destroking the L28?

Question

I have heard that the L28 has "harmonic problems" at 7250 rpm. By the same token, I also know that the inline six is inherently balanced. Would it be possible to use a smaller stroke to increase the available RPM range? I see that the L28 has a 79mm stroke, whereas it's 74mm in the L24. For bore, there's (as far as I can tell) only a 1mm larger bore on the L28 motor than on the L24.

Would it be possible to reduce the stroke substantially, while increasing the bore substantially (either with sleeves, or just trusting the solid block the L28 is) to maintain near parity in displacement, while at the same time being much more suited to turbocharged performance (boost comes on at 3500? no problem! pull to

8500!).

Thanks alex

Steve T · Accepted Answer

The LENGTH and design of the crankshaft is the main problem, not the stroke.

The problem is trying to get the non-crossflow head to flow enough air to make any power up there. Even with a turbo, you'll need a race ported head (~$2500-3500+) to make power at 8500, plus the timing chain and valve train become issues there as well. Include a better intake and exhaust manifold, stand alone EFI etc etc and to make an 8500RPM turbo L engine would be upwards of $20K by the time you were done.

The best combination for power is to INCREASE the stroke (using the LD crank), limit the RPM to 7500MAX and bore it to a 3.0 or 3.1L (no sleeves needed to go 3mm overbore.) I think you are maybe used to a honda etc where you HAVE to rev it to 8500 to make any power, these aren't like that.

Like the old saying goes, there is no replacement for displacement, it's basically free power unless you are working under rules that limit it. That's why I'm just finishing up a 3.1L for my 280Z, should be close to

300HP with no turbo. I've seen turbo 3.1L engines make close to 450HP in street trim and over 600HP running race gas.

Peter Hill · Answer

If you must have 2.4L be far better to make an RB24DET than mess with an old L. Even easier would be just drop in a RB20DET, RB25DET or if cash allows a RB26DETT. Or if you are really nuts an RB30DET (OS Giken) or RB28DET (JUN).

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you can see it's a much more mix and match engine - even Nissan did hybrids. As it's still the top dog in terms of Nissan engines lots of kit is still available.

When you have sorted a nice 6 drop it in a hatchback S13. The modern multilink rear suspension will be a revelation to your old IRS.

destroking the L28?

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