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Discussion Starter · #1 ·
A friend of mine ran my combo through desktop dyno, after I gave him a detailed list of my engine specs. It says I'm making 407hp(flywheel) at 6500 and 369 ft/lbs of torque at 5000. I thought that was odd because my XE cam is supposed to be only good up to 5700. Is this possible?

Then, just for fun, he ran the same combo with a Victor Jr. intake and it made 458hp(flwheel) at 6500 and 397 ft.lbs at 5500.
That an extra 50hp with just an intake swap! Although, it did show a drop in power/torque in the low ranges until about 4K
I know the program is only supposed to be a reference but how much can it be relied upon?


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1982 GT
351w(.060), ported & polished heads with 1.94/1.60 valves, 10.5 comp, stealth intake, 274XE cam, Holley 750, Mallory dist., shorty headers, flowmasters, 4:10 gear, c-4 with 2500 converter, subframes, electric fan

<font size=-1>[ This Message was edited by: admin on 3/17/06 1:09am ]</font>
 

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Never mind whether the HP numbers are accurate or not. Use the dyno as a baseline to compare cams, intakes, valves and flow data,etc,etc.
 

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It's not as accurate as other programs like Engine Analyzer, but it's more accurate that blind guessing, and like was said before, is useful for comparing different camshafts, etc... It's hard to compare intakes because it only has "dual plane", "single plane", etc... it doesn't have specifics like Performer vs Performer RPM, it just has a basic profile. Also I've found that you need extremely accurate cylinder head flow numbers to get accurate numbers out of it. If you just guess at the head flow or pick one of the built-in head types, it can easily be over 50hp off. Also with cylinder heads, it doesn't take into account the effect of having too big of cylinder heads (port volume). For instance if you put the flow numbers for AFR225s in compared to AFR165s on an otherwise stock engine, it will say the 225s made more power through the entire RPM range which is probably not true in real life. The program can only be as accurate as the data you are feeding it, and it requires at least some knowledge as to what actually works for a combo and what doesn't.
 

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Can't weigh-in on the accuracy of software simulation, but I can tell you that I'm running the same cam in my 351W w/ Comp Cams Pro-Magnum lifters @ minimal lash. Combination is in my sig.
Comp Cams catalog <U>generically</U> lists the usable power band as 1800-6000 rpm's. And that's <U>probably</U> based around a SB Shivvy. In my particular case, judging by the exhaust note, it doesn't <U>really</U> smooth out till 1800-2000 rpm's.... but it REALLY starts to scream (and I DO mean SCREAM
) around 3000 rpm's. Haven't had it on a chassis dyno yet to baseline it/plot the curve, and I haven't actually tried to find where it noses over, but I <U>have</U> had it to 6300+ and it was still pulling. So I wouldn't place a great deal of stock in the whole 5700 rpm notion.
Also, the motor originally came with a VicJr on it, but I shelved that in favor of an AirGap intake. I have a stronger bottom end, and I can't say I've lost anything noticeable on the top end.
With all that said, 425+/- hp doesn't sound unreasonable.

Kevin
 

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Not very accurate, but fun to play with. The proof is on the track and in the real performance

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1991 LX Mustang 347 C4 combo Mid 11's with the AC on.
1984 Mustang GT 460, Powerglide "Still putting it together" hoping for 9's !!

<font size=-1>[ This Message was edited by: dfree383 on 3/16/06 2:47am ]</font>
 

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DD suffers from too few parameter entries and too many assumptions. EA 3.0 is better and has many more data entries. This can result in two things... it can be more accurate if the data is accurate or it is more prone to error than DD if you "guess". Both programs are only as good as the accuracy of the data entered.

For example, EA 3.0 allows exhaust muffler flow data to be entered. I used dynomax's flow data for the mufflers I purchased and entered all the other 331 engine data and it estimated 388 HP @ 6300 and 398 TQ @ 4500 SAE corrected. The last chassis dyno was 335 RHWP and 337 RWTQ SAE corrected. Using a 15% drivetrain loss factor...another estimate I know, but a reasonable one...it translates to 394 FWHP (peak was also at 6300 by the way) and 396 RWTQ...Thats pretty darn close.

Like someone else said, it's a valuable tool to help make engine design decisions.

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Tracy Blackford: Corona, Ca
'65 FB Mustang 331 with 282S cam, fully preped 351W heads. T5z and 3.50 9" posi. 335 [email protected] RPM




<font size=-1>[ This Message was edited by: blkfrd on 3/17/06 12:10am ]</font>
 

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Discussion Starter · #10 ·
Maybe it wasn't desktop dyno and was another program because he asked me for my cam card specs. Judging from the replies here, desktop dyno doesn't allow for that kind of detail.
 

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The biggest mistake made with Desktop Dyno is not correctly detailing your flow settings. And it makes a BIG differance in the output.
The defaults are only averages. Try setting the program up accuratly and then you may surprised just how accurate it is.
 

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Ugh!

Here's my take lol.

Desktop Dyno 2000 can be incredibly accurate, or just as far off. It also requires some 'guestimation' and intelligence in your parts selection. As stated, AFR 225's would suck monkey butt on a mild cammed 302, but the program won't show that. Usually however with an intelligent choice, it becomes relatively accurate the closer you get to the torque peak, and after. Also, ALL the DD versions will accept cam specs. One last thing regarding DD 2000. Flow numbers are key, however be aware that 90% of flow numbers are inflated, not by cheating, but by flowing over a bore size much larger than your cylinders (as in, 4.125 or 4.155 test bore for a SBF head, when we ALL know 4.030 is much MUCH more realistic) in order to eliminate shrouding. They also flow with rounded clay inlets and other items designed to increase flow. Sometimes this can increase flow numbers by 10% or more. All without 'cheating' the numbers. You see the problem?

As for Engine Analyzer...I can't build a motor where that damn program won't say 'poor mixture quality'. You telling me a 347, Victor Jr heads and intake, 11:1 compression, 284/292 Solid Roller cam, 750 Holley, and 1 3/4 open headers is running with 'poor mixture quality'? Every motor I've made on that program had it (a few of which I built with real parts...and they screamed) lol...so I gave up when the trial ended =p.

That being said, I use DD 2000 to help me choose cam profiles, and that's pretty much it =).

Cris

PS
DD2000 did say my 347 combo would make 540hp...which was a bit over, but DAMN close to the real numbers =).

C



<font size=-1>[ This Message was edited by: Is1BadFord on 3/16/06 11:24am ]</font>
 

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Discussion Starter · #13 ·
Ok then, would you say that my combo below puts out 407hp(flywheel). Does that sound accurate?
Then , by adding a Vic. Jr., it claims it would add another 50hp.

I plugged 407hp into a program called Virtual Engine calculator and it says my car should run [email protected]
That's going to be pretty close after I get my Edge 3700 stall converter in.
 

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On 2006-03-15 08:28, Motorhead wrote:
The program can only be as accurate as the data you are feeding it, and it requires at least some knowledge as to what actually works for a combo and what doesn't.
This is true. I also doubt it takes into account possible valve float above 6k rpm with the hydro cam.

Can't see it being very accurate in this case.
 

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On 2006-03-15 20:36, 82GT wrote:
Ok then, would you say that my combo below puts out 407hp(flywheel). Does that sound accurate?
Then , by adding a Vic. Jr., it claims it would add another 50hp.

I plugged 407hp into a program called Virtual Engine calculator and it says my car should run [email protected]
That's going to be pretty close after I get my Edge 3700 stall converter in.
Although your combination seems well thought out and sound, IMHO, 407 hp would be quite a bit on the high side. I would guestimate you are pushing closer to 350hp.
 

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DD2000 can be right on or way off, I have had some luck looking for flow files on the net then downloading them to my program, as well as cam files..if they aren't already on there. It was however within like 10 horse of my real dyno of my 347!

Chris
 

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On 2006-03-15 20:22, Is1BadFord wrote:
As for Engine Analyzer...I can't build a motor where that damn program won't say 'poor mixture quality'. You telling me a 347, Victor Jr heads and intake, 11:1 compression, 284/292 Solid Roller cam, 750 Holley, and 1 3/4 open headers is running with 'poor mixture quality'? Every motor I've made on that program had it (a few of which I built with real parts...and they screamed) lol...so I gave up when the trial ended =p.
<font size=-1>[ This Message was edited by: Is1BadFord on 3/16/06 11:24am ]</font>
If you look at the actual numbers EA gives you, you will see that at low RPM the "air/fuel mix quality" will be down below 100%. That is because it assumes you have the throttle floored from beginning to end of the graph, so if you tell it to start calculating at 1500rpm or even 2000rpm, if the air/fuel mix quality is low (which it would be in real life with it floored at that RPM), even for only those one or two data points, it tells you. Like is said, it is extremely accurate, like it will tell you that you loose low RPM power with a huge mechanical secondary carb for this exact reason. DD2000 just keeps adding torque through the whole curve the more carb you give it.
 

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On 2006-03-15 22:12, 289nate wrote:

This is true. I also doubt it takes into account possible valve float above 6k rpm with the hydro cam.

Can't see it being very accurate in this case.
You're right, DD2000 doesn't account for valve float, but Engine Analyzer does, and has different valvetrain options (stock, upgraded, full race) and cam profiles (mild/aggressive, solid/hydraulic) to extimate valve float problems, and once it does think you'll have valve float the power drops off sharply.
 

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On 2006-03-15 17:29, 82GT wrote:
Maybe it wasn't desktop dyno and was another program because he asked me for my cam card specs. Judging from the replies here, desktop dyno doesn't allow for that kind of detail.
YES, DD does figure in the camshaft. I have a DD program on my 'puter that I play around with just to see what kind of #s I can get out of a particular combo.
NO, it does not have a very good database of intakes with airflow specs.
 
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