blown 944

I have been running around at about 22 psi after fixing my bad injector ordeal.

Tonight I tried to turn it up and I am having an issue with the link setup. It only reads up to 240 KPA ( I assume this is about 24 psi). Looking atthe manual it only has cels going to 240 KPA. Once it goes over 23-25 psi it will just cut fuel.

Other than that problem it is running absolutely great .

I realize the link setup is not the most popular but it is running very nice and is easy to manage.

Any ideas on how I can clamp the boost pressure at say 20-22 psi. So the link can't se more than that??


I have a separate fuel setup for running high boost (comes on at 15 psi)and it works great but I just need the DME to keep doing it's thing w/o cutting fuel.

any help is appreciated

333pg333

Sid, which LINK setup are you using?

tommye

240 kilopascal = around 35 psi.

Tommy

blown 944

It's the old AFM link.....................I know.... I know

this is the first time I have ever messed with signal massaging. It is working flawlessly with the E85 so far.

blown 944

The way this thing sees it atmosphere is around 100 kpa. Not sure how that works but it is round 23-24 psi by my guage at the highest it will let it go

gt37vgt

it's easy to scale back a boost signal put a T piece in the line put a mig wire contact tip in the line to the map sensor you are sending the signal to and on the other leg put a needle valve then a return to the air filter when the needle valve is closed the signal will be the same when the needle valve is open as much as the mig tip half the signal is lost through the needle valve and the signal to the Map sensor will be halved as you close the valve you are able to scale this signal as you like . this is the old school set up for a boost increase on the waste gate line

Duke

When I tried tune a AFM link for high boost a long time ago (4 yrs?) I wasn't able to get more than around 1.2-1.3 bar without cutting out.

The problem is output voltage from the AFM Link to the DME.
The AFML maxes out at 5 volt whereas the DME doesn't want more than 4.7 v.
Unfortunatly the voltage clamp on the out from the AFML is not stable! The higher voltage still spikes through for split seconds.

So the AFML still sends out too high signal to the DME - which thinks you're overboosting and cuts fuel.

You're gonna have a LOT of work ahead trying to get the AFML running with high boost.

Rogue_Ant

Sid,

I suggest talking with eniac. He is running high boost with the Link setup.


-Rogue

gt37vgt

I hereby challenge you to solve this problem for less than $50 . and i think you'll do it with resistors and restrict ors you can scale dale any signal

blown 944

Duke,

If that is the case I can actually put a resistor/MAP clamp (not sure if it truly a resistor but more a MAP clamp like is being used on NA Mitsu's and dodges) in line between the link and the dme so it will never see more than 4.7 no matter what the AFML puts out. I actually hope that is it, that would be a very easy fix

I am not sure that is it though, but that is a good place to start.

If I can get through this, I believe I can. I don't think it is going to be too bad to use, but I am not really using the link above 17-20 psi other than needing a stable signal for that boost level. Over that the mechanical pressure takes over that is the way i have been doing it on small injectors for some time now.

GT,
I was up last night coming up with something like that in my head. I just have to figure out what type of needle. I am thinking about using a poppet valve off of my old enderle mechanical fuel injection setup. It is quite overkill for this application but it has some great adjustability with the springs and spacers that are used. It is also designed to be used at anywhere between 10 and 100 psi.

Rogue,

I have contacted him via PM.

cpt_koolbeenz

Try this...
http://en.wikipedia.org/wiki/Linear_regulator
with this: 1N4732A
http://physics.gac.edu/~huber/classe...ts/1N4735A.pdf

I got more ideas, but no time right now... Lets talk soon!

Rogue_Ant

Sid,
If you just want to limit voltage, then a Zener Diode will work fine. It will shunt any voltage over whatever the diode is set for.


-Rogue

eniac

If the 4.7v is the problem then it seems quite easy to solve. Either a voltage limiter inline between the Link signal and DME or a MAP clamp in the vacuum line to the LINK which would scale everything down some. Also, I had Russel burn my DME chip and made sure he knew I was planning on running 35+ psi. The only time I get cut out is when I run too much boost with too low of octane. I always assumed this was a timing/knock issue.

Try it in full TPS mode and see if it still cuts out. Is it just cutting fuel, or is it switching to "limp mode" where you have to turn the car off and back on to reset?

When I get a chance...sometime this week, I will check the voltage to the DME and see what it's sending at what boost levels. I'll try it at higher boost with 93 octane gas to see if I can get it to consistantly cut out at 4.7v.

blown 944

Zener diode ....is what I'll try first. Thanks

I don't think that is it though as it seems to me that what is happening is once it surpasses 240 kpa on the link it cuts fuel b/c there is no higher cel for it to send the corresponding signal (voltage).

I will take it out today and watch the voltage screen and then watch the map screen and see where it is at on both. My suspicions tell me I will see it cut at 240 kpa and not at voltage.

It definately is cutting fuel and there is no limp mode happening. I can literally take it up and over the 24 psi and let it cut and then ease off the throttle a bit and then modulate it at around 23 and all is well.

I have had a trouble with the TPS mode. I tried it and it was way rich. The map mode is working good.

RPHARRIS

Kerchoff's laws ...loop rule ...junction rules ...nope i got nothing haha good luck!

...on second thought, megasquirt's power circuit clamps sensor voltage at 5v, maybe you could study and copy / modify this circuit somehow?