I'm wanting to know what all's involved in going from an 89' FI to Carb'ed setup.

I know he'd need a new intake (Racing Beat), and carb (Demon, K&N) setup. What else is required, and would you need the carb w/ ford linkage? etc etc.

If anyone has an EFI~>Carb write-up, link or otherwise (couldn't find anything in the search).

 

Now why would you want to do that?



-Ted

 

I can see a few reasons for going carbureted. You lose a fair bit of weight and bulk in the engine compartment. You also simplify any troubleshooting in the intake system. with the right carb you shouldn't lose any HP. Might be interesting to sleeve the 5 and 6 ports and run them off a vacuum secondary on a small 4bbl. I think the biggest loss should be to MPG, but that cost is negated the first time you have to buy anything signifigant ($$$ parts) for a FI setup.
So why not?

 

Lose weight?&nbsp I'd bet those aluminum manifolds and throttle body can't weigh more than 30lbs maximum.&nbsp Add another aluminum intake manifold and carb set-up, and the difference is down to 20lbs at the most.

That's depending on the capabilities of the person doing the troubleshooting...

That is true.&nbsp In fact, removing the restrictive airflow meter might even gain more power if you know what you're doing with the carb.

Hmmm, yeah...I'd like to see the carb draw 25mpg+ on freeway driving.&nbsp Are you paying $1/gallon for gas?&nbsp The loss in fuel economy should be significant for a daily driver.&nbsp My problem is I don't understand what you mean by "significant ($$$) parts for the FI setup"?&nbsp The stock FI system can handle almost anything you throw at it - even a mild bridgeport if you want.&nbsp You talking about a $400 S-AFC?&nbsp The carb and manifold set-up is going to cost the same thing, if not MORE than the S-AFC...

I just did...



-Ted

 

Things in FI systems go bad, a lot more often than Carb'd setups. By the time 1 FI thing goes wrong ( AMF, Injector goes bad, etc ) You've paid for those $150 extra dollars in gas.

Even still, he's going carb'd ( We're gunna race, Carb'd 13B vs. EFI 13B w/ Mild Streetport ) and I STILL need to know the processes. Things I'll need, things to remove, things to eat WHILE adding removing. EVERYTHING! It WILL be done, that's not an issue. IT's HOW to do it.

Like converting an RX-7 to a V-8, if someone plans on it, they'll do it; and most of the time, even though we don't like it we'll tell them how, or point them in the right direction.

Ultimatum: Tell me how to do a EFI~>Carb conversion, or I'll go to V8RX7.com and do a Rotary~>V8 conversion!!!

 

I thought the stock EFI manifold was pretty restrictive? (i'm genuinely curious)

 

AFM's rarely go bad.&nbsp Used ones are relatively cheap.
Injectors rarely go bad, unless you're totally ignorant on keeping a FI system clean.

Now racing scenario...that's a whole nother ballgame.&nbsp I was talking about daily-driven, street vehicle...


-Ted

 

How much power you're lookng to make?&nbsp I'm assuming street application - these things won't hit 200hp on a daily-driven, street FC...


-Ted

 

I know of a couple N/A FC engines that are/were supposedly making about 200 flywheel HP... unported, daily-driveable, and with the stock EFI setup... will have to e-mail them and ask specifics.

My curiosity lies in the runner lengths of the stock manifold... they're pretty long, and obviously tuned for low-RPM torque (with exception of the variable-runner setup for Series V's). Mazdatrix's 6-port has a power peak of "above 10,000rpm" with a street port and a 51IDA carb... now the porting on a 6-port, even stock, is pretty extreme, so the HP limiting factor would have to be the intake manifold, after you get rid of exhaust restriction. But then we're getting further to the hairier edge of "daily driveable"......

 

So, are you guys just going to bitch? Or are you going to actually give us some info on WHAT IS REQUIRED. Not to sound harsh, but I didn't ask "What's better EFI, or Carb" I asked how would you go about carb'ing a 13B. The application is haul-***** street/track racer, and sill be bearable, and not TOO unplesant as a daily driver.

 

Yeah, right. The FI system on my 2nd gen has been flawless. The carb on my 1st gen has been nothing but problems.

 

Required for carb operation
-custom intake, and of course the carb
-different fuel pump, filter, etc.
-aftermarket air filter
-some hose work to reroute a few things
-remove all emissions equipment
-loose the AFM
-keep stock ECU to run the ignition
-some rewiring
-lots of time and money for no benefit

 

will the stock ecu run the ign. with everything else unpluged?? it will probably go into fail safe. probably need a distributor.

 

I believe it will still run the ignition...Wait, it's an 89+. OK, the 86-88 ECU will run the ignition, the 89+ ECU will go into limp mode because of the lack of metering oil pump. Not sure how this effects ignition, but it sounds like you will need to go with a distributer.

 

Demon carb...youre kidding, right? Any carb has to be specially modified to work right on a rotary. And as far as I know, RB doesnt modify Demon carbs. They deal mainly with Holley now. They might still be able to modify a weber/dellorto, but I dont know.

Theres a Dellorto carb on Ebay for RX7's, and even comes with a 6 port manifold. It was ~$230 a few hours ago. Do a search for RX7 and youll find it.

 

That's why they make Weber style twin throttle bodies (with 4 injector bosses) that bolt onto Weber manifolds. You can run a TB the same size as a carb but without the restriction of chokes, or you can go for a bigger TB without any of the problems of a too-big carb. Plus you'll have all the other benifits of EFI. I wish people would stop regarding the stock manifold as a reason to go to a carb. It's just wrong!

 

I'd like to see this for myself!


-Ted

 

You know how expensive those throttle bodies and manifolds cost?!?!?!&nbsp In the states, we have a company called TWM - their **** is mucho bucks!



-Ted

 

Yeah, I've seen their site. This stuff is probably much cheaper from Australian companies, even with freight. These set-ups are common as muck over there.

 

*UPDATE*

Ok, friend is STILL going carb'ed. However, new question.

Holley or Dell'orto?

1st, and foremost, which has the greatest HP possibility?

They Holley system is pretty complete @ $620. However, I have no clue of the cost of the Dell'orto Carb, or which carb is suited for the application.

The last point, is down the road, he wants to add N20 ( NOS for you ricers out there ) Do any N20 companys MAKE a Dell'orto application?

 

Wouldn't a carb set-up actually loose HP over a stock or ported intake since you would loose the Dynamic surge?

 

All depends... you can still tune intake runner length with a Weber-style carb, what with different length velocity stacks and the like. Of course, you'll have only one length to choose from, unless you feel like engineering a variable-length trumpet setup like the R26B engine had.

You'd probably end up "losing" as much as much power as the people who wire their 6-port actuators open and wire the VDI actuators open on '89-up models. Assuming you spend the time and the $$$ to tune the carb. Looking at how much Weber jets and venturis and the like cost, it would probably end up cheaper in the long run to just get a Haltech as far as tuning costs go. (Then again, some people think their N/As make more power after putting T2 injectors in even though it was probably running too rich to begin with... "The butt dyno is often inaccurate due to the New Mods effect")

I'm still very curious about intake losses with the stock manifold, especially the common-as-dirt '86-88 N/A setup.

 

If someone could just figure out how to rid us of that stupid AFM, and keep the FI, we could drop this debate. Why can no one do it?

 

It's called Haltech.

 

lets not forget pulsation dampners go bad on all Fi Rx-7's once in a lifetime... and with carburated u wont lose horsepower at all instead it will gain... carburator is way simpler .. less vacuum lines.. easier to work on and it does loose weight around the engine... when my neighboor did carburator on his 88 vert... the front of the car lifted a slighty... because of the lost of engine weight... to do the carburator set up on an 89.. you'd need a jay-tech intake manifold if u can find one or a racing beat intake manifold but then u will need turbo II side housings or 13b 4 port side housings out of an 8485 rx7.. because the racing beat intake manifold right now is only for 4 ports.. 6 ports coming soon.. you need block off plates for the egr and acv i believe.. wire the 5 n 6 ports open.. also if u go with 12a side housings u will need to change the motor mounts positions..and lets not forget a good holley 600 or 650... i know theres a lot of people arguing that fi is better than carb or carb is better than fi.. but let me just say something ive never seen the amount of gain of power using carb compared to the stock fuel injection... and another point the carb is way more simpler compared to the fuel injection system on these cars....also the engine bay looks cleaner with carb setup