If I port the intake port to get as early opening as possible (with out going to bp), beveling the rotor the get even earlier opening,

and keep the stock closing time. The ex. port will just be cleaned up.

How would this affect the power curve on a 13bt s5 engine?

Will it strenghten the low and midrange, or will the extra overlap do the opposit?



Ronny

It should be more powerful everywhere, at load. But tell us more, turbocharger will have huge impact, it must flow very well on turbine

This will be for my daily drive s5 convertible.

The turbo is a gt3540, with a A/R 0.84 T3 twin entry hotside, and a fully divided short runner manifold with a 45mm wg.

When you look at the rx8 port timing, the intake opens at Tdc, just after the ex.port has just closed, 0° overlap.

On the rx7 engine ex. closes at 48°atdc, and the intake opens at 32° ATDC, this gives 16° overlap and let the ex.port be the only open port for 32° into the intake stroke.

If I can get the Intake to open at 8°atdc and leave the ex.port stock, I get 40° overlap and let the ex.port be the only open port for only 8° into the intake stroke.



My thought is by reducing the time the ex.port is the only open port into the intake stroke, down to a minimum, and let the engine start sucking air from the intake port as close to tdc as possible, and not force it to try to suck the exhaust back from the open ex.port until the intake opens..

I would like to think this overlap is far better for low rpm/low load driving, and also increase the power in this rpm aera while stepping on it.



Compared to if you just ported the ex.closing time to 72° atdc (which also give 40° overlap, but let the ex.port be open 72° into the intake stroke), and leave the intake opening time stock,this will have a much bigger influence on the power curve of the engine, moving it up in the rpm range..



This is just my thoughts on this subject, and it might be totaly insane:)

So any input is appreciated

What I want to achieve is increased power in the 1500-4000rpm area and 350-400whp at no more than 7000 rpm.

I`m offcourse running standalone, and will soon be getting a Eomp controller:)



Cheers

Ronny

No, Its not totally insane, actually it seems you have good understanding how port timing works. Opening intake ports earlier and keeping stock closing will increase VE% curve everywhere so this is good start. But for your power goals rotor beveling seems excessive and would call for larger hotside than you are suggesting. GT35R compressor is very capable, but again excessive for your goals. Garrett T04E 57/60 Trim would be better choose. But if you already have GT35R go with it. For even better response you could use high compression rotors.

I will only bevel the opening edge on the rotors to gain a couple more degrees earlier opening.

This shouldnt affect the hotside as the ex.port timing wont change.

What conserns me is how the light load everyday driving,off throttle responce and 2500-4000rpm low load throttle respons will be affected, compared to a streetport that also moves the power curve upp in the rpm range..

Any

thoughts

It will effect intake/exhaust relationship big time. Early opening intake gives high VE%, but of course, we are assuming low turbine inlet pressure, lower than intake pressure, which would work with GT35R to certain RPMs.... Then it would be rather detrimental.





Any porting that gives good VE% at high load, suffers at low load. Its not RPM based, just LOAD based. Street port moves powerband up because of LATER closing, its same with every porting. Most people have no idea why they are porting in the way they do and then wonder why their engine has peaky powerband and weak low-end. Most funny but at the same time sad is, that their reasoning behind late closing and almost stock opening is, that they didn´t want to lose low-end "because of overlap"

https://www.nopistons.com/forums/pub...1047683358.gifhttps://www.nopistons.com/forums/pub...1047683664.gif



Hence for goals you want I suggesting early opening street port with modest closing and for better off-boost response high CR rotors.

Ronny you mentioned you would like to get the intake to open at 8 degrees ATDC. How will you be able to do that? I"m under the impression that we can't open before around 25 degrees ATDC.

I am guessing your are not using Renesis rotors.

i agree that doing nothing but opening the intake earlier will take the existing power curve and just move it up, IE it'll make more power everywhere.



more power = more air flow = you need a bigger turbine.



i think id rather add overlap with bigger/better intake timing vs a bigger exhaust port, i'll take the bigger intake port.

I'm glad someone brought this discussion up, it's been on my mind a lot lately. Sorry to hijack the thread, but there's some things I wanted to talk about too, due to some testing done by Defined Autoworks' 20B semi-pp N/A engine. Basically, when he closed off the small peripheral ports for testing to compare streetport vs. semi-pp, which in turn severely retarded intake port opening, his low-end power was nearly identical. It wasn't until higher RPM's (I believe 7,000 RPM +) that the streetport-only configuration ran out of airflow, and the additional port volume/overlap of the additional peripheral ports allowed it to maintain the same torque to 10,000 RPM.



So, how is it possible that reducing overlap, reducing port volume, retarding port closing and seemingly increasing intake velocity due to some of these factors not increase output in lower RPM's? That's contrary to all of the porting theory that's been common to all (I thought...) Is it possible that after a certain amount of intake port open advancing and close delaying, further advancing or retarding nets nothing because VE has effectively topped out up to a certain RPM, and if so where would that point be? Or does going more aggressively on the intake port never lose you any bottom end?



This is the post about the 20B N/A: http://www.rx7club.com/showpost.php?...&postcount=187



I guess what I'm asking is if anyone else has done back-to-back testing, in different circumstances, between porting, all else remaining relatively equal (including boost if turbo'ed) to show the relationship between porting and output characteristics.

Logan´s approach of semi-pp that are opened with more than 50% throttle is perfect. In regards of powerband, he should try close side ports and let engine in very low end and mid range - at load, run only with semi-pp, it should give more power, before exceeding semi´s flow capabilities.





Common to all on internet forums?https://www.nopistons.com/forums/pub...1047683785.gif



Mazda themselves and not only Mazda, many decades ago shown in tech. papers that VE% in whole rev range is increasing when intake ports are opened early, as much as 90° BTDC in case of PP and as much as 110° BTDC in case of BP, but, and it is very important, with free flowing exhaust and full load. These test´s were carried out with fixed intake closing, so in case of PP, port volume - area, increased substantially with earier and earlier opening, and still neted more VE, to the point, which I mentioned before.



With closing, its pretty straightforward. Later intake closing, loss of low end and mid range till enough RPMs where inertia of air/fuel mixture and pulse tuning will overcome delayed closing.



So simply said, intake opening - the earlier, the better , but its load dependent. Closing is purely RPM dependent, and sadly, there is no point of closing intake ports extremelly late, when owner is not going to rev engine enough, intake can´t support that, engine is not balanced, whole package is not build to take advantage of it https://www.nopistons.com/forums/pub...1047683664.gif

Exactly why I said, "I thought". I am still trying to learn as much as possible, especially on these internet forums. I certainly don't see them as a joke, they are the biggest source of knowledge for me for rotary engines, and I haven't seen enough Mazda tech papers to be as knowledgeable as you I guess.







So then they must design semi-pp's with closing time in sync with the closing time of the sideports? The reason I was confused was I thought the same way about closing times, but figured the semi-pp's closing time would have been later than the sideports. It's all starting to make sense https://www.nopistons.com/forums/pub...IR#>/smile.gif It would almost seem that stock side ports with the semi-pp would yield you better results vs. streetport, that way you could "stagger" the closing times based on the peripheral port being open or not.

Hey Mate,



Interesting theory, though the aditional overlap will mean that the intake stroke is swollowing more exhaust gas at low rpm than stock which is no good for power, though the big question is will the power gained by opening the port earlier outweight the power lost from the extra exhaust gasses in the inlet charge? The earlier opening may also give the engine a rougher idle. The other thing to consider is exhaust manifold back pressure. If you are running say 15psi boost with that turbo you will probably have at least 18psi in the exhaust manifold. so what will happen is the higher pressure in the exhaust manifold comapred to the lower pressure in the intake manifold means that the ehxuast gases will flow into the inlet ports which isn't good. The only way to improve that is to run a bigger exhaust housing



When i rebuilt my engine s513bt i umed and ahhed weather to port it or not as it was my daily driver and i decided to keep port timing stock though i made a flow bench and just tweaked the port runners. The advantage of the flowbench ment i could see if what i did made flow increase or decrease, though building the flowbench was another story lol.



You will easily acheive your 350+ rwhp with stock ports and your current turbo. I run the same turbo as you though i have an undivided 1.06 ex housing and off boost responce with this engine is really good, and the turbo is very responsive. I think your turbo would be even more responsive downlow due to the smaller a/r plus the advantage of the split pulse, just make sure your build the exhaust manifold with the shortest runners you can fit.



The other thing i was thinking i don't think you can open the inlet ports at 8 deg ATDC because there won't be enough meat to support the corner seals?



cheers



Lance

i can't speak for him, but perhaps he was including timing with rotor bevels?

i think i'm in the same place right now. i'm learning to curb my urge to go bigger with exhaust ports based on the (flawed) logic that more in should mean more out. i'm gaining more understanding of airflow as a dynamic (as opposed to static) concept each day.



it's funny because once i had completed my semi-peripheral housings and put the degree wheel to it, i started getting curious about some things. about that same time period, i also read a thread about a turbocharged full peripheral engine (i forget his screen-name at the moment) that had exhaust porting similar to mine and his power curve was not what he had expected. he hypothesized that perhaps his exhaust ports were probably too big, so naturally, it got me thinking. i spent a few months and wouldn't you know it, i had an A-HA moment ... i finally saw why big exhausts could potentially hurt a streetable powerband.



i'm dedicated to applying all the insights i've made since then to my "next" semi-pp project, but i still feel i NEED to put this one together first, if for no other reason than to follow through. however, i suspect it will provide some good and interesting data if i can just gain the needed wisdom to extract it.

yes. in fact the Rx8 has the latest closing timing of anything mazda has ever done @80. even the P port closes @75!

lmao! i remember when i put a degree wheel on mine, it was an "oh" moment. both ports are open together a LONG time... its like oh i know why its pissed off.... if you take the trailing plug out, and look in the intake, you can see light....



although it actually is kind of a sweetheart, it runs a lot better than i would have thought

In boost the pressurized air should force the exhaust gas out faster rather than sucking it in right? Or am I completely off?

i think the one factor most people overlook here is Exhaust Manifold Pressure ( EMP ) V boost pressure ratio

in most old school turbo's used on the street you would have a factor somewhere in the 2 or 2.5:1



-- no typo,, exhaust pressure is TWICE that of the inlet pressure in many turbos on song

if you are VERY good with exhaust, turbo manifold and wastegate and turbine choices you MAY get some near 1:1,, but never better



just a little bit of thought will tell you that the inlet and overlap period in some engines is now going to amount to exhaust gas dilution of the inlet charge

this is where a lot of people fail to cross the critical threshold of understanding the fundamental differences in turbo and NA flow dynamics



anybody who understands the concept of a miller cycle engine should now start to understand there is efficiency GAINS in having a late close inlet and a boosted manifold

somewhere there is a mazda SAE paper showing you the rise cycle of compression pressure in the rotor with the various inlet timings

they are radically different between late close and early inlet timing practices ,, the late close is easier on the the mechanical effort required during the initial compression stroke and has a radically faster rise in pressure during the final degrees of the crank during compression

this has implications on flame speed and ignition timing that few take the time to try and understand fully

and so the whole argument gets much more involved than appeared on outset of the OP's questions





basically a low overlap is better to reduce the exhaust dilution effect of the inlet while under adverse EMP/boost ratio

basically a late close allows the miller cycle effect to kick in,,, where boost won for "free" mechanical effort from the exhaust keeps the inlet in positive flow against compression late in the inlet stroke

and the win win is in the crank,, where it doesnt have to lose mechanical effort to do the initial stages of compression

,, effectively having an easy effort inlet stroke at the expense of the energy already lost to the exhaust

whilst this wins a radically different compression ratio rise in the compression stroke and thus demands a timing rethink due to that influence on flame speeds



i hope that comes through clear as mud ,, even if you have to reread it a few times

I agree, but lets keep this discussion technically correct. Without measuring its just speculation. Also we don´t know at what EMP/IMP ratio things start getting really detrimental on given porting. Its clear that stock port will be most tolerant and full PP will be least. Of course EMP on given inlet boost goes up with RPMs.





This is wrong.



Turbine is propelled by heat, flow and pressure. Heat is something what rotary doesn´t lack. And flow and pressure drop... Small turbine will pass certain amount of corrected gas flow and will work with higher pressure drop. Bigger turbine will pass more corrected gas flow with less pressure drop. Main thing is that they will produce same torque for propelling compressor.



Rice Racing, and not only him, datalogged that on proper setup, EMP is just catching up with inlet boost towards max power RPMs. Also its not just matter of properly designed hotside - side of thing, but whole package including compressor and intercooling efficiency.



This is something what should be examined much more. For me personally, I would be interested in how much power is rotary engine able to extract from given compressor-airflow compared to piston engine with big enough hotside.