Is anybody getting a sustained pressure drop on their Racetronix? When I start the car cold, my fuel pressure almost INSTANTLY hits 60psi. Over the next 15 seconds or so, it gradually climbs up to 69-70psi at idle. As far as I know, that is the highest fuel pressure anybody has seen from their Racetronix on this forum. After a while of using the car, my fuel pressure sits at 61psi at idle. It doesn't happen immediately... usually I have to run the car at WOT a few times to get it to drop. And it doesn't drop all at once... it gradually works its way back down to 61psi. This creates a problem for me, because my tune gets out of whack since injector flow is obviously lower at 61psi than at 69psi. In some cases I can run the car for an hour without a pressure drop at idle. In other cases (particularly when running the car hard), I can get back to 61psi in a matter of 10-15 minutes.

I am 99% confident that my fuel pressure gauge is accurately displaying fuel pressure because my car runs MUCH stronger at 69psi than it does at 61psi. In fact, in some cases I can hear minor pinging when my fuel pressure idles at 61psi and I'm at WOT. :eek: :eek:

I have talked to Andy and he didn't have any ideas off the top of his head why this would happen. I am going to replace the fuel pump and cross my fingers that the problem goes away. But if it doesn't, what can I do to help regulate fuel pressure? Is there a pressure regulator I can use so that it never goes over 61psi? Would a boost-a-pump help out? Voltage itself does not appear to be the problem since voltage is the same when I'm at 69psi vs. 61psi. Could it be amperage? :confused:

Also, just for my information, please post back your idle fuel pressure if you're running a Racetronix. I'd like to know if I have the only Frankenstein here running such high pressure.


[Modified by diynoob, 5:07 PM 1/18/2004]


[Modified by diynoob, 5:08 PM 1/18/2004]

 

If you disconnect the Hobbs switch does it still happen? I wonder if the switch is sticking on raising the voltage thus the pressure? :cheers:

Sorry I did not read the last part of your post. Prior to plumbing a return system I had just the Racetronix and the pressure was at 58 to 59 until I jumped on it then it went down to 45 or so them right back up. Now with the new fuel rails and Aeromotive regulator I have it set to 58 at atmosphere and then goes to 64 at WOT and 54 - 56 at vacuum. I still have a bit of pressure drop when I jump on it really hard. I am looking at adding my Vortech booster pump back on working towards 0 drop at WOT



[Modified by Steve'01, 3:27 PM 1/18/2004]

 

Thanks Steve,

I saw your return system writeup earlier. Very :cool: I think I would like to get to that kind of setup eventually. But right now I am just not sure why the setup I have, on a very mild car, is not working quite right.

I hope it is as easy as swapping the pump. I have already swapped the fuel filter which helped quite a bit, but I am not sure what else it could be.

 

i have the racetronix pump in my car and at the last dyno it stayed at a rock solid 60psi thru out both runs .......maybe you have a defective fuel filter/regulator :confused: :confused:


[Modified by corvette184, 1:14 AM 1/19/2004]

 

That's what I thought... but on my '02, the regulator is inside the filter... which I replaced. Before and after the replace I am still getting the same behavior... so it's gotta be the pump or somewhere else in the fuel plumbing. And from what I understand the lines that come from the fuel filter go straight to the fuel rails, right? If that's the case then that pretty much leaves the pump or voltage/amperage to the pump as the culprit.

 

diynoob, I would buy a new sender for the fuel gauge before braking down your system. The gauges are more prone to failure than the racetronix. I could be wrong but a new sender is only 30-40 bucks. The other option would be to reinstall the original pump for comparison. The stock pump should be good up to 500hp+ and for a short test run would give you some baseline comparisons. If it responds the same way then it would be electrical or the regulator. In any case drive it easy until you know for sure and keep us posted.
:confused:




[Modified by drcoffee, 8:08 PM 1/18/2004]

 

Here is my guess.

It's the regulator, not the pump. The regulator is sensitive to heat and the pressure drops as the heat of the fuel goes up.

I noticed my stock pump doing the same thing, but it got much more noticeable with the stronger racetronix pump – it overtakes the regulators ability to regulate at low demands. I would see 64 in the mornings and 58 in the afternoon after the car had really heated up. I thought it was caused by reduced voltage from the alternator then I noticed that the pressure would shoot back up when I put in a cold tank of gas (suddenly the mystery was solved). It was really noticeable on hot days.

I finally came to the conclusion that the regulator in the filter is junk for high HP applications (I'm sure others will chime in and say they made x HP with it….. but it does not take a rocket scientist so see why the design poor). Not only is it in the wrong place, but it has to regulate without the help of a vacuum source (this makes it susceptible to heat… ). You can get buy with it, but it makes tuning a royal PITA.

I just put in the '97 return system in my car (it was very very easy since the car is already provisioned for it - the only thing missing is the line and the rail). I have not ran the car hard yet, but might have some results and a writeup tomorrow. I have the ability to log fuel pressure, so I should be able to do a before/after graph.

 

I have been having issues with my fuel system also, just noticed yesterday. I first noticed extra noise coming from the wheel well where my kenne bell boost a pump is located. I don't know if it is the boost a pump or the racetronix. I just here what sounds like a vacuum cleaner noise sort of whine and I have been seeing fuel pressure drop from 65-67 at idle to 60-61 and 56-58 under 75- 100% throttle. I haven't made any changes actually haven't been driving the car as much since I got a new driver.

Have you been getting any additional noise from your pump?

 

:iagree: This is the correct answer here... :iagree:

VR :cheers:

 

Hey badblack,

Glad you mentioned that. I am a nimrod and can't believe I completely forgot to mention that there IS increased noise when my fuel pressure drops down. To me, it sounds like the sound water would make passing through a pipe that's too small. This happened with my old pump, although it was not nearly as noticeable... with the new pump the noise is a bit louder.

I don't have a boost-a-pump but it sounds like we're describing the exact same noise. It sounds like QuickSilver is on to something in his post above. When you upgrade to the '97 style rails, do you have to do the return line? Steve01's setup he posted a while back looked real :cool: and I'd love to do that to my car, I'm just not sure what kind of work is involved.

 

Another guess, but I think the noise you are hearing is more fuel going back into the tank via the return. I would hear a similar noise if I manually turned on my BAP.

Remember, the pump is generally always pumping the same volume, but the rate of consumption is constantly changing at the rail. So at idle, there is a lot of fuel going back into the tank. The pump never slows down (I don't think most people realize this).

 

Over the past 2+ years I've been running a SC, The fuel system has been one of the many issues I've had to work though, especially as you increase boost.

After closely monitering fuel pressure on long canyon runs, it was very clear that a few things dirrectly effect fuel pressure.

... Heat is a major factor, increase heat, potential loss of pressure.
.... As the fuel pump heats up and works harder it too is less eficient
.... Injector size is critical with high boost. You can get away with smaller injectors until things heat up, then they will become far less efficient.
....Gas can become vaperized under heavy pressure and heated conditions.
.... The wine is your fuel pump staining under the workload of the heat and supply demands.

Since I have a 98, I have the return line already. I have the regulator on the rail set at 60 psi. I run the LPE pump with a KB BAP. I run a vacuum line via a selonoid, which engages at 3#s of boost from the BAP pressure senser, to the fuel pressure regulator. This allows the car to run at 60psi untill I hit 3#s of boost, at which point I climb on a one for one basis to around 67psi at 10#s of boost.
The fuel system took a lot of work, just don't blow the motor while you sort it out.
Good luck
JB

 

I talked to Tom at LS1 Speed today about what kind of parts I would need to plumb for a return system. With the billet rails (which we saw in Steve01's setup) and the billet fuel pressure regulator, along with all fittings and 15 feet of braided line, he quoted me just under $500.

I like the look of the billet setup but I'm curious what these parts cost from GM, so anybody (hint hint QuickSilver) who's done this I'd love to hear your experiences/costs.
:cheers:

 

If you are really hot to get this mod going, I have attached a pic of a cart from http://www.gmpartsdirect.com with all the stuff you will need.

A few things to mention.
There is one part missing from the cart that is not required, but you will probably want it. It is the braided supply jumper line from the rail to the hard line (the return one is already listed). The existing one works, but it is too short and you really need the correct length to get the factory look. I have my original on, but I had to bend the hard line out and it looks pretty cheesy. I'm looking for that part# now and will include it in my final post. It should be about $30 more. I'm also looking into what it takes to make the existing fuel rail cover fit (or if the '97 style will fit, they will never fit unless you get the longer supply jumper).

You can probably get some of these parts used if you look around. I got the rail and the regulator for $150 shipped from a guy over on ls1tech.com that had purchased them, but never installed.

Also, the lines actually include two lines that could be used for the return. You could double up with someone and share the cost or something like that. One line is the return and the other is the EVAP line. They seem to be identical in size material... but the bends are quite different in the rear (the evap line is much longer but you can easily bend it down and get it where you need it. I will sell mine cheap if someone wants it (the shipping could be expensive - it is a big long box).

The mod is very easy. Everthing pretty much slips right in. The lines (a cluster of 3) are actually identical to what is on the car, but there is just an extra one in the middle. If you take your tunnle cover off you will notice that the current plastic line retainers actually have room for another line. They simply deleted the return in the newer cars.

The only pain about the install is that you have to take the exahust, intake manifold, and tunnel off the car. After that, it is a 30 minute deal.

I will post more details and some pics after I get my car running and tuned. I don't know why I'm even bothering putting it back together, I just pulled the trigger on my new motor today and will be doing that install in about a month. I figured I would try to work out a few more tuning kinks on this one while I don't have much to loose (just don't want to damage the heads).

 

I think jbsblownc5 has the right idea here. A setup that will index your fp in accordance with boost sure makes a TON of sense to me. I do wonder if a similar "indexing" effect can be had through proper dyno tuning of the injectors? :lurk:

 

Thanks QuickSilver! This is exactly what I was looking for... :cheers:

 

The problem here is mostly the FPR being at the back of the car and the diameter of the return line.

Changing the system to a front-mounted FPR system with return is the answer to all these problems.

A Charged Air Systems regulator is about $130.00, -6 TFE industrial line and fittings about $50.00. (Keep away from the rubber Aeroquip type lines)
Use the factory feed line. Silver solder two -6 fittings to the end of the factory rails and run lines into either side of the FPR. Run the -6 TFE line back into the tank with a bulkhead fitting w/o-ring. The factory return line can be used but an adapter fitting will have to be silver-soldered onto the stainless line. If the factory return is not used then make sure the fuel is directed back into the fuel module / bucket. Plug the return outlet on the factory fuel filter. Total parts cost of this conversion less labor should be under $200.00.


[Modified by Racetronix, 11:48 PM 1/19/2004]

 

Just as suspected, I had run out of gas a couple weeks ago and haven't been driving the car much. I knew I should change the filter but hadn't done it yet. I did it today and my noise went away, fuel pressure came back and car runs great!
Nice easy fix :D

 

Please post back how it works out after a few weeks. I changed my fuel filter too, suspecting that it was the problem, and it seemed to work VERY well when it was cold outside but when it gets hot my problem returns.

I used to idle at about 66-67psi prior to replacing the stock fuel filter at 26K miles, now I idle at about 69psi. But I can still see 61psi at idle after I get the car good and hot.

 

Hey QuickSilver,
I just wanted to post back that I have finally experienced the exact same thing. I rarely ever run my car down to E (usually fill up at 1/2 or 3/4 tank) but I was just so busy the last week that I didn't get to fill up. My fuel pressure was all the way down at 61 today where it rests when the car is hot, and right after I put in a full tank of fuel, my pressure was right back up to 69. I guess usually when I only put a little fuel in, it's not cold enough to affect the temperature of the rest of the hot fuel already in the tank, so I never noticed it until today.

Thanks for posting the other writeup on going to the 97 style fuel setup. I am hoping to get that mod done this coming weekend and solve most of my fuel delivery issues.
:cheers: