived at.
Deek I talked with Jak about it.

Quote:
Originally Posted by Topher View Post
The brand of dyno does not matter. To truly gauge power increase you need to do a baseline run on a dyno. Then do your modifications and run on the SAME dyno.

It isn't a matter of how high the reading is, but rather the % increase over the baseline.

And hp (especially CHP) is merely a penile lengthener, especially if you are quoting CHP off of non-mustang dynos.
Topher I don't know what seems to be your thing tonight man. I had a baseline done on a dynojet up at SOC and I know based on having driven with Jak's software for a week over the past couple days before dynoing that something isn't right with the dyno read out but the A/F is right and that was the most important thing I needed to find out for Jak. I'll be down at Nicks shop in October and I know I'll get accurate readings for certain.



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Old 09-17-2007, 06:32 PM   #16
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You are actually figuring it backwards. To figurpe it correctly you have to think of it this way

X = crank HP
Y = whp
13% loss = .87(X)=Y

if you have Y you need to divide by the multiplyer, so Y=184hp then,

184/.87=211.5

The difference seems minor, but it compounds as the hp rises.
So I was off by 3hp. I was doing this all in my head. Math boy.
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Old 09-17-2007, 06:32 PM   #17
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and figuring 30% to get crank HP is crazy. The dyno must be very poorly calculated or poorly run. 30% loss would have had my car at 300 crank hp before any tune, with 15psi on a t25 turbo.

No way.

Quote:
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So I was off by 3hp. I was doing this all in my head. Math boy.
OK, be that way Mr. Poopie Pants.
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Old 09-17-2007, 06:34 PM   #18
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Deek I talked with Jak about it.
And how did Jak arrive at this conclusion?

I'm not doubting the numbers, I don't care about the numbers... I'm just wondering how it's figured out-- call it my curious side.
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Old 09-17-2007, 06:34 PM   #19
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Deek I talked with Jak about it.



Topher I don't know what seems to be your thing tonight man. I had a baseline done on a dynojet up at SOC and I know based on having driven with Jak's software for a week over the past couple days before dynoing that something isn't right with the dyno read out but the A/F is right and that was the most important thing I needed to find out for Jak. I'll be down at Nicks shop in October and I know I'll get accurate readings for certain.
I am not beefing with you. I am trying to understand. Promise.

And a baseline on a DIFFERENT dyno, does not equate to a baseline.

A baseline HAS to be done on the same dyno in similar conditions.

Think of it this way, you can't weigh yourself on two different scales that are calibrated differently. Make sense?

Edit: or at least the same BRAND dyno.
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Old 09-17-2007, 06:34 PM   #20
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I know Topher. Hence the get together at Nicks. The other 30% is what they said to correct by and that is the ratio setup (albeit with Jaks correction added) that I was given.

Again the a/f ratio is what is good which is the best part of today. True numbers later.



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