ect sensor taking out timing

347lxvert · Aug 6, 2006

i thought i read a post on here that said the ect sensor takes timing out or something, i have a 94 cobra with performer heads, mac longtubes, off road h pipe, and flowmaster catback, i went to the track last night and i could floor it off the line and pop the clutch and it would almost kill it, the fastest i could get the car to run was in the 14s on a 1000' track, i even got someone else to drive it and his stock 93 convertible went faster than my car with the bolt ons it has, any ideas, i have new wires, plugs, cleaned the maf, i dont know what else it could be, the check engine light is not on when it does this

Synned · Aug 6, 2006

My ACT was killing my car's power, but only when it was warm out. Try using ~40k ohms of resistance with a resistor instead of the act.

HISSIN50 · Aug 6, 2006

You can ohm out the ECT and see what it reads (it's a thermistor, so voltage and resistance both follow the same trend). I'd compare this to your aftermarket temp gauge to see if the reading are close.

The ECT can be out of calibration but not out of absolute spec, so no code is spit. E.g., your ECT might be telling the puter that your coolant is at 245* when you're really at 200*.

Good luck.

95strokerPSU · Aug 6, 2006

http://www.usnaaaa.com/pingisgone.pdf

347lxvert · Aug 6, 2006

it was about 95 degrees last night, i noticed when it is cooler outside that sometimes it doesnt feel like it is bogging down, that is why i thought it might be a temperature sensor

final5-0 · Aug 6, 2006

Yes, higher temps can cause the pcm to pull spark.

Cobra & GT are not like kind of animals however.

Cobra has less adders & subtractors (is that a word ) than the GT.

Grady

SVTCobra306 · Aug 7, 2006

Even more true when all your timing tables are disabled except your base... >

The ect sensor will cause the computer to pull timing when the coolant reaches 200 degrees. You'll feel the difference too....

However if you run a 180 T-stat and the fan on all the time, you'll never break 200 degrees unless you have a problem or are running the car hard ( or live in Arizona).

HISSIN50 · Aug 7, 2006

SVTCobra306 said:
The ect sensor will cause the computer to pull timing when the coolant reaches 200 degrees. You'll feel the difference too....

That's about 30* cooler than I expected the spec to be.

So they designed the timing to get pulled in everyday operation? At that temp, the OEM t-stat wouldnt hardly be open, and neither fan speed be operational (unless AC was on). That just seems strange.

Don 95Vert · Aug 7, 2006

Actually, a T4M0 PCM will start pulling timing at an ECT temp of 210* and it pulls 4* at WOT. It progressively pulls more all the way up to 8.8* at 240* The ACT starts pulling at 150* air temps, it pulls 1.2* and then pulls progessively more up to 2.4* at 210*.

It's NOT a good idea to bypass this with restsors, etc, mainly because they are there to save your motor from detonation.

HISSIN50 · Aug 7, 2006

Don 95Vert said:
Actually, a T4M0 PCM will start pulling timing at an ECT temp of 210* and it pulls 4* at WOT. It progressively pulls more all the way up to 8.8* at 240* The ACT starts pulling at 150* air temps, it pulls 1.2* and then pulls progessively more up to 2.4* at 210*.

It's NOT a good idea to bypass this with restsors, etc, mainly because they are there to save your motor from detonation.

Don, as always, thanks for the great insight.

I'm shocked at those temp thresholds (they're low).

As the puter pulls timing, do you know if it adds fuel (for a cooling and safety effect)?

Don 95Vert · Aug 8, 2006

As far as fuel goes, the ECT only adds fuel at 0* and colder, obvioulsy for REALLY cold starts. The ACT on the other hand really richens things up starting at 126* it adds 22% more fuel and by 210* it adds about 30% more fuel. This is at WOT. We usually make the ACT fuel go away in a tune and use less spark for safety with modified values.

Synned · Aug 8, 2006

Don 95Vert said:
Actually, a T4M0 PCM will start pulling timing at an ECT temp of 210* and it pulls 4* at WOT. It progressively pulls more all the way up to 8.8* at 240* The ACT starts pulling at 150* air temps, it pulls 1.2* and then pulls progessively more up to 2.4* at 210*.

It's NOT a good idea to bypass this with restsors, etc, mainly because they are there to save your motor from detonation.

Does the ACT/ECT sensor also change the fuel tables?

My car was having a horrible problem when it was hot out, hesitation and just pure slowness. I use a resistor instead of the ACT and now the problem is completely gone.

Another question- if the car pings, thats different from detonation, right?
Pinging leads to detination though? Pinging isn't *that* bad for the motor, its the detonation that is, right?

Synned · Aug 8, 2006

Don 95Vert said:
As far as fuel goes, the ECT only adds fuel at 0* and colder, obvioulsy for REALLY cold starts. The ACT on the other hand really richens things up starting at 126* it adds 22% more fuel and by 210* it adds about 30% more fuel. This is at WOT. We usually make the ACT fuel go away in a tune and use less spark for safety with modified values.

This is exactly what was happening with my car, im guessing my fuel mileage greatly increased as well. Is there any reason that with a new act the computer should be doing this around 90*? I decided it was the stock tune, but that doesn't make sense.
The car was acting like a dog as soon as it warmed up outside.

HISSIN50 · Aug 8, 2006

More great info from Don.

I find this counterintuitive. I also had symptoms of running like crap when it was about 105*F out (motor was at 190* and the IAT was ohming out nearly the same inside the chrome CAI, which was hot as all get out). The car was slow (real soft with light and mid throttle input) and would ping. I thought perhaps the puter was noting a less dense intake charge (with high IAT temps) and pulling fuel to remain stioch.

I also farted around with a resistor (to simulate 60* Intake charge temps) and it seemed to help. I was thinking that the CAI was heatsoaked and reporting a higher intake air temp than was accurate.
Now with so much fuel being added (the timing being pulled seems almost inconsequential, speaking for the IAT), why do things get so soft and why is there pinging with the IAT connected to the puter? Are we seeing symptoms we shouldn't, or is/are there other ancillary items which contribute to the softness? I wasn't sure if I inferred correctly Don - do the fuel enrichment changes occur at less that WOT? If not, that kinda is congruent with what I've seen (softness with light throttle). I think that last sentence is the most important one to me, if you cant interpret that pile of crap I typed above.

Thank you for any insight - I know it would help out several of us (Joe, Justin and myself, for three).

badstang123 · Aug 8, 2006

I can't say I am near as knowledgable as others posting in this thread, but I have seen a benefit from replacing ACT with a 47K resistor. During typical driving the benefits have been minimal (Noticable though). If it's over 90* and I have the A/C on though, it's night and day. With the resistor it runs much stronger and has less pinging. I've only been running it for a short time though, so I need to give it some more time before I can really make a good judgement on it's benefit.
- Justin

SVTCobra306 · Aug 10, 2006

HISSIN50 said:
That's about 30* cooler than I expected the spec to be.

So they designed the timing to get pulled in everyday operation? At that temp, the OEM t-stat wouldnt hardly be open, and neither fan speed be operational (unless AC was on). That just seems strange.

I was off, it's 210. Either way, daily operation on mine was 215 in Louisiana summertime with the stock rad and fan settings, and I would notice the difference in power as it warmed up.

95Vert · Aug 10, 2006

Don, so the solution for this problem is a custom tune? How about an a9l swap, would that help?

These resistors you guys speak of. Where can they be purchased? Any pics of where they go installed.
Thanks

Don 95Vert · Aug 10, 2006

Well, this parameter could be one of the reasons some people with A9L swaps feel the cars are quicker. The ACT pulls 6* but at a really hot 240* - but an A9L car has the ACT in the #5 runner too. The ECT starts pulling at 236* - 2*, then it goes up to 4* at 246*. The A9L also has a part throttle adder that pulls spark at high loads starting at 210*. The fuel multiplier on an A9L doesn't really do anything except when it's really cold, like Minnesota cold...

But the computer pulling spark and fuel isn't a bad thing - the temp limits of a T4M0 are probably a good thing because if it's that hot, it's not great for the motor to be beating on it.

You can do away with or raise all the T4M0 stuff with a chip - we do it all the time for blower and turbo cars.

Don

95Vert · Aug 11, 2006

You were my first choice when it came for a chip, but since I have 30# with matching MAF, I SOL with you guys. I'm going to do the swap soon and get some more power out of it. And if anyone is in they're right mind, they won't step on their car when it's running that HOT. Should I relocate my ect to the #5 runner as well for better readings? Or if I get rid of the heater core lines just screw it in to the front of the lower intake? What's best?

Thanks Don.

ect sensor taking out timing

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