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Thermostat Question


hpfmnst

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  • Member For: 9y 6m 19d

Hi everyone!

Bought 2008 fg xr6t not long ago with upgraded injectors, hi-flow fuel pump, hi-flow catalytic converter and bigger intercooler. Now, after driving car for a while, I realised it drinks 98 octane fuel like there's no tomorrow. I would get little over 300 km out of a tank in urban/hwy drive. I changed spark plugs with denso iridium ones and it stayed the same. Car has done 110k and old spark plugs were black, clearly indicating that car was running rich all the time. Then, my attention turned to coolant temperature. The coolant gauge was sitting about 1/4 on temperature scale most of the times and I started suspecting it is thermostat. Finally today decided to replace it. Bought new hi-flow xr6t thermostat from SCA and it opens at 91°C. When I pulled one that was installed there it was 71°C. That explains why car was running rich all the time, since it couldn't get out of warm up loop. Exhaust was all black and I think if I continued to drive like that I could've done damage to cat converter. Temperature was too low. Now, with new thermostat, temperature needle sits just under half on the scale. But now fans are running all the time once car reaches operating temperature of 91°C ! Question. How do I adjust when fans cut in? I understand that tune might have been done, but car was using way too much fuel and obviously dumping unburnt fuel down the exhaust. Is it possible to adjust fans manually at all, or do I need to find a tuning place to adjust fans for standard thermostat. Appreciate your help with this as I realised reading through different topics on this forum that there are some super knowledgeable people here.

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  • Member For: 9y 6m 19d

Even with modifications, I think you're better of keeping standard operating temperature, since lot of modern oil additives start working at 90° and engine has been engineered from ground up to work at this temperature. Personally don't think it is worth extra few kilowatts if engine burns more fuel than necessary and also risking damage to catalytic converter.

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  • Member For: 12y 4m 3d
  • Gender: Male
  • Location: Perth

Pretty sure if tuned correctly using an 82deg thermostat the consumption is ok.

Well mine is at 398rwkw on 98.

Oil will be hotter than coolant temperature so moot point with oil additives.

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  • Member For: 18y 6m 1d
  • Gender: Male
  • Location: @ my laptop

hotter thermostats do produce better fuel economy no matter who or how it is tuned, colder help keep under bonnet temps down and useful when good intercoolers are not used.

Modern oils do need a minimum temp for the additives to start to work and give the protection you pay for with the oil, running too low coolant temp can keep the oil temp down as well

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  • Member For: 12y 4m 3d
  • Gender: Male
  • Location: Perth

hotter thermostats do produce better fuel economy no matter who or how it is tuned, colder help keep under bonnet temps down and useful when good intercoolers are not used.

Modern oils do need a minimum temp for the additives to start to work and give the protection you pay for with the oil, running too low coolant temp can keep the oil temp down as well

Very generic statements.

Sure hope the minimum oil temp for additives to work includes cold starts.

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