Thoughts on this combo please

[Jeff Alton]

I think I am going to sell my yet to be assembled 3.6 to finance a 3.4 project. Wait, wait, I know.......... but I crave throttle response over outright power so tell me what you think of this combo.

3.4 10.5:1
993rs cams (need to pass emissions)
twin plug heads
Jenvey 48mmm ITB set up
DTA P8PRO engine mgmt
993 HE with a Triad muffler or B+B with a custom muffler...
boat tail case
moon cylinders

I have access to a lot of the parts at cost so it makes some of the choices a little easier on the pocket book..... May also consider going 3.5...

Thanks for your opinions...

Jeff

[ChrisBennet]

Before you moon the cylinders, check how far they actually stick out into the internal airstream. Maybe I had modified cylinders or something but on my 3.2 they only stuck into the case a few mm so it made no sense to moon them.
-Chris

[Jeff Alton]

Good point Chris, I will be sure to check that out to see.....

Thanks, Jeff

[Carrera3.5L]

Originally posted by catca
Thanks for your opinions...

Jeff

Jeff, my opinion is we should trade motors.

Do you have a visual inspection as well or only actual tailpipe emissions?

Ralph

[Jeff Alton]

No visual inspectiont to speak of, just tail pipe. The standards are quite a bit lower that in CA. My 3.2 with 964 cams and no cat passes with flying colors up here as does on of my customers motors that does not have a cat............

Jeff

[Porschekid962]

Boat tailing seems to be an extra expense that you can do without in terms of the cams you are running. Thumbs up on the Jenvey setup, why did you choose DTA versus Motec or McLaren? Depending on what rear bumper you have on your car I would sway towards fabbing your on muffler setup and spend more money on the heads for port matching and flowing. On a sidenote, no affiliation but Steve from Rennsport sells a very slick Jenvey based ITB kit with brain in the neighborhood of 6k ready to go. Depending on what you have and what you want a MFI setup would be pretty mean on a motor like this. I assume with the processing power from the DTA you are going for a crankfired setup which is clean as is.
If it were me I would take the money from boattailing and mooning and put it towards 100mm p and c's for a 3.5 litre motor. Just take a look at the one Henry Schmidt built and see what you think.

Thoughts on some different engine configurations

It's about 1/3rd down the page, the numbers are awesome. Best of luck and keep us up to date. My motor build is slowly moving closer and closer and I love picking everyone's brain. Cheers!

[Bill Verburg]

Originally posted by catca
I think I am going to sell my yet to be assembled 3.6 to finance a 3.4 project. Wait, wait, I know.......... but I crave throttle response over outright power so tell me what you think of this combo.

3.4 10.5:1
993rs cams (need to pass emissions)
twin plug heads
Jenvey 48mmm ITB set up
DTA P8PRO engine mgmt
993 HE with a Triad muffler or B+B with a custom muffler...
boat tail case
moon cylinders

I have access to a lot of the parts at cost so it makes some of the choices a little easier on the pocket book..... May also consider going 3.5...

Thanks for your opinions...

Jeff

Why not keep the 3.6 using RS or SS cams and TWM or Steve Weiners intake/engine management setup.

The problem w/ DTA and Motec(last I heard) was that the knock sensors are disabled.

[Jeff Alton]

Well, I guess I could use the profits from the 3.2 sale to put the set up on the 3.6.......

Yes, Steve has a good system, that is where I get all my ideas!!

I chose (so far) the DTA partly becuase of Steve's recommendation and also becuase I got a screaming deal on one. Same for using Jenveys over the TWM stuff.....

Jeff

[jacko241]

What does boattailing do?

[Jeff Alton]

Supposedly allows air to move move freely through the crankcase. This would free up some power that would no longer be needed to push the air around.........

Jeff

[jacko241]

I see, thanks, Jeff!

[ChrisBennet]

Does anyone have any evidence that boat tailing the webs makes a difference on relatively modern ('83+) 911 motors turning less than 6500rpm? Wasn't the oft quoted "10hp gain on Porsche race motors" was in reference to motors that with cases a couple of generations older than '83+ cases, much smaller displacement, and turning a lot faster (8000rpm?).
Is Porsche doing this mod on modern motors or have they incorporated rounded webs into the casting?
Just curious,
-Chris

[Jeff Alton]

I had the same questions for a noted expert.... He said (and I am paraphrasing here and don't want to put words in his mouth) that the bigger motors benefit more as they are pushing more air in essentially the same size case internally as the smaller motors...... Made sense to me. I wish I knew more about it, but seeing how it is just my time I have to put into doing it and not $$ I figured what the heck. If it is true I would kick myself for not getting the "free" HP!!

I have not seen any "eveidence" to actually support it though. I guess you would need two identical motors run on engine dyno, the only difference being the internal mods. I only have enough cash (barely) for 1 motor to build.......

I would sure like to know though, that would be interesting.......

Jeff

[TimT]

I dont know much about DTA, but with MoTec you have to "buy" passwords to enable certain functions of their engine management systems..

If you buy a MoTec, the price you will be qouted comes without many functions turned on ie Lambda, knock, addtional logging channels.

just a FYI

[Bill Verburg]

Does anyone have any evidence that boat tailing the webs makes a difference on relatively modern ('83+) 911 motors turning less than 6500rpm?

I do know that c/c pressure is an increasingly big problem as displacement and revs go up. I've seen the cylinder base seals blown out.



The dry sump creates a partial vacuum which alleviates the problem but not totally.

Cup cars use a one way valve to create even more vacuum.

[TimT]

Does anyone have any evidence that boat tailing the webs makes a difference on relatively modern ('83+) 911 motors turning less than 6500rpm?

Well I cant say for sure about at less than 6500RPM, but...

I had the opportunity to tear down a GT3RS engine that has competed at LeMans etc..The webs were boat-tailed. and there were numerous other "tricks" were apparent.Extra high lift cam, coated internals and externals..

cool stuff to witness first hand

[jacko241]

Is there somewhere you can learn the procedure for boattailing?

[Jeff Alton]

Motec is a little to rich for me, not sure it is going to do anything the DTA can't, at least for what I need.

Jeff

[TimT]

We have cars with Haltech EFI with over 560 rwhp
(lose traction on the dyno) lap times indicate 700hp

just a thought

[Jeff Alton]

I PMed you a couple of weeks ago, I will email with some more questions for you, it is also one option I am considering......... It is just I have this incredible deal on one DTA, that is why I am leaning that way.

I will be in touch, Thanks, Jeff