Found this quite interesting
Message: Listed below are the current modifications in my 1985 528e. Since the lounge moves as slow as it does, I hoped enough of you guys considering the e to i swap can use this to your advantage. I've done everything myself, so I garuntee all of this is entirely correct. Hope this helps somebody:
euro e30 320/6,323i cylinder head
brand new mahle pistons
325i cam, new rockers
complete 325i fuel injection, motronic version 1.3 with ebay chip
535 injectors
535 afm
325i intake manifold
325i throttle body
ireland engineering shorty headers
3 bar FPR
The euro e30 cylinder head, the 731, is great for a 2.7i. If you can find one it works great for pre 1988 etas because it has the same size and shape combustion chambers. Bolts on to the eta bottom end, dished pistons and all, and retains the eta's 9 to 1 compression ratio. The i has slightly larger valves, but you wont miss them until over 6200 rpm if your valves are cut right. Its said to be good to around 200 horsepower. I recommend it. The 325i head, the 885, is also good and flows a little better, but you need psitons too. **Regardless of your piston head combo, use your eta rods too.** They're shorter and will reduce or eliminate piston work to clear the head.
Though finding a set of good or new pistons can be tough, but it runs so much smoother with fresh ones in there. They'll cost little or no power if they're worn, but m20's tend to collapse the skirts, causing vibration and eventually piston slap. If you can find a set, jump on them. Also make sure the block is good for the new set. If the bores are worn you'll need to punch them out and use oversize pistons. If its not too bad, a hone will do.
The 325i cam is great for around town driving, but with peak torque at ~4750 rpm, it doesnt rev quite as well as a euro 323 cam or something aftermarket will. Its not bad, but if you want peak pull over 5k, find a euro 323i cam, with 264 degree duration as opposed to the 325i's 256, and you'll be happy. You wont want to pull it apart again for a hotter cam after all is said and done.
I used my stock eta crankshaft, which is cast. Some say thats a bad idea and it'll break or twist over 6200 or something like that. I'm sure these stories arent entirely unfounded, but mine has gone as high as 6600 on multiple occasions and its just fine. Unless you have a cam that'll pull that high, theres no need. If you can find a good diesel crank, use it and be happy, but its not necessary.
For fuel injection, the only real choice is to find a wrecked 325i and pillage it. You'll need everything, and even then you'll have to fabricate some things if its going in an e28. I dont wanna go over everything I did to make it work in mine right now, but its rather intense. The gains are real, it runs smoother, runs harder and is better on gas when you keep off it. Its not easy, but its worth it. Dont bother trying to find a custom chip. You wont. Even if you shell out and have one made it wont come close to 1.1 or 1.3.
The 535 injectors help power up top a little, the 3 bar fpr helps a little and the 535 afm helps a little. I did all my work at 6000 feet, so denser air nearer to sea level may require more fuel, so your personal results may vary. If you wanna be safe, just go for a set of 535 injectors and a 3 bar fpr and you'll be set. The m30 afm is a dubious upgrade. Alpina's 2.7i used the m20 afm, and it had 210 horsepower. Not necessary in my opinion. Took me a lot of time and tuning to get it right. Chances are you'll lose power on that one. No good.
The 325i TB and manifold are necessary to compliment the cam and form up the powerband. No need for a bored TB, its large as it is. Same goes for the manifold, lots of money to port it for little gains. Stock bolt on works fine.
Headers are good for the m20. Depending on how much you wanna spend, you have two choices. Short headers will work best way up high, over 6000 rpm. Longer headers will kick in sooner but help less up top. The shorty headers in conjunction with my m30 afm and bigger injectors might be why my 2.7 revs like it does. You can feel the torque falling off, but ots not as drastic as 325i dyno charts show. Theres no real shift point. Whenever works. I'll dyno it when I have time, then we'll see if its anything more than a placebo effect. Doesnt feel like it, but I've been wrong before.
Lastly, you need a shorter diff to top it off. You might not know it, but you moved the powerband up so you could gear it lower and still go. A shorter diff will multiply the torque more and you'll go quite a bit faster. In mine, for the moment, I have a 3.46 open diff. Since I only slightly increased the torque output over the eta, at bets the speedo needle swings only a little faster. But, by the nature of the project, the powerband is also wider and the power delivery is better, so all together, it goes noticeably faster. The last step to fulfillment is indeed a diff. Basic math there. Hope all this helps somebody. Good luck with your m20's!
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