Bogging Under Hard Acceleration

Smokedawg · 06-28-2001, 07:56 AM

As posted in Street Racers forum. I raced another Mustang the other day and when I hit second gear the motor bogged horribly. I thought it was my error somehow upon shifting. Then yesterday I went to pass someone and downshifted to third and hit it and as soon as I stuck the pedal to the floor it just acted as if I ran out of fuel completly. I think I might have my FPR cranked up a bit to far. Do you guys think that to much fuel could cause this bogging? Thanks for all advice.

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347 Stroker Motor: Balanced, Cobra Transmission, Extrude Ported and Polished Upper and ported Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, 30lb Bosch Injectors, Holley AFPR, March Underdrive Pulleys, Perma-Cool Fan, 3-Core Radiator, Accel Performance Coil, Accel 300+ Racing Wires, Ram Air, K&N Filter, 73mm Vortech MAF, 70mm TB, FlowMaster Exhaust w/BBK Offroad H-Pipe, Hurst Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, AC and Smog del, rear seat del.

jimberg · 06-28-2001, 08:43 AM

With 30# injectors, you should have your fuel pressure at the stock 39 psi. You aren't getting over 500 hp. Your MAF is too small for your throttle body, but that's a different issue.

Is this problem something new? Has your car run better with all the same settings? Was it hot out? Give us more details.

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351W 89 Mustang GT Convertible

Smokedawg · 06-28-2001, 08:55 AM

I would say that the temp is around 80 degrees. If the throttle body is only 70mm, the MAF is 73, why would I need a bigger MAF if I can only shove so much air through a 70mm hole. I dont want the air to bottleneck on me. I dont know if you can understand what I am saying because it even sounds a little confusing to me trying to read it.

I have had this setup for awhile and it has ran strong before. After it bogged on me trying to pass the other vehicle. I went off onto a country road and tried a few hard launches up through 3 gears and the problem never came back. Its just when I really want the power to get up and move my car, it doesnt want to give it to me.

------------------
347 Stroker Motor: Balanced, Cobra Transmission, Extrude Ported and Polished Upper and ported Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, 30lb Bosch Injectors, Holley AFPR, March Underdrive Pulleys, Perma-Cool Fan, 3-Core Radiator, Accel Performance Coil, Accel 300+ Racing Wires, Ram Air, K&N Filter, 73mm Vortech MAF, 70mm TB, FlowMaster Exhaust w/BBK Offroad H-Pipe, Hurst Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, AC and Smog del, rear seat del.

jimberg · 06-28-2001, 08:58 PM

You want a taper in your intake. Did you know TFS intake runners are tapered? Anyway, as the air rushes in, the taper causes the air to increase in velocity giving it more momentum. When the intake valve snaps shut, the volume of air moving into the intake and down the runner compresses at the bottom of the runner and then expands upward where it bounces off the air in the plenum and heads back down the runner. You have essentially have a column of air bouncing back and forth in the runner. The runners are tuned to a certain RPM so that the air bouncing back an forth will rush in just as the intake valve opens. This actually gives you more air in your cylinders than if you just had the piston sucking air directly through the intake port. This is why you get more torque with longer runners. Short runner intakes have less bounce and less air packing potential, but you are correct that they can give you more horse power at the top end. That's runner length, though. By not tapering enough at your initial point of intake, you're essentially lowering your low-end torque potential and your high end as well.

That's the gist of it. It may not be 100% right since I was explaining off the top of my head, but it's close enough that you should be able to get the theory behind it.

I don't really have more to add as far as your problem. Lower the fuel pressure and see if it makes a difference.

------------------
351W 89 Mustang GT Convertible

06-28-2001, 07:56 AM	#1
Smokedawg Tires Fear Me... Join Date: Jan 2001 Posts: 867	Bogging Under Hard Acceleration As posted in Street Racers forum. I raced another Mustang the other day and when I hit second gear the motor bogged horribly. I thought it was my error somehow upon shifting. Then yesterday I went to pass someone and downshifted to third and hit it and as soon as I stuck the pedal to the floor it just acted as if I ran out of fuel completly. I think I might have my FPR cranked up a bit to far. Do you guys think that to much fuel could cause this bogging? Thanks for all advice. ------------------ 347 Stroker Motor: Balanced, Cobra Transmission, Extrude Ported and Polished Upper and ported Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, 30lb Bosch Injectors, Holley AFPR, March Underdrive Pulleys, Perma-Cool Fan, 3-Core Radiator, Accel Performance Coil, Accel 300+ Racing Wires, Ram Air, K&N Filter, 73mm Vortech MAF, 70mm TB, FlowMaster Exhaust w/BBK Offroad H-Pipe, Hurst Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, AC and Smog del, rear seat del.

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06-28-2001, 08:43 AM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	With 30# injectors, you should have your fuel pressure at the stock 39 psi. You aren't getting over 500 hp. Your MAF is too small for your throttle body, but that's a different issue. Is this problem something new? Has your car run better with all the same settings? Was it hot out? Give us more details. ------------------ 351W 89 Mustang GT Convertible

06-28-2001, 08:55 AM	#3
Smokedawg Tires Fear Me... Join Date: Jan 2001 Posts: 867	I would say that the temp is around 80 degrees. If the throttle body is only 70mm, the MAF is 73, why would I need a bigger MAF if I can only shove so much air through a 70mm hole. I dont want the air to bottleneck on me. I dont know if you can understand what I am saying because it even sounds a little confusing to me trying to read it. I have had this setup for awhile and it has ran strong before. After it bogged on me trying to pass the other vehicle. I went off onto a country road and tried a few hard launches up through 3 gears and the problem never came back. Its just when I really want the power to get up and move my car, it doesnt want to give it to me. ------------------ 347 Stroker Motor: Balanced, Cobra Transmission, Extrude Ported and Polished Upper and ported Lower, GT40 Milled Ported and Polished Heads, B303 Cam, BBK 1 5/8 Headers, 30lb Bosch Injectors, Holley AFPR, March Underdrive Pulleys, Perma-Cool Fan, 3-Core Radiator, Accel Performance Coil, Accel 300+ Racing Wires, Ram Air, K&N Filter, 73mm Vortech MAF, 70mm TB, FlowMaster Exhaust w/BBK Offroad H-Pipe, Hurst Shifter, 3:55 Gears, Ram Clutch, Cross Drilled Rotors, AC and Smog del, rear seat del.

06-28-2001, 08:58 PM	#4
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	You want a taper in your intake. Did you know TFS intake runners are tapered? Anyway, as the air rushes in, the taper causes the air to increase in velocity giving it more momentum. When the intake valve snaps shut, the volume of air moving into the intake and down the runner compresses at the bottom of the runner and then expands upward where it bounces off the air in the plenum and heads back down the runner. You have essentially have a column of air bouncing back and forth in the runner. The runners are tuned to a certain RPM so that the air bouncing back an forth will rush in just as the intake valve opens. This actually gives you more air in your cylinders than if you just had the piston sucking air directly through the intake port. This is why you get more torque with longer runners. Short runner intakes have less bounce and less air packing potential, but you are correct that they can give you more horse power at the top end. That's runner length, though. By not tapering enough at your initial point of intake, you're essentially lowering your low-end torque potential and your high end as well. That's the gist of it. It may not be 100% right since I was explaining off the top of my head, but it's close enough that you should be able to get the theory behind it. I don't really have more to add as far as your problem. Lower the fuel pressure and see if it makes a difference. ------------------ 351W 89 Mustang GT Convertible