Competition First post - stroke vs. cylinder wall loading question

[GO 4LO]

Stock stroke on a B5. 9 is, I believe, 4. 72", correct? Can anyone tell me how much loading the Cummins' cylinder walls can take, when used with a stroker crankshaft, for example? I understand that using a stroker crank will increase the loading but am curious as to whether anyone has experimented with this and found the limits...

I'm looking into ways of building more low end torque in order to spool a very large set of twins in a relatively useable rpm range. Cost is not really an issue here.

Any ideas or comments would be appreciated - thanks in advance.

Chris

 

[fox]

Cylinder loading also includes the rod length.

Sorry I don't have the link you need for the math.

I'm on vacation and the info is at home.

 

[GO 4LO]

Originally posted by fox

Cylinder loading also includes the rod length.

Sorry I don't have the link you need for the math.

I'm on vacation and the info is at home.

Yeah, rod length is somewhere around 7. 5", which puts rod:stroke at around 1. 58, if I remember correctly. I've heard the old idea that anything over 1. 50 is okay, but I don't know if that applies to turbodiesels, too?

I'll dig around some more on the internet. Thanks.

Chris

 

[T. Baker]

Are there any other cranks avalible? Why would you need more low end torque - they already have enough to rip most drive lines to pieces. The key is keeping torque up to higher RPMs.

 

[GO 4LO]

Originally posted by T. Baker

Are there any other cranks avalible? Why would you need more low end torque - they already have enough to rip most drive lines to pieces. The key is keeping torque up to higher RPMs.

Commercially, not that I'm aware of. But there are shops out there who will build you any billet crank you want if you give them the specs (and a LOT of $$).

Extra torque is to hopefully cut down on lag time for a large twin setup.

Chris

 

[jimk]

Originally posted by GO 4LO

Stock stroke on a B5. 9 is, I believe, 4. 72", correct? Can anyone tell me how much loading the Cummins' cylinder walls can take, when used with a stroker crankshaft, for example? I understand that using a stroker crank will increase the loading but am curious as to whether anyone has experimented with this and found the limits...

I'm looking into ways of building more low end torque in order to spool a very large set of twins in a relatively useable rpm range. Cost is not really an issue here.

Any ideas or comments would be appreciated - thanks in advance.

Chris

I am not sure about the turbo diesel cummins but generally rod ratio, rod length has a lot to do with the cylinder loading, torque curve. I like to run a rod as long as can be installed. If you increase the stroke and not the rod length the rod ratio is less. That is what was told to me 20 years ago or so . , I think that if you are looking for ways to increase spooling I would try one of the aftermarket camshafts, good luck jim

 

[GO 4LO]

Re: Re: First post - stroke vs. cylinder wall loading question

Originally posted by jimk

I am not sure about the turbo diesel cummins but generally rod ratio, rod length has a lot to do with the cylinder loading, torque curve. I like to run a rod as long as can be installed. If you increase the stroke and not the rod length the rod ratio is less. That is what was told to me 20 years ago or so . , I think that if you are looking for ways to increase spooling I would try one of the aftermarket camshafts, good luck jim

The engine's already got a cam, actually. Thanks for the thoughts on the rod lengths, too - I'll look into that.

Chris

 

[jimk]

Re: Re: Re: First post - stroke vs. cylinder wall loading question

Originally posted by GO 4LO

The engine's already got a cam, actually. Thanks for the thoughts on the rod lengths, too - I'll look into that.

Chris

Did the aftermarket cam make a difference?

good luck jim

 

[GO 4LO]

It made a difference on the current set of twins, but we're trying to go with a larger set - with and HX-55/60 size turbo for the secondary. It may end up spooling okay, especially if we use a JR's hybrid 55, but we're looking into other options right now, too. Thanks for the help, Jim.

Chris

 

[MCummings]

Hey Jim,



I ran a turbo darn near an HX-60 for the top turbo, and an HT4B for the bottom. It was laggy, especially on a stock motor (hard parts). Not bored, low compression, or aftermarket cam. All OE.



I made 530RWHP with an unknown amount of boost. My Gauge crapped out, then the turbo's ate a rock.



I now have a 'lil '55 on top. The same one you can get through me, or J. R. Nothing special about it, and a HT4C on the bottom.



I haven't gotten a good test on these yet, but, they spool so much better than my previous combo. With my auto, and using teh throttle properly, it's under 8 seconds to build enough power to spin the tires, where as, the other set could take as much as 15 seconds. (This is trying to spool them at 1,500RPM)



I haven't had an opportunity to test these new turbo's out much, since I lost a HG, and spun a rod bearing. (also cracked a head. )



It's coming back together with some bigger valves, XXHD Valves springs, and retainers, a la J. R. and some trick rebuild work from Chris Strickland, some special parts from TDR Member MDW, Haisley's, and DTT.



The only problem I'm going to have, *I* feel, is getting that transmission to live a descent life between rebuilds... (clutches)





The truck wil be all put back together with some cool stuff soon, and should be running by May 28th-29th of May, and then I'll yank it up to TiM for some Sled Pullin' ! and Demo Rides !



Merrick



BTW,, When I did take the truck out for a spin,, I got an easy 80-90PSI with my fuel plate slide all the way back. (HX-40/HT3B was getting ~60)

 

[T. Baker]

How about just building triple turbos so you can have a small one for the spool up. Maybe a bypass valve so it doesn't get in the way on the top end. Seems like it would be cheaper than a new crank. ( Just went back and saw that money is no object ) Take the hood off so you have enough room for the turbos.

What are you trying to do anyway? Pulling, dragging, street racing?

How about a roots blower for the bottom end and a bypass valve like the Detroits have. Then you would have boost at darn near idle and it would just bypass as soon as your turbos kicked in.

 

[GO 4LO]

Originally posted by T. Baker

How about just building triple turbos so you can have a small one for the spool up. Maybe a bypass valve so it doesn't get in the way on the top end. Seems like it would be cheaper than a new crank. ( Just went back and saw that money is no object ) Take the hood off so you have enough room for the turbos.

What are you trying to do anyway? Pulling, dragging, street racing?

How about a roots blower for the bottom end and a bypass valve like the Detroits have. Then you would have boost at darn near idle and it would just bypass as soon as your turbos kicked in.

I've considered the triple turbo idea, as well, but overall, I don't think cost will end up all that different, and we won't have the plumbing nightmares and space issues of a triple setup.

I do have a related question - will the heat gained during the compression of the air be the same regardless of how many turbos? (i. e. 120 psi boost achieved through triples or through twins)

The roots blower is a good idea that I'd not even considered - I'll look into that. Thanks!

Chris

 

[GO 4LO]

Any more thoughts on ideal stroke length? I pulled some numbers off of another forum, and if we choose based simply on piston speed, these are the numbers (all rpms are the points at which piston speed is 5000 fpm:



Displacement numbers assume 10 thou overbore.



4. 37"___5500rpm___334cid___1. 75R/S

4. 52"___5250rpm___346cid___1. 69R/S

4. 72"___5100rpm___361cid___1. 62R/S

4. 92"___4900rpm___377cid___1. 55R/S



I'm still not sure how to calculate the differences in cylinder wall loading between these setups, though. Any help?



So given all this info above, what would be the ideal setup for a dragracing (and occasional sledpulling) Cummins?



Thanks.

Chris

 

[TractorNut]

We work with Tractors. . mainly Antiques, where we are limited on RPM's. . so there is less concern about breaking cranks. . so most of our cranks are welded... Billet shafts are just too $$$$$... .

But there are some out there... When you get into the real smokers billet parts are more common. . Stroking should give you more low end torque... boring should give you more high end HP. .

Not sure what you a looking at... custom pistons can be really trick... I have seen pistons where the piston pin is bolted to the bottom of the piston. . or have caps that cover the piston pin so the rings can run over the piston pins. . this of course was to run the longest rod possible. . but these were all on low RPM engines where stroking is done 2-3 INCHES. . and sometimes more. . but there are only 2 cylinders. .

I would think that a stock rod. . (or stock length) with custom piston would be the trick. . (with custom piston, you could go with any bore size. ) Only problem we have seen is that some times when the pistons get too short there is too much pressure on the cylinder wall. . and it tends to scar the walls. . (I don't remember the rod length. . but it was on a tractor that had a very short block. ) If 4. 72 is the stock stroke I would look at something a little over 5in. . but you need to look at clearance on the cam. (easily notched. ) and block clearance. . and of course $$$$

I think I'm just rambling at this point... . but I think with the small amount of change that you are going to make its not going to be that big of an issue. . but more is better...



MC... I had to Strickland about this at one time... anything in the works for your engine?????

Bryan

 

[Forrest Nearing]

nitrous works wonders to spool turbos!

 

[TractorNut]

nitrous works wonders to spool turbos!

Nitrous is GOOoodd. .

some in trick pumbing... and... ...



Has anyone tried fuel with Polyprolene (sp?) in it. . It addes O to the fuel... ??????

Bryan