Boost/Compression Ratio Calculator

[More Power]

Dave,

The DS/DB pumps generate their highest mm3 output at about 2000-rpm. It tapers off to some degree at higher engine speeds. Probably has something to do with rate of pumping plunger recharge - not able to keep up at higher speeds. The marine DBs have slightly better flow rates above 2700+, which means they should be able to produce more horsepower (rpm is a factor in the numbers). I'd have to see the data sheets from a calibrated Stanadyne flow bench to be convinced of 100+mm flow from any DS/DB. I have the Stanadyne spec sheets for the DS and DB2 & DB4. None approach 100, at any rpm.

The original LB7 Duramax was rated at 91mm at 3400-rpm to deliver 300 horsepower, but it has a high-pressure common rail, which means fuel delivery is less affected by higher engine speeds.

Clear up the smoke... I plan to install a modified Holset HX35W on our newest 6.5 project... This one is efficient at 15-20 with cool EGTs, where the GM turbos are not - too restrictive. I'm not doing this (Holset) for ultimate power, but for better efficiency and fuel economy.

Jim

[spdgofast]

Hey Jim, as we have spoke before, if the P400 comes with 19:1 pistons I'll leave it and tune accordingly, if not I think I'm going to put 18:1 s in it and then play with the tuning and I think I will be able to add more fuel IF IN FACT THERE IS A PUMP PUTING OUT MORE THAN 90 MM. I agree with you and I have my spec sheet but there sure are alot of claims of 100 to even 120 mm of fuel output most claiming from a DS4, I couldn't get mine to do that so that is why I converted it to a DB2, so I'd have to see it to believe it but who am I? I just want to be able to get MORE POWER if infact someone can get a DB4 to put out more fuel than my DB2. And Missy I presently tuned with a GM 8 turbo with a Spearco IC, a 3" DP and 4" to muffler then 5" muffler on back, so yes you are correct if I just added an HX 35 to my present setup 15 psi of boost may be enough I just don't want to have to pull the motor and change pistons later if a better pump is produced. Nor do I want to pull it because I overboosted or overfueled either. I am really hoping that you are correct and the P400 comes with the 19:1 CR so I won't have to go into the motor and I think the DB2 that I have now will work great with that CR and a HX 35 and it will save me some $ to maybe put that Dodge IC that I have taking up space in my shop in it. Oh! then it will be able to handle more fuel, It's a viscious cycle this diesel power thing Jim got me started on back in 95 when I bought my Burb.

As always, Thanks for your time and input, Dave

[More Power]

As far as I know, the P400 engines are all 20.2:1 CR, unless AMG is offering something different as a special run for Peninsular. Talk to Matt-at-Peninsulardiesel.com He'd know for sure, because the 18:1 CR is his baby.

Jim

[Robyn]

I will make a suggestion here.

If this were MY project

I would go pretty much as you are going, except that I would not spend the $$$$ on the 18:1 pistons on a brand new engine has cost some serious $$$

The 20.2:1 slugs are not going to be an issue unless you are planning to run this rig at a constant heavy load for miles and miles on end with maximum power demand.

The 18:1 pistons came into being due to Penninsulars use of the 6.5 in large boats.

A boat is always on a pull (uphill both ways) and when subject to hauling said boat along at a good rate of speed the load can be really heavy.

The testing that was done showed that the stock 21:1 compression resulted in too much peak combustion heat that caused piston seazure.

In a truck you are not likely to have any of these issues.

The secret is to tune the engine to make a good reasonable power level and maintain the intake air temp and of course the biggy, the exhaust temps.

Now, running a DB2 pump will allow you to fool with the timing easier than a DS4.

Slightly advanced timing will yield lower EGT's while slightly retarded timing will see an increase in the EGT.

Too far either way from nominal is not good.

Make really sure that your POP pressures on your injectors are all as close to identical as your IP/ injector guys can get them.

A top flight set of squirts not only promotes easy starting, better fuel economy and EGT's, having nearly identical squirts also helps eliminate tortional vibes due to cyl-cyl timing variations.

If you have slight POP pressure differences such at 100-150 PSI it changes the actual time that the particular cylinder fires in comparison to the one before or after it.

On my last 6.5 engine, I spec'd the injectors at 2000 PSI which is a tad low for a DS4 but still within specs.

All the injectors were spot on at 2000 PSI (cost me a tad extra for the fiddling) but the engine ran exceptionaly smooth at idle and all the way through the RPM range.

Injector setup can have a marked effect on EGT too. A poor set of squirts can send the EGT right off into the Ozones.

The secret is a nice clean "POP" at the right pressure with a clean well defined spray "cone" of fuel and a clean crisp fuel cut off.

Poor injectors are probably one of the biggest causes of starting issues, poor fuel economy, rough running and high EGT's (other than overfueling)

Stay away from "marine injectors" especially those advertising 40 plus HP gains.

A stock factory injector as used in these engines can pass all the fuel that any of the pumps spoken of here can provide.

Much of the Hooopla on the Marine injectors is derived from the fact that just replacing the old worn out stock injectors makes such a huge difference in power that the sellers credit their "Marine Squirts" as the reason for the power gain.

Many things to consider here.


If it were me, I would really think long and hard as to whether you really will benefit from the 18:1 pistons.


Just some thoughts.


Missy

[spdgofast]

Hey Missy, not much time right now but a P400 from AMG comes with no warranty but Matt SAYS that Peninsular will give a one year warranty on an 18:1 motor. Trust me, I'd rather leave it alone, and I got real excited when you said that they came with 19:1s in them but that's not the case. I thought of puting .010 head gaskets on it with the stock pistons but I'm afraid of failure. If I put 18:1 s in it and I just add fuel and boost untill I get a "clean burn" and 20lbs max boost and I'm thinking it will live. I would like it to take 25lbs of boost just incase a real HO DS4 gets developed. DIS in grand rapids is working on it slowly because I donated a perfectly good DB4 pump housing for them to play with. My Marine DB2 with marine injectors feeds a good amount of fuel but HP to me is like a gun "It's better to have it and not need it than to need it and not have it". I could reconvert it back to a DS4 and put one of these programmers that claim 120 cubic mm of fuel but I think I would have to witness one of them on a test stand puting out that kind of fuel 24/7 for a year steady before I'll do that. What do you think about that Jim? DS4, 120 cubic mm per stroke?
Thanks Again
Happy Holidays
Dave

[Robyn]

Sounds good on the 1 year warranty.

As far as I know there is not a DS4 that can shove over 90 cube mm of fuel.

There is a lot of Myth and just plain BS out there about all this stuff.

The HO DB2 stuff that Penninsular has to offer is good stuff.
They have gone the extra mile, done the testing on the dyno and can back up any and all claims on what they sell.

Good luck with whatever you decide to do.

The P400 is a good foundation to start with for sure.

Missy

[spdgofast]

1. This is what I have... The HO DB2 stuff that Penninsular has to offer is good stuff.
They have gone the extra mile, done the testing on the dyno and can back up any and all claims on what they sell

2. This I believe... There is a lot of Myth and just plain BS out there about all this stuff.


3. They are working on this... a DS4 that can shove over 90 cube mm of fuel.