Building the ultimate 3.5l motor
 

I am in the process of getting my thoughts in line for a 3.5 l motor build. My 3.2 comes early next year, and want to start sourcing parts. My base ideas as follows:
3.2l motor - case boat tailed
100 mm sleeves
JE pistons - flat top
Keep 3.2 heads basically standard
ITB with with high butterfly injection - 45mm
Crank trigger ignition - twin spark - with individual coils

There are a few points that need to be added here.
The vehicle will spend most of its time at 6000 feet above see level, but will also need to run at sea level.
We will use 98 octane fuel
Car is a dedicated track car.

I need some ideas on compression ratio, was thinking about 12:1, ideas on camshaft selection - like the characteristics of the 993 super cup cams.

The reason for the engine change, is that I currently run a monster 3.2l SS, with super cup cams, and ITB. This motor makes good HP but has peak torque at about 5500 rpm and peak HP at 6700 rpm. I compete against 993 super cups and 964 RS cup cars, and battle out of a corner. I would like to get more go low down.

Ideally I would like to have a motor that has peak torque at about 4500 to 5200 and peak HP at about 6000 rpm. This would allow a motor that is tractable.

The car will eventually be 2200 lbs.

Thanks for the input.

i have just finished building and breaking in a 3.5L

using: 100mm Mahle P&C's (74mm crank)
3.3L euro 930 case
46mm weber IDA's
matched intake manifolds
46/44mm ports
big valves
lots of custom machine work on heads
1 3/4" B&B headers
M&K muffler
twin plugged
electromotive crank fire ignition, w/individual coils and controable advance....


i made 278 (corrected to SAE) rwhp, (~320 crank) and there is at least another 20-25 on the table, that can be had with cam timing (which is presently a stock s-cam, @ stock timing) running a little rich

its hp peaked @ 6100rpm, torque was low ~5500rpm.
to say that it is tractable is an understatement, it pulls from 2000rpm hard to 4000, and from 4000-upper 6000'd better be reaching for the next gear.

as a pure race car u would obviosuly use ALOT more cam, as even i need mroe, basically i'm not using my avaible air flow.....
unbeknownst to me my mech decided to double up on head gasket spacing , making it between 9-10:1cr...i had planned on 12:1 , and with that according to bruce anderson it should be 330hp with stock cam and weber settings....

keep us updated on your build

Re: Building the ultimate 3.5l motor
 

Talk to John Dougherty (drcamshafts.com) about cams. 12:1 seems hard to do with Carrera heads, I guess it will depend on your planned deck height. I would probably run about 10.8:1, any cam like the Supercup, DC20, etc., build pretty high dynamic compression ratios.

Is your ITB setup 45mm at the head port?

Keep in mind the displacement increase will make the cam seem a bit milder because the 3.5L engine is moving more air overall at a given RPM (vs. 3.2L S.S.). Not to mention, the 3.2L 74.4mm-stroke crankshaft will lend itself better to low-end torque production.

Sounds like fun.

-Scott

The 45mm ITB is at the butterfly. This will taper down to the 41mm at the head.

I will be using Georges headers (European racing) as we are not able to get proper equal length headers here. They will be the 38mm ID ones.

Where would you guys expect the peak HP and torque rpms to be.

What would the expected flywheel HP to be.

I am also looking at running full sequential fuel injection, from the new Wolf V500 ecu.

1meansc.....

I'm not well versed regarding cam combinations for your engine, however, but based on your desire, I do know that to get more torque down low you need to increase displacement as much as possible and decrease the cam overlap.

Has any one tried a turbo cam on a large displacement engine and dynoed the combo?

I also agree with one of the other contributors, 12:1 compression is a bit high if your ultimate quest is to have a reliable torque monster.

I know that the following statement will get me in trouble, nevertheless, HP rules the straights, torque the corners, the rest is gearing.

Just my .02 cents.

I think if that high a compression motor if your goal- you better be looking at JE's with deep valve pockets.

You could use a crank from a 3.6L, for even more low down torque ;)

I was going to go for the 3.6 crank with my existing 98mm sleeves.

From what I have heard on this board, there are not a lot of supporters for the 3.6 crank, especially without the harmonic balancer and dual mass flywheel.

So I decided to make a 3.5 with a 3.2 as a base.

Just don't use the 964 crank...PM me if you want details on other options for a 3.6 crank. :)

Share your wisdom.... :)

Cheers

With regards to cam selection, I have seen on other posts that people suggest a Mod-s cam for similar builds. Anyone with ideas on this.

if by mod-s u mean a slightly modified s-cam, and i believe the 'mod' is mroe duration, no change in lift, then thats actualyl what i am using, however i have been told for timing purposes it is bascially an s-cam. and if this is the case, in a race car i would defintly want the cam to come alive at higher rpms.

My reason for wanting to keep RPM down, is durability. I don't want a low hour motor. I am prepared to do a top end rebuild every year or two, but budget does not allow full overhaul every year.

I have run my very quick 3.2 SS for two years now. Pulls like a steam train all the way up to 7200 redline. I have only reconditioned heads and replaced rings at the beginning of this season. Motor still sounds better than most, and possibly one of the quietest 930 based Porsches that I have heard. This with JE pistons.

I also want to try to design the peak RPM low, to allow for the possibility that the actual peak torque and HP are a little higher, at least the motor will be able to run there.

I will be using Johns racing springs & retainers, with his recommended cam. The rest of the motor will be made to run to 8000 rpm if necessary.

Thanks for the ideas and comments guys.

P.S. Scotts ideas are great, but budget would not allow the crank options.

you have a pm.

Scott,
What's your info on the 964 crank?

Well, this build has started. There is a year of dreaming, 6 months of design and 6 weeks waiting for parts.

The first of the parts arrived on Saturday.

The build is as follows:
3.2 carrera case and crank
Pauter rods
100 mm JE high comp pistons
Re sleeved 100 mm cylinders
GT3 Oil pump - man this thing is huge
Johns cams & racing spring & retainer kit
3.2 ported heads, twin spark - just cleaned up, not made any larger

The custom throttle body intake will be ready in one week.

Ignition & fuel will be controlled via Wolf V500, running sequential fuel injection, and wasted spark ignition.

Build will be documented on this site.

Another approach.
3.5 MFI 369 RWHP 352 F/lb 112 octane fuel
Functional RPM range 4500-7800
Mahle 100s
RSR sprint cams
930 crank 74.4 mm stroke with 3.0 rod lournals
3.0 SC rods with ARP bolts
930 oil pump
50 mm Silver Line intake valve
42mm Silver Line exhaust valve
41 mm intake ports
41 mm throttle housings
54 mm intake stacks custom build @ Supertec
RSR MFI pump conversion
Supertec Valve springs
Aasco ty retainers
Custom Distributor MSD AL6 with Blaster SS coil
European Racing headers

http://forums.pelicanparts.com/uploa...1177888951.jpg
http://forums.pelicanparts.com/uploa...1177889355.jpg
http://forums.pelicanparts.com/uploa...1177889108.jpg

Henry, that looks great.

What compression ratio are you running on that motor?

How often will you have to rebuild it?

I am prepared to open mine at the end of every season for a check. My idea is to strip top end every season and split the case every other season.

I am hoping for a little less Bling with my motor, but should be close.:D

Well, as promised i will post a couple of pics of the new motor.

I started with a 3.2 "long block", but this was covered in another thread.
http://forums.pelicanparts.com/uploa...1181795000.jpg
The case was cleaned and a "small" GT3 oil pump fitted. Note modified centre main bearing.
http://forums.pelicanparts.com/uploa...1181795105.jpg
100 mm JEs fitted to reconditioned 964 sleeves. Plenty of heartache here to get everything to fit. People tend to leave out a couple of points when they describe their work.
http://forums.pelicanparts.com/uploa...1181795214.jpg
Then assemble the rest of the long block in an anti-bling fashion. Note: Old motor had a red fan & shroud, black fan housing and looked like a Christmas tree. A nice Christmas tree none the less.
http://forums.pelicanparts.com/uploa...1181795334.jpg
http://forums.pelicanparts.com/uploa...1181795433.jpg
Not bad for one months work, from dirty incomplete long block, to what I have now. Hopefully the remainder of the induction will be fitted today, and the custom HT leads will arrive. I hope to have the motor in the car and started today.
I have also realised that sleep is not important in the quest for Pure Porsche Power.

wow!!!!!! simply amazing

1meanSC, can you please sum up all of the specs you are building to and abviousley, you must tell us how it runs/what it puts out when completed! Cant wait for your results. Any rough $$#'s on what these parts will/have cost you?? (I probably cant afford it AND I know I cant affords Henry's heart stopper posted above)
ALso, whan you say you are willing to open top end 1x/yr and lower end every other yr, what kind of hrs will the motor have seen and is this ALL race or 50/50 street/race??
Thanks a lot!!
Keep up the great work! Bob

The motor is as follows:
930/21 Case & crank
Pauter rods
High comp JE pistons
Slightly modified 3.2l heads
RSR style flywheel with Sachs sport clutch
964 3.6 turbo cooling fan
A set of wild cams from John with his retainer & racing spring kit
Custom long intake runner throttle body injection
Twin spark with six double pole coils
Sequential fuel injection

The cost is about 50% more than expected. This is mainly due to the budgeted motor was locally available during budget time, and the motor was sold, by an acquaintance, just prior to the build started. The additional cost was involved in importing a 3.2l core motor, that turned out to be very incomplete. They ever removed the studs on the front and rear of the motor, that hold the gearbox and front engine mount assy.

The motor will be fitted today, and will hopefully run today as well.

I will post the results once the motor is tuned. Remember that we are 1800 m above see level. We need to work hard at getting any power op here. A good 3.2l will make about 110 to 120 kw on the rear wheels.

Thanks for the interest.

Hi Markus.

I am reading this with great interest and have a few ideas for my car that I want to talk about with you but it will only be towards the end of the year. What management system are you going to use?

P.S. I think what you have done is really impressive.

Craig

How much tq are you looking for? My dads car runs a 3.3 short stroke that made 297lb ft at the rear wheels. The hp numbers arent terribly impressive but the tq is fantastic and goes on for days. I really think peak hp is completely overated for street and track cars. A powerband that you can use is so much more valueable than peak hp anyday.

If your talking about an ultimate 3.5l motor there are tons of things to take into consideration. How much does the car weigh, what gears will you be using, what kind of driving, how deep are the pockets, how ultimate do you want to get and all that.

When you talk about using 100mm sleeves what do you mean? Are you going with new aftermarket 100mm cylinders or boring out something you have? After using JE pistons in my dads motor I have to admit I was extremely disappointed with them. The weight, design, quality, actual CR were a bit off from what was expected but you get what you pay for. Next time its either Accralite, Pankl(CP in socal) or Cosworth. As for rods we went with stock 3.0 sc rods, fine enough for the revs this engine sees, although when it gets bumped to a 3.5 it will either be Cosworth, Pankl or Arrow.

Right now we have stock crank, stock rods, stock pump, stock 78sc heads, ssi exhaust, Jenvey intakes, Autronic electronics, Bosch MS injectors, DC camshafts, springs and retainers, stock valves and guides.

The next steps include, GT3RSR pump, hogged out 3.2 heads, equal length headers with v bands and a custom muffler, hotter cams, custom pistons and rods, lightened knife edged and different rod bearing sized crank, polished case (inside), custom valve covers for coil on plug, higher performance injectors, full sequential, bespoke intake, bespoke airbox, different valve sizes, different guides, coatins, polishing, shot peening and all that. Hoping to see a very nice tq curve and decent top end power.

At the end of the day its a hot street car, then when I really think about it I could buy a 996 turbo motor from a totalled car and build it into a gt3 r/rs/rsr kinda clone and have gobs of power and tq for about the same money. Turbo(s) well maybe one day.

Dont be disappointed if you dont make gobs of hp, just hope for a flat and fat torque curve.

It's worth mentioning that the JE's are only as accurate as the chamber volume used to come up with the dome height. That's the problem with off the shelf JEs. When if at all possible, whomever you buy your pistons from, measure your heads first and ask them to use that measurement when calculating the dome height/volume necessary to get your desired CR.

Additionally, JE can make a lighter piston, they just charge about ~$20 more per piston for machining and ~$10 more per wrist pin for their lightest tool steel pins. Additionally, if you do lighten the piston, I always thermal barrier coat the crowns for added safety, which adds about ~$50 a piston, doing the skirts and ring lands too.

A 3.3 short stroke, 3.5, or 3.7 is all about torque. Sure, you can make gobs of HP with a big cam and head work for a race engine, but these engines are all about having lots of torque and great driveability across the entire rpm band.

As mentioned in the first post of this thread, I was looking for a motor with a lot of torque.

I also wanted this to be based on a 930 case, to keep within what was basically era correct. The balance of the motor should allow for a motor that is not scared of reving.

The piston and rod combination has resulted in a 222 gram reduction per cylinder, based on a 3.2 l. The RSR treatment of the flywheel, should make a motor that revs up nicely.

The cam selection was done under the advisement of camgrinder. I gave John the build specs, as well as the fact that I am running standard 915 ratios, in a 2180 lb (wet) car. The cam is a "big" cam, that will give a lot up in the top end of the rpm range. The high compression should help with the "off cam" portion of the rev range.

Remember that at our altitude, the air is less dense, by about 15%. This means that a 12:1 compression ration equates to 10.2:1. I do seven races a year at this altitude, and one race at sea level. I may have to use an octane booster at sea level, or bring the timing back. But this was part of the spec.

I also do about 10 time trials and at least one fun day a year, all at high altitude.

I have had problems with my HT lead supplier, as these are custom. I will only get them on Tuesday.

Motor will be dynoed up to about 6000 rpm during the next week, and I will have a track session Tuesday week. After this session, we will do the full rpm dyno, possibly to just under 8000 rpm.

I will post the dyno results here.

Cheers