E34 m20-2.7l w/turbo

[Reckless_Kelly]

So I've heard of the 528e block with the 525i pistons and head on it, and I've located the 2.7l block and crank. What about what about putting a small, low pressure turbo setup on it, like 6psi or so. I also happened across a good turbo off of a volvo 240/740 non-intercooled motor, should be a Garrett TB03 AR .60. Is this comparable to a T3? I know very little about turbos (just that the one on my Duramax makes things FUN). I would like to run a lower mounted turbo with a small front mount intercooler.

I'm not looking for insane horsepower, but I would like for the car to "get out of it's own way".

The car is an auto right now, but I'm slowly sourcing the parts to do a 5-speed conversion.

[BillionPa]

try to find a variable geometry turbo, you will get less lag. and get the pistons coated, tungsten disulfide on the sides, and thermal barrier on the top.

[Jon K]

?? VGT turbos are extremely over rated - buy a T3/T04E and it will be great. BillionPa, do you have experience with the things youre recommending? Anyway - I am not sure which it is but an ETA head on an I block either raises the compression or lowers it. There is no need to do anything to the pistons as they are completely capable of gobs of power.

Forget using turbos off other cars unless you KNOW what they are and you KNOW what flange they use. A T3/T04E in like a .42 or .48 trim whichever they are, can be had for cheap. You can't run that low boost on a volvo turbo as theyre internally wastegated typically and thus you can only run as little boost as the wastegate is sprung for - theyre sprung higher than 6 psi usually 10 or 11. With the use of a Jetta 1.8T sidemount intercooler it would keep an engine happy @ 6 psi with no question.

[BillionPa]

i say get VG because the displacement is small and they will spool faster, am i correct in that assumption?

[Reckless_Kelly]

Anyway - I am not sure which it is but an ETA head on an I block either raises the compression or lowers it.

Putting the eta head on an "i" block will lower the compression, and vice versa will raise the compression. I'm trying to determine whether I need to leave the eta pistons in the block for thier lower compression design, that would make sense if I'm gonna throw a turbo at it. The eta head would be great for a turbo, except for the missing cam bearings and narrower ports w/ smaller valves.

The eta's have 8.5:1 compression standard, while the "i" has 9.2:1 comp. This difference is made in the higher crown of the "i" pistons and lower volume of the "i" combustion chambers. The eta pistons have a slightly lower crown and larger combustion chambers in the heads, but the longer stroke means that an "i" head on that block would probably make near 9:1, or maybe even higher. I'll have to get out the perfrmance books and find the calculations for CR based on bore and stroke.

How much boost would be too much for a 9:1 comp motor?

[BillionPa]

how much boost is too much also depends on the structural integrity of the engine parts, not just its compression.

iron block engines hold much more boost if you get strengthened con rods.

is the 528 aluminum block?

[Jon K]

528 E28? Should be iron. Boost is not related to structure strength of engine - think about it... you do a compression test on yoru motor, what kind of PSI figures do you see? 180... 190...200 psi in the cylinder chamber. So we're talking about adding boost in a cylinder that is able to handle WELL over 200 psi of pressure. You have a LONG way to go before you use so much boost that the head lifts, the rings blow out, or you do any sort of metal bending due to boost. Now, on the other hand, if you are running the engine for peak horsepower output (leaner) then yes you can damage components due to heat - but you are just as able to damage components due to leaning the motor while its NA as when its FI.

[Reckless_Kelly]

One thing to take into account though, is that 6psi=an increase of 54psi after the compression stroke, which equals a few more atmospheres. Like JonK mentioned, leaning it can be a real problem, and soo can running too rich in a turbo motor. Io the combustion camber is too small to handle the correct ration of fuel (liquid doesn't compress, the air does) then you get a water hammer effect that blows the weak link (headgasket, usually).

Long stroke motors creat higher CRs because instead of compressing 416cc worth or air into the combustion chamber, it's compressing an additional 34cc into the same size chamber. with 6psi behind the intake charge, that makes it 630cc of air fuel mixture getting squezed into that little combustion chamber, which is a 40% increase in volume, thereby equaling about a 12.6:1 Compression ratio equivelent (assuming we started with 9:1). If we started with 8.5:1, then it would come to about 11:1. Either way it would require some ignition retarding to eliminate detonation.

Another thing to take into account is that due to the restrictions in the intake tract, there is a slight vaccum in an NA cylinder before the exhaust valve closes (not quite a full 450cc), whereas with a pressurized motor, there will be more than 40% more mixture to be compressed.

Just a few things to keep in mind.