4JG2T tuning/ high EGTs questions.

[Sags13]

I have a 1999 Rodeo (US model) that I swapped a 4JG2T into during summer of 21, as part of the swap I deleted all the EGR stuff, also I replaced the factory turbo with a Subaru VF48 turbo. I'd read that the larger turbo would allow turning up the fuel a bit for more power, while still keeping EGTs cool enough, plus the original turbo was shot anyway. The EGT probe is in the adapter plate in between the turbo and the exhaust manifold, so basically right as it enters the turbine. Engine has the factory top mounted intercooler, with a good sized hood scoop and the factory rubber baffle sealing it to the scoop. Factory belt drive cooling fan had to be removed to get the engine to fit, installed a slim electric cooling fan on the stock Rodeo V6 radiator. It rarely kicks on and coolant temps seem good.

Engine is running great, and I've put a lot of miles on it, but there is a couple things that bother me.

1) High EGTs. I'm seeing 850°F (454°C) just cruising at 65mph flat and level no headwind. Climbing a hill at full or near full throttle I've seen EGT higher than 1400°F (760°C) before getting scared and backing off. So the first question I have is if this is accurate, or should I relocate the probe to a different spot. (I could put it where the EGR pipe used to go.) If it is accurate, how can I bring the EGT down? So far the only tuning I've messed with is the fuel metering, I turned it up till I would get black soot when pulling hard, then backed it off till it just stopped. It is probably 3/4 turn more fuel then the factory setting. I've never messed with the timing, wondering if that could help.

2) Boost pressure. I've read the factory boost was set around 11psi. The wastegate on the VF48 I put on is supposedly set at 14.5psi, however no matter the temperature or conditions I've never been able to get more than 9psi with it. It pulls nicely up to 9 though before running out of puff, I wish it had a little more. I also wonder if a little more boost would help with my high EGT issue too. I see what looks like some kind of blowoff valve on the intake manifold and I'm wondering if that is opening before the wastegate even starts to modulate.

This is not a common engine here in the states, so any help or tuning tips from you all would be greatly appreciated. Thanks.

[geeves]

Check timing and wind the fuel down a little. Are your boost and egt guages accurate? How far is the egt probe into the center of the exhaust flow? Those figures sound high compared to others quoted here but one mechanic that might also post has quoted figures far higher. He has got his probe right in the center of the gas flow closer to the engine. Took a while to work out but the combustion gas is a lot hotter in the center than near anything solid

[Roadrunner]

So did you resolve the problem? That valve on the intake manifold bleeds off excessive pressure in the intake manifold. I'm guessing that the spring in it would weaken over time allowing some boost to escape. I took mine apart and put some washers under the spring to keep it closed. EGT temps at 60 mph in my 4jg2 is 390 C from the factory, but I wound up the fuel and boost and gave the engine more injection advance, so now I see 290 C. at 60 mph. Full throttle sees egt's at well over 700 C but I turned the fuel down a tad recently and now top out at 700 ish. The factory ihi turbo is safe to 950 C according to the ihi website, but you would want to have good quality oil in the engine at such temps. The low sulphur diesel that is available these days is lacking in lubricity so can make the injector pump advance piston stick (along with gum build up) which would affect cruise egt's, making them higher. I now throw in 250 to 500 mills of engine oil into the fuel tank when I fill up to help alleviate this sticking problem.