I understand the scientific and spiritual effects of porting and polishing and valve jobs on n/a builds as you want the most ideal flow of air and fuel through the head but what about on boosted cars? What changes? Does it become less about the increase in flow and more about the "feel"? Numbers wise you can't tell me it adds anymore than 5hp on a n/a build...

 

For naturally aspirated Honda engines it might increase the total power 5-10 horsepower since the Honda cylinder heads already flow well. For low boost turbo applications it will be similar. But the more the boost is, the more proportionately the gains are. It’s difficult to determine exactly how much of a gain will be present because not much dyno testing has been done before and after port and polishing to find out exactly how much it will be. But I’d estimate low boost 5-10 HP, medium boost 20-30HP, and high boost 30-50HP.
So it is something that is advantageous for boosted applications.

 

Very cool, so the added volume and velocity all play together and you can potentially make more proportional gains, wow, well explained.

 

It's difficult to say exactly how much power a P&P job gains for two reasons:

1: 99% of the time, people do not do back-to-back dyno runs with the only difference being a P&P cylinder head, so we can't directly compare results.

2: The results of a P&P job will vary greatly depending on the quality of the job, as well as what other mods are in the head.

Another thing to keep in mind is not every cylinder head is created equal. Manufacturers that leave heads with worst casting marks/imperfections obviously have more to gain from P&P than Honda cylinder heads which are typically pretty well optimized from the factory.

IMO the biggest benefit to polishing a cylinder head on a turbo car is it can help prevent carbon buildup on the exhaust side. A smoother surface, less snags, helps keep the exhaust clean a bit longer.

Personally I wouldn't pay extra to P&P a head unless I already had it out for major work/rebuild and had cash to spare. It's a nice thing to do if you have the cash to spare and want every last bit of efficient power out of the engine.

 

I noticed a huge difference in response times in a good way. Theres more power under the curve and top. Feels like having more displacement added. What i had done was a competition port job on exhuast side. Mild on the intake ports. Valve job and combustion chambers opened up to 84mm.

However, do to the wonderful increase in flow, my 38mm no significantly creeps on anything under 17psi. I have an 8psi spring in the gate. And setup double in pressure before it holds. No boost leaks, same setup before the headwork. Same setup on my other 58mm.

In the end, would i have the work done again? Hell yes! But not until i had a killer setup. Instead of just upping the boost, i wanted to make the head even more efficient so whatever turbo didnt have to work so hard.

 

What company did the port work? What cams?

 

pure tuning
toledo, ohio
419-474-7992

-spec h port job
-gsc n1 cams

 

I would think that if you COULD do a p&p and valve job that it probably wouldn't hurt. It would increase flow and power and give at least a little difference in the feel of the engine. I just think its more of a reward and art to do it on a n/a build where the flow of the head is making a bigger difference in power. I would think boost kinda blows that out the window in the sense that it is a charge of compressed air and your making the extra 100+hp because of the boost already so whats 5 more hp from headwork, I just don't think it'd be really worth it to do alot of headwork on a boosted setup. Idk its something about the casting marks and diameter of ports and how they limit power due to flow on an n/a engine compared to a compressed air charge flying over the castings and small ports like it doesn't even matter on a boosted setup.

 

Right.
I think it has to be done by highly professional engine machinists because it must be evenly ported, and all ports should match each other so that the engine flows evenly.
Some people do their own unprofessional porting and or polishing and I think the engine wouldn’t be “blueprinted” the right way afterwards, whereas stock, at least it’s even and the ports match each other.

 

Regardless how much boost is used. Just like an intake manifold, a given cylinder head can only flow so much. So in the circumstances, an unported head can be a bottleneck. Porting allows whatever amount off boost to enter and exit more efficiently.

 

sorry for re-flamming an old post.. but I've read through some of the responds and just wanted to add my 2 pennies. A good pnp job will greatly benifit any engine. Even some diy backyard work will help head flow and cfms. If you have time, check out SRDmotorsports on YouTube a great guy based out in the Phillipines. Does great head work and very reputable. He has one specific video where he ported a d16z6 and the customer did a back to back dyno comparison. There was a whopping 90 whp gain with more to gain but got cut short due to running out of fuel.. even on n/a heads, my f22a1 head was a huge bump in power once I got done porting it with a minor pocket port and cleaning up the short turn with a 89% valve to throat ratio. True with supporting mods the port work will definitely help produce more flow and power. But if your wanting to know if a pnp job will benefit any gains alone??.. Absolutely. You'll definitely feel a increase in torque with a stronger power band. And its a great first mod to do, since other mods will certainly come after, it'll boost all the mods one after another. I would say a good port work will net anywhere from 15whp to 30 whp depending on the work done, valve job, 3 angle, pocket port, combustion chamber de-shrouding, etc etc.. but with my diy port work, I am pretty sure it was around 15 to 20 whp since I felt this mod more than a typical I/H/E modification combined. So yes, definitely, pnp work is a huge benefit and we'll worth it.

 

Yeah....I'm gonna call BS on that one. I'll be happy to eat my words if it can be shown that porting alone yielded a 90 whp gain with nothing else changed on the car, no boost or timing added, same fuel, and accurate calibrations on the dyno for both pulls. I'm fairly confident one of those things changed.

 

I forgot to mention it was a boosted application. The proof is in his video, he has links to there dyno video comparison