Pinfield357

what causes the secondary injecters to come online? RPM or boost i have and 87 turbo 2... and another question for ya i dont have the cash right now for an S-AFC. can i just get a walbro fuel pump and just install that to give me a little extra fuel? all i wana do is get a cool air intake (cone filter and mandrel bent alum. TID), a DP, a high flow cat and eventually N1 duels. im not diong this all at once over time thats my eventual goal. first will most likely be the intake

604

As far as I know, the secondaries come on right after the primaries drop from about 95-100% output to 80% and then down even further... that usually is about 3900 to 4200 RPM as calculated by the ECU. I know that the 6-port actuators on an N/A open up right around then too, so I can't imagine it would be any different for a TII. However, if you throw a higher flowing fuel pump in there, I don't think that will do anything if you haven't put larger injectors in there, but then the MAF sensor and the O2 sensor will send different information to the computer and therefore slightly change your fuel/air mixture/curve. If you install larger injectors, they will spray more fuel, plain and simple. If you have added a larger fuel pump, that will ensure that you never run too lean and with a TII that's not a good thing as you may detonate. If you want to finely tune the mixture and control the output of the injectors, you will have to get an S-AFC or something similar like a Wolf3D or something; the stock computer doesn't control or do anything about the fuel flow coming out of the injectors as far as I know.

Don't take this information as 100% accurate, but I think I'm pretty correct. I just noticed that no one was responding to this post so I thought I would give it a try. Did I answer your questions?

Pinfield357

lol yeah it helped neone else have any ideas???

HAILERS

Uh, I don't agree. The secondaries come on due to two things. One is approx 3800 rpm being reached combined with a LOAD. The load is sensed by the boost/pressure sensor. You can drive your RX whatever, under light load, in third gear to six grand, and the secondaries WILL NOT open, unless there is a load sensed by the boost/pressure sensor.

If you take the same scenario but slam the throttle full open, as soon as you reach 3800 rpm the secondaries will open and the primaries at the same time will cut their duty cycle back(but remain engaged).

If you doubt any of the above, get a wire tap for about fifty cents from RadioShack , tap into one of your secondary wires at the ECU and put a meter on the wire. You will see 12v as long as there is light load on the engine. But if you stab the accelerator, you'll see the 12v turn to approx 7volts or less when you hit 3800 rpm.

Also read this http://home.earthlink.net/~burntoast/3700.html
and pay attention to the way he describes the action of the primary and secondarys.

Also there is a free download of the 89 factory service manual at http://www.fc3s.org and if you read the fuel section there is a relationship chart. You will learn tons if you read it. Have a good time.

HAILERS

and this:

HAILERS

andthisandthis

HAILERS

And after reading that, remember this. If you are putting fuel injector cleaner in your tank to clean the secondary injectors.......it just ain't happening. Those lazy sucker are only open less than ten percent of the time.

There is a way around this. If the boost/pressure sensors vac line is disconnected, the secondarys will come on at 3800 each and every time. So run at 70mph in forth gear for a couple of hours and they might get some cleaning. At least the lazy bums will get some exercise. Don't ever boost the car in this configuration.

akageals

Hailers,

I don't mean to dispute you (I know you know more than me) but, your advice is contrary to my personal experience. I had a bad secondary injector (would not operate at all). Everything you said about load and RPM is exactly as I experienced it. My car would "miss" badly above 3800 RPM IF there was a load on the engine. Now....for the disputed part....I unplugged my boost sensor and it kept the "missing" from occuring BUT the car had very little power above 3800 RPM. SO....unplugging the sensor seems to have kept the secondaries from opening AT ALL. I replaced both secondaries and the car has run perfect ever since. So....don't mean to say you are wrong about that but it seems to go against what I experienced.

Todd

PS. My car is an '87 TII

HAILERS

Akageals.....I pulled the vacuum tube, not pulling the plug. This make sense now?????

I wrote this same description last weekend but it got erased in the BIG DUMP of this site monday or tuesday.

Before I wrote anything, I put a meter on my primay and secondary wires , then pulled the vac hose. It worked as I described in the first post. Always the secondaries came on line at 3800rpm and stayed on over 3800rpm if the boost/pressure sensors vac line was removed.

I'm curious. Do you mean you unplugged the connector or the vac tube???? I think thats where the difference is.

Try putting a wire tap on your secondaries wires at the ECU and observe with the vac line on and then off as you cross into 3800 territory.

P.S I did it on my 87N/A and the 87TurboII last weekend or Monday, I lost track of time.

Oh. I doubt I know anymore than you. I have just done this particular checkout several times on two different cars, so I feel confident in what I wrote. I don't know a P trim from a wastegate.

604

That's interesting. I just don't understand how there's a LOAD when the car is in neutral and you blip WOT to 7800RPM... do you mean to say that the secondaries would NOT become engaged in that case [even to only a 40% or less duty cycle??], and ONLY if the car is in gear?

Also, what about N/A? There's no boost sensor obviously, and I know that the duty cycle is calculated by the only other sensors the N/A 2nd gen has, so perhaps it's different for an N/A?

Pinfield357

well that is exactly what i was looking for about when they come online but what about if i just put in a walbro fuel pump and do nothing else will i get more fuel to the motor or will the presure regualter hold it back???

HAILERS

604.......I did not ever mean to imply that you could rev the engine while sitting still and the injectors would come on at 3800rpm with the vac hose off the boost sensor. The SCENARIO was driving the car. Not sitting in the driveway.

It cost only about fifty cents to tap into the secondary fuel injector wiring and about three minutes to pull your vac line off your boost/pressure sensor.

Attached is a jpg of the haynes manual and testing of the secondary injectors.

Pinfield357

not to interupt but can some one please answer my question will getting a walbro fuelpump put more fuel in my motor or do i need bigger injecters too and an SAFC to controll them

604

Pinfield,

I'm pretty sure that with the [I assume 255 Walbro] fuel pump being the only upgrade to the fuel system, the pressure regulator will maintain the same rate of flow through the injectors as normal. I guess it also depends on how many other modifications you have and if your fuel consumption is higher than stock right now too. Hailers? What do you think, you're the expert.

I don't have any experience with TII's, so is there even a "Pressure Sensor" on an N/A? How do you test the injectors while under load then, A.K.A. a moving vehicle ? I guess on a dyno is the only way -- do you have that test in the manual for an N/A?

HAILERS

Not a expert nor a guru, and I don't have a waldo. What I have read from Reted, is that the car will run rich in the lower range i.e. idle. I never quite figured out why that is if the fuel pressure regulator is working, but then again I don't know a lot about fuel pressure regulators, I've found out..

A while back I put a fuel pressure gauge on my windshiel wipers and tee'd into my fuel line. I noticed to my surprise that when I was hard on the boost, the pressure rose to close to 50psi. HUH?? I had thought the fuel pressure was supposed to be approx 40psi. So I got in a rut, thinking all these people were wrong about the 40psi being tops.. but I *thinK* I've been straightened out about that misguided thought. Its been explained to me that the pressure will rise in proportion with the boost pressure. So in effect, the pressure really is 40psi in the rail vs the pressure in the intake. Make sense????? I'm probably still confused.

Anyway, I do believe from what I read on this site, the Waldo will make you run rich at idle. I guess the volume of the pump overwhelms the regulator. Just speculation on my part. At least this will bump you to the top.

HAILERS

604.... According to the 87 factory service manual, the turbo has a pressure sensor....but the N/A has a boost sensor! Go figure. Download the fsm at http://www.fc3s.org just download the Fuel section. There is a checkout of the boost sensor for a n/a and a pressure sensor for the turboii. They are calibrated different from each other.

Only way I ever check the injectors out is to put a Fluke88 meter on the wires at the ECU and watch the duty cycle, or at times I've just put a regular meter on the wires at the ECU and watched the voltage drop as the injectors come online. Just a hobby. Something to play around with.

I really don't know what exactly what you mean by checking them out. I have put injectors on a spare rail and run a fuel line to the rail and pulsed the injectors. Watched the flow rate. Much like in the manual.

Lately discovered that a fuel injector on a 86-88 will fit on the bac's plug(or vice versa). The bac has a duty cycle, it runs at approx 125hz. So the injector will pulse if its hooked to the bac plug and the car is running. Someday I'll do something with this idea. Just a hobby, toy etc. Have not toasted the ECU doing this yet.

Pinfield357

if your right and at indle ill run rich because im just overwheling the preause regualter wouldnt i still do the same at say 6000 rpm under boost. see when all is said and i down i will probably be runing around 10-11PSI boost and i just want some more fuel in the motor under that much boost

akageals

Hailers,

I unplugged the electrical plug...not just the vac. line. I guess that is where the difference is.

Todd

HAILERS

Pinfield357........yes. I'm sure thats why they go to the WAlbro. To ensure that they don't get a fuel pressure drop while in the higher boosting ranges. Evidently if you get a fuel pressure drop the mixture gets lean which in turn causes detonation which causes apex seals to break which causes long faces and down turned mouths.