Turbo1

I've been trying to sell this newly ported (by BDC) half bridge motor now for around a month....and have gotten zero serious interest.

Since I'm not going to just throw away the money I spent (getting offers for less than 50% of what I spend on new parts!), I'm seriously thinking about using it/building it.

I'd really like to stay naturally aspirated, for financial reasons mainly. With the half bridge, what kind of power could I get out of the motor assuming it was running in a street car?

I'm thinking locost super 7 project, but I can't deafen everyone within a mile radius every time I drive it.

200hp? 250hp? What do you think?

BUMBLEBEE7

iTrader: (1)

Is the motor put together? or are you selling plates and housing?
price and detail on build.

Turbo1

My FS post is here: https://www.rx7club.com/2nd-generation-rx-7-1986-1992-parts-194/bdc-half-bridgeport-13b-motor-more-879052/

Motor isn't put together, just have the plates/housings as recieved back from BDC awhile ago.

I know the motor itself was almost 750, and the porting cost me 750, plus the extras I was including, etc. Anyway, this isn't a FS thread/I don't want to get banned or anything, but it's linked above.

Just wondering if a half bridge 13B would be a good candidate for a locost super 7 car, or if I'd be better off sticking to the original BEB (Bike engine build).

gawdodirt

We ran a 4 port with street ported primaries and bridge secondaries using a Holley 650 double pumper and had very good results. You have to get used the transition point but it was docile on the primaires but had more top end than a complete street port. The down side was that it had less hp than a full bridge. But you have to use a carb like a four barrel where you can manually request the transition and be alert enough to NOT press the throttle WOT when you need torque.

Over all, in an Unlimited Class 2 car of years ago, it was the shiz.

gd

ultimatejay

iTrader: (1)

Half bridged motors period is a waste IMO, especially in N/A motors. Just finish the bridges on the other irons and put it together, if not sell it.

BDC

Heh, heh. A "waste", huh? Could've fooled me.

B

gawdodirt

Wow. Great contribution. Very positive.

The engine had better drivability than a full bridge, and since it only had idle circuits on the primaries, it idled half way decently.
The bridge port pattern was the CNC'd MFR bridge that did eat into the water jacket. Not some '"eyebrow."



gd

el_rotary

iTrader: (3)

To say half-bridge motors are a complete waste of time is a little far ultimatejay. Didnt you compliment me on my video/current set up a couple weeks ago? Im runng a half-bridge 6 port block with it being turbo though.

In your defense though, you did say it was IMO

nillahcaz

iTrader: (2)

any thing after a slight street port you cant give a round about power output, with that amount of overlap the numbers are dependant on intake and exhaust design.

ultimatejay

iTrader: (1)

Well, I guess I'm used to all out power and don't think about street driving setups, although I have a huge tolerance for daily driving standards as I have had a full bridge daily driver for several years and had no problems while other people whine like little bitches. So the real question is which one are you?

Bitch- streetport or half bridge

A real man- full bridge or pport.

el_rotary

iTrader: (3)

I guess that makes about half of this community bitches. Im not along ....yay!

I was trying to be subjective to what your first posted but I guess you have a mind set on this subject. Relax my friend. Nobody is trying to attack you!

Back on the subject, put it together and have fun with it since you have it already and invested the money. If you dont like it for whatever reason you can always sell it. Power wise, im not sure...try it out and let us bitches know.
Ricky

BDC

I guess I now know what that makes me.

B

rotarygod

iTrader: (1)

You do have the hair!

ultimatejay

iTrader: (1)

Hey guys, when you see these smilies , that means someone is joking around. Take it easy, I'm just playing around. If you like half assed bridged motors then that's all fine and dandy.

gawdodirt

Really? then you won't be screwing with a Bridge port anyhow. Or a 12 A for that matter. Right? I mean, unless you actually race and the sanctioning body requires it for your class.

But we all have our desires and they usually don't fit anyone elses. And that's cool! Hell, Some guys race Methanol Briggs and Strattons!

On building it and "having fun." You might get more money out of your project if you part it out and not build it. So, take a moment and identfy your goals and see if the parts will help you get there.

gd

nillahcaz

iTrader: (2)

I had to do a research paper on fluid dynamics and picked airflow in rotary engines, what i found lead to over 100hrs * not alot if you think about it... less than a month of day job time* of designing intake ports and programming them into mastercam, Finding that you can get more flow when and WHERE you need in the chamber using a smaller than "Full bridge" size port. I ended up with a lot more area under the line *more average power* with a port shaped like a squished primary port as a bridge. I also found that a radius on the port edge was more than useful, Not in peak power but in engine efficiency but this has no relevance to this thread.

[thepoint] just in most every thing more is not better, there is no way you can make me believe a full bridge car will always be faster than a half bridge. I'm sure your girl *or what ever you are into* would rather you be an inch shorter and work all the time than look like a **** star but it only work once a year. [/thepoint]

RotaryPicha

iTrader: (2)

+1^

Turbo1

I want streetable power in a sub 2000 lb car (locost super 7) without blowing out my eardrums and everyone else's.

I was going to sell it, but I have 1500-2K invested in the parts, and I'm getting offers for $400 for the housings, 200 for the irons...keep in mind there is 750+ worth of professional port work there. Thats why I'm thinking putting it together and using it would be better. If it needs to have the intermediate housing B ported, BDC can have some more $$ and so be it.

A turbo rotory locost super 7 would probably be a bit "too much".

ultimatejay

iTrader: (1)

You're kidding right? You mean you can't understand why a full bridge port motor will make more power than a half bridge? If you can't understand that, then your right, there's no way to make you believe because you don't have a clue.

drewski86

No one can make you believe that being able to fit more air/fuel into the combustion chamber each cycle will allow you to make more power? Are you sure you're comparing half bridge to full bridge and not full bridge to J bridge?

Turbo1

He didn't say more power, he said faster car. Depends on the aplication really... for a road race car it might be faster to have more torque and a broad range of power instead of a short RPM band of high power with little under it.

Correct me if I'm wrong, but porting is similar to changing the cam and cam timing in a piston car. Too much power = too much cam, and just like in a car with rods, a broad powerband is often much faster than a car with too much top end.

Back to my OP though, any idea what a sub 2K pound car would run like with a half bridge NA motor in it, assuming it's muffled enough to keep from summoning cops from 2 zip codes away? NOT a drag car, a autox/track day machine that I can have fun with on the street as well.

nillahcaz

iTrader: (2)

You're kidding me right? you don't understand a bigger port will lower air velocity at lower rpm and give more overlap that is detrimental to making power? *even at high rpm, overlap is way overrated for high rpm performance* I NEVER said a full bridge will not make more peak power, peak power is for people with no working knowledge of cars or are trying to compensate for something and has little effect on making a car fast, a fixed speed prop plane yes, but not a car.

did you or Jay even read my post? For the love of God don't tell me the Rotary Performance section is going the way of 2nd gen specific.

WOOT some one did actually read my post. Yes, the port size and shape are as close to lift, duration and separation as you can get in a rotary. Unfortunately a lot of people ignore port shape and go for as much area as they can get, Lets say a V8 with cam A with separation of lets say 106º might make power from 3k to 7.4k rpm now you swap that cam out with one from the same manufacturer with the same lift and duration but a separation of 110º and it will make power from 2.2k to 5.5k rpm, you can do the same with a rotary by changing the shape and location of the intake and exhaust ports.
Lastly, again its hard to say what your car will do with that engine with no other info on intake, exhaust and fuel management tuning ability, but you should have no problem setting it up to walk all over a stock TII all day every day and have more throttle response than a TII could ask for. BDC is a great place to get work done, If I did not have the ability *or if i ever get lazy* BDC would be doing all my work. I promise you that unless you are a die hard turbo brat *not a bad thing* you will be more than happy with the engine and how it drives once it has a good tune.

Jdrift

Jesus Christ you guys. Not only did I laugh my *** off, but i'm dizzy as hell too. I was never good at math in school. hell I never liked school. I'm sure if I ever take one of these routes, i'll explain my goals, and pay someone to do the work. I'll drive the car k,thanks,bye. lol. Seems like most of you know your stuff.

diabolical1

iTrader: (3)

well, here's my opinion. get your grain of salt ...

you're probably not going get what you paid for it from BDC because the people that can afford it would probably go to BDC directly and the others, well ... they're going to look for the BIG deal! it's that simple. as was said by nillahcaz, if i didn't do my own work, BDC would be high on the list of people i'd turn to (Kahren and Ray at PFS would likely be the only others) so it's not that i don't think it's worth what you're asking (i read your for sale thread), but it's just a reality.

the fact is you will have to choose between sound control and tuning the engine to it's potential. it sounds like you've chosen sound control. i'd say just build it and be prepared to sacrifice some of the power for the muffling you desire. i've definitely become less of a fan of the half-bridges over time, but i think they work just fine.

to get an idea of sound you can look up the user trochoid ... he is the only non-turbo half-bridge i can think of off-hand. for what it's worth, his is (was) a 12A. there should be some video clips floating around of his car at a local meet he attended a few years back.

Turbo1

After looking around more, it makes no sense to NOT turbo this motor. Unfortunately, to build it right, it's going to run me another 1500-2000 worth of parts, assembly, engine managment, turbo, etc...and thats if I find deals. There really is no benifit to me (other than being different) for putting a 13b into the locost.....it just needs 2-300hp to be a kick *** fun car. What it doesn't need is to become a money pit, which is where this is headed.

I'll be sticking to the tried and true 4g63 for the locost build. $1500 total = bulletproof 300 turbo'd HP, and quiet if I need it.

If I come back to triangles, I'll just order up a fully built motor from Brian and drop it in

Thanks!