Just a little more . . . . .

[oldestof11]

Should.

Back it off to match EGT's and see where it goes from there.

One thing I havent seen mention is the change in the primary pressure and overall pressure. What is your primary putting out and what is the overall boost?

[DMan1198]

Yes. When tuning common rails we like to have between 48 and 52% btdc so it runs right. When we start getting into big duration tunes we often end up with less than that ideal percentage (I've written tunes that end up pushing close to 60% of the fuel atdc) because I don't want to exceed a certain timing number (before I did headstuds it was 32*, and after has been 36*)

When I go to bigger injectors on my 6.7 I want to be able to more than half the amount of duration I'm running now, and still break 800whp

[RCCUMMINS89]

That doesn't correlate over that simply though.......larger orifice, less holes. less injection pressure, less cylinder pressure.... results in more burn time. This is noticed due to percent of injection prior to tdc on a ve. We have a max of 30 degrees worth of injection duration ( if my head math is correct right now ). At 50% we would run at wot roughly around 15 degrees worth of timing. Way to test this... keep your rail pressure at a near idle situation and do a wot run... you'll find that that percentage of timing will end up changing, egts will be crazy hot, and power will be way down.

The 2 things that are being changed with large nozzles is location of cloud point, and burn time. Cylinder pressure will act the same as increasing injection pressure... which results in a quicker cloud point (if they are increased). This allows for less timing, and a cleaner burn.



This all related back to the fact of a ve likes a high cylinder pressure in order to re gain the proper burn, once we have huge injectors. This is hard at lower rpm.... which can really only be overcome by super fast spooling, high-er drive pressure turbos, or by raising the compression of the engine.

Now both of these things fight wot power... are really the only way of over coming the size of injector (injection pressure) we are now with. Other thing to do.... increase h/r size or modify cam plate for a quicker injection rate. This quicker injection rate can only be achieved by dramatically increasing injectin pressure.... thus changing cloud point, burn time, efficiency... etc....

[KTA]

Just a note. I made more power with my twins by wastegating the pressure 20psi. I attribute that to reducing cylinder pressure, which allows more fuel in because of the lower cylinder pressure. I know that cylinder pressure can exceed injection pressure on these with big injectors because if I lift too fast at full boost the pump will air lock and stall the motor. In my experience a higher cylinder pressure is not really what you are looking for to make the most power. You need good turbos, head and cam so you can get boost and power up as soon as possible because low rpm is where the VE works best. You can not simply make more power by producing the same cylinder pressure at a higher rpm like is typical of P-pump and common rail motors. You put big enough injectors in you can make a ton of power as can be seen by project Rust bucket on NOS. Getting it done on fuel and air only is a whole lot more difficult battle.

[RCCUMMINS89]

Couldn't agree more.......but to combat low end, low rpm smoke.... cylinder pressure is about the only solution with huge injectors.


Obviously that is counter productive at making power.... But if one were to use a very fast (air = cylinder pressure) spooling, small set up, and then gate very generously up top.... one can result in a clean down low power. Such in a way that if BC put on a single he351cw, he wouldn't make squat for power, but would have a potentially perfectly clean low end drive able truck.

Again, this is all due to the injection of a ve, and tremendously large injectors (remember he is around that 5x20 mark) on a 12mm h/r assembly.

[KTA]

What kind of hp is BC dynoing? I made about 480rwhp and 1100ft-lb multiple times with a 62-71 .80 turbo and a 12mm pump. I still have a stock cam too but had done a bunch of head work. It burned clean at that level once boost came on so I thin the 62mm is fine, maybe even a bit smaller would be better. I think cooler air and a cam that drove the turbo harder would have maybe been enough to break 500, I don't know really that a lot of hp could be gained as the fuel just isn't there, but the torque could easily be increased which of course would result in more hp, just not more peak hp, and of course a better driving truck. For a 12mm pump truck you don't need a ton of air, just more cool air and early in the rpms. I think the best way to do that is to have your low pressure turbo with a mid sized compressor, probably a 68-71mm with a big turbine and a very loose exhaust housing. the loose housing and big turbo makes the back pressure on your high pressure turbo virtually none so you can get it spooled fast, once you get the little one started it will kick the big one in the butt and get it going for when you need it on the top. It is counterintuitive to spoolup, but I have seen it work. If I redo my twins I will be doing something similar as opposed to the tight housings and wastegates I run now.

[RCCUMMINS89]

I (probably shouldn't) speak for him.... but from my understanding, he dynod 488? being the best it has done....but hasn't been on the dyno with the honed 5x18 SACs with lift.... but he is currently looking to clean up the 1800ish rpm and below driving around smoke that has come MORE into play when switching from the 6 to the 5, (losing a hole) without losing, and maybe gaining some wot power at the same time.

He has a good cam, and head work. He is also running the 62/3b set up which is still not fully cooling it at wot power.

[KTA]

A lot better options than a HT3B for the low pressure turbo. That is 40 year old turbo tech. If it was me I would replace it with a 169011 BW turbo. I can get them for like $600 new and I have seen them run over 1000fwhp on built 12V and 24v puller motors so it can feed a good bit of air and they spool nice plus it has the big exhaust housing that I think is perfect for a fast spooling set of twins.

[oldestof11]

KTA, it is good to have you back.

BTW, a very prominent injector builder would argue your combustion vs injector pop pressure. I would love to see a debate on that.

Are you going to start building 14mm H&R again?

[fatty]

KTA, it is good to have you back.

BTW, a very prominent injector builder would argue your combustion vs injector pop pressure. I would love to see a debate on that.

Are you going to start building 14mm H&R again?

Yes, very good to see KTA posting again. Must mean harvest is over.

[RCCUMMINS89]

Loose housing on the primary.... less restriction to the secondary.... faster spool.... Ya, I can follow that theory. If the housing/wheel combo on the primary is in fact a restriction.

In some ways the same theory as me and dman were talking about the other day.... using a super small secondary and a very large primary.... thus driving with a tight low end, heavily gated... therefore at wot there wouldn't be the restriction, as one would primarily be driving off the primary at that point. Such as seen on some of the stock/s480 set ups that are seen on the common rails.

[KTA]

KTA, it is good to have you back.

BTW, a very prominent injector builder would argue your combustion vs injector pop pressure. I would love to see a debate on that.

Are you going to start building 14mm H&R again?

Yes, very good to see KTA posting again. Must mean harvest is over.

Not over, it has just rained for 11 of the last 13 days so the farming is on hold. I have no plans to build anymore 14mm h&r's. I think building a timing cover to run two 12mm pumps is a more practical and better performing solution.

[BC847]

Thanks for stepping in a commenting Brian.

So . ..


Crap . ..

An exhaust manifold with the external waste-gate option, a slightly smaller secondary S300 based compressor with a slightly larger turbine, . ..

An s400 based primary with a looser exhaust housing, and smaller wheels (compared to the ht3b?) Confused there . . . or am I reading sizes wrong (Borg Warner S470 S400sx4 T6 169011 VS HT3B).

I like the notion of the smaller primary getting things going earlier with the primary kicking in hard . . .


Shit. I'm distracted with my work . . . can't put my mind into this like I want .. . . gotta rebuild the brakes NOW, so I can get it inspected, so I can renew the registration . . .

[RCCUMMINS89]

My vote....Go with a tighter/smaller secondary, and then a larger primary. Some what goes a lot with the theory of Brian's (not the same, but sort of)... being less restriction going through the primary and therefore not slowing the secondary's spool. Similar to driving around with a single.

You'll most likely lose some of the smoothness of the compounds, but at wot, once things get going.... you'll be driving off an even larger primary. Due to a heavily gated (possibly externally gated) secondary.

[Tacoclaw]

If your secondary gets too small and/or 'gated around won't the compressor wheel become a restriction?

Are you all betting that the airflow mods he's got will be enough to compensate for the lessened boost pressure from not driving the secondary as hard?