tomcat

Hey Steve: We need some new blood in the Tech section and appreciate your viewpoint. I wouldn't want you to worry too much about offending anyone. Lively discussion makes it interesting and many will learn from the debate.

There is another tool that is getting a lot of attention these days and that is engine simulation software. It is becoming more common for engine builders to build your engine in the computer first for discussion of the combination with you. You think you can make a dyno say anything, play with one of these programs without knowing what you are inputting and watch the big numbers start flying around.

BUT...if you are very careful and input only measured head flow, cam profiles etc. and compare your results against real dyno results you can build a realistic model of an engine. The real advantage of such a model is being able to make changes and learn from the model's response whether you are headed in the right direction. Properly used this tool can save time and money by eliminating some of the trial and error.

I recently started working with Engine Analyzer Pro. You can download a free fully functional demo for 10 days from Pro Trends. Your best use of time for this short period is to enter a well known engine combination and get it predicting the correct known HP. Then start changing heads and cams and watch what happens. At the least it is very educational.

stevesxm

i had heard of that but have never seen it... my understanding is that it uses the same computational thermodynamics model that nasa came up with and , if so , am sure its a hell of a tool. you have to know that that software has been in use by the japanese for years in the bike industry.... now there are beautifuuly thought out and executed motors... street bikes from the factory w/ 11.5 to 1 compression running on 87 octane because the heads and combustion chambers are so good...

GPM

TC, where would I find Pro Trend, just curious what it would say about my combo.

Monkey Spanker

Have any of you, or do you know anyone, who has dyno'd a motor with dyno headers VS a wet flow IMCO thumper or EDDIE Marine Thunder type of system? I would only suspect about 20 hp difference considering that there can't be too much back pressure with 4" exausts.

tomcat

Sorry, it's Performance Trends; here is the web page.

http://www.performancetrends.com/Eng...r_Pro_v3.3.htm

GPM: For centrifugal systems you need to enter flow vs. pressure drop data for the intercooler piping. You can do this using the restrictor plate function. I had this number because I flow tested those parts. The program also asks for pressure drop across the intercooler core, data that I had from the manufacturer. You also need to make an educated guess about your operating point (flow, pressure, RPM and efficiency) on the compressor map.

You may not have all this data, but you have actual dyno numbers, so you can build the engine and play with those entries until intake manifold boost and HP agree with reality.

It's not so much that you run the program to see how it agrees with your dyno numbers. You use the dyno results to "calibrate" the model, then you can try different ideas on the model.

P.S. Take a look at the predictions for compressor HP.

GPM

Thanks TC.

RichardCranium572

Pressure drop varies depending on the acceleration rate of the engine.

Actually, depends on alot of factors, but, that is one that will be most noticed on dyno pulls.

Raylar

I can honestly say that I am amazed at how much emphasis is put on "dyno numbers" in the performance industry. In performance boating it should be obvious that engine power, ie horsepower and torque is only a part of the equation. When it comes to boats, the whole list is a long one.
1. Hull weight
2. Hull form
3. Wetted surface configuration
4. Center of Gravity
5. prop speed
6. Prop type
7. X-dimension
8. Steps
9. Ventilation
10. Hooks and such
11. drive ratio
12. beam
13. water type
14. water temp
15. air temp
16. humidity
17. altitude
18. load
19. fuel temp
20. driver skills
21. wind and direction
22. current and direction
23. driveline losses
24. bottom finish
25. etc.
26. etc.
27. etc.
One can see that with all of the states and conditions that can affect a boats performance, an engine alone will not get it done! Dynos are great ways to test a motors output when operated to calibrated SAE standards and output values corrected properly, however the end result of how a motor performs in a boat is subjected to so many variables that one must be very careful to compare any two boats performance levels unless they are identical and in identical condtuions and states. Confusing and sometimes frustrating, there will never be a perfect boat motor, we just have to keep testing and trying!

The need for Speed! Its Magic !!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ray @ Raylar

tomcat

[QUOTE=RichardCranium572]Pressure drop varies depending on the acceleration rate of the engine.QUOTE]

I have heard this before but what does it mean? Just talking about air intake piping, not intake manifolds where all sorts of things are going on. If an air intake pipe/ filter/ intercooler/whatever flows a certain amount of air at a given pressure drop then it will flow twice that amount at roughly four times the pressure drop. Granted we measure these things at steady state on a flow bench, but why would the result be different if the pipe was on an engine that accelerated from flow1 to flow2 at different rates?

Pat McPherson

Great Thread...
I am about to start building my 4th BBC so I am most definitely a rookie.
Debates like this a vary informative, keep them coming...