308 V12 conversion begins

I was actually pleasantly surprised that the flow didn't go down. The port was still pretty rough at it was late and I was rushing (and guessing where to grind) the bigger valve is sticking into the flow more and is probably a tad big for the seat ID I cut which is smaller than I started with....all of these are bad things for flow as a general rule.

What I need is about 10 uninterrupted hours on the flow bench…..which is just not going to happen. I start a new job in a couple weeks that adds 45-60 minutes to my commute which means I need to get up earlier, so I may not even get my 1 hour at night anymore

 

Maybe....i would make passing easier.

Well I got the flow up to 161 tonight....by removing the TB and the vavles and the valve guides. Something is not right with the port.

 

Maybe. 3/4 of the gain was the valves and guides. I think I've got something not good about port....I think I'd expect to see 180+ cfm, it's just a tube now that the valves, guides and TB are removed, but honestly I don't recall ever trying the everything removed test on a head before. I opened the seat up to 29mm first thing last night and gained a little so now the head should in theory be able to flow about 165 with the valves, guides and TB installed and good ports tend to flow about low 90s% of a tube...so 180ish. The next time I get a chance to play on the flow bench

The problem with the TB is the throttle plate and shaft usually...which is why they make flat slide TBs. These TBs really need to have the shafts milled and the screws ground flush....but I need to actually buy them before I do that to them. I should probably try a run with the shaft removed too to be sure there is no restriction form the body itself because as you said it should act as a port extension/velocity stack

 

We have to make sure that happens!

 

OK, I played a little more and the flow is going in the right direction again. I was avoiding grinding on the top of the port around the guide to keep the port as straight as possible....but that was a huge mistake it turns out. Everytime I touch the top the flow goes up 2 cfm. It's at 154 now (with the TB off) and rising. It's time to watch to re-rur of the F1 race, but I'll get back to it monday and should be able to finish up this week.

 

Well, my elation was premature…….154 was all it had in it and no grinding anywhere was going to give me any more. I did find that after sinking the intake valves enough for the 34mm valves to fit, the exhaust valve sitting at stock height was sticking up and interfering with the flow at around .250-.350 lift, my buddy Vic had pointed out that the flow graph didn’t look quite right which send me hunting for the problem.

I think it’s pretty good now honestly. I still need to flow it with the TB on but I’m sure it’ll be fine. The peak flow number is lower then I’d hoped for but the lower lift numbers are better than I’d been using in the simulations so the computer says I’m up about 5 hp over the estimated head I was using. You can see on the graph the flow is pretty much all done going up by .450 lift....exactly the lift I'm planning to run. I think I’m done….well except for welding shut a small hole I put in the water jacket.
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I clicked on it and saw it was long and didn't have time to read it carefully and work on my port, I chose the port. At first glance it looks about 1/2 right but I'll give it a good read today.

 

It does andc that is basically what I've already done. It always works out that the cone angle should be 4-5 degrees so a simple calculation is all thats needed vs a lot of testing time. The throttle plate itself though buggers up the flow so there needs to be at least a 2mm step at the plate and upto a 8-10mm step often works. The 54mm ducati TBs give me about a 6mm step which I would say is about idea.

The issue with the TBs is 2 fold I think.

First the manifold makes a slight curve and the TB has a slight taper bercause of the large throttle plate and it's 48mm oval exit. This makethe TB blend about perfect on the bottom side of the port, but on top there is a slight angle wherew the TB meets the manifold. I'll need to port the TB a touch to fix that.

Second is the throttle plate, shaft and screws. The plate is thick and the shaft is round making it thick and the screws stick out. I need to mill flats on the shaft and switch to flat head screw that are cut flush as a fist step. I might also mill the plate thinner but I'd rather not if I don't have to.

 

Ok, I think I understand the question. The answer is complicated because all the variables are interrelated and every decision ends up being a compromise.

Port angle. The optimum angle for flow is about 30 degrees. The optimum angle for tuning the wave pulses in the intake track is zero degrees. Zero degrees causes a lot of flow loss in a high velocity port, but once the angle is opened up to 4 degrees the flow result because length independent. So a 4 degree port the is 4 inches long will flow the same as a 4 degree port that is 24 inches long…pretty much. The same is true for any angle over 4 up to about 30 degrees.

Length. The track length is chosen to tune the wave pulses in the track to boost power at the rpm you are interested in with the cam you have and also to fit on the space available. Getting the length right is a pretty critical variable and there are a few choices. The wave pulses in the intake track bounce back and forth and damp out as they go. The strongest pulse is the 1st one, but tuning with it would require intake manifold runner that look like header tubes so that is almost never done. Normally a "long runner" intake is tuned to the 2nd pulse or harmonic and a "short runner" intake is tuned to the 3rd harmonic.

If the port/runners were straight I would make more hp tuning to the weaker 3rd harmonic because of flow losses caused by the extra length needed to tune to the 2rd harmonic. This is the traditional solution. More recently the 4-5 degree angle has com in as "standard" design so its not flow loss that is the issue, it's port/runner volume gets so big it takes a lot of energy to get the air mass in the port moving so you never get the pulse strength you would with the shorter runner. The only way to be sure which is better is to test it on a dyno, but I'm not going to do that. I will be tuning to the 3rd harmonic primarily for space reasons and call it good enough.

 

Ok, he's got a lot of stuff all mixed up together and I' can't sort out what's doing what honestly.

Keeping the air moving in the combustion chamber helps mix the fuel and lets you run higher compression. If the fuel is already mixed by proper injector placement and sizing and the compression ratio is limited by the cylinder pressure at the torque peak I'm not sure how any claim of improved low power output can be made and he isn't making any claim of improved peak hp.

What I see is a baseline engine that is fitted with heads that are a flow restriction. Then a set of well ported heads is fitted and the engine makes more power everywhere, as expected. I don't know what else to make of it. He's been working on it for years and the patent is from 2003, I would think in all that time he would have been able to run an engine fitted with 2 matched flow heads, one with normal valves, the other with his polyquad setup and show us the improvement in a clear no questions way….but he hasn't done that.

The polyquad concept get the "Wrong" stamp I think

I did briefly consider fitting each valve with it's own TB so at low power I could just use 1 port, then progressively open the second port. That would without question bump up the low power hp/torque significantly. On the down side it's also a lot of work and work mean 36 injectors and 3 ecus to control it so this idea got the "wrong" stamp too.