Another "What if" 3.2 engine build... thoughts?

[78SCRSMAN]

Hello,
Here's what I'm thinking...
starting with a Carrera 3.2 (84-88)
P & C's would be JE and Nickies 10.5-1 Comp @ 95mm cylinders
PMO Carbs
Some sort of street cam
SSI's w/2 in 2 out exhaust (not sure what size on the SSI's)
Not sure on the ignition (NOT planning for twin plugs)

Any thoughts and/or suggestions on this kind of build would be appreciated.
Thanks in advance
Derek

[RichHawk]

prevailing wisdom that I've gleaned from the list ,and am using to build my 3.2 as we speak is:

10.5:1 needs dual plug setup. This was too much money for me. so I am sticking with 9.5:1 JEs.

To compliment the headers, get a high flow Cat, or cat bypass, and sport muffler.

Then to utilize the exhaust to it's fullest, you'll need a better cam. The 964 cam or something slightly better is used often for street motors. Check with John D. (Camgrinder user name) He's really knowledgeable.

I don't like carbs. I like FI, because it works when cold, and works when hot, and does not foul plugs. and it's tunable. just different tunable than swaping jets.

Expect to spend a LOT of money and a lot of time.

Richard

[78SCRSMAN]

Thanks
I've read that dual plugs are not necessary for this CR... it's what the Euro cars came with from the factory. Also, my car is a 78 so no need for emissions type exhaust. I planned to use SSI's w/heat. I'm kinda on the fence with the carbs. It would be great to know what can be gained if any by using PMO's vs. the stock Motronic setup. Sure wouldn't mind saving the $3700 for something better.
What would I expect to pay for 964 cams and do they just bolt right up?
Derek

[78SCRSMAN]

I suppose the 10.5:1 CR could be toned down a bit to, say 10.1:1 and stick with 93 octane fuel... which I will do regardless.

[Flat6pac]

Cams will bolt right in, only the profile changed
Bruce

[RichHawk]

I had the same "WTF? The Europeans have the 10.5:1 without dual plugs??? Why can't I" thought.
But the gas is not equivalent here in the US and in Europe, and the Motronics system does not use a knock sensor, so it cannot change the ignition or the fueling to compensate for detonation. So you would be retarding the ignition on your 10.5:1 to conservatively keep you out of detonation, and that reduces the effective hp, and reason you went with the 10.5:1 to begin with.

So I started paying attention to premium octane gas. I can't reliably find better than 91 octane in Kansas, and was not willing to risk damaging my motor with detonation because of poor gas. So 9.5:1 is where I'll stay.

Look up Steve Wong. He's the guru on FI chip tuning for the 911. If I recall, the stock FI system might be good up to 250Hp but then it's flow limited by the flap style Mass airflow, and the design of the intake. if you want more than that it's dual plugs, 10.5:1, and either carbs or aftermarket FI systems. (assuming normally aspirated, and no nitrus)

Please someone with experience chime in here, because I'm speculating now at the 250Hp limit...

Richard

[78SCRSMAN]

Don't know where I came up with 93 octane... guess I was just dreaming. I meant 91 but yes I suppose without 2 plugs per cyl., it's no good. Someone told me it's OK to run 10.5:1 while using carbs?
OK, so the cams are a straight swap... got that covered.
Anyone have data on using SSI's (with heat) and a 2 in 2 out setup... what size pipe and performance gain?

This whole decission just sucks for me... I have no motor and every way I turn it just keeps turning into about $15K. I think if I go with a 3.0 or 3.2 I can spend the same $15K and end up with a new (rebuilt) engine.

So this is my dillema. Yeah, I know, sucks to be me.

[Steve@Rennsport]

Some thoughts,........

Rich is correct: Europe has FAR better fuel than the current state of pump gas in the USA so the maximum practical limit of CR on single ignition is 9.7:1 (without knock-sensing feedback ignitions). Even then, one must be conservative about timing values and that affects acceleration and throttle response. Bigger bore (3.0+) engines are more sensitive than smaller bore (90mm or less) engines about this due to the offset plug locations.

If one doesn't have 92 or 93 octane gas, I would not go over 9.5:1,.......its better overall to run less CR and be able to use more timing, rather than a higher CR with retarded timing.

The consequences of insufficient octane, too much CR and a tad too much timing in summertime weather will have a severe impact on one's finances. "Less is More".

[fred cook]

After looking at parts and prices, I came up with a required budget of about $17k for a 3.2ss with twin plug heads, PMO ITBs and TEC3 engine management. By using PMO carbs and the XDI direct fire ignition the cost would drop to about
$15k. It would seem that the right thing to do would to either build back stock for minimal cost or go ahead and spend the extra $6 - $8k for the high performance goodies. Anything in between would just be a compromise and probably not a good "bang for the buck". Just my 2 cents worth.

[DYB]

For what its worth, ROW 3.2's had a published 10.3:1 compression not 10.5:1.

Additionally in respect to fuel between USA and other countries, from memory last year a pelican from the UK rebuit his 3.2 motor with the 98mm Mahles and maintained the same 10.3:1 compression.

He was confident on the advice of his engine builder that as long as he ran 98RON he would not have a problem.

[88-diamondblue]

Derek,

Take a look at this thread. Carrera Rebuild 10.3 Pistons & Cylinders. I asked the same question before I rebuilt my engine. Great advice from some of the best in the business. Ended up with 98mm/JE P/C's 9.5:1 with a cam from Camgrinder (Dougherty Cams), SteveW custom chip and a few other things to strengthen the weak links from Porsche. The engine(butt dyno) will be in the 220-225 at the wheels and runs strong to 7000 rpm's. Did a dyno with the cam timing set really advanced and made 151 at the rear wheels. Plan on doing a dyno as soon as I can to verify the butt dyno

The car is a absolute blast from 3900 all the way to 7000.

[village idiot]

Originally Posted by 78SCRSMAN

This whole decission just sucks for me... I have no motor and every way I turn it just keeps turning into about $15K. I think if I go with a 3.0 or 3.2 I can spend the same $15K and end up with a new (rebuilt) engine.

So this is my dillema. Yeah, I know, sucks to be me.

if you're gonna budget for 15k why not a 3.6 swap?

[rebrewer]

Yeah, there's no replacement for displacement.... a 3.6 would be a good starting point.

[78SCRSMAN]

+1 on the 3.6. I've looked at this option too. The dilemma seems to be, 15K for a used unknown condition 3.6 Vram or whatever or 15K for a rebuilt (basically new engine) 3.2. Keeping in mind all of the work will be done by myself. I've got some time to decide as my car currently sits on a rottiserie awaiting various rust repairs, media blasting, and of course paint.
I would be interested in hearing about any known issues or problem areas with the VRam engines. I guess if you're gonna go big ya might as well go as big as you can.

[sp_cs]

Originally Posted by DYB

For what its worth, ROW 3.2's had a published 10.3:1 compression not 10.5:1.

Additionally in respect to fuel between USA and other countries, from memory last year a pelican from the UK rebuit his 3.2 motor with the 98mm Mahles and maintained the same 10.3:1 compression.

He was confident on the advice of his engine builder that as long as he ran 98RON he would not have a problem.

Me perhaps? I'm actually running 10.45:1 measured on 98Ron fuel (=93Mon?) and single plugged. He even advocated running at 11:1 on race fuel - however my first name is Shirish, not Sheikh

See here for more: 3.2 > 3.4 top end rebuild

[rebrewer]

Your calculated CR of 10.45:1 may not actually yield that if you changed cams. Valve timing will affect actual compression.

[DYB]

Yes SP_CS...yours was the build I was thinking of. Thanks for sharing.

Any update on the HP numbers obtained?. Have you had any concerns related to the high compression and the single plugs?

[sp_cs]

Originally Posted by DYB

Yes SP_CS...yours was the build I was thinking of. Thanks for sharing.

Any update on the HP numbers obtained?. Have you had any concerns related to the high compression and the single plugs?

Have a Dyno session planned for tomorrow (Sunday) so will update then - its on a different Dyno to the 269 run I had a while back so not like for like however.

No concerns as such - i have a good supply of 99Ron fuel nearby so always make sure i'm topped up. As per the build thread, the piston shape should also ensure a clean burn as its a relatively flat crown.

I am tempted however, by a wasted spark solution, or fitting an MSD 6AL to maximise the spark, widen the plug gaps and optimise the timing - more research required here.

SP

[sp_cs]

Originally Posted by sp_cs

Have a Dyno session planned for tomorrow (Sunday) so will update then - its on a different Dyno to the 269 run I had a while back so not like for like however.
SP

Just back from the dyno day, figures on a DymTech Chassis Dyno are:

272.7 bhp @ 6025rpm and 246.8 ftlb @ 5098rpm

Again, not like for like, however a car attended today that was within spitting distance of figures attained at a DynoDynamics run earlier in the year

[DYB]

"272.7 bhp @ 6025rpm and 246.8 ftlb @ 5098rpm". Thats a great result. Image what better exhaust and intake would do.

Still not sure I would be comfortable tracking with that compression and with that power the urge for me would be overwhelming.

Great write up you and your brothers car in the Sept issue of 911 world BTW