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EngMod2T software - who else uses it??

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I just bought the EndMod2T software after thinking about it for about a year... very happy that i finally took the plunge! I already have TSR, Bimotion and a few other smaller programs but EngMod2T is at another level.

I found it very easy to understand and entering key measurements wasnt really any harder than other programs... other than the fact its much more detailed!

First of all i decided to model my 2007 CR250 which is claimed to have max output of 53 hp at 8300rpm with a very large mid range hit... this is the result of what Engmod2T predicted for the stock engine with a PC Works pipe and R304 shorty...

CR250poweroutput.jpg

Im pretty happy with the results... they pretty well match the claimed power output so i guess ive measured everything ok.

This one is the pressure trace at 8500rpm, just beyond peak power... you can see that as the transfers open (TPO) pressure in the cylinder is greater than in the transfers so they experience a reverse pressure spike, hence the reason power begins to drop at this point.

CR250_stockpressuretraces.jpg

So who else uses this software??? Id be interested in sharing files for common components or engines... things like carbs, pipes, etc. Im happy to model whatever i can get my hands on and swap the data files for others if anyones interested.

Dave

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Dave,

I don't have any other programs, but with engmod2t maybe I won't need them. :thumbsup:

Your results look great! I'm certainly no expert, but it looks to me like the boost ports may be stealing flow from the main transfers (maybe widen the mains?), and also that faster blowdown (raised and/or wider EP, different pipe w/more aggressive initial flare from the manifold, etc.) might reduce that reverse pressure in the transfers and possibly result in more power.

If you're willing to share your CR files, I'd love to have them. I've had several requests for advice about the case-reed CR motors, but haven't been able to help too much so far. I'll gladly share what I have, which unfortunately isn't much (Honda MR175 motor, 28/30/34mm carbs, pipes).

Speaking of which... here are my power results and 8,500 rpm pressure traces. Obviously this motor is a wimp compared to yours, but for a vintage piston-port 175 it's not too bad, and I'm real happy with the 'stretch' pipe, which trades a strong initial blowdown for the extended suction needed with undersized transfers:

H-TRun142final83-119.jpg

Run145PressureTraces.jpg

Ray

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Ray,

Im happy to share what i have done so far for the stock engine... just let me double check a few measurements... things like the intake correction factor, etc, just want to remeasure to make sure they are right.

The pressure trace above is for 8500rpm, however the lower traces, around 7500-8000 show the transfers flowing nicely at TPO, obviously at 8500 rpm things start going wrong, hence the reason why power drops off. Ill definitely play with modelling some of the changes you suggested to see if i can theoretically get better over-rev.

Ive started to model my modified cylinder as well and so far it shows good gains across the board from 4000 up to 8000, from there is signs off earlier than stock, which is exactly what my bum dyno feels too. Yet to add things like the boyesen rad valve and keihin carb but should get that done in the next couple of days. Then itll be interesting to plot the stock curve against my current setup and see if it reflects what i feel on the bike. Its exciting to be able to model all of this stuff and im very impressed with the accuracy of what the software predicts.

Im also going to play with altering the opening time and height of the powervalve to see what happens. I think there will be gains to be had in the mid range by doing this.

Ray, send me your email address and ill forward some files in the next few days.

Dave.

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Dave,

Thanks much for the offer of the CR files. I know how much work went into them. :thumbsup:

Without any previous experience with these kinds of programs I had a pretty steep learning curve, and was correcting motor data pretty much continuously for the first 3 months, less frequently after that. One thing that reached up and bit me recently was the transfer port/passage ratio, which has to be changed every time the TP windows are resized. I couldn't figure out why the crankcase compression ratio kept changing, which was because I was making TP changes without updating the TP ratio.

It is super cool to be able to try things out without cutting or spending money, especially when you have confidence the results are accurate. It must also be great to have a modern motor with so many convenient tweaks available (power valve, ignition maps, reeds, etc.).

It seemed that in my motor at least, the "conventional top-end boosters" (bigger carb, better intake/TP flow, shorter pipe) almost always resulted in better over-rev, but rarely in more peak power. The main peak-power booster turned out to be a taller/wider EP (improved over-rev) and longer pipe (considerably decreased over-rev).

Ray

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Looks very interesting. I am a long time TSR user , maybe it is time to switch over since TSR is no longer around.

I wonder how the power output graph would look compared to my dyno? Probably different due to the loss in the transmission. You software is probably giving you HP at the crank .

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You software is probably giving you HP at the crank.

Yes. It's possible to simulate gearbox and final drive losses with the user-defined friction loss modeler, but with no numbers to enter I left it as is.

Ray

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Dave,

One thing that reached up and bit me recently was the transfer port/passage ratio, which has to be changed every time the TP windows are resized.

Thanks for the tip!! I would have overlooked that initially.

How did you measure the transfer intake windows?? I just held graph paper over them and rubbed around the edges to give a rough marking on the graph paper, then just counted the squares to give me an area in mm2... crude but should work. The CR transfer ratio was around 1.6-1.7 for the main and aux transfers. The boost was close enough to 1.0.

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How did you measure the transfer intake windows??

On the MR motor these are vertical and almost perfectly rectangular, with about half above the base gasket surface and half below. I measured them with calipers and multiplied, then measured the relative widths of the main and rear transfer tunnels and figured out the area split. I went by the diagrams in the 'Create New Transfer Ports' section of the Help files.

Maybe on modern motors the ratio is fairly close to the "typically 1.2" mentioned in Help, but on mine it was nearly 3.8 (huge entry window area, tiny transfer ports). The other engmod motor models run from 1.0 (!) to 1.4.

To measure the passage length (@ 70mm), I used a plastic-covered metal tie like those used for stereo cables and garbage bags, shaping it roughly to the center of the passage.

Ray

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really want to get the engmod2t but $400 is alot of dough. atleast i think its $400 ?? im assuming its a complete package for calculating parameters of the entire engine ( dome cc, squish, msv,- porting durations, shapes, angle, areas- crank case compressions- reed valve- pipe design- ?) wondering if anyone might have a few screen shots of the program in action ? also wondering, since it calculates the optimum exh port height, area etc, does it also give you the shape so you can apply the info directly to your engine ? or would you have to create your own shape, based on the total area given ? is there anything it cant do that you wished it could ? sorry for a bunch of questions but i want to know as much about this program as possible before dropping that much coin. was somewhat confused on where to purchase the engmod2t, got any links or advice ?

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really want to get the engmod2t but $400 is alot of dough. atleast i think its $400 ?? im assuming its a complete package for calculating parameters of the entire engine ( dome cc, squish, msv,- porting durations, shapes, angle, areas- crank case compressions- reed valve- pipe design- ?) wondering if anyone might have a few screen shots of the program in action ? also wondering, since it calculates the optimum exh port height, area etc, does it also give you the shape so you can apply the info directly to your engine ? or would you have to create your own shape, based on the total area given ? is there anything it cant do that you wished it could ? sorry for a bunch of questions but i want to know as much about this program as possible before dropping that much coin. was somewhat confused on where to purchase the engmod2t, got any links or advice ?

It's a complete package for simulating the entire engine, and for such it actually cheap, although a lot of money.

The software does not calculate the optimum exhaust port. It's the users responibility to test different ports, pipes etc.

Dat2T (the preprocessor) does however calculate STA wich you can use to get in the ballpark without running a full simulation.

You can buy the software from Neels, check the link I posted above for contact details.

Beware though, you might find yourself spending too much time infront of the simulator screen than you'd wish for :bonk:

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I have this software. If you see all the functions that include, and the excelent customer service given by the author Neels Van Niekerk, the software is cheap. I bought the package in 2009 and it helped me a lot to tune my CR500, YZ250, YZ125 and little scooter Minarelli engines and I have the measurements in EngMod2t for all.

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