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Technical_   Engine_  M20 E to I 2.8 Liter Engine Conversion_  Final Thoughts, Finishing Touches

M20 E to I 2.8 Liter Engine Conversion
Fred Kim

IX.   Final Thoughts, Finishing Touches

6.)  Final Thoughts/Finishing Touches

After the initial 1000 mile break-in period, I am happy to report that the 328i has been running great without any major problems. With the stock 2.93:1 differential, the car feels slightly faster than my old chipped eta off the line, but once it gets up to about 2500 it pulls much harder than a chipped 325is (I had my friend's car as a reference). But I've never taken the car past 5800 RPM yet since things started to get really loud at that point. Just for fun, I used a G-Tech to test the 0-60 on my car. With one passenger, clutch slipped at 2000 RPM, and shifts at somewhere around 5800, I clocked a 6.65 second time.

About a month or two after the conversion, I installed a 3.73 limited slip differential from a 325is, which is a direct bolt-on with no modifications required. The difference was night and day and the car accelerates like a bat out of hell with this gearing. Initially, it seemed to rev too high on the freeway but I got used to it quickly, especially with the huge boost in acceleration. In hindsight, the conversion almost seems wasted with the 2.93 diff so I'm very glad I upgraded. Now, after the diff swap the end result is almost officially a 325i that has high compression pistons and longer stroke.

I also ordered a custom "M20 B28" plate to match the car since I thought it would be a nice addition. You can also add a "328i" badge from an E36 or the "2.8i" badge from the Z3 for a finishing touch.

The cost of the conversion and the amount of additional parts needed was much more than what I originally planned. The initial calculation was around $2,500 since all the labor (except the machine work) was done by myself and my co-workers, but I ended up spending almost $1,000 more on miscellaneous parts and on things that I found out were bad (like the starter). I also consider myself pretty fortunate that several important issues, such as the incorrect pistons, were resolved. However, unlike what many sources on the Internet describe, things do not just bolt right in, and I couldn't find anyone who could accurately describe what parts from an "e" could remain and what parts from an "i" had to be used. In the end, there were so many "i" parts needed that using a 325i as a starting point would have been easier; in fact, the only eta-specific parts that I still used were the valve cover, connecting rods, and airbox.

But I can say that it was a great learning experience and can now boast that I built that engine with my own hands. But I couldn't have done it without the assistance of Paul Ahumada and Simon Juhasz of Alpine Motorworks and my friend Can Chang, all of whom donated countless hours of their lives for this project (though I later regretted it: read below). Terry TInney of Performance Motors also did a fantastic job with the short block and cylinder head and I would highly recommend him to anyone in the Bay Area who needs machine work. Special thanks also goes out to Marvin Ancheta, Barry Robinson, Rich Vijeh, Scott Miller, Eric Lukas, Dave Adams, Tom Walrod, Eric Mickelson, Daniel from SSF, and to everyone else who helped me out with information, parts, and support!

Paul Ahumada/Alpine Motorworks (CLOSED FOR BUSINESS PERMANENTLY)
1394 North 4th Street
San Jose, CA 95112
(408) 392-0751

Terry Tinney/Performance Motors
2135 South Vasco Road, Unit K
Livermore, CA 94550
(925) 447-1820

Top End Performance
7452 Varna Ave
North Hollywood, CA 91605
(818) 764-1901

World Wide Parts and Accessories Corp (Worldpac) - wholesale only
1949 Lundy Avenue
San Jose, CA 95131

SSF Imported Auto Parts - wholesale only
466 Forbes Ave
South San Francisco, CA 94080
(800) 632-2743

12.)  Problems, problems, problems

Well, it was bound to happen one day. All of a sudden about two months after the conversion, without any warning whatsoever my 2.8i lost a lot of power. It felt like my old eta engine (even with the 3.73 rear gear) so I asked Paul if he knew what the problem was. He drove the car and happily announced that everything was perfectly fine and that I was just imagining things. I obviously disagreed, but nobody else seemed to believe me so I began to think it was just me.

But I dynoed my car on an E30 dyno day and the numbers proved me right: Much to my embarrassment, it pulled a disappointing 144.1 rear wheel horsepower and 162.7 rear wheel torque (on a Dynojet dynamometer), which is only slightly better than a stock E30 325i. The car also ran lean across the board. I was furious and showed Paul the dyno sheet, but he had no clue how to read it (not surprising, considering he never even graduated high school) and again, out of sheer stupidity said that my car ran great.

I started to test various parts and eventually found a very weak spark. If I pulled one ignition wire while the car was running, there was no change. If I pulled two wires out, it started to barely misfire. Only when I pulled out 3 spark plug wires did the car shudder and stammer, so I changed the coil and ignition wires. This made a noticeable improvement, but it still wasn't anywhere as fast as it once was.

Since the car ran lean at all RPMs, I ordered an adjustable fuel pressure regulator from Bavarian Autosport and installed it right away. (I should also add that this is a very high quality unit and mounts in the stock location, much better than the one BMP Design buys from Hong Kong and sells for a godawful $300.) However, it didn't come with a gauge so I hooked up a fuel pressure tester to measure the flow. I eventually ended up setting it at 3.8 bar, which is 0.8 bar higher than stock. Again, this made a noticeable difference but my car still wasn't 100%.

By this time, I wanted another dyno to see where the car was at. I went back to the same shop (Dynospot Racing in San Jose, California) and gained almost 10 horsepower and 10 lb-ft of torque. Better, but still bad in my book.

Since I was at my wit's end (and Paul still insisting that he was right), I took the car to the famed Bill Arnold Independent Repair in San Rafael, California. He found a loose timing belt, seven backwards installed rocker arm eccentrics, a misadjusted TPS sensor, a completely clogged fuel filter (my fault since sometimes I run the car to nearly empty), and a dirty air filter. Afterwards, the car felt better but still wasn't 100%. Bill Arnold (who is a very nice guy, I should add) recommended a better flowing 2-in/2-out catalytic converter and a custom 2.7 or 2.8 chip. Ace BMW mechanic Paul Ahumada said that the loose timing belt and backwards eccentrics were my fault because "I drive my car too hard." What a moron.

A few months later, I did end up purchasing an Alpina 2.7i chip (originally used in their B3) from Chris Dunagan along with a new ECU, and that made a huuuuge difference. I haven't dynoed it yet (or changed the cat), but I'd say that it's about 90% of where it should be. Thanks Chris, you da man!

So why did I lose all that power all of a sudden? I still don't know. (Perhaps Paul knows since he's the self-proclaimed top BMW mechanic in the country.) My guess is that a lot of parts went bad at the same time, plus my ECU could've been faulty. Who knows for sure. But I do plan to dyno my car soon, so stay tuned.

13.)  3.0i meets 2.8i

My friend Dave Adams also built a 3.0 liter M20 stroker at the exact same time I was building my 2.8. We finished our cars at the same time and had a little meet to check out each other's cars. Dave's 330iC was much more modified than mine (aside from the larger displacement, he also put on a Schrick 272 cam, oversize valves, ported intake manifold and throttle body, and MSDS headers, in addition to the mods he already has). It did pull harder than mine at higher RPM, so if you see him in your rearview mirror, move over!

For more info on Dave's 330iC, check out his website at Unfortunately, as of October 2003 his 330iC was rear-ended by an inattentive driver on the Bay Bridge and was totaled out by the insurance. RIP.


Table of Contents

1.) FAQ

2.) Parts List/Price Guide

3.) Short Block

4.) Cylinder Head/Intake Manifold/Fuel Injection

5.) Engine Removal

6.) Engine Install/Wiring Harness

7.) Cooling/Belts

8.) Tachometer Wiring

9.) Final Thoughts

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