What a drag

[wrench459]

The drag coefficient of the GT is .36.
Anyone have an idea of the CdA?
Just a brain fart while working on some calculations.

[hrcollinsjr]

Originally Posted by wrench459 The drag coefficient of the GT is .36. Anyone have an idea of the CdA? Just a brain fart while working on some calculations.

Looks like you're the man for the job. Surely there is some level ground around there somewhere and with a little luck a calm day. Are you going to remove the mirror(s), windshield wipers and whatever else that might catch air when you run your test?

More can be done with aerodynamics sometimes than hp and it's free MPG, not that you care.

I'll be interested in your results. Please make sure to share them!

Harold

[wrench459]

run file one
Dont look at the A/F its inop on this pull


RunFile_001.drf: 65.91 °F 29.15 in-Hg Humidity: 11 % SAE: 0.99 Average Gear Ratio: 74.52

s RPM x1000 hp ft-lbs Air/Fuel
0.43 2.10 N/A N/A 14.82
0.80 2.20 32.65 77.95 14.85
1.14 2.30 35.48 81.01 14.85
1.48 2.40 37.56 82.19 14.84
1.81 2.50 39.36 82.68 14.85
2.15 2.60 41.32 83.48 14.83
2.47 2.70 43.31 84.26 14.83
2.80 2.80 45.42 85.20 14.82
3.12 2.90 47.90 86.76 14.83
3.44 3.00 50.13 87.76 14.84
3.75 3.10 52.07 88.23 14.85
4.06 3.20 54.46 89.39 14.84
4.37 3.30 56.78 90.37 14.84
4.67 3.40 59.35 91.67 14.84
4.96 3.50 62.63 93.99 14.83
5.25 3.60 64.92 94.71 14.83
5.55 3.70 66.95 95.04 14.84
5.84 3.80 69.46 96.00 14.85
6.12 3.90 71.66 96.50 14.84
6.41 4.00 73.92 97.07 14.84
6.70 4.10 74.48 95.41 14.83
6.99 4.20 76.80 96.04 14.83
7.27 4.30 80.56 98.40 14.84
7.56 4.40 82.58 98.57 14.84
7.84 4.50 83.89 97.91 14.84
8.13 4.60 85.41 97.51 14.83
8.43 4.70 85.44 95.48 14.83
8.73 4.80 85.64 93.71 14.84
9.03 4.90 86.34 92.55 14.84
9.33 5.00 88.36 92.81 14.84
9.64 5.10 90.51 93.21 14.84
9.97 5.20 87.95 88.84 14.84
10.28 5.30 89.23 88.42 14.84
10.61 5.40 89.84 87.38 14.85
10.95 5.50 89.99 85.93 14.83
11.28 5.60 91.95 86.24 14.81
--------- --------- --------- --------- ---------
MAX: 11.28 5.60 91.95 98.57 14.85
MIN: 0.43 2.10 32.65 77.95 14.81

Your right Harold its a never ending quest

[Redskinsjbs]

I just see max Torque at 4400 rpm and max hp at 5600 rpm. What else can you gather from this pile o' points?

[wrench459]

Theres a big hickup starting at 4 grand.
Like the fuel mixture is going lean.
I'll need to dive more deeply into this.
Its not as great as some others I've seen but take a second and look at the torque curve.
Take the whole picture into consideration not just the MAX numbers.

[hrcollinsjr]

Originally Posted by Redskinsjbs I just see max Torque at 4400 rpm and max hp at 5600 rpm. What else can you gather from this pile o' points?

Actually it looks like to me it's pretty much done at 5100 rpm since it drops off and then spikes a little at 5600 rpm.

Dan is this a stock engine? I believe this confirms my conclusion years ago that you might as well shift somewhere between 4500 and 5000 rpm because you're no longer excelerating at the same rate as you were below these numbers.

I'm lost what is the first column?

Question for Gary if he's looking at this thread. Why is my email from this thread subscription easier to read than the post itself?

Harold

[wrench459]

Originally Posted by hrcollinsjr Dan is this a stock engine? Harold

Harold you asked me last month.."When was the last time you worked on a stock motor?"
First column is seconds into the run

It's been a long time like when I was in high school. I know the numbers dont sound right but it is what it is. From the info I'm getting.
95mm King pistons very heavy slugs
reworked stock rods They came out good. I spent some time on those.
One hell of a 1.9 head reworked by "Steve" and yours truly
IE small stem valve head
And some other mods to this and that.

[hrcollinsjr]

Originally Posted by wrench459 I know the numbers dont sound right but it is what it is. From the info I'm getting. 95mm King pistons very heavy slugs reworked stock rods They came out good. I spent some time on those. One hell of a 1.9 head reworked by "Steve" and yours truly IE small stem valve head And some other mods to this and that.

I'm assuming this is rwhp. It's not that bad. I thought maybe you had factored in somehow the drivetrain loss since the figures were close to the old gross hp rating. At dyno days here in TN IIRC the highest rwhp we had was in the low 60's from stock or near stock engines. Percentage wise I'd say you made a nice improvement. I can easily feel a 30+ hp increase in a V8. I would think in a 4 cyl. Opel it would almost feel like doubling the hp.

Harold

[RallyBob]

Originally Posted by wrench459 The drag coefficient of the GT is .36. Anyone have an idea of the CdA? Just a brain fart while working on some calculations.

According to the books I have on the GT, the stock CD of a GT is closer to .393. Still VERY respectable for a car designed in the mid 1960's, and in fact most new cars are only in the realm of .34-.36! Keep in mind that is with all OEM components fitted...mirrors, wipers, lights, etc. I once calculated the frontal area of a GT, but don't recall what it is. I think it's in my notes for my Bonneville project.

For comparison, a Corvette of the same vintage (1968 for example) has a CD of about .49!

[RallyBob]

Originally Posted by wrench459 11.28 5.60 91.95 86.24 14.81

Stock 1971 Opel (with Solex), makes about 47 whp. So you are now making about 95.5% more HP than stock, with no 'trick' parts and a single carburetor. And at a very reasonable rpm, which is a sign of efficiency. If you can raise the HP without drastically raising the peak HP's rpm point, then you are doing it with very good volumetric efficiency. Nice!

[Gary]

Originally Posted by hrcollinsjr Question for Gary if he's looking at this thread. Why is my email from this thread subscription easier to read than the post itself? Harold

Not sure what you mean by that Mr. C.?

[hrcollinsjr]

Originally Posted by Gary Not sure what you mean by that Mr. C.?

My email from this thread showed separate columns not all of it run together as it appears here.

Harold

[Gary]

Do you mean the columns in post 3? What browser & style are you using?

[hrcollinsjr]

Originally Posted by Gary Do you mean the columns in post 3? What browser & style are you using?

Explorer & Linear mode. I'll forward my email to you.

Harold

[Gary]

Originally Posted by hrcollinsjr My email from this thread showed separate columns not all of it run together as it appears here. Harold

Got your email. It's just a difference in the way posts are displayed in the forums verses a text message. The first does not recognize tab spacing.

[wrench459]

Thanks for the kind words Bob. Should we let the cat out of the bag by telling what carb. is on the old girl? Not that anyone would like to have there cake and eat it also.
The one thing that impressed me was the torque.. 80+ lbs almost across the entire rpm range. 90+lbs over a 1800 rpm range.
My goal is 100lbs over 2000 rpms.