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Pre Cups

but it also depends on how lean you make it. Basically, it might work with smaller mouths with lots of boost, really lean. But if you dont want to run super lean, but rather more in the 18:1 to 20:1 area of air to fuel, as to not blow the heads off or bend connecting rods, then you may need the larger openings to burn the same amount of fuel you might be able to burn at 40:1 air to fuel ratio. Theres a lot of variables, so you cannot just say it works one way or the other.
 
you are only going to get so much power from a measly 80cc's of fuel.... no matter how you manipulate the pre-cup, or anything else... it is only going to go so far. It is money, and time much better spent getting more fuel into your engine, than messing with something that already works well.

If you read that PSN thread, you will understand my reasoning.... having dyno'd many different 6.9/7.3's... I know what the engine is capable of as far as rwhp/cc and rwtq/cc.... until the engine starts drastically dropping those numbers down, the pre-cups are working just as good as they did stock.

As I said there, if you disagree with me, prove me wrong..... so far nobody has proved me, or Racin' wrong on this topic.
 
Simply put, just because you are not wrong, does not mean you are right. You might be right about one thing, and completely missing another point. You can't speak in terms of facts until you have proven yourself right, and thus far you have not. You have simply taken a specific configuration and documented how it performs. The entire discussion is such that you dont want anyone to prove you wrong, so you dismiss their ideas.
 
buddy said:
Simply put, just because you are not wrong, does not mean you are right. You might be right about one thing, and completely missing another point. You can't speak in terms of facts until you have proven yourself right, and thus far you have not. You have simply taken a specific configuration and documented how it performs. The entire discussion is such that you dont want anyone to prove you wrong, so you dismiss their ideas.
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I have taken several different configurations, and documented how they perform, and drawn a conclusion. More than anyone else has..... Therefore, my research is more factual, and holds water, better than the speculation of others.

I dismiss the discussion because all it is, is bench racing. I want people to stop flapping their gums and build something.

If you built two identical setups, minus the pre-cups.... and one setup with a modded pre-cup made another 50+rwhp then I would jump on board.... but I know this will not happen. Its not possible in the fuel levels you are looking at. You would be lucky to gain 10rwhp on the top end, and that is time wasted... you can get 10rwhp from less than 5cc's of fuel.


This is actual the same recipe that got me into the IDI's. Being told more than 200/450 was impossible without power adders, and $10,000.... I got pissed and I proved people wrong..... but I'm also smarter than the average 6.9/7.3 owner... I have a grasp of what works and doesn't work without even seeing it.
 
Not everyone runs only 80cc of fuel, I can hit 100cc or better with a stock DS4. Highly modded DB2s that can push a bit more. That doesnt mean every precup is even able to handle 80cc very well with a specific CR, boost level and Air to Fuel ratio. Your conclusions are drawn by inference, that because this way works well, that the other way doesnt work better. That doesnt hold much water. Its a very nice data point, a great starting point.
 
buddy said:
Not everyone runs only 80cc of fuel, I can hit 100cc or better with a stock DS4. Highly modded DB2s that can push a bit more. That doesnt mean every precup is even able to handle 80cc very well with a specific CR, boost level and Air to Fuel ratio. Your conclusions are drawn by inference, that because this way works well, that the other way doesnt work better. That doesnt hold much water. Its a very nice data point, a great starting point.
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I have said many times.... that I believe it is very possible to improve upon the pre-cups, but they are not worth the time and testing involved, for the minimal gains you will see. 100cc is still not very much fuel..... I'm talking about getting into the 180-200cc realm. I'm currently rebuilding my DB4, this version will be sporting near 170cc output, up from its 120cc output.

Tell you what, you're so certain it will make gains, then why not do it? Why is everyone standing around with their hands in the pants talking about it, instead of executing?
 
People do it all the time, when they swap engines or heads and use the latest precups GM made. Compared to the smaller, with smaller mouths made in previous years. And GM continually increased the power rating, so it seems they already did it for us. I am not contending that 6.5ers have to go do experiments, I suggest they capitalize on the ones GM already did.
 
Credit: Missy Good Wrench

attachment.php
 
buddy said:
I suggest they capitalize on the ones GM already did.
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nothing wrong with this, however the thought of "GM already did it, so it must of helped" is hard for me to jump on board with considering other design flaws.

That being said, the people who are interested to know exactly what the cups do..... why are we not doing pre, and post dyno's so you can see exactly what it does to the torque curve, if anything?

Also, what is the deal with fuel? Why is nobody pumping some good fuel through their engine yet, with a good pump... not some janky garage creation? I would really like to see the data findings, I know some of you may think I'm a jerk and have other motives, or don't care... but I do.... I just hate people that talk for the sake of hearing themselves speak.... and we know there are many people that do that on these forums.
 
buddy said:
And what you dont see in the pic is the back side, the inner volumes got greater, to drop the CR over the years.
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I don't believe it was done entirely for CR drop there seems to be a ratio of how much volume of the precup vs squish area. and when you turbocharge you need a bigger precup volume to keep the ratio in balance
 
nmb2 said:
I have said many times.... that I believe it is very possible to improve upon the pre-cups, but they are not worth the time and testing involved, for the minimal gains you will see. 100cc is still not very much fuel..... I'm talking about getting into the 180-200cc realm. I'm currently rebuilding my DB4, this version will be sporting near 170cc output, up from its 120cc output.

Tell you what, you're so certain it will make gains, then why not do it? Why is everyone standing around with their hands in the pants talking about it, instead of executing?
Click to expand...

Maybe so but when you thought you were running 180cc of fuel you wouldn't even entertain the idea that precups could be an issue. IMO when you actually get that much fuel then it's time to start looking at the precups. If you guys can successfully build a HO IP you won't have any trouble selling them. We've been told for years that the db4 pump wouldn't work cause it was designed for marine use and couldn't be modified successfully for the varied throttle that the street needs yet here we are. It's pretty hard to get people to try something new when EVERYONE tells them it won't work.
 
There have been other peoples whom have ran / run 4 plunger mechanical pumps, some have been "janky garage creations" some not, and I can name one that is on a truck that is a "production pump" from Stanadyne for the 6.2 / 6.5 (that is rated for 40hp per cylinder in stock trim)... How many 4 plunger mechanical pumps were produced for the 6.9 / 7.3 platform that WEREN'T a "janky garage creation"..... ??????

Not to mention... seems as if you have done good yet crazy, extensive amount of work to the good ole 6.9 just to nip 300 rwhp.. great job !! However, I'm not UNconvinced that our old outdated 6.5 platform couldn't do with mostly bolt-ons, especially with the Optimizer blocks and redesigned heads, tweaked DB4 pumps / well tuned DS4 pumps, turbo / exhaust upgrades.
 
I have run a four plunger,but it was maxed out. I had a stock 2 plunger put out 170ccs,and it was not maxed,but close.
 
ak diesel driver said:
Maybe so but when you thought you were running 180cc of fuel you wouldn't even entertain the idea that precups could be an issue. IMO when you actually get that much fuel then it's time to start looking at the precups. If you guys can successfully build a HO IP you won't have any trouble selling them. We've been told for years that the db4 pump wouldn't work cause it was designed for marine use and couldn't be modified successfully for the varied throttle that the street needs yet here we are. It's pretty hard to get people to try something new when EVERYONE tells them it won't work.
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I never thought I was running 180cc. I was told I was running 150cc, and after I dynoed I had doubts... and you're right, I wouldn't entertain the idea of the pre-cups being a limitation. Good thing too, because they weren't. What I don't understand, is how so many people have adopted an opinion about something, that they have absolutely no experience in. How can you say that @ 180cc's, I need to address my pre-cups.... when nobody has ever reached the limitations of the pre cup by any stretch.... All you guys have is an inductive argument...

Obviously my DB4 works fine on the street.... that's all I can add to that.

Mike K3500 said:
How many 4 plunger mechanical pumps were produced for the 6.9 / 7.3 platform that WEREN'T a "janky garage creation"..... ??????

Not to mention... seems as if you have done good yet crazy, extensive amount of work to the good ole 6.9 just to nip 300 rwhp.. great job !! However, I'm not UNconvinced that our old outdated 6.5 platform couldn't do with mostly bolt-ons, especially with the Optimizer blocks and redesigned heads, tweaked DB4 pumps / well tuned DS4 pumps, turbo / exhaust upgrades.
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Was that an attempt at knocking my DB4? There is nothing janky about my DB4, it is of the highest quality, as is all of my work, and parts that go onto my truck.

How have I done crazy amount of work? I built a turbo kit, a custom pump... and did basic engine building...... nothing really crazy about it.... stock bottom end with milled pistons, stock heads with a good valve grind, cam swap and a little bit of custom fabrication.

I may of only hit 300rwhp.... but I did it @ 2500rpm, I also did 614rwtq @ 2,200rpm. Max hp/torque @ 3,000rpm+ does me no good.

Its not like my "only 300hp" is due to a design flaw.... its due to me being out of fuel, and the pump defueling.
 
I would also like to add, just so there is no confusion. I'm not mad, nor am I trying to be abrasive. I truely enjoy this type of debate. Its strong debates like this, that inspire, and lead to new innovations.
 
nmb2 said:
I never thought I was running 180cc. I was told I was running 150cc, and after I dynoed I had doubts... and you're right, I wouldn't entertain the idea of the pre-cups being a limitation. Good thing too, because they weren't. What I don't understand, is how so many people have adopted an opinion about something, that they have absolutely no experience in. How can you say that @ 180cc's, I need to address my pre-cups.... when nobody has ever reached the limitations of the pre cup by any stretch.... All you guys have is an inductive argument...

Obviously my DB4 works fine on the street.... that's all I can add to that.



Was that an attempt at knocking my DB4? There is nothing janky about my DB4, it is of the highest quality, as is all of my work, and parts that go onto my truck.

How have I done crazy amount of work? I built a turbo kit, a custom pump... and did basic engine building...... nothing really crazy about it.... stock bottom end with milled pistons, stock heads with a good valve grind, cam swap and a little bit of custom fabrication.

I may of only hit 300rwhp.... but I did it @ 2500rpm, I also did 614rwtq @ 2,200rpm. Max hp/torque @ 3,000rpm+ does me no good.

Its not like my "only 300hp" is due to a design flaw.... its due to me being out of fuel, and the pump defueling.
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I can't speak for Mike, but I don't think he was knocking your db4 as he is in the process of running one himself. Check out his threads.
 
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