Honda D Series Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
748 Posts
Discussion Starter #1
Hey guys,

Going to be chasing some extra power this year with the use of e85 and nitrous.

Currently running walboro 255, Id 1000cc's, oem fuel pressure reg (45psi fuel pressure) and factory fuel lines.

Currently on pump fuel I'm at 50% duty at 20psi. Always liked the piece of mind use oem genuine Honda for a constant fuel pressure.

Reverently gone to a walboro intank pump however torn between to changed injectors to larger or go to a adjustable fuel pressure reg - or both. Any advantages running higher fuel pressure ? Would still like to at best keep a nice idle and light throttle afrs. I always thought rule of thumb to not go more then 85% duty cycle on injectors etc

Thoughts ?
 

·
Registered
Joined
·
2,003 Posts
I am sure you can bump up the pressure quite a bit, and gain more flow out of them, but that will likely require a fuel pump upgrade. If you bump the basline from 45 to 70 and add 10psi more boost your pump will have gone from having to produce 65PSI to having to produce 100PSI, which will cause your fuel pump volume to fall off pretty hard.
 

·
Registered
Joined
·
748 Posts
Discussion Starter #3
Yes but any advantage to higher fuel pressure ? As in better atomisation or combustion etc ? Easier to achieve a nicer idle ?
 

·
Registered
94 Integra
Joined
·
1,225 Posts
Thoughts ?
98% of stock Honda regs for b/d/h/f motors do not flow enough for >200lph. Running a 255lph pump usually results in increased fuel pressure at idle. If that's the case for you now, increasing base pressure will require adjusting any low-load fuel cell where that's happening.

The 85% number is because older injectors had very slow response and not built for it (continuous vs intermittent). They'd lose linear response & literally overheat. Resin in the coil melts and they lock up, etc. They also didn't have such large injectors on average. Newer injectors like Bosch EV14's can reliably stay at 95% up to 9000 rpm with linear response & not overheat. Larger flow actually helps since the large volume of fuel helps cool them.

Speaking of heat, additional pressure will require more power from your pump which means more heat. If you don't like adding heat into intake air, you shouldn't like adding it to your fuel. If your injectors atomize fuel well, more pressure may not have any noticeable change. Some motors like the VR38 (GTR) have problems not atomizing fuel all that well, which is made worse by very rich mixtures by dumb tuners.

One other thing is how fuel pressure affects your pump's flow. The higher the pressure, the less your pump flows. You probably aren't close to your max but the 255 (HP or not) isn't a stellar choice for high pressure.
 

·
Registered
Joined
·
748 Posts
Discussion Starter #5
hey mate. nice response - it almost sounds like what you are saying is that the oem fpr can actually become a restriction higher flows. hense when i change to a walboro 400 - i should see higher base fuel pressure again. But if this is the case - under full load is possible that fuel pressure could drop as the volume is taken by the injectors etc... not a nice thought.

not your how to skin this cat. maybe just

Walboro 400, stock lines, ID 1000cc + adjustable FPR @ a higher base pressure. 60psi etc
 

·
Tape-R taper/driver
EC3, ED8, ED9, EE5
Joined
·
574 Posts
HiProfile touched on most of it, the only thing I'll add is that increasing fuel pressure will also increase the boiling point of the fuel. That's why you see many of the late model OE returnless fuel systems typically run between 50-70psi to counteract the fuel boiling in the rails.
 
1 - 7 of 7 Posts
Top