TeufelHei

The continuing quest for an angle on power in the early 928:

I've been thinking about the coating process and the "special" process used by Porsche to get the silicon to surface in the bore. What about Nikasil, and even more, how big is too big. Early model afficionados please answer.

It would be really nice to be able to bore out to say, 4.00 inches (vis 95mm) get my point? I'd settle for less, but I wonder how much is there to work with (i've never pulled apart my engine).

Bottom line, I'd like to get more power and compression is a factor (looking for 10.5-11.0:1). If I could go to 100mm in the bore and use 944 pistons, that would make my freakin' day!

I'd like to keep my beautiful 16v motor where it belongs. Frankenstien's monster my baby is not! But she can be FA Porsche's monster any day of the week!

Tony

Jan....Brandan...care to step in?

all in fun guys

John..

You could probably go to 97 mm no problem, but the gains would not be that significant....or wait for an affordable method of forced induction for the L-jet car to arrive...

Drop me a line if you want specifics on cost of the process and/ or pictures.

I'm done bickering back and forth about this sleeving vs. Nikasil debate. I stand by the fact that I have a running and functioning automobile.

TeufelHei

Yeah, I figured 97mm wouldn't be a stretch. John, how is the Bastard these days? Did you get her put back together yet. I remember you had the heads off and were working out some ECM issues last time we talked. If I ever get enough dinero to force some air-o then I'd still like to go with newer (better) pistons for the job. Is there actually a problem using "normal" (ie non Voodo magic) pistons for regular use? It's not looking good for replacement parts, 95mm isn't exactly the most common size out there.

Jim bailey - 928 International

Tim you simply need a 85-86 5 liter short block ...100 mm pistons and higher compression .. eyebrow the piston for the two valve head and transfer all your engine parts .....heads cams etc. There are several such "hybrid" 2 valve engines with different combinations of USA and Euro parts . Your current block PROBABLY has enough material in the cylinders to bore to 100 MM but the 85-86 is a better way to get there and would allow you to over bore to 104.5 as well ....

TeufelHei

Hey Jim, glad to get your input.

Do 944 Pistons work out of the box? Or do you have to modify them too? I'd like to have the parts source be a bit more diverse if possible.

TeufelHei

Hmmmm. 104.5mm. Just like 4.10 (and small change). Timmy like!

Rough estimate= 5.41L of wahooo!

Add O2 and hydrocarbon of choice (personal favorite is Chevron Techron 93) in proper measure and that's a whole lot of go....for plenty of dough.

BC

...If your willing to pull the engine, then you may as well spend the money you have on a nice short block like Jim says. Hell, it may be cheaper for you then either sleeving or nikasil.

If you boosting, then you need to at least think about a reseal, but this statement has little to do with your question.

The 4.5L engines DO have less OD on the bore tower then the 5.0s do, so you have less to work with.

BUT, you could slap a SC on there with your COOL 8.5 or 9.0 compression ratio and GO.

TeufelHei

Slap a Super on there huh? I wish I could, this whole thing would be over and I'd be doing doughnuts down the Boulevard. By the way, how well do stock 928 pistons hold up under boost? I remember reading that they are of a cast and coated design, am I mistaken? One would think forged pistons would be the way to go.

I'm going to search for other power adder methods. I've done some calculations and more or less set the goal at "yawwn" about 390 RWHP. That'll probably come from a 100HP Direct port NO2 shot. Otherwise, 300 RWHP would do me just fine.

That damn speedometer peg has been taunting me for far too long! Now if I can just get the dash working right again...

TeufelHei

Also, I like John's twin turbo. I wish I could see it in person, very motivating. Anyone know who could make the manifolds for something like that? I had a line on a cutomer-aided mail order custom manifold shop once, but it sounded kinda shady.

ViribusUnits

Why can't you?

There are ways to get around the L-jet.

Buy a head unit, a air to water intercooler, and get to plumbing. It can't be that hard. You'll have to find a way to build a bracket to hold the head unit, but that can't be a big deal. Maybe weld a bracket to the fan mount?

You'll need eighter a higher pressure fuel regulator, or a bigger set of injectors. Or both. Then mount that AFM ahead of the blower, and tighen up that main string behind the black plastic cover untill the mixture is all right, and you should be good to go.

I've heard that the 928's AFM will make 300 hp easily enough. See how far that AFM will go.

That or you could use an FMU, and have it start adding fuel the moment you get into boost. This is simpler, easyer, and just as effective, if not as ellegent.

Apperently the 928's cast pistions will hanndle the boost all right. John's pistions hannded 10 psig of intercooled boost for a decade or two. Some of the S4 guys have pushed their pistions pretty far. Just stay away from detonation, and you should be all right.

If youw ere in the Houston area, I'd love to help you. Or you can donate some cash to me, and we'll use my shark as a test bed. ;-)

If you wanted to you could build a real boost monster. Get a 5l block, get a deck plate fitted, and get orings fitted, Nikal it, get some forged pistions, bolt your head to it. Build up a supercharger, or turbo, add the aftercooler, and then run the boost real high, like 20-26 psi.

Tony

I plan on finding out...some already are. So far so good IMHO.

Cast has its limits, no doubt. Even more so with my machined cast, but detonation will KILL anything, FORGED...CAST...whatever.

BC

The issue here is that your compression is so low that you are PRIME for blowing that carf with some form of boost.

My point was the money spent either direction may be equal.

TeufelHei

I agree absolutely, my preferred method would be twin Turbochargers and a conversion to MAF plus the cams appropriate for the job. It's about the best way to double the power that I know. Parts alone would be in the $7-10K neighborhood. Of course, using a 944 Turbo manifold on the right side and a single Turbocharger of sufficient capacity would work well, only the problem with imbalanced exhaust flow could be an issue. That cuts cost down somewhat.

I'll knwo more when I pull the engine. I intend to inspect it thouroughly for the first time in a long time and see what I've got. If it's good, then I'll seal it all back up and most likely find some sort of pump to stuff air into it. If not, then I've got a few other options (5.0L hybrid, S4 Swap, either one with forced air/NO2).

I'm actually quite excited about the possibility of actually using some of the stuff that I'm learning here at UA, who knew you could actually use Calculus right? Admittedly, I'm putting the cart before the horse buy talking heavy duty power before I even know what I've got to deal with. However, I really do need the advice and anyones experience can help me out here.

ViribusUnits

No kidding on the Cal.

Who thought you could ever use defferential equations on stuff!

Or for that matter linear algebra!