matty h
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posted on 6/8/11 at 06:34 PM |
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BMW 6 cylinder engines
Looking at using a 6 cylinder BMW engine in a 7.There seems to be loads of different ones what are the best options in terms of cc and bhp.Also GKD
told me at stoneliegh that a 6 cylinder bmw engine and box weighed the same as a redtop and sierra box is this true.
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rodgling
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posted on 6/8/11 at 07:15 PM |
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For E36 (mid-late 90s), the obvious two are basically the 328 (220 bhp, 6200 redline, cheap, alloy block, 120 kg) and the M3 (320 bhp, 7400 redline,
expensive, iron block, 152 kg). No doubt the M3 is the better engine, if you can justify the extra cost. Both are very quick in a 7. There's not
really any reason to go for the smaller engines as the 328s are cheap enough already.
I can't really tell any obvious difference in steering weight and handling between the two (i've just swapped the 328 for the M3) -
I'm sure if I drove two well set up cars back to back I could, but it's not a massive difference.
The engine weight numbers came from here:
http://www.unixnerd.demon.co.uk/enumber.html
Not sure if they're wet, dry, etc, with ancilliaries, without, etc.
Gearbox is pretty light (30 kg rings a bell?), diff is heavy though. There's a good bit of weight to be saved with the flywheel.
The big issue though is height and length: it's not a small engine.
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Doctor Derek Doctors
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posted on 6/8/11 at 08:28 PM |
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The early E36 325i engines are also very good and the cars are dirt cheap now, I paid £400 for a 195 bhp 325i and is was a damn good car.
Don't bother with anything from an E30, the iron block 12V's are so ridiculously heavy that they would ruin a '7' and a 2.5
12V is only really good for 170-180 bhp.
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SteveWallace
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posted on 6/8/11 at 08:34 PM |
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I'm in the process of putting a 2.8 BMW engine into a Viento. Its a tight fit, but doable. One of the issues with none GKD 7's is that
the chassis is not designed for BMW sumps, which have a bulge on the side that gets in the way of the lower chassis rail. This is a fairly easy fix
if you know a good ali welder (see my photo archive).
As already mentioned, they are quite hight engines, so without a lot of sump modification you will either have relatively low ground clearance or have
to modify the bonnet.
Standard 2.8's are about 190 BHP as standard but apparently you can get another 30 BHP or so by using the throttle body and inlet manifold off a
2.5 as the 2.8's were deliberately restricted to keep the power down.
No idea what the handling is like as I've not finished mine yet.
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Nickp
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posted on 6/8/11 at 09:10 PM |
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I'm just looking into this at the moment too. I've got a Haynes Roadster chassis and a M52 6 cyl coming which will hopefully be fitting
together nicely The M52 seems to be the one to go for as it's alloy blocked rather than the earlier iron blocked M50. The trick is to use the
larger bore inlet manifold from the M50 onto the 2.5 or 2.8 M52 to free up about 20-30BHP ![](/images//smilies/bigsmile.gif)
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rodgling
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posted on 6/8/11 at 11:39 PM |
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The one downside with the alloy block engines is that if the head gasket goes, there is a pretty good chance you'll strip the threads in the
head trying to do it up again. Also, they're famous for the Nikasil issue - if you get a non-Nikasil engine then this is a non-issue, but
it's something to be aware of when sourcing an engine.
With the manifold swap - this is pretty easy / cheap, but there is a loss of torque up to, say, 4k rpm. Apparently you can fix this with a remap but
then it's not so cheap...
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franky
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posted on 7/8/11 at 08:59 AM |
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quote: Originally posted by matty h
Looking at using a 6 cylinder BMW engine in a 7.There seems to be loads of different ones what are the best options in terms of cc and bhp.Also GKD
told me at stoneliegh that a 6 cylinder bmw engine and box weighed the same as a redtop and sierra box is this true.
For the m3 lump it is, the others are lighter by about 30kg. If you design your chassis right so the engine sits as far back as possible you
can't feel the weight at all.
If you want to have an N/A engine you'll struggle to get the same bang for buck. Remember you can run these on the standard ECU too.
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