Stuck in the American mentallity....

[marakka]

So you folks have more access to the e30 models than we do in the states. I'm stationed in Schweinfurt Germany and have fallen in love with the e30.... mainly because its made me a ton of money shipping mtech stuff back to the states, but all told its a great car.

My friend and I have decided to venture on an endeavor of building a drag car from a junkyard BMW. We opted for a 325i. The popular thing to do stateside is build a stroker and turbo it. The stroker sounded like fun but the turbo sounded like money. Doing the research I've found that compression ratios (CR) are low in the states stemming from 8.0:1 to 9.0:1 In my searching I found mention of euro spec motors reaching 10.3:1 and even 11.0:1 But I coudln't figure out what motor that was pulled from. After reading a few articles from the various users on this board I've heard that some use 320i parts. The boards I use mainly are americans with american versions of the cars so they don't have the 316, 320, 323 or tourings to deal with. They don't have the 4.46 rear ends or the bilstein sport factory suspensions. So they can offer little advice on such topics as euro engine building.

Here's what I've got so far: Ported and polished 2.5i head with 284/284 11mm lift cam, oversized lash adjusters and rockers. New stock springs. 19# injectors and Nology wires. El cheapo headers and a ported throttle body. We are working the intake to port match the head. We have yet to tear the lower half of the engine apart as we are not sure what to do. We are planning to run a small shot of NOS (25-50) on the motor to produce the torque we think we need to get away from the line. The hope is to be able to produce (with NOS) about 250-275 hp and over 325ft/lbs torque in a stripped car and yield a 13sec 1/4 mile time.

Anyone help get me started on my euro build? Thanks in advance gentlemen.

Max

[Jhonno]

the 320i head is used with the eta bottom end to make a budget 327i

tbh - turbo gives better bhp per Ԛ£Ã”šÃ‚£

if you have already gone this far maybe an eta crank to give you the 2.7 capacity

[marakka]

Yes, the original plan was to find some sap selling eta parts in the states and snatch up the crank, rods and pistons and slap in for the easy 2.7 swap. Depending on year we would have achieved as high as the 9.0:1 ratio. But hearing that there's an 11.0:1 ratio available here, we want that as its much more along the lines of what we are doing as we have opted to go without the turbo

Yes the turbo would produce more bang for the buck but we haven't the access to it and we live by a rule..... if it can't be bought for less than $100 and it can't be traded for.... its not for our car. The only exception is tires. We realize we need good slicks.

[Jhonno]

higher compression ratio's were using custom pistons i think

m20b25's are 9 and 9.5:1 here iirc

[Kos]

on a stock 2.5 and 50hp NOS, 17" street tires 1 ran a 14.7 1/4mile. so play with diff and gearbox ratios you could find another half second if you use slicks, the way i worked it ont you will need 300hp to dip in the 13sec barrier, but as you will strip it you dont need to go that far. i one ran 100hp nos had so much fun and totally abused the car, and never once had a problem. they are very very strong engines.

[marakka]

Well... one way or the other this won't be a stock 2.5. 14.7 ain't a bad time for a stock car. Really suprising actually. I figure we should be able to shave that .8 to get into the 13's no problem. No interior at all minus a plastic drivers seat. The NOS setup we are looking at will give us 25 50 and 75 nozzles. I'm sure we'll play with all of em.

The 11.0:1 ratio is said to have been from the early m20b27 cars 83-87? Does this sound right? God that would be fantastic to run that much CR. And it was mentioned above that stock these cars are 9.0:1 over here? Is this true? What car has the higher 9.5:1 then? And why use the 320i heads instead of the 325i? That still bewilders me.

Max

[Jon_Bmw]

The hope is to be able to produce (with NOS) about 250-275 hp and over 325ft/lbs torque in a stripped car and yield a 13sec 1/4 mile time.

Being american, is this at the rear wheels? or as we English like to do things at the flywheel?

So what are you plans if you don't want to turbo it and you don't really want to do a stoker, all that power going to come from NOS, well until the bottle runs out anyway.

[marakka]

No no.... I DO want to do a stroker. But I want maximum compression ratio where as most people do the stroker and look for lowered compression ratios to achieve higher boost numbers. The HP numbers I'm thinking should be at the flywheel. If we can put an honest 225 to the ground with the car weighing around 2400lbs we think we should be good for a quick low 14/high 13 second run.

[Boots_Walker]

i cant remember the exact changeover dates etc with the eta pistons , i think its something like 1983 > 9/85 have the 11:1 CR pistons, after that the non-cat cars got 10.2:1 and cat versions got 9.0:1. note that those compression ratios are for the eta head which has smaller combustion chambers than the b25 head, if you use those pistons with a b25 head you will lose around 1 point of compression (that is not exact, but based on my calculations it is very close) so you would still get around 10:1 using the 11:1 pistons on the b25 head

there are new sets of 11:1 pistons on ebay.de all the time, might be easier for you just to pull them from a junkyard or something though

since you already have a modified b25 head this probably isnt important, but if you really wanted to run 11:1 using the factory parts the easiset thing would be to grab a 320i/323i head (731 casting, which has the same small combusiton chambers as the eta head but bigger ports, 7 cam bearings etc) and redo the porting. - just saw your question about the 320i, hopefully this paragraph answered that for you

[marakka]

Ok.... so making headway..... The 320 used the same eta combustion chamber on the head side? If thats so then I'll pull one of those and start grinding it down...... no biggie. We are half way through the b25 head so we can either keep going or stop... we aren't out any money. Theres no difference in valve size or cam bearings or anything from the b25 head? I'm asking because I've got a 284/284 cam on the way for the b25 head.

So... to look for.... Early e lower end.... pistons, c-rods and crank. 320i head.

Can I use the m20b25 block or do I have to use the b27 block? God I've got so many quesions I can't even remember them alll.....

YOu guys have been more than helpful thus far. I really appreciate it. Thanks a ton!

Max

[Boots_Walker]

the 320i/323i heads do have smaller valves (40mm/34mm as opposed to 42/36 on the b25) they can be replaced with the larger valves of course. also early heads used a single valve spring and different retainers, after 9/85 according to the ETK they switched to the dual valve spring setup. if you were still prepared to use a 320 head, one from a later motronic car would be your best bet as it should have the dual valve springs already (one less thing to worry about). the cam will fit fine

as for blocks yes you can use the b25 block, one thing i'm actually not sure about is if the deck height is the same on all m20 blocks. i've been told its the same on all but looking at this page http://www.bmwccn.no/rogaland/Mahle_m20.html it looks like the b25 might be fractionally taller? anybody know. i'm building a 2.8 from my b23 block and it would be useful to know in advance whether or not i will need 0.5mm taken off - havent got the engine out of the car yet so i cant measure it. as you can see from those piston diagrams the 11:1 pistons have a raised crown in the centre and the rest are dished - makes them easy to identify

just thought of another possibilty for your motor although it might involve a little more work...

my 2.8 will use the 84mm stroke crank from an m52b28, 130mm rods, and 8.8:1 b25 pistons which will end up producing around 9.8:1 with the 9mm extra stroke. if you used the 9.7:1 b25 pistons instead you would end up with a CR in the high 10's, using the b25 head.

a couple of negatives of going this route are machining costs - crank/piston skirts to make it work, rod/stroke ratio reduced from 1.6>1.55 (negligible difference really), probable higher intial purchase cost of crank... might all work out a bit too expensive?

after typing all that all in all i reckon your best bet would just be to pick up an 11:1 short motor and bolt your b25 head on, you will still have a nice CR with a lot less stuffing around. i dont know anything about tuning for nitrous but i'd guess that a 10:1 CR would give you a bit more safety there

[marakka]

Thanks for the info. Its alot easier to read in english than in German. ;)

We want as high of a CR as we can without breaking the bank. I've read all about the m50 cranks and so on and so forth, but the money involved is just too much. We have a budget.... if its more than $100 or it can't be bought by trading parts from the junkyard for it..... we don't need it. Exceptsions are tires and NOS.

So should I rework a b20 head or stick with the b25 head? I just posted up a WTB for the crank, rods and pistons. Anything over a 10.0:1 CR would be great. The numbers we are looking at should be right around 250 with 10.0 and that should put us at the high 13 mark with a gutted car. Thats where we want to be. from there its merely toying with what we can get to work and playing with different timing aspects and such to try and squeeze .01's outta the time.

Once again, thanks for the input and hope to hear more...