2Lucky2tha7

iTrader: (3)

First off, I'm running a Megasquirt ECU, not a STOCK ecu.
Anyway.
I searched alot and I can't seem to find the answer that I'm looking for.
On my street-ported N/A, I currently have my regulator set to 50 psi static fuel pressure (aka: fuel pressure is currently at 50psi at WOT) and I'm wondering what psi to settle with, because I'm in the process of re-tuning my fuel map for my 550/680 injectors, so now would be the best time to set this. I'm wondering how high I should go. As I searched, the only thing useful that I found was what ReTed said a few years back in a post:
"In the top-feed ND fuel injectors, we don't see any gain after going past 70psi of fuel rail pressure.
So, keep the maximum under 70psi."

I'm still running the stock fuel pump (TII pump if it makes a difference---can't remember if it's the same as the N/A pump or not).
Reason for doing this? Looking for best fuel atomization and better efficiency without any ill effects.
If I set my pressure too high, will it strain my fuel pump too much as it tries to hold that pressure?
Any suggestions??

-Brian

2Lucky2tha7

iTrader: (3)

anyone?

anewconvert

iTrader: (1)

Dude, what in gods name do you need all that fuel for? You arent boosting, and a streetport cant possibly use all that fuel. Unless you are planning to run a dry shot of nitrous, a large dry shot, you will be seeing a very difficult time tuning your fuel curve with those injectors.


That being said, 60 psi is what injector flow rate is measured at. So at 50 psi you are running less fuel per injector event than the injector is rated for. At 70 psi your running more fuel. After 70 psi there is a signifcant diminishing return in flow flow. Really the only reason to have that high of a pressure is if you are boosting and trying to make up for the increased manifold pressure.


BC

2Lucky2tha7

iTrader: (3)

????
Injector flow rate is measured at 43.5 psi. Check with ANY professional injector cleaning service place (RC Engineering, Witchunter performance, KGParts, etc. My injector flow graph will even tell you that.)
Where did you get 60 from??
Higher fuel pressure creates better atomization of the fuel when it is being injected.
Also, my tuning so far with it set at 50 psi has been better than ever, and has been easy to tune.

2Lucky2tha7

iTrader: (3)

I do agree however that my 550/680 is excessive though, but they work great, so I'm not worried about that.
I'm still debating on the nitrous, however. 1 of the reasons why I'm using these size injectors.

anewconvert

iTrader: (1)

I could be wrong, but I was under the impression it was measured at 60 psi.


In any case, the question still begs to be asked why you are running such large injectors on an NA. Smaller injectors allow for finer tuning of fuel. Basically if you if you have enough fuel injector then the smaller the better. its just because you can increase fuel in smaller increments per given increase in pulsewidth. With larger injectors any increase in pulsewidth results in a greater increase in fuel than with smaller injectors.


i think the question you need to answer first before anyone can answer the fuel pressure question is why you have gone with larger injectors. if its just because you have them sitting around and you dont want to spend the money to get 460's I can understand that, but it just seems, to me, that you will be making tuning more diffcult for you.

If you plan on running a large dry shot then the question is answered.


BC

2Lucky2tha7

iTrader: (3)

You are absolutely right. Originally, I was running a 460/ 550 combo with the stock TII fuel rail, but my duty cycles were all over the place. So, considering I already had a pair of cleaned and flowed 680's and I recently acquired another pair of cleaned and flowed 550's for free (well, actually in exchange for helping my friend with his MS install), I decided, why not just install them and retune my already goofy fuel map? Yes, they are definitely more than enough, and by 7800 rpms, I'm only getting 50 - 57% duty cycle all around, but so far my car has driven the best it ever has with my 4-port setup, let alone since I owned the car with my old ported 6-port.

anewconvert

iTrader: (1)

Ok, in that case I can see why you went that route. im not trying to **** in your wheaties here, just wondering abotu the rationale behind your choices. There are SOOO many posts in the 2nd gen forum about switching to a TII pump and 550cc injectors for an NA becuase it "doesnt get enough fuel" with the 460cc's that I have to ask when I see something like this.


As for the fuel pressure, I have already demonstrated I am not a reliable source on that. Good luck finding the answer.


BC

2Lucky2tha7

iTrader: (3)

I appreciate that