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323i motor build -- how far can I go while retaining K-jet?

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323i motor build -- how far can I go while retaining K-jet?

Postby inkatouring » Wed Sep 13, 2017 6:52 am

I'm rebuilding the motor in my c1 2.3, which I don't believe is the original actual Alpina motor. I plan on using a turbo diesel crank and schrick 288. I can increase displacement easily up to 2.7 with that crank but want to maintain the bosch k-jet CIS to appear to be a stock e21 c1 2.3. Given that the bits that increase the displacement are hidden in the motor, I don't particularly care that it is stock inside.

To my question: how much displacement can I build into the motor and have it still run well with the stock k-jet/CIS?
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Re: 323i motor build -- how far can I go while retaining K-j

Postby e21Keith » Wed Sep 13, 2017 10:25 pm

I'd be interested to know more about your build as I have a kit of parts including the 324d crank and shrick 288. I'm not sure which rods and pistons I should be using, which block and head (I have most options in stock). I also plan to retain k-jet.
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Re: 323i motor build -- how far can I go while retaining K-j

Postby Wilmo » Wed Sep 13, 2017 10:51 pm

Just some random thoughts... Maybe that the ECU taking care of the injection can be the limiting factor, but when you implement a Megasquirt or Minisquirt, a programmable electronic fuel injection (EFI), that it is more likely to work.

Bertjeconti of this forum did it with his 2 liter M20 in his E12 and he got the theoretical power output of a standard E21 323i. It seems that with an EFI there are more HP to be found in any block using the standard injection hardware.

I just installed the electronic ignition part and the power of the spark is not comparable with the spark of a mechanical distribution, it scared the hell out of me. In combination with my Weber, starting has become much easier and since you can control the advance dependant of the engine load and rpm, knocking is much less likely to occur. I believe that already only at the ignition part of the story, there is a lot to win. When you put the EFI in control of the injection as well, together with a Lambda sensor, giving feed back of the fed mixture, yeah, I don't see a reason why your setup won't work.

When you think of the advanced camshaft and a different crankshaft, I would like to have more parameters to tune, hence the EFI. On a test bench it can be tuned to perfection.

But, yeah, I am not hindered of any knowledge here ;)
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Re: 323i motor build -- how far can I go while retaining K-j

Postby gerrit323 » Thu Sep 14, 2017 8:55 am

My hartge had 180hp with K jet .. 200hp should still be fine because that was what schnitzer was running with there turbo setup 323i

With the 2.7 cranck you have to use the m20b20 rods .. dont forget that most strokers are build out of a e30 eta block or an e30 m20b25 block.

Hou will have to increase the bore of the 2.3 block from 80 to 84mm and use the correct pistons out of the ETA block
Last edited by gerrit323 on Thu Sep 14, 2017 9:00 am, edited 1 time in total.
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Re: 323i motor build -- how far can I go while retaining K-j

Postby Duracel79 » Thu Sep 14, 2017 9:00 am

The K-jet system can be very versatile and cope with up to ~50bhp per injector depending on your setup.

I'd suggest getting one or both of these books and have a read up about it all.

https://www.amazon.com/Bosch-Fuel-Injec ... 0T81G5D9ZC

https://www.amazon.com/Modify-Bosch-Inj ... 0879385707

My dad did build a 2.7 back in the eighties and ran it on the original k-jet. The only mod to the fuel system was to adjust the WUP (control pressure) to allow more fuel. It ran 175bhp at the wheels and would still get over 30mpg on a long motorway run (75mph).

The 2.7 build was fairly basic:

ETA crank balanced with lightened 323 conrods, 9:1 ETA pistons.
Ported 200 casting head (std 323) with Schrick 282 cam
Tubular manifold and 2.25" ID single pipe system

The car finally came off the road with 279k miles with the engine still working but a bit smokey from piston ring wear.

There are many ways of building a 2.7 to achieve different results.

Hope this Helps

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Re: 323i motor build -- how far can I go while retaining K-j

Postby niske » Thu Sep 14, 2017 11:47 am

Maybe this can help you a little bit...
viewtopic.php?f=3&t=24779
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