i recently purchased an 85 se after a buddy destroyed my 84 gsl with alot done to it. i am having some minor tuning problems that i can fix but am not fond of all the extras that can go wrong with fuel injected i looked around for pros and cons and couldnt find feedback that was justifyable enough. So my question is who has gone carburated after having driven fuel injected for a while and wouldnt have it any other way.

 

If you like tuning and adjusting more often than not then go for carbs. I hear they'll get you an easy 40-60hp (with open exhaust of course) with proper tuning. I'm going to run dual carbs on my '81 with a 6 port 13B. However carbs are a headache to tune and keep running right.

 

not really, i think carbs are more better because of the tuning that you CAN do, with EFI you can only change the injectors and get a better ecu, with the carb u can change the jets, for whatever setting you want, drag racing, drawthrough turbo, blowthrough, auto x, all kinds. and tuning is easy, and you only have one vac line, if it was a toss up, id go carb all the way, i hated the freakin fuel injeciton

 

Carb. The enjoyability of working with a carb is awesome.

 

The problem with getting a true picture of the carb/efi differences is the ignorant comment by people without knowledge.
flamin-roids--- 40-60 hp better with carb---- absolute nonsense!
RVseven--- does not seem to know you tune the efi ecu not buy a new one! You can store different settings and quickly change the ecu map for different conditions.

An efi will be some 10% more powerful than a carb over the rev range. However the difference is not so great at peak power, only about 5%. If you are only interested in peak dyno results the difference is small, but for the 1/4 mile the efi will be far quicker. In addition fuel consumption with efi is lower.

For a typical independent view read John Angas in Mazda RX-7 Performance Manual

"Watching both systems at work on the same car, the results were not surprising. With the Holley 0-60 times were around 7 seconds, but after the Efi system was properly tuned it shaved a full second from this time, plus there was a slight improved gas mileage"

At one time few people knew how to set up efi system because factory settings were very conservative. Today , excellent maps are available to set up performance efi very quickly. Often these can be downloaded from the internet saving money from going to a tuner.

Working directly on a carb has some personal satisfaction going partway to offset the knowledge it is less efficient than efi.

 

paul doesnt seem to realise you cant tune the gsl-se ecu

 

BigJim- My response was to a general comment on efi. I agree you can not tune the se ecu, its the same problem with the 12A T. This is why if you want better performance you upgrade to a modern ecu which gives you tuning options. Currently I am using a fuel only computer with the stock distributer, for a Haltech you can download the appropriate map from Hitman. The cost of upgrading from an early model ecu is usually cheaper than going carby and gives better performance.

I have heard of a few people going carby on late model13B engines. But this is due to cost considerations using imported low mileage engines as against rebuilding a worn out 12A when there is a good chance the housings have had it, while the imported engine comes without an ecu or harness.

 

The best thing to do with a carb is to see how far you can throw it. I only use a carb if rules say I have to and I gripe about it the whole time. EFI is the way to go for any engine, you can change anything with the fuel anywhere without having a box of jets to keep track of. If you're cheap like me go Megasquirt, if your car is injected already for a few hundred bucks you can have full programability.

 

from the limited info i know of the GSL-SE FI setup, i'd opt for carb(which i did lol), because the stock FI is pretty limited, and not very well designed compared to say S4 or S5 NA setups... but i'm going to be going FI on my holley based setup later on, when i can afford the megasquirt, injectors, and throttlebody... my cheapo FI setup... i figure my racing beat holley manifold is designed better than stock GSL-SE FI, especially with how large a diameter its runners are...

 

thanks for the inputs. i dont have the access to tuners or the money to spend on ecu s and all that good stuff eventually i will be rebuilding my 6port with s5 rotors and whichever housings are in the best shape be that s3 or s5 from 4 port to 6 port and i am not looking for 12 second 1/4 times or 0-60 in 5 seconds i want a fun hassle free gsl-se. the gas milage is worse with my se due elctronics B.S. that i havent got around to doing than compared to my gsl so with that in mind what reccomendations would someone suggest for a daily driven carbd se with a moderate to small port job and light weight rotors? 4 port or 6 port for a carb? thanks guys

 

best carb choice would be a 48 weber....

 

If you decide to go back down the carby route with porting the engine, then 4 port is the best option. The 6 port was designed for fuel economy not increaserd performance and is more difficult to port.

After looking at all options in great detail earlier this year, I would recommend 4 port, rebuild and streetport, with a Webber IDA 48 carb and a 2 1/2" exhaust. Top end power will be good, lower range moderate to poor, noticeable increase in noise and gas consumption. Predicted power would be in the order of 180-190hp after comprensive tuning, say around 150hp realistically at the wheels if you test on a dyno.

 

If you decide to go back down the carby route with porting the engine, then 4 port is the best option. The 6 port was designed for fuel economy not increaserd performance and is more difficult to port.

After looking at all options in great detail earlier this year, I would recommend 4 port, rebuild and streetport, with a Webber IDA 48 carb and a 2 1/2" exhaust. Top end power will be good, lower range moderate to poor, noticeable increase in noise and gas consumption. Predicted power would be in the order of 180-190hp after comprensive tuning, say around 160hp realistically at the wheels if you test on a dyno.

 

whats more difficult about porting a 6 port? i've only had experience porting my 6 port, and touching up ports on a 4 port 13B... but i didn't find either one more difficult than the other... and yes, my avatar is my port

and i thought the purpose of a 6 port was more top end power without sacrificing the low end, hence the actuators

 

I love my carbed SE. It yeilds more power than the factory FI and is cheaper and easyer to deal with than a standalone. those are the biggest benifits. A properly tuned standalone will always slightly have the edge on a properly tuned carb, but 10% across the rpm range is an exageration.

If you have the money and capability to tune an aftermarket FI setup get one. If not, go with a carby.


--Alex

 

The problem is to get the optimal port shape when Mazda has compromised the options by the existing design of the 6port.

The figure 10% is the aggregate power over the range,ie the area under the total power curve. Most of the difference comes from the lower rpm range. The specific difference obviously varies by rpm and with a well set up carb aimed at the top end, peak power difference is lower.

 

thats what i am leaning towards. ive been doing some research in the FC generation threads and a guy dynoed his s4 with an s5 intake setup complete lim, uim TB and some port matching to gaskets and the dyno found to be 13 horse without tuning and with tuning who know maybe 10 more in there. a little change in topic is i can use 12a side plates and intermediate and 13b housings with s5 rotors cant i if i am going carbd and ported id use 12 plates for the 4 port design. all the input is great

 

bumpity

 

Depending on how much driving you do, Megasquirt when properly tuned will pay for itself within a year in fuel savings. Mazda made the cars run very rich stock (especially 2nd gen), too rich even for best power. They did this to keep the cats happy, if you've got no emssions testing or components then you can lean the map out, make more power and get significantly better fuel milage. This is based upon two people who have megasquirted two very different rotary set-ups and gotten the same results
Grant

 

Well of course an EFI setup will get better results but the cost is much greater. The standalone itself can run up to $1k and then you've got to upgrade injectors etc. Meanwhile you can get a carb setup for roughly $500 and not have to worry about wiring and what not. And I said I've heard of 40-60hp increase over the stock EFI setup (Probably the S3 and S4 EFI setup). I'm building a 6 port 13B to run a carb setup for my '81. Reason I'm going carb is to eliminate the harness and any ECU of any sort. Not to mention the cost of new injectors and a standalone not to mention installing a harness and all the other bullcrap. EFI is definitly superior in every aspect other than cost.

 

megasquirt costs like 200 bux, u assemble it urself... i'm not sure if its even 200 bux... might be less... its a deal and a half

 

fuel injected versions of the famous downdraft IDA carburators.
that way, you can still keep your FI setup if you want

 

this is going into my FB one day lol

 

How does dumping more **** into the cats make them happier?

 

They need to burn a specific fuel mixture, too lean and they will melt; especially behind a rotary. A rich motor will run much lower exhaust gas temps. As for the cost of Megasquirt, I just ordered a kit from www.diyautotune.com and it was $140 with shipping. You have no need to upgrade your injectors as they already run the car rich as hell. After this mod the only restriction in your intake is the lower intake manifold. It also offers complete 3D mapping of fuel and ignition (trailing still isn't finished with a split but it's close), a 12X12 map (with newer FREE firmware), 3 rev-limiters and a bunch of other cool stuff.
Grant

www.msefi.com