Zener Diode FCD question

[ArmandoP]

Im not a lazy sponge, Ive been fighting this issue all day and have come to the conclusion that there is nothing phisically wrong with the car, so I need some help in resolving the symptoms.

I want to dyno my 89 turbo before going to the LEX AFM and 550's. The problem is Im now hitting fuel cut at anything over 4200RPM, without a boost controller. Ive removed all my charge pipes and redone them with new couplers and I am positive there are no boost leaks anywhere.

What I would like to do is run an FCD instead of the lex and 550 combo so I can dyno this thing. Now, I dont want to spend $100 on an HKS FCD because it will only be on the car for a couple of weeks max.

When I was playing with MR2s there was a well documented fuel cut defencer that could be made from a zener diode. http://toymr2.tripod.com/fcd.html I know the wires are different in the supra, so I am assuming the same diode will not work. Can anyone give me some info on how I could apply this mod to the supra for the next dyno session? Can anyone come up with a better solution that will allow me to runt he car on the dyno without hitting fuel cut? Is it even possible to increase efficiency to the point that the car will hit fuel cut on the stock turbo with no boost controller or am I crazy?
Thanks in advance.
Armando

mod list if it matters: ARP head studs, Trust MHG, NA cams, BIC DDP, 4 inch custom exhaust, electric fan conversion, removal of EGR, aluminum intercooler pipes, Tial BOV, stock CT26.

 

[mkIIIman089]

You are correct, IIRC the AFM in Mr2s is one that sends a voltage signal. Ours (in turbo form) send out a frequency signal.

Is it even possible to increase efficiency to the point that the car will hit fuel cut on the stock turbo with no boost controller or am I crazy?

Haven't you just made it hit fuel cut with no boost controller??

You obviously know what you can do to get around fuel cut, why don't you just wait 2 weeks to do the dyno when you have your Lexus AFM setup in? Instead you're willing to risk blowing it up with the less expensive FCD because you're impatient. Seems very wasteful to me.

EDIT: I don't know why I waste time answering answers for people like you. A lot of this has probably been posted in your other thread on nearly the exact same topic...

 

[ArmandoP]

You are correct, IIRC the AFM in Mr2s is one that sends a voltage signal. Ours (in turbo form) send out a frequency signal.
Haven't you just made it hit fuel cut with no boost controller??

You obviously know what you can do to get around fuel cut, why don't you just wait 2 weeks to do the dyno when you have your Lexus AFM setup in? Instead you're willing to risk blowing it up with the less expensive FCD because you're impatient. Seems very wasteful to me.

EDIT: I don't know why I waste time answering answers for people like you. A lot of this has probably been posted in your other thread on nearly the exact same topic...

 

[ArmandoP]

you bother answering questions for me because I have a purpose for doing this. Im not lazy. Im not impatient. I want to find out exactly what the new exhaust is worth on the dyno. If I throw the lexus and the 550s in then I wont exactly have an accurate measure of that will I? Or did you not READ that and simply answer a question for your own ego gratification?
Waiting two weeks is for the dyno appointment, not the AFM and injectors.

So next time smarty, instead of letting your ego get the better of you, and assuming you know my thought process you should simply ask if I have a purpose for posting a second thread.

The purpose behind posting this in its own thread for people who dont have ego's the size of texas is below.

The other thread did not have a topic clear enough for the zener diode question. AS a matter of fact, I couldnt find any mention of the zener diode in any of my searches, so I thought it might be a good thing for future searches to have it in its own thread. Seeing as I know Im not the only person in the world to have gone from 4age to 3sgte to 7mgte and carry my habits from engine to engine, I figured this would be a useful thread for answering future questions on this topic. Which btw, is entirely different than a "hey, check out my new exhaust" thread.

So Mr. Smarty Pants, Im sorry youve had a bad day and decided you would try to take it out on me.
Have a great weekend, Im sure theres alot of other 19 year olds you can go play with who will actually be offended by you...

 

[mkIIIman089]

If I throw the lexus and the 550s in then I wont exactly have an accurate measure of that will I?

Why's that? All you're doing is adding more fuel to go with the more boost (what makes the extra power) that your new exhaust gave you.

Waiting two weeks is for the dyno appointment, not the AFM and injectors.

You said the max the FCD would be in was 2 weeks, to me, meaning you would have your Lex/550 combo to replace it in 2 weeks. Or did you just want to put one on, dyno, then take it off and leave it?

The other thread did not have a topic clear enough for the zener diode question. AS a matter of fact, I couldnt find any mention of the zener diode in any of my searches, so I thought it might be a good thing for future searches to have it in its own thread. Seeing as I know Im not the only person in the world to have gone from 4age to 3sgte to 7mgte and carry my habits from engine to engine, I figured this would be a useful thread for answering future questions on this topic. Which btw, is entirely different than a "hey, check out my new exhaust" thread.

You also added "except fuel cut" in the thread title, implying you're asking a question about getting around fuel cut after you put on your new exhaust. As I said in my 1st post, they use different types of air metering systems, and that mod will not work. You need to clamp or scale a frequency, not as easy as simply popping in a resistor.

Since you've brought a topic like my age into the thread, whats stopping me from saying something about your heritage? Which, judging by your name I could easily attack.

 

[ArmandoP]

Why's that? All you're doing is adding more fuel to go with the more boost (what makes the extra power) that your new exhaust gave you.
You said the max the FCD would be in was 2 weeks, to me, meaning you would have your Lex/550 combo to replace it in 2 weeks. Or did you just want to put one on, dyno, then take it off and leave it?.

ding ding ding. Wouldnt it be nice to know exactly how much of an effect any given part has on the power curve? The lex and 550's are their own mod, they deserve their own testing and documentation. Guess what, I will do the exact same thing after removing the FCD and installing the LEX and 550's. Then again after I remove the CT26 and install the Turbonetics CT26 clone. and again and again and again. and when Im done and I move on to the next car like Ive done a dozen times now. I will have learned something that I can apply in some way to the next car. and Im aware of the fact that in the process I will likely blow up an engine or three... like Ive done a dozen times now. The end result? there arent too many people who have pulled 270 at the wheels out of a stock bottomed 4age, and I was one of the first ones to do it.
fyi, the two weeks means that is when Im going to the dyno and will be installing the LEX and 550s shortly thereafter, or maybe even at the same dyno session if time allows.

You also added "except fuel cut" in the thread title, implying you're asking a question about getting around fuel cut after you put on your new exhaust. As I said in my 1st post, they use different types of air metering systems, and that mod will not work. You need to clamp or scale a frequency, not as easy as simply popping in a resistor..

You answered the question in an intelligent and thoughtful manner just like you did the first time. Thank you. Im sure somewhere along the line, someone else will be thankful as well. There is ZERO sarcasm here.
By adding the term fuel cut to my other thread I was able to spend the rest of my day looking for boost leaks. That problem no longer exists. This thread is specifically about the zener diode or any other method of accomplishing that same result for the purposes of documentation and testing.

Since you've brought a topic like my age into the thread, whats stopping me from saying something about your heritage? Which, judging by your name I could easily attack.

Because when I was 19 I was just as cocky and all-knowing. Go ahead, look up some of my posts in the MR2 community from 8 years ago. Im no stranger to your point of view. You sir, have never been Cuban and can't speak from experience on the matter... or let me guess... you thought I was mexican?

whatever, thanks for answering the question. truce?

 

[Jaguar_5]

Just an idea, use a good boost controller to ensure you actually stay at stock boost?

Although the more I think about it, it sounds like there just isn't enough flow out of the wastegate to match the rate that the pressure coming out of the turbine rises, so the boost creeps up... Guess a boost controller won't work, just thinking out loud here...

I guess you could port your wastegate, but then you'd probably need a new flapper, doesn't sound like the amount of work you're going to want to do for this situation!

 

[wiseco7mgt]

my two cents worth is have your wastegate actuator checked in case its not functioning properly, maybe a previous owner added washers behind the two bolts that hold it to the turbo.Also, it might be worth checking the wastegate making sure its opening properly.Sounds like all common sense stuff but its all pretty important if your about to put it on the rollers.Please understand that many members value there cars and hate to hear about people that are willing to carelessly run the risk of detonating there engines due to either inexperience or ignorance.Hope you solve the problem before you take it on the rollers.:icon_bigg

 

[drjonez]

the MKIII's AFM output is a frequency, a diode type FCD won't work.

 

[jetjock]

So many morons, so little time...

 

[ArmandoP]

Ive had the entire head off and thus the turbo and actuator in my hands. it has not been modified in any way.

You know, this car is a toy for me. If I blow it up, Ill rebuild it. Thats not to say I will do it on purpose. Of course not, Im not a glutton for punishment. I am however willing to take a calculated risk for the sake of testing and documentation. I just never thought I would be attacked from various directions for wanting to document the progress of my build.

Dr Jones and MKIIIMan, thanks for the answer. I will be looking into another way of acomplishing what I want to do without skewing the results.

 

[Adjuster]

Leak more air. See my answer in your other post on the exhaust.

More air past the AFM = Higher boost pressure before FC is triggered in most cases.

Downside is you are not adding more fuel besides what you get from more pressure on the regulator.

This can make you run lean at higher boost pressure, and that will FU your pistons in short order.

 

[mkIIIman089]

If all you do is leak more air the ECU will compensate pretty quickly and you'll be right back at square 1, just with a leaky intake. LOL

 

[ArmandoP]

If all you do is leak more air the ECU will compensate pretty quickly and you'll be right back at square 1, just with a leaky intake. LOL

yup. that is exactly what happens

 

[suprra_girl]

i just bought a hks fcd, well worth the money for me. I was prepared for what would happen with the fcd tho, i wasn't stupid enough to just wind boost up etc.
The first thing i did when i got it installed was off to a dyno.
With a 46 trim ct26, 3" exhaust stock elbow, 2.5" i/c pipes with a random 2" one in there lol and bigger ic and pod filter i got 278rwhp on 9.6psi, i could not run any more boost than that as i was running the stock fuel system, i don't know which couldn't keep up but my fuel was stable at 11.7:1 and i didn't want her to lean out so 9.6psi it was and it stayed... never had a problem with the fcd
And when i did get a boost leak, i did still get fuel cut lol

 

[mkIIIman089]

And when i did get a boost leak, i did still get fuel cut lol

Thats VERY interesting. You're the only one I have ever heard say this, and I tend to believe even one person who has actually experienced it over all internet hearsay.

Good info!

 

[ArmandoP]

Thats VERY interesting. You're the only one I have ever heard say this, and I tend to believe even one person who has actually experienced it over all internet hearsay.

Good info!

If I remember correctly the FCD will allow to relocate your fuelcut.

 

[mkIIIman089]

Up until now (never having used one myself) I had only heard from the tools in the Supra community that it only clamps the signal and thats it.

 

[suprra_girl]

well... me mum remembers her very first experience with fuel cut in my car lol... she literally crapped herself hahah
it cut at about 12psi, my hose from the comp housing to wastegate had melted. Once diagnosed i just cruised to my destination so i could replace the hose and boost again!! hehe

 

[mkIIIman089]

she literally crapped herself hahah

Uhh...:runaway: