destroking the L28?

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avriette@gmail.com - 18 Jun 2006 00:35 GMT

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

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Steve T - 19 Jun 2006 04:25 GMT

> 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.

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

> 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
[quoted text clipped - 7 lines]
> turbocharged performance (boost comes on at 3500? no problem! pull to
> 8500!).

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.

Signature

Steve

http://www.atlantaracing.com

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Peter Hill - 19 Jun 2006 17:39 GMT

>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.
[quoted text clipped - 12 lines]
>Thanks
>alex

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).
http://en.wikipedia.org/wiki/Nissan_RB_engine
As 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.
--
Peter Hill
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Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

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