patman

iTrader: (3)

damnit, scalli, every time i get caught up with the club and full of enough rotary stuff to satisfy me for a week or two of homework, i find another one of your threads.

I have considered the semi-pp idea for a while...maybe on my next engine... but i had never thought of 'adjustable' ones like you.

My input is this: I'm an on-the-fly type of guy. with a little bit of extra ingenuity and some solenoids (i already have a basic design in the ol' rattlebox) you could make 'automatic' chokes. What i would do is wire them up to the aux output on the Microtech, so that when you switch maps they are automatically opened. In other words... you are sitting at a stop light, an enzo pulls up next to you, you grab the laptop, fugg with it for a sec, wait 15 secs for it to load, and then kick his ***! then switch back and get 20 mpg again without ever getting out of the car.

Damn...im gonna be thinking about this for a week...I have exams coming up, too.

pat

Scalliwag

The way I understand it is that the Microtechs dash unit will store 3 maps so you can change them on the fly. So if you did get a solenoid system working and tuned you could have a dual stage semi pport where you could get a good road race setup going on the first stage and for drag you could have a second stage of pports actuate.
I am not sure how you would run all of that but it will give you more to think about

patman

iTrader: (3)

i use the laptop, so i can store at least 4...maybe more. 2 would be all you need tho. as far as on-the-fly, it takes 30 seconds or so to change between them with the laptop, not sure if that is any different witht the dash or not.
I just didnt like your idea about taking it apart and removing the sleeve....or at least thats how i understood it.... seems like there are much easier ways to restrict it that could be remotely controlled with the flip of a switch or push of a button.

Theoretically, you could tune the microtech so that no map change was even necessary, but that would be dumb. However, heres my latest idea:

Set it up with an infinitely variable p-port opening. Have it closed at idle, and then use a seperate injector and controller...maybe modified mega-squirt.. to adjust for just the p-port in real time, so that you can turn it off...and just have the port all the way closed, or turn it on and have it open as a function of load or RPM... giving you more low-end torque and then a gradually increasing power curve. Once you figured out the changes it made, ie how much fuel needed added, whether timing needs to be modified, etc, it would be relatively simple to set up a controller and program it. Every time I think about it, I like that idea more and more.... If only i won the lottery....

anyway, my next engine might see something like this...

SnowmanSteiner

I guess I'm just crazy for wanting to run a full fledged pp on the street. Oh well I've never really cared for the amenities of ac/heat/ps/carpet etc in my car.

- Steiner

2sevens

This type of set up has been ran for years, many of the 24hour endurance cars back in the late 70s and early 80s ran this.....no problems....lots of abuse!!!

Scalliwag

Yes you read right but there is a method to the madness there. The modular manifold system I want has to be changed radically for street and strip. With the big honkin pport tubes you have an insane amount of port timing for street.
With well made insert tubes you could taper the port timing and make it much more street friendly.
Another thing is that for street use I would want the manifold to wrap over the top of the motor to get some runner length and the throttle body would be set as side draft.
But when it came time to race it then it would all come apart by set screws and o-rings. The throttle body for racing then would be setup as downdraft like you see on Scheepers setup. You would just need to remember to switch the maps.
The inserts are the only way I know of to be able to control the port timing. I would want something that was truly livable on the street but could switch to a very radical mammajamma at the track.

It would be a blast to setup

Marcel Burkett

"radical mammajamma "

Kenku

The problem is though, you can't *really* control port timing with sleeves like that, for reasonable levels of fabrication. Even if you restrict the pport runner down to, (pulling numbers out of thin air) 30mm instead of 48mm, the bit cut out of the chromed iron determines when it's open. I don't *think* you're going to try to make the sleeves that close of tolerances are you?

... OTOH, in reality as long as you're close, there won't be *that* much difference. And even if you left quite a bit of room, the choke inserts expanding out to port size may help fight reversion.

Scalliwag

That is what I would plan on. Getting the insert as close as what is safely possible. We are working on buying a cryo system for the shop next year. If this ever did come to fruition we could make the tolerances on the inserts incredibly tight and cryo them so that there would be no thermal expansion.
But like you say as long as you are close the timing effect would be whatever the insert is. That is mainly due to the fact it does not pull hardly any air if the wall of the insert is anywhere near it. If this was done on the exhaust side that would not be the case because the force of pressure would drop significantly as soon as it hit any gap.

dennis91turbo

what is your overall plan for this p-port you are building.

Scalliwag

Who is the question poised to?

patman

iTrader: (3)

actually, i hadnt thought of changing the port timing. I was only thinking about tube size to change the velocity of the intake, and injector placing to atomize the fuel correctly. I had a design drawn up in ProE for a prett decent solution to all that. How much of the idle problems of a PPort is due to port timing/duration and how much is due to sze and intake setup?

pat

SnowmanSteiner

I think the idle problems are mainly due to the amount of overlap you have with the exhaust. So mainly the port timing, when it opens. But I'd wait for Scalli to reply or someone who has more experience than I.

- Steiner

Kenku

Well, from what I've determined, most of the idle problems are from the fact that people put carburetors on the things and as such have trouble dealing with the highly fluctuating vacuum. Apparently, Mazda specs motors with the factory race housings to idle at 1k RPM with EFI. But then, they run Alpha-N type injection (no MAP sensor) so fuel going in is completely independent of any manifold vacuum readings.

As for what causes the whole thing... kind of both. Intake reversion is caused because the ports are open until quite a while after the chamber starts getting smaller (this is true on all of the port timings, even the stock ones, but not to this extent) but because the large runners mean that airflow has fairly low velocity at low RPM/idle, it doesn't have enough inertia to resist the reversion. I can't say off the top of my head whether decreasing port area but keeping timing or decreasing port timing while keeping the same area would have more of an effect... there's relatively little published data on how to make pports work well at low RPM, for obvious reasons. Though really, for relatively large changes, it doesn't make sense to not change both at once.

Of course, you have to realize that (at least according to Mazda technical papers) the MFR motors had intake runners that taper as they go towards the ports. The throttle plates may be 48mm (flat slide) holes, but where they bolt to the rotors, they're down to (off the top of my head, don't have the papers in front of me) 39mm. Ignoring frictional losses, that boosts airflow velocity to around 150% what it is at the throttles.

I dunno. Trying to get the things to run well at low-load/RPM seems to be missing the point to me, especially since most of techniques to do so require changes that kill high RPM breathing.

Scalliwag

It is both the timing and the tube size. This setup is the piston equivalent of a full race cam and a tunnel ram intake. No matter what you try to carb it with you have idle problems.
In the case of a piston engine the tunnel ram lets the fuel drop straight through the valves which are staying open a long time to maximize the air/fuel charge. That setup is great for drag racing but sucks for street.
That is why I think to get the best of both worlds the inserts and runner extensions would be ideal.
Most people have to settle for what in their view is a happy medium for a street/strip cars and that medium by default will take from the maximum potential of both street friendly and drag performance.
To hell with the balance. I would much rather spend 20 minutes with a T-handle allen wrench to change the intake setup and change maps.
Now of course this does not take into account gear ratios and trannies. A really nutty idea would be to have a Ford 9" with a limited slip for street and have a solid spool with a better drag ratio in a pumpkin for the track. It would be a royal pain in the *** but it would be the best setup to go from a true street to a "badass mamma-jamma" drag car

SnowmanSteiner

Come on if you're not driving the car every day, it would be tremendous fun to have it just bad as hell. Sloppy ports, overlapping, with that gorgeous brap. Twin wastegate runners coming out behind the front tire, with a downpipe extension coming out right behind them hooked up to an electric valve. Propane/methanol injection with an antilag setup on a huge turbo. Ohh sorry let me wipe the drool off my chin and try and wake myself from this dream.

- Steiner

Kenku

Enh. Turbo, schmurbo.

SnowmanSteiner

Hey we all have our dreams.

- Steiner

Scalliwag

But think of the bets you could win when you were able to back what would appear to be some pretty outrageous claims by stating you could do (put E.T. here) in a quarter with the same motor without NOS. While they are listening to this mild mannered sounding motor that they know full well could not do the time you stated.
Talk about fun and profit

SnowmanSteiner

Well around my town in home, most people know which cars are the ones putting down serious numbers. That and quite a few of them have dumps on them. Thankfully the local police just crack down on the dumb people in the group i.e. people doing burnouts trying to race from stoplight to stoplight etc. I used to want to have a conservative setup that could still kick butt with a few changes, but the more and more that I go out, when I'm home, the more I just want a bad *** car. I like having a race setup on the street I think it would be fun, not to have any crap, besides I have the truck for dd.

Anyway to try and get back on topic, if you really wanted to over-engineer it so that you could go straight from street to race, you could design a system so that the internal tube could close in on itself. Basically have the internal tube not be completely solid have a peice at the top and bottom that can move up so that it retains an oval shape. Problem with this is you have to design very small components to be able to fit in there, drill the outer diameter larger to accomodate them. And the main reason is because the tolerance at the actual housing, where the seal travels, would have to be the same. You could have external parts to just have a lever push up. But again this is basically just over-engineering the crap out of it. I have a hard time coming up with easy solutions I always want to do radical things, and often don't even think about the simple ways until pointed out. I really need to fix that if I am going to be any use in the job market.

- Steiner

patman

iTrader: (3)

i'm still stuck on the sliding inserts thing...heres a quickie i did in class the other day...you should see my calculus notebook. lol. seems like this way you could tune it for a continuous map based on a MAP and then modified per how far open the insert was...and the insert could also be electronically controlled by the computer so that its open percent was a function of RPM.

am i missing something?

QuagmireMan

you dont think that the heat + vaccum would cause a problem with your slidding insert? would it be air tight? how?

i dont mean to hate, i just want to get your creative juices really going.

patman

iTrader: (3)

it would be semi- airtight. as in, a tight fit, but not necessarily comletely airtight. kinda like a slide stye carb like on a motorcycle. wouldnt need to be airtight, as it is not sealing anything per se, just changing the port size.

pat

QuagmireMan

gotcha

Scalliwag

Nylon or Teflon o-rings work great for those type of setups.