FAST wideband on, AFR.....off
05-20-2010, 06:21 PM
#1
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FAST wideband on, AFR.....off
So I got the FAST Wideband installed. Ever since I swapped to the Tri-Y's and the Dr. Gas x pipe the tune has been out. It was never spot on to begin with, but ran well.
Anyway, the idle circuit is now too lean, so I'll have to go up on the IFR to bring the cruise AFR back down....which is around 15:1 and has a very slight lean hesitation/misfire to it. WOT is interesting....at around 2,000-2,500 it's a bit under 10.5:1 and sputters a bit, and by 6,000rpm comes up to around 12.8-13:1 which is about where it should be. So it looks like I'ma have to order screw in restrictors for the Quick Fuel carb and play with the emulsion circuits. Which is of course the reason I got their carb....specifically to deal with situations like this.
As far as the FAST unit, it's their analog wideband O2 setup. The gauge is nice, and backlit, so it looks nice when the lights are on. Typical excellent FAST quality, even the O2 sensor came with anti-sieze on the threads and the electrical connectors has dialectric grease in them already. The control module is encased in a rubberized type coating for protection with mounting holes to screw it down, and all the wires came pre stripped and ready to be installed.
Anyway, the idle circuit is now too lean, so I'll have to go up on the IFR to bring the cruise AFR back down....which is around 15:1 and has a very slight lean hesitation/misfire to it. WOT is interesting....at around 2,000-2,500 it's a bit under 10.5:1 and sputters a bit, and by 6,000rpm comes up to around 12.8-13:1 which is about where it should be. So it looks like I'ma have to order screw in restrictors for the Quick Fuel carb and play with the emulsion circuits. Which is of course the reason I got their carb....specifically to deal with situations like this.
As far as the FAST unit, it's their analog wideband O2 setup. The gauge is nice, and backlit, so it looks nice when the lights are on. Typical excellent FAST quality, even the O2 sensor came with anti-sieze on the threads and the electrical connectors has dialectric grease in them already. The control module is encased in a rubberized type coating for protection with mounting holes to screw it down, and all the wires came pre stripped and ready to be installed.
05-20-2010, 10:06 PM
#2
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Ask this guy (Brain Macy, brian@brianmacy.com) He works for FAST, teaches classes for them and flies all over tuning cars.
05-20-2010, 10:43 PM
#3
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I can tune mine, I just have to call up Quick Fuel tomorrow and order the parts I need for the carb. FAST is definitely one of the places to call for advice though, those guys have systems on some of the fastest EFI cars out there. My emulsion package in the carb is a generic one though, and it ended up being off by quite a bit for my setup. Like I said, that's why I got the Quick Fuel, the metering block is already set up for screw in emulsion, I just need to drill the circuit out and install the proper restrictor.
05-21-2010, 04:37 AM
#4
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well what are the chances they'll sell you an EFI setup?
sorry for the stupid question, but wouldn't turning out the idle mixture screws a bit (1/8 turn each) already sort out the lean cruise? I know they're used for idle only, but should have effect as well on very low throttle cruise.
i always thought the IFR adds air to the mixture, so if you are too lean, wouldn't you have to go down on the IFR (to restrict air)?
just trying to figure this out ....
I would love one of those SS-650-AN carbs of theirs. but have to save some money first ...
i came across a QF metering block from a 650 and was thinking to buy for my demon. but i don't know if it'll fit, so I'll probably leave it off.
sorry for the stupid question, but wouldn't turning out the idle mixture screws a bit (1/8 turn each) already sort out the lean cruise? I know they're used for idle only, but should have effect as well on very low throttle cruise.
i always thought the IFR adds air to the mixture, so if you are too lean, wouldn't you have to go down on the IFR (to restrict air)?
just trying to figure this out ....
I would love one of those SS-650-AN carbs of theirs. but have to save some money first ...
i came across a QF metering block from a 650 and was thinking to buy for my demon. but i don't know if it'll fit, so I'll probably leave it off.
05-21-2010, 04:40 AM
#5
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ignore. just read:
Fuel enters the idle circuit through the main jet and then travels through an idle-feed restrictor and into the idle-feed well.
i confused it with the idle air bleed. but ya it's nice that you don't have to do any drilling with those carbs :-)
Fuel enters the idle circuit through the main jet and then travels through an idle-feed restrictor and into the idle-feed well.
i confused it with the idle air bleed. but ya it's nice that you don't have to do any drilling with those carbs :-)
05-21-2010, 11:37 AM
#7
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Interesting. Good to hear about the FAST gauge. I have been using a temporary LM2 for 18 months now, so I have been thinking of installing something permanent. I saw their stuff in a magazine recently and wondered how good the quality was.
I have been told that while an H or X pipe will not show much difference on a dyno, it will affect the ease of flow of the exhaust. In a high end motor, the exhaust and exhaust pulses can become a bottleneck because the left and right band do not switch back an forth (i.e. in a 351W, 1-8-4-5-6-2-7-3 firing order, 5&6 fire sequentially) which can cause a back up on the drive side exhaust flow. I can see my driverside AFR lean out at WOT because of this...even with 3" mandrel exhaust. I am eating my words and putting in an H pipe to help with this issue. I also suspect that my manifold does not flow evenly on all ports, which is why I hope to receive my Dr. J's Performance Air Gap today and install it to see what the AFR does.
Did you go with just a single O2 sensor or dual?
I have been told that while an H or X pipe will not show much difference on a dyno, it will affect the ease of flow of the exhaust. In a high end motor, the exhaust and exhaust pulses can become a bottleneck because the left and right band do not switch back an forth (i.e. in a 351W, 1-8-4-5-6-2-7-3 firing order, 5&6 fire sequentially) which can cause a back up on the drive side exhaust flow. I can see my driverside AFR lean out at WOT because of this...even with 3" mandrel exhaust. I am eating my words and putting in an H pipe to help with this issue. I also suspect that my manifold does not flow evenly on all ports, which is why I hope to receive my Dr. J's Performance Air Gap today and install it to see what the AFR does.
Did you go with just a single O2 sensor or dual?
05-21-2010, 02:24 PM
#8
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Lol, point taken. They certainly know their stuff, that's for sure. They even manufacture carburetor jets now.
I've been looking at their EZ EFI, but it's out of my price range right now.
And the fast analog kit is a single gauge single O2 setup. The digital is available in single or dual sensor. I installed my sensor in the driver side bank. Dual plane intakes are 180* runners so half the cylinders on each side of the engine receive air from the larger plenum and half from the smaller. Meaning half are going to be leaner(or richer) than the other half. So either bank will work just as well to give a good average AFR.
And yeah, the IFR is basically the jet for the idle circuit. You don't want to use the idle needle to adjust cruise AFR, only idle. The way it works is fuel enters the main well through the main jet, and some goes through a bypass into the main idle well and gets pulled up the well by intake vacuum(actually pushed by ATM pressure) and goes through the IFR at the top of the main idle well(on a Quick Fuel, some carbs put the IFR at the bottom entering the main idle well). After the fuel passes through the IFR it mixes with air from the low speed air(or idle) bleed and creates an emulsion that falls down into the main idle emulsion well, at the bottom of that well is the output for the transfer slot as well as the idle mix screw.
Both the transfer slot AND idle mix screw get the fuel from the same well, and a bit of the transfer slot is uncovered at idle, so some idle mix comes from the transfer slot and the rest from the mix screw. You use the mix screw to increase or decrease the fuel available during idle. Simply adding more idle fuel to get a richer cruise AFR MAY give you the correct cruise AFR, but will lead to a rich idle. Cruise AFR should always be set through the IFR and LSAB....it's basically the same as setting WOT through the main jet and HSAB.
It's also a throttle response issue too. The correct cruise AFR comes from the correct LSAB and IFR setting, and as you just start to crack the throttle open you uncover the transfer slot. That part of the idle circuit is sometimes referred to as the transition circuit. As the transfer slot is getting uncovered but intake vacuum is still high, it yanks fuel out of the main idle emulsion well. You need to have the right response and AFR in that circuit to avoid having a quick hiccup in throttle response before the fuel from the pump shot gets into the intake. That's why cruise AFR needs to be set via the IFR and LSAB, because it also results in the proper response and AFR during initial throttle tip in.
Idle circuits are responsible for the vast majority of carburetor related drivability issues(non ignition related).
As far as the exhaust system....pooey on 90* V8's. The 90* crankshaft configuration(crankpins arrayed 90* apart in the typical American V8 layout) is easier to balance, but wreaks havoc with the exhaust system. It results in 2 cylinders in EACH BANK that fire one right after the other. That means there are 2 cylinders exhausting into the same header 90* apart, so while one is still shoving a huge amount of exhaust gas out, another begins blowdown. It results in exhaust gas backing up in the collector. Not to mention the exhaust pulse firing in each header is all oddball, some cylinders in each header fire 90* apart, some 180*, some 270*. It makes pulse wave tuning have a severely limited effectiveness in addition to the "clogged" exhaust problems.
90* American V8 exhaust system tuning is really just an exercise in limiting power loss from extremely poor exhaust pulse timing. Formula 1 V8's and all Ferrari V8's use a single plane 180* crankshaft. It's basically like a 4 cylinder crankshaft but in a V8 where 2 rods are attached to the same crankpin like any other V8. They're just arrayed 180* apart instead of 90*. Much more difficult to balance but it makes the exhaust system function properly. It causes the firing order to fire each cylinder bank to bank, 1 left...1 right...1 left...1 right and so on. That means that each cylinder in 1 bank fires exactly 180* apart from all the others....both banks fire their cylinders 180* apart, and each bank is phased 90* apart from the other bank. So the firing order for exhaust pulses in a 180* crankshaft engine is 180-180-180-180(just like a 4 cylinder)....as opposed to a 90*(American) V8 exhaust bank that fires 90-180-270-180(or something similar depending on the make and bank). That's what the Tri-Y tries to solve....by separating runners out, it creates a 450-270 firing order at the end of each secondary runner.....better than nothing, but still not optimal. It's what makes American V8's sound American, and makes F1 and Ferraris sound like F1 and Ferraris.
Balance pipes try to fix that, and balance pipes combined with Tri-Y's are as close as you'll get without using crossover headers(which generally require a chassis specifically designed for them).
I've been looking at their EZ EFI, but it's out of my price range right now.
And the fast analog kit is a single gauge single O2 setup. The digital is available in single or dual sensor. I installed my sensor in the driver side bank. Dual plane intakes are 180* runners so half the cylinders on each side of the engine receive air from the larger plenum and half from the smaller. Meaning half are going to be leaner(or richer) than the other half. So either bank will work just as well to give a good average AFR.
And yeah, the IFR is basically the jet for the idle circuit. You don't want to use the idle needle to adjust cruise AFR, only idle. The way it works is fuel enters the main well through the main jet, and some goes through a bypass into the main idle well and gets pulled up the well by intake vacuum(actually pushed by ATM pressure) and goes through the IFR at the top of the main idle well(on a Quick Fuel, some carbs put the IFR at the bottom entering the main idle well). After the fuel passes through the IFR it mixes with air from the low speed air(or idle) bleed and creates an emulsion that falls down into the main idle emulsion well, at the bottom of that well is the output for the transfer slot as well as the idle mix screw.
Both the transfer slot AND idle mix screw get the fuel from the same well, and a bit of the transfer slot is uncovered at idle, so some idle mix comes from the transfer slot and the rest from the mix screw. You use the mix screw to increase or decrease the fuel available during idle. Simply adding more idle fuel to get a richer cruise AFR MAY give you the correct cruise AFR, but will lead to a rich idle. Cruise AFR should always be set through the IFR and LSAB....it's basically the same as setting WOT through the main jet and HSAB.
It's also a throttle response issue too. The correct cruise AFR comes from the correct LSAB and IFR setting, and as you just start to crack the throttle open you uncover the transfer slot. That part of the idle circuit is sometimes referred to as the transition circuit. As the transfer slot is getting uncovered but intake vacuum is still high, it yanks fuel out of the main idle emulsion well. You need to have the right response and AFR in that circuit to avoid having a quick hiccup in throttle response before the fuel from the pump shot gets into the intake. That's why cruise AFR needs to be set via the IFR and LSAB, because it also results in the proper response and AFR during initial throttle tip in.
Idle circuits are responsible for the vast majority of carburetor related drivability issues(non ignition related).
As far as the exhaust system....pooey on 90* V8's. The 90* crankshaft configuration(crankpins arrayed 90* apart in the typical American V8 layout) is easier to balance, but wreaks havoc with the exhaust system. It results in 2 cylinders in EACH BANK that fire one right after the other. That means there are 2 cylinders exhausting into the same header 90* apart, so while one is still shoving a huge amount of exhaust gas out, another begins blowdown. It results in exhaust gas backing up in the collector. Not to mention the exhaust pulse firing in each header is all oddball, some cylinders in each header fire 90* apart, some 180*, some 270*. It makes pulse wave tuning have a severely limited effectiveness in addition to the "clogged" exhaust problems.
90* American V8 exhaust system tuning is really just an exercise in limiting power loss from extremely poor exhaust pulse timing. Formula 1 V8's and all Ferrari V8's use a single plane 180* crankshaft. It's basically like a 4 cylinder crankshaft but in a V8 where 2 rods are attached to the same crankpin like any other V8. They're just arrayed 180* apart instead of 90*. Much more difficult to balance but it makes the exhaust system function properly. It causes the firing order to fire each cylinder bank to bank, 1 left...1 right...1 left...1 right and so on. That means that each cylinder in 1 bank fires exactly 180* apart from all the others....both banks fire their cylinders 180* apart, and each bank is phased 90* apart from the other bank. So the firing order for exhaust pulses in a 180* crankshaft engine is 180-180-180-180(just like a 4 cylinder)....as opposed to a 90*(American) V8 exhaust bank that fires 90-180-270-180(or something similar depending on the make and bank). That's what the Tri-Y tries to solve....by separating runners out, it creates a 450-270 firing order at the end of each secondary runner.....better than nothing, but still not optimal. It's what makes American V8's sound American, and makes F1 and Ferraris sound like F1 and Ferraris.
Balance pipes try to fix that, and balance pipes combined with Tri-Y's are as close as you'll get without using crossover headers(which generally require a chassis specifically designed for them).
05-21-2010, 03:09 PM
#9
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well i never knew the ferrari V8s were boxers. another lesson learned.
thanks a million for you long desciption about the relation between the wells, idle, transfer and the restrictors and bleeds. I have to pull the metering block again to follow all this. quite sure my IFR is top as well. i always knew what the transfer slot was but even though i adjust my throttle plate for square port, i never thought of the fact it's used during idle as well.
anyway, i'm still trying to soak all this up. this weekend my crane distributor is going in and after that I plan a long tuning session with my A/F as well. unfortunately the carb (it's an older demon) doesn't have the niceties of restrictors and bleeds. And I'm most certainly not taking a drill to it to increase anything ;-)
would you have any info if QF metering blocks will fit holley/demon?
thanks a million for you long desciption about the relation between the wells, idle, transfer and the restrictors and bleeds. I have to pull the metering block again to follow all this. quite sure my IFR is top as well. i always knew what the transfer slot was but even though i adjust my throttle plate for square port, i never thought of the fact it's used during idle as well.
anyway, i'm still trying to soak all this up. this weekend my crane distributor is going in and after that I plan a long tuning session with my A/F as well. unfortunately the carb (it's an older demon) doesn't have the niceties of restrictors and bleeds. And I'm most certainly not taking a drill to it to increase anything ;-)
would you have any info if QF metering blocks will fit holley/demon?
05-21-2010, 04:38 PM
#10
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QFT sells metering blocks that fit Holleys etc. Call them and ask which ones would fit your carb. If you're running the Demon though, I wouldn't change the metering blocks unless your fuel curve has to be adjusted via the emulsion package. And trying to see all that in the metering block is hard, some of it is inside the block. Those little brass plugs on the top of the metering block are actually plugging the holes left when the main fuel well and idle fuel well are machined out, or the die is removed.
And Ferraris aren't boxers. A boxer is an engine where the cylinders are opposed to one another, arrayed 180* apart. A Ferrari V8 is a 90* V8 block with a 180* crankshaft. So the cylinders are arrayed 90* apart but the crankpins are 180* apart. Think of it sort of like an American V8 engine with a 4 cylinder crankshaft inside it. Same thing with an F1 engine, 90* block with 180* crank. It makes for a difficult to balance assembly, but a more efficient and highly responsive to tuning exhaust system.
And Ferraris aren't boxers. A boxer is an engine where the cylinders are opposed to one another, arrayed 180* apart. A Ferrari V8 is a 90* V8 block with a 180* crankshaft. So the cylinders are arrayed 90* apart but the crankpins are 180* apart. Think of it sort of like an American V8 engine with a 4 cylinder crankshaft inside it. Same thing with an F1 engine, 90* block with 180* crank. It makes for a difficult to balance assembly, but a more efficient and highly responsive to tuning exhaust system.
