2.2 or 2.5 turbo?

[t-1 LeBaron 5sp]

I found a 1991 2.5 t-1. Is it better to build a 2.2 or a 2.5? And why? thanks

[MarshallOne]

Do a search. This question has been asked a hundred times. What it boils down to is...and this is just opinion mixed with experience...high horsepower = 2.2. 2.5s are excellent for runaround town. Smooth and torquey but they tend to blow all to heck under high boost and high horsepower. 2.2s is what you need. How many turbo 2s, 3s, and 4s, have you seen in the 2.5 litre size from the factory? None. Maybe the factory knew something. Excuse me while I don my fireproof underwear.

[SUPERVAN]

The 2.5 was a motor designed to tug around grandmas K-car and someone at Chrysler put a turbo and MPI on it. A TII was intended to haul ***.

I personally love the 2.5 engine. I got one out of a minivan for my Daytona. They come cross drilled, with heavyweight rods. Those two reasons were the biggest reasons I felt great about getting one. A side note was that the Pacifica is a fully loaded very heavy car, that can definately benefit from the extra torque of the 2.5. Toss in the really low geared A523 I'm putting into it, and it might just accellerate like an L body.

Make a desicion based on comparing bore and stroke on both engines
2.2 Bore =3.44 Stroke =3.62

2.5 Bore =3.44 Stroke = 4.09

both engines have more stroke than bore. Just like a diesel. It's refered to as "under square"

Generally speaking stroke builds torque and bore builds horse power

4.09 is more stroke than a 454 chevy!!! But 3.44 is smaller than the 265 chevy. You wind up the smallest bore and the largest stroke.

long strokes also generate more centrifical force and are somewhat RPM limited by that. ALL 2.5 had ballance shafts.

I think the 2.2 is just right and the 2.5 is extreme.

All depends on application. If you don't need to rev it (like if you are gear limited), then a 2.5 is fine.

If you need power to 6300 rpm, then the 2.2 is a better choice.

You can make the 2.5 rev... just more money, custom cam, head work...

[DirectConnection]

Quote:

Originally posted by Praxis All depends on application. If you don't need to rev it (like if you are gear limited), then a 2.5 is fine. If you need power to 6300 rpm, then the 2.2 is a better choice. You can make the 2.5 rev... just more money, custom cam, head work...

Piston speeds on a 2.2 are still very high for high rpm hp.
All of the dyno plots I have seen from people's cars, I have yet to see one 2.2 that makes peak HP anywhere's near 6k. I don't think I've even seen a 16v 2.2 (T-III) make peak HP above 6k for that matter.

I don't believe anything you do to the 2.5 (besides de-stroke) will make the 2.5 rev. IE: revs=hp (*if* there is hardware to support it) I can explain why... but this would take me some time to explain in my words.

There's a wildy modified 2.5 16v that peaks well below 6k on these boards. Makes kick booty power.... but is limited by the long stroke. Torque.... well.... it actually has too much :big grin:

What Praxis is trying to say is this: 2.2 vs 2.5 the 2.5s usually make less peak HP at the expense of generating much more torque. This would give you better response, meaning...you don't have to wing the engine up to 4k to be in it's power curve. Also, the 2.5 should have less lag with larger turbos due to it's displacement.

The funny part... a 2.2 is actually a very torquey motor, just not as apparent as a 2.5.

[Mopar_Nutz]

I don't know as much as some other guys in here posting but I'd say it depends what you want to do with the car?
For low mods in an auto or something I'd say the extra down low of a 2.5 would be nice.
For heavily modded I would assume that the extra torque of a 2.5 would be too much for the street. What good is torque if all it does is spin your tires an extra gear? For heavy mods on a streetcar, I would imagine the 2.2 would give you more than enough torque as well as give you some extra revs.

I've had the same trouble deciding, but when it comes to building the engine for my Daytona, I think I'll probably go 2.2 for the reason I mentioned.

My 2.2 peaks at 4800 rpm, but the power stays flat to 5800 rpm (within 10 hp). That's with stock cam and just mild head work.

I can guarantee with the cam I have coming, and a little more headwork it would peak at 6000 or more. But, I decided on the 2.5 as well

[DirectConnection]

Quote:

Originally posted by Praxis My 2.2 peaks at 4800 rpm, but the power stays flat to 5800 rpm (within 10 hp). That's with stock cam and just mild head work. I can guarantee with the cam I have coming, and a little more headwork it would peak at 6000 or more. But, I decided on the 2.5 as well

Yeah... I am going with a 2.5 because I am too committed to change to anything else right now.
I decided on the 2.5 for a few reasons:

#1) because 2.5 T-I motors were plentiful compared to T-II 2.2 motors. At the time, I had no idea that 2.2 common block cast cranks were so plentiful in Shadows, and no 2.2 OS Mahles on the market. I eventually did go with JEs, though.

#2) I was going with a 5 speed tranny, and I heard good things about the off boost torque and response, so I figured it would make the car easier to launch through easier modulation of the go pedal! My 2.2 VNTs have gobs of torque down low, but nothing at all at 0 psi launches. (until I discovered high rpm under vacuum launches to make up for it)

#3) The fastest cars at the time were running 2.5s (Gus, Gary, FM, etc..)

But it really boils down to what ET, raceweight, boost level, *turbo selection*, tranny, and powerband you are looking for.

[crazymadbastard]

2.5 with a 16v hybrid conversion, that ought to get some air in there at 6000+ rpms with a big turbo.

well with my V8 back ground i still think there is no replacement for displacement..
my daily driver has a 393 cubic inch stroker motor with 3.850 stroke and a 4 inch bore... so whining about to much torque kinda makes me laugh...

2.5's have a HUGE stroke though. which hinders the MAP RPM with out going to custom pieces to hold it together . the good news is your 8V head will never flow enough to get you into the range of impossible RPM for a 2.5..
i mean a head that will flow to 6K on a 2.2 will only support 5,400 RPM on a 2.5 you add 30 cubic inches with out increasing air flow you drop your RPM peak... win win..

for daily driver? you will spool your turbo Quicker with a 2.5. you will have more off boost response. and make more off the line torque..a flatter longer broader HP and torque curve.

for racing? you have more torque, and more exhuast flow which spools your turbo faster and at a lower RPM.
you also have almost 30 more cubic inches.
but you will have traction issues..darnit

your choice..
the only reason i would go for a 2.2 is for autocrossing where you dont want a but load of torque out of the corners.. or you make so much HP that you need a forged crank.. but they arent needed till say.. 400HP?? and.. you still have a crappy 8V head...

my 393ci has a cast crank and is making well over 600HP on the bottle..

[macncheese]

ok, everybody is trying to get technical. passengers, drivers, and opponents alike do not care about technical. they care about getting nailed back in the seat. i will NOT trade my 2.5 for anything less than a forced 350 what's all this talk about 2.5s will only spin the tires? engines aren't responsible for the tires spinning....lack of traction is!!! what about multiple stage boost controllers, better tires, weight distribution, different gearing, NOT FLOORING IT all the time; there are many ways to improve traction, just as there are many ways to make power. lets do a quick test..
all of the td'ers out there who have built, driven, or ridden in a 2.5 turbo and WEREN'T impressed, raise your hand.
(cricket: "chirp chirp, chirp chirp")
thought so.
lol
just my thoughts
tony

heh, hook that 2.5 to an automatic with slipping clutches that won't downshift half the time.. heh.. Eh, when it does downshift it's a hoot.

[Mopar_Nutz]

Quote:

Originally posted by macncheese all of the td'ers out there who have built, driven, or ridden in a 2.5 turbo and WEREN'T impressed, raise your hand. (cricket: "chirp chirp, chirp chirp") thought so. lol just my thoughts tony

My Lancer (2.5) feels like a dog compared to my Daytona (2.2). But thats auto vs 5 speed.
Question is. Is all the extra torque usable on street tires? Or is it just more tiresmoke?