n12 heads theory

[et_rider]

Here you go:

33M
---E16i head
---combustion chamber volume: approx 24.5cc (poly-spherical)
---valve dia (I/E): 37/30
---low-swirl intake ports

31M
---E16s head
---combustion chamber volume: approx 24.5cc (poly-spherical)
---valve dia (I/E): 37/30
---high-swirl intake ports

15M
---E15ET turbo (or FI) head
---combustion chamber volume: approx 17.9cc (semi-spherical)
---valve dia (I/E): 37/31
---low-swirl intake ports

11M
---E15s head
---combustion chamber volume: approx 18.5cc (semi-spherical)
---valve dia (I/E): 37/30
---high-swirl intake ports

52A
---E15 head
---combustion chamber volume: approx 21cc (semi-spherical)
---valve dia (I/E): 37/30
---high-swirl intake ports

L8tr
E

you see now im confused i hate numbers i like to look and see lol guess thats what you get being dislexic now on topic in theory wouldnt a 11m head be batter as it has high swirl ports does some one myne explining this to me please your help would be very greatfull

ta matt aka et rider

[dexi_styles]

Dyslexic are Teople Poo!!!

[Callumgw]

I'm guessing a little, but I think it might be to do with Carbie versus injected. The high swirl is used on the "S" and the low swirl "i". Swirl is also used to get a good mix of the air/fuel charge. So maybe the injected one doesn't need this mixing and the swirling slows the charge entry (detrimental)

C

[Timmzy]

Plus in a turbo setup, as soon as that valve open you get 8PSI (or whatever) of air/fuel pressure blasted in there.

That is going to make it swirl alright.

The fuel injected (non-turbo) heads would be interesting to look at. But the exhaust valves are 1mm diameter smaller, which is quite a penalty to pay.

Regards,
Darren.

[et_rider]

well i got a standered head for the last hea relacment it was cheap lol now the only thing i found :

Pros:
response down low was good
saved fuel lol

cons:
top end there wasnt much there felt like it was struglling witch would explain the smaller valves
mid rang wasnt that good either

so im not to shore the head i was had 52A on it mmmm i wonder if your just chasing higher compresion maby you could go with the 52a and if your just after a nice good drive lol go normal


and dexi_styles spokane eikl a true di s lexik lol

[TurboZ.Dude]

So the 1-mm difference in exhaust valve size does that much of a difference? Wouldn't the high swirl instead of low swirl cause more than the valve size? It's hard to believe that the valve size itself would do the difference in your case as you have high swirl instead of low swirl.

Would a 1-mm change in exhaust valve size actually do much of a difference if the ports would be the same size and have the same swirl?

JP

[Panda_ET]

head design gets less important when working with boosted engines. The theory maybe more important whenplaying with Naturally aspirated engines but boosted engines everything is forced in so as long as there is a hole it will work

[photoglossy]

But ya cant beat a big clear port with boost

[tassuperkart]

It also should be known, altho not really that earth shattering, that the 15M head on Aus built ET's is the much sought after Nismo Hi-Po head available once thru NissanMotorsport.

The Nismo head is fundamentally the same as the stock 15M fitted to various Cherries/Langleys/Milaonos/etc with e15et turbo-efi engines.

However, the Nismo head cast with slightly thicker aluminium castings here and there to supposedly cope with the higher head temps experienced in a race turbo engine.

The rest of the world is not blessed! You have to pay for the priviledge!

Im not entirely sure as to exactly how they are positively identified. This seems to be a bit of a mystery.
What is known is that Nissan in Australia in their infinite wisdom, specced the Nismo head along with the rear disk brake setups for Aussie ET's.

They (Aus 15m's/Nismo15m's) are greatly prized by yank e15 atmo tuners.

L8tr
E

[photoglossy]

And to think i have about 5 of them...HAHA!

[tassuperkart]

Heheheh yer, you have the stock 15m M8, the one with the thinner castings. We in Aus have the thicker Nismo sport items of which I have about 5 of LMAO. Sucker.... bite me!!!!!!!!!!!

L8tr
E

[photoglossy]

Got an ET one too... Its actually on age's car tho

If they were really any different surely they would have made it a different casting number... Bet ya it was just all hype...

[tassuperkart]

Heheheheh well... you have, or had your grubby little snatch-scratchers on at least one eh!
I seriously dont think anybody is missing out on anything! 15M FTW!
L8tr
E

[tassuperkart]

If they were really any different surely they would have made it a different casting number... Bet ya it was just all hype...

I agree M8. Might very well be. However, the Yanks discuss it at length and one of them had about three of them still in Nismo boxes. Its sposed to be demonstrable... Im sure not going to dice up a head just to see some thicker aluminium!!!!

Thats the story anyway.

As you know, some very strange things go on between design, pattern-making and eventual casting.

There is a Holden 308 (5 litre) head cast from back in the Torana days which was sneaked thru the production process and so outperforms the other castings its almost a joke.
Its the "trick" head which can still be found on rubbish tips and wreckers today that was used on the L34 and later A9-X hatchback Toranas of the mid /70's, and probably later Commonwhores that crucified their much larger displacement Ford competition for so long.
For those poor souls who had other casting heads, no amount of work could bring them up to these "special" heads level such was the improvement!!!

There is NO special markings or numbers to identify them but a trained eye can pick them out in a pile of ordinary ones!!!

Way it is!!

L8tr
E

[Panda_ET]

dont bring boring push rod stories here old man ..now get back in your box