Blue temp sender query

[Kevin Bacon 5]

Would pulling the plug on it make the engine over or under fuel?

 

I can't remember! Or does anyone know the resistance of the sender when the coolant is cold?

 

Got myself into a situation and need to temporarily make the engine run rich! I've heard of putting a 3000ohm resistor across the plug but I can't get one today....other option is to use a second sender and just plug it in hanging in the engine bay so it never sees the coolant.

 

Basically I gas flowed my throttle last night but it means idle and part throttle now see a lot more air than usual and the engine hates it, coughing and misfiring all the time.....ooops! I've had to order a new throttle at huge expense. That'll teach me for buggering about :roll:

[andy 0]

As engine temperature rises, the resistance goes down, couldn't comment on values though.

[andy 0]

Thinking about it, if putting a 3k resistor in is the same as putting a spare sensor in, unattached to the car then you can assume the cold coolant value is 3k ohms. If, according to what I said the resistance falls with an increase in temperature then pulling the plug will be more like higher resistance ie still cold so would tend to make the engine overfuel. However, I reckon the ecu will see it as open circuit and assume the engine's running at its default 'safe' value of 80 degrees C.

[Chris VR6nos 0]

Now are we sure that the blue sender will change fueling or is that the domain of the maf and lambda?

The blue one is the ECU temp sensor and changing the res on it will adjust the idle speed, i've done it but not sure if the mixture was actually altered!

 

 

Chris

[Supercharged 2]

I've got a spare 'good' BTS Kev, I think you need it to start the engine from cold but unplugging it assumes a fixed value of 90c.

[andy 0]

Coolant Temp signals are used as a correction factor for ignition timing, injection timing and idle speed stab'.. according to my info, what do they mean by injection timing, surely thats fuel pulse width, ie fueling. What else compensates for cold starting if its not that?

[Kevin Bacon 5]

Cheers lads. I've plugged in a spare sender and left it dangling. I'll see if it helps.

 

I just need it to hold out until tomorrow morning for my journey to and from work as the replacement throttle arrives in the AM.

 

The tailpipe is white!! I wasn't expecting grinding out the step in the throttle opening to have such a big impact on air flow, but you live and learn!

 

As Chris says on occasion, I seriously need a DTA or KMS standalone if I keep buggering about with the engine like this!!

 

Think I'll just replace the throttle and leave well alone :-)

[dr_mat 0]

You could just unplug one of the myriad sensors and force the ECU into limp-home?

[Kevin Bacon 5]

Yeah, could try that, thought about the lambda - can't do that as the MAF less remap relies on it.

 

Pull the throttle sensor - can't, no MAF and engine relies on it for idling

 

Cam sensor - might work, but can't get to it, no tools in the car!

 

Intake temp sender - doesn't have anything like enough trimming scope to help and pulling it assumes a 20 deg ambient, which is warmer than it is now!

 

Erm, yeah...stuffed really!

 

Moral of the story...... don't feck about with something that works!

[lottysvdub 0]

don't feck about with something that works!

but if you hadnt then we wouldnt have known not to try it , so really we should be saying thank you for the sacrifice of your throttle body in the quest for more power resulting in the the knowledge that it didnt work .

Sorry mate im not taking the p**s , hope you sort it soon its the type of thing that i would try and it always goes wrong :D

[Kevin Bacon 5]

LOL, well I always tend to learn the hard and expensive way!

 

All is not lost, I'm due a remap to run a MAP sensor anyway, so I'll use the hogged out throttle for that :-) It pulls so much better low down with the bored throttle, makes a huge difference - until it heats up and the fuelling goes off :-)

 

To get her running smoothly, I had to put the standard chip back in!

[Kevin Bacon 5]

Even though it's not working at the moment, I was rather pleased with my throttle porting :-)

 

The red line was where the step was, so I removed a heck of a lot of metal!

 

[dr_mat 0]

That's a heck of a lot of metal. Gotta wonder if they didn't leave it there for a reason .. ;)

[Kevin Bacon 5]

Yep, the point of the step is to act like a crimp on a garden hose, i.e. speed up the gas flow for torque. It's largely because of that that OBD2 VRs feel perkier off the line. Once the throttle is a 3rd open, then the air flow through the throttle plate slows down again and the engine can then get on with making power.

 

Now that's all fine in normally aspirated applications, but when you add a big air pump to the engine, the need for the ramp is negated and it's more of a hinderance than a help ;-)

[dr_mat 0]

Interesting. Tempting to try out a highline TB, actually, sounds useful. Mind you, I need my remap working properly for the Schrick first ..

[Kevin Bacon 5]

You also need an OBD2 ECU and harness to run the Highline throttle too :-)