derelict

At what level is it dangerous/harmful? When I start the car in the morning it hovers around 29-30psi. Normal acceleration brings it up to 35-40, and WOT pegs it at 97+. However when I take my foot off the gas (after accelerating) to coast, I see it drop down to as low as 21psi sometimes. Stopping at a light after about 20 minutes of highway driving is showing 27-28psi. A/F is constantly between 14.4 and 15.2 while cruising, and goes immediately to 11.5ish under WOT at first, and then eventually under 11 (needle buried) if I keep on it. I still need to dyno tune with e-manage. Any recommendations about the low FP under those conditions or should I stop worrying?

Seattle Cl-S

Isn't anything under 12 (A:F) for long periods of time a bad thing for an engine?

Smitty

ur fuel pressure is too low.

I gave Steve all the numbers to give to you.

Smitty

and yeah under 12's is not good....

1 too many times = BOOM BOOM

Smitty

STOCK: 36psi and 70 w/ vacuum pulled~~~ STOCK



with HBP
35psi
65 vacuum pulled
Ignition key on car off ESM voltage should read 2.93 Volts.
NO Accessories are to be on (i.e. A/C. radio,etc)

the Richer you run = more power loss.
you run lean too many times and you will be replacing that motor again.

derelict

I was under the impression that low A/F = rich. Air to fuel... 12 parts air to 1 part fuel has more fuel in the mix than 17 parts air to 1 part fuel. No? Which is why when you take your foot off the gas, it goes to completely lean (higher than 17) for a sec since it's all air. Maybe I am very confused? I thought lean meant lean on fuel... not lean on air.

av6ent

Isn't this is a rule for FI cars to keep under 12s AFR at WOT to be safe?
My understading the AFR should be stoich 14.7 at idle and go from 13s partial throttle to high 11s at WOT for all FI cars. And by running more then 12.5 at WOT thats where it goes BOOM

johntypes

your setting a-f should be 13.1 nothing under that

scalbert

Wrong, 13.1:1 is way to lean for a supercharged J32A2. Knock will occur imediately. I tuned mine for 11.5:1 - 12.0:1 to play it safe. IMO, on pump gas 12.0:1 is about as lean as I would go.

The lower the number the richer it is:

14.7:1 is stoichiometric which is what the ECU shoots for during cruise and idle. But that is too lean for WOT. I believe Ramanan also shot for just below 12.0:1 as we found it to be the safest for pump gas.

scalbert

No, not at all. This only occurs during acceleration. The rest of the time the ECU will keep it near 14.7:1. Running under 12.0:1 with an SC is prefered. But not too low though. If you started hit mid 10's and below you may have a chance for a backfire in the exhaust. If not that it can start to damage the cat and the O2 sensors.

allmotor_2000

If you were running 10.5, you will notice a loss in power, but it won't harm the motor.... probably backfire and suck up a lot of gas. I would not recommend anyone running > 12.0 under boost on our motors on pump gas!

Personally I run anywhere from 11.0 to 12.0 depending on RPM and boost-level. It's very difficult to get a constant A/F at all times, but if you are within that range, you are ok.

johntypes

I forgot supercharger's
-------------------

derelict

Wanted to revisit this topic, especially since I am having other problems with boost lately. Lately I am noticing a "sluggishness" during WOT and I never see more than 3-4 psi (and only then momentarily). I don't think the gauge is busted because it's showing the proper -10psi vacuum at idle or when my foot is off the gas. Fuel pressure also starts out at 30 when I start the car in the morning -- then as I begin to drive it drops down to 25ish at idle. It does still spike up to 80-90ish on WOT, but never over 100 like it used to... maybe cuz I am not seeing as much boost anymore? So given that the gauge is reading the vacuum correctly, where could the loss in boost be coming from? A crack in my headers maybe? I checked the belt and it was tight so I am not sure it's slipping... although maybe the pulley itself is slipping if that's possible?

Also, the only time I get concerned about FP is after I drive the car home from work... and then about 3 hours later I get back in and start it up. FP shows at like *6* at idle. When I hit the gas it goes up to 30 and then eventually gets better the more I drive, back to the 25ish at idle/no accel and the normal 80-90 at WOT. But that first reading after I start up scares me.

Any ideas? thanks!

speedr73

Hmm...I have a boost gauge running stock right now on my 99TL, and I show around 20in vacuum during idle. Why are you running 10in? Not sure about that 6psi fuel pressure at startup. I hope that is just a glitch in the gauge at startup, maybe a wiring or electrical problem. (Electrical gauge right?)

I also wanted to revisit this issue as to the regulator. This is what I got out of reading the installation instructions from comptech on their regulator.
The ratio you set the regulator at will add pressure based on boost. If I have 6psi boost, and a 4:1 ratio on the regulator, the I will see an addition of 24 psi to the static pressure when full boost is reached, right?

Also, static pressure is not idle pressure. Static pressure is the pressure the regulator puts out when there is neither boost nor vacuum, right? Comptech says their regulator sees a .75psi drop per 1in of vacuum. So you have to figure your static pressure needs based on what pressure we need at idle.(under full vacuum~20in)

So, I figure I will need a 45psi static pressure setup for there to be 30psi under 20in of vacuum (idle). Then, at 5.8 psi of boost I have determined that I will need the regulator to be set at 8:1 for there to be a max of 91.4psi.

I wonder tho, can our stock injectors handle this? And if so is that a good fuel pressure to shoot for, or does it need to go higher or lower? Of course this is all theoretical for my car and setup until it is tuned and I see what the A/F ratios are.

P.S. I have a 255lph fuel pump that can handle the high pressures.

mrsteve

iTrader: (1)

The boost sender was loose and he was leaking vaccum/boost. Everything has been repaired and its running well

speedr73

So what about the rest of what I said...What peak fuel pressure should I be looking for?

mrsteve

iTrader: (1)

Depends on the tune of your e-manage. You should be able to add enough pulse width so that your fuel pressure doesn't need to go above 70-80 psi. I haven't installed the e-manage yet though but i'm just going off of what i've read.

bigguyonbike

your vacuum is too low. it should read 20 inHG at idle. 10 inHG means that you probably have a leak in one of your vacuum lines. double check to see if a line has popped off. that may be the reason why you only get 3 to 4 psi because most of the blower's air is escaping.

also 6psi of fuel pressure is too low and can cause a very lean condition because the ecu might possibly max out pulse width to reach 14.7 a/f during idling.

speedr73

Thanx, that answers what pressure I should be shooting for, but I still wonder if the stock injectors can handle the flow. I would rather wait a bit before installing the add. injector...or maybe I will just do both at once...I am interested to see what allmotor has to say since he did this successfully.

mrsteve

iTrader: (1)

The Comptech supercharger kit pushes the stock injectors to 100+psi. No injectors, that I know of, have failed from this kit.

bigguyonbike

thanks for the update mrsteve.

Smitty

those damn boost senders...

glad all is well...

derelict

After talking to Jimmy, he said it wouldn't be uncommon to see low FP after running the car a while, since aftermarket FPR's don't hold their pressure as well as stock when the car is off. And as long as the #'s rise back up to normal after a few minutes of driving, it should be fine. However he did say it's probably not wise to go WOT and push 6lbs of boost 10 seconds after starting up the car when the FP starts out that low.

I still only see -10psi of vacuum at startup/idle though. Definitely no boost leaking now either.

mrsteve

iTrader: (1)

It's not a good idea to boost the car at all until the car has reached operating temperature (i.e., fans come on)

speedr73

Hmm...I wonder maybe is the throttle stuck a bit open or do you still have a vacuum leak? Having a boost leak would not matter at idle since throttle position is at 0% or fully closed. When our throttle is fully closed even going 80mph you should still see about 20in of vacuum. Vacuum is dependent on throttle position.

mrsteve

iTrader: (1)

It could just be the gauge or vaccum line he connected the sender too. My gauge is connected to the vaccum line directly off the manifold going to the FPR. My vaccum pegs out at 30inHg while the throttle is closed.

speedr73

So you think it is where the gauge is connected? Mine is connected to the smaller of the three tubes that come out the back of the manifold. I get a steady 20in...maybe my line is pinched or you have a better vacuum source

speedr73

Oh and maybe a CL-S SC will run more vacuum than a TL-P?

mrsteve

iTrader: (1)

No, the J32 should pull 20 inches of mercury at 0% no matter what.

speedr73

I just read your response, but why did you say that the J32 should pull 20in no matter what, but then before you also said that your vacuum pegs out at 30in when throttle is closed?

mrsteve

iTrader: (1)

My gauge reads vaccum incorrectly.