ZZ Fab head, or larger charger?

RonA

RonA

Active member
Joined
Feb 26, 2008
Messages
11,080
I'm driving the primary fairly hard now. Don't like seeing close to 80psi overall. Would it make more difference to go to a head that's been ported on both sides(intake and exhaust), or just go to yet another (larger) primary.
 
Larger ar will just slow the process down a bit. It will still drive too hard on top. I have heard that the additional porting can decrease the restriction and drop the boost number a bit(hopefully increasing hp by allowing additional fuel). If it's just a matter of spending $4k for a cool manifold, I'll pass and go to a bigger charger. But if there is power to be gained at the same or lower boost level, great.
 
I say dial in your combo and dyno again to get some more baseline numbers, then go with the headwork route. It should drop boost levels and increase power at the same time. Less restriction = more air in the cylinder.

If you could do this and then dyno again with no other changes it would be great to see the comparison...

Not many people have dyno'd before and after head work/intake work as most people do too many other changes at the same time...
 
What is wrong with 80psi of boost?

I don't see a ported head dropping the boost numbers by a large amount, but benefical for more power.
 
Primary is already gated.

80psi seems like alot of boost for 800-900 hp.
 
With boost , you will get not only heat , but a corresponding increase in drive pressure , this restriction on the exhaust side of the equation creates heat on its own , and takes power from the engine to pump the exhaust gasses out in to a manifold that is already pressurized

If you could take this pressure completely away from the equation , as in a supercharger the gains would be significant . , but with a engine driven supercharger you have the parasitic drag on the crank. Remember that a turbocharger is in reality exhaust gas driven supercharger and is not free either.

Now on to the subject of making power .

First , any engines ability to make power is tied closely to how much air , and the quality of air that you can pump thru the engine. The fuel is the easy part , as in the case of a diesel .

Fist engine is a restrictive stock port engine with high boost numbers , this engine forces high temperature air in to the cylinder , this air even if driven thru a efficient intercooler , still requires a lot of drive pressure , and hp to force in to the combustion chamber . The amount of time it takes to spool is longer , and the retained heat , from the previous cycle will take away from the potential power , before the piston , or cylinder containment give way

You can drop compression to compensate , remember that the ignition even in a diesel is not related to the injector firing , but instead its occurs when the temperature , for pressure reaches a point that the fuel auto ignites . High boost and high intake temps , along with high residual temps lead to the ignition timing being to early , causing the cylinder pressure to spike to early before the piston is traveling down the hole , and now your in trouble, the answer is to reduce the compression.

By reducing compression , you have taken mechanical advantage out of the engine , this is a fact of physics.
Mechanical compression ratio , makes power in that the combustion chamber is smaller in realation to the swept volume of the engine , allowing more expansion energy to me converted in to power .

Got to get , ill finish this later this afternoon
 
Being that our cylinder heads flow like crap, it takes high amounts of boost to flow the air for 800-900hp. Remove some of the restriction(ported head) and the same amount of power can be had with a lower boost number.
I personally don't feel that 80 psi is out of line to make 800-900 hp. on fuel.
 
What I seen from porting my head and adding my billet manifold is that my boost has dropped about 7psi and the egts dropped about 150 with the same set up I was running before and the spool up was allot quicker . I wanted to get the truck on the dyno so I could give you guys some numbers but ended up cracking the block before I could do that. All I can say is from the seat of the pants dyno is it made a heck of a difference and if you can feel it you know it must be substantial.
The thing is if you can drop your egts and boost numbers running the same set up you can add more fuel to get back to the previous numbers you were running before and then how much difference horse power wise is that going to make? A bunch!
 
I don't want to be redundant but i'd check drive pressure and make sure it's 1 to 1 or darn close. I'd focus all effort on getting it to 1 to 1 if it's not (large turbine side of chargers and or gates). From there it's your choice.
 
With improved airflow, and running lower boost, you'll also pick up some bottom end power since the engine will be flowing more air at all times, so, IMHO, it would be worth it, just to widen your powerband, and on a daily driver, it would increase the "ease of use", LOL (I made that word up for "driveability).

Merrick
 
here is a thought , Project X diesel with a ported head and ZZ side draft manifold , MaxSpool 2.5 cam and II 90 hp injectors and SB 66 turbo make 597 with out any programs or a fuel box.
this on about 35 lbs of boost and 39 lbs of drive pressure
the EGT's were lest then a 1000 at all times and compressor out temps were around 235
 
here are pictures of the extent we are going for air flow

P1030921.jpg


P1030986.jpg


P1040006.jpg


P1040007.jpg
 
Got to talk to someone who cut off the manifold and ported the intake side. Seeing the dyno sheet it makes sense. Peak power moved up to 4k rpm from 3500. Nothing under 2000rpm though. Good to know. I'll pass on this mod. Probably be great for a comp only truck.
 
Rona, what happened to the torque curve of the modified head engine? Did it lose power at the low end rpm? IMO 80 to 90psi isn't bad for a 800-900rwhp engine. I pushed 70-80psi on a HRVP engine that made around 700rwhp. Have you put any instrumention on the twins? Thermocouples, pressure guages? It would help to tune in the twins. My set-up was 1to1 until 70psi, but I ran small towing twins GT-3782R over a BTH-3B
 
I hook up a drive pressure gauge when I put a different charger or housing in either location. My setup runs 1.13 to 1 at 75psi. On the dyno it is only there for a fraction of a second so it's tough to get an accurate reading. Egt's are 1200 or so. The torque curve is changed by the porting. Peak is at higher rpm.
 
You must log in or register to reply here.
Top