In your opinion: do 2.5T's just "let go"?

[Robbks]

if your economy is that bad, your o2 sensors are stuffed

[Monkey]

if your economy is that bad, your o2 sensors are stuffed

I don't know about o2 sensors, but I think 13-15L is normal consumption for the 3L.
And can you can't really compare "city" driving in Tasmania with Sydney

[GTbee]

if your economy is that bad, your o2 sensors are stuffed

Sensors were changed many months ago. No change in fuel consumption.

[Shaheenis]

As much as I love my GTB, I was surprised at the lack of off the line torque that I expected from the 2.5ltr. My other liberty (Gen1) i have owned and been modding for 10yrs and I always deliberated about getting a bigger engine like a 2.5 and eventually had a custom 2.2ltr built (not stroker) built. Open deck but ARP studs and forged pistons and rods. With a VF28 turbo and slush box (upped line pressures and high stall) has heaps more torque. It would out perform my GTB throughout the entire rev range at 12psi (expected as stock) versus ~17psi in the GTB. With that said, the GTB has only a retune, no actual mods yet. I just expected more shunt off the line but maybe it is the manual versus auto.

After everything I have read I would personally be cautious pushing above 220atw on the EJ255 as kiahatsiu mentioned earlier. Although it sounds like plenty are doing it and getting away with it, you are just walking a thinner line the higher you go. It is a choice and a risk decided by the individual. The WIN for me is to have a car that has oodles of power between 0-120 with an aggressive torque curve and good daily drive-ability. Once again from what I have read you should be able to achieve this safely in an EJ255 running sub 18psi so probably under 200atw and all without your 2.5T letting go .

[bigBADbenny]

Fascinating post from Maxwell Power about compression ratios, bore vs stroke, rod length and EJ's:

http://forums.nasioc.com/forums/showpos ... stcount=25

[Shaheenis]

I will have to read this Benny.

I also would like to take back what I said about my GTB being sluggish off the line above. I uploaded a new tune from Matt last night and I don't know what he has done but it feels a lot stronger and smoother and boost appears to have gone down, not up (do some more logging tonight). Launch Control in S# with a VF46 yep she moves .

In the past I have blown 3 x EJ20/22 motors (well two myself and one by the tuner) and it always came down to detonation. Two ring lands on No4 and one cracked cylinder wall on No4 (this one had forged pistons). Supporting mods are obviously a factor but the tune should cater for any lacking mods so ultimately tune is key. I guess even with the perfect tune if you are squeezing big boost into the engine and something goes wrong (blows a hose causing a lean out as an example) then the consequences are likely much more devastating. They way I would think about this is with the open-deck EJ20 and EJ22 variants, 220atw and 18psi was about all you would want to run safely. Not sure how the EJ255 cylinder walls fair in comparison but assuming they are same/similar and given the larger size (.5ltr) you might expect 25% increased flow but the Lib EJ255 variants rev lower which would offset the power potential so back to ~230ish (very crude calculation).

[bigBADbenny]

The crux of the matter in the Maxwell Power post linked to, is that building a 2.3 de-stroked ej255 decreases the rod angle in turn decreasing the chance for detonation if properly tuned, as the piston spends more time at TDC, effectively meaning a bigger window with more effective resolution to add timing.

The comment that lead to the post was about building a low compression EJ engine, apparently pointless as EJ's make power from timing especially as regards off boost conditions...

(PLEASE correct me if I'm wrong here)