blackvette

Hi there. I'm posting this question for a friend who has an '89 GTU. He has a few mods to the car, the biggest being a new ported polished motor. We are planning on bolting on a new manifold and Holley carb. He is waiting for the new Racing Beat 6-port manifold to come out which should be soon. So the question is, anyone do a carb conversion and have any advice? Thanks in advance.

BTW-- Any idea what 1/4 mile times this set up will run? We are hoping for low 14's at least.

amemiya

advise don't do it. carbs are old tech........ all the fast cars us fuel injection why because you can tune every last bit of power out of the engine VS a carb spitting fuel every time it sees air go by

Poindexter10thae

iTrader: (2)

I used a Weber 48mm sidedraft carb kit from mazdaracing. only thing to remember is not to gut the computer or the CAS(unless you are going to a distributor, which is not wise), simply tie back all the EFI leads, the ECU still will control timing and does an excellent and efficient job with the carb.

Poindexter10thae

iTrader: (2)

Please learn and study how a carbureator operates.

breesej

Amen to that....
Amemiya has no clue what he's talking about, Carbs can offer similar power but substancially less initial cost. I can build a carbed car for almost half of a FI car and be racing in almost weeks instead of year(s)

Dyre

Carbs are fine for weekend warrior drag cars that don't ever go partial throttle.

The only people that switch EFI cars to carb are either making full drag cars... or are scared of new tech... or just cheap.

Carbs are evil.
<----From the 'new school'

FPrep2ndGenRX7

Why is it that many race cars make all that HP with a carb setup? Because the rules dictate that they must use a carb or there is a weight penalty. Why do most people think that carbs are the way to go when looking for more HP? Its because all the real race cars are making good HP from their carb setups. Lots of dyno time and properly tuned intake and exhaust configurations. If you don't have the time and money to fully develope the Holley carb on you your engine you would probably be better off to maximize the exsisting intake setup. But then again its your friends car and if he has his mind made up then there is nothing we can do. Personally, after a year of asking questions and researching carbs and EFI systems I'm going to go the EFI route. Why? If you put the same amount of air/fuel mixture into an engine whether its carbed or injected you make the same amount of HP. The EFI system will simply let you control the delivery better, atleast thats what I've come up with I do have a weight penalty to deal with but my racecar is not borderline at the class minimum so it doesn't matter.

blackvette

I think you pick up a bunch of hp with a carb at the expense of low end torque because of the length of the runners. Supposedly around 40 rwhp gain according to RacingBeat. This ported polished motor doesn't have any low end torque anyway, so he will just have to launch at a higher rpm. We are really hoping for 13s at least!

I know with my Corvette if I loose the long runners of the TPI setup and get a carb I will gain around 75 hp but loose around 40 ft/lbs of torque down low.

Also, my buddy says that his stock computer system does not take well to upgrades. Basically he said it works well within the parameters of its design, but once the engine starts flowing more air the computer can't keep up. He already has a major idle fluctuation during warm up possibly from a confused computer. The car has a new TPS and has been checked over. He thinks it is because of the new port/polished motor. Basically, a carb should simplify things and allow for better tuning.

The new 6 port manifold was released for sale today, and he is going to order tomorrow. I told him about the used Jay-Tech manifold (thanks HAILERS), but the advantage of this new manifold is that the extra 2 ports actually function whereas on the older ones they didn't. Does the Jay-Tech manifold mantain the use of the 6 port function? I could call him in the morning if it does b/c he was very interested in saving the $.

amemiya

I never said it wasn't cheeper, why don't you port your efi intake and shorten the runners or go with a turbo intake and housings, the problem is $$$ right well if you can't fork out the $$$ then go carb put don't let it sit long if the carb dries out you have to rebiuld it. And good luck tunning it. I have had my share of carbs mostly holly they where good back in the 70's this is the new age profect the new tech and it will dominate all. The time of the carb IS OVER.

Josepi

EFI is easier to make cleaner.

Rotortuner

My friend runs two 4 barell 12 a carbs on a hommade intake on his 6 port fc. Ya you read right dual 4 barells. We did a little porting on the primarys and big on the secondarys. Any ways the intake is like a tunell ram so all together.

CJG

Mazdatrix

iTrader: (1)

Btw - the new Racing Beat 6-port Holley manifold does NOT have anything for the 6-port actuators.
We have one here for testing purposes, and it is essentially just the 4-port one with the casting re-done -- but it IS a nice piece, and should fit the 86-91's WITH an air filter and automatic choke (which the JayTech's would not).

JOE@FC3S.ORG

I assume you would just remove the sleeves on install. If I am not mistaken, there is just another set of holes for the 6 port holes, but it shares the same "space" as the lower intake holes enter the engine. In other words, there are not 6 paths, just 4 paths and 6 holes.

Any idea of the estimated HP range on a stock-port 86-88 engine? Also, where can I get some info on the "Jay-Tech" manifold?

Joe Romeo
www.fc3s.org

Angel Guard Racing Team

I am sorry guys but the first rotary to hit 7 seconds (7:62) uses webber carbs and turbo. Carb might be old tech but it is the best way to make an RX-7 N/A a mean beast. No N/A factory cpu with upgraded injectors can outrun a Ported engine with 650 cfm holley with Jay-Tec intake manifold, racing beat header, 2 1/2" or 3" straight exhaust (curve under the rear end not over). With this combo and two msd blaster 2 coils you will be running very fast no 5.0 Mustang should be a problem... Do the math and after you install the carb. conversion you will still have money left to hang out. By the way... you will still pass emissions test without a cat. Rotaries have a high curve when it comes to emissions test (Not in California).

NZConvertible

So what?! This forum is mainly for road cars that have to have good part throttle response, a smooth low idle, decent fuel economy, pass emissions tests AND have good top end. Drags cars are irrelevant in carb vs EFI discussions due to their narrow tuning focus. Also, the car you refer to was a fibreglass-bodied tube frame car. Full steel-bodied Aussie rotaries weighing a helluva lot more are now as fast. No carbs in sight.

Um, you've just compared a basically stock car to a heavily modded one. What's the point in that? People who make more power changing to carbs do so because they put on a huge carb that can flow more air. Why not install a bigger manifold with EFI? Provided the intake manifold can flow the same amount of air the carb, EFI will provide slightly more top end, a solid mid-range improvement and superior drivability and economy.

Poindexter10thae

iTrader: (2)

I specifically built my carb'd FC to be the meanest 2nd gen N/A in my area, and it was. It was fully streetable, got ok gas mileage(not one of my main concerns), and was fast as hell WITHOUT the nitrous. If you want the best bang for your buck, and you dont want to go the forced induction route, carb is the way to do it. EFI components MIGHT be able to produce the same effect on a N/A, but it would be about three times the cost, ten times the hassle, and take an additional 2 months for fine tuning. I have been down both roads, for NA vehicles I will stick with the carb.

kabooski

you talk alot of **** NZ

It's your f'ing choice if you want to run full body or Tube
There is a 85 Red 300ZX in P.R that is full bodied full interior
that will kick any thing you excuse making aussies have.

KNONFS

iTrader: (14)

AS fast, don't thinks so.....NOT YET!! There are(\used to) plenty of FULL BODY Puerto Rican cars in the low 8's. Same as Aussies, in fact they just broke the 7'sec barrier (not even 6 months ago)!!

NZConvertible

That's not exactly an intelligent argument.

I didn't say it wasn't. But that doesn't change the fact that much heavier rotary-powered cars are running 7's. That was my point.

Again, not much of an argument. You must have forgotten to mention it's time. And as I have pointed out in the past, I am not an Aussie. That's why my user name has NZ in it.

RETed

Carb is old technology.
EFI is the current standard.

Sure, EFI components cost more - it's the newest tech; you pay for all the "new" stuff.

If you call EFI a "hassle", you're a neanderthal, PERIOD.&nbsp The ROTW is looking to the future, and you're hanging onto what you know cause you don't want to learn something new.

Can carbs make the same power as EFI?&nbsp Sure.
Can carbs make MORE power than EFI?&nbsp I highly doubt it, considering everything else is kept the same; in fact, EFI should be superior due to better atomization, in general.
Is EFI more efficient (for daily driving)?&nbsp **** YEAH - anyone who claims their carb system can beat a properly tuned EFI system on the street in gas mileage is smoking good stuff.
Can carbs produce a fast car?&nbsp Of course, I never said it can't be done.&nbsp But remember, whatever a carb can do, an EFI set-up can do also...

This debate should be moot.&nbsp If contingents can read what modern engine control and motorsports is doing, you'd KNOW EFI is superior.&nbsp As someone else mentioned, carbs in racing is usually due to rules restrictions or advantages for using a carb.

If you're scraping the stock EFI system on your FC, it better be some extreme reason for doing so...




-Ted

NZConvertible

Thank you Ted! Carb fans should do a little research before they try to covince everyone of a carbs supposed superiority.

Icemark

Ted hit the nail right on the head

kabooski

how many of you N/A
are running a aftermarket ECU ??????????

HA!

Let's see a ported 6 port with STOCK ECU and upgraded Fuel system
i.e upgraded injectors,fuel pump etc
Take on a Ported 6 port 650 Double Pumper
85 dist

There's one here running 13.0!!! with secondary bridge
beat that!

If you want a nice driveable low noise rx7
Then leave it stock!

He is clearly wanting more power!

you turbo guys
dont know squat

RETed

Don't know squat?&nbsp Why the hell I wanna mess with carbs when I can...

NOS THE BITCH!
I'm sure I can beat a 13.0 with a 200shot that might cost me $600 total!

Us turbo folks don't know squat?&nbsp HA!


-Ted

kabooski

what car you drive Ted?

thank you

TII's is one thing
Fuel Injection works the best

But for a N/A CARB makes the Best/$- Power

spending 1.3k on a ECU for a N/A? like to see that



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88 GXL
87 SE
87 TII
...etc