j9fd3s

i know. i agree. my weber was probably more than your whole EFI setup.... and i still need to spend another $50-60...

j9fd3s

so i feel i have learned a bit about drivability on these engines.



1. it does not like intake manifold vacuum. due to the good connection betwixt the intake and exhaust ports, any intake vacuum will just suck exhaust up into the next intake stroke (@low rpm), which = misfires and bucking. i drilled a hole in the throttle plate, and it makes a HUGE difference in drivability. i can't find the section, but the "rotary engine" book also suggests a dashpot, and i believe it might help.



2. AFR's. at part throttle a side port engine will basically run the same from 15.5:1 to 10:1 afr, and out side of this range it just stops running. with the Peripheral port this is likely to be also true, however unlike the side port the peripheral has a narrower range where it will run without bucking/misfiring. this range at low rpm part throttle seems to be in the 12.5:1 to 13.8 range. richer than 12:1 gives very bad drivability. going leaner, 14-15:1 drivability also decreases but it is not quite as bad as being too rich.



3. the AFR numbers are ballpark measurements. due to the overlap/cyclic misfire the meter does not read correctly at idle/low throttle openings.



4. i have not yet adjusted timing, it is locked @18 with zero split.



5. the Rx8 spark plugs are the same design as the racing spark plugs, but in a "street" heat range, and thus are probably valid on a street car, where time @wot is small

Kapn.K

Great thread! I've always wanted to try a pp on the street. I ran a 12a bp in an old 1st gen I used to have. Most people advise against either. I bought a '92 b2600 extended cab b/c I needed a little truck, like the old body style, and needed a mazda to put a rotary in. I would like to get a blown donor s5 and use the suspension as well(maybe put some panasports on it). It would be cheaper to put an s5 turbo motor in it(and be loads more practical) but I WANT BRAP, BRAP!

FC/DTP

at what degree should a pp intake start and end at 2.125 wide to have peak power from 5-9k, also what size 4 barrel carb would be recommended 650cfm?

sen2two

I'm building a "street" 12a PP right now myself. But I'm using a 51 IDA Weber. Deciding on the size of the PP is my problem right now. I was thinking since I'm using a 51 IDA, why not make it just slightly smaller to keep velocity up. I was thinking a 45mm ID (about 1.75") in more of a rectangular shape with a rounded open edge. Similar looking to the stock exhaust port shape.

j9fd3s

i think a 51 is about the right size actually.



carbs like a choke that is about 80% as big as the throttle. 48 x .8 is 38. on the PP engine we run a 43mm choke, and actually the port runner is about 43mm too. so 43 x 1.2 = 51.5...



so in theory a 51 IDA seems like a better choice.

sen2two

I'm debating on putting the PP hole at an angle , or directly in like the MFR housings. The major benefit of the angle to me is getting rid of that hard 90 degree bend for the intake runners.

j9fd3s

yeah i actually wonder about running a side draft carb, if there is room it seems like it would be better?



although the 90 isn't that bad, you can use a big radius

sen2two

I thought about the sidedraft as well. You can get a 55 dco from Weber brand new for $400 I believe,Bigger than a 51IDA and half the price. But limited space means limited runner length. Really cuts down on options when runner length can be such a huge deal with PP motors...

j9fd3s

had it at the track this weekend. its FUN!



i wanna DD it!



it feels like its making about stock 12A power by about 3k rpms, and then it STARTS pulling, tq peak's about 6k, i'm blaming the stock 12A air cleaner. the air cleaner might limit power, but it does fool EVERYBODY, so it can stay for street use. i get asked if the engine is stock all the time, which is funny cause they are usually standing on the side where you can see the filled in stock intake ports





the issues.



temperature makes a HUGE difference. the difference in power between 75C and 90C feels like 30hp!



2. i checked the mixture with the WB, it said mid 11's, which the engine and i* were happy with, however the mufflers didn't like it... the paint is GONE mufflers are broken.... exhaust 3.0 will be the next step, after a radiator that works







* the PP seems to be a balancing act between what it likes and what i like. for example, i we both were happy with mid 11's afr. however i'm happy with mufflers, and the engine is not....