Humboldtgrin

Just killing time think about an idea. So I know many many men have stroked their 8v turbo to a 2.8L. But how many have built a 2.8L 16v turbo engine using a 2.5 944S head on a 2.5 block? I was thinking about the 2.5L 951 block w/928 S3 cylinder head turbo project I have planned and as I started up my 944S today I was thinking if anyone has stroked one out and added a turbocharger. The 928 S3 (from 85-86 928 "S3"USA cars with 32v V8's) head on the 2.5 block has higher intake runner velocity then using a 944S head on the 2.5L block due to the smaller intake runner size and valves on the 928 S3 head, which isn't a bad thing to mix up the air. So if the 944S head flows 10% more then the 928S3 head, would the intake velocity be close to he same between the two different displacements designs? The added dispalacment is about the same for the amount of cylinder head flow. I'm thinking the 2.8L with 944S head would have 2% more intake velocity then the S3 head on a 2.5. What do you all think? Added ideas would be things like I couldn't see the 2.8L 944S head being a non interference like a 2.5L S3 head design can be, or could it be made a non interference engine? Doesn't seem like much piston would be left to use on the 2.8L engine to make it a non interference design. But I bet the 2.8 16v turbo would put down some serious power. Would need to wet sleeve the block at that power I would think. Or fill the block half way with that concrete block filler stuff to match the 3.0L blocks water jacket depth (the water jackets are much deeper on the 100mm 2.5 block then the 104mm 3.0L blocks, which means room for reinforcement). I wonder if the velocity would be the same for a 968 head on a 3.0L turbo? If all three engines had similar intake velocity's and I built the 2.5 S3 engine could I see a matching drop in power that would equal the displacement and head flow increase of the other two bigger displacement engines? Would the "S" cam work better for the 2.5L, and the S2 cams in the 2.8L? Because we all know the 968 cams stay in the 968 head for that extra power. Anyways if your not doing much it's something to think about.

V2Rocket

Have heard of 2.8L 16v over the years but generally "whats the point" if there was a factory 3.0 version..

The intake ports and combustion chambers are identical S vs S2 so that pretty much addresses your air velocity question.

Humboldtgrin

Velocity would be different on the S2 head 3.0 vs S head 2.8. And the 968 head is like a ported S/S2 head right? Wouldn't the velocity be close to the same on a S3 head on a 2.5, a 944 S head on a 2.8 stroker and a 968 head on a 3.0? I would think the S2 head on the 3.0 would be higher velocity then all of them and a S head on a 2.5 would be the slowest velocity especially if the S and S2 heads have identical ports and valves.

V2Rocket

No way to know just by guessing from valve/port size.
I spend a lot of time digging through the 928 forum as these guys have done a ton of research and work regarding their heads (which as you know are very close to 944 16v).

The S port is really too big for a 2.5L NA engine. It's still kind of big for a 3.0L NA. The 968 ports are just ridiculous. I think that Porsche oversized them in an attempt to scrape a little more power out of the restricted AFM intake tract of the S/S2, don't know their reasoning on the MAF-968.

In a turbo you take all the flow you can get so the port size doesn't matter a whole lot once boost arrives.

I really like the S3 head and have thought about (but likely will never try it) putting it on a 3.0+ bottom end and running NA to see the torque through the smaller ports and valves, and it should still flow plenty for high RPM power. The S3 intake port is 45mm diameter and from the "authorities" is said to flow only about 10% less than the S4 (roughly 944S) head.

MorfeuZ

We are building 2.8 16v Turbo stroker motor with closed deck with sleeves. Using 944S head with dual camgears, custom pistons and pauter rods with M. Mount bearing mod. You can check blog (sorry, only finnish language) & pictures from here:
https://silverbullet951.com/

Adonay

Wow great Build . No expense spared .

dlr944

morfeuz can you tell us more about your build on another thread or point me there.. I need to were you got those led gauge lights. Thanks

MorfeuZ

I do not have build threat (yet) in Rennlist, but leds are from ebay and you can find them from here.

MooreBoost

333pg333

Would be interesting to hear about your build. Never seen that sort of sleeving with a deckplate incorporated.
Looks sort of like MiD sleeves but with the added solid deck. Interesting. Any reason why you started with the S motor though?