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What happens if there is NO speedo input signal to LH2.4?

BDKR said:
I'd really love to know what that is because from where I'm standing, 2.4 never had any functionality that would require know what it's speed is. For what I know, cruise control is handled by a seperate computer. Anti-lock functionality is controlled elsewhere, and that uses different sensors anyways. And 2.4 never had any traction control.

So I'm having a hard time believing that 2.4 needs a speedo signal.

But if I'm wrong, please correct me. I've been wrong around here plenty of times before.



Uhhhh.... I think it uses the RPM sensor and TPS for that job. Looking at my AFR gauge, the engine always resumed in jecting fuel when the RPM dropped below a certain point. Go put it in Nuetral on the freeway and see what your wideband says.
Click to expand...

ABS is run off of three sensors. One on each front tire and the speedo sensor from the rear. ABS is activated during braking when it sees that any of these three sensors are not all reading the same speed.
(a bit wrong on the position of the ABS unit)
And I forget where I read it from (been looking for it) but the speedo signal is used in the fuel cut/decc. function. If I remember correctly it only does the fuel cut above a certain speed.
89363783





Oh and here is the diagram for the OP

91396997


What the hell, those aren't the originally picks I posted, freakin AllData
 
Last edited:
What kind of a car are you installing LH2.4 into?

A couple of thread discuss the conversion:

http://forums.turbobricks.com/showthread.php?t=230687

You can swap in the rearend and speedometer to get the signal to the ECU. The ECU needs a 12V square wave, so if you're doing something that you cant' just swap in the parts, you can build a circuit (somebody used the build inside the speedometer), and use the stock sensor mounted to read a pulse off the driveshaft:

SpeedSignal2.jpg


DSCN1711.jpg


http://forums.turbobricks.com/showthread.php?t=191751&highlight=driveshaft

http://turbobricks.com/forums/showthread.php?t=132582
 
Hi

The LH2.4 uses the speed for several things

when to ligth up the shift up arrow in the cluster
how to attack idle motor strategies (manouvering the idle motor)
When to switch between various 5x5 maps for lambda response
when to go into closed loop before engine is above temperature setpoint.

normally it goes into short term fueltrim (closed loop 1) as soon as the car starts moving

So if it is missing the LH will be bitching about it :roll:

YS
Jaybee
 
I did not read the thread but I can say that we do not have an idle motor or a speed signal in our racecar(facebook.com/generalleif) and it doesn't care one bit. If we had an idle motor, it would make the rpm hang after higher rpm. No problems without the idle motor in the system.
 
With all the information I have just read in this thread perhaps somebody can help me. Certain Takasago speedometer failures are well known. Is it possible that a car, 91 745t, with a malfunctioning or totally inoperable speedometer with lh2.4 would have drive-ability issues? It seems like what I have been reading says that if my speedo gos up to 47 mph when I turn on the ignition and stays there as long as I am driving it must be giving lh2.4 system erroneous info. and affecting the cars' performance and mileage. I've been stumped by these problems for some times for some time. This problem has existed for several years. COULD IT BE????
 
klr142 said:
I did not read the thread but I can say that we do not have an idle motor or a speed signal in our racecar(facebook.com/generalleif) and it doesn't care one bit. If we had an idle motor, it would make the rpm hang after higher rpm. No problems without the idle motor in the system.
Click to expand...

Just wondering how you set the idle? I think I'm going to go this route on my LH swap project
 
You can use an LH2.2 style throttle body, or just do what we did and how everyone sets the base idle with 2.4. There's a little screw that moves the throttle plate, just like on a carb, adjust that to where the idle speed is where you want it. The car will idle lower whenever it's cold or there's a lot of load on the engine(e-fan, etc.).
 
Final report; sucess

Well we have used the car for the summer without a speedo input to LH 2.4 with the following status.

Intially we left the idle control valve installed and yes after long runs it did idle high at approximatley 1500 until power was cycled then normal.

Removed idle control valve and set Idle as per "klr 142" suggestion, everything worked well.

Also it is perceived that after decel (no fuel cut off ocurrs; based upon AFR gauge) and then quickly accelerating; performace (spool up) was better than a unaltered car with fuel cut off.

Thanks for everyones help.
 
I wish I had seen this months ago! Now I feel more obligated to get my speedometer working. I figured that the signal was screwing with my idle because it revs high when I put it in park, but I was unaware of the other problems it causes.
 
Well ****, I'm glad I stumbled onto this thread. My speedo wires were a bit bare on the diff so the needle would bounce so I ripped it out an now I deal with the high idle and other **** I was unaware of. Looks like I'm going to the junkyard to grab another speedo sensor pigtail
 
after a heavy rain, my speedo bounces around for a few minutes when I start off. Will this mess around with lh2.4?

Cheers,
 
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