Plan on running big shot----few questions

[i30dvr]

Ok right now im running the nx wet kit with a 75 shot jet. I like it a lot but would like to go higher. I was planning on getting the walbro 255 fuel pump and adjustable fpr. My question is what my fuel pressure should be for running a 100+ shot and how i would adjust it so i know the first time i spray a higher shot i won't blow it up. any input would be greatly appreciated. Thanks guys

[mtrai760]

Stock fuel pressure. With Nitrous Express, you adjust the size of the fuel nozzle, not your fuel pressure. Dry kits must adjust the fuel pressure. That is a benifit of the wet kit, keeps your fuel pressure at a safe level.

Nitrous Express or members here should be able to recommend a fuel jet size for your 100 shot. You will need to check your AFR's and your plugs and adjust from there. From what I have seen from Nitrous Express, they are usually pretty close.

[grey99max]

Originally Posted by mtrai760

Stock fuel pressure. With Nitrous Express, you adjust the size of the fuel nozzle, not your fuel pressure. Dry kits must adjust the fuel pressure. That is a benifit of the wet kit, keeps your fuel pressure at a safe level.

Nitrous Express or members here should be able to recommend a fuel jet size for your 100 shot. You will need to check your AFR's and your plugs and adjust from there. From what I have seen from Nitrous Express, they are usually pretty close.

^ ^ ^ what he said.... update your plugs, use race gas for safety, a 300ZXTT fuel filter for the volume, a change of underwear, and 100-shot jets - call NX and ask..... jet sizes depend on the hot bottle pressure and what your fuel pressure is set to - you do have gauges for both, right? NX expects 43 psi for most imports..

EDIT 7:15 PM. I just looked up the old Jime-recommended 100-shot jets and they are N2O=52 Fuel=31 ...

.

[t6378tp]

I am running a 100shot
bottle psi is set to 1050
nitrous jet 46
fuel jet 26
a/f was 12.5-12.8 while on the dyno

but everycar is alittle different

[i30dvr]

Originally Posted by grey99max

^ ^ ^ what he said.... update your plugs, use race gas for safety, a 300ZXTT fuel filter for the volume, a change of underwear, and 100-shot jets - call NX and ask..... jet sizes depend on the hot bottle pressure and what your fuel pressure is set to - you do have gauges for both, right? NX expects 43 psi for most imports..

EDIT 7:15 PM. I just looked up the old Jime-recommended 100-shot jets and they are N2O=52 Fuel=31 ...

.

the only gauges i have are wideband and nitrous bottle pressure....now i don't need to upgrade the fuel pump?

[mtrai760]

Yes you do need to upgrade the fuel pump. The stock pump was not designed to flow enough fuel for your requirements.

[Max_Out]

Originally Posted by mtrai760

Stock fuel pressure. With Nitrous Express, you adjust the size of the fuel nozzle, not your fuel pressure. Dry kits must adjust the fuel pressure. That is a benifit of the wet kit, keeps your fuel pressure at a safe level.

Originally Posted by mtrai760

Yes you do need to upgrade the fuel pump. The stock pump was not designed to flow enough fuel for your requirements.

Now I'm confused. Id upgrade regardless. Never know when you might go F/I.

[mtrai760]

Fuel pressure and fuel flow are two different things.

[Max_Out]

Originally Posted by mtrai760

Fuel pressure and fuel flow are two different things.

so your saying that can regulate the stock fuel pump? interesting. any links on this, im interested.

[Lusitania]

Isn't fuel pressure and fuel flow directly proportional. If you increase one, the other must as well. Any engineer knows that ρ a v = ρ a v. ρ = density a = area of opening v = velocity. It is safe to say that we can replace v with fuel flow, and ρ with pressure since in this case density and pressure are proportional. If we keep a (area, the opening) the same, for both sides, and increase pressure, the velocity must also increase. If you increase pressure, then velocity must also increase. Dunno if this helps clarify anything for anyone, but hope it does.

[grey99max]

Originally Posted by mtrai760

Yes you do need to upgrade the fuel pump. The stock pump was not designed to flow enough fuel for your requirements.

I did use a 100-shot NX setup for a while, maybe three years ago - and the engine lived - and the fuel pump was stock. I only had colder plugs, so no idea what the A/F was...

[grey99max]

Originally Posted by Lusitania

Isn't fuel pressure and fuel flow directly proportional. If you increase one, the other must as well. Any engineer knows that ρ a v = ρ a v. ρ = density a = area of opening v = velocity. It is safe to say that we can replace v with fuel flow, and ρ with pressure since in this case density and pressure are proportional. If we keep a (area, the opening) the same, for both sides, and increase pressure, the velocity must also increase. If you increase pressure, then velocity must also increase. Dunno if this helps clarify anything for anyone, but hope it does.

?? Er.... we don't especially worry about velocity. Fuel pressure and fuel flow volume are inter-related, since the pump establishes the pressure, which is managed with a FPR (regulator) to keep the pressure constant. Only when fuel consumption volume goes too high for the pump to maintain pressure is there a problem. If you are using more fuel with nitrous or FI or larger injectors for NA, then a larger pump can be required. Higher horsepower always demands more fuel, so changing out the fuel pump, regulator, and filter is quite common with higher horsepower engines. Pressure under full load must be maintained - monitor this with a fuel-pressure gauge.

[mtrai760]

Originally Posted by Max_Out

so your saying that can regulate the stock fuel pump? interesting. any links on this, im interested.

I was saying that the stock pump is going to be hard pressed to provide enough fuel volume to maintain proper fuel pressure at the requirements of a 100 shot of nitrous. 255lph pumps are cheap, $85 is better than a $500 motor and the time to replace it.

[mtrai760]

Originally Posted by Lusitania

Isn't fuel pressure and fuel flow directly proportional. If you increase one, the other must as well. Any engineer knows that ρ a v = ρ a v. ρ = density a = area of opening v = velocity. It is safe to say that we can replace v with fuel flow, and ρ with pressure since in this case density and pressure are proportional. If we keep a (area, the opening) the same, for both sides, and increase pressure, the velocity must also increase. If you increase pressure, then velocity must also increase. Dunno if this helps clarify anything for anyone, but hope it does.

They are directly related, but they are not the same thing is all I was saying. grey99max pretty well summed it up. Basically, the stock fuel pump is barely adequate for a 50 shot, it does not have the flow capability to sustain a 100 shot, IMO. Without the flow, you cannot maintain the proper system pressure, which means you run lean, and buy a new motor.

[t6378tp]

when once I ran a 85shot and confirmed with a incabin fuel psi gauge that the stock pump was not able to maintain psi at high rpms

when I would 1st hit the nitrous psi would go up to 50psi then slowly taper off so I got a 255 and never had that problem again

[i30dvr]

which 255 pump would you go with? cheapest place to get it from?

[accordingtou]

Originally Posted by i30dvr

which 255 pump would you go with? cheapest place to get it from?

For a piece of mind....I have the hp high pressure pump part#GSS342 hp
Walbro Fuel Pumps & Install Kits 89-94 Maxima 190LPH, 255LPH, 255LPH-HP Free Shipping

[sparks03max]

There's alot of misunderstanding about why you need a bigger fuel pump in this thread.

Consider it this way. The stock pump can easily keep the pressure needed to run the engine stock. The way a wet shot of nitrous works, it pulls fuel from the fuel line that goes to your injectors and puts it into the intake.

The fuel pump must STILL keep up pressure while supplying both the injectors AND the nitrous fuel solenoid. A bigger pump can push the extra fuel, the stock pump won't be able to keep up with the increased total fuel requirements.

[vwracer1172]

how does the bottom end hold up with a 100 shot also head gaskets?

[i30dvr]

umm well so far so good..compression is still perfect but the only thing is that i have my nitrous stop at 6000rpm before the trans shifts as to not add that much more stress on it but after it shifts into second gear the afr spikes to like 16.0+. Could this be contributed to the fuel pressure? if i let out of it and get back in it it will go back down to normal...(12.0-12.4)

[i30dvr]

any idea guys? i think even though the nitrous should come back one under 6k rpm it doesn't. Only if i let off the gas completely then it will spray again....

[grey99max]

Originally Posted by i30dvr

any idea guys? i think even though the nitrous should come back one under 6k rpm it doesn't. Only if i let off the gas completely then it will spray again....

It would help if you described your full installation for nitrous, and how you are shifting and cutting the nitrous before shift.

I use the MSD 8969 RPM switch for several things, and when you wire it as a nitrous window, it always triggers just at the ON rpm, and has to drop 200 rpms below that to turn OFF. If you go up beyond the window for cutoff, it cuts off at the set Off rpms and has to drop 200 rpms below that to come back on.

[i30dvr]

well i also have the 8969 set to come on at 1500 and cut off at 6k. my only reason as to y it goes lean is the fuel pressure because i have stock fuel pump still. It seems like once i let off completely and get back into it the a/f will be back down around 12.0 or so.

[grey99max]

Originally Posted by i30dvr

well i also have the 8969 set to come on at 1500 and cut off at 6k. my only reason as to y it goes lean is the fuel pressure because i have stock fuel pump still. It seems like once i let off completely and get back into it the a/f will be back down around 12.0 or so.

Sounds like you either ran out of fuel pressure -when you let off, it came back up - or you didn't have enough fuel in the tank and you ran low on fuel pressure.

I won't run hard with any less than 1/8 tank - and I prefer going to the track now with 1/2 tank. Spraying a heavy shot really sucks fuel, you know. I have two PLX graphs showing my A/F going very lean in third gear at 150-shot - 1/8 tank wasn't enough - I was sucking air as I got close to the traps.

[i30dvr]

Originally Posted by grey99max

Sounds like you either ran out of fuel pressure -when you let off, it came back up - or you didn't have enough fuel in the tank and you ran low on fuel pressure.

I won't run hard with any less than 1/8 tank - and I prefer going to the track now with 1/2 tank. Spraying a heavy shot really sucks fuel, you know. I have two PLX graphs showing my A/F going very lean in third gear at 150-shot - 1/8 tank wasn't enough - I was sucking air as I got close to the traps.

yea it really doesn't matter where the fuel is at in the tank. i've never really sprayed under 1/4 tank just for safety.

[i30dvr]

Originally Posted by grey99max

Sounds like you either ran out of fuel pressure -when you let off, it came back up - or you didn't have enough fuel in the tank and you ran low on fuel pressure.

I won't run hard with any less than 1/8 tank - and I prefer going to the track now with 1/2 tank. Spraying a heavy shot really sucks fuel, you know. I have two PLX graphs showing my A/F going very lean in third gear at 150-shot - 1/8 tank wasn't enough - I was sucking air as I got close to the traps.

grey- where do u get ur racing fuel? i want to get like 5 gallons of 100 octane or so to be safe on a 100+ shot...i live in VA and really don't know of any places to get it.

[grey99max]

Originally Posted by i30dvr

grey- where do u get ur racing fuel? i want to get like 5 gallons of 100 octane or so to be safe on a 100+ shot...i live in VA and really don't know of any places to get it.

I used Sunoco 104 unleaded, which you can get at most drag strips in the Midwest. You can also order it in cans from a place in Texas. -Google for it. This year, since I'm pushing up to 175-shot now, I switched to VP Racing Motorsport 109 - also unleaded. They have a good web site.

Look in your phone book - under Speed Shop or Performance Cars or the like. If a shop sells it, chances are their ad will say so. If you have any roundy-roundy tracks local to you, check with them - they usually sell the stuff...

Use Google to search for outlets. It's out there.

[i30dvr]

ok cool thanks man

[i30dvr]

ok i've been looking in the GD section and there is only like 89-94 maxima walboro pumps. will these fit or does anyone have a link to get one for a 99?

[accordingtou]

Originally Posted by i30dvr

ok i've been looking in the GD section and there is only like 89-94 maxima walboro pumps. will these fit or does anyone have a link to get one for a 99?

Originally Posted by accordingtou

For a piece of mind....I have the hp high pressure pump part#GSS342 hp
Walbro Fuel Pumps & Install Kits 89-94 Maxima 190LPH, 255LPH, 255LPH-HP Free Shipping

The fuel pump fits my 4thgen max...
Click on link please
http://forums.maxima.org/6754632-post45.html

[grey99max]

Originally Posted by i30dvr

ok i've been looking in the GD section and there is only like 89-94 maxima walboro pumps. will these fit or does anyone have a link to get one for a 99?

A Walbro GSS342 HP works fine in my '99, and yes, the '94 pump is the same dimensions and connections as the '99. The full installation kit for the '94 doesn't have the right parts for 95-99 tanks - but the pump is right.

[i30dvr]

ok cool thanks guys, where abouts is a good place for a '99 install kit?

[grey99max]

Originally Posted by i30dvr

ok cool thanks guys, where abouts is a good place for a '99 install kit?

Don't need one - the Walbro pumps fit exactly into the '99 tank to replace the original pump. I did it, anyway....

[i30dvr]

sweet.

[i30dvr]

ok guys i'm about to order the 255hp pump and was wondering what afpr you guys are running....do you all have setup pics of them? i need help cause i think my fuel pump is on the way out. today i was driving my car and when i come to a stop after about 10-15 seconds the idle drops to around 700rpm or so and sounds like it has really big duration cams or one of the coil packs is unplugged and running on 5 cylinders....i check those and there all secure. so what is everyone think? any pics of the afpr?

[accordingtou]

I thought I saw your nitrous kit for sale

[t6378tp]

I have a aeromotive, check my cardomain for pic's

I have pic's of a kirban and aero both on there, the kirban sucks azz and would blow the diaphram everytime I sprayed it but the company did replace it 3 times with a brand new one.

[grey99max]

Originally Posted by i30dvr

ok guys i'm about to order the 255hp pump and was wondering what afpr you guys are running....do you all have setup pics of them? i need help cause i think my fuel pump is on the way out. today i was driving my car and when i come to a stop after about 10-15 seconds the idle drops to around 700rpm or so and sounds like it has really big duration cams or one of the coil packs is unplugged and running on 5 cylinders....i check those and there all secure. so what is everyone think? any pics of the afpr?

My Aero ****105 EFI regulator. Diaphram rebuild kits are available. Old pix - I now run 45 psi on the 3.5.

[i30dvr]

Originally Posted by accordingtou

I thought I saw your nitrous kit for sale

aha yea it is for the right price, but it seems like no one wants it lol.....i still need to get the pump though even though i might be getting rid of it.

[i30dvr]

Originally Posted by grey99max

Don't need one - the Walbro pumps fit exactly into the '99 tank to replace the original pump. I did it, anyway....

ok im ordering mine right now and the guy from importcar gd for the fuel pumps said i have to modify it? it should be the same shouldn't it?