High-revving 3.0 16v

[WP0ZZZ]

Originally Posted by v2rocket_aka944

not really with a 944. not enough stroke to worry about piston speed.

max offset ground stroke on a 944 is 94mm or so. stock 3.0 is 88

a rev happy Honda K24 is 99...and a 7000rpm LS7 is 101.6.

So what is the limiting factor on the 944 3.0 engine?

Per cylinder displacement is the same as in a 6.0 V8 which is large but not ridiculous. The V8 will probably have more balance though...

Originally Posted by flash968

i regularly spun my 968 engine to 7400, but i did a LOT of work to get there.

What sort of power could you get out of it?

Originally Posted by flash968

balancing and blueprinting are a must. vibrations are a real issue at higher rpms. you will need to go to great lengths to ensure that everything is matched.

Did you run with the blance shafts?

Originally Posted by 951and944S

The oil system is definitely the limiting factor.
You can get creative with original wet sump factory system by lessening the strain, deleting balance shafts, orifice limiting main thrust bearing, custom wider pump gears or additional tooth count, etc.

At what point is it worth to convert to dry sump?

[v2rocket_aka944]

Originally Posted by WP0ZZZ

So what is the limiting factor on the 944 3.0 engine?

Per cylinder displacement is the same as in a 6.0 V8 which is large but not ridiculous. The V8 will probably have more balance though...

displacement per cylinder doesn't matter for revs.
the real factors are rod+piston weight, rod tensile strength, rod bolt strength, big-end concentricity, OILING and piston speed (it's possible to move the piston up and down so fast it stops being useful for pulling in fresh air)

a 944 3.0 crank (88mm stroke) has a piston speed around 72 feet/sec at 7500 rpm.

the previously mentioned LS7, 505hp 7.0L V8 with a 4" stroke, 7000rpm rev limit with a 3 year warranty is 77.6

the real limiters of the 944 are the oiling system, and the standard block/crank...simply can't get very far in terms of added displacement due to the thin, flexible cylinder barrels and the "short" stroke 3.0 crank, even offset ground is maxed out at 94mm or so where it gets noodly.

now a closed-deck cast-iron or billet block and super-duper custom crank...

[WP0ZZZ]

I'm thinking about high-revving 3.0s again...

In terms of valvetrain, do you think variable timing such as that in the 968 head would be an advantage compared to an S2 head?

Regarding camshafts are there any well known performance cam profiles that people tend to use?

[v2rocket_aka944]

Sure, if you get custom cams whipped up (WebCams, CatCams, Milledge, among others) for the 968 that are designed for high RPM power.

the 968's variocam basically let them use a cam designed for higher-RPM power, then advance it 15 degrees (!) to have a useful bottom-end and mid-range too.

[Raceboy]

I am planning to make 3.xliter 16v n/a engine with the goal of 300+ hp. Sleeve the block to 4.155 chevy size, custom 12.5 CR pistons Catcams highest lift hydraulic cam, custom ITB-s, standalone ECU and it will get there no problem. Max rpm will be 7200 and no, stock valvetrain does NOT have problem with it.

Key to power is to have intake tuned for higher rpm, dial in the cams on the dyno and have appropriate CR for the cam (you lose a lot of dynamic CR with wilder cam) and of course most important is to tune it properly not just rely on the factory tune or some chip. Factory tune leaves a lot of power on the table with ignition for example and any sorts of restriction in front of ITB-s (AFM, MAF) is not a good thing.

[9FF]

Originally Posted by Raceboy

I am planning to make 3.xliter 16v n/a engine with the goal of 300+ hp. Sleeve the block to 4.155 chevy size, custom 12.5 CR pistons Catcams highest lift hydraulic cam, custom ITB-s, standalone ECU and it will get there no problem. Max rpm will be 7200 and no, stock valvetrain does NOT have problem with it.

Key to power is to have intake tuned for higher rpm, dial in the cams on the dyno and have appropriate CR for the cam (you lose a lot of dynamic CR with wilder cam) and of course most important is to tune it properly not just rely on the factory tune or some chip. Factory tune leaves a lot of power on the table with ignition for example and any sorts of restriction in front of ITB-s (AFM, MAF) is not a good thing.

Seems a lot of work for only 300hp? There are guys on this forum who have built a similar na motor who are pushing 400+ fwhp.

[Raceboy]

Without getting to 8k rpm there will be no 400 hp. Getting to 8k rpm requires dry sump and upgraded valvetrain.

I know Michael Mount's work, he has built 3.2liter 400+ hp 16v n/a engine.

My build is actually a budget one as I use off the self throttles for ITB's. Have perfect candidate for such build, a 3.0 S2 engine with one cylinder scored.

[9FF]

Originally Posted by Raceboy

Without getting to 8k rpm there will be no 400 hp. Getting to 8k rpm requires dry sump and upgraded valvetrain.

I know Michael Mount's work, he has built 3.2liter 400+ hp 16v n/a engine.

My build is actually a budget one as I use off the self throttles for ITB's. Have perfect candidate for such build, a 3.0 S2 engine with one cylinder scored.

I still think it’s a lot of work for a 300hp target, I don’t want to be a bore but it really doesn’t take much for a stock 2.5 turbo to reliably reach that goal and very cheaply by comparison even if you have to buy a complete engine.

Saying that I’ll be following your buld as I’ve secretly thought about a large capacity itb na build on many occasions so gl

[Raceboy]

I have built MANY turbocharged engines over the years and few n/a engines also (including 300+ hp n/a Honde H22A engine), I currently have 2.6liter fully built sleeved block 16v turbo in my 924 that is able to withstand 2+bar boost from Holset HX40 Super, so that is not the case.

I plan putting that engine onto 944 S2 cab for fun driving and unique engine sound (ITB's+tuned exhaust), will be fun project. And at the same time tuning the engine management in a way that the engine is fully streetable and has nice behaviour in traffic.

[robert_hooper]

HI All, I run a 968 motor in my 924 race car, I get 300hp at the flywheel, change the bearings every 2 years, new oil every meeting, 60mm throttle bodies and big cams, revs to about 7300. It can be done but it will cost,

https://www.youtube.com/watch?v=S-KeSFRL2U4

[stownsen914]

I have an old IMSA 968 that currently has a 3.4L motor built by Mr. Mount. 370 hp at 7200. ITBs with Motec, dry sump, Pauter rods, no balance shafts. I suspect there is some hp left in the induction, as the ITBs are 52mm off a smaller motor. I have to admit some ignorance on the details of the drive train. It's a full race application, but it's surprisingly tractable.

Scott

[951and944S]

Chiming in since this popped back to the top,

I think if it were me as the OP, I'd either shorten the stroke or at least start with the 2.5 format and just big bore that.
The 3.0 liters having the longer stroke are a worse candidate.
This all opens up the list of max revs vs the oiling system again though and there's really no way around getting safely past 7500 IMO.

If you delete the balance shafts, you can shrink down the passage size to the #3 main/thrust bearing as it does not feed a rod and will no longer feed balance shafts.

In looking at the main bearings, it seems evident to me as a lifelong automatic trans tech with tons of history fighting lube problems in automatics, that using two sets of main bearings, discarding the lower smooth set and using grooved in the upper and lower crankcase would give a 360 degree oil feed to the main feed hole in the crank that eventually supplies the rods.
I have discussed and have been given reasoning why this might be detrimental, mainly combustion load on the crank vs. surface area of the lower smooth bearing but it's still worth considering. The way the bearings are in stock state, the crank feed oscillates between on/off through 360 rotation. Severing the feed obviously causes a void between start/stop.

The oil filter housing/oil cooler console. Pfft, way too many turns where the oil goes through the OPRV, cooler lines, filter. Still working on that one but I will come up with something better than factory as actual assembly draws nearer.
Close attention to detail on windage and creative precautions on drainback.
I am running a belt driven vacuum pump for better ring seal/flutter but you have to be careful not to starve the piston pin and upper rod bushing since there will be less oil mist and splash. Vertical gas porting into the top ring land helps with high rpm flutter and better ring seal as well. The Mahle piston has force fed piston pin lube by delivering oil ring scraping to the pin boss. You can add this feature to any piston however.

Lastly, my cams are high enough lift that 16V springs will not work, clearancing for lobes in head required at .455+ lift.
To take advantage of a full system, you need a specifically tuned exhaust, custom to your exact setup. Any aftermarket bolt on will be a compromise. Likewise, you need a scientifically tuned intake as well...., my rules set does not allow but the 968/S2 and S manifolds are pretty darned good.
I am going against the grain and staying with a 4-2-1 design on the exhaust which should allow for power and torque over a wider band of rpms than a header/collector combo tuned for solely high rpm power...., something to consider since a high rev 4 cylinder will already exhibit a peaky, narrower power band than inherent in stock I4 form.
Including a custom pan, I expect to have $7k in this engine, complete long block installed in chassis give/take $1k.
Closer than a guess or an estimate as I am nearing the end of accumulating the parts and custom work but jury is still out on my cylinder head, your mileage may vary on this specific piece since my head cannot have porting further than 1" into port with gasket matching allowed.
You want to make sure the crank and cams are extremely straight and turn very free with as close to .0000 runout as possible.
To the OP's concern re vario cam vs S2 tensioner, it's best to shim and deactivate oil activation of the tensioner so, 19T cams from the S or S2 and the S2 head or converted 968 head (968 has 18T cams).

Blah blah blah.....,

T

[nyc951]

Originally Posted by stownsen914

I have an old IMSA 968 that currently has a 3.4L motor built by Mr. Mount. 370 hp at 7200. ITBs with Motec, dry sump, Pauter rods, no balance shafts. I suspect there is some hp left in the induction, as the ITBs are 52mm off a smaller motor. I have to admit some ignorance on the details of the drive train. It's a full race application, but it's surprisingly tractable.

Scott

More details about this motor, please! Any pictures?

I want to retain an NA motor in my street 968 and having 320 flywheel HP and a 7300 RPM redline would be awesome. Is that too much to ask for, Santa??

[nyc951]

Originally Posted by Raceboy

I am planning to make 3.xliter 16v n/a engine with the goal of 300+ hp. Sleeve the block to 4.155 chevy size, custom 12.5 CR pistons Catcams highest lift hydraulic cam, custom ITB-s, standalone ECU and it will get there no problem. Max rpm will be 7200 and no, stock valvetrain does NOT have problem with it.
.

Any updates on this build?

[soSincerious]

you know what RPM stands for right?















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