Would like to keep the spool i got from my billet k16s, but they will now be a bit small for this engine - thinking A3071 or A3076, but will i get a noticeable lag with the A3076 even with a 4.0L?

 

what i saw from randys 3.8 upgrade was about 40 more rwhp down low. this gets him moving faster than my 3.6 and then his turbos take over. he runs a 3073 tial for better spool than the 3076 and more power than the 3071.
of course tim941nyc has proven you don't need to punch the motor out to make huge power. 160 mph trap and 235 at the mile from a 3.6 and more longevity out of the motor. just food for thought

 

You will love the Alphs 30's with a good tune on a 4.0. I would go 71 or 73. Let me know if I can help out.

 

Are you saying a 3.6 is more reliable than a bored/ stroked 3.6 that now displaces 4.0 each making the same power?

 

i would think a punched out 4.0 let alone 3.8 would provide that maximum platform for power without sacrificing any "longevity" since all your rods/parts are to match and seemingly better equipped to handle the increased hp#'s.. 800+ 3.6 builds aren't exactly building longevity into their "builds" but then that isn't the ultimate goal is suppose.. i would imagine the reverse would be true. regardless of building up the internals. e.g. your building longevity OUT of the motor by asking that much more out of a 3.6. but thats just logical and common sensical, i know nothing.

 

based on the the porsche factory teardown specs for each size motor i would say yes. the hrs run for a 4.0 is much less than a 3.6 before the required teardown

as for reliability i would say that is completely dependent on the builder and quality of the parts used.

 

Wgere does Porsche quote that ?Do they make the same power or is the 4.0 making considerably more?i am trying to wrap my head around that.I would think a 4.0 would be less stressed to make the same power a 3.6 does in a turbo setup with all other things being equal.

 

The stroker is capable of making more power at a lower boost. The cons are the piston speed ratio (this relates to stroke/rod ratio). Higher rpm's become much more stressful on the motor components as the stroke/rod ratio goes below 1.6 to 1. An example would be a 4.3L motor ideally should have a 133.0 mm rod length to attain a 1.60 to 1 ratio. The problem becomes without raising the deck hight and lengthening the timing chain, the physically longest rod length is just under 130.0 mm. That brings you down to, if memory serves me correctly, a 1.57 to 1 stroke/rod ratio .... which lowers the safe redline. As a basis, if memory serves me correctly again, the 3.6L with it's 78.4 mm stroke has a ratio of 1.63 to 1.

http://ftlracing.com/rsratio.htm

The Porsche motor is what is referred to as an over square motor. This allows the motor to make power at higher rpms. When you begin squaring the motor up ..... the rpm power range comes down.

Our 4.3L motor with GT35R's would make 1000 hp at 1 bar. Again, the limiting factor becomes the higher rpm unless you want to spend a bucket full of money.

 

Chad thank you for the info and i am familiar with what you are referring to but as for the application of our turbo motors that max out rpm at 7500 rpm ,are you saying that a 3.6 making 1000whp is more reliable and will have more longevity (all other things equal) than a 4.0 making the same power?

 

I got a ride in a fully built ESmotor 4.1L with GTX3076's and I didn't feel any lag. It was amazingly fast on low rpm's.

That's my dream setup for a fast daily driver but I think when my time comes, I will go with the 3.8L kit, it's cheaper and doesn't involve lots of parts and machining. Should be perfect for my A3071's.

In your setup I would go with the 76's

 

Joe, we both understand there is more to longevity than piston/rod ratio. Let's say for the sake of discussion Porsche optimized the 3.6L with a P/R ratio of 1.63-1. Making a 4.0L stroker would require a 2 mm stroke on the crank (78.4 to 80.4) plus a slight increase in piston size. In my opinion an ideal set up would be to do the calcs and increase rod length enough to keep the same P/R ratio. There by keeping the angular degree on the pistons/liners the same. Doing this should keep the degree of reliability equal . The 3.6L will safely rev higher to make it's power and the 4.0L will have a lower redline, but will make power earlier.

That is the best way I can explain how I see your reliability question to me. You also have me at a disadvantage. We have never assembled a 3.6L that made 1000 hp period. Our 3.6 back in 2004 was making about 740 rwhp. After we bent our rods we went with 102, 104.4 and 105.4mm pistons as well as 80.4 and 82.4mm cranks. Our 4.3L has made considerably more hp with plenty of boost available. Trouble is we didn't have enough ***** to push further fearing the motor would scatter.

Back to your question. I believe a 3.6L Porsche recommended redline would have same reliability as a 4.0L using a longer rod length (to keep the P/R ratio equal 1.63-1) as well as the 4.0L would have a new formula derived redline which would be slightly lower in my opinion.

 

thanks

 

Joe,


Is yours a 3.6 ? I cannot remember. I was there when you ran your amazing top speed and when you did your little spin dance at the end of the Texas Mile.