getting maximum fuel not maximum throttle travel

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getting maximum fuel not maximum throttle travel

Postby fatty » Sat May 10, 2014 8:30 pm

So a while a back I messed with my throttle shaft and the cable to get some more travel out of it. Well, I got more and now it pulls back too far so that it makes less power at WOT than it does just a little under WOT. I remember this has been discussed a few times on here, but I've never seen anyone talk about the fix. I plan on putting my idle screw back in just a little to limit travel, but other than the ol butt dyno, how do I know when I've got max fuel?
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Re: getting maximum fuel not maximum throttle travel

Postby RCCUMMINS89 » Sat May 10, 2014 9:27 pm

Quite a few things could go on....

1. dropping case pressure, thus losing timing... thus losing power.
2. flooding the system out with too much fuel...thus losing power.
3. on mine I actually could see my fulcrum lever doo hicky moving back after too much throttle, I really still don't know why as I haven't played with another one that will do it.

Ways to check... boost, egt readings... smoke.. and then butt dyno. I know, I don't gain a thing after about 1/2 throttle anymore.
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: getting maximum fuel not maximum throttle travel

Postby cougar » Sun May 11, 2014 9:17 am

I see you have an Airdog. Are you monitoring fuel pressure perchance?
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Re: getting maximum fuel not maximum throttle travel

Postby BC847 » Sun May 11, 2014 9:25 am

RCCUMMINS89 wrote:1. dropping case pressure, thus losing timing... thus losing power.


That's an ongoing issue with my mess.

Seen it illustrated on a dyno a while back.

Image
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Re: getting maximum fuel not maximum throttle travel

Postby fatty » Sun May 11, 2014 12:14 pm

cougar wrote:I see you have an Airdog. Are you monitoring fuel pressure perchance?

I did for a while when I first installed it until the gauge broke. It was pushing just over 20 psi at idle IIRC.
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Re: getting maximum fuel not maximum throttle travel

Postby fatty » Sun May 11, 2014 12:17 pm

BC847 wrote:
RCCUMMINS89 wrote:1. dropping case pressure, thus losing timing... thus losing power.


That's an ongoing issue with my mess.

Seen it illustrated on a dyno a while back.

Image

BC what have you done to remedy this. I guess if I was willing to spend the money on renting a dyno for a few hours, I could figure it out easy enough.
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Re: getting maximum fuel not maximum throttle travel

Postby cougar » Mon May 12, 2014 9:29 am

fatty wrote:
cougar wrote:I see you have an Airdog. Are you monitoring fuel pressure perchance?

I did for a while when I first installed it until the gauge broke. It was pushing just over 20 psi at idle IIRC.

Just a thought. RC mentioned too much fuel. With 20psi at idle it may be a factor. If you can, turn it down to 15 and see what happens. Also with the issues Airdog has been having with their pumps, your WOT pressure may not be what you hope it is. Something to check anyway.
RIP 91.5 W250 5 speed. The great experiment.
92 W250 HD 47RH with Compushift. Upgraded H1C to 62/60/16, Scheid Lightning VE, 60# valve springs, DAP 7X.010 injectors, 4" DE exhaust, home made cooler tubes.
01 2500 "the work truck".
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Re: getting maximum fuel not maximum throttle travel

Postby BC847 » Tue May 13, 2014 3:10 pm

fatty wrote:BC what have you done to remedy this.


I'm embarrassed to say: Nothing as of yet. :oops:

Actually, that's not accurate. For racing, I set the static timing a little over advanced, so that when running WOT, the dip in timing is compensated for. Of course, at a more normal/regular throttle, it's a little over advanced. :roll:

It gets back to I'm demanding more than the stock/OEM IP vane-pump can move. I've got a fuel pressure sensor in my fuel pressure regulator that monitors that fuel pressure going to the IP two feet away (through 6AN plumbing). With the regulator set to about 18psig, I'm pulling it down to no less than 16psig.

I suppose I could whittle a little on the IP's fuel input passages, but I'd most like do better with a higher incoming fuel pressure. That being said, I figure my Walbro 392 fuel-pump is the bottleneck. It can deliver the pressure, but not maintain it at the volume WOT wants with these stupid-big injectors. :?

Dunno what I'm gonna do about it right now.
David

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Re: getting maximum fuel not maximum throttle travel

Postby oldestof11 » Wed May 14, 2014 6:12 pm

BC, RonA had a 392 pushing into a piston lift pump for awhile. I don't remember how much he made but I would assume more than 700hp.
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Re: getting maximum fuel not maximum throttle travel

Postby directinjktn1stgen » Wed Aug 20, 2014 6:29 pm

I have the same problem! I came up the smart idea to cut the throttle lever so there would be nothing interfering with travel on top of re indexing it as well. However i have stock injectors that are not in "sync" and a factory lift pump. Soon enough thanks to RC ill have a set of 5x.012 injectors along with a 15 psi spring, when i was monitoring fuel pressure with what i have i had 4psi at idle and 1psi and WOT. Basically when i give more than half throttle past 45mph power basically packs its bags and leaves!
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