Ok i just turbo charged my '86 gxl I used my intake manifold and just customized the lower part and made a small exhaust spacer for fuel i used 550 primaries and 680 secondaries and a walboro 255 fuel pump apexi s-afcII and an adjustable fpr. I used stock computer and everything else. Now my problem is when my secondaries come on(or dont come on) at 3800rpm's my car starts missing reall bad, it doesnt even want to rev past that really but when its in neutral it will however i replaced my resistor pack thinking that was it. and i dont know what else to check. sorry to post this but i did read over all the 3800rpm posts and nothing answered my problem.

 

maybe your secondaries arent oppening correctly?and/ or try grounding your ecu,alt...

 

will the stock ECU allow for turbo? i figure it would freak out when sensors register PRESSURE in the intake system... (instead of vacuum)

 

yes the stock comp will run with a turbo it just dumps all the fuel it can and with the s-afc i tune it down. and i already have extra grounds ran but your right i dont think my secondaries are coming on. the problem is i dont know why they aren't coming on.

 

please someone give me some ideas

 

is the RX7 secondary runners vacuum controlled or electronically controlled?

if it's vacuum, do a simple vacuum test on the hoses...if it's electronic, pick up a repair manual at any parts store and test the proper parts.

 

all of the s4 fc3s have ecu that cuts fuel somewhere around 4 to 5 rpm you might want to check rx7.com they have fuel cut chip thing. it's eleminates this problem

 

no it has no chip and i test the plug ins for the injectors and they have power but i dont know i dont think they are getting signal i want to run a new signal wire from the computer for them but i dont know how to wire them through the resistor pack

 

ok i tested the resistor and it has one power wire going in and four going out to the injectors so im guessing the ecu sends a ground for the signal but i have no clue how to test this maybe someone could help me out here

 

Secondary injectors don't/won't open unless there is a load on the engine sensed by the pressure/boost sensor. That does NOT happen in the driveway. Only driving under load. UNLESS....you disconnect the vac hose from the sensor and plug it(at the hose), then the secondarys will come on each time you reach 3500RPM. Even in the driveway. It's in the fsm.

You NEED to download the fsm off the net.

Personally........I think that car will BOGGGGGGGGGG down as soon as the secondarys come online. Just my opine. I know nothing about turbos.

Backprobing the secondary injector wires AT the ECU with a meter....and then going for a drive and punching it...should show a drop from approx 12v down in the five or six volt range....depending on how hard you are punching it. At light throttle the voltage will not drop but stay at approx 12v or whatever your alternator is a puttin out.

 

yeah i know bout the underload and all of that when i am driving the car hits 3800 and its like a damn rev limiter and for the bogging i have an adjustable fpr that i turned the pressure down some with and i have an apexi s-afcII that i turned the injectors down some with.

there are two wires that go to each injector one has 12v what is the other? what does it come from? i was thinking that it was the signal wire and that the ecu grounds the injector to turn it on and off but i dunno

hailers you helped a guy back in 02 in a post. he had a similar problem im having but he never said what fixed it in the post. i was just wondering if you might remember

 

and i can take it past 3800 if i ease it past or if its in neutral and i also unplugged the secondaries and tried it and it acted the same way

 

The ECU controls the injectors by putting a ground on the injectors. ON, Off, ON, OFF rapidly.

So the 12v is a good sign. And you know the ECU is doing good on controling the primary injectors.

I KNOW what I'd do. I'd put the positive lead of a digital meter in the back of pin 3F or 3H and go for a hard drive and monitor the 12v you will see on either of those two pins. It should drop off waay down in the 5 or 6 volt range when the 3500 rpm is reached.

Either that or disconnect the vac hose from the pressure sensor and do the same thing in the driveway and rev above 3500 rpm. I don't think the voltage drop will be a great as the above example....but should drop quite a bit.

If it's just a hesitation thing.....then check the ground wires for the ECU. At pins 2R, 3A, 3G,2C. If it's just the hesitation thing at approx 3800rpm then things should have gotten better after 3800 and it should have rev'd ok after the hesitation.

You really NEED to check out to see if the secondary injectors are coming on line at 3500 as described above. If they are...then either the mixture needs some leaning/riching up/down or it's the hesitation thing that many experiece at 3800rpm.

You know, I've got a spare series five turbo and I've been thinking about putting it on the wife's 86n/a just for something to play with. Keep up the good work.

 

Oh. Are the secondary injectors of the low resistance type?????They should be about 2.3 ohms on your car with a 86 ECU. If they are the high resistance type, 12ohms or so, then that might compound your problem.

 

well my secondaries are 680's out of a gxl se so they are low but i do not know how to check for ohm's i have the multimeter thing but i dont know how to check for ohm's but i did try other injectors in the secondary spot thinking it might be faulty injectors and it did the same thing

so the ecu pin outs for the secondaries will have 12v then drop once the secondaries come on?

 

and no its not a hesitation its like they are not coming on at all

 

If the injectors are for 88-91 they are high resistance.
86 and 87 have low resistance.
Hope that helps.

 

Those 680 should be low resistance. Put one meter lead on one contact of the injector and the other lead on the other contact on the injector. Put the meter on ohms and it should read approx 2 ohms.

Yes, the secondary injectors should show approx 12v until the engine hits approx 3500 rpm, then the figure of approx 12v should turn into some way lower figure like around 5 or 7 volts. It'll be noticable.

Pins 3F and 3H are in the small plug on the ECU. With the plug connected, they are lettered from right to the left, counting in a up down way. Like 3A is the top right wire....the one just below it is 3B and keep counting like that from right to the left til you run out of wires.

Using the meter, you won't hurt the ECU. But if you take a piece of wire and ground out any of those wires....kaput goes the ECU.

Just put the meters black lead on a ground like the hold down bolts for the ECU and the other lead up the back of either of the pins above. Then go for a ride and see the voltage drop when you are on it AND above 3500rpm.

 

ok tested it and both of them were going from 13v to 11v at 3800 or when i hit my brick wall. so what does that mean?

 

check to make sure the connection to the injector resistor box isn't covered in oil. In a couple cars that i've worked on, this was the problem. The owner spilled some brake fluid on the injector resistor box while filling their brake reservoir. I sprayed it all down with some brake parts cleaner, reset the ECU, and everything was fine.

make sure all the connections are clean and tight. If they are, they start ohming out the injector resistor leads.

 

I just replaced the resistor box and everything "ohms out" fine.

 

***ok tested it and both of them were going from 13v to 11v at 3800 or when i hit my brick wall. so what does that mean?****

To me that means the secondary injectors are NOT coming online. If the wiring ohms out (rings out) b/t the ECU and the injectors, and the injectors plugs are on the injectors....then it seems to me the ECU transistors are toast i.e. they are not pulsing a ground to the injectors to turn them on (secondary injectors).

Try one more time, but this time get the engine gently over four thousand rpms, then stomp the pedal. IF the voltage does not drop into the 5-7 volt range but apes what you wrote in the above post.....then the ECU is shot.

 

i thought of that and put in a different ecu and it does the same thing

i was thinking that maybe an ecu ground is bad and it cant ground the injectors very well because it does drop cosistently from 13 to 11 at 3800, what do u think? does that sound logical? i mean for the ecu to ground the injectors the ecu would need a good ground for itself right?

 

Makes sense. THE major cause of 3800 rpm hesitation IS grounding of the ECU. Not the chassis of the ECU, but its ground wires.

Those ground wires are loacted on the top of the rear rotor housing. Located on a ring terminal and held on the rotor housing with a 10mm socket size bolt.

Whatever you do...don't ground one of the injector wires or kaput goes the ECU.

An alternative way of grounding the ECU ground wires....is to access the ECU plugs......strip back the overbraid on the harness for about a half foot to one foot from the plugs where you'll see some black wires spliced together. At that point a person can either crimp on or solder on an additional wire to those and then terminate that new wire at say the attach bolts/nuts of the ECU, or any other confirmed well grounded spot.

Personal experience tells me there is something else wrong. On any of my cars, when I stomp the pedal over 3500 rpm....the secondary voltage will drop like a rock to around 5-7volts.

What might be interesting is to backprobe one of the PRIMARY injectors and go for a ride. That voltage should drop down also but most all the time when your on the pedal. During hard running I remember seeing the voltage drop waaay down in the low numbers, like 3-4 volts before the secondaries come online. Try one of the primary injectors sometime and see what you get. Pins 3C and 3E

 

ok ill try that tonight but can i do this without driving the car because last night when i was testing something my differential went out and i dont feel like putting a new one in 'til i fix this problem