Hypothetical engine w/ $30k budget: bottom end
 

Lets say that hypothetically you have a $30k budget and want to build a reliable & powerful 3.8 to 4.0 liter air cooled 6
Purpose: mostly DE some street, no emissions or other regulatory concerns

Engine management: Motec w/ itb's, power band in the 5 - 8K range

Lets start w/ the bottom end, case, crank, rods/pistons/cylinders, bearings, oil pump

Where would you start and what pieces (be specific) would you use, what mods if any to the components, rationale is always nice

Bill:

Given the desired operating RPM range and that fact that its going to be a big-bore motor, I would do this:

3.6 case (RSR ones are NLA)
P/C's of choice (bore spigots as needed)
Shuffle pin
GT-3R oil pump
GT-3R crank and crossdrill
Pauter rods
Modify case and center main bearing for the crank mods
JWR rod bearings
Porsche Glyco main bearings (no aftermarket ones)

We make our own ITB/throttle assemblies (46mm or 50mm) and use Motec engine management.

Heads get reworked with our own special RS intake valves (they flow more than OEM RS ones), some port work, and our own P-B guides.

Cams of choice.

1.75" headers for an engine like that and a proper race muffler that incorporates a cross-over or balance tube.

This combo, if properly assembled, works very well,....:) :)

Cross drill the crank, modify the center main bearing. (gets extra oil to 2&5 rod bearings)

GT3 oil pump...Maybe have the bearings DLC coated.

Pauter rods.. Or some Pankl Ti rods if you find some extra change laying around.

Thanks for the input

Thinking of a 993 case just because it already has the oil filter provisions, obviosly won't use the stock p/c and rods, wont use the heads either. The 993 cam carriers seem to be desireable

Gt3 crank, how is a gt-3R crank different? Fewer after purchase mods?

Gt3 oil pump, how is the Gt-3r different?

Pankle Ti rods, looking for the lightest strongest bottom end possible w/ available parts

There are some very light weight Mahles w/ RSR tops and symmetric pin bores that are going to be available soon, supposedly in the pipe now)

is JWR the NASCAR bearings?

what coating?



Cam/valves/ heads will be another discussion along w/ itbs but as long as you brought it up, Steve how do your itb's compare to TWM intakes

I've recently been exposed to a Motec'd 964 w/ some extremely aggressive cams that work well w/ the stock plenum. A truely amazing car, unfortunately limiteed by stock pistons and rods

GT-3 cranks are stronger and use the earlier, (SC sized) wide rod bearing journals.

GT-3R oil pumps have the biggest pressure side and 3 scavenge pickups. There is nothing better, and there are a lot worse ones. An older 930 pump would be an alternative.

Titanium rods are life-limited parts so budget accordingly. :) :)

Those Mahle pistons are available now but in limited quantities. These run very thin rings and are optimized for racing. Good stuff, for their intended purpose.

JWR bearings are not NASCAR ones: these are custom-made, Calico-coated ones that are FAR better than Glyco's.

Our ITB's are much better than ITB ones with far superior linkage, TB position, and two sizes to choose from. E-mail me directly for some pictures.

Common-plenum intakes simply do not function with cams using narrow lobe centers unless ITB's are used below each runner. We've done a lot of R&D on this and have made some of these systems that mimic the 3.8 RSR intake. That factory system works VERY well but has no provision for any air cleaner. We make a common-plenum system based on a modified 3.6 intake and ITB's, but its too small to make big HP on a healthy 3.8-4.0. :)

JWR = Jerry Woods.. they have bearings that are coated by Calico.

The Nascar bearing require a resizing of the rod throw on the crank... this is getting outside your budget.. Clevite makes some of the bearing we use.. they are actually sort of concave in profile.. and hold alot of oil against the crank, which is a good thing...

DLC is "Diamond Like Coating" Calico does it, as do many other jobbers... Casidium is a keyword...

Racecar Engineering has had some articles in the last few months which highlight Nascar teams use of coatings... DLC etc..

I understand that, but you mentioned GT3R crank, which threw me

Again I understand the benefit of the Gt3 pump which I believe also has the 3 scavange pick ups, is the GT3r a different pump or the same one?

What is the life expactancy compared to Pauter? Quite a few engines are showing up w/ Ti rods these days

I know about the current crop but there is another more street oriented version coming.



Good to know, is JWR having them custom made for their shop?

Will do

I understand that too, I recently got a ride in a Motec'd 964, stock intake manifold, some truely racy cams, 993 valves, headers, they use MAP and TPS sensors, the thing is remarkably tractable and smooth given the cams. My direction is to itb's anyhow

yeah, i read Racecar Engineering religiously, wish they included a little more of an amateur oriented slant.

So you think that the JWR coated bearings ins the way to go? Forget the NASCAR bearings that i've seen mentioned?

What kind of horsepower are we talking about here, 450-500?

Ok I looked throught Smartracing and read up on the JWR bearings seems like a good call

One & the same.

Indeed, they are more prevalent and if the motor will see 8K, these do NOT last as long as 4340 steel ones do. Life expectancy is all about how many times the engine reaches or exceeds 8K. IMHO, these things should be regularly replaced as I've seen what happens when they are not. GT-3 Cup engines get new ones every 150 hours and GT-3RSR's every 50 hours.

Yessir, they are.


Magnus,

The ONLY 450-500 HP naturally aspirated Porsche engines I know of are the GT-3RSR ones. The highest HP air-cooled ones make around 415-425 HP and these are all 25 hour engines,...:)

A 3.8 makes anything from 300-425 HP depending on cams, compression, heads, intake system, and exhaust. One's budget & expected engine longevity plays a role in the end result.

Way too big for 6 cylinders. Read this http://forums.pelicanparts.com/showthread.php?t=384230&highlight=efficient+cylind er+size

Sorry not true..

Our 3.8 GT3RSR engine is pushing over 500 hp

We just built an engine for a customer, 3.7L, we don't have much time on the dyno, but we are already at 400 hp.. give us some more time sitting on the dyno rollers, and I see another 10-15 hp

Bill if this is going to be a mixed use engine, ignore the Ti bling, and the resizing of the crank etc..Drilling the crank and modifying the center main will never hurt.

In Bills Uber hp engine we have Pauter rods with many hours on them... they are bullet proof.

We also have recently built a 3.9 haven't put a fire to it yet though..

Matteo's car is a 3.9, right?

The Flying Lizards and Farnbacher are using 4.0 Liter Porsche Motorsport development engines in their ALMS 997 GT3RSRs. They had some great speed at Lime Rock and did well at Mid-Ohio. If not for the disputes over racing line and the frustratingly important pit stops, the Porsches could have done a lot better.

I guess I'll have to disagree w/ you.

I've been living w/ a 3.8RS for quite a while now, it just needs a little more flexibilty in the rev department for some very specific conditions. I could also regear(again) but would rather extend the rev range for other reasons.

The reasons more pistons are often better in terms of specific output are manifold, among them smaller lighter components that are easier to accelerate or decelerate and smaller volumes that are easier to fill in a shorter period of time.

Would an 8 cyl flat 6 be a better power plant than a 6 of the same size? Probably, but given that we live in the real world and have to deal w/ what is available....

Steve/Bill/Tim

Is 400hp achievable w/ $30k in an n/a motor? If so what would be the life expectancy? I'm in motor purgatory too. My car is really well balanced light pretty etc. I'm putting in a g50, would like more hp. It seems the biggest bang for buck is turbo charging. I've seen some pretty sweet dyno charts on single turbo motors, w/ carrera intake plenums, motronic dme' w/ pressure sensing, and twin plug. Torque curves were pretty flat/stable from about 2.5k on (don't hold me to that but I was shocked how much torque was available dwn low and how flat the curves were). Oh and these were running 1bar of boost or slightly less, so I think longevity would be pretty good.


The problem is I like the balance of the car now, and I'm not real psyched about adding a bunch of weight behind the rear wheels. If I thought I could get between 375-400 hp in an n/a motor with out rebuilding it every 50k miles it might be tempting.

ok, requirements are

1) 400 to the wheels *minimum*

2) preferably air cooled

3) no lag; either NA or supercharged (area under the curve is key, so probably an eaton type...i know someone makes a kit but it is bolt on territory only good for 330 or so to the wheels

4) pump gas

5) 75k mile plus reliability on street and track

6) dressed powerplant weight under 500 lbs

what is the budget and what are the probable combinations?

I would guess 3.8 with good aftermarket heads, low compression and custom supercharger tuning with more boost than the off the shelf kits.

I would prefer to get it NA with a 4.2 conversion

I'd love to hear thoughts and real budget numbers.

Ramey,

IMHO, 400 RWHP is simply not possible using pump gas. Further, a 400 RWHP HP N/A engine doesn't remotely come close to a 75K mile lifespan. Measure such things in hours,.... :)

My best advice is to prioritize your list, re-evaluate what is realistic (or not) and define a specific budget because this really decides what will be possible given your resources.

400 RWHP on pump gas usually mean turbocharging and you may not want that.

GT3 RSR case with the oil return holes opened back up, the case itself is slightly thicker.
GT3 RSR or 962 crank with some slight machine work, bearing surfaces DLC coated.
GT3 RSR oil pump.
Pankl (Porsche motorsport) main and rod bearings.
Pankl rod and piston combo, not Ti but designed with a longer rod.
Pankl valves, valve springs and seals.
Jenvey ITB's or adapt an RSR resonance chamber with TB's to an air cooled motor.....
Which Motec?
Coil on plug twin plug setup and staged sequential injectors and two wideband 02 sensors could allow you to run closed loop if the motec is powerful enough. Pectel, McLaren or Bosch are other options that can run on a can bus system to integrate with a logger and dash.

thx steve; that would be getting into serious specific output from under 4.0 NA, but I just needed some input.

I appreciate it. Still working... maybe a SC motor.