geckospec

why are carbs such a popular thing on this board? is there no decent engine management available for the rx7? can you guys use mega squirt?

razorback

carbs are relatively easy to tune and less mess. and yes we can but we have to use the ecu for the timing or get a first gen dizzy

casio

seems like a cheap simple way to make power (though to someone like me, it wouldnt be that simple; a lot involved).
there's plenty of standalones (haltech and microtech being rather popular); they don't have to be "rotary specific;" they're standalones!
i believe a couple of people are using megasquirts.

razorback

someone has a carbed turbo motor making 371 hp on 17 psi. he was going to haltech but used the car for temp purposes.

MARTIN

a good carb setup will run you the same if not more than most standalones... but then again, U get almost all the features of a standalone but with out the wires..
plus tunning is not hard at all, and if you dont know how to tune the carb yourself
there are tons of people out that are able to tune it.... The only upside I see to a standalone is the fact that you can have multiple maps for several setups.. unlike a carb you have to retune. And starting the car when its cold is a bitch.... if you want more info, ask those who have used both.

totallimmortal

also some racing sactions require carb engines

Aaron Cake

iTrader: (1)

Because they don't understand fuel injection, and/or think that a carb will make more power.

Also, moving to Rotary Performance...

Evil Aviator

^ These are the two main reasons plus:
3) It is easier and cheaper to make a ghetto junkyard carb setup than it is to make a ghetto junkyard EFI setup.

Also, to expand on not understanding EFI, it is better to use a carb if that is all you know how to tune.

Yes, but a standalone EMS that is not rotary-specific is not able to run split leading and trailing timing. Also, not every standalone EMS will work with every model of RX-7 because some of them are "plug & play" or "plug & tune" which requires a generation-specific stock wiring harness. The term "standalone" means that it works independent of the stock ECU, but not necessarily independent of the stock wiring harness and sensors.

hondah8er

A good carb with run you the same if not more power then a standalone EFI? I dont think so....

von

Isnt there an EFI setup that has 4 individual throttle bodies? I think this is a 5000$ setup and suppose to yeild the most power. 280+ rwp bridge port...Awsome ****. I think thats considered a carb/efi dont know

680RWHP12A

because carbs are the ****!!!!!!!

happy new year!!!

rotarygod

iTrader: (1)

You can make great power either way. Personally I like the fact that I don't have to rejet a fuel injected car for cold weather or higher elevations. I have a Megasquirt that I built. I was intimidated at first but they are actually pretty easy to use. I don't know why people say efi is so difficult. They aren't that bad. You don't need a dyno to tune one any more than you need a dyno to get a good carb system running good. I had played around with the idea of running a carb but wanted more options. The biggest deterrent though is that I don't know how to properly tune a carb. You can do good either way. I personally see much more inherent potential available from efi but that doesn't mean carbs are bad. They've been making tons of power for alot longer than efi.

I think the best thing about a carb though is the fact that if your car has a problem, it doesn't take long to figure out where the problem is. EFI can have problems in many more places that are harder to diagnose. A faulty wire for instance.

BASTARD

iTrader: (4)

Carbs are for losers...Hahahaha. No seriously though they are for losers. I would much rather have the benefits of a self adjusting (altitude, temp, speed, load...etc)EFi system then have to "re-jet" a carb...Er-umm what track is that...oh yeah i need to rejet the carb or i'll blow my motor. Much easier to swap a file or better yet having to pull apart the carb to "rebuild it"...silly rabbit tricks are for kids. EFI is the only way to make real efficient reliable clean accurate power...any how different strokes for different folks. Do what ever makes you happy

peejay

EFI isn't as self adjusting as a carburetor. You have to *tune* the EFI to suit, the carburetor is largely self-compensating. You only *have* to rejet when you do stupid things like tune it at sea level then drive it in Denver, or vice-versa, and then you only have to go a couple sizes one way or the other.

EFI is nice, and I want it for my '85, but here is what I am looking at:

Fuel injectors (probably 4x480s, so about $100-150)
Fuel pump (about $50-100)
MS computer ($200-250, I dunno?)
Big twin throttle body (about $40 from a junkyard, comes with TPS and an IAC even!)
Laptop computer (another couple hundred)

Or I could just get a $50 performance carb fuel pump and a $75 used carb, if the Holley I have proves to be too large to work well. No worries about accidental holes in the fuel map, or lots of time tuning it up from scratch. Jets can be had fairly cheaply, too.

Note I didn't mention intake manifold - that is going to be fabricated no matter what.

grantmac

Peejay: You're going to be using the Ford truck throttle body that I was posting about a while back? I think it's got some serious potential.

I decided to go with a Megasquirt system for a few simple, not really performance oriented reasons. One was that I wanted better fuel economy, two was that I wanted a little bit more power and the third was to avoid the fuel starvation that my carb sees in long left-hand turns.
I'm building my set-up totally junkyard, the only new component will be the ECU itself. The whole project is going to be fairly cheap. I'm going to be converting my stock Nikki to a throttlebody and then running 4 injectors in the stock manifold. I don't expect much more performance, but I won't be surprised if I get it.
I was going to go with a downdraft weber, but I worked it out and over a years worth of running around at 15 MPG the EFI was actually marginally cheaper.
Grant

peejay

I didn't see it. But it's noce to see that other people have the same idea... It's an idea I've been kicking around for some time now.

The TB on the 4.9 appears to have 44mm bores. I haven't had opportunity to sample a 5.0 or 5.8 yet to see if they are different... for some reason everyone has the 4.9 six. (Actually the reason is obvious - the six kicks butt)

But if you caught my intonations, I am *not* going to be using it... why? Because the EFI setup would cost more than the rest of the car's alterations combined. It's not economically sound.

grantmac

Ahh, I know the 5.0 one has 50mm bores actually; I was gonna use it! I may have made mention of that on the msefi.com forum, so you probably didn't see it.
I can understand not going EFI for the initial cost, or if the car is for track/fun use only. I drive mine through the city on a regular basis to work, the fuel savings would be worth it in the long run for me. It's not that it gets bad milage with the stock carb, it's just that it would stink with an aftermarket set-up.
The only problem with the Ford TB is that it doesn't have the correct bore spacing for a weber manifold. If some enterprising person were to make a Ford-Weber adaptor with injector bungs in it I think they could make some decent coin. The 12A doesn't have a very large assortment of EFI goodies, and the ones it can use are rediculously expensive (TMW; pretty but steep). I was going to hack my IDF manifold but I just couldn't bring myself to do it, an adaptor might still oneday be used however. I'm going my current route for cost savings alone, that and I'm not certain the overall direction I'm gonna take with the car.
Grant

peejay

50mm bores eh... that would be too large for my mini-port, but it'd be just peachy for a bigger port.

Throttle bore spacing only matters if you're trying to mate it with an existing manifold.

Picture a fabricated dual throttle body manifold using a pair of the 4.9 throttle bodies.

Now picture a similar manifold with the 50mm throttle bodies, on a four port engine in an FC using the stock EFI.

grantmac

There is a guy on the MS forum running 50mm TBs on his streetport 12A, he says it does just fine for low end. I imagine the 44mm would be great on a stockport though. Fabricating a manifold wouldn't be hard, and I think you could have a market with them; seriously. With the number of people who are interested in an EFI 12A set-up I think a low-cost set-up would be great. There was someone (V8Kilr I think?) who was going to make a new LIM to bolt a T2 UIM onto a 12A, but that is waaay more complicated then this would be and he's sold the design. Since these Ford parts are cheap as chips it makes sense to use them in a budget build-up. I personally think that 50mm bores wouldn't be too big for a 12A, even a stockport; EFI isn't as sensitive to TB size as a carb is.
Grant

KNONFS

iTrader: (14)

A FULL carb conversion WILL make more power than a stand alone by itself.

rotarygod

iTrader: (1)

Just curious why you think so? A carb always has a slight restriction in it where the flow area through it gets smaller. It's called the venturi. I know both systems can make great power but I would never say that one WILL make more power than the other. All things being equal, a fuel injected system SHOULD (not will) make more power and it SHOULD be able to do it over a wider rpm range since there aren't as many manifold design limitations.

bill Shurvinton

Yup. I sold him that. Put the other one on my 13B ( got a good deal on a pair of 50 DCOE pattern TBs). Works great, but to be honest for a street ported engine 2 45mm bodies is more than enough.

My setup is a little extreme compared to many...

grantmac

Well the 44mm Ford TBs are even more available then the 50mm ones. I believe they all have the same bolt pattern and spacing so a manifold could be made to accomodate either one. The only problem I see is the inability to use airhorns. Unless they were put-on without a flange and just hose clamps. That and the airbox would be a custom affair.
Grant

KNONFS

iTrader: (14)

The secret is:






The intake manifold

rotarygod

iTrader: (1)

I kind of figured that's what you were getting at.