T2 SMEC enough fuel?

[WickedShelby88]

Ive got a 2.5 T1 I will be running at least until I get the plumbing for the SRT4 cooler I have. My main question is how much risk will I run into as far as being too lean with a 89 2.2 T2 calibrated smec with my 2.5. Ive already got the wiring setup for a 4 wire O2 so that should help some, but Ive heard the spark curve is noticeably different from the 2.2 to the 2.5. Could anyone elaborate on this?

[MiniMopar]

Since you already have a SMEC car, you might as well just run the 89 T1 2.5L SMEC. The amount of fuel that the CAT sensor meters is quite minimal. Just turn up the fuel pressure a hair for extra insureance, or run a set of +20s.

The main differences is in the fueling (especially in the midrange) and a bit in the spark curves.

[Dodge Aries K]

Joe, talk to me about getting one. A friend and I are going hunting in Sandwich this friday night.

[TurboJerry]

2.2 T-II spark curves are too aggressive for a 2.5. Better off running a 2.5 T-I comp. Unless you want to find out what detonation does to an engine...... I tried to run 0 deg basic timing, and you could still hear detonation, and it would still take 15 deg out due to knock retard. +20's seem to help, but not enough in my case.........

[WickedShelby88]

Right on guys. Thats what I was afraid of.

[ShelbyZD]

Make sure you get the right Smec. I put a 2.5 AUTO t1 smec in my 89 A555 and I didn't like the way it idled at startup.

Also, just for the record. In stock form I see no reason why a 2.2 T2 ecu couldn't run a 2.5 engine. It's already setup for the bigger T2 injectors, setup for the larger T2 exhaust and has enough fuel to run a 2.2 on 14-15psi with a well opened up exhaust.

I know others have done it successfully but personally my engine was burning too much oil for me to be able to tell.

[MiniMopar]

...but it's not setup to be a 2.5L.

Remember, we don't have MAF sensors. The computer guesstimates air flow by measuring pressure and temperature to calculate density and then using hard-coded tables that have been tuned to estimate how much air the engine will draw on a given stroke for a given set of circumstances. The 2.5L will draw more air, therefore needs more fuel. The 2.2L calibration has no clue that there is more air in the cylinder. The same is true when you port the head/intake/whatever. It increases the volumetric efficiency of the engine, so the calibration needs to be...recalibrated. If our elelctronics used MAF sensors, we wouldn't need to worry about a lot of this. MAF sensors are expensive, though.

Also, the 2.5L has different ingition characteristics due to the longer stroke, so that needs to be compensated for as well.

[TurboJerry]

The fuel is not actually far off, it's the timing of the T-II that got me. But Minimopar is 100% correct. A 2.5 MTX comp would be the best starting point.. The only difference between the MTX/ATX comp's are the idle settings/idle response characteristics.(as far as I can tell)

[turbovanman²]

I tried a 2.2 cal in my van for shits and giggles, I had to turn up the fuel pressure to like 65-70 psi and set the base timing at around 4 deg. I still didn't like the way it ran, still lean under part throttle.

[GLHSKEN]

.

Also, just for the record. In stock form I see no reason why a 2.2 T2 ecu couldn't run a 2.5 engine. It's already setup for the bigger T2 injectors,

Lots wrong there. The injectors are the same size. 33lb/hr... You are running with a crutch if you use a tII ecu for a 2.5L. (note... I am doing this with my convertible... base timing set at 8^ initial and +20's at 55 psi static pressure. (of course my head more than likely flows no where NEAR turbojerry's )

[WickedShelby88]

Yeah guys I already looked at D-cal where there was a comparison for the 2.2 T2 timing vs the 2.5 T1 on a chart. I plan on going with a MP 2.5 cal when I get my smec socketed, but for now I got a 2.5 T1 manual trans smec. I traded my T2 smec for it, but its no loss IMO because I will change the cal so I can still use my air charge sensor as well and instead of running plus 20's for now I will just adjust the fp a little higher. Thanks for the initial info guys as I didnt think of timing.

[turbovanman²]

Thanks for the initial info guys as I didnt think of timing.

[TurboJerry]

I always seem to *massage* cyllinder heads. I guess it's "force of habbit". My Lebaron runs T-II fuel with 2.5 timing and runs pretty good. This *is* a completly stock 2.5. Which I figured is a good way to compare the "real" diff with the 2.2/2.5 battle............