LS-1 MAF translator vs ARC-2/ VPC

[kutschca]

yeah, sorry I wasn't clear on that. I plan on upgrading my fuel system with the pump and regulator around the same time as getting the MAFT.

 

[P8ntBalla]

does anyone know of a 2.5" gm maf? i would imagine that in a blow through setup that that would flow just fine if its on 2.5" pipe, not to mention that it would be easier to hook up.

 

[GreenGSX]

Originally posted by P8ntBalla
does anyone know of a 2.5" gm maf? i would imagine that in a blow through setup that that would flow just fine if its on 2.5" pipe, not to mention that it would be easier to hook up.

The inside diameter of the 3" GM MAF is closer to 2.5" so going to a smaller MAF wouldn't make much sense.

Tim

 

[JayHass]

Originally posted by P8ntBalla
does anyone know of a 2.5" gm maf? i would imagine that in a blow through setup that that would flow just fine if its on 2.5" pipe, not to mention that it would be easier to hook up.

I've seen a lot of posts like this and it needs to be adressed clearly.

Guys, you can't just swap in MAF's at will. A MAF has a map to it just like a turbo compressor wheel does. Basically what it says is "at X airflow I put out Y voltage."

The boxes are built for the 3.5 and 3" applications stated. Putting on another MAF or "hacking" or "porting" even the above applications throws the readings off.

When I first learned the DSM community was "hacking" MAF's to tune without fuel controls or data acuisition I almost crapped myself and couldn't believe it until I saw it first hand.

 

[natedogg]

Originally posted by JayHass


Also don't forget guys...when pressure goes up fuel pump flow generally GOES DOWN.

I've seen this before and wondered where this assumption came from.

Pressure and flow can be treated similar to electrical voltage and current. Similar to voltage, pressure is a potential difference between 2 mediums. Once you supply a path between these mediums (electrically this would be a wire, fluidly this would be a pipe) you have flow analagous to electric current. If you increase the potential difference (aka. increase the pressure or voltage) across the path of a set resistance electrically or pipe diameter fluidly, you also increase the current or flow. Its a simple linear ratio. I'm not sure what the fluidic equation is but the electrical equation is Ohm's law V=IR or I=V/R. Where V=voltage, I=current and R=resistance. As you can easily see from the equation, if you increase the current across a set resistance you also increase the voltage. Likewise, if you increase the voltage across a set resistance, you increase the current.

You explained that increasing the fuel pressure increased the flow of your injectors. Now you are saying that increasing the pressure of the fuel pump, decreases its flow. Now, I'm not saying you're wrong. I honestly don't know that much about fuel pumps beyond what I've read on RRE's and dsm-performance's websites. I'm just trying to use my knowledge of electrical engineering to make sense of this statement. Perhaps you could explain it to me a little better.

 

[JayHass]

Originally posted by natedogg


I've seen this before and wondered where this assumption came from.

Well first off, rest assured it's not an assumption. Flow tests have been done and that is the result.

We also have a Walbro engineer on the SE-R mailing list who gives lots of great fuel pump information. (Yes the SE-R community has a lot of wacked engineers from Garrett, Nissan, Walbro etc etc )

I'm just trying to use my knowledge of electrical engineering to make sense of this statement. Perhaps you could explain it to me a little better.

No problem, I hope I can explain it. Think of the pressure as resistance to the pump. The more pressure, the greater the resistance which limits flow proportionatly.

You can actually STOP the fuel flow with enough pressure.

 

[natedogg]

Originally posted by JayHass

No problem, I hope I can explain it. Think of the pressure as resistance to the pump. The more pressure, the greater the resistance which limits flow proportionatly.

You can actually STOP the fuel flow with enough pressure.

Hmm...this still doesn't make sense to me. As long as the fluid has a path to follow how can you stop the flow. I could possibly see hitting a peak flow and staying there just because the lines aren't capable of flowing more fluid.

I look at our turbo systems for reference. The turbo being analagous to the fuel pump. Increasing the boost pressure increases the effective flow of the turbocharger. This allows us to flow more air and of course cram more air into less space. Now we can outflow certain bottlenecks if they are not big enough, perhaps meaning we hit a peak flow and stay there, but it seems to me the flow would never actually decrease beyond that point. It certainly doesn't stop flowing.

Am I missing something here? I'm not trying to be a PITA, but I'm just having trouble wrapping my mind around this concept.

 

[JayHass]

Originally posted by natedogg
I'm not trying to be a PITA, but I'm just having trouble wrapping my mind around this concept.

Think of it this way. The turbo compressor has a long pipe attached to the outlet and is always at max *flow*, and pressure is controlled by a restriction at the end. The smaller the restriction the more pressure. Now picture there only being so much energy to spin the compressor. As the restriction gets smaller, pressure in the tube goes up and "load" on the compressor goes up. At a point the pressure will overcome the energy available to turn the compressor.

That's what a fuel pump is, and why at higher pressures the flow goes down.

 

[QuickSilverGSX9]

Thanks for the replies everyone. I think I'm starting to pick some of the information up. However, the past two nights I've came across a problem. I have the MAFT, and have it zero'd out across the board. So, I'm not enrichening anything, or leaning anything out. I also have it set for 0 on the base, which is for stock 450's, which is what I have.

Anyways, the past two nights I've been hitting fuel cut. Or atleast feels like fuel cut. I checked my pocketlogger and at varying RPM's you can see them climbing, then all of a sudden dip, and a decent amount of knock appear (however it is always after 4500, it varys after that point). This is the weird thing, I've been playing with the settings on the MAFT prior to this happening, both on the rich and lean side of the WOT setting. I only started hitting fuel cut at 5% rich at WOT, and then neither rich or lean at WOT. Now, before you say I need to lean things out, I was at 10% richer at WOT before hand, and no fuel cut. Also, I'm not getting any boost creep, atleast the gauge isn't showing me any. It has gotten a bit colder out, so that is a factor, but I don't understand how I can hit fuel cut at say 4900 rpms but not before, because obviously I'm hitting full boost far before that point.

Anyone think they could help me out on this on? I'm still doing more testing, I just don't know what would cause this, and I would like to go back to the track on friday, but there will be no point if I keep hitting fuel cut. Thanks all.
-Bill

 

[eclipse2via]

It's the total airflow not the boost that is causing fuel cut. In colder denser air you will only hit it that much quicker. What are your duty cycles like? I saw increase of 5-10% when I put the MAF on, leaving me no choice but to upgrade my injectors. I was seeing fuel cut every time I went WOT and I never had fuel cut before upgrading, just overrun.
Scott

Just a thought. Are you getting overrun or fuel cut?

 

[natedogg]

Originally posted by JayHass


Think of it this way. The turbo compressor has a long pipe attached to the outlet and is always at max *flow*, and pressure is controlled by a restriction at the end. The smaller the restriction the more pressure. Now picture there only being so much energy to spin the compressor. As the restriction gets smaller, pressure in the tube goes up and "load" on the compressor goes up. At a point the pressure will overcome the energy available to turn the compressor.

That's what a fuel pump is, and why at higher pressures the flow goes down.

Ahh yes. I can see how the high outlet pressure could overload the pump itself, effectively stopping it from pumping. Meaning that the flow through the fuel pump itself is 0. I can also see how a greater pressure on the outlet side of the fuel pump would make the fuel pump flow less because it has a higher outlet pressure to overcome. I guess I was looking at the fuel system as a whole rather than just the fuel pump itself.

Please allow me to explain where I'm coming from.

If you look at the fuel system as a whole, the flow never really slows down unless the fuel pump quits because the increasing pressure along a path of constant resistance will result in an increased flow, right?

Perhaps an example of what I'm trying to get at. Let's look at an air compressor. It pumps to an internally set pressure say 140 psi. Cool. Now we can change the outlet pressure with a knob connected to an outlet valve. If I turn this knob to 40 psi outlet pressure and inflate a tire to 40 psi, the pressure difference is 0 so there is no more flow. But if I increase the outlet pressure to 90 psi, the air will keep flowing until the tire blows because the pressure difference is allowing it.

This is the same case as a fuel system because the fuel pump side will always be at a higher pressure than the fuel tank return side (lets ignore injectors right now for the sake of simplicity). Now if we put a higher pressure pump in the system, we get an overall greater flow in the entire system because the fuel tank return side is still only atmospheric pressure (fuel system outlet pressure) and the fuel lines themselves are the same size, therefore offering no extra resistance. The fuel pump itself may actually reach a point where it can barely increase the pressure, therefore it barely flows anymore fuel through itself, but the fuel system as a whole is flowing faster because it wants to equalize its high pressure with the low atmospheric pressure by getting rid of all the fuel in the system. But the moment it gets rid of some the pump puts more back in.

If increasing the fuel pressure actually resulted in less fuel flow throughout the entire system, then I should jack my fuel pressure up as high as possible because I will be getting awesome gas mileage since I won't be flowing nearly as much fuel. j/k :laugh:

Thanks for the explanation Jay. I think most of my explanation was basically to help me think my way through it, but hopefully someone will be able to take something from this discussion.

 

[QuickSilverGSX9]

It might very well be overrun. Like I said, it felt like fuel cut, but, I didn't have a pocketlogger to log the outcome before. So, this is probably a pretty stupid question, but I thought I'd ask, what's the difference between overrun and fuel cut? Whatever the differences, aren't the results the same? The computer can't provide enough fuel for the amount of air entering the cylinders, so it I guess, cuts the injectors, or what? I guess this explains why when I turned down the boost to 14lbs I hit the same overrun problem, but it just simply happened later? This may not be true, because the overrun point did occur randomly to a point, but the last time it did happen later than any other time.

Anyways, I guess injectors are definately my next purchase, since it seems I need them more than anything else. I was going to go with a supra SMIC, and UIC pipping, but oh well. I do plan on running a 20g, most likely a SB20g, and (still leaning this way) a Supra SMIC. What would be large enough, injector wise, 660's? Can anyone PM me for a place I can get good prices on these, possibly? Thanks for all the input guys.
-Bill

 

[bottledbird68]

OK, you guys finally sold me, I placed my order today. Now I'm off to order a pocketlogger so I can keep track of what's going on. One question though, since I'm getting a pocketlogger would an EGT gauge really be needed, and if so, why? Or does the pocketlogger provide all the info I'll need?

 

[nine5raptor]

go with just the pocketlogger. if you decide later that it isn't enough, look into a homemade wideband setup instead of an egt.

 

[Tallen]

forget pocketlogger
buy a palm, an $85 cable form multiplex engineering, and download the free tunerstein palm software

 

[bottledbird68]

Oops, I reposted this in a separate thread because I was having computer issues and didn't think it went through But, since I have your attention, I thought the the tunerstein software wasn't as good as the pocketlogger?? What exactly is the difference? Please tell me either here or in my other thread, I'll check both. Thanks

 

[Tallen]

for the price...tunerstein rocks. logs, plays back, does codes. i have used pocketlogger and its a ripoff IMO

 

[eclipse2via]

For a 1G I highly recommend the updated version of Pocketlogger. The split screen realtime Gauge feature is the best. Plus it has continued factory support, I think tunerstein is no longer being supported. Scott

 

[eclipse2via]

Originally posted by QuickSilverGSX9
It might very well be overrun. Like I said, it felt like fuel cut, but, I didn't have a pocketlogger to log the outcome before. So, this is probably a pretty stupid question, but I thought I'd ask, what's the difference between overrun and fuel cut? Whatever the differences, aren't the results the same? The computer can't provide enough fuel for the amount of air entering the cylinders, so it I guess, cuts the injectors, or what? I guess this explains why when I turned down the boost to 14lbs I hit the same overrun problem, but it just simply happened later? This may not be true, because the overrun point did occur randomly to a point, but the last time it did happen later than any other time.

-Bill

When you overrun the airflow drops from max 1606hz to 1300-1500hz with a concurrent drop in DC. It feels like nasty miss/stumble. Fuel cut airflow usually maintains 1606hz but DC drops to 0. Feels like you broke your tranny. I never hit fuel cut before I put this MAF on.
Scott

 

[MaxBoost]

With the MAFT you hit fuel cut with 550's? Did the fuel cut defense switch work for you? Im running stock injectors and might just get 660s if this is true.



/

 

[eclipse2via]

No, the 550's are "On the shelf" permanently. They were non-functional. I hit fuel cut with the 450's. Tomorrow, I'm going to DSS and buying 660's. My DC's were up to 110% so with 48% bigger injectors my max DC should drop to around 75%. And giving me leeway for more airflow and an upgrade turbo down the road. Thanks for letting me know to update my mods profile.
Scott

 

[MaxBoost]

I think 660s with the MAFT even with big16g is the way to go. Does maxing out the DC of an injector have a similar effect as having a misfire? I dont have a logger or bigger injectors yet so any advice would help.
I wanna hear more from people who are using the blow through setup.

 

[eclipse2via]

Maxxing the injector has lot of side effects: leaning, knock, pulled timing, fuel cut as starters. If you're feeling a misfire it could be overrun or a misfire I think a logger or at least a egt gauge with peak hold is a necessity when tuning this MAFT.
Scott

 

[MaxBoost]

I know what fuel cut feels like. What i am getting with the MAFT and stock injectors feels like littel fuel cuts or misfires and happens at boost pressures as low as 9-10 psi. I do have the defense switch on though so its probably just misfires.
Regardless, the MAFT is definitely one of the best modificatons I have made.

 

[nine5raptor]

you aren't running platinum plugs are you? you might try leaning out the mid a bit as you might be too rich, causing the stumbling.