rx7freak13v

hey guys,

so i have definitely decided to go the big boy badass pp route instead of a bridgeport. im glad you guys helped me make that decision.

i have some ideas and questions about the angle of the pp through the housing along with an intake design.

mfr cut the pp at a 90* angle straight through the housing where rb cuts the pp in at an angle. anyone have any idea which is better and why?

next question would be, if im running 60mm efi throttle bodies that taper down to 55mm at the base, i will be forced to tune with alphaN correct?

what could i do to allow me to tune with speed density?

i thought about adding an intake plenum around the throttle bodies and using a vacuum port from there to the map sensor but i am not sure if that would work (the air box is necessary to reduce intake noise as this car will be daily driven)?

i had even thought about just building an air plenum and running the pp runners straight to the plenum and use a large throttle body at the front but i couldn't find any info on if anyone had done this?

just throwing ideas around trying to figure out what i should do? i would prefer not to tune in alphaN if i can get around it.

im planning to run 2 1000cc fuel injectors with a msII (if i tune in speed density) or msIII (if im going to tune with alphaN)

let me know what you guys think. bounce around some ideas with some pro's and cons and see what we can come up with.

nvmarx

iTrader: (1)

if your cheap like me buy some 2008 arctic cat snow mobile throttle bodies. 1000cc or 1600cc bosch fit right in it comes with tps and is 50mm, on the small side but its all you need for a daily bro. compered to any other itbs they are super cheap and can get them off ebay. take a look at my build thread for photos

rx7freak13v

im actually planning on gettig some rc51 itb's. they start 60mm at the top and taper down to 55mm at the base. im getting a good deal on them from a member on here. im definitely going to check out your build thread though.

thanks for the reply, keep them coming guys.

rx7freak13v

any have pics of their pp air boxes?

j9fd3s

iTrader: (3)

what's wrong with alpha-N? it works really well on an NA, and it really isn't any different to tune than speed density.

does the MS do sequential injection? and can you play with injector timing? i have a feeling those two features are what separates EFI from the carb

oh and if you can fab it up so that you can adjust the intake length, that would probably be good, although it might not be easy, mine hits the hood already for example

peejay

MS3 will do timed injection. Not certain if MS2 can be hacked to do it.

S1sevenNZ

Some pic's i found :

nvmarx

iTrader: (1)

that last picture is of ''aerosev''s 12app with a jetted niki carb i think he built it like that so he could fit the factory air box thing. he built my intake, coil overs and a few other things to

rx7freak13v

i must be bad at searching, i couldn't find any examples as good as most of those. thanks for posting them S1sevenNZ.

the reason why i would prefer to tune with speed density is only because by what i have read while searching basically says that alphaN is a pita to drive in traffic. unfortunately i can't find a lot of info on alphaN tuning for street use but by what i have read it is more race applications only. i would love if someone could chime in who actually drives a dd tuned with alphaN.

also, does anyone have any video of a pp running without an air box but with some filters instead that could show intake induction noise? by what i have read it easily get as loud as a properly set up exhaust and sometimes louder. i wish i would get away with only using filters, i love the look but have to keep sound to a streetable level. i know i ask for a lot. but it's so hard to find info on mechanically tuned rotaries, most people use boost instead.

thanks for the replies guys

John Huijben

iTrader: (1)

Most ecu's can do both, so I wouldn't worry about using alphaN or speed density, as you'll probably be able to switch very quickly. We switched a car over in an afternoon last week, just setup the ecu, and a few hours to redo the injection map. On n/a engines with a weak vaccuum signal (high valve overlap, big throttlebodies, or both) I would recommend using alpha-N. It's just easier to tune and driveability can actually be better than when using speed density. Depends a lot on your engine though.

j9fd3s

iTrader: (3)

john is right, switching from alpha-N to speed density isn't that bad. i like alpha-N on NA cars in general.

the last speed density car i did was a 56 chevy with a haltech, and it basically does all of its driving @1500rpm and one load point, so it was hard to get it right, because that load point covered hills and different gears and stuff, so it was either too rich or too lean. the V8 doesn't care, it probably wasn't running on all 8 cylinders anyways, but a PP won't put up with that.

rx7freak13v

wait i'm confused. i thought alphaN wasn't able to understand load differences not speed density, maybe i misread.

thanks for clearing up alphaN and light throttle/low speed?lower rpm driving. that was my only real concern sincing im planning to daily drive this thing. i understand why speed density is a problem with low vacuum high overlap engines. it makes since to me, but what i was reading is different then what you guys just stated. thank you guys for clearing that up for me.

ok so back to induction noise. how loud does the intake actually get when not using an air box?

does n air box really help quiet down intake noise?

what's the difference in throttle response between itb's with sock filters or an air box?

i appreciate you guys sharing your knowledge with me. it's really helping figure out what i need to do.

Jimbo II

Hey man you got anymore info on this car?

S1sevenNZ

Na sorry i dont, Just a pic i found while searching, It was on trade me.

j9fd3s

iTrader: (3)

basically with fuel injection there are 3 ways for the ecu to sense load.

speed density, uses a MAP sensor, to get intake vacuum. it works well on turbo cars, as it sees boost and vacuum, but on an NA with a small vacuum signal, its probably not great.

Alpha-N uses the throttle position as the main load signal, so its just RPM+throttle. it works great on NA engines, its even been used on turbo cars, although it doesn't see boost. the 787B is alpha-N.

the third is to use an airflow meter. the other two methods infer airflow, but an airflow meter actually just measures the airflow. most OEM cars use an airflow meter. on it would require a sealed airbox, and even then the pressure changes might do weird things.

traditionally the PP's run ITB's to keep the pulses from the rotors separate from each other, and all the factory race cars have an airbox over the trumpets.

i've never tried sock filters, i understand that they do not work very well just because each sock has to handle the instantaneous flow, and they can't. but if you mount the filter further away it can handle the overall flow for both rotors

the airbox does help with the noise, i don't have video or anything, but its pretty loud without the lid on it

rx7freak13v

thank you for explaining that to me. i'll make sure to build my plenum and make it sick! lol

im more excited about AlphaN now and cannot wait to get this engine done.

since im going to be using alphaN im also going to use 2 ID1000cc injectors so i don't have to worry about staged fuel maps.

you guys have really pointed me in the right direction. thanks guys

j9fd3s

iTrader: (3)

yeah 2 ID1000 injectors are what i would use if i was gonna go EFI

rx7freak13v

can i get some advice between a wrap around side draft style vs. an ida style for the pp? im curious on which size intake piping may make more power and usable tq?

and GO!

i've read that the longer runners help tq but most people use the ida sized runners. i was curious on why? and realistically, i know this topic gets covered over and over but how much power should i be expecting to get out of an na pp13b to the wheel with the exhaust at 100db?the more searching im doing im finding more and more people making 200rwhp+/- on their built pp 13b's once it gets to autocross trackable exhaust notes. can anyone please enlighten me? im feeling kind of down right now about the low hp ppl are getting after having a track quiet exhaust.

then i thought, well if im not satisfied maybe some low boost (8-10psi) could make me happy, but how reliable would that be? i know i know, i sound kind of No0bish right now, maybe i should stop reading lol.

S1sevenNZ

For exhaust, Have a read here : (12thpost down 1200wag)

http://www.ausrotary.com/viewtopic.p...haust&start=60

These guy's have built 13bpp's in the past that are around 300rwhp and exhaust's that are still quiet enough for NZ road's.

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Heres an exhaust sample for those that were interested in a quiet exhaust that doesn't restrict flow.

This one has twin 2in primaries into a 2.5in collector, then out into 3in.

Usually we'd make the rear muffler out of aluminium (not steel as shown), I found out by accident one day that alloy rear mufflers absorb more sound than steel or s/s,and they're much lighter. The best packing we've found for the rear muffler is ceramic blanket.

The resonators are stainless packed.

Using the correct perforated tube also helps. Believe it or not the perf tube on the left (thicker wall, with less holes) is quieter than the stuff on the right (thin wall, more holes). Common sense says it should be the other way round, but in reality it's not.

Steam pipe on the first header bend also helps a little.

Stainless steel tube or mufflers lasts longer but will make the system louder.

The rear muffler makes the biggest difference. If everything listed above is done AND an alloy rear is used it will end up being 95 db (13B PP). If a steel or s/s rear muffler is used it will likely be over.

And the longer the better. Typically a muffler 500-550mm long will fit in and Rx3.
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rx7freak13v

wow thanks for that exhaust thread, very nice. where would i find those mufflers at, any ideas? the rear muffler, hmm also aluminum...where do i find such nice things and where would i find ceramic muffler packing? im going to do a search but just in case i don't find exactly what im looking for and you have already located such websites

300rwhp 13bpp's that are street quiet siiiiiiiick. that was definitely the upper that i was looking for. ok, so im pretty excited right now.

so the other question was intake runners, ida style, side draft style or start at a 45* side draft where they are wrapping over the top but pointing towards the hood some instead of 90*?


ps: really S1sevnNZ, thanks a lot i was really getting kind of depressive thinking about how much money was going into this build and how how little hp was coming out of it. i know it probably won't get near 300rwhp but does give me hope for the 250-260rwhp range that i would give anything to achieve. you has given me hopes

j9fd3s

iTrader: (3)

i've posted the page from Mazda's SAE paper about intake lengths, basically the longer it is the lower the RPM peak will be.

and actually if you do something custom, it might be fun to make the intake length adjustable, so you can try some different ones and see what you like

fidelity101

iTrader: (11)

Thats the rule of thumb for any intake manifold runner length design.

j9fd3s

iTrader: (3)

https://www.rx7club.com/showpost.php...1&postcount=18

S1sevenNZ

http://manufacturing.mufflercentre.co.nz/rotary.html

Those guy's do ceramic packing, But you should be able to buy it from most exhaust shop's. Alloy muffler's need to be custom made as far as i no, Any engieering shop should be able to make somthing up for you.

No worrie's and good luck