Jump to content
HybridZ

Twin cam head for the L6 from Derek at Datsunworks


Recommended Posts

  • Replies 1.3k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

This is all Tony D’s fault:)   Hi everyone. Some of you know me from my  DIY EFI manifold project http://forums.hybridz.org/topic/63445-making-my-own-efi-intake-the-first-casting/ &#

Machine work finished!   I can relax a little:) Just got done with their first bath. Still need de-buring and edge finishing but the majority of the work is done.    

Yes, the exhaust port 'could' use some work, the as-cast cleaned intake is flowing within 10cfm of a 4 hour port job on an OS Giken head.   Those numbers outflow most max ported SOHC heads

Posted Images

Yes, the exhaust port 'could' use some work, the as-cast cleaned intake is flowing within 10cfm of a 4 hour port job on an OS Giken head.

 

Those numbers outflow most max ported SOHC heads by a good margin. Most you will likely get is around  230cfm intake, possibly more.

 

The important thing is that the barrel tested was 89mm, and not something like 4", which would skew the low-lift numbers artificially low, and boost top end numbers by potentially 40-50cfm!

 

Overall, this is very good port performance and about as big as you really can go on the intake side with a 2.8 or 3.0 Liter engine. The peak power will be up there...in terms of gross output, and rpms!

 

You won't get these numbers  out of a non-crossflow head. 

 

And I don't see any reason to get uncivil since the 28", bore size, clayed radius, exhaust stub stuff is all stated for replication.

 

More importantly, it gives a baseline for improvements  from any porting done. 

 

I would only add that it would have been nice to quantify intake manifold loss, and what the intake port flowed with the intended ITB on it at WOT.
On Peter's OSG project, that added up.

 

One thing to note for all the benchracers out there, that turbo stock intake flows 190 CFM thereabouts. So for a P90 that's a darned good match of components! The engineers DO know what they are doing sometimes. Thinking you will change the world swapping from one component to another is really misguided, it's  a system--if you don't look at ALL the components, changing one will likely just screw up a well-balanced setup right from the  factory!

  • Like 2
Link to post
Share on other sites

Really, the important thing is that  there are SO MANY options now available for K20 CNC Ports. 

 

I'm sure the possibility exists that the port could be hand-massaged to increase the flow, but with 310 or about that on the intake side (bare) getting the exhaust to flow 75% of the intake (232 cfm) should be a matter of talking to the CNC guy and saying "give me your 230cfm exhaust port"...

 

Then some casting changes and out of the box you are flowing 270 intake 200 exhaust and have the proper balance right out the gate. Nothing big the end-user must do, other than casting cleanup. This is how you keep costs down: sweat equity by the buyer. If you want to just bolt it on and run it, it's balanced. If you port it you get incremental gains. 

 

If you wanna go hog-wild you still can.

 

JUST REMEMBER THERE IS ONLY SO MUCH FLOW AN L30 OR L28 CAN USE! For a TURBO application these numbers represent staggering possibilities. For an NA L-Series though, especially a small one like under 3.0 Liters, you are going to have to understand you WILL need to twist the engine to 8,500 - 9,000 to get maximum horsepower. Our Bonneville car had 220 cfm in the intake port and with 45mm ITBs was 320+ to the rear wheels  just over 8,200 rpms. This setup will be FAR more tractable, and with 52-54 mm ITB's should be very like an OS in the respect that you could lumber along in fifth gear at 1,500~2,000 and mat it for a pull that just gets stronger as the RPM's rise to 9K!

 

The Non-Crossflow head will perform well to a point. But on larger engines, 3.2, 3.3, 3.4 Liters...it really restricts the power you can ultimately get from them as they can't pass the air to make the power. 

 

The  exciting aspect is that the ports are as-cast about at the limit of what you can use flow-wise on a 2.8 or 3.0 if you are comfortable twisting it to 8,500~9,000. Put a proper ATI dampner on it, have Velasco's do a crank up right and you will have a fun car. I would HIGHLY recommend a 3.9 ~4.38, even a 4.62 R200 gearset out back (with the differential cooler) to have some REAL fun with the car and this  head.

 

Turbo guys... they will need new shorts if they understand what these flow numbers mean.

 

One porting job and exhaust port design change to get port balance correct "out of the box" and other than maybe thickening the port walls for guys who insist on hogging  stuff out... I think the port configuration is set and done.

 

For a first try, I'd say it's darned good! VERY darned good!

Link to post
Share on other sites

All this being said.... that same 220 cfm intake port was used  on our L20A to do SOHC Valve Train Stability testing. We ran that engine to 12,500 rpms+ on the dyno seeing what power did and if we got valvetrain instability.

 

The first person that hears and L-Series running open exhausts at 12,500 rpms will remember that sound. There is a point where it changes from individual exhaust pulses and exhaust, and starts sounding like the wail of an F1 Engine Warble. To paraphrase Clint Eastwood in "Heartbreak Ridge" : This is the Nissan L-Series, and makes a distinctive sound.

Link to post
Share on other sites

OH, and one-more-thing.... As stated any flow bench number is a relative change. You baseline it then compare for flow improvements against that baseline. Like dynoes one is not standard against another unless strict criteria are specified and standardised. In this area, there is 'conventional thinking'...

 

Remember conventional thinking. The standard for decades has been to use the bore-sized liner you run in your engine for testing flows. This stems from old OHV designs and is absolutely critical on them and the Nissan SOHC the valve opens along the bore wall and shrouds the port somewhat. Hemis? Nah. Ever wonder why those old 'twisted wedge' combustion chambers had those funky valves that pushed the valves to open towards the center of the chamber?

 

On a Pent-Roof Canted Valve engine like this... and on those twisted funky-valve-angle dinosaur heads bore size during flow testing really is a moot point. You could jigger the head about...but because the valves open to the CENTER of the cylinder and not along a bore wall the effect of shrouding is pretty much eliminated. But in an effort to stave off criticism on internet boards, following "standard flowbench practices" in the setup validates the test in a lot of peoples eyes. Doing it, whether it impacts the test results or not, is simply a way to keep the superfluous chatter down now that this is occurring in the open domain. A lot of this same discussion was done offline before these numbers were posted, 'we sniped at our own results' before posting them so as to silence detractors who are not making  their own head....but who might be more  than willing to cast stones at the efforts of those doing so.

 

Fat Old White Dudes. . . you know?

Edited by Tony D
Link to post
Share on other sites

Hey... it's a stereotype on the internet. It can not be helped if you have Ethiopian Genes.

 

I haven't been 170# since I was in the USAF Olympic Training Program... And I had to cut 20# off then that I gained in Basic Training and Tech School because the  regimen was so laid-back.

Link to post
Share on other sites

I am only more excited than ever to see flow numbers because it shows you are committed to getting this done. I bought a spare VQ35HR that I was planning on swapping some day...this seems just sooo much more appealing. This may seem like a dumb question but what kind of options do you plan to have available for head gaskets? 

Link to post
Share on other sites

Turbo guys... they will need new shorts if they understand what these flow numbers mean.

 

I simply can't imagine how much this will move the surge point in the RPM range for the "big boys" turbos. On a conventional wastegate setup this could very well be making boost in HALF the RPM compared to a stock Nissan head of any kind, and wouldn't get mad at you for creating 15psi by 2,000rpm. But really, even 15psi on this head is looking like a 700+hp engine, which means we're talking BIG turbo requirements. I'm thinking something in the GT47 size range with a turbine AR down sub 1.00. Should spool that sucker in no time, and you're not trying to get 1200hp worth of air out of it.

Link to post
Share on other sites

So I figure it's well past the time these photos came up...

 

Sorry for the delays, Derek.

 

KIMG0052_zpshcoopwtg.jpg

 

KIMG0053_zpsu4wiesnp.jpg

 

KIMG0054_zpstf3dt6j0.jpg

 

1.75" OD stainless steel tubing, with tubing lengths selected to boost as much as possible the upper-middle RPM band as that's where the head is going to be making the big power. (4800-7800RPM) The low-end isn't going to be suffering, either...unless the collectors get cut shorter than 10", and if the collectors are left a LOT longer (like rear of the transmission mount long) then the BMW sound will start coming out.

 

Will have more photos for you once the back three tubes are fitted and tacked. Am trying to work it so I can hand-deliver these prototype headers myself! Would love to get a chance to see this project "in the white".

Link to post
Share on other sites

so pardon my ignorance here... but with all this potential torque the engine can produce, what kind of transmission options are available to handle this? Its not like collins adapters has plates for an L28, and hoke has been out of stock on the Z32 adapter plates for sometime... The B boxes might work fine for a while, but repeated abuse will take its toll alot quicker on those. Longevity and reliability through repeated abuse is the issue I would think. SX C boxes are getting harder to find because the drift crowd is beating them to death.

 

I dont see anyone making 350/370Z trans adapters either... so what are the options for a good trans to mount to the engine with this setup?

Link to post
Share on other sites

 

 

 

 

 

D stainless steel tubing, with tubing lengths selected to boost as much as possible the upper-middle RPM band as that's where the head is going to be making the big power. (4800-7800RPM) The low-end isn't going to be suffering, either...unless the collectors get cut shorter than 10", and if the collectors are left a LOT longer (like rear of the transmission mount long) then the BMW sound will start coming out.

 

 

 

Looks great Xnke!

Edited by Derek
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...