Fuel Pressure Regulator

Which Car? in a 5.0 you have to take off the upper manifold, if you haven't before, then you have to cut that bar in the back that hold upper/lower together. I read another article that discussed how fussy tuning it was, so I kept with stock, and later got the car professionally tuned with a wideband sensor and new chip. still has stock Fuel pressure gague.

1993 5.0 8# KB

Ewww... The car is an 89 LX Convertible 5.0. Removing the upper, and cutting some bar seems like more than I wanted for a quickie upgrade, for some unknown gain. Thanks for the info.

One article (by an individual, not a company) seemed to suggest increasing fuel pressure would allow me to support more timing advance. I currently have the car @ 11 BTDC, with no pinging. With fuel prices where they are, I REFUSE to advance it more to where I would need premium. Would higher pressure allow more advance, on regular unleaded?

There is a guy locally, actually a GM LT engine tuner, who has a dyno and told me that with the mods I have and a perfect tune up, he could tune 20-60 HP out of my Mustang with an adjustable fuel pressure regulator.

I've been told if you want all the power you can get out of larger injectors, you must install and adjustable regulator.

I don't under stand that cut the bar thing, but I have an Edelebrock intake.

Ewww... The car is an 89 LX Convertible 5.0. Removing the upper, and cutting some bar seems like more than I wanted for a quickie upgrade, for some unknown gain. Thanks for the info.

One article (by an individual, not a company) seemed to suggest increasing fuel pressure would allow me to support more timing advance. I currently have the car @ 11 BTDC, with no pinging. With fuel prices where they are, I REFUSE to advance it more to where I would need premium. Would higher pressure allow more advance, on regular unleaded?

increasing the fuel pressure will seem like you have larger injectors, a trick they do all the time with FMU's and blowers, but the computer will cut back the pulsewidth the injector to compensate, so you get the same HP unless you get more air into engine. So you can get more fuel, but not more air, it is stuck at 70% without getting new heads to improve airflow, or a blower. I think 10 is stock timing setting, some have gone to 15, and listen for pings (risky) but could work, depends on how much carbon you have built up in your engine, and switch to next colder spark plugs to reduce det. You could use premium and bump the timing up more, but, if you get a tank of bad (or regular) gas, "ping city" and with summer coming on (more heat, more det)

Putting in a thermostat at 180 keeps the engine a little cooler. Putting in a new/rebuilt 3 core radiator is easy, but I got one off the west coast and it worked worse than the one I took off. So got another. There are some great buildups in the old 5.0 Mags late 90's and 2000, may be at a libarary ??? Show what works what dosent. The 5.0 is already very well optomized. Some good summer performance tires made a huge difference for me, I had some really old cop tires that got too hard, smoked nice, but little traction, switched to BF Goodrich g-sport (had to fit 15 inch cop rims)

the stock 93 had a flipping bar in the back side, about 1/4 inch that tied the upper to lower manafold together about a foot long between engine and firewall, had to cut it when putting on the Keene Bell, this was an old cop car too has a few other slight mods, but I thought the bar was stock, and lame, did nothing mechanical except keep uppper and lower together. Did you run into this when you put the Edelebrock on?

Without knowing your plan it is hard to say if a regulator is beneficial at this time or at all. Where I think fuel pressure becomes a big concern is when turbos or superchargers are installed. Then fuel pressure has the added burden of overcoming the boost pressure and the overall fuel system might need improved to supply fuel at the required pressure AND volume. If you are staying N/A then it isn't as much a concern and the custom tune you should get will compensate for any little variation in fuel pressure you may have now.

So, what's your plan?

You're not going to get much, if any, horsepower from just replacing a working regulator and messing with fuel pressure. You can make the engine run richer by increasing fuel pressure during WOT but that doesn't necessarily make more power. Personally, I wouldn't waste my time on this now. You have a plan so stick to it. These little distraction are just wasting money that can be better spent on parts included in the plan. I have wasted so much money on my car by breaking from the plan that I would cry a river of tears if I added it up.

Actually, the computer goes into a different operating mode when the engine is near Wide Open Throttle (WOT). It doesn't use the O2 sensors (i.e. doesn't operate in closed loop mode) and relies on preprogrammed tables for fuel, timing etc based on MAF readings. Increasing fuel pressure will affect the A/F but the stock computer on the 5.0L engines are fairly decent and I would bet he will gain nothing or even lose power at WOT. This could also make the engine not be able to operate in closed loop mode which will trash his gas mileage under normal driving conditions. IMO, he is better off bumping the timing as much as possible for the octane gas he uses.

This trick causes the engine to stay out of closed loop mode and runs the engine from the table values programmed into the computer. The computer never gets the signal that the engine has fully heated up. It will run the engine rich and trash gas mileage once again and it could wash the cylinder walls with gas and over time cause excessive wear on the cylinder walls. It also puts more unburned gasoline into the oil and can reduce its lubricating abilities. This is another trick I don't recommend either.

If more fuel is needed, he should put in

1 higher volume gas pump in tank, 2 larger injectors, then a fuel regulator(if needed) (and that is just fuel, not air)

oh, THE PLAN! find a HP buildup in the old 5.0s and follow that, putting on the low cost high HP first etc. Most mods add little HP, and arn't worth doing. Save those $s for a supercharger.

I don't know what your mods are but on a N/A engine I can't see getting anywhere near that improvement from just adjusting fuel pressure. If it is out of spec that far then you should be experiencing drivabilty issues, IMO. Maybe there is that much power to be had if you change other parameters on the computer or if you have a blower. But even with a blower I would think you would have melted a piston or two from running lean under WOT with an out-of-wack fuel pressure regulator.

I suspect Jim is veering from his plan. He needs to remember that many people that think they know something about making horsepower really don't know that much and will lead you to headache after headache. When I went with the Kenne Bell twinscrew I heard all kinds of BS from supposedly knowledgeable 5.0L engine builders. They said it wouldn't make power and I should get a centrifugal blower etc. Well most times they suggested this because they got deals from those manufacturers and Kenne Bell didn't have dealers at that time. since they had not experience with twinscrew blowers they would just trash them instead of figuring out how to get the most from them. I ended up getting 425 rwhp but more importantly I got 460 ft-lbs of torque at the rear wheels at under 2,500 rpm using a twinscrew. Speed shop mechanics are like doctors, engineers etc. There are good ones and bad ones and many can't think outside the box or beyond what makes them the most money.

agreed, WOT is suppose to be a little on the rich side, but may not be, which is not good if lean and too much timing.

With the 160s that can be true, but with the 180 thermostat I put in, the engine still heats up to 220 anyway even in winter. And the engine runs in closed loop about 10 to 15 seconds after starting it now, dosent seem to be dependent upon engine temperature, (perhaps this should be exaust temperature?) before it took about 30 to 40 seconds (had the engine rebuilt @140K miles due to too much carbon on one plug, was oil wet too) I have an indicator that watches the O2 sensor outputs, and when they come on, the engine is in closed loop sensors are putting out 1/2 volt square wave stuff indicating the computer is keeping the air/fuel ratio at 14.7 for min emmissions, actually walking across 14.7 back and forth. Perhaps that 30 to 40 seconds was too rich waiting for closed loop to kick in, O2 sensors heat up. Is there another way to tell if engine is in closed loop?

Thermostats are not exact temperature either, they start to open at temp A, then are fully open at temp B, and the engine temp is slower to respond, as it has a large mass to heat up. Would like to see some real numbers on this stuff, but have not. I don't see any dramatic improvements from changing the thermostat either.

Thank you ALL for the input - it's all good stuff.

After much discussion, I figured I'd commit my plan to writing, and post it. It's the next discussion topic in this group, at

whatever reason (I can't fully explain it) I want to staynaturally aspirated, just dialing the fun-factor up within that limit.My next big step is the Eibach suspension kit, and I'm mainly killingtime on audio and maybe the FPReg until I man up (and ante up $$$ moreimportantly)and take it to the shop for the Eibachs. Take a look atmy plan and let me have your thoughts.

Mine was a 100% stock 89 LX and I have no clue what the bar is, so I'd have to say that was not on my car. If I had to take a guess, I'd say it was a cop mod rather than a difference between 89 to 93.

I'm skeptical as well, which is why I've never done it. I did go back to a normal thermostat though for just the reasons that you mentioned.

My new plan, spend $500 and whip that loping 2006 GTO I see around town....

I have one word for you.... nitrous.