Opinions on Rudy's modified VCV and ported rails?

Buck1 · Feb 5, 2014

Very good info. Thanks a ton! My first common rail, so learning.

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sootboy · Feb 5, 2014

No problem, glad to help.
Keep us updated on the test.

Randy_270 · Feb 5, 2014

sootboy said:
No they stroked the cam.
I tried modding a regulator or 2 and did not getany huge gains. It did help.
I also just gave up and went to twin hpfp's.
I am sure with the rails it will help, or else they would not be selling them!

So with that being said, if one was to buy an II 55% over pump and the modified VCV, could you in theory get more flow out of the stroker pump?

Buck1 · Feb 5, 2014

Will do! The guage thing really helped clear things up.

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bigrpowr · Feb 5, 2014

Randy_270 said:
So with that being said, if one was to buy an II 55% over pump and the modified VCV, could you in theory get more flow out of the stroker pump?

well i highly doubt that pump increases flow by 55%

sootboy · Feb 5, 2014

Randy_270 said:
So with that being said, if one was to buy an II 55% over pump and the modified VCV, could you in theory get more flow out of the stroker pump?

Ok this is my take:
On the old cp3 style pump in dmax and cummins the fp reg control volume and idle pressure.
On a cp4 the regulator at pump is volume and the safety relief on the left rail controls idle. (Hence in new mcc software h and s provided control of the low pressure regulator for dual pumps)

Historically early regulators such as lb7 / lly dmax had 2 small rectangular holes in the barrell that were indeed restrictive. With lbz/ Lmm models the barrells went to 4 triangles. The tips control idle. It was found that style barrell provides suffient fuel.
It is now prefered to just use an lbz regulator for ease of tuning. Modification of the older regulators is inconsistent.

This brings us to the cp4. The barrell of the cp4 pump regulator has 4 very large t shaped holes. I also took the barrell out of an ii stroker and it did not appear to be modified.

I have found that drilling all rail fittings out to 1/8" has been very helpful in the past.
I have not done this on my personal 6.7 psd.

I hope that all makes sense.

sootboy · Feb 5, 2014

bigrpowr said:
well i highly doubt that pump increases flow by 55%

In my personal experience it took a truck that was dropping rail at 1350 us pulse and allowed the truck to run 1850 without dropping.
Injector latency of a piezeo at 29k psi is around 250-300 depending on nozzle size.

So subtract 300 from both numbers and we get a 500 pulse difference.
Divide 500 by 1050 and it works out to 48%.
I agree that number is very optimistic.
Hot fuel and latency decreases.
There are multiplier tables that correct in the tuning for that.
But I did use the h and s and watched the inj pulsewidth pid.

So I agree and have some testing to back it up if that helps

dseitler · Feb 8, 2014

Running box tune H&S the rail pressure never dropped below 29K. With the SPE HotX the rail drops to 27500 right away at WOT. On my 13 if I go past 1/4 mile to say crossing over 100 mph the rail pressure drops so fast I can't read it and the motor shut down. I am going to do the VCV and rails also but I am really pushing toward my supply pump also. Doing the rails is not going to help my complete drop off. I'm not ready to do the dual pumps yet. I want to see how far I can get with this first.

Gmoney69 · Sep 1, 2014

Did anyone get to install the vcv and rails? I'm looking
To do this next if it helps bc canned hns tuned with my torq 2 sets my low press code off now and If I could hold rail pressure w the two on I'll be so happy.

Gmoney69 · Sep 1, 2014

Also what's involved in installing the two? Is it hard ? I can't seem to find any info on this anywhere and can't get any emails back from elite or Rudy's?

bigrpowr · Sep 1, 2014

Gmoney69 said:
Did anyone get to install the vcv and rails? I'm looking
To do this next if it helps bc canned hns tuned with my torq 2 sets my low press code off now and If I could hold rail pressure w the two on I'll be so happy.

what pulse width are you commanding ? just run some mcc tunes with slightly less.

Gmoney69 · Sep 1, 2014

Iv got no idea. Using the canned tunes still. Going to try some gearhead tunes see if that helps. Good idea?

dseitler · Sep 1, 2014

The only thing that's going to help is more fuel. I spent months on this problem dropping rail pressure. The best fix is dual pumps. If you not willing to spend this much money then the next best is a modified CP4. After that the VCV would be the less expensive. Anything over 1340pw you will drop rail no matter who's tune you run. Most will give you less pw so you won't drop rail pressure. If your planning on stopping at this point the VCV will work but it's hard to get and always on back order. I'm not sure about longevity no one has talked about that. You will be over maxing your CP4 pump. Who knows how long that will last.

Gmoney69 · Sep 1, 2014

dseitler said:
The only thing that's going to help is more fuel. I spent months on this problem dropping rail pressure. The best fix is dual pumps. If you not willing to spend this much money then the next best is a modified CP4. After that the VCV would be the less expensive. Anything over 1340pw you will drop rail no matter who's tune you run. Most will give you less pw so you won't drop rail pressure. If your planning on stopping at this point the VCV will work but it's hard to get and always on back order. I'm not sure about longevity no one has talked about that. You will be over maxing your CP4 pump. Who knows how long that will last.

Honestly I was waiting for you to reply bc iv been reading a lot of your posts and you were in the same position I am before your dual settup. I do eventually want to do the billet 2015 turbo , but i really didn't want to go crazy with duals as you kno it gets expensive real quick. I'm guessing with the billet 2015 turbo fuel pressure drop is going to be even more of a concern bc I'm forcing more air in and need even more fuel ? I was going
To try the vcv and fuel rails but I can't find any info about the install process or anything. Maybe you could shed some light on that.Thanks for the advice
brotha.

dseitler · Sep 2, 2014

Honestly I am running almost double your pw and have not needed the fuel rails. My problem is all about air and has been from the beginning. IMO before you go any farther you have to know exactly where you want to end up HP or you will spend a lot of money and wrong parts and still not get there. Once you have that number or idea the choices become clear and you will know what fuel system and turbo to purchase.

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