1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

How to mod a 13b

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Old Nov 5, 2005 | 05:00 PM
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From: ennis
How to mod a 13b

Okay, I have a fuel injected 13b. This is in a 1984 RX-7 GSL-SE. What can I do to mod this rotary up to where I'm getting about 400 rwhp. Try to keep it cheap bc I don't have a large amount of funds.
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Old Nov 5, 2005 | 05:08 PM
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Turbo, SAFC, FMIC...custom 3" exhuast, Street port, and 14-16 psi Boost

Oh yea, and you're gonna need a turbo motor.

It's not gonna be cheap, so unless you have $4k lying around, I wouldn't consider it. 6 port motors are tough to turbo because of the high compression. You can only give them but so much boost.

The cheapest way I see it is Nitrous, but you're gonna need a SHITLOAD of it. Maybe a 250 hp shot. Plus you'll need exhaust and fuel to support it, along with a more efficient intake system. I'd say $2k for the N20. Plus I doubt the motor is gonna take a 250 shot well. Can you say rebuild often?

Last edited by lovintha7; Nov 5, 2005 at 05:11 PM.
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Old Nov 5, 2005 | 05:16 PM
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400rwhp doode i dont think u would want to do that , specially rotaries are not that good with gas mileage and gas prices kinda pricey now . i think 250 is a good amount of power for an n/a 13b engine . aim for the cornering not for the 1/4 mile ,to me the 1/4 is kinda played out its all about drifting and suspension now .
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Old Nov 5, 2005 | 06:14 PM
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400 RWHP is nearly 500 crank HP.......good luck.
I dont think you realize how much power that truely is....especially in a 2500lb car designed for less than 150HP.
A 250 crank HP 13B is not very hard to build and might cost 1800-2000 bucks depending on how you shop.Itll make an otherwise stock FB into a formidable street machine and wont require a big rearend,brakes,suspension,chassis mods,ect.
400RWHP is a wicked powerful setup many FC and FD guys strive for, and when they do,they are usually breaking drivetrain parts and their banks.Youll probably spend more money keeping the drivetrain together and the FB chassis stable with 400RWHP,than you spent on the actual engine.
I dont know how much experience you have or what if any mods youve already made to your SE,but youll need to do a lot of reaserch first and then set realistic goals.
Honestly,if you have to use the phrase,"I dont have much funds"....then 400RWHP is completely out of the question.
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Old Nov 5, 2005 | 06:37 PM
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If your broke and want to go fast, go ride in a friends car thats fast.............
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Old Nov 5, 2005 | 06:45 PM
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Originally Posted by BootlegRX7
Okay, I have a fuel injected 13b. This is in a 1984 RX-7 GSL-SE. What can I do to mod this rotary up to where I'm getting about 400 rwhp. Try to keep it cheap bc I don't have a large amount of funds.
you might as well give up now
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Old Nov 5, 2005 | 07:07 PM
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I'm shooting for 300 whp, and I don't even think my $3500 budget is gonna do it. Just put that in perspective for you.
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Old Nov 5, 2005 | 07:12 PM
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drop in a 13b turbo.... ?? how u gonna get that amount lol on a small budget.
200-250 maybe.. but not 400
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Old Nov 5, 2005 | 07:14 PM
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400 would just be SCARY!
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Old Nov 5, 2005 | 07:27 PM
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Is it bad to turbo the 86-92 NA 13b engines? My buddy got one that he can sell me for cheap, but it's not the turbo engines. He said it has 100+ compression on both rotors with a recent rebuild, but i heard you dont wanna turbo high compression ones.
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Old Nov 5, 2005 | 07:49 PM
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Easiest way to get 400rwhp in a first gem is a V8 conversion. But even that wont be cheap. And as everyone said you'll then have driveline concerns and chassis flex. A stock LS1 corvette engine alone is worth 2,500 to 4k with harness and ecu. Some things you cant get cheap. Read the forums and you'll see there are things you can do but theres no miracles. Check mazspeed.com facts section nice how to's there. Good luck.
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Old Nov 5, 2005 | 08:14 PM
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Originally Posted by DwArF
Is it bad to turbo the 86-92 NA 13b engines? My buddy got one that he can sell me for cheap, but it's not the turbo engines. He said it has 100+ compression on both rotors with a recent rebuild, but i heard you dont wanna turbo high compression ones.
You can turbo them,infact,you can make good power on low boost since the static compression is already high.The disadvanage is that detonation will set in sooner so you have to go easy on the boost.And the N/A engines intakes and porting are designed for naturally aspirated airflow,with all their dynamic tuning and such.
A factory turbo engine(TII) is a better starting platform that will require less re-engineering and guesswork,but plenty of guys have turbocharged the N/A engines with varying sucess.The biggest and baddest turbo rotaries are almost always TII or FD based.
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Old Nov 5, 2005 | 09:01 PM
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Originally Posted by steve84GS TII
You can turbo them,infact,you can make good power on low boost since the static compression is already high.The disadvanage is that detonation will set in sooner so you have to go easy on the boost.And the N/A engines intakes and porting are designed for naturally aspirated airflow,with all their dynamic tuning and such.
A factory turbo engine(TII) is a better starting platform that will require less re-engineering and guesswork,but plenty of guys have turbocharged the N/A engines with varying sucess.The biggest and baddest turbo rotaries are almost always TII or FD based.
So I would be better off buying a TII engine then buying a Stockport NA 13b or a SP NA 13b
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Old Nov 5, 2005 | 09:36 PM
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It depends.
If you want hassle free, and a better platform,yes Id go TII engine.
If you wanna be different and get it cheaper(initially), then the N/A 13B can be turboed.

Personally,I like to do things right the first time. Letting Mazda do all the R&D for a reliable turbo rotary makes the most sense.Thats why the TII engine is better,its MADE to be turbocharged....lower compression,filtered turbo oil feed,smoother exhaust ports,intake ports/manifolds tuned for forced induction,knock sensor,bigger injectors/AFM,ECU designed for boost,ect.

Last edited by steve84GS TII; Nov 5, 2005 at 09:40 PM.
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Old Nov 5, 2005 | 10:01 PM
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Originally Posted by steve84GS TII
It depends.
If you want hassle free, and a better platform,yes Id go TII engine.
If you wanna be different and get it cheaper(initially), then the N/A 13B can be turboed.

Personally,I like to do things right the first time. Letting Mazda do all the R&D for a reliable turbo rotary makes the most sense.Thats why the TII engine is better,its MADE to be turbocharged....lower compression,filtered turbo oil feed,smoother exhaust ports,intake ports/manifolds tuned for forced induction,knock sensor,bigger injectors/AFM,ECU designed for boost,ect.
Oh word, I was fenna run a Megasquirt with it.

I could have gotten a 13b for 500 and the same engine rebuilt and SP for 1600.
Would it be mroe worth it to buy a TII off ebay for 1300 with like ~50k miles from japan
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Old Nov 5, 2005 | 10:32 PM
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Ehh,
If your gonna run a standalone ECU,then all you really need is a block and manifolds.You could probably find something private party.
The Jspecs come with all the other stuff usually,which youll pay for,then promptly discard.If you get a deal on one,then yea its worth it.You can also sell the ancillary stuff off....
Sometimes Jspecs are good and sometimes not....Seriously,if you knew you had to change your engine out every 30K miles,would you treat it right?!Many have a warantee,but its still a pain to pull the bad engine out,ship it,then install another questionable engine......
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Old Nov 5, 2005 | 10:41 PM
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How would you go about building a 200-250 rwhp N/A GSL-SE?
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Old Nov 6, 2005 | 12:43 AM
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Originally Posted by kgray
400 would just be SCARY!
NAW.... It's fun!!
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Old Nov 6, 2005 | 12:50 AM
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Again,thats a tall order.
Everyone seems too hung up on rear wheel horsepower.Whats the point?
Factories rate their engines in flywheel horsepower,after all,thats how much horsepower the engine is ACTUALLY making!!So why not take that into perspective when you plan on an engine buildup?
Wanting a 250RWHP means your going to be making about 300 crank hp,assuming 20% drivetrain losses.An FD 13B only makes 255,a 20B barely makes 300HP.
To get 300HP from a non turbo,6 port 13B means youll need some serious porting,likely bridgeporting which the 6 port isnt ideal for and will also limit engine life due to the high RPMs that are needed to make those ports breathe well.Again,the SE engine is not idealy suited to this having the heaviest rotors,3MM steel seals and non-hardened gears.And what kind of lowend power or idle would it have?What good is 300HP at redline if your flat on your face below 5000RPMs?Its not that you couldnt do it,its just would you WANT to drive something like that?
Remember,the SE 13B was designed to make 135HP, and 133lbs of torque at an amazing 2700RPMS!!Thats incredible for a non turbo rotary,its called tractability and it makes the SE engine the most broadly powerful non turbo rotary around.To rebuild it to make 300 peak HP is to ask it to do something that it was never intended to do.If you want super high peak power with no regard for lowend torque or tractability,bridgeport the **** out of a 4 port 13B with S5 N/A rotors.But dont expect it to be very smooth or civil.
A turbo engine would have a broader powerband,last a lot longer and be more driveable.An N/A engine with streetporting might not make 300 crank/peak HP,but it would be much easier to drive and have more USABLE power than a N/A drawn out to its limits with wild porting and a short lifespan....just to get 300RWHP.
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Old Nov 6, 2005 | 01:26 AM
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Ok, well, I just want to suck more power out of it, nothing crazy, just wanted to know how hard it would be?

How hard would it be for just 200 crank or wheels?
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Old Nov 6, 2005 | 02:02 AM
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heres a start. Headers/exuast/intake/efan/street port/. that should put u around 175 (Pure guess can anyone verify horsepower for these modes?)
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Old Nov 6, 2005 | 02:32 AM
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Originally Posted by Max7
If your broke and want to go fast, go ride in a friends car thats fast.............

fuggin classic i always ride in my friends pt72 supra when mine is down WOOT!
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Old Nov 6, 2005 | 03:17 PM
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From: ennis
The reason I'm broke now is bc I just got through restoring my 1979 Z28 Camaro that has 500rwhp. Took me 15K to get it to showroom quality and get the power I wanted out of it. I'm new at the whole fuel injection and turbo bit. I intend to use my RX-7 as a daily driver and have my camaro as a daily driver but I want enough power in my rx-7 to have some fun in so what do ya'll suggest. May I also mention that I'm 16.
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Old Nov 6, 2005 | 03:24 PM
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Well, 200-250 HP would be fun. Not crazy *** blistering fast, but definatly fun. A TII swap would get you that easy.
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Old Nov 6, 2005 | 04:47 PM
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If you're 16, and need to have a little more pep, do what 3times said.

How does a 16 year old afford to pump $15k into a car?
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