550 injectors on re-wired stock pump?

[mach1one]

My friend bought 680cc injectors, so I bought his old 550cc's and we put them int oday. I'm running a MAFT + rewired fuel pump. My question is do 550cc's pump in that amount of fuel, even on a stock pump? I'm not sure of the mechanics of the fuel system, if the fuel pump can pump in more to compensate for the bigger injectors.

I thought it compared to running a 190lph on stock injectors, but then I thought that unless you drop the f.p. down to near stock you'd just be running the stock injectors at 100+ D/C. Am I running the risk of sucking air down in the engine if I try upping the boost before I install a 190 pump? Boost is currently at 14.

I do have a fuel pump on the way, but I was still curious and trying to learn more about the fuel setup. I searched for "550 stock pump" but didn't really see any threads pertaining to my question.

 

[Bd1000Eclipse]

you need a pump for those injectors.

 

[sweet97]

I know we all like to buy go fast goodies before the "tools" to keep themrunning but get somrthing to let you know what's going on in the motor. Check out the "Scanmaster" at www.fullthrottlespeed.com
If you have a 1G it's the greatest, simplist tunung aid available. It will give you over 30 pieces of "DATA" while you are driving the car.
Knock and timing are especially helpful. The 1G runs very rich from the fatory at WOT. I have been running 550's, a GM MAF-Translator in a blow thru position, 2.5" mandrel ss exhaust. EVO exhaust, 02 housing and EVO Big 16G turbo at 18 psi on the stock pump and am able to "TUNE" it to pig rich with the Translator which is richer than 10:1 a/f.
I believe you will be OK to run the 50's but without fuel control like the Translator you wil run even richer, you won't be "pushing air with the stock pump. I have a Walbro 255 but never installed it because I have plenty of fuel available even in 4th gear at 7000 RPM.
I am installing a 50 trim today and expect to be able t run 14 PSI on the 550's. I have a friend runnng a Buschur 20G with 550's and 15 PSI until he gets it tuned. mark

 

[mach1one]

I have a datalogger and we quickly tuned it to run on 550c's, they work great. idles fine. Thanks for the info sweet97, my car wanted to run pig rich on the stock system. I need to finish tuning it and see if I can run any more boost on it.

 

[sweet97]

Logging what's going on is the key. One car may have a "tired" stock pump and need to be replaced, yours and mine were OK. Don't take chances, LOG!
I could run 18 PSI with the EVO big 16G and the 550's but I could adjust flow. How are you controlling the fuel flow? mark

 

[yo2001]

May be it's time for us to go datalog

 

[sweet97]

yo2001, great times on your EVO. What are your mods? You have done a great job getting those times from the big 16G. What do you mean by your statement "let's go datalog"? Mark

 

[mach1one]

:laugh: yo2001 lives in the same city I do. He's showing me the ropes and sells me his old stuff. Hopefully he'll upgrade soon so I can get his 16G We got a few things to do today but I"m gonna try to get out and log it.

I don't have an afpr yet, but I need to pick one up. I adjusted the base setting on the maft to the 550 and it runs pretty good w/ the idle richened a couple clicks and mid/wot at zero.
I think my o2 sensor is dead, or I need to check the connections on the o2 sensor. Came w/ a crappy tunnel connector, I'll solder the wires together and see if it fixes it. I replaced it about 4 months ago.

 

[mach1one]

After a couple days of driving, my FTLT is 97%, FTMT is 98% and FTHT is 100%, so the basic 550 setting is pretty close.

 

[Kevin Jewer]

Just a few thoughts...

550s can only move 132 LPH at 43 psi. According to RREs page (http://www.roadraceengineering.com/fuelpumpflowrates.htm) at 15 pounds of boost and 14v, the stock 1g pump does 100 LPH and the stock 2g pump does 131 LPH. So on a 1g, you wont be able to max out those 550s on th stock pump, according to the math. The math and the real world dont always agree though 450s flow 108 LPH at 43 psi, so the 1g pump is pretty well matched to those at stock boost levels.

You should choose your injectors and pump for the amount of power you need to make. Not trying to match them to each other. For example, if you bought 950cc injectors just because you have DSMlink and you can, doesnt mean you need a massive fuel pump if you are only going to make 300 whp

This reply promted me to check out my setup, since my AFR goes lean over 7k rpm. The 255 low pressure, which I believe is the variant I have, flows 183 LPH rewired at 30 pounds of boost. The 950s do 228. So at roughly 80% IDC I should be running out of fuel. I'm somewhere around 85%. Go figure.

 

[sweet97]

As I stated in an earlier reply I have been running 550's with an EVO set-up at 18 PSI and had no problems running a 10:1 A/F ratio at WOT in 4th gear at 7k RPM. Mark

 

[Kevin Jewer]

Fueling is based on airflow per rev (or airflow per time, converted), of which there is no mention in your thread. Airflow varies greatly at a given boost pressure between different setups You might get away with it, but the next guy might not. All depends on how much of those 550s you are really using. Certainly appreciate the datapoint though. And like I said, the math doesnt always equal what you see in the real world, its just a guide. But in my case it appears to be accurate. AFR rises from setpoint of ~12.5:1 to nearly 14:1 over 7000 rpm.

 

[mach1one]

very interesting....thanks for the info. that's what I was looking for

 

[sweet97]

I can give you engine airflow in Hz. Also for all I know the car has an upgraded pump, I am onlyststing what the 550's do in my motor and I recommended that anyone upping injectors must log to be sure they are running witin a safe limit for their motor. mark

 

[pinknuggit]

I can give you engine airflow in Hz.

how???

So you can say your engine airflow is 1300hz. :laugh:

hz = cycles per second fo a sine wave.. you could equate your engine revolutions to hz, but it would be useless....

 

[sweet97]

Please bear with the fact that much of this is new to me. If something I say makes you laugh that's cool because laughter can be rare for some folks.
I don't know how you determine airflow but the "Scanmaster" I use from full throttle has airflow as one of the engine data available. It is given as hertz. It's the airflow sensor signal. apparently it is not useless to the ECU.
This is beginning to become one of the many posts where guys just bicker about nothing. I run 550's on the stock pump and can maintain a 10:1 a/f at 7000 RPM in fourth gear. Doesn't that answer the original question?

 

[Kevin Jewer]

I dont think anything is funny about your post. We're all here to learn. But it doesnt really answer the question for everyone, just setups similar to yours. A 14b car at 18 psi and my car at 18 psi would have very different fuel requirements Boost just isnt a good indicator of airflow, and thats whats used in the air:fuel ratio. But for poeple with similar setup to yours, its a good data point as I said above. Just not an absolute

 

[sweet97]

Your statement that we are all here to learn is right on. Unfortunatly there are way too many guys(not you) that are allowed to belittle, swear at and disrespect fellow members in a big way and I personally find it immature and disgusting. Yeah let's work together and weed out the guys like the one who called a fellow member retarded who ought to be shot. Thanks for uderstanding I gave what I had to offer not knowing it would not work for all but at least for the originator of this post it did. mark