Cam profile - 3.2 with ITB
 

Hi,

I have a 3.2 that I am building to fit my 914-6 GT build.
I have upgraded oil pump and rods, but keeping the std pistons/cylinders.
Will be running EFI, twin plug with COP and ITB

I have bought 964 cams, but am thinking maybe to grind the SC/3.2 cam to a better suited profile.

As I understand 993SS or DC21 cam profile is the most aggresive one can have on the std 3.2 pistons.

What profile would be perfect for this build?

Yes aware of Dougherty site
Will be regrind here in Norway.

But looking for experience or suggestions

Ever think of calling him?

more information and pictures please
 

Good morning Norway - is the 3.2 engine from a 1984-1989 G series 911?

Can you post a pictures of the pistons you are using?

What is your estimated compression ratio?

Regards,
Steve

He’s using stock pistons.

If you are using standard pistons you are quite limited in your selection. I would say its not worth the upgrade from the stock cams.

totie- Didn't you post before nearly the same question?
One major benefit of the ITBs is the ability to run much more camshaft, meaning overlap, to help midrange and top end power, and still have great drivability to boot round town. Yet you chose to keep stock pistons which don't allow much of a cam . Thus you cannot take advantage of the increased airflow possibilities through the cylinder and heads from using ITBS. If you are on a major budget crunch, pull it apart and cut valve pockets in your stock pistons, and you will gain something for certain w a moderate cam, say a Mod S. Bare in mind your stock 3.2 USA pistons CC at barely 9:1 when all is measured, and a 10.3:1 Euro 3.2 is only 9.5:1 max with a 90-91 CC head. So these are NO where near advertised on compression. You will lose a far bit of compression additionally by cutting required valve pockets.
Hopefully you see now don't be a "half way dude" and get some well designed pistons at 9.7 ish to 1 with proper valve reliefs designed in. Then you can get a modern ring pack and other features (not to mention new xlnt cond. parts ) to get all you can . Otherwise, call Laurie at Web cam and ask what is the "most" cam you can fit in there w stock pistons. Likely it's a 993 super sport is my guess... A guess because we don't do half way engines...

Regards
Kevin
GAS Motorsport

993SS will work, if you set the timing right. But its not an upgrade worth the money. I have that combination of ITBs and 993SS.

Hi Steve,
Std euro 1986 3.2 piston/cylinder. So that would be 10:3 as I remember from the euro spec

Hi Kevin,

Thank you for the input.
Usually not the "half way dude" :-) , but bare in mind that this engine is for a light 914-6 build, so basically not aiming for the 300hp here.
Building 2 x 930 engines at the same time, that has taken a lot of the budget as well.
My goal for the engine is to raise the power from 231 stock to somewhere 260-270 hk, and this is obtainable with stock piston/cylinders.
Just looking for the best match to the P/C that I have

Hi Tutle
Didn't want to seem to be busting your chops and I get it , costs pile up. You spent good money on ITBs and an ECU & harness, etc, plus a bunch of time will be spent making it all go together and work well -meaning drive nicely, stout performance, be reliable. To not put a moderately or more than a moderately sized camshaft in it , will not take advantage of the increased Volumetric efficiency that the ITBs can provide midrange and up. Keeping in mind these engines are just an air pump, and simply speaking if the valves are closed the engine will not do a great amount of breathing.
These 3.2 pistons( yes they are no more than 9.4:1 stock if Euro ) look like the surface of the moon and clearly Porsche did some work designing them to get a good A/F mixture homogeneous & over toward the single spark plug more effectively. This is why I suspect you will need quite alot of valve relief on the intake side. Whomever said it wasn't worth it I think was modifying a 3.6 L and that piston looks totally different( more like a reverse dome-great for twin plug) plus I recall they retarded the cam timing a bunch to fit them in without hitting. Thus not much of that applies to your situation, plus unless they did the engine with a stock cam, tuned it all then dyno'd, then did it w the Cam option 2, tuned it and dyno'd, one wouldn't really know what the cam change as installed was really worth. Worth saying that retarding the timing more than a degree or two likely means it is just the wrong cam.

If you cut the required valve reliefs for a moderate cam, Mod S a good choice, your compression would suffer quite a lot I think , 9.4:1 ish or less now (did you CC your heads I could calculate it for you as we've used stock euro pistons many times in a certain race class we had to be 9.5:1 in) down at least .3-.4 of a point compression perhaps more. Then you are staring at a 9:1 hotrod, wondering why you wasted the dough and didn't just leave the stock motronic on it....Coincidentally we have a set of 95 MM SC pistons(roughly some dome design) that came from a friend's estate that look like someone went to the same machine strum with deep reliefs cut in them, and through-the-towel-in on the idea. I'm in a similar boat on a 3.5 L Motronic engine I built for one of my streeters...But different. I kept the stock motronic injection , made a custom chip based on dyno x 2 , changed the cam 3 times, moderate(pretty good) to more than moderate(too much for the compression ratio and intake) and overdid it- lost power, then went back to custom moderate middle, and haven't dyno'd again yet. It feels better but nothing like The 3.5 L ITB engines we've done for other hotrod streeters. Given all the dough I have in this custom lump, The Motronic plenum intake just holds it back too much above 5800-6K and when I get time I am going to fit our ITB and Motec package on it to get all the performance that is waiting there.

These follies are why I suggested to change the pistons. It's like building a house on a hill w a great ocean view, then not putting any windows or glass doors on that side of the house LOL.

Good luck.
Kevin
GAS Motorsport

This is why I say its not worth it.
Stock 3.2, except for headers, with large ITBs and. Nothing done to the pistons.
Stock cams vs 993ss cams. Same dyno, maybe two years apart.

http://forums.pelicanparts.com/uploa...1732627095.jpg

Safe just said it with solid proof.

Hi Safe -it’s great to have data. Are you the person who had to retard the cam timing quite a lot as I recalled? Didn’t recall it was a 3.2 L Motronic engine.
But where’s the Tqe curve? As being better, making more power is
Not only about a HP number . Plus this actually looks like the same engine ( did they select the correct files to print?) with less than optimal and more optimal ignition timing as HP curve shape is nearly exact ? A 3.2 plenum in every engine ( more than a few handfuls) we have done , many different config’s -high compression, medium compression, stock cams medium cams and huge cams, stock heads trick heads, makes it peak power near 6200 rpm and falls in varying steepness after, due to the manifold’s resonance . This engine ( stk 3.2 you show) keeps climbing even up to 7 K with no fall off. The plenums also broaden the Tqe curve significantly which is why most engine have these today for the street as it makes broad drivability , much more Tqe at say 3K-5 k where we spend 90-95 pct of our time on the street. This comes at a cost in top end as everything is a trade off in engines. If your engine had more Tqe at 4 K w plenums it would show in the hp curve obviously as this is simply a calculated number based on Tqe measured.
Did you retard your 993 Ss cams and to where to not hit the pistons?

Thanks
Kevin
GAS Motorsport

I never had a 3.2 plenum on this engine, so I can't compare the power or torque to that.
Torque isn't on this print, but it's less everywhere. It's the right graphs.

This is the original dyno sheet with torque.

http://forums.pelicanparts.com/uploa...1732635638.jpg


Long ago now so I m not sure I remember correctly, but I think I set the cams to the manufacturer spec, maybe 1.6 ?? Later I changed it more towards the stock 3.2 spec 1.2mm?? And regained some power, but not up to the original.
But that is probably 10 years or more ago now.
It goes to 6800 every shift, it's been mostly a track car for the 20 years I've had it.

Well darn Safe
I thought you said stock 3.2 L , not a stock cam only from a 3.2.
Where did you time the 993 SS cams?
So anyhow thx for more info and you may rev that thing another 500 rpm as at 6950 ish it is still going up, likely would make 10-15 more hp and keep you in the range of broad HP when you shift back down to your split or drop Rpm, you know “ more area under the curve” power level so pretty disappointing for ITBs and 3.2 . But it is very hard to compare Dyno’s. Your a/f is bit more all over the place than we’d like to see . Perhaps something small can be gained there.

Good luck for another 10 yrs!

Kevin
GAS Motorsport