Intake Port Size/Velocity and Power

[magicweed]

This discussion got started up in another thread and I thought it was deserving of its own topic. I just wanted to get other peoples ideas on what optimum port size and velocity is when dealing with our engine application. As I don't want this to seem like I'm just looking to get information for free, I'll give my ideas first.

At first glance, some might assume that the ports on our engine are adequate due to the restriction of airflow, but I don't believe this is the case. According to numerous sources and some Dyno results (I wish they were our results, but sadly no), the stock ports on the motors are too large for even the stock application!!! According to numerous engine builders, optimum port velocity is at least 320ft/s and maximum volumetric effieciency is achieved at as high as 670ft/s.

The lead enginer designer and myself are looking into this and are planning to dedicate a lot of testing to this once we have a reliable engine running on the dyno. If found to be beneficial, it could lead to other areas of interest, like the limitations of the camshaft lift, duration, valve size, etc. Since everyone likes talking about power and making more, I assume the serious engine guys should chime in on this.

[magicweed]

This discussion got started up in another thread and I thought it was deserving of its own topic. I just wanted to get other peoples ideas on what optimum port size and velocity is when dealing with our engine application. As I don't want this to seem like I'm just looking to get information for free, I'll give my ideas first.

At first glance, some might assume that the ports on our engine are adequate due to the restriction of airflow, but I don't believe this is the case. According to numerous sources and some Dyno results (I wish they were our results, but sadly no), the stock ports on the motors are too large for even the stock application!!! According to numerous engine builders, optimum port velocity is at least 320ft/s and maximum volumetric effieciency is achieved at as high as 670ft/s.

The lead enginer designer and myself are looking into this and are planning to dedicate a lot of testing to this once we have a reliable engine running on the dyno. If found to be beneficial, it could lead to other areas of interest, like the limitations of the camshaft lift, duration, valve size, etc. Since everyone likes talking about power and making more, I assume the serious engine guys should chime in on this.

[kozak]

yeah i remember this, and it was discussed that smaller ports would be better. however a soon as the air from the smaller runners hits the larger size of the ports in the head it would kill the flow again, you would need to find a way to sleve or add material to the intake ports. i believe that this was the concensus reached.

[Storbeck]

J B Weld...

[Andycostin]

Yeah, I'd back the philosophy of port filling to aim at improving the flow through. Aimed at straightening the port and reducing any casting surface roughness left.

Initial design using CFD would be a great starting point, but you could also just move straight to testing on a flow bench using JB Weld or bluetak. Then verification with some dyno testing... further thoughts??

Andrew Costin
Engine Team Leader 05
General Nuisance 06
Full Boar Racing
Swinburne University

[magicweed]

Port filling with the JBWeld 24 hour epoxyseems to be a pretty standard method of port filling, and I believe the consensus was that smaller ports were better, but not for better flow. If you fill the ports so that the intake charge reaches those velocities, you'll actually lose flow in terms of cfm on a flowbench. That however is due to a flowbenches inherent design flaw. It's only designed to measure the flow during a steady state vaccum. The cylinder continues to be filled (if adequate velocity is achieved) after BDC and continues until the camshaft closes, anywhere from 30-60 degrees ABDC. I believe thats the area we need maximize the amount of filling in, making the most efficient use of the intake cam's duration.

I think CFD would be good on a replica representation of a port and could yield some benefits, but I think that my teams looking more toward the last one. Throw some JBWeld in there and see what happens.

[lyonsb]

one thing to think about: how are you actualy going to manufacture a JB or welded set of port? Unless your working on a single cylinder (where you dont have to reproduce the added material on multiple ports) I think there is more potential for harm than good, by modifying the ports unevely or causing head distortion (with an actual weld up). sorry to sound like a grumpy old machinist, but wouldnt want anyone to ruin a head...

maybe a way to do it would be to CMM or clay mold your ports, then modify that model (physical or digital). Then use that model (either clay or RP from the file) to make an Si mold of the area you would like to change (not hard, just get a showbox and some pour-a-mold).

with a Si mold (and a wax/PVA release) you could make a set of identical inserts from a Fe filled epoxy (JB) and then bond them to the ports, to get identical properties.

just my $0.02

[magicweed]

Creating some sort of sleeve would be the best way to tackle this endeavor, I agree. You would be able to modify the entire port ensuring the best about of blending and ensuring that the ports are all the same. Overall, I think this is the way we will go in the future, but for the principle of practical testing to see what the possible benefits are in a real world application, I would rather do it this way. It is also the reason I posted for an extra Yamaha R6 cylinder head in the wanted forum, just in case. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[DaveC]

And how about tapered primary runners? I have not found a good way to test the effects of that, either modeling or manufacturing.

That 320 fps to 670 fps is a pretty broad range. Any ideas on what the optimal speed will depend on? This could be modeled in Wave, I'd guess, can anyone suggest a technique for this?

[magicweed]

I don't really think the range of speeds is that great when you look at the ramped curve of the mach index. Since it's dependent on the relationship between the minimum cross sectional area of the valve/port and the set cross sectional area of the piston as well as stroke, you can see that its a pretty linear increase in port velocity as the RPM's increase. A good engine dynamics text book should have the equations to calculate it, as well as a chart relating it to volumetric efficiency. The only thing I'm still looking for is how greatly the charge density affects the system. Also, flow through the restrictor after our CFD is done on it will help in determining whether it will choke the engine earlier, but thats for later.

As for modeling it in Wave, I'll have to pass on answering that. Our CFD program is Fluent and we lack engine simulation software here. Oh how my grades would suffer if we did.

[Anthony V]

I agree that reduced port sizing is important. It doesnt even take an engineer to know that stock ports are too big for our restricted motor.

sleeving would be cool cuz you would have consistent runners, but as mentioned, i question the benefit if the ports are not matched to the new runner sizes. otherwise you are gonna give up port velocity in the end.

I respectfully disagree on being able to calculated volumetric efficiency based off of Mach number. As we all know, the delayed charging effect that we are all talking about which takes place ABDC, which is what we are chasing after to improve, is dependent on the window of opportunity for this to occur. now we are getting into cam timing. your cam timing is gonna determine when/whether this happens. picking the best compromise between choking high rpm flow and improving midrange is the real dillema. say for example, Tuner1 wants to trap good cylinder pressure in the low to midrange rpm...a Mach number of .5 at 12000 rpm is peachy keen but if he is closing the intake valve 20 deg ABDC (for lower rpm torque) then the mixture coming in at Mach .5 is gonna get rejected when it hits the closed valve anyways. I am over simplifying things here but im trying to make my point that you should consider Mach number and cam timing in the same context. And i dont see how you can get volumetric efficiencies off of Mach numbers...unless there is some magic equation somewhere that takes into account cam timing. If there is then i need to find it. http://fsae.com/groupee_common/emoticons/icon_wink.gif

-2 cents
Akron Engine Captain

[lyonsb]

Were doing tapered runner tests now, using lots of RP, but itd be possible to roll-your own welded cones from sheet Al (HP books makes a good sheet metal handbook for practical stuff like that).

[magicweed]

In the discussion on f4i engines mods, I had mentioned toward the end that modificaton of the entire head would be a beneficial effort for any FSAE team willing to undertake it. This included redesigning the size and shape of the ports as well as the placement of the choke point, valve sizes and combustion chamber design. I'm also aware of the issue of cam timing, which I was hoping someone would pick up on Anthony.

Since we are talking about maximizing the effective filling of the cylinder after bottom dead center, the effective duration of the camshaft (The area where the intake charge travels at less than choked flow. We need to remeber that since the cam profile isn't sqaure, the available amount of lift increases and decreases the mach index. Lowest mach index coming at maximum lift) becomes the most important factor after port size is determined. Depending on how you want your engine to develop power, intake duration and duration ABDC become the most important parts.

The chart associates volumetric efficiency with mach index, but doesn't directly calculate it. However, I have seen your magical calculation that takes into account mach index and cam timing. Hopefully I can get it into MathCAD or even easier, Excel.

[DaveC]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> using lots of RP </div></BLOCKQUOTE>

whats RP? With your tapered runners, do you taper down to the stock port size? I'm having trouble finding a way to test this without actually building a ton of stuff. If I could find a way to test several different tapers on the same plenum, that would be great. Right now, its lookig like an entire intake manifold would need to be fabricated to test a single tapered runner design. Yes, I am too lazy to build a bunch of intake manifolds that will get thrown in the garbage. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

I know you can model tapers in Wave, but there are limitations... I guess at small taper angles Wave would be OK. Maybe between this year and next I can learn Vectis, and find a big computer to run the sim on. Time is running out for playing on the computer, Its about time to start building and testing stuff.

[Greg H]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DaveC:
whats RP? </div></BLOCKQUOTE>
I beleive he is talking about rapid prototyping. In most cases, if you can model it, you can make it.

[Anthony V]

Stan,

I smell what you're cookin man! haha http://fsae.com/groupee_common/emoticons/icon_wink.gif Seems like we are thinking along the same lines. Where did you find that "magic equation"? I'd be willing to help you out in any way i can if there is something that you think i could actually help with...in finding a way to get it into excel or whatever. i'm not sure what it is you are working with, just throwing out an offer of a helping hand. Let me know if there is anything i can do.

[magicweed]

It's not really putting this "magic equation" in excel that is the problem. The problem is ataining the values and constants required to make the equation as accurate as possible. Thats what we're going to have to do some testing for. I'm sure we'll get it sorted out, and with any luck you can hear all about it during our design presentation in May. http://fsae.com/groupee_common/emoticons/icon_wink.gif

edit: Thanks for the offer though, if we can get it to work the waqy we expect it to, you can have the equation and any help I can give setting it up. I'd rather do it within the team as to control the variables in procedure. Some people just do things differently.

Has anyone given any merit to a variable area port design incorporated into the head?? Ever since we started talking about this, an idea has been floating around in my head for a design. I was also liking another suggestion that came out around here. I'd love to organize some sort of FSAE engine design consortium focused on design of a "perfect" FSAE engine. That'd be wicked cool!!

[Z]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by magicweed:
Has anyone given any merit to a variable area port design incorporated into the head?? </div></BLOCKQUOTE>
Ford (I think?). They block off one of the intake valves with a butterfly at low RPM. Increases velocity and swirl.

Z

PS. Consortium to design "perfect" FSAE engine might be like deciding what is a perfect woman! http://fsae.com/groupee_common/emoticons/icon_confused.gif

[magicweed]

I think most of the throttle bodies that come off the engines we use at competition has something similar to that. At least the GSXR that we used was configured like this. This is more of a restrictive way to increase and velocity and swirl. I was thinking more along the lines of a fully adjustable runner and port that changed cross sectional area lineraly with RPM without disrupting (near)laminar flow until the charge entered the cylinder. It would flow like a standaard head without restriction at all RPM while maintaining the predetermined mach value designed for.

[Z]

Stan,

UWA has continously variable length intake runners. These are a copy of a system on some BMW production cars. I can imagine a similar system that would also vary the cross-sectional area of the runner, but only up to the cylinder head. See Race Engine Technology (Oct'05) mag for more info.

IMO, a lot of work for only small reward...

Z

[TG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Z:
Ford (I think?). They block off one of the intake valves with a butterfly at low RPM. Increases velocity and swirl.

Z

PS. Consortium to design "perfect" FSAE engine might be like deciding what is a perfect woman! http://fsae.com/groupee_common/emoticons/icon_confused.gif </div></BLOCKQUOTE>

I know Honda has a different strategy for the VTEC on their VFR800FI engine. Instead of having a high speed cam lobe that is activated at a certain RPM, they disable one of the two intake valves at lower rpm that is reactivated at a certain rpm.

[DaveC]

I'm not a huge Ford fan, but thats a great idea for a road car. Implementing that idea sounds pretty tricky, do you know how Ford did this? I'm coming to the conclusion that a variable geometry intake manifold will have minimal gains if the rpms can be kept fairly high. I was considering it, there are definately gains to be had, but shifting gears is fun, right http://fsae.com/groupee_common/emoticons/icon_smile.gif. In the interest of simplicity, I'm leaning towards the port shrink (with no variable intake), although I'm still wary of applying epoxy in the ports, and I'm not sure if a sleeve that only extended a little bit into the port would be the best answer as there will be an expansion after the sleeve. Maybe we can test on our '04 or '05 car...

So, how about the exhaust ports? Reasons why you'd want a certain sized exhaust port are a little harder to grasp intuitively, but sims showed losses using smaller diameter (than the port exit) exaust primary tubing, so I'd guess there might not be much to be gained there. Any ideas?

edit: TG posted at the same time I did. But, yeah, I guess disengaging a valve could be considered tricky.

How about a boxer 2? Use 250 heads from a single?

[Anthony V]

Stan, I hear ya man. Totally understand where you are coming from. I'm careful about giving people things to do on our own team that are engine related just because I feel that if I did it, i know i thought it through. Whereas if i hand it off to someone else...it better be someone you know and trust that's all.

[magicweed]

Hmm, lemme think about that for a second...


I think there are some gains to be made on the exhaust side of the engine with shrink porting. This is a bit trickier as the exhaust port must either filled with weld or the same style of sleeve must be implemented using a material capable of higher temps than the standard aluminum. If I'm thinking correctly, an increase in exhaust port velocity would minimize the amount of exhaust gas brought into the cylinder during valve overlap. This would be caused by the increased inertia of the exhaust gas which would greatly reduce the amount of reversion. This creates a cleaner intake charge and more power. Thats what comes to mind off the top of my head, but I haven't slept in a couple days. God damn end of the year projects/papers/parties.

[BeaverGuy]

I believe the mechanism Ford uses is a butterfly valve that blocks the port to one valve. The first and only instance I have heard of it is on the '05+ Mustangs. At the same time it is one of the first things many owners are removing when they mod their engines. You could probably find more information on one of the Mustang forums.

[Test Driver]

Some late 80s Isuzu models had the same system of blocking off one valve. Did'nt the Honda CVCC have something similar as well?

Brings to mind something someone said recently about there not being real and new IC engine innovation to speak of.

Ramon

[Chris Boyden]

Mendoza?

I gather that you moved up north?
Are you still with Firestone?

Chris

[DaveC]

Wasnt CVCC the system with the rich chamber that was ignited, and in turn ignited the leaner main cylinder? Honda has come up with some cool designs, but in other ways lags a decade behind the competition. At least they dont have their customers do their testing for them (like Ford).

[buddy]

Test Driver,

'89 Isuzu I-mark RS (or any 4xE1 engine variants) had twin runner per cylinder manifolds with one runner blocked by a butterfly valve. Some of the Toyota's (early MR2's) and Mitsubishi's (Japanese spec 1st gen Eclipses) had similar systems. Supposedly improves runner velocity at low engine speeds. On my I-mark the valve opens at approximately 3k rpm, with a 7.2k redline

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Z:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by magicweed:
Has anyone given any merit to a variable area port design incorporated into the head?? </div></BLOCKQUOTE>
Ford (I think?). They block off one of the intake valves with a butterfly at low RPM. Increases velocity and swirl.
</div></BLOCKQUOTE>

Ford Duratec V6 does this, also Duratec I4 although the butterfly has a sector cut-out in it to promote a lot of swirl.

But, I think this would fall foul of the no throttling downstream of the restrictor rule for FSAE.

Ian

[Test Driver]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chris Boyden:
Mendoza?

I gather that you moved up north?
Are you still with Firestone?

Chris </div></BLOCKQUOTE>

Chris,

I did move up north and I'm now working for Tenneco. I'm still doing ride and handling testing but now my work is shock tuning.

Ramon

[Test Driver]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by buddy:
Test Driver,

'89 Isuzu I-mark RS (or any 4xE1 engine variants) had twin runner per cylinder manifolds with one runner blocked by a butterfly valve. Some of the Toyota's (early MR2's) and Mitsubishi's (Japanese spec 1st gen Eclipses) had similar systems. Supposedly improves runner velocity at low engine speeds. On my I-mark the valve opens at approximately 3k rpm, with a 7.2k redline </div></BLOCKQUOTE>

I too had an 89 I-Mark RS. Back then, that engine had a nice and seldom heard rev noise winding up towards 8k before the limiter slowed it.

[buddy]

Test Driver,

yep, your right the I-mark had the 8k rpm redline. My Impulse RS ('91) had the 7.2k rpm redline (4xe1-wt's had heavier rod's and pistons for the turbo)

[Ben Inkster]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">So, how about the exhaust ports? Reasons why you'd want a certain sized exhaust port are a little harder to grasp intuitively, but sims showed losses using smaller diameter (than the port exit) exaust primary tubing, so I'd guess there might not be much to be gained there. Any ideas? </div></BLOCKQUOTE>

DaveC, just wondering if you were modifying your valve flow coefficients accordingly with the port reductions? I've never flow benched different port sizes and compared coefficients but intuitively you would think they would change.

I also agree with murpia, a butterfly in one of the ports must be considered throttling of the engine downstream of restrictor. I still wonder about those 3D cam profiles though, that could be great way to get around that rule.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I'm coming to the conclusion that a variable geometry intake manifold will have minimal gains if the rpms can be kept fairly high </div></BLOCKQUOTE>

Probably true, but why are are you so interested in high rpms and changing gears? I don't know whether you have driven many of these cars but the last thing you want is to be changing gears all the time.

-Ben

[magicweed]

I think that in this case a flowbench would be deceptive. Your goal isnt more flow at a certain level of vaccum. Instead, the goal is increasing the velocity of the charges allowing more filling after the initial vaccum is lost. In most cases I've read about, you actually lose flow on a flow bench while generating around 5-10% more power. This was using the JBWeld method.

[Ben Inkster]

magicweed,
I'm not suggesting the use of a flow bench to determine the advantages of reduced ports. I am asking DaveC if he has use a flow bench to measure new valve flow coefficients to feed back into his ricardo wave model. Accurate valve coefficients can be quite important the accuracy of simulations.

There has already been several discussions regarding the use of a flow bench to determine intake distribution and general engine performance. Personally I'm not a big believer because they don't represent the true airflow motion in a reciprocating engine (although I know of others that will disagree).

-Ben

[DaveC]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">DaveC, just wondering if you were modifying your valve flow coefficients accordingly with the port reductions? I've never flow benched different port sizes and compared coefficients but intuitively you would think they would change </div></BLOCKQUOTE>

No, I have not. I have seen (in a couple different papers I have looked at, as well as sim) that reducing exhaust primary diameter from port size has not been beneficial. This is NOT with modified exhaust ports. I have not done anything so far with trying to figure out the effects of a smaller exhaust port. I am not sure how you'd come up with correct valve flow coefs without modifying a port and flowing it. We do have a junk head around, though. A good project might be to modify the ports a couple different ways, both intake and exhaust, have the head flowed, and input the new flow and size specs into Ricardo and see what happens. We dont own a flowbench, but I'm sure we can find one semi-locally.

As far as keeping revs high, youre right I have not driven fsae cars, but I do have some experience with similar events in a regular car. I recognize shifting a lot will make the car slower, and I've asked the team what is realistic in terms of usable powerband, and that will determine how much benefit there might be to a variable geometry intake. If we can keep the engine operating from, say 8-12000 rpms (just an example), theres not much benefit. However, if it helps a lot to have power down to 6500-7000 rpms, then a variable geometry intake will be more beneficial. I'm thinking if building a wider powerband than we can achieve without a variable intake is a big issue, and will make the car a lot faster, then I'd rather work on fitting a turbo than building an extremely complicated intake manifold. My feeling are mixed about turbos, but if all our drivers believe a wider powerband than what I can accomplish without one would be a big help, and we have people willing to work on it, and we can afford it, I wont rule it out.