2.5L Rebuild question....

[Stan]

>>>By the way 0-60 in 5.36s. I am happy to live with it.. <<<

I have other mods too. But I think you could get to or below 6 seconds for 0-60 without too much trouble. I got down to 6.24 seconds with a chip and other minor stuff while still using the AFM. But the below 4000 action still sucked and throttle response was sluggish compared to the present setup I'm using.

The main thing is to get the AFM out of the intake air path. It's that metal box thing at the back of the air filter box. It has a spring loaded door inside that is small compared to other parts of the flow path. And it gets smaller at certain RPMs even when floored since the door closes. At part throttle an S14 needs a fair amount of throttle opening to create enough vacuum behind the AFM so that the door opens sufficiently.

There are several ways to ditch the AFM such as using a mass air sensor like contemporary BMWs, several alpha-n approaches, hybrids, full stand alone engine management, etc.

Stan

[K.C.]

Good information Stan. Sound like you already been thru all this stuff. So exactly what you done to your S14 and where you have it done? And how much $$$$.
Thanks. Kin

[Steve88M3]

Just so I'm clear on this, Stan your car is a 2.3L correct?

[HANDBLT]

Originally posted by K.C.
Good information Stan. Sound like you already been thru all this stuff. So exactly what you done to your S14 and where you have it done? And how much $$$$.
Thanks. Kin

Shade tree trial and error young apprentice......:jedi:


Do a search with AFM and Stan here and on DTM and you'll create days worth of reading.

T

[John]

K.C. if you want to know about Maxx Alpha N, Martin and I
are selling/supporting it. I have it on my engine.

I didnt mention the Alpha N to you because, this already
assumes you already now what you are going to build.
As it sounds, you dont know what kind of motor you want
to build or as someone else suggested perhaps you want to
do a swap. I like "top down" approaches. Decide first what
the general goal is and then go from there. This is already
getting into specifics of a certain type of S14 buildup.

It has been a while since Ive driven stock M3. I know the
AN (Alpha N) increases torque everywhere, but I think
Im used to it. My engine is also built to favor top end
5000-8000 rpm performance, bottom end was never a consideration.
It breathes and makes
more power above 7000 where your normal S14 is already
falling off or starting to, even the cam'd ones
with 284/276 run into the same breathing problem without
head work.

Anyway, the usual progression is to add as much breathing
you can, that is all top end 5000+ rpm stuff. You can
work on the head, special pistons, cam, CF airbox, etc.
the alpha N is just part of all that.

OR

you can go the 2.6l or 2.7l route. Jake, are you not
planning something like this? The bottom end will be all
custom and cost about the same as a very well built 2.5l.
Not many people have experience with this. There are 2 tuners
in Germany that do it, they build 2.7l.

John

[HANDBLT]

Originally posted by John
K.C. if you want to know about Maxx Alpha N, Martin and I
are selling/supporting it. I have it on my engine.

I didnt mention the Alpha N to you because, this already
assumes you already now what you are going to build.
As it sounds, you dont know what kind of motor you want
to build or as someone else suggested perhaps you want to
do a swap. I like "top down" approaches. Decide first what
the general goal is and then go from there. This is already
getting into specifics of a certain type of S14 buildup.

It has been a while since Ive driven stock M3. I know the
AN (Alpha N) increases torque everywhere, but I think
Im used to it. My engine is also built to favor top end
5000-8000 rpm performance, bottom end was never a consideration.
It breathes and makes
more power above 7000 where your normal S14 is already
falling off or starting to, even the cam'd ones
with 284/276 run into the same breathing problem without
head work.

Anyway, the usual progression is to add as much breathing
you can, that is all top end 5000+ rpm stuff. You can
work on the head, special pistons, cam, CF airbox, etc.
the alpha N is just part of all that.

OR

you can go the 2.6l or 2.7l route. Jake, are you not
planning something like this? The bottom end will be all
custom and cost about the same as a very well built 2.5l.
Not many people have experience with this. There are 2 tuners
in Germany that do it, they build 2.7l.

John

Does the standard top end build like I have (284/276, 48MM TB's, alpha n, light head prting to match 48's....etc) match well with the 2.6/7l bottom end? Can the 2.6/7l be achived with the US2.3l block? I really have not found much info on the larger bottom ends besides the 2.5l. This is the route I have wanted to take. Throw out some general numbers on the crank/rods/pistons $$$$$$$$$$$$$'s..........

T

[ADA///M]

im gonna go out on a limb here and say anything larger than 2.5L is probably not what anyone here wants for a street car...

Im not saying the larger displacement engines wont last long...But I highly doubt its worth it for a street engine for all the custom $$$$$...im sure most of these engines are RACE ONLY...with lots of maintenance needed

ADA///M

[Mad Mike]

Originally posted by ADA///M
im gonna go out on a limb here and say anything larger than 2.5L is probably not what anyone here wants for a street car...

Im not saying the larger displacement engines wont last long...But I highly doubt its worth it for a street engine for all the custom $$$$$...im sure most of these engines are RACE ONLY...with lots of maintenance needed

ADA///M

I got 5.9 Litres and 340 lbs torque. :D

Mad Mike

[HANDBLT]

Originally posted by Mad Mike
I got 5.9 Litres and 340 lbs torque. :D

Mad Mike

OK ENOUGH WITH THE JEEP REFERENCES, this IS an S-14 discussion.

T

[Mad Mike]

Originally posted by HANDBLT
OK ENOUGH WITH THE JEEP REFERENCES, this IS an S-14 discussion.

T

Take a deep breath and hold it.

Mad Mike

[John]

the bottom end parts are about 6000 euro (crank, rods, pistons).
no special engine block is used.

you can make a street 2.7l if its done right.
these are not race motors, although there are race
versions of these that make a lot of power and dont
have to last (see dolate 2.8l with 400+ hp)

I almost decided to build one. Maybe I still will next
year

John

[Jake]

you can go the 2.6l or 2.7l route. Jake, are you not planning something like this?

There's a lot of work to do but yes, eventually I'd like to have a 2.6 hanging off the engine stand. :D

I'll be in a position financially to resume putting this project together in about a month or two but my current location in the UK isn't all that set in stone for the next year. I'm trying to get an assignment to Korea so I'm holding off until I know for sure where I'm going to be. Most likely I'll just pack everything up, put it in storage for a year while I go away to Korea and then return and resume the project. Not like I've ever really been in a big hurry anyway. :p

Adam,

This 2.6 will be just as maintenance free as any mild 2.5. With all concerns taken into account, there is no reason something larger than 2.5 has to be a highly strung and temperamental race motor.

As far as necessary additional costs, the crank is the biggest one. Some use custom rods for their 2.5's anyway so I don't really count that as an additional cost. All 2.5's will obviously require new pistons so I don't count them either. Other than this though, everything else will be standard high spec 2.5 stuff. Unusual maybe, but far from extreme in my opinion.

What makes an engine "maintenance needy"? The simple answer is RPM. An engine designed to spin exceptional RPM will need a few things that definitely impact service life on there own. High lift, long duration cams is one of them. Using a modest redline with a respective cam choice will probably make the biggest difference in terms of service life. This is a basic rule that applies to all engines irrespective of their displacement.

Take care,
Jake Larsen

[EVOIIIM3]

Originally posted by Jake
There's a lot of work to do but yes, eventually I'd like to have a 2.6 hanging off the engine stand. :D

I'll be in a position financially to resume putting this project together in about a month or two but my current location in the UK isn't all that set in stone for the next year. I'm trying to get an assignment to Korea so I'm holding off until I know for sure where I'm going to be. Most likely I'll just pack everything up, put it in storage for a year while I go away to Korea and then return and resume the project. Not like I've ever really been in a big hurry anyway. :p

Adam,

This 2.6 will be just as maintenance free as any mild 2.5. With all concerns taken into account, there is no reason something larger than 2.5 has to be a highly strung and temperamental race motor.

As far as necessary additional costs, the crank is the biggest one. Some use custom rods for their 2.5's anyway so I don't really count that as an additional cost. All 2.5's will obviously require new pistons so I don't count them either. Other than this though, everything else will be standard high spec 2.5 stuff. Unusual maybe, but far from extreme in my opinion.

What makes an engine "maintenance needy"? The simple answer is RPM. An engine designed to spin exceptional RPM will need a few things that definitely impact service life on there own. High lift, long duration cams is one of them. Using a modest redline with a respective cam choice will probably make the biggest difference in terms of service life. This is a basic rule that applies to all engines irrespective of their displacement.

Take care,
Jake Larsen

TMS had some beautiful ACS 2.6l cranks a while back, only about $1200!

[SeattleE30///M3]

Originally posted by Jake
There's a lot of work to do but yes, eventually I'd like to have a 2.6 hanging off the engine stand. :D

I'll be in a position financially to resume putting this project together in about a month or two but my current location in the UK isn't all that set in stone for the next year. I'm trying to get an assignment to Korea so I'm holding off until I know for sure where I'm going to be. Most likely I'll just pack everything up, put it in storage for a year while I go away to Korea and then return and resume the project. Not like I've ever really been in a big hurry anyway. :p

Adam,

This 2.6 will be just as maintenance free as any mild 2.5. With all concerns taken into account, there is no reason something larger than 2.5 has to be a highly strung and temperamental race motor.

As far as necessary additional costs, the crank is the biggest one. Some use custom rods for their 2.5's anyway so I don't really count that as an additional cost. All 2.5's will obviously require new pistons so I don't count them either. Other than this though, everything else will be standard high spec 2.5 stuff. Unusual maybe, but far from extreme in my opinion.

What makes an engine "maintenance needy"? The simple answer is RPM. An engine designed to spin exceptional RPM will need a few things that definitely impact service life on there own. High lift, long duration cams is one of them. Using a modest redline with a respective cam choice will probably make the biggest difference in terms of service life. This is a basic rule that applies to all engines irrespective of their displacement.

Take care,
Jake Larsen

Jake, this is an interesting subject. For some reason, I have always understood that on 4 cylinder engines, when displacement exceeds 2.5L the vibrational characteristics of the engine increases dramatically due to the inability of 4 cylinder engines to cope with 2nd or is that 3rd order harmonics, reducing overall engine life. Especially b/c 4 cylinders are prone to vibration compared to I-6, V-8 etc... Is this just a fallacy or is there some truth to this.

[Jake]

SeattleE30///M3,

I think you can offset some of these problems to an extent. Obviously stroke and bore has nothing to do with frequency as it's still a 4cyl. It's still going to "beat" the same rhythm. However the magnitude of these vibrations will change. How magnitude is affected with respect to changes in rotational mass is something I'm incapable of calculating at my level of knowledge, so I have to rationalize.

And so this is how I’ve come to rationalize it. If you increase rotational mass/inertia due to a longer stroke crank, you affect magnitude and inherent harmonics within the assembly in a negative way, this is understood. So what if you decrease rotational mass while increasing stroke? Inertia compounds at a greater rate with the larger diameter crank throw, so the ultimate RPM for a given rotational mass will surely be reduced. But if you start off with less mass I think you can extend the safe zone far enough to maintain a sound bottom end within a respectable RPM limit.

For instance, take the factory E3 bottom end. How does this assembly mass compare to a stock 2.3? It weighs more, correct? Longer stroke crank and bigger pistons…. It must. The larger rotating assembly has greater inertia and thus a corresponding change to magnitude at any given RPM (or frequency). But both of these factory assemblies are capable of spinning much higher, even in stock form.

Now let’s build a bottom end with a 90mm crank. The crank for sure will be custom and lightweight. With typical custom rods and pistons I think you'll find you can easily build this bottom end to have less mass than the stock E3 assembly; probably even less than the factory 2.0L assembly. I don’t know how much this levels the field but I think we’re on the right track.

Assuming that one maintains a modest redline, say under 8200, I predict that you could build a 2.6L with an acceptable service life. The change in rotational mass across the range from the factory 2.0, 2.3 and 2.5 liter designs compared to a custom light weight 2.6 spinning at modest RPM seems inconsequential to me.

Anybody will tell you ultimate RPM will be reduced, but I have no intentions to build an RPM monster. I want to increase torque beyond the typical high spec 2.5 street engines. And although it will use light weight components, it’s fairly safe to say it will be much more robust that any factory production variation.

HTH,
Jake Larsen