DaveJackson

iTrader: (5)

So I bought a silly car mag to pass the time in an airport and came across a TT 370Z (I know - different platform, but bear with me) that seems to be putting out a lot of horsepower on what is listed as a Walbro 255 L/hr pump. If I'm allowed to post a relevant link, it is here: http://seiboncarbon.com/blog/2012/08...l-nissan-370z/

It seems that folks here are using/recommending larger fuel pumps for less power than this, so I'm wondering if I am missing something. The stats say this car is at 550hp, although for some reason they are stating "estimated" so maybe that is the whole story and the car is nowhere near that. I doubt it's that far off, though.
Putting aside that it's not a VQ35, it seems obvious that more fuel is going to have to be consumed to generate more power and I thought that folks here felt that going much above 500hp required a larger fuel pump than a 255.
How do you determine that the bottleneck is the fuel pump? Is it possible that people are using larger fuel pumps than needed? Is there a data logging method used on a dyno to determine that "everything else is sized adequately and your fuel pump is holding you back"?
Is there a tried and tested rule of thumb chart for fuel pump sizing?
Hopefully there is a simple explanation. I don't want fuel pump sizing to become like car amplifier power wire sizing where people are using 10' of 2AWG wire to supply an amplifier that will only put out something less than 1000W just because an alleged expert told them to.
Appreciate your input!

jerryd87

iTrader: (4)

each platform is going to be different there isnt enough details on that car to really be able to call bs or not. the major thing that limits fuel pump flow is boost pressure, since we use rising rate regulators to keep our fuel injectors flowing enough fuel we are reducing how much the pump will flow. the engine is bigger meaning its likely using less boost so the pump will flow more, similar to how for our platform its recommended around 550 to switch over but most evo guys recommend going bigger then a 255 at around 450-500, but even some of them have made close to 600(although i wanna say most around there where with the addition of meth.)

as for how to tell? only real way i know is rouch calculations, rc has a decent calculator for bhp to size injectors for a set power level which can be used to determine injector needs. from there can look at a flow chart for your pump and see if that number falls on the chart at the expected pressure you will be running. its only going to be a ballpark though only sure fire way is to put the car on the dyno and see when fuel pressure starts to drop(since this indicates the pump cant push enough fuel for the regulator to be a restriction anymore.)

Boosted Performance

iTrader: (14)

The best way to keep an eye on of fuel is to have a fuel gage right on the rails. If you see the fuel pressure starts to fall up top, there is a fuel supply issue. On the VQ's in general it seems that about 550whp is the max a walbro 255 can provide. But then again, fuel injector size will make a difference as well as fuel pressure.


If you read the article again, they are saying the stock 370z has 332hp (this is manufacturer rated flywheel HP), and then they say the car puts down about 550hp with the turbo kit. So I would say the 550hp is also flywheel power, and not power at the wheels.


The standard fuel pump on all my kits is a 340lph pump, and in addition to that the 370z kits will be using 750cc injectors, as suggested by a couple of tuners. This combo yielded 550whp on the test mule without any fuel issues at all. That is about 620hp at the flywheel if a 13% drivetrain loss is used.

DaveJackson

iTrader: (5)

Yeah, I was thinking the same thing, I just still thought it sounded high.
Good points about the boost pressure fighting the fuel pump. I just wanted to make sure that people were actually measuring something to determine if a pump was out of uhmmpf.
Thinking to what a pump curve looks like, noticing a significant drop in pressure is indicative that the pump is running on the far right of its curve and doesn't have much left to offer, I suppose.
Thanks for the help, guys!

djamps

iTrader: (1)

Mid 5's to the wheel is about the most you can hope for with a 255lph... there are a few that make more and a few that make less. It all depends.

binder

iTrader: (8)

Yep, it also depends on dyno. Every correction is different as well as just regular variances.

Each fuel pump has it's own limiting power and it depends on the efficiency of the car as well. My 255 ran out on hal's DD dyno at 465hp with a supercharger. He told me low 500's is where he usually sees them run out which on another dyno might just read a higher number due to dyno variances.

Also the resistance the fuel has to see. From what I gathered from Charles as CJM the 370z fuel basket and system is far less restrictive than the 350z. If that is the case then the same fuel pump would be able to produce more power due to the less work on the pump. The same reason you can get more power out of a 255 with upgraded supply line and rails over a 255 with a standard return system that uses the small stock supply line and small fuel rails.

I think quite a few people here over estimate how large of a fuel pump they need for their stock block or mild built block. Guys with 1000cc injectors and twin pumps for a mid 500hp is just wasted money.

TopgunZ

Unless your on E85.

str8dum1

iTrader: (11)

you can make 500 on E85 with the latest crop of 300+ lph pumps.

E85 is a waste of money for only mid 500whp.

thatv35guy

iTrader: (1)

I’m planning on running E85 was I get my motor back together…

I was planning on running the Walbro 485 pump and 1000cc Deatschwerks injectors on my car. I’m shooting for 550whp… E85’s a safety measure for me if that makes sense… (I live a quarter mile away from a station)

str8dum1

iTrader: (11)

its just as safe as 93 octane at that power level but with half the mpg's.

Obviously since its readily available, its a no brainer, but for some that would have to go out of their way to run it at that power level, its not worth it.

Boosted Performance

iTrader: (14)

I was thinking the same thing...why spend all the money on fuel support when you can do the same thing on pump.

One of my customers just made 610whp with the 6266, with a 340lph fuel pump and 850cc injectors. According to the tuner there was another 30-40whp left on the table, so a conservative pump gas tune. This was also a simple short block build, no head work, stock DE cams.

rcdash

iTrader: (18)

Think a walbro 485 at 18 volts with HKS 1000cc will be pump or injector limited on e85? I am hoping I can squeeze 700 to the wheels out of it.

TopgunZ

I drive by an E85 station on my way to work and theres one the opposite direction a half mile away also. Thats why i was going to go that route too.

I am currently on stock block but im guessing im pumping some pretty hot air into my engine with my twin charge setup. I wanted it for the cooling properties (safety). Plus it spools your turbo quicker with 30% more exhaust than gas.

Oh and im in CO so we only get 91 pump.

I actually just today purchased a dual output Intercooler guage. Im going to tap just before the throttle body and one in the plenum. Trying to get an idea of what temps im pushing in.

TopgunZ

Go with the 1000cc ID's. From my understanding they are more stable and can be ran up to 1200cc's.

Im going to replace my factory supply line with a bigger one also.

binder

iTrader: (8)

you can't run anything over the max which is what they are rated at. If you are talking about increasing fuel pressure then any fuel injector will flow more with that so there isn't a limit to which fuel injector will work better than another.

He already has hks and has a great tune on it. I run the hks as well. No reason wasting another 800$ on injectors when HKS are great injectors as well.

You need larger rails to support injectors that big. Large injectors on stock rails is a waste of flow.

TopgunZ

I seen a write up (wish i could remember where) where they tested a handful of injectors and the ID's were just more stable at max and when pushed over max still maintained the best stability of proportions and atomization. However, I am not saying the HKS's are not just as good, i dont think they were in there. But it kind of sold me on the ID's.

I wonder how many people think that the switch to E85 vs. 91 for safety is a waste. It makes sense to me that if you are dumping 30% more fuel, of fuel that has immense anti-knock properties and burns much cooler, that your chances of pre-ignition are going to be lower and your cyclinder temps will be lower.

binder

iTrader: (8)

It's a waste for low power in the sense that it costs a lot of money to support the same hp (pump and injector upgrades) as well as the per mile fuel cost. If you can provide a 100% safe tune at 550hp on pump gas without pushing the limits then doing 550hp build on e85 won't be any safer. Now if you are talking about a person on the ragged edge of timing at 550hp they yes, going to a higher octane will be more safe. On a stock block setup octane is FAR from the limiting factor so there should be no question of safety due to octane. Do people get knock on pump gas and blow stock blocks up, yes, but not due to proper octane, due to proper tune or defective parts. I would guess the same engine would still fly apart on e85 due to the lack of brains in the tuner or the metal fatigue of the parts.

I'm on e85 for 652hp. If I was to get here on pump I would be pushing it pretty close to the edge. Therefore I would be on race gas. The cost of e85 per mile over race gas is cheaper so I use e85.

For a 550hp build and you are worried about safety it would be cheaper per mile to put a gallon or 2 of race gas with the pump gas and provide just as much octane while being considerably cheaper than e85. So if i was concerned that a dumbass tuned my car I would leave the expensive e85 costs out and just put a little race gas in with my pump gas. 19 gallons of 91 plus 1 gallon of c16 would give you right about 93 octane. I could do the math per mile to show how this would be probably half the cost of e85 per mile if you want but I think you get my point.

jerryd87

iTrader: (4)

something you need to remember is knock and pre ignition are two different things and fuels act differently, for instance e85 has great anti knock propertys, however it is actually more susceptible to preignition apparently(researched not known for fact) for the most part that shouldnt be a issue though since our combustion chambers are so smooth compared to some and the ethanol itself should keep carbon from building up.

str8dum1

iTrader: (11)

thats why tuning on a dyno is important with E85. Its very easy to go way past MBT, and that will cause preignition and a ruined motor in short order.

TopgunZ

Ok. Points well taken. I have been on the rocker if I should go to E85 or not. It would require larger injectors and it would yield 22% more cost at the pump.

However, I have read and read on E85 vs. meth and 90% of the time i hear that if you have access to E85 then its way better than meth.

Many people run Meth on their stock block to ward off detonation and cool the intake temps. So would you argue the point that both meth and E85 are pointless on stock block numbers?

Remember im not using it for the HP increase but the safety factor. I can sell my DW600's and buy 1000's and spend $300 to $400. Or i can buy an injection kit for that amount and have all of the added complexities meth can bring vs just pumping my tank.