easing off the throttle instead of side stepping...

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Re: easing off the throttle instead of side stepping...

Postby RCCUMMINS89 » Mon Jan 13, 2014 11:55 am

Caleb - you are thinking correct.

The only way a lift pump can help is if there is a situation where one is sucking the case pressure dry. Increased inlet pressure can help the vane pump keep up.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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Re: easing off the throttle instead of side stepping...

Postby BC847 » Mon Jan 13, 2014 12:24 pm

Caleb,

Up until recently, I fell into that catagory of running lower than stock POP-pressure. I've since reset things back to stock/OEM with the installation of new injector nozzles within the last two or three weeks ~ no improvement.
FWIW, I feed my VE IP with just shy of 20psig. WOT has the IP pull it down to no less than 18psig. (As measured at the fuel pressure regulator's output, which has maybe 18" of 3/8" ID fuel-line between the regulator and the IP).
David

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
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Re: easing off the throttle instead of side stepping...

Postby DodgeFreak » Tue Jan 14, 2014 8:01 am

What would happen if you plugged or slowed the return on the injectors?? I dont know anything about injectors really, just wondering...
92 D350 Cab and Chassis. Auto stock, wiring gremlins. 330k miles
92 W250 Ext cab rotted completely out. Auto, pump maxed, 215 ppump nozzles, Denny T2 pin.
85 D350 single wheel, converted to cummins, getrag, turned up 2 turns and afc screw flush.
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Re: easing off the throttle instead of side stepping...

Postby Sutter1stgen » Tue Jan 14, 2014 11:30 pm

1STGENFARMBOY wrote:
Sutter1stgen wrote:I'm still getting symptoms at the end of the 1/4, even with my airdog. It's not as bad, but still noticeable.

Not side stepping is the only real cure. But when you have to backup at the end of the track, because you didnt get off the skinny pedal soon enough, it can be a little embarrassing. Hahaha.



get back in it and drift around the corner... :lol:


I like your style :D
Eric

91'w250 with a new pump. This one doesn't chase itself around in a circle.
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Re: easing off the throttle instead of side stepping...

Postby xohcef » Wed Jan 22, 2014 2:30 pm

Quick thought then. Blow off valve probably aid the situation a bit as well then? Am I thinking right?
93 d350 extended cab dually, NV5600, he351cw, DDP stage 3, industrial man ported, ported head, 60# springs, 354 spring, holley blue, aeromotive fpr, South bend single disc/hydros, kelderman dual bag.
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Re: easing off the throttle instead of side stepping...

Postby BC847 » Wed Jan 22, 2014 3:07 pm

xohcef wrote:Quick thought then. Blow off valve probably aid the situation a bit as well then? Am I thinking right?

I don't know that it'd be quick enough.
David

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
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Re: easing off the throttle instead of side stepping...

Postby RCCUMMINS89 » Wed Jan 22, 2014 3:42 pm

Your boost pressure increases cylinder pressure. The cylinder pressure is what is killing things. So dropping boost instantly still wouldn't have an affect on said cylinder(s) with the extreme pressures.

At least that's what my head is telling me.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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Re: easing off the throttle instead of side stepping...

Postby cmann250 » Wed Jan 22, 2014 4:05 pm

RCCUMMINS89 wrote:Your boost pressure increases cylinder pressure. The cylinder pressure is what is killing things. So dropping boost instantly still wouldn't have an affect on said cylinder(s) with the extreme pressures.

I agree with that. Say you could dump boost at the intake horn the instant you let off the throttle. (I think that's impossible, btw) The head is still nearly fully charged. Maybe you wouldn't get air in 1 and 6, but 2, 3, 4, and 5 would get air pushed up in them. Just think at 3000 rpm, a cylinder is hitting 50 times a second.
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Re: easing off the throttle instead of side stepping...

Postby RCCUMMINS89 » Wed Jan 22, 2014 4:30 pm

50 times a second........man that's a lot when you think of it that way.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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Re: easing off the throttle instead of side stepping...

Postby BC847 » Wed Jan 22, 2014 6:25 pm

In the Bosch "Diesel distributor fuel-injection pumps" book, the issue is referenced in passing while talking about the different designs of delivery-valves used with the VE IP (page 23):

Constant-pressure valve
With high-speed direct-injection (Dl) engines, it is often the case that the “retraction volume” resulting from the retraction piston on the delivery-valve plunger does not suffice to reliably prevent cavitation, secondary injection, and combustion-gas blowback into the nozzle-and-holder assembly. Here, constant-pressure valves are fitted which relieve the high-pressure system (injection line and nozzle-and-holder assembly) by means of a single-acting non-return valve which can be set to a given pressure, e.g., 60 bar (Fig. 13).


FWIW: The DVs on my heap are the absolute basic spring-loaded plunger with no retraction-piston (ours are Full-Cut stock/OEM) nor special valving.
David

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
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Re: easing off the throttle instead of side stepping...

Postby fatty » Mon Feb 17, 2014 8:50 am

fatty wrote:He doesn't have to say who it is. The guy is such an arrogant tool I'd say most of us knew who he meant right away.

Other than that, my brother Soggy runs an A1000 and had the same problem many times with 6x16. I think he said since he had the engine rebuilt and a reman IP along with SDX 5x18 it doesn't do it anymore. I'll ask him since I'm not positive on that.


I should add to this. I remember now that when Soggy's engine was rebuilt the pistons were shaved for a big cam, resulting in a compression ratio drop (15.5-16 IIRC) To me that further supports the compression blowing into the injector tip, since with lowered compression it quit doing it.
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Re: easing off the throttle instead of side stepping...

Postby soggy » Tue Mar 18, 2014 7:15 pm

I think it's more like 14.5 to 15-1 (bad idea with a VE) but yeah, it hasn't had any problems with the lower compression so I think you guys are on the right track. Regardless of what that one guy says.
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Re: easing off the throttle instead of side stepping...

Postby fatty » Wed Jan 21, 2015 9:41 pm

Been thinking about this lately, I recently put some 6x13 @ 80 lpm in my 91.5 and have never once had this issue. I've (accidentally) let off hard enough to bark the turbo really bad and never had even a hiccup from the engine. Making 45 psi with pump against the head...
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Re: easing off the throttle instead of side stepping...

Postby RCCUMMINS89 » Wed Jan 21, 2015 10:14 pm

May be because of the....not huge timing with that large of injector......plus the low drive pressure with that setup.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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Re: easing off the throttle instead of side stepping...

Postby RCCUMMINS89 » Wed Jan 21, 2015 10:15 pm

I had less of a problem with larger injectors, slower burn, and larger turbo.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.
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