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Tech Forum : Fantastical but plausible high revving 323i

- BMW E21 Community
   - Tech Forum
      - Fantastical but plausible high revving 323i
Marquis_Rex   Posted Monday, Jul 12th 2:55am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 119
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
Hi folks.
I was up in my head fantasizing about possible E21 323i conversions. In fact it was while driving both the Porsche 993 turbo and 928 S4 (later) that got me thinking about this: Alot of torque can be exhilerating, but sometimes for fun, a smaller engine revving can ALSO be fun. In the above mentioned beasts certainly, there is NO room on public roads to come anywhere near to exploiting the engines potentials.
the 911/993 Turbo doesn't SING like my 323i 2.7- it bellows and shouts and shrieks like a wild animal! Obviously I'm a fan of big grunt engines-else I wouldn't be going ahead with my 3.1 litre M20 but nevertheless it got me thinking about other possible cost effective conversions.
I started to think about a high-revving 2.3 litre M20- that sings and is rather peaky, and suited to a dog leg and an LSD. Rather in the vein of the E30 M3 but with a 6 cylinder instead.
I'm not going to pursue this conversion- but it's nice to think about and I think it would work.
So after a bit of analytical work- this is my proposal for a 2.3 litre revver.

Use eta/325 i block (because the 320/6 323i/6 block has water ways between bores) and over bore to 86 mm.
Use 66 mm throw crankshaft from 320 i, preferably a forged affair from an M50 320i! This crank has tremedous potential and is extremely strong- the crank pins and mains overlap ALOT and if made of forged steel- will be better- of course being a BMW it is fully counterweighted anyway.

Use either 325i E30 135mm long rods of may be 140 mm rods from either a 318is or an M50 or may be even 145mm throw rods from a 316i!
The deck height of an M20 ranges from 206.7 mm to 206.2 mm- such that if a 206.2 mm height deck was taken and a 140mm rod used, you would need a piston compression height of 33.2mm. I don't think it would take too much doing to find a piston that had an 86mm bore, with a compression height of 33.2 mm (or slightly altered to suit), in the BMW armory by thumbing through a Mahle or KS catalogue [thus keeping more to the budget appeal of this project].
Use a 325i E30 "885 cylinder head- lightly ported (including 3 angle valve seats) using slightly oversized valves to, say 43 mm i liu of the normal 42mm.
Use a schrick 284-272 cam shaft (11.4/11 mm lift).
Use the E30 325i inlet manifold and a throttle size of at least 65mm diameter.
If using European fuels you could aim for 11.2:1 CR and run it ok on 98 octane.
Tuned exhaust lengths of around 850-1000 mm long.

All my analytical work, comparative work and experience shows this should yield close to 200 Bhp assumming everything has been done correctly.
It will make less torque low down and potentially have worse combustion efficiency (due to the worsened surface to volume ratio of the combustion chamber), but this will be offset by the lower pumping losses of the wilder cams and higher compression ratio.
Peak torque is likely to be at around 5500 rpm and peak power between 6500 rpm to 7000 rpm. The rev limit could be up to 7500 rpm I reckon. You would have to make sure you had your valve springs sorted and got appropriate rocker arms.
Let me know what you guys think!

[edited to say: The engine would be more in character to some of the earlier 1970s Small capacity Porsche 911 engines in terms of power delivery and would be suited to a lightened E21 shell]

JJG323   Posted Monday, Jul 12th 4:41am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 124
   
Reading MA USA
1979 BMW 323i
Exactly my thoughts. After talking to Ray, thinking about engines for a long time, M50, m52 2.5, 2.8, and 3.0 as well as the big six conversions, I concluded the 2.8 or 2.9 liter m20 was the way to fly.

I am using a knife edged 524td crank and a 1989 325i with forged pistons bored out to 2.8 liters.

Metric mechanic pistons, and
i have a shrick 288 cam and am in search of a 885 head. I also have the 325i rods. I am lightening the 325i flywheel.

Bottom line: it radicaly transforms the car, and it sits in there close to stock.

Its a lot of bang for the buck!

Joe G
79 323i

uberpanzer   Posted Monday, Jul 12th 7:54am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 27
   
San Diego CA
You want all FOUR listed?
Just be carefull with how high you are revving it. The reason that the engine builders at BMW went to the 4 cylinder S14 for the race motor (vise using the S38/M88 for the full-on DTM assualt) was that they saw problems spinning the crank at extremely high revs. I have heard of the 3.5 CSL's motor going to 9K, but they were NOT mass produced motors, so there must have been some sort of special modifications down to get things going that fast. The newer S54 revs pretty high, I believe in the 8K range, but then again tech has improved a bit since then.

JDBeyer   Posted Monday, Jul 12th 8:07am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 118
   
N. Humboldt county Ca.
82 323i on steroids
So if my quick math is right it would be 2300.29cc. Rev. until the rockers break, and like it. It- would be along the lines of early 911's! Sound like a fun engine to me...
I have always been fond of the short stroke rever engines, They just like to be "beat on".
As for the S54.. I work at a small BMW dealer and we just replaced the first E46 M3 engine here with rod failer at 20,000 mi. There are only 3 E46 M3's around here. This is the engine with rod probloms that BMW extended its eng. warrenty to 100,000.
I do not care for fractured cap rods, and the new M crank and rods do not look as nicely made as my S50 counterparts in my M20/S20. (S20, cool idea Marquis) Just my opinon: Jeff

RDAvena   Posted Monday, Jul 12th 8:18am [Edit] [Quote] [IMS] [View car]
Staff
Post nr. 672
   
SELECT * FROM users WHERE clue > 0
1981 323i, 1988 545is, 1997 528i
uberpanzer wrote:
The newer S54 revs pretty high, I believe in the 8K range, but then again tech has improved a bit since then.


if the proper care is taken to balance the rotating mass and with the same consideration taken into account for the rebuilding of the head the M20 motor can rev safely to those limits. This can be done for small $ on a well planned engine budget.

Granted a 'mere mortal' stock M20 is not up to the task, but then we are talking about "built" engines. For an extra 200.00 deducted from the 'automotive jewelry' you know, short shifters, coil over kits that will never be used, white faced gauges ect, and placed into the engine, it well rev safely to those limits and hold. Just not too many people are willing to make that type of sacrifice. Show usually being more important than go. Last time I checked the S engines are nothing like the M engines. Not exactly apples to apples there.

But safe to say that a 2.3/2.5/2.7/2.8-9, stroker or not, will rev past 7000 and with a single cam.


JJG323   Posted Monday, Jul 12th 11:50am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 125
   
Reading MA USA
1979 BMW 323i
6 k rpms is fine with me.

I really just want my car back and a chance toput th3e new engine in.

Joe


Shahpor   Posted Thursday, Jul 15th 3:27am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 5

London, UK
Nissan :(
Marquis_Rex, thats brilliant!

I have also been thinking about something along these lines for a while now.

However, I was wondering what it would need to take it a bit further? What I mean is, what extra engine work do you think it would be in order to be able to rev to 8000rpm safely and repeatedly?

From what I have read so far, some sort of crank strengthening would be in order as well as some stronger rockers & shafts. Still, as you obviously know more on the subject than I do, I would appreciate any insight you might have on the matter.

Also, am I right in assuming that generally speaking the higher it can rev the higher the peak power output would be?

Thanks.

imaradiostar   Posted Thursday, Jul 15th 4:38am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 19
   
Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i
I think you'd reach a point where the 12 valve head would become a limitation- though perhaps not until more than 8000 rpm. Can anyone speak to this?

I believe some M30 and M10 pistons are 86mm- I don't know the compression height though.

Max   Posted Thursday, Jul 15th 8:14pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 79
   
OC, CA, USA
85 635CSi euro, 89 325iA
Well, on the rev issue I can add that I revved my stock and far from being new M20B23 up to 7000-7200 all the time when I had stock cam. As far as I've heard the 1st thing breaks are the rocker arms, happens somewhere around 7800 RPM's, but not necessarily. I personally saw my friend revving his E21 320 M20 up to 8000 RPM's ( w/ hot cam), sounded good
I doubt one would want to go faster than 7500 on M20 w/o mods.

Max

m10_power   Posted Friday, Jul 16th 12:17am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 68


I've got an 2.0L M50 at home, not going to be much good to me with the V8 going into my E36

I'd sell the crank I'm sure, no demand for these engines in north america.

The bottom end with that short of a stroke would hold up to 10k+(careful balancing of everything rotating attached to the crankshaft is key)

Problem with a NA engine would be to rev that high effectively making power would require a high lift long duration camshaft that would end up breaking the stock rockers. A turbocharged version with milder camshaft would pull without much of an issue, would sound crazy spinning that fast. Either way I'd go with something fancy for rockers, not sure what is available, also dual springs and ti retainers and valves to keep the weight to a min.

Marquis_Rex   Posted Friday, Jul 16th 1:52am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 121
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
As has already been said, the next weak point when revving on our mythical short stroke engine are the rockers.
The M20 rockers have an average ratio of 1.55 and similar in dimention to early Porsche 911 rockers arms but can't be interchanged. The reason I mention the 911s ones, is because they are made of alloy, as ours are, and can rev around the mid 7000s if not a little higher. In racing, they were replaced for steel items (with no adjustment)- I'm not quite sure how high the racing 911s (934s) revved- but definately over 8000 rpms. I've found that the M20 rocker arms break around the fork region. The ones that break first are the ones that have porous metal in their casting in that region. The fact that they break there also means it is due to an inertia loading and that shot peening won't help (also the material doesn't lend itself well to this).
What I do, is bead blast the fork region and check for porosity- if I find it, these rocker arms can be used reliably on conventional engines that rev safely to about 7000 rpm. If I find a good non porous casting, well I'm not sure of the limit, but mid-to high 7000s sounds reasonable.
The crank I hypothesized, should be quite reliable. It's such a short stroke, and we already know that even the longer 325i and 323i stroke cranks with less over lap and cast iron construction can take a smidgen above 7000 rpm. With the forged construction of the M50 and the short stroke the rev limit should be greater. I can only hypothesize- and guess that a 7500 is a resonable safe and conservative limit.

The biggest problem on a straight six is the torsional vibrations. This is due to the length of the crank shaft- its natural frequency is around the same region of the working engine speed range of an engine- this means that at a particular engine speed- you can hit resonance- and should you hold it at this speed- the crank can break! What manufacturers do, is do tune this out, by using the torsional vibration damper- this is the rubberized disc that sits on the nose of your crank. The problem is that each TV damper is tuned to the engine system of pistons, conrods, flywheel,clutch housing etc etc. When you go about modifying the engine, you CHANGE this system. A manufacturer would re tune this- but it's not easy for us to do so-without special analytical tools or using long winded maths!
So this is what I fear, it's OK to rev through- but holding revs- could cause problems. I've seen engines on dyno break apart due to this-they were tuned wrongly and the revs were held. The first sign is the mal-tuned TV damper shreds its rubber coating! I'm not sure what revs the TV resonance occurs at though- it could be a resonably low speed....

Marquis_Rex   Posted Friday, Jul 16th 2:03am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 122
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
imaradiostar wrote:
I think you'd reach a point where the 12 valve head would become a limitation- though perhaps not until more than 8000 rpm. Can anyone speak to this?

I believe some M30 and M10 pistons are 86mm- I don't know the compression height though.


The limiting factors becomes the valve area feeding the cylinder.
Porsche used to get around this by making their engines very over square- and hence being able to fit in humongous valves. The only problem with this solution is that an savagely over square combustion chamber doesn't burn as efficiently- ( and believe me- you DO notice in terms of performance). I've seen very over square engines on engine dynos- deliver the Volumetric efficiency and JUST NOT deliver the power or torque ( to speak nothing of what it does to fuel economy!). Some manufacturers of two valvers- who are trying to get good breathing via the over square route -try to claw back some combustion efficiency through the use of twin plugs. Good examples of this are the late air cooled Porsche 911s and the Dodge Hemi- but this solution isn't as good as using a 4 valve pent roof in the first place. So next time someones cites that 4 valve combustion chmabers give good breathing- rememmber this is only HALF the story, what they actually allow you to do- is have good breathing for a given combustion cylinder dimention ( that you would have had to go far more over square with- with a two valve to get equivalent air flow) and hence retain decent thermal efficiency too!

As you start to design to get more and more power out of the engine at higher revs, with a not-too-oversquare-two valver - due to the restriction- your rev band narrows, and peak torque is typically engineered to occur close to peak power- JUST to get that top end out put. This isn't the case with decent valve area/4 valves.
The longer duration cams imperative get high top end power from a not-too-oversquare two valve engine means that low speed torque is lost quicker too.

Shahpor   Posted Friday, Jul 16th 2:24am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 6

London, UK
Nissan :(
So what you are saying (and please correct me if I am wrong in this) is that the 12 valve straight 6 would require too much work to get it to 8000rpm to make it feasible?

Shame

I would have liked to have seen a 323 with that capability....

Still, if you have any other suggestions as to how it is could possibly be done, please tell me more. I find this all very interesting.

JJG323   Posted Friday, Jul 16th 5:10am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 129
   
Reading MA USA
1979 BMW 323i
-Marquis-:
The 524 turbo disel crank is what i am using.
Its forged and its strong as anything.
I am Knife edging this and after that I am Cryoing it to make it even harder.

Question: can this knife edged and cyroed 524 td crank ever BreaK?

After its cyoed I am putting it in my 2.8 liter stroker and removing the eta one.

It should rev high. Is 7k feasible?
The car should fly, due to its light weight nature. I think it will be awesome. I dont know who fast but according to Jim at metric Mechanic "it goes like Stink."

I also have a lightened 325i flywheel and Shrick 288 degree cam, with K jet and yeah I am gonna use the 325i manfolds and 885 head.

thanks

Joe

RDAvena   Posted Friday, Jul 16th 7:41pm [Edit] [Quote] [IMS] [View car]
Staff
Post nr. 686
   
SELECT * FROM users WHERE clue > 0
1981 323i, 1988 545is, 1997 528i
Shahpor wrote:
So what you are saying (and please correct me if I am wrong in this) is that the 12 valve straight 6 would require too much work to get it to 8000rpm to make it feasible?

Shame

I would have liked to have seen a 323 with that capability....



Why? Are you going to be running it in F1? Do you want to compete with Hondas? Actually this is a step down but for sake of argument... This is an engine that will be used on the street correct?

Granted the engines can rev to the 7K or whatever limit was posted last but if you just want it to rev high and not have torque/power then by all means that is what hondas are for. You may want to study some of the dyno charts produced by BMW engines and look at where the power of the engine is created. At a certain point the power just drops off. Sure you can cam the engine and do other things to move the power band over but then that would sacrifice the driveability of the engine. As an example ever listen to any Formula 1 engine idle? At about 6000 revs? Not condusive to streetable performance.

Many here are mistaking the rev-ability of the M20 engine with the real world powerband. "Oh the engine can rev to 7500, it will make power all the way up there." Wrong! The way it should be looked at as is that the engine will not self destruct if you miss a shift and happen to place your engine in that type of situation. Revs does not always mean power, Honda proved that.

Shahpor   Posted Friday, Jul 16th 8:25pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 7

London, UK
Nissan :(
Actually I do want to compete with Honda's

Anyway, I understand what you are saying. I primarily want the car for track days and the occasional road outing. I certainly don't intend to use it everyday!

Also I understand only too well what you are saying about power dropping off at higher rev bands. When I say an engine that revs to 8000, I mean puts strongly to 8000rpm without too much drop off.

That is why I was so interested when Marquis said in his first post that his theoretical engine would produce peak power between 6500-7000rpm and peak torque at 5500rpm.

What I originally wanted to know is if this can be extended a little so that, lets say, peak about was between 7000-7500rpm and peak torque at around 6000rpm. Now I know that would make the engine rather flat at lower rev's and it would be a pain to drive in normal traffic, but as I have already stated, that is not what I wanted it for.

So I am not saying that it is exactly what I want in an engine, I was just wondering if anyone had any insights into making the engine a bit more 'peaky'.

Thanks again.

BruceH   Posted Friday, Jul 16th 8:45pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 181
   
Atlanta, GA USA
81 323 Baur, 85 745
Shapor,

Theory is great, real world is a whole 'nother issue. I agree with Ray that you need to look carefully at where the m20 makes power. The 8k capability is not needed.

Bruce H

Shahpor   Posted Friday, Jul 16th 9:01pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 8

London, UK
Nissan :(
Thanks Bruce.

Like you say, this is only theory for now. However, the idea fascinates me and I am just wondering whether it would be possible or not.

If someone said to me you could get the engine to 8000rpm but peak power is at 6500rpm, then I would say there is no point. However, if you could get the engine to produce good power that high up, then it might be worth thinking about.

And you are right in that the m20 isn't particularly suited to this task, but that is what this is all about, if it is possible to modify it to cope.

Thanks for the input.

Marquis_Rex   Posted Friday, Jul 16th 10:55pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 124
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
I'm with you guy in terms of needing torque, obviously I agree or else I wouldn't be taking my own engine out to 3.1 litres.
But fitness for purpose, if the guy knows the compromises involved, and is curious about a revver- that's fine.

Also, it IS possible to build an engine that makes resonable low speed and great top end, but very rare. Honda DON'T do it, BMW do it with the Euro- S50 3.2 litre M3 engine.
The Jag 3 litre in the S type makes good top end power AND low speed too. I don't think it's possible in an M20, or at least very difficult, because you don't have Variable cam timing to play with. Careful matching of components ( say, using exhaust scavenging, combined with careful ram tune matching and cam timing) could go a long way to having an OK engine- but it would be a challenge- with my 3.1 litre- I'm aiming for reasonable low speed torque- perhaps 9-9.5 bar BMEP and outstanding top end.

Anyway-back to the topic at hand-Shahpor, structurally, I really honestly DON'T know if the engine could withstand 8000 rpm. I would reccommend getting rocker arms specially fabricated, out of steel. In terms of breathing, The basic ingriedients are there, the ports are steep on the M20 and straight. A bore and stroke of 86/66mm is sufficently over square enough to accomodate decent ports to fill the cylinders. But I believe you would have to go for cams longer then the 284 duration I did my calcs with. Anything above a Schrick 288 and the amount of overlap causes problems with K -Jetronic Injection. To be honest an M50- with the hydraulic tappet system removed and replaced for solid bucket tappets might lend itself better for this kind of activity. Also, I rememeber hearing about crank bearing lubrication problems at high revs on BMW M20/M30 straight sixes- I'd have to look into it.

Shahpor   Posted Saturday, Jul 17th 12:46am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 9

London, UK
Nissan :(
Thanks for that Marquis.

It would seem then that the m20 would require just too much work to make it operate at those limits.

I suppose a 7000rpm limit with peak power somewhere around 6000-6500rpm would be much easier.

I am curious though. On a standard 5 speed box, would you be able to keep the engine 'on boil' as it were. What I am wondering is if you revved to 7000rpm, would you be able to keeps the revs up enough between gearchanges to keep the power flowing well?

I think I just have got too much time on my hands thinking about these things!

Thanks again.

JDBeyer   Posted Saturday, Jul 17th 8:23am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 121
   
N. Humboldt county Ca.
82 323i on steroids
Shahpor, I would think that keeping the revs up is just a matter of tight rear gearing or a CR 5 speed.

Marquis, I had witnessed brg. probloms years ago with some hot M20s we built at Hardy&Beck and some after those days. I did some homework when I started building the 3.0 I am flogging and loving today.
I remembered in a model update from 1988 that BMW made a change to the main brg. in 4/88 M20 engines. This brg. is only used in a block made after 4/88(it has 2 locating tabs insted of the usual 1 tab) It does not have a full circle oil grove. The grove stops on the very edge of the the brg. in the cap. This gives more brg. surface to the crank, cuts off extra oil to the rod on the upswing and cuts down on the amount of oil thrown around in the block(Windage). I am sure there are other resons BMW made this change that I did not mention or even think of.
This is the same main brg. used in the 4 valve 6 cyl.engines.
If nothing else it seems to be a better choice, if you can get one, for a hot rod M20. What do you all think??? Jeff

Marquis_Rex   Posted Wednesday, Jul 21st 11:05am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 126
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
Jeff this MIGHT explain why there are two different heights listed for the earlier and later blocks.

I guess there isn't a way to retro fit or ammend the earlier block to the later spec...

This means I am best off to try and source a later block- in order to be thorough-for my 3.1 litre conversion.

JJG323   Posted Thursday, Jul 22nd 2:14pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 136
   
Reading MA USA
1979 BMW 323i
Marquis,

from what I have heard, a 3.1 liter stroker out of the newer M20 block would be pushing the envolope.

This is becasue of the distance between each piston in the block. A 2.8 is doable, and in the 2.9 metric mechanic engine its close.

Can a newer block like the 1989 one I have really be bored out to 3.1 liters? What diamter pistons and what would be the bore and stroke of the engine?

Thanks

joe

Marquis_Rex   Posted Thursday, Jul 22nd 6:38pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 127
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
Joe, it's OK, I WORK in engine design and development. My task isn't to simply listen to what old mechanics say- I'm an engineer AND a mechanic and I aim to not only made a rapid car but push the boundaries using my skills and experience. If I experience an engine failure, so be it, its all learning. I still won't have wasted as much money as those who buy new cars!

An 87 mm bore leaves me a bridge distance of 4mm between bores. This is cutting it close. The NG V6 engine that was designed by BMW but subsequently canned,(supposed to go into Land Rovers) has a Bridge distance of 4 mm and is made of ALLOY. The V8 5 litre M5 engine has a bridge distance of 4 mm and is also made of alloy.
The current E46 S54 M3 engine has an 87 mm bore and a bridge distance of 4 mm too- its block is cast iron (for all its problems- none of them are head gasket or block related). It IS true that BMW did have problems with the S14 engine and weren't able to get a bridge distance of much less then 5 mm. I believe the weakest link will be the head gasket. It is something I would NOT reccommend anyone do, but would try myself. It is likely I will get some bore distortion.
I'm going to dig deep into head gaskets, I have someone who does alot of analytical work on these to consult- as the head gasket is likely to be the weakest link.

I think the biggest problem will be getting a piston compression height of 23.8 mm- because of the 86.8 mm stroke I'm trying to use. If I find this too difficult- I'll put a spacer and tallen up the block.

imaradiostar   Posted Thursday, Jul 22nd 9:19pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 24
   
Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i
my reply is a little off topic, but I feel it applies since it would allow for a little higher-performing version of this idea.

something I've considered- why not start with an m50 and modify it to use CIS fuel injection and a standard distributor? I've considered this for one of my own projects- it'd be an exercise in combining old and new technology in an interesting way. If you used a later alloy block, it'd probably end up weighing less than an m20 as well.

jamie

velocewest   Posted Thursday, Jul 22nd 10:13pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 283
   
Oregon USA
e9, e12x2, no E21?
Would a copper head gasket help with the narrow bridge gap? Or a cutting ring gasket?

Tony

M42powered   Posted Friday, Jul 23rd 12:29am [Edit] [Quote] [IMS] [View car]
Staff
Post nr. 365
   
Arizona, USA
1981 BMW 320i
imaradiostar wrote:
my reply is a little off topic, but I feel it applies since it would allow for a little higher-performing version of this idea.

something I've considered- why not start with an m50 and modify it to use CIS fuel injection and a standard distributor? I've considered this for one of my own projects- it'd be an exercise in combining old and new technology in an interesting way. If you used a later alloy block, it'd probably end up weighing less than an m20 as well.

jamie


There is a guy in tucson that turbo charges stuff... the first thing he does is pull of the EFI and put on CIS. He says it's the easiest cheapest way to go turbo.

M42powered   Posted Friday, Jul 23rd 12:30am [Edit] [Quote] [IMS] [View car]
Staff
Post nr. 366
   
Arizona, USA
1981 BMW 320i
velocewest wrote:
Would a copper head gasket help with the narrow bridge gap? Or a cutting ring gasket?

Tony


I just hope you're ready to battle with that gasket for a while. It is a cold day in hell when those things seal all the coolant passages.

Marquis_Rex   Posted Friday, Jul 23rd 12:49am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 128
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
imaradiostar wrote:
my reply is a little off topic, but I feel it applies since it would allow for a little higher-performing version of this idea.

something I've considered- why not start with an m50 and modify it to use CIS fuel injection and a standard distributor? I've considered this for one of my own projects- it'd be an exercise in combining old and new technology in an interesting way. If you used a later alloy block, it'd probably end up weighing less than an m20 as well.

jamie


You've read my mind! I've thought about this LONG and hard!
I've wondered about using K Jet on it and trying to retro fit a distributor.
You're also right in that the alloy block M50s are very very light engine, similar to other manufacturers 4 cylinders (DESPITE having a 25 kg crank!)
In terms of dimentions and flow figures and stuff I also have lots and lots and lots of data on the M50 engines too. Only problem is that I wouldn't be able to bore the alloy block units I don't think. I have a theory that the alloy M50 is slightly flimsy if you bore it above 84 mm. My reasons for thinking this are

1)BMW continue to use an Iron block on both the Euro M and US M versions when the bore the basic architechture out
2) Even in the 330 Ci, BMW persist in lengthening the stroke and keeping the 84mm bore- even though the engine has now become savagely undersquare. I KNOW their thinking- they WOULD have made the engine oversquare by now at this stage of development if they could have, to liberate more flow. Good for them that they were able to attain they power figures without having to but The fact they didn't hints that there could be some alloy bore distorsion issues.

I reckon its not helped because of the extra heat sink from cylinders of the inline six compared to a V6.

So if I were to go and use a 3 litre long stroke M50 block- I reckon I wouldn'tbe able to get much more then the 230 Bhp- such a long stroke with 33 mm valves is already at the limit it terms of flow. Now rememeber the power figure alone isn't enough for me- it's an engieering exercise for me....for a two valve I need to get close to 80 Bhp / litre for a four valve- 100 Bhp/litre of over. Why? Because I'm a sad engineering nerd!

The other issue I had with the 4 valver was the noise. Sound quality is very important to me. I'd gladly lose some HP for a better noise.I've outlined in other posts how 2 valver sound better because of the longer exhaust duration and more sudden-early exhaust valve opening event. Well I could remedy this by ensuring the 4 valver M50 had a cam that had same exhaust valve event- although I'd probably be losing fuel economy and performance as a result!

So overall it's not totally ruled out and I'd be happy to still consider it!

Tony/Veloce I was thinking about a Copper gasket too, or perhaps a wire ringing one if it is possible to do do with a 4mm bridge distance!

Marquis_Rex   Posted Friday, Jul 23rd 12:51am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 129
   
UK
BMW 323i 2.7-as featured in Total BMW Nov 2002,Porsche 911/993TT
M42powered wrote:
imaradiostar wrote:
my reply is a little off topic, but I feel it applies since it would allow for a little higher-performing version of this idea.

something I've considered- why not start with an m50 and modify it to use CIS fuel injection and a standard distributor? I've considered this for one of my own projects- it'd be an exercise in combining old and new technology in an interesting way. If you used a later alloy block, it'd probably end up weighing less than an m20 as well.

jamie


There is a guy in tucson that turbo charges stuff... the first thing he does is pull of the EFI and put on CIS. He says it's the easiest cheapest way to go turbo.


Nick that doesn't suprise me, Its no accident that alot of the early eighties cars that were boosted continued to stick with K-jet, eventhe Porsche 911/930 Turbo, while the "lesser" 911 3.2 continued with EFI

Turbo3er   Posted Monday, Mar 12th 10:36pm [Edit] [Quote] [IMS] [View car]
Junior Member
Post nr. 1


87 325e 87 325es 94 325Is
This has definitely been quite the interesting read for me. everyone seems to have a good idea, and a nice hypothetical going. i'd say it could work, with some time and a little effort. I have a 2.7eta engine in my e30 with a 2.5is head dbl.valve spring,titanium retainers, hardened 7deg locks, 288/272 deg. duration 11.5/11mm lift cam, adj.cam gear, Is intake manifold throttle, housing, super sprint headers and full exhaust. ditched the stock motronic and put a plug and play mega squirt ems with a 60-2 trigger, and tech edge wide band. soft cut rev limit is 6800 and the hard cut limit is 7000. Bone stock 140k bottom end, and it pulls hard from tip in to the rev limit. so in practice it is very doable. been running strong for the last 6mo without a so much as a wimper.

jdench   Posted Monday, Mar 12th 11:01pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 174

Sussex, UK
1979 E21 323i, 1998 E36 323i touring
If anyone does get to 8k, make a sound recording! It would be the most wonderful sound in the world

Turbo3er   Posted Monday, Mar 12th 11:26pm [Edit] [Quote] [IMS] [View car]
Junior Member
Post nr. 3


87 325e 87 325es 94 325Is
if it makes it that high without perforating/ventilating the block i will.

hopefully i'll get the chance to put it on the dyno in the next couple weeks and do some tunning. will post results, along with pics if it self destructs.

kpeters   Posted Tuesday, Mar 13th 6:12am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 835
   
San Jose, Costa Rica
1981 320/6 Kastanienrot-Metallic 5spd
jdench wrote:
If anyone does get to 8k, make a sound recording! It would be the most wonderful sound in the world


Have heard it several times....> let's say my car is missing the rev limiter and the mechanic always get's happy with the throttle.

blair winter   Posted Saturday, Mar 17th 6:52pm [Edit] [Quote] [IMS] [View car]
Junior Member
Post nr. 1
   
Oregon, USA
'81 323i, '70 2002, '97 540i/S
Anybody remember the Johnson 24v head for the m20?! I have a great article scanned...

Greg323i   Posted Sunday, Mar 18th 3:20pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 304
   
Melbourne, Australia
1982 Hennaröt 323i
Post that article, I'd love to read it.


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