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  • 2.5 vs. 2.3

    Hi everyone,

    I am once again requesting for your help. As you all know i am currently rebuilding my s14 engine and need some more help to make a decision.
    I have the choice of keeping the block as a 2.3 or increasing it to 2.5 which will require a new crankshaft as well.
    The cams used will be 284/276. Carbon airbox, Miller MAF with WAR chip.....

    I am having trouble deciding what to do with the block 2.3 or 2.5
    Any help would be great.

    Thanks

    Shahan.

  • #2
    Is cost a consideration? Do you know the cost of the 2.5 crank?
    Peter
    ____________________________________

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    • #3
      That's a personal decision only you can make. As for me, I am perfectly happy with the power I have achieved with my modded 2.3 so I chose not to do the 2.5 conversion. One reason was the cost of the 87mm evo crank which has just about doubled over the last 10 years. Also for a true 2.5, we would have to go to a max bore of 95mm+. I didn't want to do that either. Then there is the tuning, etc.

      88 M3 - LACHSSILBER/M TECH
      89 M3 - ALPINEWEISS II/SCHWARZ
      85 323I S52 - ALPINEWEISS/SCHWARZ
      91 M TECHNIC TURBO - MACAOBLAU/M TECH


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      • #4
        the more you spend $ the more power you can achieve how fast do you want or need to go i personally think a good 2.3 is better for any street or autoX use a 2.5 is for the track junkies or motors that need to be totally rebuiltMike

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        • #5
          Last week i started thinking about rebuilding my S14, money in my situation is not a lot, but with time i can go both ways.

          What hp output can i expect if i only do a overhead, schrick cam´s, bigger valves and port/polish intake?

          I´ve got CF airbox.

          If going to 2.5 can i expect good torque gains, and what kind of hp can i get?

          My car will be street driving and sometimes trackday´s, but even on street will in a fast pace as i will send it to Portugal and will be my car when i go back on vacations?

          But my bigger problem will be doing porting and assembly of the engine as where i live (Saskatoon) there is no one i can trust for that job, any suggestion´s?
          Thx

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          • #6
            a well specced 2.3 will outperfom a 2.5 build if same amount of money is used for both builds IMHO. (talking of a sensible budget, not no money no object builds)
            The money the 2.5 parts alone will cost is better spend on getting the right parts for your 2.3

            I would not build a 2.5 for a mostly daily driven car, the few CC's more will not give you the torque gains you may think.


            Goodbye M3, you served me well.

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            • #7
              Thank you for your answers.
              I am looking at the pricing of both options. If the price difference is not too big, I might just go for the 2.5. But if The price is too big then i will stick with the 2.3 as you said.

              How much price difference do you expect with a top 2.3 vs. a top 2.5.
              What are the parts that will need to be different? Crank, pistons, rods, bored block. am i missing anything?

              Regards,

              Shahan.
              Last edited by shahano; 03-03-2013, 11:39 PM.

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              • #8
                That all depends on what you consider to be a top 2.3 and 2.5. If we are talking true top, i.e DTM standard, probably within 5% of total cost, total cost being $50k.

                On something sensible/streetable it is the cost of pistons, crank and machining the block.

                Pistons: Up to $800 for good quality forged pistons. (I'll sell you a set of BNIB stock pistons if you like)
                Crank: $2300 for a 2.5 crank from VAC
                Machining: $200 probably

                Rods, Valvetrain, head, flywheel ect are the same.

                So something like $3300.
                Sport Evo No.47

                My Sport Evo Restoration

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                • #9
                  I think this is really a pretty simple question. All else being equal, the 2.5 is better in every way except cost, so you really just have to ask yourself how much you want to spend...

                  But I agree with the advice that if funds are limited, I would rather spend the money on a nice balanced build on a 2.3, than buy a 2.5 kit and leave everything else about the engine completely stock.

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                  • #10
                    In the late 90's/early 2000's, I have noticed that nearly everyone simply purchased these 2.5 kits (custom pistons, evo crank, new chip and 2.5L gasket) from Turner or similar shop, slapped in the components and left the top end completely untouched. Then figured they should have at least 240-250HP like the sport evo because they are now 2.5L. It just doesn't work like that. You can gain some HP from the stroke/compression but real HP is gained in the top end so to me it makes more sense to open up everything on top and lighten components for high RPM before stroking it. The sport evo engine had bigger valves, hotter cams, bigger throttles/headers, etc. It all worked as a package to produce 238HP. Back in the day, stroking was one of the first things people did, now because of price I feel it should be the last. There's so many other things you can do to the 2.3 that yields big HP without rebuilding the bottom end.

                    With that said, I think if you want to run high duration/lift cams that necessitate changing pistons anyway and you can get a good deal on an 87mm crank (they come with bearing shells), perhaps sell your old crank to recover some funds and you don't mind taking your block close to max bore (for more of a true 2.5)...it may just be worth it to you at around $1000 for the crank. It's really up to you.

                    88 M3 - LACHSSILBER/M TECH
                    89 M3 - ALPINEWEISS II/SCHWARZ
                    85 323I S52 - ALPINEWEISS/SCHWARZ
                    91 M TECHNIC TURBO - MACAOBLAU/M TECH


                    Comment


                    • #11
                      Originally posted by stevesingo View Post
                      Pistons: Up to $800 for good quality forged pistons. (I'll sell you a set of BNIB stock pistons if you like)
                      Crank: $2300 for a 2.5 crank from VAC
                      Machining: $200 probably

                      Rods, Valvetrain, head, flywheel ect are the same.

                      So something like $3300.
                      Just to add, if you are going reasonably high spec on your 2.3 and go for forged pistons, you can scratch $800 form that. That still leaves $2500 to play with.

                      $2500 would get you some good head work with uprated springs to go with your 284/276, CF Airbox and Miller.
                      Sport Evo No.47

                      My Sport Evo Restoration

                      Comment


                      • #12
                        Originally posted by Reelizmpro View Post
                        In the late 90's/early 2000's, I have noticed that nearly everyone simply purchased these 2.5 kits (custom pistons, evo crank, new chip and 2.5L gasket) from Turner or similar shop, slapped in the components and left the top end completely untouched. Then figured they should have at least 240-250HP like the sport evo because they are now 2.5L. It just doesn't work like that. You can gain some HP from the stroke/compression but real HP is gained in the top end so to me it makes more sense to open up everything on top and lighten components for high RPM before stroking it. The sport evo engine had bigger valves, hotter cams, bigger throttles/headers, etc. It all worked as a package to produce 238HP. Back in the day, stroking was one of the first things people did, now because of price I feel it should be the last. There's so many other things you can do to the 2.3 that yields big HP without rebuilding the bottom end.

                        With that said, I think if you want to run high duration/lift cams that necessitate changing pistons anyway and you can get a good deal on an 87mm crank (they come with bearing shells), perhaps sell your old crank to recover some funds and you don't mind taking your block close to max bore (for more of a true 2.5)...it may just be worth it to you at around $1000 for the crank. It's really up to you.
                        See my question regarding sleeving a S14 block. Agreed Thinking I have a great boat anchor.
                        Who knows where I'll be, changes from day to Continent.

                        Comment


                        • #13
                          Agree with everything in this thread. I'd put cams(schrick 284/276) and headwork into a 2.3; alphaN and airbox before going 2.5 or larger. With prices of the evo 95mm block lately, 2.5 crank, that was grounds for me to look at a little more and build a 2.7. Main cost being the extra $k for the crank. Didn't like the idea of boring the 2.3 block out for 2.5 pistons. Just not enough meat and pretty sure i'd be running it hot. Heard stories of punched out 2.3s that are short lived.

                          Another case is a M10 bock punched to 92mm; it's now my center piece of my sun room as a coffee table.
                          Photos

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                          • #14
                            Hi all,

                            Seems like keeping the 2.3 might just be the better option... Still not sure and waiting the quotes from VAC motorsports. They are providing me with a whole buildsheet including heads, cams, header, piston, rods, gaskets, oil pan, race oil pump, water pump, chains, CF airbox, Miller MAF and warship. I guess i could call this a complete rebuild.
                            For the 2.5, we need to add a crankshaft and a couple of other parts to the above.
                            I was going to go for the 2.5, but after hearing all of you, i might just stick with a 2.3. If however i can get a better engine for $3300(probably less after discount), i might just take the bullet since I am only doing it once.

                            My worry is about machining the block, but after having asked around, seems like I got one of the best shops to do the job (lebanon is a small country so we can easily find out a persons work).

                            Let me know what you guys think.

                            Regards,

                            Shahan

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                            • #15
                              I am thinking going the same way, let me know what vac tells you about parts price

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