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I'm planning on putting a 280zx turbo engine with sds into my 240z this upcomming summer (yeah yeah that was last year's goal too), but I have a few things I dont like about the engine. first of all, the compression is REALLY low, at 7.4:1, i dont even see how the engine could move the car off boost. Second, I love the way my 2.4liter revs, and the higher redline of 7,000. Now Im thinking, I'll have to rebuild this turbo motor anyway, so why not throw the L24 rods and crank with some flat top l28 pistons and make a nice 8:1 compression destroked 2.6 liter motor. The rod/stroke ratio of 1.8:1 is much nicer than the stock 2.8 liter's at 1.63:1, making for longer dwell at TDC, and loading less angular stress on the bearings. Now I'd have a faster revving, higher redline, less stressed motor, but would all that be worth the .2 liters of displacement I'd be giving up. I like the numbers of my destroked turbo, but the displacement may not be worth giving up. What do all you number crunchers think?
 

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Ya, that all sounds good on paper but with 7.4-1 comp you can run alot more boost. You don't loose that much torque keeping it that low. Another reason to leave it a 2.8. You'll have more torque. Both engines can easily take 7500 rpm ,I know mine has no problem pulling HARD to 7500. It's the long crank that limits rpm not the stroke on these. The cam will determine where your peak hp is not the stroke. Don't let the factory tach redline worry you. Also if you leave it stock you won't have alot of time and money in it. I'm running a stock turbo block(cast pistons) L28 w/P90 head port matched and unshrouded with a T4 and 20 psi. It has more power than two 24.5/10-15 slicks can take in third gear going straight with a welded diff. One more thing the stock turbo pistons have a much thicker top ring land compared to all the others. I've broke two N/A pistons, one L26 and one L28 dished non turbo but never a L28 turbo piston. If you go with a cast piston other than the factory turbo piston, you should take that into consideration unless you are going with forged. That extra little bit does make a difference on the cast parts.

PS. More displacement means more torque and more boost means more power.
 

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point taken

no replacement for displacement I guess. Hey, maybe I'll run the stock turbo engine and when it's time to rebuild (when I blow it up), I'll build the destroked turbo. Still, it sounds so nice on paper! That piston thing would be a problem, Ive heard people say otherwise, but I could see how it could be. Maybe it's possible to run the L28 crank with L24 rods and .40 overbore with (early non-floating) turbo VG pistons? anyone have the specs for the VG pisons as in pin height? I simply want a better than 1.63:1 rod/stroke ratio
 

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Another consiteration..

is that these engines were not built to rev like a honda. The port angles are just too low, and when a person really wants to get the rpm's way up there, they raise the roof of the port and fill the bottom to get a straighter shot in and out of the cylinder. You may be better off aiming for more tourq at a lower rpm. But to each their own, if you like it, go for it!

Dylan
 

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What about 8500?

That's the shift point of the 76 280 2+2 we built. But it's N/A and have to go there.
Keep this in mind:
even at 7500, you should have forged pistons. Keeping it below 7000, you can get away with literal murder and still run well, especially with a turbo, as the alloys are much stronger under compression than tension. THe loads in tension escalate astronomically with rpms increase, but you really have to boost it up to make the compression loadings of the engine anywhere near the failure point of the materials used. Even with cast pistons!
Point two: if you increase the RPM limit, while ultimate HP may increas incrementally, you most likely will have to size the turbo for the flow required at those rpms, makeing the lower end much more unusalbe. This is the advantage of low-rpm high-boost applications. Sure, 7.4 is soggy on the bottom end, but with proper application of cam timing and porting, the engine will make just as much power at 5500 to 6500 on inexpensive cast pistons and be much more streetable, than an engine makeing much more HP at 7000+

Lastly: the Electromotive 280ZXT in 1983 made 580 advertised crank HP at 7500 rpm with stone-age electronics, and could do over 200MPH on the back straight at Riverside. The stock rods are good to about 600HP...
Kinda makes the de-stroking question academic, don't you think? My suggestion would be to INCREASE the stroke with the LD28 crank, raising the compression, and go from there with more boost!
 
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