12v head vs 24v head vs 24vcr head

[CATCRACKER]

does anyone know the d/f in how these heads flow? cfm?



what i am getting at is, why does the common rail injection system spool turbos so well?



higher flowing head? higher injection pressures? duration of pulse injections?

 

[Cooker]

Never having owned, and only driven a few 3rd gens, I was under the impression that the did not spool as well from a dead stop but once the boost was up a bit then they fueled hard and really lit the charger.

 

[BBowers]

I am under the impression that first, more fuel and air period in the higher horse(305-325 horse) stock cr engines will produce more exhasust and thus spin any turbo up faster. I know from looking at a 96 ram 3500 ctd that it has a much larger turbo than my 2005. The bitty lil turbo has low inertia and spools up quick but also I belive produces a greater exhaust restriction under lots of load whereas a big turbo spools slower but moves lots of air efficiently, probably where a lot of our fuel economy probs reside with the 3rd gens!!!!

 

[CumminsAholic]

I also thought that it was mainly because of a different fueling curve and a much smaller turbo.

Corey

 

[CATCRACKER]

(this is for modded non stock trucks) no what i am saying that with comprable fueling the 3rg gens a able to spool sps66 type turbos like the other trucks cant. this has lessened the need for twins. we see people using 66mm turbos with very little lag this was not the case with 24v's vp44 or 12v. i am wondering if the head flows better or is the CR the reason.

 

[Vaughn MacKenzie]

The 24v head flows about 15-20% better than a 12v head, and I think the HPCR flows a little more than the 24v head (not sure on that though).



Here's a CFM comparison http://www.piersdiesel.com/DodgePortedHead.htm

 

[KBaucom]

Smaller exhaust housing has a lot morespool up than others

 

[Scrappy]

Smaller exhaust housing has a lot morespool up than others

But 3rd gens can spool larger turbos easier than a 12 or 24V with the same turbo. third gens really don't smoke @ low rpms like the older trucks do

 

[Scrappy]

The 24v head flows about 15-20% better than a 12v head, and I think the HPCR flows a little more than the 24v head (not sure on that though).



Here's a CFM comparison http://www.piersdiesel.com/DodgePortedHead.htm

Isn't the 24v and ISBE heads the same? they look the same to me.

 

[Cooker]

third gens really don't smoke @ low rpms like the older trucks do

Isn't this an idication they do not fuel as hard on the bottom?

 

[Jeff_K]

Isn't this an idication they do not fuel as hard on the bottom?

Exactly, the CR motors fuel bsed on boost pressure.

 

[Cooker]

Exactly, the CR motors fuel bsed on boost pressure.

That was the point I made earlier in this thread:

they (3rd Gens) did not spool as well from a dead stop but once the boost was up a bit then they fueled hard and really lit the charger.

So from a dead stop the 2nd gens, particularly a 12v, lit the turbo better initially?

 

[CATCRACKER]

no its my understanding that the 3rd gens spool turbos of anysize better than the other engines. i am trying to find out why? is the 24v isb head the same as the 24v hpcr head? the reason people always went with twins on the 24v isb is b/c they could not spool the 66mm compressors that well whereas the 24isbe are spool 66mm sinlges very well.

 

[KBaucom]

the reason people always went with twins on the 24v isb is b/c they could not spool the 66mm compressors that well whereas the 24isbe are spool 66mm sinlges very well.

No this is not true a 66mm charger will spool on a 24v twins move more air and make a more driveable truck moving more air efficiently giving the motor cooler air to burn more fuel.

 

[Lsfarm]

Head flow differences

The CR head flows about like a stage 1 ported 24v head, the ports are much cleaner and the valves have a lot less shrouding. No doubt this helps to spool big turbos and helps make more HP compared to the earlier engines. The head gasket is much better on the CR engine too, seems to survive 50 psi boost.



Cooker is right, the CR engine increases fuel only with increase in boost pressure, this is to reduce exhaust smoke and emissions.



Greg L The noise nazi.

 

[raychem]

timing is key

CR engines tend to spool better than the 12 and 24 valve engines since they are able to control engine timming aggresivly and over a wider range since the ecm controls injector timing. 12v had fixed timming on a mechanical pump which you were always stuck on. 24v's w/vp44 have a broader range of timming better than 12v's to a point.

 

[CumminsAholic]

To answer your question. It's because of the timing and fueling curve. A 3rd gen won't necessarily spool a big turbo faster, it just doesn't have the surging problem like the 2nd gens.

Corey

 

[CATCRACKER]

ah now some good info flowing here! all of this makes sense to me. so the CR head is like a stage one 24isb head. very interesting.

 

[HoleshotHolset]

Cooker is right, the CR engine increases fuel only with increase in boost pressure, this is to reduce exhaust smoke and emissions.

Aren't OEM VP-44 ISB's like this too? Quite a few of the fueling boxes for those fool the ECM into thinking that there is enough boost to crank the fuel... AND have a voltage clamp that leads the ECM into believing the maximum boost is within OEM limits.



I can actually see where an ISBe could spool the turbo better because of the multiple injection events on the same combustion cycle. It's a good smooth burn and results in a progressive increase of cylinder (and exhaust) pressure - instead of one big explosive event.



To create boost on the compressor side, you need a delta of temperature and pressure across the turbine wheel. ISBe's start with enough fuel for a minimum of 305hp... us 12-valve guys are starting with enough fuel for a minimum of 160hp. ISBe's have a lot more fuel on-tap all the time without even having to take into consideration the turbos, heads or other factors.



The ISBe's also have a different exhaust manifold. The combination of the exhaust manifold and modified combustion cycle makes them sound a LOT different out the old tailpipe than an ISB or B5. 9.



Matt