Understanding boost.

[Lino]

I have an XT Forester without a boost gauge, anyway it seems to have more power with a certain amount of fuel, or gas pedal position, not at full throttle.
Is this just my imagination, why would you want a boost gauge, to know the sweet spot?

 

[nipper]

The boost gauge tells you how much air is being forced into the engine. The higher the number, the more boost, the lower the fuel milage. If it has a Vacume section the higher the vacume the better the gass mileage.

https://www.jumptronix.com/2g_go_faster/Stages/details/BoostGauge.htm

Ignore the part of them selling you a better gauge

 

[Rally]

The amount of fuel will generally have no really noticeable effect per se. However, on a hot day the fuel gets hot, and with a low fuel load it heats up more quickly and performance suffers. Boost is dependant on revs, throttle position and load. You need enough of all 3 to get boost. There is a limit, based on the size of the turbo, the ECU, wastegate and revs. The turbo on the XT is small for this engine size, so you would expect it to be better at low revs and running out of boost higher in the rev range.

Boost gauges are handy for ensuring the turbo is operating correctly. When an alarm installer earthed out the wires blowing my boost controller, I could pinpoint the problem by seeing how much boost I was or was not getting.

 

[nipper]

A small turbo allows for faster spin up and less lag. It is all a tradeoff. Fuel temp really is not that much of an issue. Modern fuels systems has the fuel constantly circulating so it stays within a acceptable temp range.consistant temp range

 

[Lino]

I have been reading so much about boost and turbos, now I'm wandering when my turbo will go out, I guess they all give out, it's just a matter of when.
Hopefully it will not be too hard to change, I do all my own work on my cars.
Thanks for the replies.

 

[Rally]

Left to their own devices, they should last a fair while. I hate changing turbos- I think I'd rather go to the dentist- almost! You will need some good 14mm flank drive 6pt sockets, a ball joint type uni joint, some long extensions and a good ratchet for underneath. Plus I use a super long 14mm ring spanner for the ones up top. You do the job with it cold, with liberal use of WD40. The hard part is putting it back on, the trick being to get the oil return hose on. If you do it often, you're right. But if like me you rarely do it, you forget the little tricks after a while. Oh, did I mention removing and re-installing the heat shields is also a pain! Depending on the sort of driving you do, you could go up 2 or 3 sizes in turbo- but then you'd have to get bigger fuel pump, injectors and definitely a re-tune. If you are happy with what you have, remember the automotive KISS principal. Keep It Standard Stupid!

 

[stealth]

I reckon it might be quicker to pull the motor, as a turbo is easy when not in the engine bay

 

[lefty]

the standard TD04L in the XT has a reputatiuon of being bulletproof. your engine will probably go before the turbo will

 

[El_Freddo]

the standard TD04L in the XT has a reputatiuon of being bulletproof. your engine will probably go before the turbo will

Agreed, I wouldn't be worried about the termination date of your turbo! If you treat it right - let it warm up before a good flogging and a cool down afterwards before you shut down it should be all good.

As for a boost gauge - most ricers have them for the ricer factor, I bet they don't know what's going on. A boost gauge - as far as I know without having a turbo engine - shows you when exactly you're on boost. After some time you will learn when you come on boost with different throttle positions and loadings. It is also a great way to find out if you're getting the correct amount of boost as per specs.

Cheers

Bennie

 

[Rally]

Agreed. The 2.5 turbo engine unfortunately has a reputation to not responding well to modifications and hard use. The big issues being plasticine strength pistons and rods. Oil pickups have also proven to be subject to fatigue, cracking and leading to loss of oil pressure and engine failure. None of these were issues on the 2.0 litre engines but in our little world of offroading it is all less of an issue as most XT owners look for better offroading options- like those with non turbos.

It was only last week I helped out a mate on the south coast who has an MY08 WRX (same engine as XT) fitted with twin scroll turbo, exhaust and TMIC upgrade running 17 pound boost and a mild tune. Nothing radical, but it would appear that he cracked a ring land, had massive blow by and ran out of oil in less than 5000km's and effectively blowing the engine. I had seen the car drive just weeks before and there was no visible smoke. We will know for sure once the engine is pulled down, but in the re-build forged pistons, heavy duty rods and 13mm head studs will be used.

An interesting exercise as I had to borrow a another mates VE SS ute and car trailer from Parramatta, meet my mate south of Wollongong, drive to Nowra to collect his car and get back to his place (just that bit took 3 hours due to holiday traffic) and then back to the north west of Sydney to drop off the car/trailer and then drive home- all up a 10 hour exercise!

the standard TD04L in the XT has a reputatiuon of being bulletproof. your engine will probably go before the turbo will

 

[Athdeb]

Mightycarmods does a turbo upgrade on the forester [ame="https://www.youtube.com/watch?v=A2Po7fMbO_A"]Turbo Upgrade - YouTube[/ame]
followed by a tune [ame="https://www.youtube.com/watch?v=HA___-ukpXI&feature=context-shows&list=SL"]Custom Dyno Tune - YouTube[/ame]