Opinions on my 3.2 to 3.4L build?

[gliding_serpent]

Just wondering if you folks mind commenting on my engine build specs. I won't get into all the details (arp studs, stainless fuel lines, etc) but I wanted opinions of the performance aspect of the build (i.e. is is a good mix?).

The goal is a engine that has strong midrange as opposed to a high RPM screamer (I plan to have it live below 6500rpm). Midrange is more key as I will essentially be keeping stock gear ratios. This is a street car that will see the odd HPDE. This is also not a budget-less build so I am not going all out.

84 3.2

915 transmission: essentially stock gears and final drive ratio, Guard 40/60 LSD, upgraded bearing retainer plate and diff cover, wevo short shift. New engine and tranny mounts. May get wevo internal gate shift. I might slightly lengthen 2nd with something from Guard to increase reliability from the increased torque.

Intake: cup style airbox (current airbox drilled by prior owner). Dynos here. I opted against extrude hone as I was advised that with my near stock RPM, benefits would be lessened and my low and mid range performance would take a hit. I suspect the cup airbox may have a similar effect.

Engine: 964 cams (wondering about 20/21), max moritz 9.8:1 3.4L single plug design pistons, 91 octane (all we have local). Stock springs.

Exhaust: SSIs, M+K 2:1 (have both, not changing)

Chip: SW stage 2 (custom mapped, dyno tune), 6760 redline (will live below 6500), 91 octane

[Josh D]

Looks like a solid combo to me.

[gliding_serpent]

Steve Wong estimates 220rwhp or 260hp at the fly, which was my hope. He did point out that stock headers and muffler might add 10-13 more hp. Talk about low hanging fruit. Dynos on his site show headers and sports exhaust getting you above 280hp (288 in one car w 93 octane).

Might stick to my guns, but i will keep my test pipe/oem headers just in case i choose to eventually switch back.

When i got my exhaust, i did not anticipate a top end rebuild, 3.4l, or 964 cams. Ssi's are a lot of $$$ for the results in this setup... Fine for 3.2... But now i am thinking...

Either way, resale is good.

[darrin]

seems the relatively greater restriction offered by the SSIs could well increase your midrange feel and make for a better "butt dyno" than stock headers and cat bypass, regardless of ultimate #s -- since you have both (and it will be relatively easy to swap), once you have things (relatively) dialed in, you might want to try both options and see which one is "funner"

[gliding_serpent]

I plan to do as you say. I will probably clean up the oem headers and current exhaust and hang them on the wall for now.

[Bob Kontak]

Originally Posted by Josh D

Looks like a solid combo to me.

+1 Nice balance.

Don't fully understand longer 2nd but if transmission pro's say it's better..... FWIW, I just picture more strain at the point of 2nd gear engagement under load but I don't know nuttin' and I can prove it.

[spuggy]

Originally Posted by gliding_serpent

Just wondering if you folks mind commenting on my engine build specs. I won't get into all the details (arp studs, stainless fuel lines, etc) but I wanted opinions of the performance aspect of the build (i.e. is is a good mix?).

The goal is a engine that has strong midrange as opposed to a high RPM screamer (I plan to have it live below 6500rpm). Midrange is more key as I will essentially be keeping stock gear ratios. This is a street car that will see the odd HPDE. This is also not a budget-less build so I am not going all out.

84 3.2

915 transmission: essentially stock gears and final drive ratio, Guard 40/60 LSD, upgraded bearing retainer plate and diff cover, wevo short shift. New engine and tranny mounts. May get wevo internal gate shift. I might slightly lengthen 2nd with something from Guard to increase reliability from the increased torque.

Nice - all good mods. I ran much the same setup with way over 300 ft/lbs for years (with some respect) - and you'll love the 40/60 GT.

Engine: 964 cams (wondering about 20/21), max moritz 9.8:1 3.4L single plug design pistons, 91 octane (all we have local). Stock springs.

Hotter cams (like 964) usually take away mid-range grunt for more top-end. That said, there's some reports that 20/21 cams give more power low down than SC/3.2 cams with a curve that looks like a table-top over 4000 and goes on longer before it drops off. Which sounds useful...

I would budget for ARP rod bolts on a 3.2 or 3.3 if you didn't already. That's $600 well invested - spun rod bearing will cost way more. I have invoices...

[spuggy]

Originally Posted by Bob Kontak

Don't fully understand longer 2nd

Taller 2nd than stock is great on a motor that has good low-end torque, even more so in a light car. I pretty much just use 1st for noodling about in traffic/parking. Even in traffic, once rolling over 5MPH, you're probably holding 2nd anyway, until you have to stop.

Gear changes are lost time - and putting lots of power through 1st on a 915 isn't the best idea anyway.

So for a good compromise between stress/failure, avoiding wheelspin and a brisk 0-60, you pretty much just get rolling off the line with low throttle, get promptly into 2nd and start using it. Or (with more power), pull away in 2nd if the clutch can tolerate a little slipping. Just to avoid the less useful time spent in 1st gear, and the 1-2 shift.

For the track, when going up through the gears, taller 2nd lets you hold the gear longer, makes 2-3 closer - and, when going down the gears, gives the option for some corners of using 2nd rather than dropping low/out of the power-band in 3rd.

I liked mine, until it broke (but it was a very old gearset that'd probably been used and/or timed out in a rally car, sooo...)

[fred cook]

I think you are on the right track. The only thing that I would do differently is to change over to twin plug ignition and bump the compression ratio up to about 10:1. I built a 3.3SS engine for my SC recently and took pretty much the same route that you describe. I reused the block, crank, flywheel and oil pump and replaced everything else. I used Carrera heads (you already have those), LN Engineering 100mm cylinders, 10.1:1 Mahle pistons, a set of connecting rods reworked by Ollies, 964 cams, SSI exhausts, early SC CIS airbox with the large runners and the Electormotive XDi direct fire twin plug ignition. The end result was an engine that makes good bottom and mid range torque but will still pull quite well up to 7,000 rpms (my redline). By going the twin plug route, the engine timing is set at 25 degrees instead of 36 degrees. It runs quite well with no issues on 91 octane pump gas (premium). It starts easily and is well behaved in traffic...... until you stick your foot into the throttle! By keeping the CIS injection, fuel mileage has even stayed reasonable. Good luck with your build!

[Bob Kontak]

Originally Posted by spuggy

Taller 2nd than stock is great on a motor that has good low-end torque, even more so in a light car.

Thanks for the write-up.

[gliding_serpent]

Originally Posted by spuggy

Taller 2nd than stock is great on a motor that has good low-end torque, even more so in a light car. I pretty much just use 1st for noodling about in traffic/parking. Even in traffic, once rolling over 5MPH, you're probably holding 2nd anyway, until you have to stop.

Gear changes are lost time - and putting lots of power through 1st on a 915 isn't the best idea anyway.

So for a good compromise between stress/failure, avoiding wheelspin and a brisk 0-60, you pretty much just get rolling off the line with low throttle, get promptly into 2nd and start using it. Or (with more power), pull away in 2nd if the clutch can tolerate a little slipping. Just to avoid the less useful time spent in 1st gear, and the 1-2 shift.

For the track, when going up through the gears, taller 2nd lets you hold the gear longer, makes 2-3 closer - and, when going down the gears, gives the option for some corners of using 2nd rather than dropping low/out of the power-band in 3rd.

I liked mine, until it broke (but it was a very old gearset that'd probably been used and/or timed out in a rally car, sooo...)

Could not say it better myself. This is why I am opting for a taller/longer 2nd. 0-60 I do not care about, but the rmp drop from 2nd to 3rd in oem gearing is a bit high, near 2K rmp drop when up-shifting. I want me second closer to 3rd. Plus, in our single second gear corner, I find myself running out of gear too early on corner exit. With a faster/lighter car, a longer second will help a lot and prevent a mid shift to 3rd on early turn exit.

A taller gear from Guard will also be stronger than the OEM gear (mine has light scoring, still useful, but a risk with a stronger motor).

[gliding_serpent]

(to expand on my post above) So I will throw a wrench in things. Steve Wong pointed a few things out to me.

- one can expect 260 flywheel hp with this setup once dyno tuned. Not bad. Steve wong says it is hard to get over 260hp with SSI's... the primaries become a choke point and returns diminish quickly.
- one would get an extra 10-13hp with the stock heat exchangers and muffler and cat bypass!!! Add a bit more with sport muffler. So we are talking 270-275hp. More if you have larger headers and sport muffler.

Interesting. I got my SSI's for the original stock 3.2 (without upgraded cams) as they are superior to the OEM heat exchangers/sport muffler/cat bypass in midrange and top end power if you look at the data SW has shared. But go with cams and larger displacement, and the smaller SSI primaries begin to limit the power in a way the OEM do not.

Decisions decisions... my SSI and M+K 2:1 are brand new uninstalled... and look so pretty, and I have everything for the backdate, but 10-20 more hp by keeping my current oem/cat bypass/sport exhaust is tempting. Beauty or the beast?

[88-diamondblue]

I did a rebuild and went with the 3.4 upgrade and cams amoung some other things. If you are buying new P&C's i would go to the 3.5. As i remember the 3.4 is just shy of that where the 3.5 is full 3.5. There was a long thread about a 3.5 build that ended up very drivable and lots of power. Steve did the chip and tuning for it. He has tuned enough engines to know what id the best. He did my chip and its great. Have fun with it.

[gliding_serpent]

I think the issue with the 3.5 (and I did not research them...) is compression and piston top design. I am unsure if they have max Moritz style tops. Even if they do, I am wondering if the diameter is really starting to further stretch the single plug design.

My thought is 3.4 now, and if someday those wear out, I still have the 3.5 overbore option.

[88-diamondblue]

This is the thread i was referring to. There is a part one to it as well. Lots of good information
http://forums.pelicanparts.com/porsche-911-technical-forum/186906-3-2-3-5-part-ii.html

[tshebib]

John,
Just for reference, I'm using Guard's 1.65:1 2nd gear and couldn't be happier. It has a distinctive whine which I actually enjoy. With regards to your exhaust dilemma, I was never a fan of the stock setup as the crossover pipe throws too much heat directly at the #3 and #6 cylinders (coincidence?). Maybe I'm paranoid but why put heat where you don't want it. I wonder if anyone has converted 993 heat exchangers to fit on 3.2 heads?
Maybe Bill V. can chime in.
Tom

[spuggy]

Originally Posted by gliding_serpent

But go with cams and larger displacement, and the smaller SSI primaries begin to limit the power in a way the OEM do not.

IIRC, the SSI's were originally developed for the much smaller motors, so not too surprising they start to limit a larger one as you tune it.

270-275 HP should be pretty useful... I wonder at what point the stock primaries are restrictive?

I note RarlyL8/M&K make larger primaries for 911's...

The ones they built for me were beautiful workmanship, BTW. I've seen good welding before, but those headers were truly amazing - a work of art.

Beauty or the beast?

My $0.02: form follows function. I don't much care what it looks like, if it works better (can't usually see it from the driver's seat)...

But high-end stuff usually looks better too.

[tshebib]

I did a little searching and found this solution.
Fitting 993 Heat Exchangers to 3.2 Carrera - Exhaust: Gas and Heat - Impact Bumpers
Apparently you just need to flip the flanges to get the 993 HE's to fit.
Anyway,Something to think about.

[gliding_serpent]

Tom... Larry has 993 b+b headers with heat on his wall. Need to verify primary diameter (may be too large).

Brand new ssi's will be easy to flip...

The other end is, how obnoxous do i want my car to sound? Not too obnoxous is my answer.

[pooder]

My 2 cents: Nearing completion of my 3.4 conversion and agonized over these details in anticipation of this project, my best advice is to find a reputable Porsche engine builder and then trust his advice to achieve what your specific goals are. Even if this is a project you are going to do yourself, find such an expert and pay him for his advice. My car will only be on a track for DE events and my primary interest was not in the peak HP at 6000 rpm which would represent <1% of my driving. A detailed discussion with my engine builder of my expectations and his recommendations determined my ultimate build specs. By no means am I suggesting that there is not valuable information on this forum, but someone who builds Porsche motors professionally will have a wealth of experience and insight to lend to your project.