What fuel pressure to run with 800cc's

[racersedge1821]

My question is,i'm running a HX40 with 800cc injectors,a walbro 255 and a fuel pressure regulator what should i set my fuel pressure to?

 

[c2ypt1c]

Stock (around 43 psi). Although, you can raise it up to increase flow, you need to keep an eye on your IDC. You should be more concerned with how much air you'll be moving. If you want to maximize your setup, definitely look to upgrade those injectors and adding another pump...

 

[racersedge1821]

Would 50 psi. be suitable? I'm thinking about getting another pump but an Aeromotive inline pump. Would that work to help feed that hx40? It's only running 20psi now but i'm considering running 25

 

[kasumax]

I tried i quick search for a 1g. 2g is 43. i thought 1 g was 47-ish.

The 255 and FPR set at the proper fuel pressure will be just fine i have read. Will need to figure out if your injectors will keep up. May want search on the forums and see how much you can run. Or purchase a tuning solution to control it all.

 

[curt-s]

On a 1G, it's lower. 37psi with no vacuum line attached to FPR is the base fuel pressure. Of course, that's assuming stock fuel map and injectors.. you'd need to pick a pressure that's suitable for that exact set of injectors and feed/return line combination and compensate for it in tuning.

What type of injectors exactly? What is your feed line size?

 

[c2ypt1c]

On a 1G, it's lower. 37psi with no vacuum line attached to FPR is the base fuel pressure.

Yup, I forgot about the 1g's (no offense 1g owners!)

 

[racersedge1821]

My car is a 97 gst but it has a forged 6bolt swapped with speed density,and V3 Link but my cable was stolen,the car was tuned at 20 psi and the injectors are RC 800's. Since i have a 6bolt swap do i use the 1g fuel pressure or the 2g? Running 6 AN

 

[bigbird94]

My car is a 97 gst but it has a forged 6bolt swapped with speed density,and V3 Link but my cable was stolen,the car was tuned at 20 psi and the injectors are RC 800's. Since i have a 6bolt swap do i use the 1g fuel pressure or the 2g? Running 6 AN

I would reccomend you list all of your mods in your profile so that we can see exactly what you are working with.

 

[c2ypt1c]

My car is a 97 gst but it has a forged 6bolt swapped with speed density,and V3 Link but my cable was stolen,the car was tuned at 20 psi and the injectors are RC 800's. Since i have a 6bolt swap do i use the 1g fuel pressure or the 2g? Running 6 AN

I would run 43 psi. But seeing that you can't log with link, I would not turn the boost up. Hell, I wouldn't even go wot. For all you know the car was tuned at a higher fuel pressure. Do you even have a wideband? Any tuned logs from before it was stolen?

The first thing you should worry about is getting another cable.
USB datalogging cables (ECMLink V3 ONLY)

 

[WES_393]

More pressure will make the injectors flow more, but will cause the fuel pump to flow less. So unless your running out of injector and have more than enough fuel pump, leave it stock.

Also is your Walbro rewired? Is it the HP version? A non-rewired 255 non-hp will only support 50 lbs/min at 25psi, which isn't enough to safely support an HX40. A rewire would greatly improve fuel flow, but your 800cc (I assume you mean 850cc) are also cutting it close for what the HX40 can dish out. Even in a bolt-on housing.

 

[okm12346]

The base fuel pressure for 2g is 43psi with the line disconnected or crimped. For 1g turbo is 37psi and 1g non turbo and 2g non turbo spyder is 47-48psi. When you restore the vacuum it pulls it down a few psi.

You have to look at the injector duty cycle. Its its close to 100% at the desired boost and you dont want to upgrade the injectors, you can raise the Base fuel pressure a few psi to lower the duty cycle, or turn down the boost.

 

[Bud92gsx]

1g auto fuel pressure is 43 psi..1g 5 speed pressure is 37 ish.

You will want the pressure that the manufacturer says there rated to flow x amount of cc's..You can always increase the pressure and make the injectors flow more.

 

[MY1GDSM]

Just to clarify,
1g 5spd cars are 37psi, 1g Auto's are 43, 1g N/t cars are 47 and all 2g's are 43 as far as turbo cars are concerned.

As well the OP's question is very subjective need a lot more info to really say exactly what it should be. But a good starting point is always going to be 43 Psi without vacuum applied. As that is what the car came running and the majority of Injectors are tested at. As well and as mentioned if you start raising your base pressure the Pump will start to drop off in flow depending on the model. It's important to size and pick your fuel system parts based of what the cars power goal and taking into consideration ALL the factors involved including giving your self some head room for any unforeseen conditions.

 

[racersedge1821]

So i need to set my afpr to 43 and take off the vacuum line. Correct?

 

[n0de]

Are you running e85 or pump gas?

 

[91tsi_awd]

So i need to set my afpr to 43 and take off the vacuum line. Correct?

Take off the vacuum line, set it to 43psi then put the vacuum line back on.

 

[racersedge1821]

Running pump gas 93

Do you think i should turn it up some? Considering i'm running a HX40 with just 800cc injectors at 20 psi? If so probably 50 psi or so?

 

[91tsi_awd]

Running pump gas 93

Do you think i should turn it up some? Considering i'm running a HX40 with just 800cc injectors at 20 psi? If so probably 50 psi or so?

No, the fpr automatically raises fuel pressure under boost at a 1:1 ratio. Just make sure your fpr is functioning correctly, At full boost your fuel pressure should be at 63psi. Also make sure your idc isn't above 80% at 20psi, otherwise you need to go for some bigger injectors.