scular

Folks, come on. I have now seen a few comments in this thread about special pistons, and all kinds of parts. It is possible to get these parts without having to refinance your house or have them custom made. If you are serious you can easily find a set of high performance pistons in summit racing. Who cares if the label says they are for a ford or chevy, all that matters is they fit and work. Many parts can be had this way, but some time needs to be invested to verify all dimmensions, this is not a project like bolting on a "cold air induction kit" onto a honda that you happened to find at your local walmart.

Also it is easy, if you are doing a full rebuild, to gain a few horsepower with the usual head work, porting, and polishing. 200hp is resonable out of a 944 2.5L na. The turbo worshippers, that somehow are the most vocal, don't know everything. The fact is for them to get over 300 hp reliably, their engines probably without boost are making around 200hp. Guess what, it takes more than boost, there is timing, fuel, and air. So now, the turbo motor has lower compression than a na... hmmm... that implies the engines without boost does not put out as much. So that means the na's can be tuned. Right?

eman930

I think a 2.5L engine could be build to 250-260hp with about $10,000 or so in it, It would all be upper RPM power. I have seen 1.8L Honda NA motors putting down 310HP on race gas with about $7,000 to $10,000 in the engine. Problem is with the P-car there isnt alot of aftermarket support and to many P-car guys think it cant be done and think that the 2.5L is at its max. Then you get the turbo guys telling you to go buy a turbo if you want a fast car, Hell why not buy a ferrari if you want a fast car and sell the turbo. The point is its always great to play and learn from the P-car. This is part of the reason I am built Project red blaze, Im hoping for about 200hp without nitrous and 250-275 with. I say go for it, build a 200-250hp engine just to show that the 2.5 can be built and that its not at its max. It all can be done, some one just has to try.

Jfrahm

Pistons for iron blocks or sleeved blocks are cheap, yes. Pistons for our Alusil bores are not cheap. they need a plating to prevent skirt wear. If you can find an easy way to solve that problem Chevy pistons can be used in the 944 motor. They would still be custom pistons or at least require custom rods to sort out the pin location.

The 300HP turbo motors are probably under 150HP without the turbo. Most of them are running more than 1 bar of boost, in other words they are putting more than 2x the air and fuel in that they would without the turbo. With the low CR I expect they are not much over 115-120HP off the boost.

To determine how much HP you can make with an NA motor, just consider how much fuel and air has to get into the combustion chamber. Consider how difficult it would be to get all that in there with the piston to valve area you have, and the number of crank degrees to do it in. Making lots of NA power is hard with 2v heads and streetable port diameters and cam profiles. It's a lot easier with 4v heads and a variable geometry intake manifold.

-Joel.

meanmaroon951

Someone said nawwzz.. .l0l but i think you shoudl gut your cat turn the fuel quality switch a few notches and run maybe 40% nitromethane , by the way that one engine with the narrow powerband wouldnt make a bad drag racer (going to hide now)

eman930

Already running alot of aftermarker parts including a chip, adjusting the Fuel quality switch wont gain HP. Why is it when some one says nitrous people make fun of the word or think its ricey. Nitrous is quick and easy and cheaper then a SC or turbo kit. From what I hear the NA does well with it.

P.S I said nitrous not NOS

Danno

I had a NOS 50-shot ProFogger kit left over from my Supra. What was the first thing I did when I got my 951? Yes, that's right, installed the NOS! While it made the Dr.Jekyl & Mr.Hyde personality of the 951 even worse (off-boost -> on-boost), it would work great in a 944NA. Only catch is nitrous is a fairly expensive upgrade for the power generated in the long run.

I'll have to agree with George with the difference between the Porsche owners and other "imports". We tend to be less willing to stray away from bolt-on upgrades and get into real internal engine mods where the real power is made. For whatever reason, I have no idea.

fast924S, got your message a while back, gonna get back to you on those valves.

hrsteel

There is nothing special about the pistons (or rings for that matter) for Alusil cylinder walls. I happen to have quite a bit of experience working with the F4i motor out of a Honda CBR600, which has the same cylinder walls. We had two sets of custom hi-compression pistons made for our motor at a value of $800 per set. They are the same forged aluminum that is used in any good piston. What makes them special is that our supplier has never made an F4i piston before, and I don’t know of anyone that produces a hi-compression piston for that motor. $800 for a one-off set of pistons is really not that expensive, and designers really don’t care if the hood ornament says Porsche or Honda; it’s still a motor just the same. (Yes, I know 944 pistons would be larger and therefore a bit more expensive, I’m just trying to give some sort of reference.)


You are getting close to the basics of IC engines and how they make power, but there is more than fuel and air volume to consider. (This is where the turbo guys tend to miss out.) Higher compression yields a higher thermodynamic efficiency and faster traveling flame front = more power with the same amount of fuel and less ignition advance. Different intake shapes and surface finishes with the same mass flow can yield different power due to differences in fuel atomization. A massive, unstreetable intake port may not make any more power than a smaller one. We have actually made power gains by tapering our intake as it approaches the motor.
Regarding 2V vs 4V: You can make a 2V motor flow as well as a 4V one. Look at what the C5-R guys are doing with an archaic 2V pushrod motor. I would venture to guess that the 944 motor is more hindered by having valves at 45degs than by the fact that it only has eight.

2BWise

I've been floating around and reading treads for months now, but this topic is right along where I'm going with mine. hrsteel I'm involved with Formula SAE at UC and am working on building up an NA engine. There are so many ways for us to avoid costs by engineering the parts and then building them in house for a fraction of the cost. But first I got to get myself out of the shop for enough time to work on my NA. It should be possible to build a high output 2.5L engine, but it will take loads of time of testing and development to make consistent power and reliablity. I know as soon as I can a break from our 05 car that I will be tearing apart my NA and looking for ways to build reliable power.

Good Luck with your 2005 car

Jfrahm

Are you sure about that?
I would suppose the CBR uses a more modern material, nikasil or a ceramic composite or something. The 944 and 928 use an Alusil block with a process used to expose more silicon in the bores. The pistons have a plating on the skirt to reduce friction and wear. You could probably slap in a set of traditional pistons and it'd last a while though.

-Joel.

StupEd05

NOS gets a bad rap. It good if you want to be able to quickly control power. Think of it as Daily Driver Economy: ON/OFF Flip it on when you want to waste someone, turn it off when grocery getting. Just dont get too carried away and start shoving a 150 shot down its throat. Keep it around 75 and you should have some good clean fun for under $1k.

Geo

Higher compression is a "while you're in there" thing and not much else. There are gains to be had from raising CR, but they are not at all dramatic.

scular

Thinking some more on compression. I remember being told by a firehawk mechanic that you can make a stroker by putting a 3L crank in a 2.5L block, or is it the other way around?

hrsteel

Jfrahm, I stand corrected: The F4i is indeed a NikaSil motor, which is slightly different from the AulSil 944 blocks. Thus far I’ve only been able to find one good side-by-side comparison of the two. It states that AulSil can be over bored, while NikaSil cannot, but AluSil pistons need to be coated with iron and tin. I’m going to try and make a few calls on Monday after work to find out if any alternatives are available and the feasibility of coating new pistons.

Scular, A 3L crank has an 8.9mm longer stroke and should bolt directly into a 2.5L block. You would probably need shorter rods to keep them from smacking the head. Displacement would be raised to 2,758cc, and compression would be dependant on piston design but should be in the neighborhood of 10.6:1 if a stock profile is used. I suppose you could put a 2.5L crank into a 3L motor if you were going to throw a lot of boost at it. It would also let the motor rev higher.

Legoland951

You sound pretty serious about this project. I can donate some stock parts for your cause and I have almost one or more of everything mechanical somewhere in my garage like spare cams for regrinding or cylinder head with no valves for experimental machining.

Sasquatch

Adding fuel to "what is possible"... Look at modern superbike motors that come out of the factory stock with over 150 crank HP, around 100 ftlbs of torque, rev to 12k and are only 1000cc. The acceleration of my last bike (Yamaha FZR 1000) was unbelievable. The Yamaha Genisis motor (designed in 1984) is a 4 cylinder, 1000cc, 5 valve, dual overhead cam carburated motor running 12.5:1 compression on standard pump gas. No pinging, just HP.

The new R1 is somewhere in the neighborhood of 155hp.

Now, what is different with those motors? I have rebuilt my fare share of them and spent countless hours building them for performance. I still have a 187hp GSXR 1000 that is pleasing his owner running the streets around Boise.

I could easily get 20-25hp from a super bike motor with cams, some mild porting of the head, a good exhaust system and spending some time reprogramming the fuel injection (or jetting the carbs, depending on the bike). When you are talking about an average starting HP of 130hp and easily getting it to 150-160, it is a huge gain.

I just can not see why the NA motor is any different. There are some great resources out there on the web that just need to be altered and be adapted to the 944. There are volumes out there on intake efficiency alone...

If I only had the time and money to invest in my car right now.......