Starting point for +20 Inj

[GLHS99]

I'm running a T3/T4 Hybrid 46 Trim with Stage II wheel and a 0.63 housing with a 2.5" swingvalve and a 3" exhaust. I'm been loafing around until the clutch gets some miles on it. What's a good starting point for the base fuel pressure w/+20's (vacuum line unplugged)? I have it set at 38 #snow but I'm thinking it may be rich. This turbo spools much slower than the stock TII.

[crazy1eye]

I was just doing some "testing" with gaboon(Joey), he has the same setup + a large FMIC, 44pph 5th injector, etc... The base psi with the vacuum connected was at 46, using a digital volt meter tapped into the O2, it was reading .88 at WOT with 15/16psi. When he increased the boost to 19/20psi, we heard that nasty noise called detonation, not to mention the O2 readings dropped to .84 . With this setup, the boost was getting up to 10psi or so at 4000rpm, then hitting full boost by 4500rpm, kinda slow. Tomorrow, will try my 550cc(52pph) injector in stead of the 44pph, we don't want to increase the base fuel psi to much. This is where a custom cal would help, with a custom cal you could lean out the fuel & increase the timing to help with turbo spool, then remove the timing & add the fuel as the boost rises.

[glhsken]

WAY TOO LOW!!!

I maxed +20's out at 55 base and 18 psi with a stock turbo/Ic.

Ask GLHS222.... his base was there... I think he lost a piston or 2 (he has a 46 trim as well.)

[GLHS99]

I didn't actually run the car at that setting. I thought this turbo needed a little less fuel to spool up. In addition I thought to get the bigger injectors to idle you had to turn down the base pressure. For example if running 45 psi the +20's flow like 38pph compared to stock TII injectors at 55 psi flowing 33pph?

[GLHS99]

This thread was supposed to be a continuation of the other thread "Starting point for +20's" THis will make it easier. Who's running +20's w/T3/T4 Hybrid (46 trim stage II 0.63 exhaust housing and 3" exhaust) and what is your base fuel pressure set at? Thanks.

[glhsken]

Quote:

Originally posted by GLHS99 I didn't actually run the car at that setting. I thought this turbo needed a little less fuel to spool up. In addition I thought to get the bigger injectors to idle you had to turn down the base pressure. For example if running 45 psi the +20's flow like 38pph compared to stock TII injectors at 55 psi flowing 33pph?

Get used to the hybrid.. It's slower to spool until 4k with a 2.2. It doesn't mean it does not put "usable" power down as opposed to the stock turbo which hits so hard, the tires liqueify. Quite the opposite.. You will run quicker with it. 10 psi on a hybrid is equal to 14 on a stocker.

Yes, the idea is to lower the fuel pressure for idle. But if the injectors can't handle it up top, you'll have ashtrays. The stock LM will not like +20's @55 psi static (unplugged). The Stage II will handle them just fine. I ran like that for over a year.

The most boost you'll be able to handle with the +20's and Hybrid turbo is 16-18 psi. Even at 55 psi static. I've run just about every injector combo and fuel pressure short of 5th injectors and a rising rate. I wouldn't run a hybrid with +20's personally. If you do, a little rich down low is good insurance. ( I maxxed them out at around 270 hp to the wheels)

The only way you'll have "perfect" fuel for idle is to turn the base pressure below where they will handle the boost you seem to want. Best alternative is +40's and a custom cal or RRG reg (tough and touchy to tune)

[GLHS99]

That makes sense. I didn't plan on keeping the +20's as the new motor I'm building will have even greater fuel demands. I used them with the stock turbo and they were already on the car. Until I get to the track I have no frame of reference on my improvements. The characteristics of this combo is so different. I'm used to the tires breaking loose all over the place. The custom cal is starting to look like the way to go. I want something I can set and forget. Thanks for the response.

[87Shadow]

Ok so the base fuel setting at static 55PSI should be good for about 18PSI? I looked up and the formula which I found was:
P = 55 * (Desired LBS^2 / Actual LBS^2)
Where P is the base pressure.
The big question is.....
If the 42LBS injectors are rated at 55PSI base, how low of a base can you go before the injectors stops spraying correctly? I can't phrase it correctly, but @ 55PSI they spray as they are designed to, how low of a base can you go before it doesn't function properly? Or does it have a limit?
A side question, what happens if you have a HIGHER then rated base pressure? ie 42LBS injectors at a base of 60PSI.
Peace

[87Shadow]

I think I killed this thread.

[GLHS99]

I think you can turn them down quite a bit before it has an impact. I think Gus mentioned something about this on his site. The people that run +40's turn them down fairly low with a Rising Rate of Gain Regulator to get the car to idle. Last night I took the car out for evaluation and Ken was right. The base pressure was too low. I ran out of fuel before 15 lbs of boost. I turned it up to 45 psi and I'm carefully testing it. I'm probably going to have to turn on the 5th injector for the time being until I can get the funds to go to a Relentless Cal with +40's. I have a week to prep for Test and Tune at ESTA in Syracuse (6/28). Time to put on my wounded duck face to hand out some "Humble pie".

[glhsken]

Set the base to 55 for now. The stage II cal can handle it no sweat at idle with an good flowing exhaust (I ran like that for over a year). With the hybrid, that will give you fuel for 16-18 psi. Set the 5th to come on at 14-15 psi for safety

Too many people are giving bad fuel advice on this board. The base pressures people are setting their injectors at is ridiculous. And they all want to argue until they lose a piston.

Gus had his +40's set at 18-20 psi base... no effect on the spray pattern car idled and passed emissions this way. He also had the RRg reg for higher boost. I had my +40's set at 28 base, There was enough fuel with the hybrid turbo for 17 psi of boost.

[87Shadow]

Ken,
That's great for 40+ injectors at a static of XX PSI base pressure, but in my engine (mild ported head/match ported intake/exhaust) if I leave it at a base 42LBS@55 PSI, it will be WAY to rich and kill the O2. I know I've lost 2 O2's now. I ran at 40PSI base, and it had more then enough fuel for 16PSI but I haven't gone higher. I turned it down to a base of 31 base PSI and that's WAY to low, but I'm wondering if this is because of the spray pattern of the injectors. There is no RRR just a AFPR, so this limits me as I have to reach a balance. I think I'm going to call the injector manufacture and find out if these injectors have a limit which affects their spray pattern. What is the IDEAL EGT?
Peace

[glhsken]

31 base with +20's will affect the car because of 2 little fuel at idle... literally starve it.

I've never run into a spray pattern issue. This was debated long ago on the FMML.

Stock LM's will not handle 55 psi base The GLHS MP (stage II) will. Not sure about the Daytona/shadow unit.

Ideal egt is 13-1500 for cruising.. 15-1550 max wot and 850-1000 idle.


I wouldn't go over the boost you have set with only 40 psi base pressure.. not a lot of room there.

[GLHS99]

The first thing I'm doing when I get home from work, well the second thing, after I get a beer, is to set the base pressure to 55 psi.

[GLHS#116]

Here's the deal, folks. Listen to Ken. He KNOWS stuff! The stock pressure reg is 1:1. If you put in +40s and then turn down the base pressure to where you have the flow of stockers at idle YOU WILL HAVE THE FLOW OF STOCKERS AT HIGH BOOST AS WELL!!! You should, in fact, have a fuel curve that is more or less identical across the board to stock.

Let me put this a different way. There's always (<base pressure>+boost[or -vacuum]) force pushing the fuel out into the air stream at the intake port. That's the job of the fuel pressure regulator. The way your engine gets more fuel at higher boost and less at vacuum is that your computer varies the duty cycle (the amount of time the injector spends open vs. closed) according to the engine's needs. At idle the injectors are closed most of the time. At high boost they can be open up to 80% of the time. When you raise the boost past what the engine knows about (past 14psi without a custom cal and 3bar MAP) you get no extra fuel. If you are already too rich at 14psi because of a high base pressure (like Ken) you can go and boost a little higher before you are too lean. At part throttle you won't be too rich on the GLHS Stage II because it uses feedback from the O2 and has fairly wide tollerance for adjusting the duty cycle (fuel curve) based on that. O2 is ignored at WOT and cold engine conditions, BTW. The stock computer only adjusts via O2 in a narrower band and will stay rich everywhere.

The only way to have your mixture OK at high boost and low boost is to take over from the computer once it turns blind past 14psi (RRR or 5th and 6th injectors). The obvious turnkey alternative to this is a custom cal. Combined with a 3bar MAP your computer is now able to see and understand boost levels up to 30psi.

You don't want to get this wrong. High boost and lean mixture is a quick route to an expensive rebuild.