Lindsey sells 3.0L (piston pin raised for long stroke) turbo-spec Wossners for $1000/set too.

 

Yea I know but not a 2.7l low compression piston that I looking for. Not many build a 2.7 turbo, everyone wants that 3.0 crankshaft in their engine. I'm happy with my knife edged 2.5l crankshaft. But I'm looking for a better breathing head. And the 2.7 is the answer. Plus .2 bigger displacement and a stronger big block (siamese cylinder walls(they touch unlike the 2.5L block)) are all selling factors to me.

 

Yes

 

I don't think the 3.0L NA (I'm assuming 8v) should even be an option. When the 2.5L S became the 3.0L S2 it only produced 10% more power. When the 2.5L NA became the 2.7L NA, it produced no more power. So you might be looking at a few % increase... 170hp if you're lucky. If you want NA power just buy a used 16v 3.0L or an LSx.

So between $1600 2.8 and $1000 2.9... clearly the 2.9. Whether you need the extra 0.2L for $1k depends on your goals and needs.

 

I'm with this guy. I don't think that 8v 2.5l based head would benefit from making that a 3.0 N/A engine. Best to turbocharge it.

 

You should never forget, that those mentioned engines are/were equipped with this power restrictive AFM thing.
I assume that if you're working on a stroker, you won't consider to keep the AFM. So I doubt you can't compare those old numbers regarding power with the power a stroker will generate.
The features of modern engine management will release a bit more hp than years ago was possible.

 

^+1
2.7 had bigger bore, bigger valves, bigger ports, bigger runners and +0.7cr but only made ~5hp vs the 1988 2.5...but it was still breathing all of that through a 50mmx50mm AFM square hole with conservative tune.

the S2 had a milder exhaust cam than the "S" which knocked the power down a bit, that's why S2 guys like to swap in "S" exhaust cams for a cheap power bump.

opening the intake up and playing with cam timing so far has proven quite good for my lowly 9.5cr 1985 NA engine (+17 crank hp/+21tq ) so id fully expect similar results on a larger version of the engine with even higher cr, percentagewise.

broadfoot has said his higher-CR 3.0 8v motors are good for ~190 or more and i think those are on the stock cam still. if the plumbing can support the extra flow, more cubes should equal roughly proportionally more power.

turbocharging is pretty much not an option due to smog requirements - way too much hassle to un-turbo it every 2 years. thats the same reason ive sold off my collection of aftermarket 944 exhaust headers - PITA. at least an intake, tune and stuff is easy to swap around when needed. DOHC is also out of the question for the same reason - i really can't believe how familiar the local smog guys are with porsches and the 944.

my long-ago conceived supercharger may still happen, someday in the distant future, but i just have no time in the right location (other house) to do the fab work for that project. my time spent at the house with the fab tools can be measured in hours per year.

 

IMO go with the longest stroke. It'll be your best bang for the buck.

I wouldn't worry about the rod ratio.

The head flows fine for a 200 hp engine too.

Just look at Shawns dyno and the torque (pre boost) compared to all the other cars built.

Cubic inch makes a difference, but adding stroke is the best way to add low end, and it sounds like that's what you want. Do a 3.1 with a 95 mm crank. Its the most cost effective option IMO

 

Hi Sid

Have you guys done a 95mm offset yet? Is there any chance of clearance issues with the oil pan?
We're doing a 94mm (x102mm 16v) but with a different pan so we want to ensure that it will fit which involves pulling the motor this weekend. My assumption is that the pans are similar depth to due to the X member so was wondering on the 95mm.

 

My motor is 94.75mm x 102.4mm. No clearance issues.

 

Thanks Shawn. Good to know. btw...what is the max revs you've taken your motor to at this stage?

 

It will depend on the rods. If you're doing a build like my design, the mitsu rods clear easily. As Shawn has shown.

I hope this works out well for you. As you know, I like the stroker vs bigger bore. I like that it works better with the engine design IMO.

Looking forward to how it compared. Obviously the 16v will change things a bit.

 

And here's Wikipedia info on Rod ratio. Pro's and cons for both.


Last edited 7 months ago by an anonymous user
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User:Wdl1961/Rod/Stroke ratio
< User:Wdl1961
Rod/Stroke ratioEdit

The rod/stroke ratio is the ratio of the length of the connecting rod to the length of the piston stroke. A longer rod will reduce the sidewise pressure of the piston on the cylinder wall and sress forces increasing engine life. It also increases cost and engine height.



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=== Rod/Stroke ratio ===5454 The rod/stroke ratio is the ratio of the length of the connecting rod to the length of the crankshaft's (or piston's) stroke. An increase in the rod/stroke ratio (a longer rod, a shorter stroke or both) results in a lower piston speed. A longer rod (and consequently, higher rod/stroke ratio,) can potentially create more power, due to the fact that with a longer connecting rod, more force from the piston is delivered tangentially to the crankshaft's rotation, delivering more torque.[citation needed] A shorter rod/stroke ratio creates higher piston speeds, but this can be beneficial depending on other engine characteristics. Increased piston speeds can create tumble or swirl within the cylinder and reduce detonation. Increased piston speeds can also draw fuel-air mixture into the cylinder more quickly through a larger intake runner, promoting good cylinder filling.

Rod length and stroke length are independent variables. Rod length is expressed as center-to-center (c/c) length. An engine with a particular stroke can be fitted with rods of several c/c lengths by changing the piston pin location or block deck height. A rod that is longer in relation to stroke causes the piston to dwell a longer time at top dead center and causes the piston to move toward and away from TDC more slowly. Long rod engines with a particular stroke also build suction above the piston with less force, since the piston moves away from TDC more slowly. Consequently, long rod engines tend to produce a lower port air velocity, which also reduces low speed torque. Long rods place less thrust load on the cylinder walls, thus generate less parasitic drag and result in less frictional losses as engine revolutions rise. A "short rod" engine has the opposite characteristics. “The short rod exerts more force to the crank pin at any crank angle that counts i.e.--20° ATDC to 70° ATDC” (Jere Stahl [1]). Short rod engines tend develop more torque at lower engine speeds with torque and horsepower falling off quickly as engine RPM rises to high levels.[citation needed] Long rod engines generally produce more power due to reduced engine drag, especially as engine RPM increases. Regardless of rod length for a given stroke, the average piston speed (usually expressed in ft/s or m/s) remains the same. What changes as the rod length becomes shorter or longer in relation to the stroke, is the RATE of motion as the piston rises and falls in relation to the crankshaft. A long rod fitted to a given stroke generates less stress on the component parts due to the lower rate of acceleration away from and toward TDC. The average piston speed is the same; however, the peak piston speed is lower with long rods. A "square engine" is an engine with a bore diameter equal to its stroke length. An engine where the bore diameter is larger than the stroke length is commonly known as an oversquare engine; such engines have the ability to attain higher rotational speed since the pistons do not travel as far. Conversely, an engine with a bore diameter that is smaller than its stroke length is known as an undersquare engine; such engines cannot rotate as quickly, but are able to generate more torque at lower rotational speeds.

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Seems odd that Porsche went to the trouble of building the 8v 2.7 for just 1 year.

 

they killed the NA as a model after 1989 anyways.
probably to make interested buyers spend more on an S2.

by 1990 it wouldve been a really hard job to convince someone to spend $40k+ on a car with 162 hp...especially when a contemporary corvette was cheaper and had 50% more power.