Direct port on my twin turbo some questions about fuel pressure and jets.
05-07-2009, 11:06 PM
#1
Direct port on my twin turbo some questions about fuel pressure and jets. Ok have the zex direct port lsx kit going on my car. I have as you can see 408 twin turbo setup. I recently got a new fuel system with boost referenced regulator.
So now not really clear. When my car is in boost and the nitrous is happening too then the fuel pressure can go up 1 to 1 with the boost. So say running 50 base would be getting 70 fuel pressure at 20psi.
So what effect does this have on the nitrous system. Does it mean a 100 shot is not a hundred shot when the car is at 20psi and fuel pressure has gone 20 over normal. Does this affect my fuel or nitrous jetting to get a given power level or do I risk going lean or super rich if don't change out the jets to compensate for the increase in fuel pressure that happens under boost?
Can someone clarify this stuff for me.
So now not really clear. When my car is in boost and the nitrous is happening too then the fuel pressure can go up 1 to 1 with the boost. So say running 50 base would be getting 70 fuel pressure at 20psi.
So what effect does this have on the nitrous system. Does it mean a 100 shot is not a hundred shot when the car is at 20psi and fuel pressure has gone 20 over normal. Does this affect my fuel or nitrous jetting to get a given power level or do I risk going lean or super rich if don't change out the jets to compensate for the increase in fuel pressure that happens under boost?
Can someone clarify this stuff for me.
05-07-2009, 11:13 PM
#2
The fuel pressure increase will have an effect on the nitrous tune. It may be best to go with a dedicated cell for the nitrous with a set regulator to keep the nitrous tune in check. Also, you will want to run the DP on a low pressure setup. When you are on a high pressure setup running a low shot, the jets are tiny. Huge chance of clogging one. It also depends at what point you are spraying, and how long it takes the car to come on full boost.
05-07-2009, 11:22 PM
#3
I don't think going to bother with extra tank and separate pump and reg.
Lonnie was explaining to me what you said.That the jets got tiny when you go to small shots at higher pressures. So that was one reason got 120s to be able to run lower pressure and still have lot of headroom. So at lower pressure then can use bigger jets to get similar power as smaller jets at higher psi.
Wonder how i figure out what jet sizes to run and how so what effect does it have as fuel pressure will rise with boost.
I have seen many turbo cars mostly dsms like my talons running with direct port and turbos one fuel tank,one reg no problems running small shots usually and no problems apparently.
I guess big danger is getting something in fuel jet so a good filter is obviously important.
Maybe should put an extra filter on the nitrous fuel feed but small filter on that smaller 4 an line would likely have more chance of clogging up than current running on big filter on the 8 an main fuel feed. ?
So will zex be able to tell me what up at different pressures so can size the jets.
I can run less boost and bigger shots also.
Would think that is also an option. So 10psi instead of 20psi and then a 200 shot type of thing.Engine is fully forged up so don't see a problem on that end of it.
Lonnie was explaining to me what you said.That the jets got tiny when you go to small shots at higher pressures. So that was one reason got 120s to be able to run lower pressure and still have lot of headroom. So at lower pressure then can use bigger jets to get similar power as smaller jets at higher psi.
Wonder how i figure out what jet sizes to run and how so what effect does it have as fuel pressure will rise with boost.
I have seen many turbo cars mostly dsms like my talons running with direct port and turbos one fuel tank,one reg no problems running small shots usually and no problems apparently.
I guess big danger is getting something in fuel jet so a good filter is obviously important.
Maybe should put an extra filter on the nitrous fuel feed but small filter on that smaller 4 an line would likely have more chance of clogging up than current running on big filter on the 8 an main fuel feed. ?
So will zex be able to tell me what up at different pressures so can size the jets.
I can run less boost and bigger shots also.
Would think that is also an option. So 10psi instead of 20psi and then a 200 shot type of thing.Engine is fully forged up so don't see a problem on that end of it.
05-07-2009, 11:29 PM
#4
When are you looking to spray? If you only want to spray when the car is in full boost, that's easy. Get a window switch and set it to a couple hundred RPM after you hit full boost. Then set your jetting for how much fuel pressure you run at full boost. With the twins, I wouldn't expect much lag, and you are probably in full boost by 3K-which is when most people start to spray.
05-08-2009, 05:31 PM
#5
Truck Sponsor
iTrader: (11)
Join Date: Sep 2006
Location: Wichita Falls Tx.
Posts: 3,122
Likes: 0
Received 0 Likes
on
0 Posts
Your fuel pressure raises 1 to 1, its an offset. If you start with 50psi jetting, and you run 20psi of boost but now your fuel pressure is 70. Really you are still spraying 50psi worth of fuel at the nozzle. The air pressure will offset the fuel pressure this is why you need a 1 to 1 compensating regualtor. Failure to do so will mean you will only be spraying 30psi at the nozzle and be very lean.