1987 - Turbo - issues at about 4000 RPM
07-27-11, 02:52 PM
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1987 - Turbo - issues at about 4000 RPM
Hello everyone, I'm new to this forum. I have a 1987 Turbo, engine was built from RX7 specialties with 3mm seals and has been ported. For fuel I have SE injectors and a cosmo fuel pump along with the fuel cutoff defense switch. Exhuast is a downpipe straight to a Y pipe with two tube mufflers.
Issue I'm having is after my car warms up and I'm driving down the highway if I downshift from 5th to 4th or 3rd and try and step on it once the turbo starts to spool up it at 4K it doesn't climb RPM's very fast.
What makes this confusing is that it doesn't do this when its cool or only been running a few minutes. Seems that if I'm driving the car for a period of time without having the turbo spool up, when I then try and give it full gas it starts to sputter like its either getting too much or not enough gas.
My apologies for my poor description, if anyone has any ideas they would be greatly appreciated.
Thanks,
Issue I'm having is after my car warms up and I'm driving down the highway if I downshift from 5th to 4th or 3rd and try and step on it once the turbo starts to spool up it at 4K it doesn't climb RPM's very fast.
What makes this confusing is that it doesn't do this when its cool or only been running a few minutes. Seems that if I'm driving the car for a period of time without having the turbo spool up, when I then try and give it full gas it starts to sputter like its either getting too much or not enough gas.
My apologies for my poor description, if anyone has any ideas they would be greatly appreciated.
Thanks,
07-27-11, 06:42 PM
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Currently I have it running at 10lb of boost on the factory turbo. I took it for another rip this afternoon trying to see if I could get some more knowledge as to what's happening.
Seems as though if I redline it in first and then go to second I don't get any sputtering or slow RPM increase as it only drops back down too about 4500-5000.
However I do get that same issue in 2nd, 3rd, 4th and if I have enough room and space to go fast enough I will in 5th as well....
Makes me think I may need to pull the fuel pump and see what's happening down there as at high RPM from first onward its ok, its just if I am starting in 2nd or 3rd and am driving at about 2000 or 3000rpm and then step on it, that's when I get the sputtering or hesitation.
Make any sense?
Seems as though if I redline it in first and then go to second I don't get any sputtering or slow RPM increase as it only drops back down too about 4500-5000.
However I do get that same issue in 2nd, 3rd, 4th and if I have enough room and space to go fast enough I will in 5th as well....
Makes me think I may need to pull the fuel pump and see what's happening down there as at high RPM from first onward its ok, its just if I am starting in 2nd or 3rd and am driving at about 2000 or 3000rpm and then step on it, that's when I get the sputtering or hesitation.
Make any sense?
07-28-11, 09:07 AM
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Yes it should be the stock fuel pressure regulator. I was of the understanding that if I upgraded to a cosmo fuel pump and installed the fuel cut defense chip that my fuel issues should be alright, especially with 680cc injectors....am I wrong?
07-28-11, 10:15 AM
#6
While your fuel setup may work, it's not the safest or most fine tuned way to go about running more boost on a stock turbo. FCDs are absolute garbage due to the way they trick the ECU into thinking boost pressure is lower than it really is. This can have a negative effect on fuel and timing calculations.
If you're using a Cosmo 13b or even 20b fuel pump, you'll have plenty of flow at higher pressures (under boost). A 20b pump will probably increase fuel pressure a little more than stock. Pump upgrades are always a wise choice.
When you say you have GSL-SE 680cc injectors, I assume you mean the secondaries only? It would barely idle, and stutter badly down low if you use them as primaries with no fuel tuning. As secondaries, you're netting as much as 12% extra fuel (2460cc / 2200cc) under boost & above 3800 RPM. This is helpful, but some fine tuning would prevent the mixture from getting too rich at partial throttle/low boost.
Something else to consider is that the secondaries don't come on until 3800 RPM, but you can easily make 10+ psi as low as 2500-3000 RPM if you're in a tall gear. Stock primaries can max out before the secondaries come online, which leads to a small lean spot in the middle of the RPM band.
So getting back to your problem, the FCD's job is the fool the ECU and prevent it from cutting fuel to the rear rotor at 8.6 psi. It almost sounds like you are still hitting fuel cut (even though you shouldn't be able to), since peak boost will not be very high in 1st gear. Offhand, I think I usually see 8-9 psi max in datalogs. From 2nd on, load will be higher, and you'll be able to make more pressure. I would suggest turning your boost controller down, or disconnecting it temporarily. Disconnect the FCD, and see how it drives. Note that if your wastegate is not ported & you have a free-flowing intake/exhaust, pressure will still creep higher & you will hit fuel cut. Back off the throttle, and see if you can get to redline making low boost.
If you're using a Cosmo 13b or even 20b fuel pump, you'll have plenty of flow at higher pressures (under boost). A 20b pump will probably increase fuel pressure a little more than stock. Pump upgrades are always a wise choice.
When you say you have GSL-SE 680cc injectors, I assume you mean the secondaries only? It would barely idle, and stutter badly down low if you use them as primaries with no fuel tuning. As secondaries, you're netting as much as 12% extra fuel (2460cc / 2200cc) under boost & above 3800 RPM. This is helpful, but some fine tuning would prevent the mixture from getting too rich at partial throttle/low boost.
Something else to consider is that the secondaries don't come on until 3800 RPM, but you can easily make 10+ psi as low as 2500-3000 RPM if you're in a tall gear. Stock primaries can max out before the secondaries come online, which leads to a small lean spot in the middle of the RPM band.
So getting back to your problem, the FCD's job is the fool the ECU and prevent it from cutting fuel to the rear rotor at 8.6 psi. It almost sounds like you are still hitting fuel cut (even though you shouldn't be able to), since peak boost will not be very high in 1st gear. Offhand, I think I usually see 8-9 psi max in datalogs. From 2nd on, load will be higher, and you'll be able to make more pressure. I would suggest turning your boost controller down, or disconnecting it temporarily. Disconnect the FCD, and see how it drives. Note that if your wastegate is not ported & you have a free-flowing intake/exhaust, pressure will still creep higher & you will hit fuel cut. Back off the throttle, and see if you can get to redline making low boost.
05-15-13, 05:40 PM
#7
13btRX7driftmissle
While your fuel setup may work, it's not the safest or most fine tuned way to go about running more boost on a stock turbo. FCDs are absolute garbage due to the way they trick the ECU into thinking boost pressure is lower than it really is. This can have a negative effect on fuel and timing calculations.
If you're using a Cosmo 13b or even 20b fuel pump, you'll have plenty of flow at higher pressures (under boost). A 20b pump will probably increase fuel pressure a little more than stock. Pump upgrades are always a wise choice.
When you say you have GSL-SE 680cc injectors, I assume you mean the secondaries only? It would barely idle, and stutter badly down low if you use them as primaries with no fuel tuning. As secondaries, you're netting as much as 12% extra fuel (2460cc / 2200cc) under boost & above 3800 RPM. This is helpful, but some fine tuning would prevent the mixture from getting too rich at partial throttle/low boost.
Something else to consider is that the secondaries don't come on until 3800 RPM, but you can easily make 10+ psi as low as 2500-3000 RPM if you're in a tall gear. Stock primaries can max out before the secondaries come online, which leads to a small lean spot in the middle of the RPM band.
So getting back to your problem, the FCD's job is the fool the ECU and prevent it from cutting fuel to the rear rotor at 8.6 psi. It almost sounds like you are still hitting fuel cut (even though you shouldn't be able to), since peak boost will not be very high in 1st gear. Offhand, I think I usually see 8-9 psi max in datalogs. From 2nd on, load will be higher, and you'll be able to make more pressure. I would suggest turning your boost controller down, or disconnecting it temporarily. Disconnect the FCD, and see how it drives. Note that if your wastegate is not ported & you have a free-flowing intake/exhaust, pressure will still creep higher & you will hit fuel cut. Back off the throttle, and see if you can get to redline making low boost.
If you're using a Cosmo 13b or even 20b fuel pump, you'll have plenty of flow at higher pressures (under boost). A 20b pump will probably increase fuel pressure a little more than stock. Pump upgrades are always a wise choice.
When you say you have GSL-SE 680cc injectors, I assume you mean the secondaries only? It would barely idle, and stutter badly down low if you use them as primaries with no fuel tuning. As secondaries, you're netting as much as 12% extra fuel (2460cc / 2200cc) under boost & above 3800 RPM. This is helpful, but some fine tuning would prevent the mixture from getting too rich at partial throttle/low boost.
Something else to consider is that the secondaries don't come on until 3800 RPM, but you can easily make 10+ psi as low as 2500-3000 RPM if you're in a tall gear. Stock primaries can max out before the secondaries come online, which leads to a small lean spot in the middle of the RPM band.
So getting back to your problem, the FCD's job is the fool the ECU and prevent it from cutting fuel to the rear rotor at 8.6 psi. It almost sounds like you are still hitting fuel cut (even though you shouldn't be able to), since peak boost will not be very high in 1st gear. Offhand, I think I usually see 8-9 psi max in datalogs. From 2nd on, load will be higher, and you'll be able to make more pressure. I would suggest turning your boost controller down, or disconnecting it temporarily. Disconnect the FCD, and see how it drives. Note that if your wastegate is not ported & you have a free-flowing intake/exhaust, pressure will still creep higher & you will hit fuel cut. Back off the throttle, and see if you can get to redline making low boost.
Hi, this is my first post, EVER in this forum. I have a similar set up to the OP,
Ported, 3mm Apex seals, I am running a single exhaust however, with the same issue.
I was drifting this weekend, and the car was running splendidly, until it got to around 205 - 210 degrees. All of the sudden I started hitting a "Wall" of sorts. as if I lost a set of injectors, Because it happened where my secondaries kicked on (3800 rpm lean spot)
So I shut the car off, checked as much as I could without pulling everything apart, and let it cool down. Started it up, same issue.
A fellow rotor fanatic thought I should reset the ECU and see if the problem happened again as s5 stock ecus hold codes...
I disconnected the negative battery, hit the brakes a few times, and restarted the car, and to my amazement it worked!!!
I am running an S4 turbo II ecu, from factory, with a FCD from mazdaspeed. Notice how I said s5 ecus hold codes??? I have an S4.
Car ran great, for a few laps and then it started happening again!!! (once it got a little warm, 200/205/210 ish , it started doing the 4000 rpm Wall/cutout thing.
This time I pulled the FCD to see if it had any effect, it didnt.
reset the ECU without the FCD car ran great, plugged FCD back in, car still ran great.
I dont think its the FCD....
Could it be the Thermo sensor??? Seeing as how my problem started once it got warm this is where I am...
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05-20-13, 01:17 PM
#9
13btRX7driftmissle
Checked the main ground, everything was connected correctly, decided to check my Fuel pump connection as my Fuel pressure regulator gauge was at 0, even when the key was on.
To my dismay, my fuel pump wasnt receiving 12 volts like it should, so I hooked it to a toggle switch, everything is working correctly as of now. No more fuel cut off issue.
Thanks for all of your help!!
To my dismay, my fuel pump wasnt receiving 12 volts like it should, so I hooked it to a toggle switch, everything is working correctly as of now. No more fuel cut off issue.
Thanks for all of your help!!
Last edited by 13btdriftmissle; 05-20-13 at 01:22 PM.
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