3.2 to3.4

[Carrera3.5L]

Originally posted by Wayne at Pelican Parts
100mm cylinders expose other problems, mainly the need for twin ignition to achieve good performance across such a large cylinder. Also, at 100mm, the cylinder walls are getting very thin, leading to reliability problems.

I would recommend 100mm for a street motor not running Motronic, as you can't easily customize the timing or fuel characteristics of this system without an expensive and difficult to program chip. The 98mm pistons and cylinders can be made to work with the existing 3.2 system quite well...

-Wayne

Well, I'm obviously biased and couldn't resist the urge to keep my big mouth shut, but I find the above opinion about half-true...

I agree that twin-ignition should be used with such a large cylinder bore, especially in an application with higher compression, CIS/Motronic and/or running pump gasolines. Twin-ignition, while not inexpensive, is certainly not a problem in my view. Far from it, not only will it increase power, provide better fuel economy and result in a crisper running engine, it provides an extra safety margin against detonation. I did some dyno testing on my motor a few months back with only the upper bank of plugs firing and the difference was over 15 horsepower! This was with Steve Wong at my side programming for both single plug as well as twin-ignition. I find twin-ignition to be a real godsend, especially with 91 octane gas and sweltering SoCal summers...

While the cylinder walls do indeed get thinner and the engine case spigot bores have to be enlarged from 103mm to 105mm to accept the larger cylinders, any long-term reliability problems are much more likely to crop up in a 930 or other forced induction application where higher temps and stresses come into play that may not be an issue in normally aspirated applications.

These concerns led Dieter @ Andial to design in conjunction with Mahle the 3.5L long-stroke motor used primarily for 930 applications, which is a modified 98mm bore piston/cylinder combined with the 964 3.6L stroke crankshaft. This still allowed a significant increase in displacement over the 3.3L which increased the low-end torque and reduced turbo lag prevalent in these motors, especially in the '80s when turbo technology was nowhere near what it is today (a modified K27 was the hot set-up back than).

I would offer the exact opposite opinion as Wayne. I would be much more leery of a 3.0L to 3.5L SC based motor using mechanical CIS than a 3.2L to 3.5L Carrera Motronic version where one actually CAN precisely customize the fuel & timing characteristics (see Steve Wong).

I would like to know how much more expensive and easier it is to program a 3.4L chip vs. a 3.5L chip. The answer, it isn't any more expensive nor is it any harder...Steve will perform his wizardry based on the engine specs you provide him and will continue to make improvements (both part & full throttle) based on your dyno plots and feedback until it is where both of you want it. Can this be done with the same precison using mechanical CIS?

With any motor rebuild, whether stock or race, the success or failure usually lies with the quality of the parts used and the skill and attention to detail of the engine builder...

Wayne, how about a friendly wager as to how long my personal motor lasts? Never mind that I have seen many 3.5L's over the years last well over 100,000 miles, I would assume by the recommendation you gave that you have seen many fail long before 100,000 miles. Mine is driven daily, has 15K on it at present and accrues about 8K a year. Based on those numbers, we should still be both young and sane enough for one of us to pay up when the motor reaches 100K (roughly the year 2017)...

Ralph

[jdm61]

Originally posted by Carrera3.5L
Well, I'm obviously biased and couldn't resist the urge to keep my big mouth shut, but I find the above opinion about half-true...

I agree that twin-ignition should be used with such a large cylinder bore, especially in an application with higher compression, CIS/Motronic and/or running pump gasolines. Twin-ignition, while not inexpensive, is certainly not a problem in my view. Far from it, not only will it increase power, provide better fuel economy and result in a crisper running engine, it provides an extra safety margin against detonation. I did some dyno testing on my motor a few months back with only the upper bank of plugs firing and the difference was over 15 horsepower! This was with Steve Wong at my side programming for both single plug as well as twin-ignition. I find twin-ignition to be a real godsend, especially with 91 octane gas and sweltering SoCal summers...

While the cylinder walls do indeed get thinner and the engine case spigot bores have to be enlarged from 103mm to 105mm to accept the larger cylinders, any long-term reliability problems are much more likely to crop up in a 930 or other forced induction application where higher temps and stresses come into play that may not be an issue in normally aspirated applications.

These concerns led Dieter @ Andial to design in conjunction with Mahle the 3.5L long-stroke motor used primarily for 930 applications, which is a modified 98mm bore piston/cylinder combined with the 964 3.6L stroke crankshaft. This still allowed a significant increase in displacement over the 3.3L which increased the low-end torque and reduced turbo lag prevalent in these motors, especially in the '80s when turbo technology was nowhere near what it is today (a modified K27 was the hot set-up back than).

I would offer the exact opposite opinion as Wayne. I would be much more leery of a 3.0L to 3.5L SC based motor using mechanical CIS than a 3.2L to 3.5L Carrera Motronic version where one actually CAN precisely customize the fuel & timing characteristics (see Steve Wong).

I would like to know how much more expensive and easier it is to program a 3.4L chip vs. a 3.5L chip. The answer, it isn't any more expensive nor is it any harder...Steve will perform his wizardry based on the engine specs you provide him and will continue to make improvements (both part & full throttle) based on your dyno plots and feedback until it is where both of you want it. Can this be done with the same precison using mechanical CIS?

With any motor rebuild, whether stock or race, the success or failure usually lies with the quality of the parts used and the skill and attention to detail of the engine builder...

Wayne, how about a friendly wager as to how long my personal motor lasts? Never mind that I have seen many 3.5L's over the years last well over 100,000 miles, I would assume by the recommendation you gave that you have seen many fail long before 100,000 miles. Mine is driven daily, has 15K on it at present and accrues about 8K a year. Based on those numbers, we should still be both young and sane enough for one of us to pay up when the motor reaches 100K (roughly the year 2017)...

Ralph

Ralph......are you seeing 246 hp at the rear wheels?

[Carrera3.5L]

Originally posted by jdm61
Ralph......are you seeing 246 hp at the rear wheels?

Yes, the same Dynojet chassis dyno was used for the before/after testing and for chip optimization. Don't know (or particularly care) what the actual driveline losses are (many use 15% but is probably slightly less).

A nice 50 horsepower or so gain with a nice torque curve for street use over the original, slightly modified 3.2L motor...

Would have liked peak power a little higher in the rpm range and without such a dramatic drop-off but limited in what I could do...You can search some of the other dyno graphs for similar type motors built without smog constraints and using higher grades of gasoline and will find that they make comparable or exceed this motor's horsepower.

A "compromise" motor intended to pass smog for sure...

Ralph

[Facey]

indeed...

as i would be very sad if i just spent all this money and had my car off the road for 4 months in order to gain less then 15wrhp...

i'm hoping to see a number north of 300. (barely)...but i will be in no way smog legal...or alibge to any noise regulations.

and i probably won't get anywhere near the fuel mileage that you do....or idle as nice.....but it'll be worth it.

would love to see some pics of your engine though

[jdm61]

Being that I live in Florida, I don't have to worry about smog.......and if these fart exhausts that the import tuners use....or the "loud pipes save lives" Harley guys are any indication, noise isn't much of an issue in the good ole Sunshine State either. That said, i don't think my ears could handle open pipes and i would like to be able to hear my stereo a little bit, so i will probably forego the straight pipes or race mufflers. I'm currently installing the Fabspeed Euro setup with the single out muffler, but that will probably be replaced in a year or two with the SSI or B&B header setup with multiple outlets.

[Facey]

just so ya know the stainless steel headers probably make as much differance as the muffler does.

they are way way louder, regarless of the muffler, and to make really good use of them, you'll need a muffler which is also failry free flowing (fabspeed is probably), so the noise level will defiently go up.

[jdm61]

Originally posted by Facey
just so ya know the stainless steel headers probably make as much differance as the muffler does.

they are way way louder, regarless of the muffler, and to make really good use of them, you'll need a muffler which is also failry free flowing (fabspeed is probably), so the noise level will defiently go up.

If I decide to go with headers down the road, I will put the second outlet on the Fabspeed. I wanted to leave the rear valance intact for now.

[BReyes]

I was passed by a rsr (74ish Yellow 11 rear flares whale tail) going on the 405 & Mulholland.

What exhaust does that car have guys?

It was nice and loud too.

[sp_cs]

Apologies for digging up an old thread...

As per another thread of mine, i'm weighing up 3.4 options at present - having scoured Andial's website again, i see they do a Motronic 3.5 P&C kit at 9.8:1CR.

What i'm reading above is that twin-plug is a firm requirement for a 3.5 cylinder, is this correct?

I'm UK based, so have access to decent fuel; with this in mind and running at 9.8:1, is 3.5 single plug do-able?

Cheers all

[cnavarro]

I would say that a single plug 9.5:1 is do-able with good fuel. I've even done some 102mm 3.0/3.2 at 9.5:1 just fine. The nice thing is as the bore gets larger, you need less and less dome to get the desired CR, which gives you better and better flame front propagation. Not to say that twin plugging isn't worth doing, but not a must as long as you are not overzealous with your CR demands.

[sp_cs]

Thanks Charles, thats good to know.

I'm tempted, but unsure whether trying to achieve at euro spec CR of 10.3:1 is worth attempting, or leaving at 9.8:1.

More research required!

SP

[charleskieffner]

since a top end is looming with #4 exhaust leaking down 19%, its already become "while yer in thar" type of mind set. really dont know if i'll be happy just building a "bulletproof" showroom stock 3.2. its not like were chasing points or trophies and showroom stock is/ was a great guideline to follow. my wrench states i have 25000 miles left on it before power goes down or i become a mosquito fogger so i have some time to think this thru. 120 K on it now.

but while yer in thar sure opens up a can of worms to reliability and the dreaded summer heat here in the dezert.

if i just go 3.4 with some 964 cams and other assorted goodies do i start down the slope of less reliability?

if i go 3.5, am i building a grenade where temps soar and reliability go out the window?

can you still get 250K miles out of either a 3.4 or 3.5?

my track temps on the hottest days here with a setrab in front, along with fender cooler and engine cooler NEVER see above 210 pinning the hell out of it at firebird, pir or calif mtr speedway. even when going putt putt in gridlock with a/c on does it get above 210 degrees.

so really im looking for reliable bang for buck. jeremyd's seems like a good combo thats suited for track and street/highway.

open to all suggestions aside from going to 3.6. at that point i'll just buy a roached full blown sunroof delete coupe stripped down for track only and then try stuffing both into a 2 car garage thats got so much crap in it only one fits in there now!

im willing to leave no stoned unturned and money is not a question. reliability is job numero uno. its not a daily driver in the dreaded summers but i still have to traverse dezert north south east west to escape this hell hole in the summers for relief. and when its 118 degrees plus its already 105 degrees by 10am so early starts out of town are the norm.

also since its a "collectible" smog -emissions are not an issue.

open to ALL MONEY SINKING CRAZY IDEAS!

[JeremyD]

Mine works pretty well - no track oil temp issues even in hot and humid sebring.

I'd try and find some mahle 9.8 to one slip in 3.4's - talk to camgrinder on what grind he recommends -

Lots of options - start acquiring parts...

[sp_cs]

Originally Posted by cnavarro

I would say that a single plug 9.5:1 is do-able with good fuel. I've even done some 102mm 3.0/3.2 at 9.5:1 just fine. The nice thing is as the bore gets larger, you need less and less dome to get the desired CR, which gives you better and better flame front propagation. Not to say that twin plugging isn't worth doing, but not a must as long as you are not overzealous with your CR demands.

i've spoken to a couple of European indies, both reckon 11.1CR is safe on single plug, with 98Ron fuel and Motronic pistons

Seems high to me?

[cnavarro]

Yup, too high to me. I think part of the illusion is that the advertised compression ratios are actually quite lower than the real ones plus another consideration is that the static and dynamic compression ratio really honestly much be considered when setting fuel and ignition requirements. I've had some customers only able to run 8:1 on the four cylinder engines with one particular cam (no overlap, dynamic ~= to the static) where on another cam, 10.5:1 static or more still has less dynamic compression than the previous static 8:1 engine with the same 91 octane fuel. See my reasoning?

[sp_cs]

hmmm, kinda....but that's because i'm a dimwit...

One of the indies is a Mahle dealer in Switzerland and one builds (air and water cooled)engines for customers in various Porsche series here in the UK, so i'd trust their judgement too.