96x71 or 96x78 motor - That's the question Options

[KenH]

In playing with my el-cheapo dyno program it looks like you can get the same HP with either a 71mm or 78mm stroke. The 78mm however gives a bit more torque.

Over all the CAM seems to give the biggest improvement.

The question is - is it worth the hassle to go to 78mm stroke (T1 rods, special pistons, clearence issues, cost of rods, crank, pistons) for 10'lb of torque??

Looks like 96mm x 71mm with good heads, proper CAM, optimun fuel delivery, FI or Carb, will make a pretty good motor.

Comments??

Ken

[So.Cal.914]

Torque is nice but the shorter stroke is going to rev higher. And the 96x71 should be more reliable.

[Twystd1]

It really depends on your end result.

What are you looking to do with this car when finished?

It's all in the package...!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Give us some more data to work with.

Twystd1

[Mark Henry]

I'm sorry but those desktop dyno programs are most of the time BS.
Just sticking a great big cam in an engine is about the biggest mistake an amateur engine builder makes.

There is no replacement for displacement.

and

Your engine is only as strong as its weakest link.

[KenH]

This is the set-up.

96mm pistons
44 webbers - 36mm venturie
4 to 1 headers, Phase 10 muffler
WEB CAM 86 - not firm on this yet
Heads upgaded to 44 x 38
So is it worth $1000 to go to a 78mm crank over the 71mm crank??

This comment below needs more to go with it to be of value.

"There is no replacement for displacement.

and

Your engine is only as strong as its weakest link."


Ken

[anthony]

Raby has graphs posted for all his engines at www. aircooledtechnology.com. You can use them a base of comparison against each other. The difference between his 2056 Daily Driver + and his 2270 Peformer is pretty substantial. Hope the chart works:

Torque
rpm......2056.......2270
2000......104.........129......+25
4500......130.........162......+32
5500......119.........144......+25
6000......104.........135......+31
6500.......?............122......+


HP
rpm......2056.......2270
2000.......40..........61........+21
4500......112........139.......+27
5500......125........151......+26
6000......104........154......+50
6500.......?...........151......+


To me the 2270 is clearly in a different league than the 2056. I did take a ride in McMarks 2056 equiped car with a mild cam. He dynoed it at 90hp at the wheels which would be about 105hp at the crank. I can say that it made the car move nicely - much much faster than my stock 160k mile 2L engine. To me his engine made the 914 feel like the car it always should have been. Still, I can't stop thinking that a 2270 would make the 914 faster than my 911SC and be comparable to most six conversions.

(IMG:http://www.aircooledtechnology.com/type4/914/2056_daily_plus.jpg)


(IMG:http://www.aircooledtechnology.com/type4/914/2270_performer.jpg)

[BMXerror]

"There is a replacement for displacement. It's called good engineering."

Displacement isn't everything, but you are rather limited on how much engineering you can do when you're using someone else's design. My quote isn't completely true either, but it's what I say to people who only think bigger is better. That's why Porsches modern 5.7 liter engine has almost twice the output of Chevy's modern 5.7 liter engines. 78mm WILL give you more torque, but unless you're going with longer cylinders and/or severely offset wrist pins, your rod angle is gonna go to hell. This will cost you in reliability to bottom end as well as the extra wear on your rings. It will also cost you the ability to rev, as I think someone mentioned, AND some tourqe perportionally to the length of your stroke.
As Twystd1 said, it all depends on what you're using it for. If you are concerned about cost (as many of us are), it sounds like you're not going to want the rebuild the thing very often. In that case, I would go with the 71mm stroke. However, if I was building a drag motor, especially if it were forced induction, then I would go with the extra torque and displacement at the expense of some reliability. MY OPINION.
Mark D.

[Mueller]

"There is a replacement for displacement. It's called good engineering."

Displacement isn't everything, but you are rather limited on how much engineering you can do when you're using someone else's design. My quote isn't completely true either, but it's what I say to people who only think bigger is better. That's why Porsches modern 5.7 liter engine has almost twice the output of Chevy's modern 5.7 liter engines. 78mm WILL give you more torque, but unless you're going with longer cylinders and/or severely offset wrist pins, your rod angle is gonna go to hell. This will cost you in reliability to bottom end as well as the extra wear on your rings. It will also cost you the ability to rev, as I think someone mentioned, AND some tourqe perportionally to the length of your stroke.
As Twystd1 said, it all depends on what you're using it for. If you are concerned about cost (as many of us are), it sounds like you're not going to want the rebuild the thing very often. In that case, I would go with the 71mm stroke. However, if I was building a drag motor, especially if it were forced induction, then I would go with the extra torque and displacement at the expense of some reliability. MY OPINION.
Mark D.

did you see the graphs above?

have you read any postings of Raby's about his motors or these combos??

I gather not...the Type IV really seems to wake up with the additional rod length without any real negative effects. As for the Porsche 5.7 putting out 2X that of the Chevy 5.7??? What are you smoking??

[Andyrew]

Cough, LS1, LS6...


end cough.

[Dominic]

[quote name='BMXerror' date='Jun 13 2006, 04:23 PM' post='702860']
"There is a replacement for displacement. It's called good engineering."

Displacement isn't everything, but you are rather limited on how much engineering you can do when you're using someone else's design. My quote isn't completely true either, but it's what I say to people who only think bigger is better. That's why Porsches modern 5.7 liter engine has almost twice the output of Chevy's modern 5.7 liter engines. 78mm WILL give you more torque, but unless you're going with longer cylinders and/or severely offset wrist pins, your rod angle is gonna go to hell. This will cost you in reliability to bottom end as well as the extra wear on your rings. It will also cost you the ability to rev, as I think someone mentioned, AND some tourqe perportionally to the length of your stroke.
As Twystd1 said, it all depends on what you're using it for. If you are concerned about cost (as many of us are), it sounds like you're not going to want the rebuild the thing very often. In that case, I would go with the 71mm stroke. However, if I was building a drag motor, especially if it were forced induction, then I would go with the extra torque and displacement at the expense of some reliability. MY OPINION.
Mark D.
[/quote


(IMG:style_emoticons/default/bs.gif)

Please do yourself a favor and read a little on the topic before you waste all that time writing B.S.

Enjoy!

http://www.aircooledtechnology.com/vw_2270t4torquer.htm

[Mueller]

Ken,

The motor I sold to Mark Henry was going to be a 94mm X 78mm engine. (still should be since I think Mark is putting it together with all the components I sold him)...Jake helped me with the selection of components, the idea was that with the stock 2.0 heads I had, the extra stroke and smaller bore would allow the cylinders more time to ingest the air/fuel mixture. With the cam spec'd by Jake, he thought 160hp was not out of the question...very similar to the 2270 posted above, but with the bone stock 2.0 heads, probebly lacking a little here and there....still would have been a fun motor...

[KenH]

First - Let keep this discussion civilized, everybody is entitled to their comments. To many of these threads go off course do to non-technical comments.

Any way - my Dyno program my not give an accurate HP number, but it should be OK in showing changes up or down. For the same CFM, CAM, BORE, EXAHUST, C/R changing only the STROKE the HP stay about the same but with more TORQUE for the 78mm Crank over the 71mm.

Ken

[Mueller]

First - Let keep this discussion civilized, everybody is entitled to their comments. To many of these threads go off course do to non-technical comments.

Any way - my Dyno program my not give an accurate HP number, but it should be OK in showing changes up or down. For the same CFM, CAM, BORE, EXAHUST, C/R changing only the STROKE the HP stay about the same but with more TORQUE for the 78mm Crank over the 71mm.

Ken

Does the dyno program plot out the VE of the proposed combos?

[BMXerror]

Since when did Raby's articles become the VW bible? No offense to Jake, but he's still a human being. He has his opinions on the way things should be built and I have mine. And as with everything to do with technology, there's more than one way to solve a problem. So.Cal.914 asked our opinions. I gave my opinion. I even qualified it as ONLY my opinion. If you don't like my opinion, counter it with YOUR opinion instead of trying to discredit me with someone else's opinion.
And as for the Porsche/Chevy comparison, I'm talking about factory specs before OTHER people get ahold of the motors and mod them. Chevy Camero: 325 HP Porsche Carrera GT: 612 HP. ALMOST twice as much from the factory.
Mark D.

[jd74914]

Ken,

The motor I sold to Mark Henry was going to be a 94mm X 78mm engine. (still should be since I think Mark is putting it together with all the components I sold him)...Jake helped me with the selection of components, the idea was that with the stock 2.0 heads I had, the extra stroke and smaller bore would allow the cylinders more time to ingest the air/fuel mixture. With the cam spec'd by Jake, he thought 160hp was not out of the question...very similar to the 2270 posted above, but with the bone stock 2.0 heads, probebly lacking a little here and there....still would have been a fun motor...

Mike, you were going to build it with stock heads? Was this engine planned for turboing (hence extra air being forced in)?

[Mueller]

[quote name='jd74914' date='Jun 13 2006, 06:05 PM' post='702898']
[quote name='Mueller' post='702881' date='Jun 13 2006, 08:46 PM']
Ken,


Mike, you were going to build it with stock heads? Was this engine planned for turboing (hence extra air being forced in)?
[/quote]

yep stock heads..that is why I went with the 94mm bore instead of the 96mm bore, the larger bore (and stroke) would benifit or would for sure need head work...this motor would have worked normally asperated or with the small turbo I have..that is how Jake and I had planned it from the start... (still going to install the turbo on my 1.8)...


Mark, I don't even know where to start....you cannot compare a pushrod V8 in a pedestrian grocery getter to a purpose built V10 barely streetable racecar...as for quoting Jake, I've done quite a bit of homework on the Type IV's and learned from Jake and others (still learning)

[Mark Henry]

OK, but here's the rub.
Just because the stock stroke is shorter it doesn't equal less wear or higher rev's. Stock rods are about 815g and the aftermarket type 1 rods are 590g, so that alone is close to a half pound less being tossed around. If you're using stock pistons they weigh 710g, my 102mm JE's weigh in at 510g (so I expect the 96mm KB, 22mm pin are the same or less) so if your using a stock piston (or KB with a 24mm pin) you're now pushing almost an extra pound per journal. Multiply that pound by 6000rpm
Unless you are using $1200.+ Carrillo rods and $1000. JE 22mm pin pistons you just lost any advantage you may have had from the shorter stroke.
At any rate even if you stick with stock rods you should upgrade to ARP rod bolts so there's $150

Also note in those dyno graphs that both torque and HP are done at 5800rpm, so being able the rev higher doesn't mean a whole lot.

If the 78mm crank is counterweighted, with a proper balance it has less harmonics, add lighter rods and pistons equals less wear at high HP levels. The rod angle ratio with a 5.400 rod is not that extreme.

[jd74914]

yep stock heads..that is why I went with the 94mm bore instead of the 96mm bore, the larger bore (and stroke) would benifit or would for sure need head work...this motor would have worked normally asperated or with the small turbo I have..that is how Jake and I had planned it from the start... (still going to install the turbo on my 1.8)...

cool, thanks for the info. I was wondering why you were using a 94mm bore, now I get it. did you have custom long barrell (sp?) cylinders, or very offset wristpins?

(sorry for the hyjack everyone else)

[KenH]

Mike, yes it does. I cannot export the pintout directly, but I will scan it and see if I can post it as a picture. If you have a FAX # I can "print" and send it as a FAX. If you want, send me your fax# to jacquiken@verizon.net or post it here.

It would be nice if somebody on the BBS had a good dyno program. Maybe the Club should buy one and find someway to allow members to use it.

Ken

[Mueller]

(IMG:style_emoticons/default/hijacked.gif)
stock Type I pistons (aftermarket) and stock length cylinders (Nickies)...CB performance rods (mod'd by Jake for clearance issues with the cam)

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