TrevorS

iTrader: (1)

Picked up a thermocouple temp meter to make some TB and neck measurements on my Eclipse, but thought I'd try it out first on my xB. After taking air and surface measurements, I checked some OBDII values. I'm having trouble believing the MAF temp reading -- very inconsistent with the reasonably accurate ambient thermocouple reading. In any case, here's what I got with a fully warmed idle and open hood (~670rpm OBDII).

ambient air (six feet distant at inlet height) -- 79F
just inside air inlet (immediately behind TRD vent) -- 82F
insulation covered intake pipe -- 84F
top center OE air box -- 96F
OBDII IAT (MAF air) -- 117F (??)
insulation covered TB elbow -- 94F
TB (coolant warming bypassed) -- 108F
OBDII ETC (coolant, varies with fan) -- 194F-202F

just inside air inlet (engine shut down, hood closed) -- 89F

TrevorS

iTrader: (1)

Thinking I need to measure the underside of the air box nearest the header and see if I can finagle an air box interior measurement. The TB measurement is interesting too -- I'm guessing it's due to heat radiated from the block with the car just sitting at idle.

TrevorS

iTrader: (1)

Took more measurements and today's warmer. The OBDII IAT is again pretty high, but not as badly as it was yesterday. The thermocouple measured box air temp was made by inserting the probe under the corner of the air bypass flap which necessarily allows some 100F engine bay air to leak into the box slightly raising the measured temp. But even so, the temp difference from thermocouple to IAT is 17F. Guess I'm not too impressed with reported MAF temp accuracy.

ambient air (six feet distant at inlet height) -- 81F
just inside air inlet (immediately behind TRD vent) -- 87F
insulation covered intake pipe -- 93F
directly under box air bypass flap -- 100F
probe through edge of flap (causes leakage) -- 89F
OBDII IAT (MAF air) -- 106F (??)
TB (coolant warming bypassed) -- 105F
OBDII ETC (coolant, varies with fan) -- 194F-202F

just inside air inlet (engine off, hood closed) -- 92F

PS. As a consistency check, I also measured the temp of the concrete a few feet ahead of the car with an IR meter, it gave 82F -- pretty consistent with the 81F thermocouple ambient reading. A few more IR measurements.

top center OE air box -- 96F
TB (not a great angle) -- 108F
corner of the block nearest the TB -- 130F
header flange (flat black) -- 260F
wrapped #2 header pipe -- 380F

PPS. All readings were taken in the shade. All OBDII readings were taken with the engine running.

TrevorS

iTrader: (1)

Well, can't do anything about the MAF IAT readings, but I can try lowering the TB temp, don't much care for it heating the intake air !

Roller_Toaster

iTrader: (1)

I'd be interested to see if doing a coolant bypass mod would help the temps much.

And when I say interested....I mean..."nudge nudge...wink wink.....do it so I can see"

TrevorS

iTrader: (1)

It's easy enough to do. I suggest a couple middle duty spring clamps from Lowe's or Home Depot to pinch off the two coolant lines, otherwise you'll lose coolant. Then you'll just need something to join them -- can reuse the provided clamps, but remember to block off the two TB nipples.

Roller_Toaster

iTrader: (1)

Doh, I meant to say " do it so I can see the results". I had already planned on doing it, but wanted to see if there was truly any benefit.

TrevorS

iTrader: (1)

It's not going to blow your socks off, but if you're trying to cool down the ingested air (eg, installed a CAI), then seems to me every little bit helps and that coolant is near 200F and coursing through the TB -- aluminum is very good at conducting heat !

I tried to do the same thing on my '90 Eclipse, but turned out its cold idle behavior is governed via a coolant temp controlled air valve in the TB. Bypass the TB coolant and bye bye proper idle behavior -- very disappointing ! I just today finished an alternative mod that included installing heat dissipation fins at the TB neck.



Weird, huh? Hey, what can I say, that's me )!