I am curious if anyone has run comparasions of their engines on the DD2000 and on a real dyno? what were the results... The reason why I am asking is the numbers it came up with for my block were a bit higher than I expected.
Also how about the RPM range on DD2000, does it seem very accurate for anyone else. I ran a couple cars which I know the outputs of already and DD200 was extreemly accurate down to the peak RPM and everything. I just don't want to get my hopes up if the same does not turn out for my vett.

 

I've run a few friends boat motors through it and find it pretty good (+/- 5-10 HP) IF you have the actual head flow numbers. If you get "optomistic" about how well stock or slightly modified heads flow and use one of their canned "ported" head options you can get quite optomistic results. I think their RPM for peak power may be a little high, at least for my BBC boat motors.

-Greg

 

This is an interesting post. I've always heard DD2000 is fairly close, but a little on the optimistic side. The torque and power curves, (not peaks) are supposed to be right on. It would be cool if you took a known quantity that had already been dyno'd and ran a comparison. :yesnod:

I know what you mean about getting your hopes up, I've got a motor sitting on a stand in my garage that DD shows to be a little over 500# torque and a little under 500 HP.........and this is with a mild emissions compliant cam! I'd be ecstatic if that were true!!!!! It looks like I'll find out next year :D

 

I think it's a little optimistic and the level of detail isn't that high. Engine Analyzer by Performance Trends is a much more elaborate program.

Marck

 

When I initially built my NA SBC 427, I used DD2000 to run iterations for cam specs, etc. It was amazingly accurate, within 1-2% across the rpm range.

However, neither DD2000 or Engine Analyzer Pro was very accurate for the turbo setup.

Here's a comparison of DD2000 vs. actual real world Superflow engine dyno results for my NA SBC 427...





[Modified by Monty, 10:30 AM 12/4/2002]

 

Monty, thanks for posting that info! That's great news for those of us that are planning motors and want to play around with flow rates and cams to optimize our setups for our particular needs.
It just amazes me that guys will spend thousands of dollars on combos that aren't "quite right" for each other, yet don't spend the 40 bucks or so to plan with these programs and eliminate potential conflicts. A great example of this is my motor. I got a combo I liked real well, then plugged in lift #s with 1.6 rockers thinking I'd improve across the board........... My numbers actually went down a bit!!! :eek: I don't know exactly why that happened, but I'm pretty darn sure I've saved myself some disappointment because of the DD2000 program!!!!!
And, I can't sign off without thanking GKULL for all the time and patience he's given me in this project.......George, you're amazing :cheers:

 

See my reply to this thread: http://forums.corvetteforum.com/zerothread?id=355719

 

I've found DD2000 to be quite accurate on top end power, but a bit optimistic on peak and low end torque. Of course, your input is critical, so having good
data for head flow, inlet and exhaust restriction, and accurate valve timing data is critical.

DD2000 and most other simulation programs cannot account for air and fuel distribution problems, which can seriously affect actual engine output partcularly with big carburetors and manifolds. Modern EFI systems have much better air and fuel distribution than carburetors, but how close you are to predicted output has a lot to do with how well you can do the final fuel and spark map tuning.

DD2000 also assumes ideal timing, fuel-air ratio, and no detonation. EA predicts detonation and retards timing as necessary, which reduces output, but its detonation predictions seem overly conservative, and the feature can't be disabled.

For 50 bucks DD2000 is a excellent system engineering tool that will allow you to develop a suitable torque curve for your application. If you just pick a peak horsepower number out of the air and bolt on a set of components to achieve this without paying attention to the entire rev range from off idle to peak revs, you probably won't end up with a very good engine.

My basic requirement for a street high performance engine is to have the 80 percent torque bandwidth begin at no more than 2000 revs, and this is primarily achieved via judicious valve timing selection. The top end of the 80 percent torque bandwidth and peak power is then a function of heads or head work and minimizing the inlet and exhaust restriction, which basically boils down to how much you have to spend.

Regarding valve timing selection, unless you are running headers and a very low restriction exhaust system, most aftermarket cams have too much overlap. With manifolds and a street exhaust system too much overlap will kill the low end without adding much on top.

Duke




[Modified by SWCDuke, 10:10 AM 12/4/2002]

 

Caboboy,

Just be cautious, don't put all of your confidence in what DD2000 predicts, it's jsut a guideline. Common sense and previous experience should still be a key component in your decision making process. My example is probably a best case example, and I had alot more detail in terms of actual flow data for my heads and intake than most people do. I also am using some components which most people don't use that probably had a significant impact on the engine being as efficient as it is - i.e. sheetmetal intake, custom stepped headers, etc. Additionally, I went through 4 different cams on the dyno in an attempt to optimize and maximize performance.

Some of the cam specs that DD2000 suggested as a result of it's iterations were pretty goofy. I ended up trying one of them and it did make the pwoer/torque DD2000 predicted but it was hardly optimal compared to the subsequent cams I tried and ended up with. In the end, good 'ole common sense and previous experience proved to be superior and I gained hp and tq at every rpm point as a result of it.

Even though I have had good success with the simulation programs, I still think they are better at showing trends rather than predicting absolute numbers.


[Modified by Monty, 12:31 PM 12/4/2002]

 

A quirk I found wiith DD2000 is how it reacts to changes in stroke. If I increase my 327's stroke from 3.25 to 3.48 with no other changes, peak hp actually drops. Increasing stroke to 3.75 drops peak hp even more. As you'd expect, the hp peak comes in at a lower rpm and low-mid rpm torque is increased with the larger cubes.

 

Cheap filling and emptying models arent really that accurate...

Sometimes they are.. sometimes I've seen results like Monty.. but put in what specs you can for a 5L trans-am engine and it's been over 100hp off.. thats a pretty large error.

I just flat out dislike DDyno2k.. it doesnt even have generic compensations for different types of rings/accessories etc.

Sometimes it works, sometimes it gets close, and sometimes its way off. Depends on how "extreme" youre going it seems, so for most people its probably reasonable :). YMMV as always.

-Phil

 

Okay here is a question, I would think that if you have 2 turbos that say flow 300 CFM each, then you would put 600 CFM in the flow rate on the dyno. Only problem is, when I do this the power drops dramatically when compared to how it would be if it were to be at 300cfm. Can anyone explain this?


[Modified by WashingtonRacer, 2:13 AM 12/5/2002]

 

I found the same thing, DD2000 was worthless in predicting my turbo setup.. Engine Analyzer Pro was just as bad, even with all the minutea detail accurately entered. I don't think they've got their programs really setup to address forced induction very well. For instance, each one of my turbos is rated at 1000 or so cfm, but DD2000 won't even allow you enter in a flow number larger than 1000 cfm. Actually, the smaller the flow number, the more power DD2000 predicts which inverse to what it should be unless I am totally misunderstanding what DD2000 is looking for in that field.

 

This is not a quirk, but a characteristic of IC engines. Take similar engines - everything the same except stroke - a 302, 327, 350, and 383 - same heads cam, CR, inlet and exhaust system. You will find either in the simulation or the real world that all three will produce about the same peak power, and it will occur at the same mean piston speed, which means lower revs as the stroke increases.

With optimized gearing all three would make about the same top speed in a given car, but the larger displacement engines would accelerate faster because they produce more AVERAGE power over the operating range, which is established by gear spacing, and this is why the old adage "you can beat cubic inch displacement" is true.

Duke

 

Duke, as you stated, average power does increase but the part that I question is that it shows a loss of peak power despite the displacement increase. As expected, volumetric efficiency goes up as displacement goes down but I can't buy that an engine looses peak power as it's displacement is increased. Yes, the peak will likely be at a lower rpm but it should still be a higher number.

 

I went back and looked at my '63 L-76 -.030" over, LT-1 cam, and pocket ported 461s with stock 1.94"/1.5" valves, 10.75 CR, 550 CFM AFB, HP manifolds and mufflers. Peak predicted power is 346@6000 and rolls off to 330@6500. I increased the stroke to 3.75" and peak power was 347@5000 with a "flat peak" - 346@5500, rolling off to 331@6000, so the peak is essentially the same. Of course, the 383 has a much fatter torque curve, which would be nice since I have a CR four-speed and 3.08 axle. If I had to do it over again I would definitely go stroker, and it can't be detected!!!

You didn't specify any examples, but if the peak power for different stokes, - everything else the same - is within two percent, you can essentially assume for all practical purposes that it IS the same since two percent is within the error range of the simulation program.

Duke

 

Duke, in my simulation the difference is well under 2% (407hp @ 6,000 w/331ci, 400hp @ 5,500 w/383ci) but I still don't accept that peak power would be less if measured on an actual dyno.

Another quirk I found was with carb size. That 407hp with a 700 cfm carb jumps to 418hp at the same rpm with an 1100 cfm carb and no other changes. It also shows a power increase throughout the entire range, even at 2,000 rpm. I'm not dissing DTD. I think it's a valuable tool for comparing possibilities and the effects of modifications but I also accept that it's not capable of accurately interpreting all changes.

 

Your right, Leaving DD2000 as a helper is the best way to go. It's too bad that they hav not set up the Turbo options for it. Since that is still a rather important step in the building process, So many different trim designs, it's really hard to figure what is best for your block... unless you want to spend the countless hours figuring efficnecy rates, thermal rates, block flow rates, turbo flow rates, pressure density and ratio.... Ughh.. luckly enough people have done this already. The worst part is that they even have a Speed option in the induction portion of the setup. Yet what is one of the main kind of force inductors that really have their own speed variable?? TURBOS and they don't even have the option available. I don't even know if the option works, perhaps they were working on it then just pushed the program to release date and forgot to finish it. Who knows, anyways according to my setup I should be able to make 1043hp at 75k rpm. thats at 450 cfm to4b v4 trim turbo. Now since there are 2 turbos you would think I would have 900cfm right? well when you plug in that number the power drops to 896hp at 75k. Kinda strange don't you think. Either way I am pretty sure I will be happy with the results, since I have already built the motor and ran it once, And it did pull like crazy. Only got a few runs in, then I shattered my trans. Some may remember that. Since then I have decided to replace the cam, which required springs, which required me to machine out the heads, so I just got some new heads instead, then I thought what they hey, why not a new bottom end too, It just never ends does it!!! But you might as well get all the fun in while you can.

 

The problem I see with DD2000 is that you can enter both the advertised specs and the @.050 cam specs using the manufactures cam cards, and the results are completely different. The DD2000 help file says to use advertised duration, because it's more accurate in DD2000 and because DD2000 converts @.050 specs to advertised anyway. :confused: Apparently it doesn't convert from @.050 specs to advertised too well for the cams I've looked at.

When I found a cam that I liked I first ran it with the @.050 specs, and the HP/TQ curve is shifted lower with lower peaks. Then I ran it using advertised specs, and the HP/TQ curve is shifted higher with higher peaks. The TQ numbers at 2000 RPM were as much as 20% different, and the RPM scale was shifted around 1000 RPM higher. For most who are building for max HP this is not an issue when using DD2000. You just keep entering cams until you find the one with the highest output. It's a good comparitive tool.

For me....I want to design my engine to produce a TQ figure of around 380 lb./ft. at 2000 RPM, and with as much peak HP as possible based on TQ. Depending on which cam specs (adv. or @.050) I chose to enter into DD2000 for a particular cam could mean the difference between choosing the right cam, or one that is too small. Which is the most accurate way? I would think @.050 specs should be more accurate since not much is happening below that lift, but according to DD2000 and others that I've spoken with DD2000 needs the advertised duration to be accurate.

mark

 

For Caboboy and 81vette for their 415 or so ci motors I came out with two roller cams to look at in dd2000 ones has greater TQ than hp.

Use Dart 227 cc flow files from their site. 2.08/1.6 10.8 c/r I used single plane 750 cfm. just under .600 lift I & E

intake at .050: -2 , 52 or 54
ex @ .050 : 47 , 12

This has max TQ at 4500-5000 and max hp at 6000-6500

i at .050: 8, 42
e : 56, 2

TQ monster max at 4000 and max hp at 5500

--------------------------------------------------------------------

What so deceiving about both is: they both have about 230/238 duration and 112 lc with 10 degrees of over lap, but the cam event timing radically changes their behavor. So seat to seat advertised imput numbers would not even come close. Tell me what you think :cheers:


[Modified by gkull, 10:08 AM 12/6/2002]