missing link

[civicstyle]

Does everyone who has a turbo setup have a missing link or something else. I got the edelbrock kit and it comes with a resistor wire to keep the map sensor from seeing boost. I dont think this is worth a flip though and ordered a missing link today. just curious what everyone else is running. :roll:

[Rexinre]

Missing link will help you out.

The wire that comes with the kit is a diode, and doesn’t eliminate the signal completely. The missing link eliminates it. There is a lot of technical mombo jumbo involved and one day I will write it all out and post it up.

[Honda4VW]

wow, for the price I would think the edelbrock kit would come with a missing link. I would want my map sensor to provide a correct signal to my ecu

[PRcivicHB]

Cant you just use check valves? $10 < $50

[Sonny7730]

yeah you can, that's a kind of a ghetto rig, but supposedly it works.

[gaowee]

valve check work but like sonny said its ghetto..also they tend to crack because of the engine heat and if it should while your boosted might lead to some problem.. i have a missing link and i neva had a problem with my 98ex-T

[ghettoturbo]

so the edelbrock kit just uses what for fuel management, an fmu?

[Rexinre]

It uses a hack similar to the APEXi, called LINK Engine Mgmt. Check out how it works here... http://d-series.org/viewtopic.php?t=5308

[TurboEF9]

Missing link will help you out.

The wire that comes with the kit is a diode, and doesn’t eliminate the signal completely. The missing link eliminates it. There is a lot of technical mombo jumbo involved and one day I will write it all out and post it up.

Technical mumbo jumbo? Heheh..

Let me explain it "laymen's terms". Missing Link is just a fancy check valve. It's a peice of hardware that connects between your MAP Sensor, and your throttle body, and has a diaphram that bleeds off all positive manifold pressure. Therefore, your ECU will not ever think you're "in boost", only vacuum. Check-valves do the same thing, only they are cheaply made (as they were never designed for this type of use) and break.

Both of these methods normally provide fuel with an FMU to give a linear increase of fuel pressure as boost increases, therefore, overflowing your injectors and providing the fuel needed for the increased air pressure.

..so on and so forth..

[Rexinre]

Here is what I meant by “technical mumbo jumbo”: 8)

The atmospheric pressure is to be considered at 14.7 lbs at sea level or 1 bar. Your map sensor (Manifold Absolute Pressure) reads this same atmospheric pressure. Your car, under natural power, is a Vacuum and usually it runs less then the atmospheric pressure creating negative atmospheric pressure or (>14.7lbs per sq in.). :shock:

When you boost a car you are adding to the atmospheric pressure, obviously! So when you are getting “7 lbs of boost” you are really at 21.7lbs with the atmosphere. Mercury, the element used to read pressure, reads atmospheric pressure with the pressure of the manifold. With this at 7 lbs of boost you actually have about 2 bars (depending upon elevation). Thus making a stock Honda MAP sensor is no good with boost, either needing a 3 bar map sensor or the check valve i.e. missing link. :D

If I lost you, or I am wrong let me know. :)

For those of you who already know this sorry to bore you! :(

Some additional information can be found here! http://www.sjmautotechnik.com/10vgauge.html

[TurboEF9]

Not to down play what you're talking about.. but even though your information about what is refered to as "absolute pressure" vs "atmosphereic pressure" is correct, it is not an issue here.

Honda's MAP sensors measure in atmosphereic pressure, therefore, 7psi, is 7psi, not registered at 21.7psi.

Your stock Honda MAP sensors converts this atmosphereic pressure reading into a voltage reading by the use of a diaphram. The incremental scale of the diaphram dictates what your maximum atmosphereic pressure reading will be.

For example, a stock OBD0/1/2 MAP sensor will measure voltage from 0-5v. The useable voltage scale is 0 to about 4.9v because of the design of the diaphram. The resistance of this diaphram dictates the amount of vacuum, or boost pressure needed to "move" it an increment. OBD0 will register voltages from about 28inHg, to about 9.5psi. OBD1 from 28inHG to about 10.5psi (atmosphereic pressure). Honda compatible GM 3bar MAP Sensors use the same 0-5v scale, except the resolution is less. This means that the increments are further apart, therefore enabling a larger range int he same space. Thus allowing the sensor is give a value for higher boost settings.. up to about 28psi.

The only reason we run into issues running positive manifold pressure in our Hondas is because Honda did not create fuel and ignition tables tuned for boost. There were no production force inducted Hondas. Therefore, there is a bounds check in the ECU, that if the voltage gets higher than about 3.1v, a CEL will pop, and the ECU will drop the vehicle into limp mode, because it thinks there is a problem. ..3.1v is about 2psi atmosphereic.

Now the reason one would use check valves or a missing link is to bleed off (into open air.. basically, an intentional "boost leak") boost so that the MAP sensor's diaphram never increments voltage up to the 3.1v threshold, thus, never causing a CEL.

So, clarify just a bit, yes, you can use stock Honda MAP sensors in conjuction with boost projects up to about 10psi (Ye,s you can physically run more, but then you get into the resolution of your fuel and ignition maps, and MAP scalars outside the tunable area of the MAP.. blah blah blah, we can get into that if anyone doesn't understand, or woul dlike more information).

Depending on your engine management setup, you may or may not need check-valves/missing link.

[Rexinre]

Cool, There is some great information on this thread!

[Bizzar]

That sounds about dead on. I've been running a JRSC with the 8psi pulley and I DO see 8psi up to about 5k rpm. Up over that rpm it starts to create a tad more boost and the guage will read on the edge of 10psi. Wether or not its really boosting 10psi is naysay but it is definatly boosting more than 8 psi. No hack, no missing link, nothing just an FMU and stock injectors. Due to stock injectors I do have to retard my timing a little or else kabloey!!

[Sonny7730]

speaking of injectors and fmu, if you're running an fmu and missing link at, let's say 7 psi, what changes would you have to make to keep the stock injectors. obviously new spark plugs, but what other changes would you have to make sure it doesn't blow up?

[Rexinre]

at 7 psi nothing else. More the 8 you need to change the fuel pump.
The injectors you shouldn't have to change until like 18 or so lbs of boost. The other fuel rail will support the fuel needs.
Keep in mind you will need the tuning computer at that point. You will need to mess with your timing/fuel settings...

[TurboEF9]

Ouch.. 240cc injectors at 18psi? :(

Personally, with an FMU, I wouldn't run more than the alotted 6-7psi on stock injectors (and that is even pushing it a bit).

If you compare flow rates with generic air flow rates of the compressor maps of your turbo, you'll see that 240cc injectors are not going to flow the fuel to compensate for the cfm being created.

[Rexinre]

He has the edelbrock kit which has 2nd fuel rail and 4 injectors. So yes 18 lbs is good if he chooses to do so. I got the same kit so that’s how I know, but I don't go over 15lbs because of the turbo flow maps.

[TurboEF9]

Aaaaaah.. Well that would make sense then. 8 injectors @ 240cc flow the same as 4 480cc injectors.. :D

Now it all makes sense.. was getting nervous for him there a second ago.

[Rexinre]

Lol, man you know your stuff, serously and its good to have you here!

[TurboEF9]

Hahaha... Well, I know engine theory, tuning and such.. I don't know about pre-fab kits. We'll all come to the right answer in the end. :D

[Sonny7730]

thanks for the help, but for my question i'm not going to be running the edelbrock. i'm going to be running a homemade with a t3. so could i still keep the stock injectors, or should i look to upgrade, cause i don't want to do overkill.

[Rexinre]

O, Ummm I thought you just got the edelbrock kit! Sorry I got you mixed up with someone else, I just looked at the advatar. Yes you need to upgrade you injectors.

[Sonny7730]

alright, cool, thanks :) haha sorry bout the mix-up. I feel bad jackin' the thread, so back to the edelbrock and missing link!

[Bizzar]

18psi on stock injectors are you nuts lol j/k. I'm at 10 using the stock injectors but also mind you, using the high flow high volume Walbro pump and choking the hell out of the lines with a Cartech FMU. Idle psi is 45ish and WOT is cranked up to 85psi!!! Yes I am 100% positive this is all the stock injectors can handle and under the gun. They are definatly at 100% duty cycle. I know this because I have had one hang open on a few occasions hehe. Just keep a small hammer on hands so you can run out and give it a tap to "unstick" it. Sooner or later they will burn up but I hope to change in some 340's before I found out what happens when theres NO fuel at 10psi runnin full bore under boost. KABOOOOM!!!!

[civicstyle]

Just wonted to say thanks for all the help.....I got my missing link in and took that stupid diode wire out and my car is running great no cel code yet and going on 4th day now........

[Rexinre]

Great!

[Sonny7730]

congrats. knew it all would work out. :)

[oscarmayer]

18psi on stock injectors are you nuts lol j/k. I'm at 10 using the stock injectors but also mind you, using the high flow high volume Walbro pump and choking the hell out of the lines with a Cartech FMU. Idle psi is 45ish and WOT is cranked up to 85psi!!! Yes I am 100% positive this is all the stock injectors can handle and under the gun. They are definatly at 100% duty cycle. I know this because I have had one hang open on a few occasions hehe. Just keep a small hammer on hands so you can run out and give it a tap to "unstick" it. Sooner or later they will burn up but I hope to change in some 340's before I found out what happens when theres NO fuel at 10psi runnin full bore under boost. KABOOOOM!!!!

you should be running prelude 310cc injectors minium at 10psi. your asking for a blown motor on stocker. they cannot handle 10psi. they can';t flow enough no mater what pump and tuning you try.