GSL-SE 13B Fuel Injection questions
02-28-16, 12:35 AM
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GSL-SE 13B Fuel Injection questions
I want to buy a 1984-85 RX-7 and I want either the GSL or the GSL-SE. I'm kinda leaning toward the SE because of the more powerful SE, but I think it only comes with fuel injection as opposed to the 12A's carburetor. I want the extra power the 13B has, but I'm a little wary when it comes to 80's fuel injection... Is it manageable? I've always been told to steer clear of early fuel injection. You can make a carburetor work, but fuel injection can be very fickle...
Any advice would be much appreciated...
Any advice would be much appreciated...
02-28-16, 01:08 AM
#2
I have a GSL-SE that no longer has EFI. Instead it has a 12A Nikki carb that's been hogged out and boost prepped. Even without boost, it is SOOO much better than ancient limited (and limiting) EFI. With boost, it's so much better than the original setup it's hard to compare. Like apples to oranges almost.
It's kind of a joke, really; the original EFI. I Agree. Stay away. Also avoid the 86+ EFI. I tried it once (in the red car). Will never try it again. Garbage.
There are some purists on this forum like LongDuck that will answer all your GSL-SE EFI related questions, but I think it's a sinking ship personally.
It's kind of a joke, really; the original EFI. I Agree. Stay away. Also avoid the 86+ EFI. I tried it once (in the red car). Will never try it again. Garbage.
There are some purists on this forum like LongDuck that will answer all your GSL-SE EFI related questions, but I think it's a sinking ship personally.
02-28-16, 09:21 AM
#3
Old [Sch|F]ool
The GSL-SE fuel injection is extremely simple. It is basically a license of first generation Bosch L-Jetronic. Air goes through the flapper, fuel comes out the injectors, and it's good.
Most of the problems I see with it is people screwing around with it because they're afraid of wires and vacuum hoses so they want to get rid of it all. Problem is, the system is designed to work with the extra air going into the exhaust from the air pump, take that away and it won't run well anymore. But at least you got rid of all of those evil hoses and solenoids hidden under the intake manifold.
The same thing happens with Nikki carbs. They work great until you screw with them, then five "OMG HELP" threads later the car is for sale or gets a V8 swap that gets halfway completed before the car is scrapped due to lack of ability.
Most of the problems I see with it is people screwing around with it because they're afraid of wires and vacuum hoses so they want to get rid of it all. Problem is, the system is designed to work with the extra air going into the exhaust from the air pump, take that away and it won't run well anymore. But at least you got rid of all of those evil hoses and solenoids hidden under the intake manifold.
The same thing happens with Nikki carbs. They work great until you screw with them, then five "OMG HELP" threads later the car is for sale or gets a V8 swap that gets halfway completed before the car is scrapped due to lack of ability.
02-28-16, 09:31 AM
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the GSL-SE EFI is pretty basic, and its early Japanese efi. the Japanese went to great lengths to make sure it worked, and except for setting the idle it does. the idle takes a few steps to setup, you need to set the TPS, and then the idle speed, mixture and then there are two valves you need to clean, and one is adjustable. so there is enough to make it a two pass deal, where you set everything, and then go back and set everything.
by contrast my brother has a VW that is actually a bit newer, and he's had to replace every sensor on the engine twice now, and god help you if there is more wrong than that, because the Germans don't understand electricity so its wired like an aftermarket stereo from the 80's at best. i'm sure if we could find a VW guy who was willing to work on it, even for money it could be better, but basically my P port runs better than this car.
so keep in mind that "early efi" advice applies to german cars, because on a german car, if its not something simple, its a total nightmare and you're almost better off with a ground up restoration.
by contrast my brother has a VW that is actually a bit newer, and he's had to replace every sensor on the engine twice now, and god help you if there is more wrong than that, because the Germans don't understand electricity so its wired like an aftermarket stereo from the 80's at best. i'm sure if we could find a VW guy who was willing to work on it, even for money it could be better, but basically my P port runs better than this car.
so keep in mind that "early efi" advice applies to german cars, because on a german car, if its not something simple, its a total nightmare and you're almost better off with a ground up restoration.
02-28-16, 09:51 AM
#5
Old [Sch|F]ool
German engineers understand electricity just fine. They just don't LIKE it and seem to do everything they can to impede its travel. So you get things like unsealed, open-backed wiring connectors (during the time GM had been using Weatherpak for years) and wire insulation that works just fine as long as you don't get the wires over room temperature, or move them.
(note: I own an '83 GTI and an '86 Quantum that are immobile due to mass wiring problems. One has water damage and PO "Throw parts at the problem" issues, and the other has wiring like uncooked spaghetti. I used to own an '89 Golf with Digifant and I am probably the only person ever who liked Digifant. It was L-Jet with idle and ignition control. Getting it to idle correctly was an exercise in counterintuitive thinking, like increasing the amount of idle air in order to get the idle speed *down*)
(note: I own an '83 GTI and an '86 Quantum that are immobile due to mass wiring problems. One has water damage and PO "Throw parts at the problem" issues, and the other has wiring like uncooked spaghetti. I used to own an '89 Golf with Digifant and I am probably the only person ever who liked Digifant. It was L-Jet with idle and ignition control. Getting it to idle correctly was an exercise in counterintuitive thinking, like increasing the amount of idle air in order to get the idle speed *down*)
Last edited by peejay; 02-28-16 at 09:55 AM.
02-28-16, 10:04 AM
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German engineers understand electricity just fine. They just don't LIKE it and seem to do everything they can to impede its travel. So you get things like unsealed, open-backed wiring connectors (during the time GM had been using Weatherpak for years) and wire insulation that works just fine as long as you don't get the wires over room temperature, or move them.
(note: I own an '83 GTI and an '86 Quantum that are immobile due to mass wiring problems. One has water damage and PO "Throw parts at the problem" issues, and the other has wiring like uncooked spaghetti. I used to own an '89 Golf with Digifant and I am probably the only person ever who liked Digifant. It was L-Jet with idle and ignition control. Getting it to idle correctly was an exercise in counterintuitive thinking, like increasing the amount of idle air in order to get the idle speed *down*)
(note: I own an '83 GTI and an '86 Quantum that are immobile due to mass wiring problems. One has water damage and PO "Throw parts at the problem" issues, and the other has wiring like uncooked spaghetti. I used to own an '89 Golf with Digifant and I am probably the only person ever who liked Digifant. It was L-Jet with idle and ignition control. Getting it to idle correctly was an exercise in counterintuitive thinking, like increasing the amount of idle air in order to get the idle speed *down*)
scene, interior, factory floor. car is in the center of the floor, semi complete
hans: "hey boss, everything is wired up"
franz: "i just found out we need a coolant temp sensor"
hans: "ok i'll wire it up"
[runs two wires to the new temp sensor]
hans: "ok, now we're done"
franz: "i just found out we need another coolant temp sensor"
hans: "ok i'll wire it up"
[runs two more wires to the new temp sensor]
hans: ok done! now we can go home
franz: oh, now they are telling me we need a thermostat.
hans: !#@!
hans: where the f am i going to put that?
[adds thermostat housing and the other 5 (count em!) radiator hoses and the pipe from the break room sink to make it all fit]
hans; ok NOW we're done.
franz: oh now they want headlights....
hans: [looks at relay box, which is full, adds 2 relays next to box, runs wires]
etc....
02-28-16, 01:56 PM
#7
^LOL
The factory 79-80 Nikki was calibrated rich at idle and in other places in its curve for the thermal reactor and the air pump etc. I really don't like 79-80 carbs. I prefer 81-85 because they take mods better and are just better designed over all. Their idle and AF curve is quite tunable and can be recalibrated easily so they run excellent without an air pump, and they can also handle boost keeping the curve within the safe zone from idle up to 8000 (I don't take mine any higher).
I couldn't test 79-80 in depth because they go scary lean in boost at the top of the primaries so I had to cut the tuning time short and likely won't attempt it again. Too risky.
The factory 79-80 Nikki was calibrated rich at idle and in other places in its curve for the thermal reactor and the air pump etc. I really don't like 79-80 carbs. I prefer 81-85 because they take mods better and are just better designed over all. Their idle and AF curve is quite tunable and can be recalibrated easily so they run excellent without an air pump, and they can also handle boost keeping the curve within the safe zone from idle up to 8000 (I don't take mine any higher).
I couldn't test 79-80 in depth because they go scary lean in boost at the top of the primaries so I had to cut the tuning time short and likely won't attempt it again. Too risky.
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02-28-16, 02:20 PM
#8
Old [Sch|F]ool
The funny thing is, I swapped my '80 carb onto my '85 (and later my '84) because it just plain worked awesome. I think that carb had 240k miles on it when I stopped using it between three cars, 130k of them mine. I never opened it, never needed to, it always just worked.
Of course, I also never mucked around with it aside from removing the secondary spring
I tried mucking with the '85's carb, It was a mess when I got to it so I could only make it better, I thought. Nope. Binned it and put the '80 carb on there
Of course, I also never mucked around with it aside from removing the secondary spring
I tried mucking with the '85's carb, It was a mess when I got to it so I could only make it better, I thought. Nope. Binned it and put the '80 carb on there
Last edited by peejay; 02-28-16 at 02:22 PM.
02-28-16, 03:59 PM
#9
Totally understandable. Factory 81-85 carbs are calibrated so painfully lean that they just don't run right when you start mucking around with them, unless you know what to do to recalibrate them for:
a) running with no factory choke
b) mechanical secondaries (or no spring like you said)
c) any air flow higher than the stock dinky 20mm venturis allow
The 79-80 carbs are jetted richer and have smaller idle air bleeds (short slows) thus leading to a richer idle and fatter transition circuit. Thus it runs better in a not-exactly-factory-anymore scenario like yours. But if you can really get into an 81-85 carb and recalibrate it the way I do for boost, it runs equally well for NA. It really is shocking how much these tiny factory carbs have in them. Wankel-awesome found this out with just 24.5mm venturis for his stockport 12A and long primary exhaust etc, which had more power and ran better than his RB Holley 465. I'd say that my carb with the max venturi size of 25.35mm* is more powerful than an RB Holley 600 if I am NA (Nikki almost could break them loose in gear on dry road which the Holley could never do). If I swap out the long primary for a turbo, the Holley isn't even in the same league anymore. Plus the RB Holley I have is not a double pumper, and the air bleeds are not adjustable, so forget boosting it.
*I've found 25.35mm to be the biggest primary venturi size that works with the factory transition circuit on a 74 ported 13B (which obviously pulls more cfm at the same RPM as a 12A would so I'd say this size might be too big for a 12A so please don't ask). Plus you still get the lean glitch at around 1700 but the accel pump does cover for it when you drive so it's unnoticed. Wankel-awesome concurs.
Anything bigger starts to have some issues but they are all pretty minor until you get up to 26mm, which I don't recommend at all. It works, but is more of a jungle cat to drive on the street vs a nice tomcat which is what I have right now - powerful, but nice and manageable - like right on the edge of feral which is perfect for me. The factory carb is like an old ***** cat that just can't catch mice anymore. Pisses all over your stuff, and is just a plain nuisance to have around. I'll never run a factory carb on anything.
a) running with no factory choke
b) mechanical secondaries (or no spring like you said)
c) any air flow higher than the stock dinky 20mm venturis allow
The 79-80 carbs are jetted richer and have smaller idle air bleeds (short slows) thus leading to a richer idle and fatter transition circuit. Thus it runs better in a not-exactly-factory-anymore scenario like yours. But if you can really get into an 81-85 carb and recalibrate it the way I do for boost, it runs equally well for NA. It really is shocking how much these tiny factory carbs have in them. Wankel-awesome found this out with just 24.5mm venturis for his stockport 12A and long primary exhaust etc, which had more power and ran better than his RB Holley 465. I'd say that my carb with the max venturi size of 25.35mm* is more powerful than an RB Holley 600 if I am NA (Nikki almost could break them loose in gear on dry road which the Holley could never do). If I swap out the long primary for a turbo, the Holley isn't even in the same league anymore. Plus the RB Holley I have is not a double pumper, and the air bleeds are not adjustable, so forget boosting it.
*I've found 25.35mm to be the biggest primary venturi size that works with the factory transition circuit on a 74 ported 13B (which obviously pulls more cfm at the same RPM as a 12A would so I'd say this size might be too big for a 12A so please don't ask). Plus you still get the lean glitch at around 1700 but the accel pump does cover for it when you drive so it's unnoticed. Wankel-awesome concurs.
Anything bigger starts to have some issues but they are all pretty minor until you get up to 26mm, which I don't recommend at all. It works, but is more of a jungle cat to drive on the street vs a nice tomcat which is what I have right now - powerful, but nice and manageable - like right on the edge of feral which is perfect for me. The factory carb is like an old ***** cat that just can't catch mice anymore. Pisses all over your stuff, and is just a plain nuisance to have around. I'll never run a factory carb on anything.
Last edited by Jeff20B; 02-28-16 at 04:02 PM.
02-28-16, 06:22 PM
#10
Old [Sch|F]ool
The RB tuning leaves much to be desired. It is pig rich all the time. That said they do drive nice out of the box.
Remember that when I had my polk high football moment, it was with an untouched '80 carb with no other tweaks but fuel pressure tuning I would just keep pulling fuel pressure away until it felt "right" driving down the road at 60-65mph. Coincidentally this would also be the best fuel pressure for quarter mile times.
Remember that when I had my polk high football moment, it was with an untouched '80 carb with no other tweaks but fuel pressure tuning
I would just keep pulling fuel pressure away until it felt "right" driving down the road at 60-65mph. Coincidentally this would also be the best fuel pressure for quarter mile times.
02-28-16, 06:40 PM
#11
Yep, I remember.
And yes my Holley does drive well right out of the box. Just only ever "kinda" wowed me though; in the GLC and the brown car, but didn't in the REPU. But back then it had a tiny exhaust, since replaced with a long primary, so I'm sure it will have some wow factor for me if I decided to test it again, but the plan is to do a copy of the Nikki in the brown car. At least then I'd have a tunable carb that can handle boost! And it drives just as well as Holley.
I think these Nikkis are my Polk High football moment! I've peaked and it's all down hill from here.
And yes my Holley does drive well right out of the box. Just only ever "kinda" wowed me though; in the GLC and the brown car, but didn't in the REPU. But back then it had a tiny exhaust, since replaced with a long primary, so I'm sure it will have some wow factor for me if I decided to test it again, but the plan is to do a copy of the Nikki in the brown car. At least then I'd have a tunable carb that can handle boost! And it drives just as well as Holley.
I think these Nikkis are my Polk High football moment! I've peaked and it's all down hill from here.
02-28-16, 06:48 PM
#12
Old [Sch|F]ool
LOL! It's okay, I'm scaring people with my Volvo fuel economy now. I saw as high as 41mpg with my little turbo 2-liter.
Of course it is more like 17-20mpg nowadays... all city driving... if I'm not at idle then I am at 5 pounds of boost, not much motor for a 3200lb car. Think I should get an RX-8 R3 to save on fuel?
(To the OP: Sorry about the threadjack. We're the old farts of the RX-7 community, I guess. Hey where's my 15 year badge already?)
Of course it is more like 17-20mpg nowadays... all city driving... if I'm not at idle then I am at 5 pounds of boost, not much motor for a 3200lb car. Think I should get an RX-8 R3 to save on fuel?
(To the OP: Sorry about the threadjack. We're the old farts of the RX-7 community, I guess. Hey where's my 15 year badge already?)
02-28-16, 07:39 PM
#13
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i've been DD-ing an Rx8 for a while, and so far i've had zero issues since i bought it, and did a little fixin. i've put 30k on it since then too. mileage sucks, but it doesn't behave like a normal car, there are some loopholes. the first one being speed, i get better mileage (ive seen a whopping 23mpg) at 70+ than i do at 65. second, driving around town hurts mileage, but since it wasn't any good to start with, you still get 17-19.
so while you would be the first person to buy the Rx8 because of the gas mileage (most ads feature pics at the gas station), its not as crazy as you'd think.
like i say the Rx8 has been good to me, it handles awesome, and its quiet and smooth. you should expect to go through it, as there are a TON of warning lights, and there will be a bunch that are on. they are all easy to turn off, but these cars are cheap because nobody is willing to even bother trying. just about everything on the car is a 20 minute job, even the interior, so its easy to pull that out and wash it in the sink, Rx8 owners are gross, i've had three and all three were disgusting inside.
*true story, they hired the head of the neck guy at the dealership i worked at, right after i left, he didn't last long.
02-28-16, 07:45 PM
#14
Rotary Enthusiast
Egi-re
I'm not a wrench so I can only tell you my experience. I own a 85 FB. 115k miles, I've had it 11 years. Had 88k on it when I bought it. It was taken care of properly previous two owners so I lucked out. It's my second FB and third overall. First one was a 84gsl 12a. Had 84 SE from 87-92 also and had it from 22k to 82k when I sold it. Never snow never rain on my current one. To the best of my knowledge neither one ever had a single adjustment... Ever. Starts, runs, idles perfect all the time. I know they aren't optimum for performance and that a S4 conversion would be a good upgrade. I don't fix things that aren't broken. As far as I'm concerned the original set up is basically bullet proof. Someday I'll take it to Defined Autoworks and let them decide best way to upgrade tastefully and reliably to keep it NA and get more HP. Till then mine still pulls hard and gives me a great feeling. Have no idea what compression numbers are but again, I've logged plenty miles on all of mine and know my 7 well. Also the GSL was 101 HP stock new with a original Nikki carb. It had a manual choke and I loved it. Very reliable. Just had need for more HP. The guys in these forums do amazing things with rotaries. I think Japan did an amazing thing just plain stock. Change oil and filter every 3500 miles with the best oil possible ( and proper weight for climate) and keep the radiator juice clean and up to level and my experience says you'll get a ton of damn fine driving miles on it. Just be aware of who you're buying it from and get as much background on it as you can.. Good luck.!!
02-28-16, 11:14 PM
#15
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If you happen to live in a state with a Smog Check, The EFI SE's are much cleaner and have an easier time passing smog. My SE with 147k was so clean last time the technician was shocked.
02-29-16, 01:42 AM
#16
84SE-EGI helpy-helperton
For the 'purist EFI' opinion up in here...
The Bosch L-Jetronic was licensed by just about everyone back in the 80's for being a simple air-measurement system with a minimal of computing required. Intake air temp sensor, water temp sensor, and the AFM and Tach are enough to keep the engine breathing well and performing to expectations related to 135hp, stock. There are only 2 injectors (680cc each) and they're on a single rail which is easy to maintain. Since there are only 2, and each one feeds one rotor, that means any injector problem will quickly be noticed in one rotor not pulling it's weight. Regular (every 4-5yrs) cleaning of injectors helps performance, but may be overkill for a DD.
The AFM is rock-solid. It's sealed well, and works as it should. The ECU is factory programmed for fuel mapping which runs in open-loop under acceleration, and closed-loop in 5th gear steady state cruising. This is what gives better fuel mileage over most STOCK carbeurated engines, even with the 12a of lesser displacement.
I owned an 80LS for many years, and got used to tuning the carb. I was hesitant to dive into EFI, but now that I'm there, it's far simpler than the monkeying I was doing with the carb to keep it running well. In truth, I would never go back at this point.
Don't let EFI scare you off of an -SE. Sure there are idiosyncracies to it, but every car has these, and the early EFI systems being so simple, are usually trouble-free due to their simplicity.
The Bosch L-Jetronic was licensed by just about everyone back in the 80's for being a simple air-measurement system with a minimal of computing required. Intake air temp sensor, water temp sensor, and the AFM and Tach are enough to keep the engine breathing well and performing to expectations related to 135hp, stock. There are only 2 injectors (680cc each) and they're on a single rail which is easy to maintain. Since there are only 2, and each one feeds one rotor, that means any injector problem will quickly be noticed in one rotor not pulling it's weight. Regular (every 4-5yrs) cleaning of injectors helps performance, but may be overkill for a DD.
The AFM is rock-solid. It's sealed well, and works as it should. The ECU is factory programmed for fuel mapping which runs in open-loop under acceleration, and closed-loop in 5th gear steady state cruising. This is what gives better fuel mileage over most STOCK carbeurated engines, even with the 12a of lesser displacement.
I owned an 80LS for many years, and got used to tuning the carb. I was hesitant to dive into EFI, but now that I'm there, it's far simpler than the monkeying I was doing with the carb to keep it running well. In truth, I would never go back at this point.
Don't let EFI scare you off of an -SE. Sure there are idiosyncracies to it, but every car has these, and the early EFI systems being so simple, are usually trouble-free due to their simplicity.
02-29-16, 07:24 PM
#17
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this is true. i mostly smog rotary cars, and they all do really well. occasionally i have to smog a piston car, and they usually pass, but they are rarely as clean as a rotary
02-29-16, 09:07 PM
#18
LongDuck,
I recently acquired an '85 GSL-SE, what was you main source on info on the EFI system and ECU programming? I think I've seen a few books mentioned on the Bosch EFI, but don't remember them off the top of my head. I'd like to develop by understanding of the stock system.
Thanks!
Patrick
I recently acquired an '85 GSL-SE, what was you main source on info on the EFI system and ECU programming? I think I've seen a few books mentioned on the Bosch EFI, but don't remember them off the top of my head. I'd like to develop by understanding of the stock system.
Thanks!
Patrick
02-29-16, 09:25 PM
#19
84SE-EGI helpy-helperton
<img>http://www.sierramadrecollection.com/images/products/124800.jpg</img>
Theres some information in the Factory Service Manual, as well. If you don't have a printed copy, they're available for download on a quick search.
Theres some information in the Factory Service Manual, as well. If you don't have a printed copy, they're available for download on a quick search.
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