M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: Torsten on April 06, 2008, 06:07:15 AM
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Hi guys,
I'm from Germany and study mechanical engineering at the university of Karlsruhe in the 6. semestre.
Here we are going to convert a stock M42 engine from a E30 318is running with E85 fuel (85% Bio-Ethanol / 15% gasoline)
Due to E85 has a much higher octan value (104) we like to increase the compression ratio. So we ask ourselfs how much compression the engine can handle without blowing into tons of pieces. We have calculate a value of 13.4 for comp. ratio... but we are not sure if the engine can handle that.
I guess, that several guys here installed a turbo at this engine. Maybe somebody can tell me how much you can boost this stock engine.
Thanks a lot and greetings from Germany!
Torsten
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Not sure if high compression ratio is harmful to engine itself? It is usually detonation or knock due high CR that causes the problems.
Also, you need to consider dynamic CR in addition to static CR :)
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I don't think you will have problems at 13.4:1. You might consider a metal head gasket from Cometic. Also, the engine will be harder to crank over when starting, so a higher amperage battery may be wise.
Please tell us what else you are doing as part of the E85 conversion, as far as fuel lines, pump, injectors etc.
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We will do the following points:
-increasing comp. ratio to 13.4:1
-new camshafts with adjusted valve lift to avoid valve crashs.
-bigger injectors
-4 throttle bodys
-rev. limit 8.300 rpm
-lowering flywheel weight
-fine balancing of all rotating parts.
-megasquirt ECU w. Alpha-N control
-4 in 1 exhaust manifold
-2,5" exhaust system
-all gasoline feeded lines will be replaced.
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Not sure if high compression ratio is harmful to engine itself? It is usually detonation or knock due high CR that causes the problems.
Also, you need to consider dynamic CR in addition to static CR :)
Yes, you are right. But we have to know to which ratio we can set the compression without starting to knock.
Does anybody have experiences with E85 or does anybody boost his M42? If yes, please post CR, boost and octan-value of the fuel.
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oh mein freund...!i am not sure if the cylinder head will last long enough with that high cp of 13.4:1 ?! to enjoy the engine...:-)
with a turbo they usually lower the cp to 8:1 or so...
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do you put the engine into a car?? if yes... call me and i come to karlsruhe to have a look!! and drink some beer..
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I have a lot of experience with E85, and 13-14 CR will be fine from a fueling view, but I cannot speak for the engine, as I have never run e85 in an m42. Look into a fuel composition sensor. MS can run it.
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You will need
ARP headstuds, Metal cometic headgasket, and upgraded pistons rings such as the total seal rings.
You should also consider removing any sharp edges in the combustion chamber to avoid detonation and getting a 3 or 5 angle valve job done to ensure a good valve seal.
As far as determining what CR you can run i guess thats up to you guys, all fuels have a certain point where at a certain air/fuel ratio and at a certain compression they detonate.
Im not in college this week but i might be able to get some information on this when i get back.
Once you know that compression ratio you will want to adapt your active compression ratio to come in under this number.
Active compression ratio is determined by your static compression ratio and the overlap of your cam shafts.
Here is a useful link to a discussion about e85 ethanol
http://www.eng-tips.com/viewthread.cfm?qid=188508&page=1
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Where do I get total seal rings for the M42? I've have looked at totalseal.com but didn't find a kit for the M42. :-(
We have calculated, that he have do decrease the compression space between piston and cylinderhead of 2,4mm.
If we install a very thin headgasket from cometic, we will earn about 0,7mm so we have have to find 1,7mm more to remove.
The valve seats are very close to the head plane. Does anybody know how many mm we can remove from the head without injuring the valve seats? I guess, it's about 5/10mm?!
And does anybody know the maximum machining for the block plane? Maybe we can remove here some material, too.
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The valve seats are very close to the head plane. Does anybody know how many mm we can remove from the head without injuring the valve seats? I guess, it's about 5/10mm?!
And does anybody know the maximum machining for the block plane? Maybe we can remove here some material, too.
HEAD:
bmw specs:
- brand new head height = 140,00 mm
- max decked height = 139,55 mm
so you can remove max 0,45mm from the head...;)
BLOCK:
I don't have BMW specs.
I know that "ludiagsm" removed 2mm from the top of block for its turbo beast setup, read here where he wrote http://www.m42club.com/forums/showpost.php?p=28271&postcount=42
keep us updated:cool:
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Yes, he removed 2mm of the block, but having installed other rods which were 2mm truncated.
We will removing as much as we can at the block, but have to make sure that the piston will not contact the head gasket. So we need the underhang (is ist the correct english word for?? :confused: )of the piston skirt and the stock block plane.
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along with the .45mm reduction to the block wouldnt high compression pistons be a good idea, rather than trying to find an extra few mm in the machining of the block
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high compression pistons could be a good idea, too. But I've never seen high comp. pistons for the M42 :confused: because most of the people want to lowering the CR to install a turbo. Good old suction engine tuning seem to become pretty stale in comparison to turbo- or supercharging engines. :(
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high compression pistons could be a good idea, too. But I've never seen high comp. pistons for the M42
search...;)
http://store.nexternal.com/shared/StoreFront/default.asp?CS=vacmotors&StoreType=BtoC&Count1=256694972&Count2=173835396&CategoryID=1&Target=products.asp
enter in pistons and scroll until you see m42
this is what you'll find
M42 CP Forged Piston Sets, 13:1 CR
price $849.99 $749.95
code: CP-FPS-M42-13