swirl in a diesel

I just had my cylinder head swapped back from Zach's 12v head to an OE cummins one. I had Zach deck the head to lower the valves and add some swirl reliefs to the intake valves. That head showed 380PSI on my truck. Same as a stock setup with .020 oversize gasket.
With the hamilton unit, the spool and top end was nice, but part-load operation was awful. I had thick idle smoke and off the line Id smoke the people behind me. Dialing this out with the AFC wasnt possible without making it undriveable.
Fueling stayed the same.. turbo was not changed. The only thing that really changed is the port and valve sizes. My guess is that swirl (from higher intake speed) is the real change.
FYI if anyone is considering a ported head on any daily driver truck. The only way to (maybe) have your cake and eat it too is with a supercharger to make up for the change in port velocity.

So now on the OEM head the low load smoke is gone? Everything else the same?

Dave @ Passenger, has been doing some testing with measuring the swirl in various heads, with some interesting results, hopefully he will chime in here.

I know our full ported Hamilton head had almost 50% less swirl, then our full ported 12v head. We had speculated that swirl was the issue, but until we sent them to Dave we didn't have concrete evidence.

Yup otherwise same setup except the head.
I probably should have waited to try the supercharger idea before I swapped it out.
Anyone else compression tested a stock 12v? curious what readings I should be seeing.
wondering if all the crud and economy problems are worn / coked rings.

Nice cylinder head just didnt fit my particular application. Most folks probably wouldnt notice the extra smoke.

Everything in research I've come across suggests exactly that, with no hard evidence of my own so only left to speculate. The 24V's naturally with the port arrangement are not nearly as affected, and looking at the video's of RonA's build seems to have very little low load-off boost smoke suggesting the same.

IMO the supercharger is just a bad band aid. The other fellow noted poor combustion even on boost.

Im going with the supercharger as soon as I can. Will post the results for part-load smoke / economy and all that. Maybe save someone else some grief and cash.
Its fun to tinker with this stuff though. Learn a lot.

I have a couple of heads laying around with different swirl #'s cast into them from 3.0 to 4.25, what # (high or low)is the best for a daily driver without getting into porting the heads.

Yeah we just got a swirl meter so we have been doing lots of testing across different head combos. The Hamilton head swirls literally about half of one of our ported 12v head with similarly sized valves and almost as much flow. The velocity doesn't have anywhere near as much to do with swirl as most would guess. First thing we thought when we saw the Hamilton head was "this thing isn't going to have much for swirl". Its as simple as just not having an appropriate swirl dam.

I'm working on redoing all my flow charts with swirl numbers right now. Hopefully have some new data late next week.

But to prove my point check out this graph we have from our work on the Hamilton head. The ported example had swirl reliefs in the deck and the manifold had been machined off.


Here is a OEM casting stock vs the same casting ported, with OS valves and swirl reliefs.


The oem ported 12v is similar in cfm to the stock Hamilton but literally has double the swirl.

Another interesting note is that the Cummins 12v and 24v, along with the duramax heads all have a very similar amount of swirl. And we've been able to port all those heads with large cfm increases, while getting within 5% of factory swirl.

What numbers do you have on a stock valve ported 12v head. I want to see if they are close to what i have.

The goal is to have that top end flow and maintain decent part-load operation.
Would be interesting to see if a ported head with similar flow rate was able to come close to factory swirl even with lower port velocity. And then whether part load performance followed like you would expect.
Im -almost- tempted to try one, heh. Im about done with heads for now though.

This week is a write off for trying to get all my swirl numbers together, just got swamped here. Hopefully next week.

Die Hard- here are the stock numbers for a 12v with the same head ported (stock valves, manifold on etc).



Kawi, I think you'll be surprised how close the swirl is from stock to ported on what we've done.

Thank you Passenger: My numbers are a little lower on the intake 22.5 CFM lower. On the exhaust mine is 31.4 CFM lower At .500 lift. With stock valves. I know i could have gone bigger on it. But it is for my 98 12v street truck. I did'nt want to go to big. I was afraid i would have a lazy port if i went to much bigger.

I have gone bigger on race heads. I just did'nt feel that i needed it bigger for a street truck.

Unless I'm seeing it wrong, does that graph show the low speed stall problem? At 0.100" valve lift, the ported head is down 2cfm on the intake? Is that right?

joefarmer said:

Unless I'm seeing it wrong, does that graph show the low speed stall problem? At 0.100" valve lift, the ported head is down 2cfm on the intake? Is that right?

Click to expand...

Yeah that is right, but 1.8cfm is nothing, you'll never notice anything at .100" anyways, much less 1.8cfm at any lift point.

I had to look "swirl" up. I had a good idea but wanted to make sure. Found this. Sorry...

Has anyone compared port velocity loses/gains on a Hamilton head? Does the fact that we utilize forced induction minimize the loss of swirl. Sorry if i derailed the thread.

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Good find!!

Epically post by a dumb phone.

jkidd_39 said:

I had to look "swirl" up. I had a good idea but wanted to make sure. Found this. Sorry...

Has anyone compared port velocity loses/gains on a Hamilton head? Does the fact that we utilize forced induction minimize the loss of swirl. Sorry if i derailed the thread.

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

Click to expand...

I don't think more forced induction can mitigate swirl loss. From what I've seen, I surmise RPM does.

Swirl Numbers

PASSENGER said:

This week is a write off for trying to get all my swirl numbers together, just got swamped here. Hopefully next week.

Die Hard- here are the stock numbers for a 12v with the same head ported (stock valves, manifold on etc).

Kawi, I think you'll be surprised how close the swirl is from stock to ported on what we've done.

Click to expand...

Did you ever get a chance to post your swirl numbers. I'd love to see them. I am setting up to do some porting and testing and would like to see some baseline and advanced numbers, comps to the Hamilton would be interesting to.

Thanks

Velocity figures are interesting also. Bulk CFM figures mean little on the scheme of things.

That is an impressive difference from over sized valves. Now I'm even more excited to see what they will do in my truck.