Difference in 280zx dished pistons and turbo pistons

[defrag010]

I am doing a rebuild on my '80 280zx, and it has a dished piston L28E in it now. I have a P90 head for it, and I was going to order some new turbo pistons for it.. except everything I find says the turbo pistons will yield the same compression as the n/a dished pistons.

 

Are the turbo pistons more rigid with wider ringland separation, or are these two pistons essentially the same thing?

 

They will yield the same exact compression, so if I re-use the stock n/a dish pistons, how much power can I expect the motor to handle vs. getting new std. bore turbo pistons?

[defrag010]

almost 100 views, and no one knows?

[roger.svoboda]

Not a hundred percent sure on this but I've been told by some very reliable folks that the pistons in n/a engines are flat top and they dished the pistons on the turbos to reduce compression ratio to take the turbo boost. The block and head are the same dimension. Even tho there are differences in the p90 and p72 heads the combustion chamber is supposed to have the same volume just depends on the pistons installed in the engine.

[nismopick]

Not a hundred percent sure on this but I've been told by some very reliable folks that the pistons in n/a engines are flat top and they dished the pistons on the turbos to reduce compression ratio to take the turbo boost. The block and head are the same dimension. Even tho there are differences in the p90 and p72 heads the combustion chamber is supposed to have the same volume just depends on the pistons installed in the engine.

 

He's talking about the early L28 dished pistons used for emissions purposes. They should be the same, tho the turbo pistons have P90 stamped in the top (kinda hard to see in this pic, but the stamp is on the right side of each piston):

 

[defrag010]

thanks.. I know that the n/a dished pistons have larger rings, but could the turbo dished pistons have a larger distance between the crown and first ringland?

[zeiss150]

suposedly the turbo pistons have slightly thicker ring lands. zx N/A L28e engines came with flat top pistons only (provided it is an F54 block with a P79 head).

 

If you have one of those 1979 N/A zx's with an N42 block and an N47 head then maybe you might have dished pistons, that engine combo will give you 8.5:1 CR but is more prone to detonation than the N/A F54 P79 combo the P79 head has a better design (as does the P90) and can be turbo'd easily

 

the 8.5:1 CR is a great way to go for a turbo design as long as you don't plan on running huge boost. With the higer CR than a stock turbo (7.4:1) you get a quick off boost engine and once the turbo kicks in, watch out.

 

If you are looking to make a monster turbo engine go with the turbo pistons and stock 7.4 CR

 

I think there was a thread on this side about the ring land thicknes of turbo pistons... one of the guys mic'd them and compaired the three difference pistons. I haven't had much luck with the search function on this site but you could give it a try and see what you come up with. I do sort of remember reading in one of my Z books something about all the L28 pistons being the same ... even the turbo ones... but ... the mic #'s hold the truth.

 

Good luck!

[1 fast z]

Ok, heres the differences:

 

 

NA 75-80 Pistons have a 10cc dish, with both compression rings being 2mm thick.

 

81-83 ALL pistons have 1.5mm top compression ring, and 2mm second ring.

 

81-83 pistons, move the ring lands down about 1.5mm deeper in the bore compared to the earlier pistons.

 

Compression ratios with ALL dish pistons, NA, and turbo are the same.