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View Full Version : sr20det upping fuel pressure


joe3180
07-03-2013, 04:12 PM
I was wondering if there is any down side to increasing the fuel pressure to 4bar(59psi)?

As far as fuel goes I am running a walbro 255 fuel pump, 555 injectors, and will be getting a aeromotive fpr. The reason I want to do this is I am getting close to the max duty for my current injectors at just under 350hp and I wont be able to get new top feed injectors/rail for a few more months and doing this should keep me safe until I can upgrade the injectors.

If something I said is wrong let me know. As far as I know, all the information is right but I in no way know everything and am happy to learn if I am wrong.

EsChassisLove
07-03-2013, 04:40 PM
I think the only problem is going to be the size of your feed and return lines. A lot of pressure going through the lines.

joe3180
07-03-2013, 06:49 PM
Ok. I didn't think about that. I will have to look into that. Thanks.

EsChassisLove
07-04-2013, 12:23 PM
I can't remember what size lines are stock. -4 I think. Some steel braided -6 and a CS fuel rail would be a perfect set up for a 4 bar system.

I'm sure someone will chime in and say stock is fine. Lol

joe3180
07-04-2013, 01:53 PM
Ill think about the cs. I tend to go away from that brand except in parts that are not critical. I was just going to buy a tomei adaptor or similar, -6 fittings, and ss lines from the hard line to the rail and back. I understand you are trying to get -6 fitting in and out and Ill ask my builder what they think about it as well. Im hoping they say it wouldn't be necc unless I was trying to flow even larger injectors but maybe it will be. Thanks again.

codyace
07-05-2013, 12:12 AM
I'd make sure he 555 injectors can hold up to the high pressure without issue. Not all injectors like 4 bar base fuel pressure.

AsleepAltima
07-05-2013, 12:29 AM
ive got plenty of -6 line if you want to make braided hoses - you just need to get the fittings. i do believe i have the correct tap as well if you want to buy a blank fuel rail and install the fittings onto it same as my car is done.

joe3180
07-05-2013, 12:35 AM
Ill check with hks about the injectors to be sure about the pressure. I hope they will be fine. But perhaps when I get them flow tested I can have them tested at 4bar. I never had injectors tested before so I don't know how the process works but if it can be done I will do it.

that would be great. I was going to start looking for some line sometime soon too. Ill be in touch and find a day you will be available. Thanks.

AsleepAltima
07-05-2013, 12:37 AM
Ill check with hks about the injectors to be sure about the pressure. I hope they will be fine. But perhaps when I get them flow tested I can have them tested at 4bar. I never had injectors tested before so I don't know how the process works but if it can be done I will do it.

that would be great. I was going to start looking for some line sometime soon too. Ill be in touch and find a day you will be available. Thanks.
no problem bro, just let me know!

Croustibat
07-05-2013, 03:21 AM
It is not worth it. Here is why.

1/added strain on the fuel system and wiring.

Your fuel pump has to be able to do base pressure + boost, and its flow crumbles when upping pressure. Now if you are doing 350HP, you are north of 1bar boost, meaning the pump needs to flow about the same(140L/H instead of 136L/H), but at 1 bar more pressure. It also means the injector drivers (in the ECU) will require more amps to open and close the injectors ( = heat )

2/ Injector flow is proportional to the square root of pressure. So if you add 1 bar, that is a 33% increase in pressure meaning IF your fuel pump can cope with that, you only get 5.7% increase in flow. So you go from 550 to 586cc ...

And it means you still have some crappy 20 yo injectors.

So ask yourself "is it worth it ?" That is a 5.7% flow increase. Not much considering the added stress to the whole system.

Been there, done that. Finally got bosch ev14 1000cc hi impedance injectors. Work wonders, has somewhat the same latency old 500cc injectors have so tunability is very good. And i now have room :D

joe3180
07-05-2013, 09:26 AM
Thanks for the input. I will look into that as well. The injectors are fairly new though. They are only about 4 years old and have 5k-7k miles on them. My car has been dead for the past few years.

Croustibat
07-05-2013, 10:15 AM
What i mean by "20year old injectors" is that this is previous century tech. Those injectors, while not bad, were designed a long time ago. Tech has made a lot of progress on this.

TBH i went from 4 different injector sets. The latest is the ev14 set, which replaced a set of 510cc mitsu evo ones (on a CA18DET engine but it does not matter here). EV14 are new tech. From mapping, I could see i have more torque everywhere, and a bit less fuel consumption, for the same base pressure. I guess the atomization is much better, and as the injectors are twice as big their opening time is halved, so less fuel is going to hit a closed intake valve (most fuel will just do that when your injector duty is high).
That cant be bad for combustion.

Anyway your choice here. Just saying upping fuel pressure will put a lot of strain on your fuel delivery system and wiring while only providing approx 5% more fuel delivery capacity.

Selling your injectors and getting EV14 based ones may cost the same or less than changing fuel rail and fuel lines, will provide room, and will increase overall efficiency. Injector dynamics sells these, so do fuel injector clinic, five-o motorsports, and i am quite sure many others.

Now i think you have enough info to make your choice :D


BTW whatever your choice is, you will need a remap.

joe3180
07-05-2013, 11:17 AM
Thanks again. I will check those out. Yes, I know I will need the remap. Its part of the reason I want to do this now. My engine will be out of the machine shop soon and will be dynotuned afterward so I want my whole plan in place so I don't think of something new after the tune and then have to go back again.

I understand what your saying about the injectors now. It didn't click the first time.

AsleepAltima
07-05-2013, 05:10 PM
What i mean by "20year old injectors" is that this is previous century tech. Those injectors, while not bad, were designed a long time ago. Tech has made a lot of progress on this.

TBH i went from 4 different injector sets. The latest is the ev14 set, which replaced a set of 510cc mitsu evo ones (on a CA18DET engine but it does not matter here). EV14 are new tech. From mapping, I could see i have more torque everywhere, and a bit less fuel consumption, for the same base pressure. I guess the atomization is much better, and as the injectors are twice as big their opening time is halved, so less fuel is going to hit a closed intake valve (most fuel will just do that when your injector duty is high).
That cant be bad for combustion.

Anyway your choice here. Just saying upping fuel pressure will put a lot of strain on your fuel delivery system and wiring while only providing approx 5% more fuel delivery capacity.

Selling your injectors and getting EV14 based ones may cost the same or less than changing fuel rail and fuel lines, will provide room, and will increase overall efficiency. Injector dynamics sells these, so do fuel injector clinic, five-o motorsports, and i am quite sure many others.

Now i think you have enough info to make your choice :D


BTW whatever your choice is, you will need a remap.you bring up some pretty excellent points... i think im going to get some new injectors when i get my jwt tune redone.