I'm wanting to make a custom manifold for an N/A 4-port 13B, and I was wondering if an 86mm mustang TB is too big? (is there such a thing?)

13BT, 9.7:1 Rotors, 3.5" CAI, Big Streetport, Big Exhaustport, Tuned Header, Full Exhaust w/ cutout behind the header. Being run by a MegaSquirt & S3 Dizzy.

 

:sigh: bump

 

Drawing would be useful. If you are building it similar to the design on the SDS site With a single throttle I would recommend a little smaller. 60-65mm would be spot on IMHO. 86mm is BIG

(This isn't how I would do a custom inlet, but that's another story)

 

Happen to have a link to SDS?

 

http://www.sdsefi.com/techinta.htm

 

Next step... calculating plenium volume, runner length, and exhaust runner lengths.

 

Well, assuming you haven't been to bed tonight I'll try and drop some notes on this subject over lunch.

Bill

 

Also... If making a manifold that can utilize stock fuel rails... but replacing the PD with a stock FPR... and running in paralled.

Would you run both vacuum lines to the secondairy runner? Or the Primary FPR on a primary runner? (BTW, I'm keeping injectors in their places... although running them from the same spot WOULD let me stage the rotors instead of the injectors.... something to think about.

Also, on a custom Mani. I assume things like the brake booster, intake air thermo, and any other things would go into the Plenium, correct? ~CE

 

Ford Motorsports had a 86 mm TB under the SVO division. It's probably the best designed one I've ever used compared to the rest of the same design. One of the best feature was the dual ball-bearing sealed shaft.

 

Aside: if I were doing it (and I will one day) I would use a set of TBs of a GSXR 600 (or like) and run an IR setup.

Back on topic. anywhere behind the throttle plate should be OK for brake boost and map feed. You may have to put a damper on the map line (AKA lil plastic inline fuel filter.)

In terms of runner length, this depends how you are going to do the resonant tuning. (Need to find some notes on this I have lost as 99% of the tuning guides out there do not take the rotary into account, so the equations don't always work).

 

go to other rotary and check out gambone

 

Hi Gambone,

Had a look. Great fabrication ( I may try that tip on flaring if you don't mind). Concerned about how small your plenum is though. I like to have them at least 3 times the engine capacity, or at least as big as will fit. Wondered if you were using some resonant modes I hadn't thought about.

Bill

 

I like how he plugs himself

I've seen the manifold gambone. Unfortunatly I'm not as good @ flaring as you are. I've been looking around for flaring dies so I can flare the ends of the runners, but with little luck.

Also, I was wondering the same thing as Bill... kinda tiny plenium... ain't it?

 

I think 86mm might be too big for your application. What type of porting will it have? It might be ok for a bridgeport or more extreme...

Just as a side note, many high performance turbo 13B's (over 400 rwhp) are upgraded to single 75mm TB.

 

Yeah, I'm looking for a 70mm, but I won the 86mm anyway. I may be able to do some wheeling and dealing to get one locally.

 

I'm 95% sure that's what I just got.

A pity it's too damned big to be of much use to me.

 

follow ansersr to mr bill-shurvinto & liuid anarchy, porting is as big as it can be made with brakinf thrugh and plenum size was base on what was laying around,throttle body size I worked at a dealer ship (warenty) and it will out pull a 3rd gen and you gussed it the dealer ship was a mazda/isuzu so I had the chance to get the feel of all the RXs, one of the problems I'm haven is fuel it runs out to fast , so I'm now putting on a aux set of nozzles

 

I found a site which givees a good amount of info for V-8's. If you double the displacement it gives ballpark estimates for a rotary. By my figuring: For a 13B spinning at 8000 rpm with a 90% Volumetric efficiency and a maximum air velocity of 180 feet / minute you need a 2.378 inch opening (a 60 mm throttle body).

this is straight from his site (http://www.grapeaperacing.com/GrapeA...ehelmholtz.cfm)

This is the easiest to figure out. The velocity in the plenum intake pipe should not be higher than 180 ft/sec at maximum rpm. The formula to figure out the diameter pipe that should be used is for a given velocity is:

D = Square Root of (CID × VE × RPM) ÷ ( V × 1130)

Where:
D = Pipe Diameter
CID = Cubic Inch Displacement
VE = Volumetric Efficiency
V = Velocity in ft/sec

If you're dealing with liters, change CID to liters and the constant to 18.5 so the formula will look like this:

D = Square Root of (Liters × VE × RPM) ÷ (V × 18.5)

An example for a 153 cubic inch 4 cylinder with a 85% VE, revving to 6000 rpm would and a desired 180 ft/sec air speed though the intake pipe would look like this:

D = Square root of (153 × 0.85 × 6000) ÷ (180 × 1130) = 1.96

You would need an intake pipe that has a 1.96" inside diameter to have 180 ft/sec air velocity at 6000 rpm for that engine. In other words the engine would need a little over 3 square inches of intake pipe area.

Hope this helps.

-Trent
(I've put a link below)
www.grapeaperacing.com/GrapeApeRacing/tech/intakehelmholtz.cfm

 

Follow up:
I think the stock throttle bodies are 35mm in diameter, so that gives 961 square mm of area. Multiply by 3 and you get 2883. A single 60 mm bore gives 2826, so they are basically the same. So, according to the data I posted above, the throttle body doesn't appear to be a restriction. The restriction must be somewhere else in the intake. Hmmm.

A 65mm bore gives 3317 square mm of area, so if you need more flow than the stock setup can provide, a 65mm would be a good bet.

hope this helps too,

-Trent

 

Chances are though that with the engine being modified and turbocharged the volumetric efficiency is well over 90%

 

Keep in mind that a 4-stroke piston engine only fires HALF of its rated displacement per revolution of the output shaft. A rotary engine or 2-stroke piston engine fires ALL of its rated displacement per revolution of the output shaft. Therefore, when using formulas intended for 4-stroke piston engines, you need to double the displacement of the rotary engine before entering it into the formula.

 

Who said anything about turbocharged?

 

No one, that's why I mentioned it

 

The stock FC TB size is 45mm X 3. The FD is 50mm X2 and 45mm X 1.
You cannot just base the flow rate of a TB based on size only. The entry angles, length etc. have a great effect on flow.There are size TB's that don't flow the equal same. Plus a lot of manufactures base their flow rate by different methods. You also have to take into account plenum size when choosing a TB.

 

Well Cris... care to indulge?

I still haven't found any really good formula's for intake manifold runner length, plenum volume, TB size, or exhaust length.