3.6 vs. 3.2; Again

jamesjedi · 02-15-2011, 04:47 AM

I was at a local high-end race car builder yesterday. He was saying that the 3.6 is not that great a motor. I do not wish to wrongly quote him, but there was reference to its not being able to rev very high (7000 rpm), and I understand that. But the 3.6 does not have to rev to 7000 to get good HP/torque. He said I should get a 3.0, and make 3.2ss, or similar motor.

I would like to ask him more, but I only had a few minutes to talk to him. He does build very expensive race motors. Is it when the engine has "everything" done to make it faster and better that it becomes a better engine than a 3.6?

I wanted to say that a 3.0 performance build would not be as reliable as the 3.6 displacement would be. Or is this a case of "it depends". Both motors could put out similar numbers. Or, am I missing something?

Steve@Rennsport · 02-15-2011, 07:52 AM

JMHO,.....

3.6's are every bit as good as a 3.2, IF they are properly spec'ed & assembled. Its all about the attention to details and using the proper components based on how the engine will be used. In some cases, building a high-powered 3.6 can cost more money, but thats dependent on the application. Reliability & durability are both excellent provided the correct components are chosen and installed correctly.

In the context of street usage, both engines are very good performers, with the nod to the 3.6 simply based on torque. "There is no replacement for displacement" insofar as street motors go,....

jamesjedi · 02-15-2011, 08:11 AM

There is reference to 3.6 race motors built in Anderson's 911 Handbook that are simply cams and exhaust, maybe an engine management system. It looks like a 3.2 would need considerable work to have similar numbers that the simple 3.6 race motor would have. I understand that the 3.6 does not tolerate the high revs that a 3.2 would, but the motor looks like it could perform better at lower revs. than the "built" 3.2 does at 7000rpm. It does this with better torque/HP.

Maybe what am saying is that the 3.6 does not need to be run at 7000, it has good numbers in the lower range, and a very good number when it comes to HP/torque in the 6000 range?

Steve@Rennsport · 08:20 AM

Quote:

Originally Posted by jamesjedi

There is reference to 3.6 race motors built in Anderson's 911 Handbook that are simply cams and exhaust, maybe an engine management system. It looks like a 3.2 would need considerable work to have similar numbers that the simple 3.6 race motor would have. I understand that the 3.6 does not tolerate the high revs that a 3.2 would, but the motor looks like it could perform better at lower revs. than the "built" 3.2 does at 7000rpm. It does this with better torque/HP.

A stock 3.2 doesn't handle 7K RPM any more than a stock 3.6 does.

The 3.6 performs better due to difference in displacement. One cannot compare the HP/Torque curves of these motors, especially a "built" 3.2 that will make power to 7K as these are totally different.

Quote:

Maybe what am saying is that the 3.6 does not need to be run at 7000, it has good numbers in the lower range, and a very good number when it comes to HP/torque in the 6000 range?

True,......all other things being equal, larger engines will always make more torque everywhere in the RPM range than an equivalent smaller engine will. For street use, torque is King.

Where is gets complicated is when you factor throttle response. Installing ITB's (carbs or EFI) make any engine feel a lot different due to major changes in throttle response, compared to any OEM, single-throttle intake system.

jamesjedi · 02-15-2011, 08:19 AM

Thanks Steve.

Bill Verburg · Bill Verburg's Garage

I agree w/ Steve 100%, stock whether its a 3.0, 3.2 or 3.6 they are all rev limited to 7k or less, they can all also be built to revs far higher by the liberal application of art and cubic dollars. the rev limit is proportional to log(9$)

for a prime example look at the singer 3.6/3/8/4.0 that will rev to 8k or look at the late 3.8L Gt3 Cups that can spin to 9k,

the Singers and Gt3 Cups use essentially the same bottom end and oiling, but the smaller lighter valve train of the Cups allows for better breathing and power up high

jamesjedi · 02-15-2011, 12:34 PM

"they can all also be built to revs far higher by the liberal application of art and cubic dollars. the rev limit is proportional to log(9$)"

Well said!

I really like the 3.6. It seams well suited for someone like myself that will not do 10 races a year, or is concerned about building to meet the class rules. I do want it to be fast on the track, and have it beat cars that cost much more at Solo1 or time attack.

Thanks

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by jamesjedi

"they can all also be built to revs far higher by the liberal application of art and cubic dollars. the rev limit is proportional to log(9$)"

Well said!

I really like the 3.6. It seams well suited for someone like myself that will not do 10 races a year, or is concerned about building to meet the class rules. I do want it to be fast on the track, and have it beat cars that cost much more at Solo1 or time attack.

Thanks

us air cooled guys are fighting a losing battle, much as I love my cars they are antiques that will never be able to keep up w/ well driven Caymans, Boxsters, 996, 997 etc. sure cubic $ make them better but in the end the same cubic $s thrown at a modern chassis will be that much better

It's like all the guys that are still driving their '69, 73 pick a year, great cars and loads of nostalgia but the state of the art has moved on, you enjoy them for what they are.

PFM · 02-15-2011, 06:24 PM

Yes RPM = $$$$$ to build initially but RPM = Service as well. As the RPM increase so does the service interval and the reduction in long term reliability. High RPM parts and the motors they live in need more care period.

So if 300 HP trips your trigger getting it from a 3.6 or 3.8 at 7000 RPM will live longer than a 3.0 at 300 HP and 8000 RPM. Both make 300 HP both fun to drive.

Just my 2 cents worth,

And yes I am building a 3.0 for other reasons, would have done a 3.6 and been on the track long ago if we lived in a perfect world.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by PFM

Yes RPM = $$$$$ to build initially but RPM = Service as well. As the RPM increase so does the service interval and the reduction in long term reliability. High RPM parts and the motors they live in need more care period.

So if 300 HP trips your trigger getting it from a 3.6 or 3.8 at 7000 RPM will live longer than a 3.0 at 300 HP and 8000 RPM. Both make 300 HP both fun to drive.

Just my 2 cents worth,

And yes I am building a 3.0 for other reasons, would have done a 3.6 and been on the track long ago if we lived in a perfect world.

If I catch your drift correctly I'll have to disagree

hp comes for mixing 2 ingredients(never mind how you derive the 2)

hp comes from torque and rpm. Torque up high in the rpm band makes more hp than torque down low in the rpm band. The shape of the torque curve is important as you need area under the curve(doesn't matter if you are talking hp curve or torque curve as they are intimately related)The bigger the displacement the more torque across the entire rev band

yes you can build 300hp 3.2 but the engine will need to rev higher and the hp curve will have less area under it than a 300 hp 3.6

I disagree w/ the service interval, the more revs the more service has been my experience

winders · 02-16-2011, 07:16 AM

Quote:

Originally Posted by Bill Verburg

I disagree w/ the service interval, the more revs the more service has been my experience

You guys agree....

He meant an increase in the frequency of the service interval, not the time of the service interval.

You can tell that based on this text:

"...a 3.6 or 3.8 at 7000 RPM will live longer than a 3.0 at 300 HP and 8000 RPM."

Scott

PFM · 02-16-2011, 07:01 PM

Yes I flubbed a bit High RPM requires more maintenance not less, you service a high RPM motor more often.

KTL · 02-17-2011, 08:48 AM

For average Joes vying for a $5 trophy, I say build a good reliable engine that provides a decent amount of power for your class. What you don't spend on the engine for that extra 10 HP and 500 RPM, put it in the suspension. Depending on your tracks, HP & TQ isn't always King (I suspect that's why Steve said "on the street" its King) and if you're carrying more cornering speed than your competitors, you're somewhat negating the extra HP your competitors have.

I'm all for a great engine (can never have too much power, right?) and I totally appreciate the question of a 3.2 vs. 3.6 because its a very valid one, for more reasons than just the actual displacement. I have a GTS3 3.0L that i'll likely bump up to a 3.2 when the time comes for rebuild. Currently I run against guys with GTS4 3.3L (100mm bore from a 3.0 base) in a '70 widebody chassis and GTS4 3.6L 993, 964 engines in '75 & '92 narrowbodies. Mr. 3.3L blows our doors off because he carries so much speed through the corners (true Hoosier slicks help, but so do the size of his cajones/talent and well setup suspension) on top of the 250 WHP of the engine. I was able to finish ahead of the 3.6 guys on account of my cornering speeds, which are notsogreat, and not necessarily suspension and tires since we're ~ equal there. They'd run out on me on the long straights, so it had to be my cornering and braking. I suspect the 3.6 guys will be on their game this year after seeing Mr 3.3L EASILY destroy us last season.- he lapped me every event except one. So i'll have my work cut out to not be the last 911 in the field, and my goal is to not get lapped by him this season!

I do understand this is the engine forum....... Just saying don't make it your only intense focus. Suspension, tires and trans are along for the ride too! Finally, the driver has to make it all go.

There's cars with less power & more weight in the GTS2 class below me that consistently beat me quite well last year. Raw power is great, but its important to optimize your suspension setup and most importantly you really have to be able to drive the heck out of the car to be competitive!

jamesjedi · 02-18-2011, 02:07 PM

I am not a racer, but I have seen what you are talking about first hand when it comes to the extra 10 hp, or if you are restricted to a max. hp. Some will spend crazy money on the engine to either get the extra 10 hp or have your car reach the max. torque/hp sooner.