FAST87T2

im in the process of build a complete custom intake manifold, the one that i have designed has a 1300 cc surge tank, is this too large, i was planning on using the stock throttle body so that kinda locked some of the dim. i had to work with. is there really a big advantage to using like a mustang throttle body, also i was planning 1.5 dia. runner are these too large?? As far as the mat. i plan on using 18 ga. s.s. and s.s. runners. i would fab the whole thing out of alum. but i have only been tig welding for about 2 years and i am not confident enough in my alum welding skills. the runners will be mandrel bend due to the fact that i also run a unison breeze cnc mandrel bending machine. it also helps that i work as a machinist/mechanic for a living.



the picture attached is the mandrel bender.



thanks

--joe

sen2two

there is a fabrication section now...maybe you should post this there.

j9fd3s

off to fab.....



the factory tb is staged, you loose that if you go with a single tb. so you'd be loosing response in the low throttle opening/lower rpm range. if you're not going to drive it there, then its not important.

teknics

I personally was referred to a book all about manifolds and how to figure out your needs based on calculations. Ill try to find the name of the book, manifold fabbing is another area of fab I would like to get into, theres so much untapped power in these rotaries that is restricted by the stock manis.



Random throw out here, someone was posting a nice 20b for sale with a hogan racing intake manifold on it. from the looks of it they used aluminum plates and made square runners, or at least they look square. I would assume with the appropriate design on where the air enters and where it exits the mani that square runners might work.



but ive never designed a manifold before, only imagined at this point.



velocity stacks FTW.



kevin.

sen2two

i am going to welding school myself, and have self taught myself a good amount. and what i have learned is, if you can TIG stainless. you can do aluminum. just practice some lap weld joints on sheet of 6061 aluminum. then go for it. it will be lighter and dissapate heat more. i think S. Steel is more exspensive too???



are you building this for NA or turbo? track or street? if its track, road or quartermile? these will all determine runner length, diameter, plenum size/shape, and TB size.



a good idea for the runners is to start long. and if your powerband isnt where you want it. chop it down and go from there...



i would use an aftermarket mustang TB. they have a bunch of different brands and sizes. and the TPS easily wires into rx7 type TPS harness. theres no real junk on them either. they clean up real nice...

mazdaspeed7

ITB's reduce the effect of reversion and charge dilution allowing large ports to be more streetable than the same port with a plenum. Same applies to piston engines, and pretty much everything that uses big cams(from the factory) has ITB's. BMW M cars and sport bikes are great examples. My bike is perfectly livable around town at 2-5k rpm while the torque peak isnt until 10k, and the power peak around 12k. A good example to the contrary is old school cammed v8's. The inconsistent idle and absolute dogs below a certain rpm.

ColinRX7

Why did this get moved to fab?



I left it in rotary build on purpose so some intake manifold tuners could help him decide on sizing. But oh well, hopefully they will see it here.



As far as building this thing goes, I'd like to know if you're N/A or turbocharged, what type of port work you're doing and what powerband you're looking for. That setup sounds great, but how long were you making the runners? Bends? Is this still a side port motor?



Stock ports, inch and a half runners for primary and secondaries sounds excessive. But again, depends on the other details.

FAST87T2

the motors that this intake will be on is a s4 6-port with a full bridge and twin garrett t3 50-trims ( i know they are kinda small and i realise the power will top out at about 400). the car is going to be set up for autocross another reason for the smaller turbos. yeah ss is more expensive but i am much more confident in my tig skills with ss as opposed to alum. plus ss has a better heat rejection quality then alum. from what i have gathered is that a single plane plemum with a mustang style TB would be just right, the plemum size will be about 60% of the totla dis. of the the motor, and as far as runners go i belive if i use 1.5 all around i should be ok and considering the forced induction im not gonna worry about port tuning them due to the fact that there will aready be a high pressure area behind the port for when it opens. but if any of this is wrong please feel free to correct me. any help is more then welcome



--thanks

joe

j9fd3s

i moved it cause he was FABBING an intake, we can slap each other with fish later....

ColinRX7

No worries Mike



What size is the mustang style TB anyways? It sounds like a really cool setup, I'd be curious to see how quickly those turbos produce pressure (what RPM). With 1.5 runners for each port the flow of air will be slow at low RPM, but only while it's not producing boost. Autocrossing won't be a problem though, you're up in the revs anyways. I could see it lurching on you at take off but, I could be wrong.