The problem with increasing the pressure is the seals where the injectors attatach to the rails plus when you approach redline fuel rail pressure drops now you lift off and you are slamming the system with more then 82 psi. Pressure is going to cause something to pop off or start leaking.

 

Bulldogger, i know you swear by the sl55 pump and say its the increase in volume that makes the difference, not the pressure.

Am i understanding you correctly that your saying the factory fpr is not a factor when running lean,and that 60psi fuel pressure is sufficient at all load and boost levels?

If this is the case, do you agree that 2 Walbro 255's routed in parallel would be as effective or more effective than the sl55 pump? It might even run too rich, but if what your saying is correct then this would settle it and prove more VOLUME is the answer.

 

Two pumps together will more then likely work. If pressure was the answer then the difference say between the 178 and 185 is about 5lbs then increasing the pump by 10 would be the answer. But Waldig increased the pressure and..... Yes but he did it with air pressure into the filter which increased the fuel flow by forcing the fuel out of the filter faster, which actually increased the volume supply.

 

#14 (permalink
not sure but we are not stock once we get the tune and a pully, the sl55's ecu is set up to give the injectories the fuel they need at a certin psi(boost) makes it work stock,, now the crossfire has a tune and a pully so the psi (boost) is higher than stock (that means the psi (boost) pushes the fuel back ,, ( example ) put air in a flat tire no problem now put air into a truck tire that already has 100lbs in it ,, the air goes in slow ir at all the same with fuel the psi set by the ecu is good for stock just don;t add boost and you are fine, the sl55 pump by itself will not change a thing on our car. (correct me if i am wrong) filter/ reg. has to be changed also. a in line pump in front of the reg will change our psi, u would need another reg to decrease the psi of fuel. now that i am confused see what you can do. jim

I have been wrong once before , so teach me,, because if i ever need more fuel this is the best and only way we have at this time and it works. or if you know of another way post it or just pm it to me i want tell anyone. jim

 

It appears the atmospheric reference port may hold a promising option. In some boosted applications, the fuel pressure regulator is boost referenced, meaning that fuel pressure rises with boost in order to offset having to overcome the increasing boost pressure inside the manifold. This is a simple way to ensure proper injector fuel delivery with varying boost/vac inside the manifold. Another way to accomplish this is with injector duty cycle, the program inside the computer handles compensating for varying levels of boost/vac. But if we were to take hostage this atmospheric port and apply boost pressure (with a check valve so that it doesn't go negative with vac) to it, now we have accomplished increased fuel delivery with increasing boost. It may be a solution to prevent going lean, assuming of course we don't exceed the fuel pump's capacity. Comments? Any experimenters?

 

been there, done that, that alone doesnt do it, tweaking the system now

 

Unless you have exceeded the pump's capacity and fuel delivery (pressure and volume are dropping off). In that case, more pump will help.

 

I added a boost line to my regulator tonight so that I can back off the low end fuel delivery and still keep my top end where I need it. This regulator has a 1 to1 ratio so for every pound of boost my pressure will go up 1 pound. I will be at the track tomorrow to see how it works. I also put a set of Nitto 315 35 17's on today so I am hoping to get some great launches. They sure look good it is a lot of meat under that car.

 

Wow Paul, you work fast! Can't believe you got those huge tires on already...Same rims? I'm thinking taller tires will hurt your times...Good luck!

 

I added boost to the regulator causing the fuel pressire to rise some. It is only one leg of the "stool" and not a complete solution, YET.

Liquids move because of a difference of pressure, flowing toward lower pressure zones from higher pressure ones.

Flow is the rate the fluid moves under the pressure difference which is needed to overcome resistance in form of friction, viscosity, and turbulence factors. More pressure more flow, less resistance more flow, lower viscosity more flow and visa versa.

Flow is caused by pressure difference so the higher the pressure delta, the greater the resulting flow. On the dual CAI I had a fixed pressure ( the atmosphere) and had to overcome friction by reducing the velocity in the pipes to minimize fluid friction and turbulence by half which results in 1/4 the overall friction. I.E. two tubes; Woody

 

Mimi the tires are actually 315 35's not 40.s my bad. Neal I said at the track I am determined to get in the 11's and the traction is just another thing that has been holding me back.

Woody you are right the regulator is not the complete fix but I can now go to the track and run safer. I am hoping that smarter people than I can figure out the rest of this puzzle. So come on Woody and Rob I am ready for your new mods.

 

I truly feel for you guy's. All these post regarding fuel pumps and regulators.... chasing lean conditions.... I sure hope you can get it all squared away.

A little refresher - - When I installed my 185mm pulley back in Feb 08 (the first guinea pig to buy and try the 185) I was so worried about running lean that I stayed off the throttle until I could get the SRT in for a Dyno tune.

Much to my surprise, I even pulled my dyno sheets tonight to re-confirm and give you straight data, I was running PIG RICH with the factory tune. 10.4 to 10.8 AFR at rev limiter thru the entire power band on the factory tune.

BTW - I had the SL55 intake and a set of NGK BKR7EIX-11 Iridium plugs installed. (Package deal from LET when they first started business - don't ask about the killer deal I got - you'll only cry) - No other performance mods installed.

My AFR was monitored with a Wideband sensor set as far up the tail pipe as possible and also with the STAR diagnostic system (factory sensors) they had at the shop.

After all the pulls and adjustments I ended up at 12.6 AFR and gained +26 HP thru the entire band.

In fact, comparing my last pull (Run #20) with my first pull (Run #1), where the AFR graph begins to climb from 11.2 up to 12.6 AFR and stays rock steady for the last 3/4 of the pull, is the same point where the HP graph climbs and stays a consistent +26HP above my first run.

My point is that if guys are running lean with all sizes of pulley's - perhaps it's your:

1) Tune - maybe in the zeal to provide the customer with a big HP gain, your ECU has been over tweaked and now you run to lean.

2) Fuel pump - perhaps it's getting weak (especially at the top end) - I was tuned at approx 2,000 miles if my memory is correct, so my pump was still fresh - with only 18,000 on the clock - I'm pretty sure it's still 100%.

Good luck, I hope you get it all figured out.

 

Its still beyond me how you never ran lean.

Interesting point about the tune. Has anyone ran lean with no tune and big pulley?

 

got a recent wideband log on the street brian?

 

Or did I have any of the IAT overtemps everyone seemed to claim I would. Prior to my coolant separation mods or after. Never a SC shut down.

No belt slip issues either - still running my factory belt without a "wrap kit". Go figure??

At 20-21 lbs of boost - Never an over-boost CEL. Not Ever. Only CEL I ever had was when my SRT6 was new and I had an faulty injector.

I even got the upgraded idler bearings from LET plus I got some killer high RPM sealed ceramic bearings from Japan for the idler and tensioner pulley's and they just sit in their package - never installed. But those I should install - ASAP even if I'm not having any issues yet. (knocking-on-wood)

But - my SRT is at the dealers right now. My factory warranty expires next month and I discovered the drivers side bottom seat heater failed (some time ago I figure) so I thought I would take advantage and get it repaired - even though I live in paradise were it never gets cold (or hot) - been in the mid 70's all week.

Nope - but I've been on two other dyno machines since to confirm results (and to test my coolant mods) Even ran three days of full-tilt-boogie runs at the Texas mile without any issues.

In fact, I'm considering removing my IAT and boost gauges and going totally stealth....

 

Going from 56 psi (stock) to 76 psi (assuming 20 psi boost) of fuel pressure with a regulator which tracks with boost should net you a 16.5% increase in fuel delivered - as long as the pump can keep up. Based on the flow chart I posted, with the stock pump I feel that this may become an issue. It appears that the stock pump might not have sufficient capacity, especially if the injectors are running near 100% duty cycle (static).

 

Brian doesn't run lean because of his stock intake plenums. They bottle neck and give a higher reading at the MAP sensors then what is actually seen in the plenums. Moddified Plenums plus 181/185 pulleys take you over the edge. Lets sue Needswings and 240M3SRT for this it is all their fault.
I'm first on the list, Oh wait I didn't use any of their stuff , but don't let that stop anyone else

 

It's not the difference in pressure, it is going from 55-60g/h (stock) to the 95g/h that the SL55 pump gives you. Up top you are loosing pressure in the rail due to lowered volume. The SL55 pump adds 35-40 more gallons per hour.

 

Regardless of the pump, going from 56 psi to 76 psi fuel pressure equals an increase in 16.5% more fuel : sqrt(76/56)=1.165 if the pump can keep up, as stated earlier.

Yes the stock pump is inadequate, but the point I was trying to make was that more fuel pressure means more fuel delivered, with the caveat stated in the original post.

 

Oh and the stock pump/injector configuration will not deliver more than ~42 gph (assuming 100% inj dc) - see the chart posted here

https://www.crossfireforum.org/forum...tml#post453333

If you extend the curves for the stock injector to meet the SL55 pump curve, they will cross somehwere around ~105 psi and ~66 gph. But it would be impractical to try to run that much pressure.