TomCat39

Doubt it would work against the volume calculation with the water method.

I was thinking more in line about measuring distance of both, inside and outside radii of the runner assuming the easy way out would be used of measuring on the outside of the intake manifold to get your numbers.

h2.4

Measure the inside of the runner, short turn and long turn. You could use a soft tape, like a seamstress or taylor would use. Tape one end to a reference point and make sure the tape conforms to the runner shape as you go through it. Good luck with your project!

TomCat39

Wouldn't a roll of clay be a little easier than trying to conform flat tape to the runner walls?

I would think the soft playdoh would naturally conform over the tailor tape?

PyroProblem

I think playdoh would be easier to stretch and move thus possibly skewing your measurements. Tape may not lie completely flat in the runner, but I don't think it would have a chance at changing length as much as play doh would.
You could always get some real narrow tape and try that.

Sikrthnyoavrage

I know this has nothing to do with this thread really, but I just signed up with this forum and I have to wait to start a post, but I'm having an issue with my B20b swapped DA9 that I needed suggestions for ASAP. I was driving home this morning, playing with this Beamer, and I ran through 3rd, 4th, 5th gear, when suddenly my car started to lose power and slow down, I was freaking out of course because this is my daily, I noticed good sized sparks flying behind my car, I put it in neutral and coasted to a stop and turned her off, before I did that I noticed the battery light and the oil light was on, but I know there is oil in it, and I let it sit for a few minutes, tried to start it and it turns over but it won't start and the exhaust makes a popping noise. So that's basically my issue, I've only had the car for a month now I don't know the history of it all I know is it ran great it was quick I love it but now this problem has arose, so if anyone might have a clue to what might the problem be or what I can check out or try to do to fix it that would be great, thanks a lot. please help my noob *** haha

h2.4

I would just worry about the playdoh stretching when removing. You could apply mold release to the runner interior and use duraglas. Shape a thick enough section to remove without breaking. Or as lame as it sounds, hotglue, when it sets then carefully remove and measure.

TracerAcer2.2L

I may not have thought this all the way through but, what about using string?

Got some amazing ideas the other night for modifying my H22 manifold, just need to find time to do it. You guys are helping a lot in the "accurate measurment" department

h2.4

^^ Tracer, I cut the plenum and shortened the runners down on a H22 that we did awhile back I think you saw the graph on another thread. Everything else was pretty "run of the mill", but on this engine we peaked hp at 8200rpm. On a stock port head H22 peak hp at 8200 is not that common. I shortened runners down to "roughly" 7-7.5" and hollowed out the butterfly plate. It worked really well on that particular setup. I haven't seen many H22 with stock or type r manifolds peak over 8k.

TomCat39

Had this thought too but not sure how easy it would be to keep the string on track by itself. Some of the runners are semi S shaped as well as curved to go up to the plenum.

One thought was string and roll of playdoh combo. The playdoh should keep the string on track with the runner and the string will prevent stretch.

Maybe with the combo you could mark the string at the top and the bottom and get the as close to accurate as can be?

As it was, when I used the roll of playdoh, I let gravity both settle the roll to the runner wall, as well as let gravity do the work and make the roll fall out of the runner. Don't think the roll stretched or compressed much in the process, but it is a very valid point and concern. I just didn't flip the intake over and do the opposite wall when I did the one measurement.

TracerAcer2.2L

Yeah I've done a lot of researching threads, I've seen just about every modified version of the OEM manifold out there. There are just a couple things no one has tried yet, I won't know until I test but I think there's a lot more power to be had out of it. The euro-r is not that great imo, so no surprise there. I have a skunk2 mani with stock TB right now, when I got it tuned we only went to 7.8k rpm (motor had sat for a long time). The power carried hard all the way to 7,800, I don't doubt it had another 200-400 rpms in it. So really the junk2 isn't that bad imo

Honestly, knowing what I do now, being off 1/8-1/4" isn't going to affect where you make power that much. Most OEM manifolds have uneven runners anyway and there's not much you can do about that, yet OEM manifolds still make great power despite this. As far as tuning runner length for harmonics, you will have a range of a few hundred RPM anyway where it kicks in, if you're off 1/8" you'll still be in range, I believe

Mr. Dabolina

I want to start out with saying that I don't post here or do forums much anymore, but I love seeing threads like this popping up and staying alive. It reminds me of how I got myself on the educational and career path I'm on right now. I also did a quick skim of the thread so if I'm preaching to the choir then my bad.

While all of the math and general trending you've learned is incredibly helpful in doing a very intuitive and quick analysis of what works for you, it isn't worth fighting for a 99% perfect analytical design. Every design parameter affects every other design parameter. Without computational fluid dynamics ($$$) or a 1D engine simulation software ($$$ for OEM level but Desktop Dyno is cheap/free), it really impossible to get an idea of how the engine is going to work at a finite level. Even with those softwares it's still a crap shoot because so many assumptions are made by the software. Anyone who works in OEM level engine validation will stress how much experimentation goes on to validate and calibrate the software models.

I'm a bit biased because my bread and butter is combustion and tuning and less mechanical design, but for a lot of the setups you'll see coming out of a grassroots (ie not OEM funded) program can benefit more from a more refined and cylinder trimmed tune than from an intake tuned to have resonance at exactly 5000rpm. Tuning and cylinder trimming makes up for the unknowns in your engine design. I can ramble about this longer, but I won't clutter your engine design thread.

Something that seems to always get missed when designing an engine is fuel choice. Each fuel, along with having its own knock resistance, has its own burning speed. While the burning speed is still heavily dependent on in-cylinder turbulence and pressure, ethanol burns slower than gasoline. So theoretically an engine running E85 would benefit from more dwell time than a gasoline engine would which drives your R/S ratio also.

I know this will probably **** some people off but a ton of the engine math online is wrong (way, way, way over simplified) or draws significances out of coincidences or parroted information. My favorite example being all the stuff getting thrown around about R/S ratio a few years ago. There are countless threads and build dedicated to analyzing and attempting to push engines to a predetermined R/S ratio (1.75 mainly) out of some coincidence with the B16A and SBC having numbers fairly close to that. It's an expensive gross oversimplification of a very complex problem. Dynamic CR has a similar place in my heart too. These values are great for a starting point or as a check to make sure you didn't REALLY screw up but being dead on a value isn't going to get you a magical amount of power or reliability.

So I guess to sum up my rambling, don't spend too much time tearing your hair out over equations on the Internet. You're better off understanding the trends that changing parts has on your end goal, but also remember it's hard to drastically change the shape of the torque band of an engine because you're so severely limited by block packaging. And oyea tuning, tuning, tuning, it'll get you there.

Mr. Dabolina

If anyone wants a copy of Heywood's Internal Combustion Engines, I have a PDF I can get to you. It's 1000x better than trolling the Internet because it is THE book on engine design. It is a college level text book so it can get a bit dense at times thoigh. PM me if you're interested and I'll get you a link.

TracerAcer2.2L

Good stuff, Mr. Dabolina. After spending approximately 6 hours developing an exact formula for harmonic resonance tuning, I can confidently say that every single online calculator is dead wrong, with only one calculator rendering any result at all similar to what I have. And even with such an exact formula, it is still no substitute for real world testing (although wave tuning, in particular, is far more forgiving than some of the other topics you mentioned, and in this instance I believe the formula should suffice)

PM'd

TomCat39

What you said is pretty much the impression I gathered from scouring the inet.

Thank you for confirmation. Now I know instead of only guess I was barking up the wrong tree.

ollp

Have anyone made this work HT = (r + c) - (r cos (a)) - SQRT(c^2 - (r sin (a))^2)
when I try in calc and use 3.4 as and c is 6.25 after 180 the crank have moved twice the distance meaning 6.8

TomCat39

Okay so it looks like you are using the corrected formula.

What specifically are you using the formula in? Remember "r" is radians and excel does not work the same with radians as a scientific calculator.

I don't recall the exact details about radians and degrees but it does make a significant difference.

Actually, I got it backwards. If you are using MS excel you have to convert degrees into radians as excel does not do trig functions in degrees, only radians. This tidbit allowed me to fix up a formula in excel I was using that was spewing out all kinds of garbage.

I am not sure where you are using the formula but if you are in degree mode trying to process radians..... you will come out with some messed up answers.

Mr. Dabolina

I think you mean "a" is in radians. "a" is the angle after top dead center. "r" is crank throw (ie stroke divided by 2) if I remember correctly.

I'm not entirely sure that equation is correct though. It looks like when you put in zero for "a" (TDC), it doesn't sum to the rod length plus the crank throw like you'd imagine it would for the height of the piston at TDC. I'll check my notebook when I get to campus though.

ollp

Thank for reply, Just to make it clear To all. Radian= Degree* 3.14 / 180


Degree as you say after TDC

TomCat39

Doesn't matter. What Mr Dabolina is eluding to is the formula is incorrect.

And really, the source the original formula was pulled from seemed to have it written pretty messed up to begin with so then the base was not good when mithious attempted deciphering the already broken formula.

The result is just another broken formula.

Doesn't matter if we are working with radians or degrees in the formula, if it's broken, it's broken.

Mr. Dabolina

Little late, but finals are keeping me busy.

Here is the correct equation:

distPiston = (r + c) - (r cos (a) - SQRT(c^2 - (r sin (a))^2))

For clarity:

distPiston=(piston distance from TDC)
c=rod length
r=stroke/2
a=(angle aTDC in radians)

The only issue with the one posted previously is that one parenthesis was misplaced. It should work now. Also, remember not to mix and match length units. Rod length and stroke should be in the same units (in, mm, cm, etc). The result is in the same units as you entered.

Happy mathing.

ollp

have anyone used this Formula


A(t) = -4sin(2pu)p²u² - 4R⁴sin(2pU)²cos(2pU)²p²U²/((L²-R²sin(2pUt)²)³)^½ - 4R²cos(2pU)p²U²/(L²-R²sin(2pUt)²)^½ + 4R²sin(2pU)p²U²/(L²-R²sin(2pUt)²)^½


please explain: 2pu I think radians at crankangel
please explain: p²u²