Fuel Cut with only Intake and Cat-Back?
01-26-02, 01:56 AM
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Fuel Cut with only Intake and Cat-Back?
Hi Folks,
Well the tips of my tailpipes are starting to look a little crusty, so I'm thinking of installing a 65mm (2.5") dual A'PEXi N-1 cat-back exhaust.
I currently have an intake as my only mod.
My question is: With only an intake and cat-back exhaust, will the boost rise high enough to risk hitting boost cut?
I don't plan on making any other mods until I learn a WHOLE LOT more about my TII, so I'm wondering if I need an FCD at this point.
Or do I need to either rewire/replace the fuel pump and get larger fuel injectors?
I did a SEARCH on this subject but couldn't really get a definitive answer on fuel cut with >just< an intake and exhaust since most people had a lot more mods (turbo-back exhaust, etc...).
Thanks in advance!
Well the tips of my tailpipes are starting to look a little crusty, so I'm thinking of installing a 65mm (2.5") dual A'PEXi N-1 cat-back exhaust.
I currently have an intake as my only mod.
My question is: With only an intake and cat-back exhaust, will the boost rise high enough to risk hitting boost cut?
I don't plan on making any other mods until I learn a WHOLE LOT more about my TII, so I'm wondering if I need an FCD at this point.
Or do I need to either rewire/replace the fuel pump and get larger fuel injectors?
I did a SEARCH on this subject but couldn't really get a definitive answer on fuel cut with >just< an intake and exhaust since most people had a lot more mods (turbo-back exhaust, etc...).
Thanks in advance!
01-26-02, 03:26 AM
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Well with the RB Turbo Back exhaust (which they are redesigning at the moment) you get an extra 4 to 5 boost increase, so I'm thinking the cat back might be close to it but maybe not close enough. I would suggest getting getting a Boost meter to see what kind of boost you would be getting, and then determine if its close enough to get a FCD.
BTW I have heard that FCD are not a good thing due to them making your car run lean.
Waht are the Pros and Cons of an FCD
what other reliability mods should one have before installing a FCD.
I'mgeting a TurboII some time in the near future, so I hwought I might as well know this stuff while the topic is up
BTW I have heard that FCD are not a good thing due to them making your car run lean.
Waht are the Pros and Cons of an FCD
what other reliability mods should one have before installing a FCD.
I'mgeting a TurboII some time in the near future, so I hwought I might as well know this stuff while the topic is up
01-26-02, 09:03 AM
#3
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Depends on how bad you cats are clogged in my experience. I installed a Borla cat back, and it didn't make much difference. I also use a K&N in the stock box, just can't justify the $200ish for something else-- not to mention introduce warmer air. I know that they would be less restrictive, and I could add a cold air box, but that's not your question.
After these 2 mods, I did not hit the boost cut. After replacing the cat (see sig) and downpipe, hit fuel cut BIG time. Built my own FCD which took care of that. Added the SAFC to help get the mixture right, still need to rewire the fuel pump. I don't think I'll replace it for the mods I plan to do, but a re-wire is one of the suggestions that's pretty popular here.
Greg O.
After these 2 mods, I did not hit the boost cut. After replacing the cat (see sig) and downpipe, hit fuel cut BIG time. Built my own FCD which took care of that. Added the SAFC to help get the mixture right, still need to rewire the fuel pump. I don't think I'll replace it for the mods I plan to do, but a re-wire is one of the suggestions that's pretty popular here.
Greg O.
01-26-02, 09:25 AM
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My 87turboii, with the Mazdatrix item 16207 http://www.mazdatrix.com/r-extii.htm which is a 2 and 1/2 inch downpipe with a presilencer only, gave me just a small hair below 8psi. That was with the stock intake and stock mufflers.
So I had 8psi with the above. One day I took my K and N off my 87 N/A and put it on the turbo. I now can touch 10 psi and hit fuel cut where I was not touching fuel cut before. I find this setup very controlable because the boost goes right to 8, lags for a moment and edges to 10. Plenty of time to lift off the throttle before fuel cut, which seems to happen somewhere b/t 9 and 1/2 and 10. Fuel cut seems to be dependent on how aggressive I am at the time as to when it cuts.
So I did not answer your question, but I FEEL like you will not hit fuel cut. I think you'll come close to 8, and real life fuel cut seems to be around 9 and 1/2 to 10. Used a Autometer boost gauge.
So I had 8psi with the above. One day I took my K and N off my 87 N/A and put it on the turbo. I now can touch 10 psi and hit fuel cut where I was not touching fuel cut before. I find this setup very controlable because the boost goes right to 8, lags for a moment and edges to 10. Plenty of time to lift off the throttle before fuel cut, which seems to happen somewhere b/t 9 and 1/2 and 10. Fuel cut seems to be dependent on how aggressive I am at the time as to when it cuts.
So I did not answer your question, but I FEEL like you will not hit fuel cut. I think you'll come close to 8, and real life fuel cut seems to be around 9 and 1/2 to 10. Used a Autometer boost gauge.
01-26-02, 11:56 AM
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So I'm thinking that I should either make/buy the FCD and do the fuel pump rewire (just as insurance) before installing the cat-back... whaddya guys think?
I know there is a FAQ on the FCD, does anyone know the URL of a FAQ on rewiring the stock fuel pump?
I know there is a FAQ on the FCD, does anyone know the URL of a FAQ on rewiring the stock fuel pump?
01-26-02, 12:08 PM
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87 TII, I run a bonez cold air intake, downpipe and catback and I was boosting right at the cut off point. About 6.5k rpm when the boost was beginning to max out the computer would start cutting the fuel. It was livable because it didn't happen all the time and would only happen about the time I was going to shift. I later installed an N1 catback and a cat replacement straight pipe and did need to install the FCD.
About leaning out with the FCD... Yes, My fuel pump begins to loose pressure at 7.5k rpm so thats the limit of the stock fuel pump with using the FCD and a free flowing in and out system. Any more boost and I will have to replace the fuel pump. I use no boost controler, just free flowing in and out gives about a 2 lbs increase in boost.
About leaning out with the FCD... Yes, My fuel pump begins to loose pressure at 7.5k rpm so thats the limit of the stock fuel pump with using the FCD and a free flowing in and out system. Any more boost and I will have to replace the fuel pump. I use no boost controler, just free flowing in and out gives about a 2 lbs increase in boost.
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