1JZ water temp climbs 10 degrees within seconds of hitting boost

[1JZ-Rolla]

Strange things seem to be happening with my water temp under full boost... normally I wouldn't notice because the factory instrument temp gauge is so slow to react, but now that I have a Microtech dash unit, I can see the water temp climb from 92 degrees to 104 degrees in a matter of seconds after hitting full boost on the road.

At first I thought it must be the wiring to the WT sensor pulling tight & reading higher resistance or something, then remembered that it reads COLDER with high resistance, not higher, so now I have no idea what is going on!

Is it possible that water temp could climb that quickly, then immediately drop back to 92 degrees when I back off?

[The Real Roadrunner]

its normal for a 5-10degree temp rise but most ppl wont notice as the factory guages are fairly slow.

where else is 250-300odd KWs worth of heat going to go? has to go somewhere and its generally into the block (which is then cooled by coolant), oil or out the exhaust.

maybe try a lower temp thermostat if your worried about flogging the car for long periods but other than that its pretty normal.

cheers
linden

[1JZ-Rolla]

Cool (or hot, which ever way you want to look at it!) thanks Linden

I understand there's a shiteload of combustion temp to be absorbed, I guess it just surprised me that it built so quickly in the coolant temp.

I have a suspicion that my long researched voltage drop when on boost may actually be that the alternator is not keeping up with the electrical demand. Didn't seem feasable before, but now that I know the thermo fan is switching on under boost (since it sees 100 degrees +) it could be just enough to push the alt past its capacity.

Most 1J owners who are sensible enough to leave the motor where it came from (JZZ30 etc) wouldn't have the same issues since they have a mechanical cooling fan right?

Might see if I can put a current clamp meter on the alternator output while on the dyno to see just how much it is trying to match. Between two EFI pumps (VL turbo and 044), 16" Spal fan, 6 bosch coils, 6 injectors etc etc i'd imagine the electrical demand is getting pretty high.

[chris davey]

I have the same issue with a 1j, microtech. I have rewired my ground on the water temp 3 times and it still basically maxes out at 124deg as soon as I boot it. It doesn't matter as there are no modifications to fuel or timing when it gets that high (only air temp) I just gave up on it. My Voltage also drops to 11.8 or so when booting it IIRC. no thermo fan though, just 044 pump, stock coils and injectors and a whole heap of other electrical shit though I guess. No where near as much as a soarer/chaser though!

[1JZ-Rolla]

Thanks Chris, glad to hear its not just mine, i'll get back to not worrying about the water temp now

I'd still like to work out WTF is going on for the voltage to drop under load though.