17 replies to this topic

[Maniac motorsports12]

I have a 97 and just bought a fuel pressure regulator. Unfortunately I do not have access to a dyno right now. Anyone out there have any experience with setting the fuel pressure on this car. I have heard that these cars run a bit lean and the motor could use a bit more pressure. Any help would be greatly appreciated.

Thanks
Mike

[FTodaro]

I have just installed the regulator on my car but have not yet set it on a dyno. I will pass on what has been told to me but I cannot confirm by experience "Yet". the average fuel pressure is about 60 psi. the regulator will be used to lower the pressure to lean out the motor. I have been told that if you set it at about 55 PSI that it will be close but safe. You may be leaving 1 hp on the table. some may be able to get it down to 52 PSI without burning a piston, but if you want to get it right to the limit you better get it on a dyno which can also monitor the Fuel air mixture.

On a different thread some guys were recommending installing a fuel air ratio gauge to monitor it.

So what you can do is buy a fuel pressure test Kit, set it at 55lbs and see what you get. If your going to go below that you may want to make the investment in the Fuel air Gauge or get it to a dyno

Some others my have a different experience.

[Maniac motorsports12]

Thanks Frank, thats at start.

[William Bonsell]

The whole fuel pressure adjustment issue as it relates to pre '99 cars has conjured up a lot of questions. Since I know there is a benefit to adjusting fuel pressure over the factory settings to maximize higher rpm HP, what about those of us who have sent their AFM's out for tuning. AFM tuning effectively leans out the car as I understand it, correct? I have also heard that fuel pressure adjusting is more effective with the stock AFM setting. Are we all just bringing a lot of unnecessary details and expense into the the whole equation, especially if you are satisfied being a solid mid pack car? As I see it, tune the AFM or play around with FP along with the A/F gauge. Will be interesting to see eventual dyno results as to the HP and Torque gains from all this.

[Ron Alan]

I have a 97 and just bought a fuel pressure regulator. Unfortunately I do not have access to a dyno right now. Anyone out there have any experience with setting the fuel pressure on this car. I have heard that these cars run a bit lean and the motor could use a bit more pressure. Any help would be greatly appreciated.

Thanks
Mike

In our experience(dyno) and others I've talked with...the 1.8's run rich...opposite of what you've stated. Leaner=more power...to a point of course. Drago offers another solution in the classifieds for those on a budget but want something more. He sets the stock FP regulator to an ideal pressure...you can read his ad to see what that is. Very much considering going this route!

[trimless]

In our experience(dyno) and others I've talked with...the 1.8's run rich...opposite of what you've stated. Leaner=more power...to a point of course. Drago offers another solution in the classifieds for those on a budget but want something more. He sets the stock FP regulator to an ideal pressure...you can read his ad to see what that is. Very much considering going this route!

+1

The 1.8's run rich not lean. The 94/95 OBD1 are very rich with stock fuel pressure and the 96/97 OBD II not quite so rich but you will need to lower fuel pressure (in most cases) for the best power. Your factory service manual will offer details on the stock fuel pressure range. As others have stated, don't make any changes without a proper AFR gauge or dyno AFR readings to prevent a motor meltdown from running too lean.

[davew]

I am selling regulator kits for both NA and NB models, so take this as being a biased opinion.

The 1.8 cars, both NA and NB, run rich. There is no trap door on the air flow meter, so there is no adjustment possible. The cars do run rich, so by lowering the fuel pressure, you can lean out the engine. Thus getting more power. But too lean will melt down any motor.

The 1.6 cars have the trap door style air flow meter. There are a couple things inside the box that can be "adjusted". This is not a factory adjustment, but it works, if you know what to do. The idea is too fool the ecu into thinking less air is going into the engine, so it supplies less fuel. Tuning this type of air flow meter is an art form.

The adjustable fuel regulator on a 1.6 eliminates the need for playing with the air flow meter. We can now simply turn a screw and make the car leaner. I have had better success on the dyno with fuel pressure than air flow meter adjustments. My opinion is that fuel pressure is much more accurate and repeatable.

The 1.8 cars are a little simpler to give a baseline on. Since there is no other adjustment to take into account. You simply lower the pressure and you are done. Personally I would only do this on a dyno with a wide band air/fuel ratio guage. But a baseline number can be given.

The 1.6 cars are a little trickier. Due to the variations in even a stock air flow meter, a baseline fuel pressure recomendation is not that accurate. And if your air flow meter has been adjusted, who knows where to set fuel pressure. So a dyno tune is even more important.

As far as an air/fuel ratio meter (commonly called a Lamda sensor) in the car goes, it is a good idea. But you have to look at it. If you really want to get the most from tuning, I would put the gauge into a data logger so you can review the info at all points on the track and at all RPMs.

Just my opinion
Dave

[5X Racing]

An air/fuel ratio gauge is a must in my opinion, especially when adjusting fuel pressure. The benefits of one go beyond just monitoring too, they are useful tuning tools as well.

I wouldn't recommend adjusting your fuel pressure without one, especially if you are running one of our afpr's. I would consider an adjustable fuel pressure regulator a waste without an afr gauge, unless you have a reputable shop dyno tune it for you. We do our tuning at the track, the afr gauge is a necessity for us for sure.

Might sound like a broken record, but I don't want to see people blowing motors due to blindly adjusting fuel pressures.

[Maniac motorsports12]

[quote name='davew' timestamp='1298391122' post='2893']
I am selling regulator kits for both NA and NB models, so take this as being a biased opinion.

The 1.8 cars, both NA and NB, run rich. There is no trap door on the air flow meter, so there is no adjustment possible. The cars do run rich, so by lowering the fuel pressure, you can lean out the engine. Thus getting more power. But too lean will melt down any motor.

The 1.6 cars have the trap door style air flow meter. There are a couple things inside the box that can be "adjusted". This is not a factory adjustment, but it works, if you know what to do. The idea is too fool the ecu into thinking less air is going into the engine, so it supplies less fuel. Tuning this type of air flow meter is an art form.

The adjustable fuel regulator on a 1.6 eliminates the need for playing with the air flow meter. We can now simply turn a screw and make the car leaner. I have had better success on the dyno with fuel pressure than air flow meter adjustments. My opinion is that fuel pressure is much more accurate and repeatable.

The 1.8 cars are a little simpler to give a baseline on. Since there is no other adjustment to take into account. You simply lower the pressure and you are done. Personally I would only do this on a dyno with a wide band air/fuel ratio guage. But a baseline number can be given.

The 1.6 cars are a little trickier. Due to the variations in even a stock air flow meter, a baseline fuel pressure recomendation is not that accurate. And if your air flow meter has been adjusted, who knows where to set fuel pressure. So a dyno tune is even more important.

As far as an air/fuel ratio meter (commonly called a Lamda sensor) in the car goes, it is a good idea. But you have to look at it. If you really want to get the most from tuning, I would put the gauge into a data logger so you can review the info at all points on the track and at all RPMs.

Just my opinion
Dave

Dave, given the fact that you can not adjust the AFR on the 97, If you dyno the car and set the fuel pressure for max HP, how do you know that the car is not now running too lean?

[Tom Hampton]

From a theoretical standpoint you would think the 1.6 AFM could be used to control the SHAPE of the mixture. While the regulator could shift the whole curve up/down. Thus providing at least the potential to maximize the power under the curve.

[Maniac motorsports12]

Dave,
given the fact that you can not adjust the AFR on the 97, If you dyno the car and set the fuel pressure for max HP, how do you know that the car is not now running too lean?

[Ron Alan]

Dave,
given the fact that you can not adjust the AFR on the 97, If you dyno the car and set the fuel pressure for max HP, how do you know that the car is not now running too lean?

Your dyno will give you a AFR...along with HP and torque under a graph. As you adjust your FP these numbers and curves will change. Based on what your tuner feels is a safe AFR you'll set your pressure to maximize the other 2. My understanding...though a complete rookie. Looking forward to doing our car as funds come in

[Graeme]

Now that people are using an adjustable FPR, will anyone share their target air/fuel ratio information? I have an wideband LC-1 installed and I am wondering what ratios others are shooting for.

Thanks,
Graeme
Golden, CO

[FTodaro]

13.1 to 13.5 between 6 & 7,000.

[WarmShoe]

I have just installed the regulator on my car....

Frank, can you recommend a source for the regulator? Any other bits/pieces required. Just replace OEM (I have '94)?

Jon

[Ron Alan]

Frank, can you recommend a source for the regulator? Any other bits/pieces required. Just replace OEM (I have '94)?

Jon

Got ours from Dave Wheeler(advanced autosports)...everthing you need including instructions! 10 minutes!!!

But you will need a gauge to check pressure and a dyno to find the sweet spot.

[tom1977]

I understand that this is an old thread... for a 1.8L, is this discussion related to stock base timing or are some running slightly advanced? Obviously A/F monitoring is necessary...

[38bfast]

Yes you will tune timing and AF on the Dyno