When I turn on the ignition (not started) the gauge goes to 55 while priming, then immediately drops to 42 or so and holds steady. Is this behavior normal? I was curious whether or not the pressure should hold closer to the 55 it goes to during priming.
Fuel pressure question for those with a gauge
1 - 15 of 15 Posts
Joined
·
2,309 Posts
Test it or log it
I am assuming that the pressure changes with boost level(?) - Are you running a vacume/pressure line to the regulator? and are you running a regulator?
You would want to make sure that the pressure is both stable and where it should be.
But one can also do this exercise without the engine running at WOT, but the engine may need to be running to keep the pump energized?
To do this is to hook up a vacume pump (they make hand operated units) and pull off the fuel return and put it into a container. Then measure the flow over some period of time.
Then repete the procedure with boot going into the regulator, and measure that flow over time. Then compare the flow that you are getting at the pressure you selected (with the boost going into the regulator), to the flow required for that WOT condition.
Logging the pressure is usually the best way.
I am assuming that the pressure changes with boost level(?) - Are you running a vacume/pressure line to the regulator? and are you running a regulator?
You would want to make sure that the pressure is both stable and where it should be.
But one can also do this exercise without the engine running at WOT, but the engine may need to be running to keep the pump energized?
To do this is to hook up a vacume pump (they make hand operated units) and pull off the fuel return and put it into a container. Then measure the flow over some period of time.
Then repete the procedure with boot going into the regulator, and measure that flow over time. Then compare the flow that you are getting at the pressure you selected (with the boost going into the regulator), to the flow required for that WOT condition.
Joined
·
6,306 Posts
FP when the car and pump are off is generally not a relevant measurement. It will drop significantly from pump running to pump off. The only thing your interested in with the pump and engine off is how long the pressure takes to drop to zero thereafter.
With the car idling, what is your pressure? Assuming a stock (or stock-ish) fueling system design, my guess is that the pressure is fine since you're seeing 50+ during the prime....
With the car idling, what is your pressure? Assuming a stock (or stock-ish) fueling system design, my guess is that the pressure is fine since you're seeing 50+ during the prime....
Car has vf tvs kit. Pressure at idle is 57-58 or so. Seems steady at idle, and when the car is turned off, it takes quite some time for the pressure to return to 0. At least 20-30 minutes (haven't really timed it.)
I pulled the plugs, they looked decent, light peppering if any. They were however a 6 heat range (gapped way too far) and looked a bit hot. I put ngk bkr7e's back in it.
Feels great accelerating with 75-80 percent throttle. So, I'm hoping that it was some combination of bad gas and/or the plugs. But, I'm a little timid to go back wot to confirm one way or another.
I pulled the plugs, they looked decent, light peppering if any. They were however a 6 heat range (gapped way too far) and looked a bit hot. I put ngk bkr7e's back in it.
Feels great accelerating with 75-80 percent throttle. So, I'm hoping that it was some combination of bad gas and/or the plugs. But, I'm a little timid to go back wot to confirm one way or another.
Joined
·
6,306 Posts
Do you have an aftermarket surge tank or something?
Those pressure numbes are not correct on the stock delivery system. You'll see 47 +/- at idle with the stock pump and 50+/- with a wally 255 with the in-tank setup.
Outside of that, "peppering" is a sign of detonation. If you indeed saw detonation peppering, that's obviously bad. The Ngk 7 plugs are the correct ones to run for FI. The standard gap on the -11 (dash 11) suffixed plugs will work for many setups. The higher HP setups will misfire badly (felt by the driver) with -11 gaps. The standard, non -11 plugs come with .032" gap and will remedy that issue. Doesn't sound like your issue though.
If you're concerned about a fueling issue, you should run a WB 02 to determine whether or not she's running lean/rich at WOT.
I think I have a VF TVS tune on file. What year is your car?
-Phil
Those pressure numbes are not correct on the stock delivery system. You'll see 47 +/- at idle with the stock pump and 50+/- with a wally 255 with the in-tank setup.
Outside of that, "peppering" is a sign of detonation. If you indeed saw detonation peppering, that's obviously bad. The Ngk 7 plugs are the correct ones to run for FI. The standard gap on the -11 (dash 11) suffixed plugs will work for many setups. The higher HP setups will misfire badly (felt by the driver) with -11 gaps. The standard, non -11 plugs come with .032" gap and will remedy that issue. Doesn't sound like your issue though.
If you're concerned about a fueling issue, you should run a WB 02 to determine whether or not she's running lean/rich at WOT.
I think I have a VF TVS tune on file. What year is your car?
-Phil
Car is an 05. I appreciate the offer, but I think at this juncture I'm going to try to get Jermaine to find some time to fly out and do a dyno tune on it. I've always been pleased in the past with my vf2 kit and hope to get this one straightened out also.
I may be interested down the road in a tune from you guys. I've seen where you integrated an air temp sensor post intercooler and I do think that would be a significant advantage.
Part of me thinks that I may be just getting used to the sounds of the new set up. I felt that I heard something and backed off. But, I've also upgraded to a decat and one of your silent touch mufflers, and the sound of that when the second cam comes on is very loud. Almost like an exhaust leak. I could have attributed some new noise to being detonation. I've built several cars, but I don't consider myself to be an expert or anything. Just trying to be precautious.
I may be interested down the road in a tune from you guys. I've seen where you integrated an air temp sensor post intercooler and I do think that would be a significant advantage.
Part of me thinks that I may be just getting used to the sounds of the new set up. I felt that I heard something and backed off. But, I've also upgraded to a decat and one of your silent touch mufflers, and the sound of that when the second cam comes on is very loud. Almost like an exhaust leak. I could have attributed some new noise to being detonation. I've built several cars, but I don't consider myself to be an expert or anything. Just trying to be precautious.
Joined
·
2,309 Posts
If the pressure at idle is ~50, then what should the pressure be at boost?
Joined
·
6,306 Posts
The 2ZZ has a fixed FPR in the fuel tank and is a deadhead system... So with a wally 255, it will idle at ~50-52 and drop ~5psi at the rail with the stock fuel system and 275whp at redline.
Here's a pic of a log I took years ago from my car with a "hot wired" wally 255 in an otherwise stock system. This is about the healthiest you'll see a stock system from a FP standpoint. On throttle it went from 52 to 47 at 10 psi boost, so 37 at the injector nozzle.
Not saying this is ideal, but it's how 99.5% of the FI'ed 2zz Lotuses are out there...
Joined
·
6,306 Posts
No worries, I didn't mean to offer a new tune. I don't have any VF tunes to offer. I was just going to look at what I had on file and study the spark and fuel curve they are using to see if it might be more likely a tune that's just on the ragged edge in a car that's "ping happy" or if a hardware issue may be more likely... By all means, you should go back to your vendor:up:
Phil
That's very generous of you. I would really appreciate that if you have the time and wouldn't mind taking a look. Any advise is helpful.
On the subject of second cam exhaust note, does my description sound normal with the silent touch and a decat? Very deep and controlled on the first cam, and almost like a straight pipe on the second cam.
On the subject of second cam exhaust note, does my description sound normal with the silent touch and a decat? Very deep and controlled on the first cam, and almost like a straight pipe on the second cam.
Joined
·
6,306 Posts
Sounds about right... The idea is that exhaust is mild enough for the DD but will still bark at your neighbors when asked to...
As for the map. Checked out a VF TVS map we have on file and total timing is in the 29 degree range for spark advance. That's a good bit of timing for a boosted 2ZZ on pump gas... No way of knowing if your map has that kind of timing in it. If it does, it could just be that the motor is detonating and needs some spark pulled out of it.
2 cents from afar...
-Phil
Joined
·
2,309 Posts
2-1/2 bar (37 psi) seems pretty low for a dependable system.
I can now see why there is so much drama related to fuel pressure.
1 - 15 of 15 Posts
Join the discussion
Join now to ask and comment!