General Forum : 323i vs225e and 325is

e21enthusiast

Posted Sunday, Oct 15th 8:20pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 24

eugene,oregon
hennarot 320is,topasbraun metalic 323

ok so thursday night i called a friend with a 325e to see if he wanted to race my 323i,just a friendly race to see where my car was at ya know. i was thinking i was gonna loose plus i have like no idea how to launch im not used to drag racing. first run i acidently burnt out threw most of first,second run a litlle better take of and almost dead even but i won,last race i took him by atleast 3 cars. last night after we got done cruising i asked a guy with a 325is if hed go out knowing i was gonna have my as handed to me,we took one run and he was gone by like 10 semi truck lengths before i hit second,well not quite that bad. sucked though i was having a sputtering isue too,but i still woulda lost. i was damn surprised he raced my friends golf vr6 and it was prety close,the golf one, but damn i didnt know those 325is's were that fast.

MayanArch

Posted Sunday, Oct 15th 8:37pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1176

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

The last couple of years of the 325is were just as fast as the E30 M3's up to 60mph.....but then the M3's were faster by a second or two up to 100.

The 325is that had the super ETA engines had the same 2.7 engine block of a 325e.........except they had the "is" head........which was really excellent at high RPMS and higher speeds.

The regular 2.5 325i were nice too......but the super eta ones really had the best of both worlds.

That is why they tell you to couple a 2.7 ETA block with an "is" head when doing a stroker.

I personally like the low end rpm growl of the 323i head ........... but then again, I dont race and I dont take the car to near redline rpms.

cnvkellogg

Posted Sunday, Oct 15th 9:16pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 55

Eugene, OR
78 320i

If you want to autocross don't go with the eta block or anything 2.7L. That will put you in the anything 2.5 and over OSPO, including v8's. Thats why Im staying with 325is motor. That is as big as you can go in OSPU. Im faster than e30's because of the e21 being so much lighter. I wont even bother racing a 325e. On the other hand if you want to go to club track days go big... 2.7L eta block with a turbo kit.

redmist

Posted Sunday, Oct 15th 11:35pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 985

NY USA
357i , 325i e30 turbo

BMW never put the head from the "i" on an "e" block. They did on the 1988 Super ETA use the "I" head but only with 4 cam bearings, weak springs and an "E" cam. You would never beat a healthy 170HP stock 325i with a stock healthy 323i. Just won't happen.
The hot setup is a "e" block and a 323i head with a turbo or a Super ETA block and "I" head with a turbo. Good for 240 to 300 and more HP.
I'm doing a rear mount 325e turbo currently as I love low rpm torque of the "e". Using a special chip with a 6000 rpm redline, 22# injectors, beehive springs (65 pound seat pressure) and a RRFPR. Looking for only about 220 but a nice wide flat torque curve.

cnvkellogg

Posted Sunday, Oct 15th 11:45pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 58

Eugene, OR
78 320i

mmmmm....turbo....aaahhh.

I'm still saving.

myersport

Posted Monday, Oct 16th 4:57am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 184

east tennessee
'82 320iS. '91 327iC

Pete-
The 1988 Supereta engine used the 885 head casting as you say, as well as only the outer valve springs instead of the dual springs the 325i used, but you are wrong about the cam journals. The supereta used all 5 journals as the 325i did, and unlike the early 'e' engines with the 200 head casting which used only 3 journals. So the trick is to find a 1988 supereta block, and simply install a 325i cam and the extra 8 inner valve springs and you have an engine that will make 143 hp and 172 lb/ft torque at the wheels (using stock motronic 1.3). Ask me how I know all this.

--Dennis

wharthog

Posted Wednesday, Nov 1st 7:39pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 75

SF Bay,California, USA
1982 323i, , R1150RT

I'm trying to put together a reasonably priced gimmemore motor... Mayan, have you put an ETA block under the 323i head? If so how does that work? Just based on my seat of the pants feel, my stock 323i is torqier at lower RPM's than the 325i's I've driven... but the 325i pulls away once you get up to horsepower range. Has anyone slapped a 2.5 block into our car? Or run a 325i complete motor with the k-jet?

imaradiostar

Posted Wednesday, Nov 1st 9:16pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 925

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

What kind of parts do you have laying around?

The E21 323i head is a huge limiting factor- there are huge gains to be had by going to the E30 323i or 325i heads.

If you have an E30 323i (731 casting) head laying around you can make a cheapy hybrid motor using M50 pistons, 135mm rods and an eta crankshaft. You'll have to knock a mm or so off of the top of the pistons but it's nothing a decent machinist would shy away from. You could use this same bottom end with a 325 head and intake but the squish geometry won't be very good. I have an extra m50 piston set if you want some.

Definately use dual valve springs from a 325i head! If you can get your hands on a larger cam it'll be of huge benefit- my engine floats valves at 6k plus both the added lift and duration would be a help. CIS should be able to handle cams as big as the shrick split duration 284/276 (272?) without any trouble. My E30 323i head on 2.7 bottom engine really isn't a revver at all and the bottom end (while durable enough to take it) wasn't really designed for high rpm and the components are a little heavy. The M50 pistoned engine will rev higher and be happier doing it.

If you can get one cheaply (car-part.com) a 325i engine running megasquirt fuel injection is an excellent and very tunable way to go- plus you can slap a turbo on it when finances allow. Probably the shortest path to success if you don't have a cheap or free machinist to help you build a budget engine.

redmist

Posted Wednesday, Nov 1st 11:51pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 997

NY USA
357i , 325i e30 turbo

I thought the super eta had all the cam journals but the Super ETA cam only used 4? Yes I heard that put the "I" cam on the super ETA head is a straight swap. I would pass though on the dual springs and get the MM behive springs, that's what I did on my "e" head to wind it up to 6K.
Save your cam and better performance at the same time.
Yep I went mega squirt too MS1 V3 with spark control, no AFM, no Motronic. Should be arriving shortly. Got a plug and play setup (already programmed for the "i" turbo motor) including 42lb injectors, wiring harness and MSD.
Still debating on a straight "e" turbo or a super ETA block and "i" head. Leaning toward the "e", Have all the peices for both. Do I want ridiculous turbo HP (390+) in upper RPMS (7000) or strong torque down low and moderate turbo HP (240) at 6000 rpm?

imaradiostar

Posted Thursday, Nov 2nd 12:35am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 926

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

Higher rpm and better pressure ratios are the way to go according the the Swedish turbo guys.

jamie

Bill in MN

Posted Thursday, Nov 2nd 2:52am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 38

Minnesota USA
1988 735, 1986 535 turbo, 1981 Baur 323i

Redmist,whose turbo system are you putting in?

Posted Thursday, Nov 2nd 9:45am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 10

NY, USA
82 528e2i 84 320i/4 80 320i

I recently finished an e to i swap in my '82 528e. I heard the nearest chassis dyno is an hour drive from here so I don't have any numbers for you guys but here is my recipe:

junkyard 325i head, intake manifold, throttle body, fuel pressure regulator
custom made pistons (same shape as 325i but with more compression height)
everything else is stock eta

I compared the stock chips from the 007 and 027 ECUs and a Dinan chip. What I ended up doing was tweaking the 007 chip. The result is here http://www.hyakushiki.net/tj6.bin

It sounds/feels like it's lost a bit of torque under 3500RPM, but high RPM power is great. The torque curve feels "peakier" than on my M10. Also, I got 25mpg (mixed city and highway)

wharthog

Posted Thursday, Nov 2nd 10:21am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 76

SF Bay,California, USA
1982 323i, , R1150RT

Jamie,
Thanks for the info... that was one way I was considering going. If sourcing the ETA bottom end wasn't a problem would u go for the 2.7 with i head or does that change the nature of the beast too much? I can get ahold of the parts easy/cheap I have friends... I would be paying retail for machine work though. Suggestions?

imaradiostar

Posted Thursday, Nov 2nd 4:44pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 929

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

I'm not a big fan of the i head/eta bottom engine. The squish geometry is pretty poor with this combo. It'll certainly have torque but in a light car like an E21 the 325i engine is a better way to go. I have an eta bottom end with a 731 casting (E30 323i) cylinder head and while it's plenty powerful it is definately a torque monster, not a revver. I wish I would have had the money for a bigger cam and valve springs when I built the thing because it would have made a big difference!

The eta bottom/I head combo is used by some of the turbo guys because it results in a lower compression ratio. While this works fine for some guys I don't like the idea (again, squish area) and I think you'd have better results with the complete I engine. If you're really looking for power there are things you can do to increase the power of the 325i engine without having to buy rods or pistons. Low friction coatings, polishing, reducing squish/increase compression ratio, etc.

The only way to make really big power with an M20 is a turbo anyway; the M20b25 responds very well to a correctly built turbo system.

jamie

redmist

Posted Thursday, Nov 2nd 5:25pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 998

NY USA
357i , 325i e30 turbo

An ETA/I is a bad combo but the super eta/I is great the only thing you lose is a little compression ratio but you end up at the perfect place for a turbo motor 8.7 to 1.

I'm doing a rear mount turbo. My own design.
Happy to give details if you want. Email me.

wharthog

Posted Friday, Nov 3rd 12:49pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 77

SF Bay,California, USA
1982 323i, , R1150RT

Thanks remist but at this point I think a turbo is more over the top (knowing me I'll probably get there shortly) and I'm trying to keep a stock or 'period correct' look. Based on what I'm reading here sounds like a complete 325i motor is the way to go... can I run that motor with k-jet (again the period correct thing) or are there going to be ignition/distributor and other issues?

realcrouton

Posted Saturday, Nov 4th 1:29am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 57

Washington, USA
1977 320i, 1981 323i, 1991 325ic, 2000 328i

My plan was to put a 200 head (w/L-jet set up) on to a 2.7 eta bottom end without changing any internals. From this thread it sounds like this might be a little disappointing. Fortunately my brother is a machinist, so that won't be expensive. With that in mind what items should I have my eyes peeled for? 325i head? M50 pistons? Different rods?
I might also note that my dad used to have an automotive machine shop, and we still have all the equipment. Boring bar, seat and guide machine, valve grinder, head surfacer etc... I'm guessing I could build a pretty decent engine, but I want to do it as cheaply as possible.

So the long and the short of it is; machine work is free, what components should I gather seeing as I already have an eta and an L-jet set up?

Thanks!

-Dave

myersport

Posted Saturday, Nov 4th 3:06am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 184

east tennessee
'82 320iS. '91 327iC

Dave-
You won't be disappointed. I had this setup at one time, and I felt it had better throttle response (with k-jet) and better off line torque than my later motronic 2.7i supereta setup with the 885 head. In fact, what little I gained with the later setup I don't feel was worth the time and money, and if I were to do it again I would spend the money on a hot cam, 3-angle valve job, and a mild porting on the 200 head. The extra compression of the early eta setup helps too.
--Dennis

wharthog

Posted Saturday, Nov 4th 2:10pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 78

SF Bay,California, USA
1982 323i, , R1150RT

the 200 head is the stock 323 head right? I know what the 885 is...

BruceH

Posted Saturday, Nov 4th 3:14pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1029

Atlanta, GA USA
81 323 Baur, 85 745

My car has the stock 200 head on a 2.7 bottom. It is OK. Not much happens beyond 4800 rpm but noise.

A 731 head is on the shelf awaiting freshening and porting.

realcrouton

Posted Saturday, Nov 4th 9:44pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 58

Washington, USA
1977 320i, 1981 323i, 1991 325ic, 2000 328i

Bruce,
With the 731 head mated to an eta block w/ stock pistons and rods I can see revs over 4800? Will my L-jet intake bolt up to the 731 head?

Dennis,
With your eta-200 set up did you see the lack of revs over 4800 that Bruce is describing?

Thanks guys.

-Dave

myersport

Posted Sunday, Nov 5th 4:49am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 184

east tennessee
'82 320iS. '91 327iC

Dave-
It's not that the engine won't rev past 4800, it's just not making significant power past 4800. It will rev to 7000 easy, there is just no point. With the eta/200 head setup, there is a noticeable power gain, it is just shifted lower in the rpm range. Shifting at 5000 rpm will yield better overall accelleration than shifting at 7000. For what it's worth, however, my supereta/885 head combo didn't make significant power past 5500 rpm.
--Dennis

BruceH

Posted Sunday, Nov 5th 5:11am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1030

Atlanta, GA USA
81 323 Baur, 85 745

What Dennis said....

imaradiostar

Posted Sunday, Nov 5th 8:40am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 932

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

The eta bottom end and 731 or 200 casting head combo seems to work well with low gearing and a 4 speed or overdrive 5 speed. The wide power range seems to be a good complement to the wider gear ratios and taller rear gearing. I still feel like 1st is too low with this setup though.

If you really wanted a more spirited revver you'd have to go with a head flow and cam duration increase to complement the larger displacement. Various BMW tuners out there could give you suggestions and details on what could be done to improve things.

There's nothing wrong with an eta bottom/731 head engine, it's just I wouldn't want you to compare it to a 325i engine and be disappointed. The 325i engine is going to feel more lively and fast though it may not actually be the case. I've driven my boss's 315/2.5i and my 323i back to back and while they're both pretty quick his has a different feel- more of what you'd expect from a BMW. My car has more of a US V8 kind of feel to it- lots of torque and spinning tires at low rpm but not as much excitement as the revs climb. Sure, it still pulls pretty hard at 5500 but not like it would with a bigger cam.

If all goes to plan I'm going to be slapping a bigger cam in mine soon and I'll be able to report the changes.

jamie

Posted Sunday, Nov 5th 9:02am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 13

NY, USA
82 528e2i 84 320i/4 80 320i

With the 885 head and 325i intake you should be able to get good top end power. Try milling the head for more compression. I'm using the stock cam but my M20 is still pulling at 6000RPM.

wharthog

Posted Monday, Nov 6th 1:22am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 79

SF Bay,California, USA
1982 323i, , R1150RT

from what I'm hearing, it sounds like an 885 head, ETA bottom end, hotter cam, and maybe some headwork is the optimum naturally aspirated setup... I'd like to keep my K-jet with that. Is that foolish.

Bruce, you said you're going to L-jet. What are the advantages of the swap?

BruceH

Posted Monday, Nov 6th 3:10am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1031

Atlanta, GA USA
81 323 Baur, 85 745

I'm not going to L-Jet.

I'll second that with a 4 speed and the eta/200 combo first gear seems short.

The 731 head is going to make a difference over the 200 head right?

Bill in MN

Posted Monday, Nov 6th 3:28am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 41

Minnesota USA
1988 735, 1986 535 turbo, 1981 Baur 323i

Somewhat off topic, but how much power can a 323 chassis handle before things start going wrong?

BruceH

Posted Monday, Nov 6th 3:57am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1032

Atlanta, GA USA
81 323 Baur, 85 745

There were several 345's built. Gotta wonder about the torque.

Marquis_Rex

Posted Monday, Nov 6th 5:12pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 491

UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT

On a naturally aspirated engine ports are all about a compromise of flow against port velocity.
I once heard someone post that if you make a port too large it won't flow as well. In fact this is not true, the larger the port the less the restriction so the better it flows, HOWEVER, flow isn't everything, there's a compromise with velocity. Ford learned this with their massive tuunnel ports in the late sixties and Pontiac learned it the hard way with the RAM AIR engines- where the ports were simply way oversized. Someone probably only used a flow rig which indicated bigger is better.

On a naturally aspirated engine ports are all about a compromise of flow against port velocity.
I once heard someone post that if you make a port too large it won't flow as well. In fact this is not true, the larger the port the less the restriction so the better it flows, HOWEVER, flow isn't everything, there's a compromise with velocity. Ford learned this with their massive tuunnel ports in the late sixties and Pontiac learned it the hard way with the RAM AIR engines- where the ports were simply way oversized. Someone probably only used a flow rig which indicated bigger is better.

So what you want is the highest velocity possible with the highest flow possible. High velocity is important because it keeps the kinetic "ramming" energy of the flow high (KE=1/2 MV squared).
Good gas velocities to aim for on an engine with cast ports in the centre section before the valve shroud/guide protrusion are 88 to 95 m/s. On a fully machined , straight and very good flowing 4 valve port over 100 m/s is possible and sometimes over. The E36 M3 achieves a mean gas velocity of 119 m/s at it’s 7400 rpm peak power speed.

If you use a '200 cylinder head on a 2.7 litre engine at 6000 rpm you’ll already be at 108 m/s, at 6700 rpm you’d have reached 120 m/s! This is way too high for a cast port on a 2 valve type engine- so the ports are WAY too small! By comparison a conventional 2.3 litre 323i at 6000 rpm has a mean gas velocity of around 92 m/s which is ok, may be a bit on the high side if the engine is to be modified. It’s a shame the 200 cyl head doesn’t flow all that well at high valve lifts- so the compromise of this head is too far in the direction of gas velocity. Perhaps it’s the ideal head for the short stroke 320i/6

An E30 885 325i cyl head will achieve about 78m/s at 6000 rpm, 87 m/s at 6700 rpm. Bit on the low side but ripe for modification or capacity increases! Also this is a head that flows very well.
A 2.7 engine with the 885 head is almost like a match made in heaven, with 84m/s at 6000 and 94 m/s at 6700 rpm. My current run around 323i has a set up like this and works very well, while also achieving great fuel economy on K Jetronic.

Because I intend to stretch my M20 capacity by a massive amount and because I’m pretty much redesigning the whole port where it will be totally machined and straight, raised slightly, I intend to aim for gas velocities of close too 100 m/s. I’ve calculated that I’ll need a port diameter of about 39.5 to 40 mm.

realcrouton

Posted Monday, Nov 6th 8:20pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 59

Washington, USA
1977 320i, 1981 323i, 1991 325ic, 2000 328i

Your detailed explanation is really helpful Marquis. You make a very good argument for the 885. Would you also pair this up with a hot cam, or use stock?
Does anyone know which cars/years were shipped to America with the 885 head? I have a feeling I'm going to have to start hitting the bone yards.

Also, as per the transmission discussion, I'm planning to use the 5-speed out of my 84 325e. Is first going to be too low in this transmission?

-Dave

redmist

Posted Monday, Nov 6th 11:26pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 999

NY USA
357i , 325i e30 turbo

Super ETA bottom, not ETA bottom with the "I" head...just to be clear. The key is the super ETA pistons.

(or an ETA with Super ETA pistons; or an "I" engine with Super ETA pistion and ETA crank; or "I" engine with eta crank and take 2mm off the "I" pistons etc etc)

wharthog

Posted Monday, Nov 6th 11:47pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 80

SF Bay,California, USA
1982 323i, , R1150RT

Sorry Bruce I meant to ask Dave why he was going to L-jet.

Marqius- Brilliant dissertation that. Thanks for boiling it down.

My question is the same as Dave's now... hotter cam or stock? Sounds like you can't go wrong with the hotter cam.

And for review, a list of years/models that had the SuperETA bottom end and likewise for the 885 head.

If I recall correctly the '90-'92 325i and 325is had the 885. Were there others?

I'll see you in the boneyards Dave! If you find any extras, let me know.

realcrouton

Posted Monday, Nov 6th 11:50pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 60

Washington, USA
1977 320i, 1981 323i, 1991 325ic, 2000 328i

Thanks Pete, I actually was a little unclear about that. So what is going to be easier to come across, super eta pistons or "I" pistons to be milled down? I'm thinking least expensive of course. Milling the pistons won't cost me anything.

-Dave

myersport

Posted Tuesday, Nov 7th 2:02am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 184

east tennessee
'82 320iS. '91 327iC

wharthog wrote:

My question is the same as Dave's now... hotter cam or stock? Sounds like you can't go wrong with the hotter cam.

Definately a hotter cam. Like I posted earlier, The 885 'i' head on the supereta bottom end starts running out of breath at 5500 rpm. With Marquis several over-the-top-so-much-that-I-get-lost-so-just-accept-the-fact-that-he-knows-alot-more-than-me

dissertations on the 885's flow characteristics, the limiting factor has to be the camshaft. Keep the valve open longer, more air gets in, more power is made. Maybe Marq can back me up on that.
--Dennis

realcrouton

Posted Tuesday, Nov 7th 2:41am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 61

Washington, USA
1977 320i, 1981 323i, 1991 325ic, 2000 328i

Ok, so the '90-'92 325i and 325is had the 885... I'll be looking hard. I'll try to find two Wharthog, if you find a coulpe first let me know. Anyone have an idea what the max price should be for an 885?
I went L-jet because my mechanic (I call him the Peurto Rican Bandit

) suggested it to me. He likes the ease in tweeking the distributor while having a stable electronic fuel injection system. I beleive it came from an e30 323i, I bought it from a guy on this site. While we're on this topic, will the L-jet intake bolt up to the 885 head?

-Dave

MayanArch

Posted Tuesday, Nov 7th 3:14am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1186

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

QUESTIONS:

1.) Are all blocks the same...but with different innards? In other words, can I put a 2.7 crank, pistons, and rods in an old 2.3 block casting?

2.) Why is the 200 style head feel like it does better in low rpm's? I always liked the pull of an E21 323i engine better than that of a E30 325is engine at the low rpm range.

Early on in life I put a 325i engine to replace a 323i engine in an E21. I felt the car lost a lot of its bite.

Posted Tuesday, Nov 7th 3:24am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 15

NY, USA
82 528e2i 84 320i/4 80 320i

In the USA the 885 head can be found on any E30 325i(s) '87-'91 (convertibles went as far '92 or '93 IIRC) as well as the '89-'90 E34 525i.

I think any M20 intake should bolt up if you use the associated valve cover and support bracket. The manifold from an E30 323i is a good choice but you should get it port matched.

myersport

Posted Tuesday, Nov 7th 3:55am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 184

east tennessee
'82 320iS. '91 327iC

All blocks are not the same. The 'e' blocks have a higher deck height and different rods than the 'i'. It is imperative to keep the bottom end as is if using factory components. When ordering custom pistons they will ask what block and which rods you are using to be able to get the proper piston.
--Dennis

realcrouton

Posted Tuesday, Nov 7th 5:38am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 62

Washington, USA
1977 320i, 1981 323i, 1991 325ic, 2000 328i

Thanks TJ, I'm off to the wreckers!

-Dave

Marquis_Rex

Posted Tuesday, Nov 7th 8:48am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 492

UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT

Hi, the 885 cylinder head on a 2.7 litre works very well with a hotter cam.
I don't think the same is true on a #200 head. To put it another way, you would get alot less benefit using a hot cam on a #200 head set up than an #885 set up, purely because the #200 cylinder head can't flow enough air at higher rpms.

Another point of note is all the talk of low end torque- which IS important. However it's also important to note that the cylinder head and inlet runner set (runners of lengths up to 480mm) up will effect the torque between around 3500 to 5300 rpm roughly.
Below that both engines torque curves will be effected more by exhaust tuning effects. The part of the exhaust system near the tail boxes will have an effect on the torque curve at 1000 to 1300 rpm and as you move up the rev range the torque curve is more effected by the system closer to the engine, until intake system tuning effects the torque curve at 3500 rpm. So a #200 set up may have alot more torque at 3000-3500 rpm than the #885 set up but not neccessarily at 1500 rpm. It's one of the secret tricks I use on engines, when there's an OEM with a hole in the torque curve somewhere and it's up to me to address it. At even higher engine speeds (5500 upwards), the torque curve is effected more by port flows themselves, exhaust back pressure and the losses at the air box, throttle, plenum entry etc etc

Thanks for all the complements guys, and just think, despite all this knowledge I'm still finiding it impossible to get a job in the USA

melloh

Posted Tuesday, Nov 7th 1:32pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 444

California, USA (San Jose)
1980 320is, 1991 318is

Marquis - Thank you for taking the time to explain this and everything else past, present, and future. I'm a complete greenhorn, so this helps in my (extremely) gradual acquisition in automotive knowledge - especially because you seem to have a knack for explaining it in a clear, coherant, comprehensible manner w/ just the right blend of vernacular and techiness for the challenged (me). In fact, your posting style would be good for the FAQ pages.

And yeah... I can imagine it's tough with all the US companies downsizing bigtime. My cousin is worried for when he finishes school @ UC Davis in mech engineering. All that schooling and knowledge and nowhere to go.

MayanArch

Posted Tuesday, Nov 7th 4:09pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1187

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

Marquis....like I told you....the auto industry is the most protected job market in the US. You may as well tell them you are an Iranian-born Muslim looking for a job in a nuclear laboratory. Look for a non-auto related engineering job.

QUESTIONS:

1.) Why port match an ETA intake, when you can port match an "I" intake that is coupled with a better flowing throttle body and runners?

2.) Is velocity created by the intake runners or by the ports at the head?

3.) Why does the length of the intake runner affect the engine? It is still naturally aspirated and at atmospheric pressure going into the ports. I can see diameter of the intake runner being a big issue since it clearly restricts volume, but why length????

Marquis_Rex

Posted Tuesday, Nov 7th 10:04pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 493

UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT

MayanArch wrote:

Well over te last few months I had five interviews with the same company who were willing to sponsor me and my fiance/future wife to move over, the final interview I thought went ok, but in the end they decided not to pursue so I failed and they spun me some lie as feedback- so it's a bit of a sore point at the moment.

Anyway, back to your questions:

1)the 325i "885" intake manifold IS a better match, it has the correct runner length, while the eta manifold has too long runners for good top end performance.
2)The velocity is actually created by the action of the piston moving down the cylinder and causing a suction which transfers through the open valve into the port and into the runner.
3)Your analysis of the situation considers the restriction aspect in terms of flow but doesn't consider the "tuning" aspect. The restriction aspect that you've touched upon is relevant mostly at high engine speeds- which is why port flows, exhaust back pressure and inlet air box losses become increasingly important.
The runners are a certain length to boost/tune extra fresh charge into the cylinder at a pre-determine point in the rev range. As the piston moves down a rarefaction wave traverses up the inlet runner and then reflects off the open end at the plenum, changes sign and heads back toward the valve/cylinder. This can happen a few times. Most road engines usually utilise the second or even the third wave of this reflection. The length and diameter of the runner is tuned/matched to get the correct characteristic of engine torque curve.The inlet runner dimensions in the case of these M20 engines will predominantly effect 3500-5300 rpm- around the peak torque region.

MayanArch

Posted Friday, Nov 10th 4:14am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1189

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

Marquis,

I still dont understand why the 323i engine feels like it has more bite than the 325is. Yes, the 325is engine has more upper end power, but otherwise feels tamer than the 323i......and the ETA for that matter.

I know a lot of the ETA bite comes from the 2.7 bottom end, but it also seems more responsive at lower end RPM's.

Marquis_Rex

Posted Friday, Nov 10th 11:31am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 494

UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT

MayanArch wrote:

Could be a number of things. Was the exhaust geometry the same on both cars?
What about ignition? The ignition characteristics on the L Jet and K jet cars is an approximation by distributor at best compared to Motronic map.

What about cam profiles? What was used?
The 325i does have bigger ports and better flowing cylinder heads, but the camshaft has been optimised to regain low speed torque. The 325i achieves 85% peak torque at 1900 rpm, compared to the old E21 which achieved it at about 2150 rpm. Even the 731 cylinder headed E30 323i was a little less peaky than the E21-according to BMWs own figures...

Also, "seat of the pants" dynos are notoriously unreliable, it's possible that something as simple as "throttle progression" or throttle response was being factored in as "low speed performance.
I don't have time to get into it right now, but Throttle response, low speed torque, and throttle progression are very different things and not neccessarily related and can quite often be mutually exclusive

imaradiostar

Posted Friday, Nov 10th 5:30pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 942

Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i

Yeah, I have to disagree on the 323i versus 325i thing. A correctly running 325i engine feels strong all the way to redline, something a 323i engine never seemed to do. Just one man's opinion.

I've said things about the butt dyno before- suffice to say they're notoriously unreliable.

jamie