555 injectors
02-18-2004, 08:44 AM
#41
If you look around, it can be had for a lot cheaper probably.
Here is one for $226.95:
http://www.carshopinc.com/product_in..._id/40020/2350
Not sure if you're up for Ebay:
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2460731080
Here is one for $226.95:
http://www.carshopinc.com/product_in..._id/40020/2350
Not sure if you're up for Ebay:
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2460731080
02-18-2004, 08:57 AM
#42
Originally Posted by IceY2K1
It isn't nearly as cheap as the Cartech or Vortech FMU you already have, but you might look into a MSD fuel pump booster, http://fuel.atrperformance.com/produ...?products_id=4.
Basically, it just ramps up voltage to your Walbro as boost increases. I've seen the flow differences Walbro 255lph HP pumps makes and it will definitely give you more room.
Just seems cleaner then a FMU, but probably too pricey for most to mess with.
Basically, it just ramps up voltage to your Walbro as boost increases. I've seen the flow differences Walbro 255lph HP pumps makes and it will definitely give you more room.
Just seems cleaner then a FMU, but probably too pricey for most to mess with.
02-18-2004, 09:20 AM
#43
The Stillen b-pipe is only 2 and 3/16ths inner diameter. I know because I have one and I measure it. It's really not big enough for boosted cars. People here seem to recommend 3" exhausts, but everything I've read about exhaust sizing says that 3" is overkill for the kind of hp levels (300-450 at the crank) most of us are making. If it is too big to fully utilize, then the trade off in torque reduction is not worth it, in my opinion. So I'm thinking 2.5" to 2.75" should be just right.
now I spoke to dallas from warpspeed the other day and he said that 3 " was probably overkill. I know, however that mardigras gained over 40whp from going to a 3" exhaust. So how is that overkill isnt he using the exhaust to its potential.
I called flowmaster yesterday and they told me that my current exhaust is actually hindering my spool up. and that I needed a bigger exhaust.
My thoughts were that because the turbo uses the exhaust to make power, then the bigger exhaust is needed more than a Supercharger.
02-18-2004, 10:06 AM
#44
Originally Posted by Redmax
now I spoke to dallas from warpspeed the other day and he said that 3 " was probably overkill. I know, however that mardigras gained over 40whp from going to a 3" exhaust. So how is that overkill isnt he using the exhaust to its potential.
I called flowmaster yesterday and they told me that my current exhaust is actually hindering my spool up. and that I needed a bigger exhaust.
My thoughts were that because the turbo uses the exhaust to make power, then the bigger exhaust is needed more than a Supercharger.
My thoughts were that because the turbo uses the exhaust to make power, then the bigger exhaust is needed more than a Supercharger.
02-18-2004, 10:15 AM
#45
The pressure delta across a turbo determines how efficiently it operates and the engine VE, therefore the less back pressure after the turbine the greater the delta, ie the better.
SC is a different kind of air pump.
SC is a different kind of air pump.
Originally Posted by Redmax
My thoughts were that because the turbo uses the exhaust to make power, then the bigger exhaust is needed more than a Supercharger.
02-19-2004, 02:16 AM
#46
Hmmmnnn...couldn't sleep, so I began thinking about this topic more.
Assuming open-loop operation, WOT, if the MAF is at 100% capacity, using your 0V-5V range, the ECU would set injector pulse width to whatever maximum value is preset in the fuel map, say 8ms. Now we know that the stock injectors will max out before the MAF. So if you put in bigger injectors and change nothing else, your ECU is still only going to send 8ms to the injectors. 8ms on the larger injectors will give us some more fuel, however if you keep increasing airflow, you'll be right back to lean. Basically, with the stock MAF, you're limited to whatever amount of fuel you can get through whatever size injector you run in the pulse width preset window for the MAF at maximum capacity.
I fully understand that a S-AFC modifies the MAF signal the ECU "sees" thus tricking it into adding/subtracting fuel and that you can only simulate the MAF voltage to a certain maximum value, such as 5V, before it's no longer effective.
Now, using the same 8ms pulse width signal from the ECU to the injectors and MAF voltage of 5V, *IF* the eManage is capable of intercepting the 8ms signal and adding additional pulse width, you could get more fuel assuming the injector can be open longer. On a dyno, you then tune the AFR using this additional pulse width value in a 16x16 table by adding/subtracting, so a Z32 MAF and JWT ECU program is unnecessary. Correct? I think so, however I see a *HUGE* flaw. You've now dyno tuned your setup under ONE particular set of weather/pressure/climate conditions. Basically, it's no longer an airflow referenced system. So, if you take this car out and the conditions vary too much, you could run into rich/lean problems. See that?
Ok, we don't want to eliminate the MAF referenced system, so we need to bring the MAF voltage back into range so the ECU can compesate as necessary for the changing environments. Now, do the "MAF hack", so that it's only reading a portion of the actual air flow. This would decrease the MAF voltage back down into the valid operating range, so when you tune the car on a dyno using the eManage and bigger injectors as above, you still have room for the MAF referenced system to work.
The biggest catch I see in this "theory" is how the ECU will react in closed-loop operation.
Assuming open-loop operation, WOT, if the MAF is at 100% capacity, using your 0V-5V range, the ECU would set injector pulse width to whatever maximum value is preset in the fuel map, say 8ms. Now we know that the stock injectors will max out before the MAF. So if you put in bigger injectors and change nothing else, your ECU is still only going to send 8ms to the injectors. 8ms on the larger injectors will give us some more fuel, however if you keep increasing airflow, you'll be right back to lean. Basically, with the stock MAF, you're limited to whatever amount of fuel you can get through whatever size injector you run in the pulse width preset window for the MAF at maximum capacity.
I fully understand that a S-AFC modifies the MAF signal the ECU "sees" thus tricking it into adding/subtracting fuel and that you can only simulate the MAF voltage to a certain maximum value, such as 5V, before it's no longer effective.
Now, using the same 8ms pulse width signal from the ECU to the injectors and MAF voltage of 5V, *IF* the eManage is capable of intercepting the 8ms signal and adding additional pulse width, you could get more fuel assuming the injector can be open longer. On a dyno, you then tune the AFR using this additional pulse width value in a 16x16 table by adding/subtracting, so a Z32 MAF and JWT ECU program is unnecessary. Correct? I think so, however I see a *HUGE* flaw. You've now dyno tuned your setup under ONE particular set of weather/pressure/climate conditions. Basically, it's no longer an airflow referenced system. So, if you take this car out and the conditions vary too much, you could run into rich/lean problems. See that?
Ok, we don't want to eliminate the MAF referenced system, so we need to bring the MAF voltage back into range so the ECU can compesate as necessary for the changing environments. Now, do the "MAF hack", so that it's only reading a portion of the actual air flow. This would decrease the MAF voltage back down into the valid operating range, so when you tune the car on a dyno using the eManage and bigger injectors as above, you still have room for the MAF referenced system to work.
The biggest catch I see in this "theory" is how the ECU will react in closed-loop operation.
Originally Posted by Stephen Max
Yes, it could. The way Nissan seems to do things is to provide injectors that are the limiting factor, that is, the injectors will run out of fuel delivering capacity before the maf reaches its saturation point. So if you go with larger injectors, it is possible to hit the maf limit first. Whether or not that results in an overrich mixture depends on how much air is being pumped into the engine. It could be overrich, or just right, or still not enough. But with 555 cc/min injectors you will most likely be overrich at 100% DC, so you will need to lean out with the AFC.
You're right, pulse width and duty cycle are different entities, but they are very intimately related. Duty cycle is just the time that an injector is on compared to the total time available. So as rpm increases, available time decreases and duty cycle will increase even if the pulse width stays the same. The AFC just alters the maf signal either up or down, and then sends it on to the ecu. The ecu adjusts injector pulse width based on what it thinks the maf is measuring. But the AFC can not send more than a 5V signal to the ecu, no matter what, since that is the maximum voltage that the ecu can accept. If the maf is saturated at high rpm when the injector pulse width is already at 100% DC, then the AFC can not be used to increase pulse width. But with big injectors this won't be your problem. Rather, you will probably need to lean out the entire rpm range with the AFC. But again, it also depends on how much charge air the engine is getting.
With a 3" exhaust you will be somewhere between 320 and 350, I would guess.
You're right, pulse width and duty cycle are different entities, but they are very intimately related. Duty cycle is just the time that an injector is on compared to the total time available. So as rpm increases, available time decreases and duty cycle will increase even if the pulse width stays the same. The AFC just alters the maf signal either up or down, and then sends it on to the ecu. The ecu adjusts injector pulse width based on what it thinks the maf is measuring. But the AFC can not send more than a 5V signal to the ecu, no matter what, since that is the maximum voltage that the ecu can accept. If the maf is saturated at high rpm when the injector pulse width is already at 100% DC, then the AFC can not be used to increase pulse width. But with big injectors this won't be your problem. Rather, you will probably need to lean out the entire rpm range with the AFC. But again, it also depends on how much charge air the engine is getting.
With a 3" exhaust you will be somewhere between 320 and 350, I would guess.
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