Desktop Dyno Software

[jsup]

OK, I have a question......

Seems that Desktop Dyno takes into consideration flow numbers to ascertain HP results.

Now, Dart holds the position, which I agree, that flow numbers don't tell the whole story, that design has more to do with it.

So I have to ask.....is it not expected that heads that put up big flow numbers, regardless of the quality of that flow, will always post higher numbers on a desktop dyno.

What is the response to a desktop dyno that shows higher numbers for one head over another just based on flow number?

Thanks

[lun40119]

I have dynoed my last three combinations and desktop dyno wasnt even close to the real world dyno. It also missed on the 502. It has kind of made me a non-believer.

That being said, even real dynos can be off. I am sure of this, because I am not making the power in the car at the track that the engine made in the dyno cell. Think about it, on the dyno it is a controled enviroment with cool air, no air cleaner, no exhaust. In the car the hood is closed, under hood temps are through the roof. I am not saying that dyno's are bad, I dyno my stuff every year, but getting the car to perform at the track like it does on the dyno is a different story.

My theory on the heads that make the big numbers is this. I am more concerned with the low and mid lift numbers. Think about it this way. You are at max lift on your camshaft once. You are at all other points twice.

[jsup]

Here's the information as presented.

Does anyone really believe there's 50 HP between them?


Originally Posted by some guy
Changed heads to Dart Pro One 227 Ported, all else the same...
RPM HP TQ
2000 164 432
2500 220 461
3000 279 488
3500 353 530
4000 433 569
4500 508 593
5000 572 601
5500 615 587
6000 637 558
6500 638 515
7000 621 466
7500 585 409

Bringing AXX heads here for comparison...

RPM HP TQ
2000 163 428
2500 217 457
3000 275 481
3500 348 523
4000 429 563
4500 512 597
5000 581 610
5500 627 600
6000 658 576
6500 661 534
7000 655 492
7500 634 444

Going to dinner now, will Sim the Dart 230's later

[Dart Vader]

Simulation software has it's place and can be useful at times, but the algorithms aren't perfect. The people who actually build engines all the time know better than to rely on software like this for anything other than preliminary testing.

[jsup]

OK, then how accurate do you think the 50HP difference is? I guess the question is what's the response? Someone lays that down and says "SEE XXX heads make a lot more power"....I hate those people.....:D

[Dart Vader]

OK, then how accurate do you think the 50HP difference is? I guess the question is what's the response? Someone lays that down and says "SEE XXX heads make a lot more power"....I hate those people.....:D
My response would be to cease reading and posting on the forum where this data was posted.

[lun40119]

I am probably biased, but I do notice, when I am at car shows I see alot of sbc's with XXX's, but when I am at the DragStrip I don't see much of them.

[jsup]

My response would be to cease reading and posting on the forum where this data was posted.

HA! I should probably do less of that in general! Yeah, I know. It's my Don Quixote condition. I have a hard time letting BS stand. I can't help but think BS is being passed around as fact and kids are spending hard earned money on it.

It's my disease, I probably need help!!:D:D:D

[jsup]

I am probably biased, but I do notice, when I am at car shows I see alot of sbc's with XXX's, but when I am at the DragStrip I don't see much of them.

I've made that point......

[Dart Vader]

HA! I should probably do less of that in general!
:p
There isn't really any point in debating if you're the only one debating. It's only a debate if both sides are willing to change their opinions when presented with compelling evidence.

Otherwise, it's just an argument, which is a waste of everyone's time. If someone really wants to know how flow numbers play into the equation, have them read the article by Reher Morrison I posted in our news section. I'm pretty sure he might have an idea what he's talking about.

[lun40119]

Ask them if they can ride thier flowbench down the track. :D:D:D

[jsup]

:p
There isn't really any point in debating if you're the only one debating. It's only a debate if both sides are willing to change their opinions when presented with compelling evidence.

Otherwise, it's just an argument, which is a waste of everyone's time. If someone really wants to know how flow numbers play into the equation, have them read the article by Reher Morrison I posted in our news section. I'm pretty sure he might have an idea what he's talking about.


I'll go look, thanks.

[Trmnatr]

Ahhh,,,,,,,

Could you see that, pull your Chevelle up and in the right lan a guy riding a flow bench :eek::D

[jsup]

OK, I'm an idiot. Where exactly is the article I'm looking for?

Thanks

[lun40119]

Here you go...........

http://www.dartheads.com/news_article_view.php?nak=49

[Awesome Bill]

We on the other hand have a real dyno with pretty good equipment for measuring real power. I also have the Desk top dyno right on my screen that I can compare when testing. What I have found is when we actually put the very close flow #'s in instead of pick one of the following, it is pretty close.

What happens is when the actual real dyno testing is done, you have to have the proper fuel for compression, fuel flow, air flow and the right a/f ratio to make the real engine be in line with the desk top. The desk top will be very close but you can not test the desk top conditions you actually have with your real engine of you do not have the real conditions right. Believe me, they are very close but both are considered junk if you don't know how to use them or can't back either up.

With conditions being correct as I have laid out, and timing is not the best power maker when dyno testing. When you get pretty close, within 2°, the power gains or loss are not that much being 1-2°'s off. What we find makes the most power is proper size of head, a/f ratio, proper fuel and timing for actual static compression, and just common sense. John from Jomar just sent me 10 spacers to dyno. I told him I have really not found spacers do that much if anything. He said he had worked on these with a leading engine builder which I have great respect for and surely knows just as much if not more than I do, and I told him I would run them.

Well I will be one to tell you that most of the time we see none to 3hp with most spacers, even the cnc'd ones, but I took a 582BBC @ 1015 hp after extensive dyno work and we installed the Power Cone Spacer and the first pull was 1020hp with 10 more ftlbs of torque. This was a back to back test. I was impressed with the hp but the torque was more impressive.

This was a 582 with a very nice set of heads and a Profiler Sniper Manifold which already has 1" of spacer on it. So some things are good and JOHN'S POWER CONE ACTUALLY WORKS. But if I did not have the fuel trim, timing, etc correct, the spacer most likely would of done nothing or very little. So without both dyno testing conditions being to what they are supposed to be, you can have a football field condition wide between the both.

Air flow means nothing when most cases the head is to big. I would rather have a 330cc head flowing 400cfm @ .800 than a 355cc head flowing 409 @ .850 on a 540 any day. Volume with out air speed is a weak slow air flow and will only get into moving air quick enough at very high rpms. Look at pro stock or comp elim.

So both are o.k. but the driver has to have everything in ideal or close to being right conditions to make both testing for real. What I have seen are cams way to big, heads to big, carbs big, and the whole big deal really hurts engines. Engines like conservative, they work better. John and Skip @ DAMBEST has told me that many times and I have learned that from just years of playing. Especially with BBC engines under 500ci. I only use 300-310ccs of good flowing heads and make very good power. The larger heads kill the engine. If I use epoxy to put them back to the smaller size for air speed just proves I did not know what I was doing or was sold these heads by the person on the phone with those particular size head and needed to move the. Seen if 1000 times.