So with the new full 3inch system I decided to do the dirty and see what difference it would make if the cat "fell off" Aside from maybe 15whp at rev limit and a bit more on the spoolup it really made no difference. Without software changes I get a bit of overshoot. I can tune that out. like before but the big problem is that the injectors are maxed. Fuel pressure is not the problem that stays nice. So next step is something bigger than the 750cc or more fuel pressure and some sort of magic pump to flow at those pressure. 43 base plus 30psi.. it out of the range of most. This is with a stock head, only 264 cams JE pistons and a top mounted GT 3071.64 Base boost is like 12psi Boost and inlet temp measured at inlet manifold brake port. A/f In the downpipe that is based on 14.7= lambda 1 but this is E85
it was quite a bit hotter this time 95 ambient vs 70 so in the cold it might make a little more. however does not good to command more fuel if the injectors are full on. Might have to turn it down.
Walbro 255.
This is what it looked like at lower power on the stock pump. OilP is fuel rail pressure. Was within .5psi or gauge tolerance across the run. Normally I look at the text data recorded every .1 seconds, you can see much more clearly that way. But the graphs tell the story easier.
So is the comparisson in the dyno the new 3" without the CAT (i.e. Blue line) vs. the 2 3/8" Remus/Viggen sport exhaust (i.e. red line)?
If not and it was the new 3" both w/ and w/o the CAT, how to the numbers of the 3" compare to the Remus? Did you also check the backpressure of the new 3"?
Fuel pressure is not the problem that stays nice. So next step is something bigger than the 750cc or more fuel pressure and some sort of magic pump to flow at those pressure. 43 base plus 30psi.. it out of the range of most.
The bosch 044 will support it and will fit into the "bucket" with the same mods as the -040 model. At the same time take care of "short-circulation" among the T-piece which is tiny std.
Here is a flow vs pressure of the -044 bosch http://www.fuelsystem.co.uk/new_page_10.htm
flows someting like 3.8l/min with 5bar resistance while the Walbro manages~2l/min and the -040 2.35l/min
I think what Vigge is saying Nick is that you may need more flow than the stock fuel hoses and rail can deliver, no matter how much the pressure is upped. Is that correct Vigge?
Vigge:
What is the standard T-fitting you refer to and what to watch out for on it?
Are you talking about the fitting in the top of the 044 pump? I think I used a banjo fitting on mine. How much bhp can the stock lines and rail support?
This may mean nothing in regards to our cars, but I had a car that had one fuel pump. We then added another when we added a super charger along with bigger injectors. It ran pretty damn good but what helped out and was the key to the puzzle was changing all the fuel lines (increasing the size) of them all. We had these 2 pumps, huge injectors, but these tiny fuel lines.
Just a guess, but I doubt it means anything.
Beat me to it by minutes^^^^^
Yeah you're probably right about the t-fitting being the one in the assy Mark i forgot about that one-the white or clear plastic one right?
I think Maptun or Nordic go to AN lines and a larger rail for above like 450 or 500 hp right?
I guess it would be an easy calculation if someone feels like doing it.
First injectors:
If you figure your injectors are like Nick's (750cc), then you know the volume flow rate (v dot) but this is also times 4 since there are 4 injectors. Basically calculating for max injector flow which is at 100% duty cycle. You would just have to make sure the cross sectional area of your fuel line and rail at the smallest area could flow that amount of fuel or more and that the pump could supply the needed fuel.
So:
750cc/min. x 4 injectors = 3000 cc/min. (this is the max req'mt of the fuel system)
Anyone know the inside diameter of the t-fitting in the fuel pump assy?
I think it's around 1/8" i.d. but not sure.
Now fuel pump:
From the specs I've seen, the Walbro 255 flows a volume flow rate of 255 liters per hour at 40 psi.
So, to convert this volume flow rate from liters per hour to cc/min.:
255 liters/hr x 1000cc/liter x 1 hr/60 min. = 4250 cc/min. -so at 40 psi the fuel pump can supply the needed fuel to the injectors at 100% duty cycle, but can the rail and lines keep up with this demand? And also rail pressure may be up to 5 bar or higher depending on the amount of boost being run. For 2 bar boost the fpr will hold rail pressure at 3 bar + 2 bar = 5 bar = roughly 75 psi! Not sure what the Walbro 255 will flow at 75 psi.
Anyone know the inside diameter of the t-fitting in the fuel pump assy?
I think it's around 1/8" i.d. but not sure.
With 75psi the walbro will flow according to specs 3200cc/min
The std T-piece has a diameter of ~3mm and the line which goes to fuel rail is from the "T", and the "straight" passage goes to the internal return making the solution even worse.
Roughly a year back a friend of mine swapped his 750cc's to 1000cc's when fueling became a problem (dc 100 afr too lean), but the afr dropped only by whopping 0.1afr when the 1000's where run dc 100% as well, so it was kind-of obvious that the 750's where not main limiting factor but the other fuel delivery parts where and taking care of them solved the afr problems as well.
When we went to 400whp the fuel pressure measured at the rail and compared to manifold pressure was decent across the dyno run. I have to get a new solution to connector that we do not have to remove the valve from the connector. My hose that connects does not like E85 and worries me. Rather not blow that on the dyno.
If there was not enough flow the pressure would be less.
When we went to 400whp the fuel pressure measured at the rail and compared to manifold pressure was decent across the dyno run. I have to get a new solution to connector that we do not have to remove the valve from the connector. My hose that connects does not like E85 and worries me. Rather not blow that on the dyno.
If there was not enough flow the pressure would be less.
Here is a datalog to look at. Dashed lines with bosch 040 in the std bucket all other stuff std, injectors 780cc/min.
Solid lines with bosch 044 from pump with 8mm line to t-piece and 5mm line back to bucket, 8mm to bucket like. Other lines and injectors the same. Affect to AFR 1.5 at 6500rpms almost 2afr at 7krpm. Note boost, DC, MAT are the same. http://www.stcf.net/viggen/044.jpg
btw the 040 flows better than the walbro when line pressure is higher and the car produces roughly ~480bhp.
Yeah that T-Fitting messes up alot of things. When I took my assembly apart I didn't realize how small it was until I saw it.
A12 your right, no matter the size of the fuel pump, it gets to a point of diminishing returns, you just cant force enough fuel through that fitting regardless of the force. And like Vigge said, the fuel to the engine takes the 90 degree turn to inhibit flow more. Although iirc with minor corrections, you can rework the flow patterns inside the assembly with reasonable ease.
That is strange, my 9k aero has 8mm line in the basket anyway and I think my ng 900 fuel also was 8mm. I thought he meant he did better by adding 8mm line all the way from pump to rail... That is the resriction they talk about, fuel line size and some nice 8mm aeroquip line or whatever it is maptun sells would probably work well.
I read it as smaller pump did better with larger fuel line than larger pump and stock fuel line.
Awesome info Vigge!
When I installed my 044 pump like that in the basket, I also used a piece of submersible flex line like that, but only to the T fitting. Did you use the same size line for all 3 pieces and where can you get different sizes of submersible rubber line like that? The NAPA auto parts store near me only has one size. i know Gates hose company makes it bui it's hard to find over here in the USA.
I did not realize that T-fitting would be such a major source of restriction.
Also, the banjo connection to the Bosch pump coul be a restriction as well correct? If I remember correctly the hole in th ebanjo fitting is not that big. Did you drill it out or something?
Thanks for all the info on this.
Oh, ok, I guess when I do my Holset turbo and go for 650bhp, I will update the fuel pump, the inner basket fuel lines and the entire lines to fuel rail.
John
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