h2k
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Posts posted by h2k
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Im looking for a new set of cams for my 700++hp rb25det engine. I used to run tomei 256 poncams but i've taken those out to be in my daily driver skyline. for my racecar I want very aggressive cams, does anybody have JUN 292 degree cams for sale? or know where I can get any rb25det cams that are more aggressive then the tomei 280 cams?
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I pulled this copy paste from a MegaSquirt site. Wich does lead me a bit closer to making a MAP to MAF signal converter
The Ideal Gas Law
You might remember from high school physics classes that an ideal gas (which air is reasonably close to) obeys the relationship:
PV = nRT
Where:
P = pressure,
V = volume,
n = number of moles (which is related to the mass of the gas, i.e. 1 mol = 6.023x1023 molecules of the gas, and n = mass (in grams)/molar mass(MM)),
R = the ideal gas constant,
and T = the absolute temperature.
What does this have to do with fuel injection? In order to know how much fuel to inject, we need to know how much air is going into the engine so the chemically correct mixture (called “stoichiometric”) can be achieved. So for a fuel injected engine, we use sensors to determine the pressure in the intake manifold and the air temperature. However, the temperature in this equation is “absolute temperature” measured in Kelvins which is equal to degrees Celsius + 273º.
The volumetric efficiency (VE) is a percentage that tells us the pressure inside the cylinder versus the pressure in the manifold. We know the volume (V) from the displacement of the engine. Thus we can calculate the mass of air (M) in the cylinder (proportional to n) from
n = PV/RT
=> M = n x MM = PV/RT x MM
= (VE * MAP * CYL_DISP) / (R * (IAT-32) * 5/9 + 273)) x MMair
Since:
P = VE * MAP (i.e. the pressure in the cylinder in kPa),
V = CYL_DISP = the displacement of one cylinder (in liters),
R = 8.3143510 J/mol K,
and T = (IAT-32)* 5/9 + 273 to convert IAT from ºFahrenheit to Kelvin.
Note that we can combine the constants R and MMair into one, and we will ignore them from this point on since they can be hard-coded into the assembly language code and neglected after that.
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Or you could take 5 minutes looking at the all 3 wires to change in the wiring diagrams and do it yourself, nothing inside needs to be changed. MSD timing window for $80 will run the vct at any rpm point your heart desires at a touch of a button.
H2K, you still have that link of the system i showed you that can convert the signals? cant for the life of me remember its name? Bit pricey but looked very good
"MAF Translator Pro" is the system you showed me
don't remember the url but a google will find it -
The beauy of speed density systems on factory ecu's is that their model for charge temp (the actual air temp of the air in the engine) is mapped over g/s of airflow (which without a map sensor is based on rpm and MAP itself).
If I was you I would rescale the maf down to a suitable size to get good airflow figures from it. I would also place a intake air temp sensor into the manifold. I would then get a micro with at least four ADC. Three input chanels for MAF, MAP and IAT and one ouput for a psuedo MAF votlage for the PFC. YOu then will need to be able to map/tune the intake air temp sensor over MAF voltage as a multiplier of AIRtemp to give you a final Charge temp.
ie
MAF Voltage Air Temp Multiplier
0 2
0.5 2
1 1.9
1.5 1.7
2 1.5
2.5 1.3
3 1.1
3.5 1
4 1
4.5 1
5 1
The actual charge temp of the air in the engine is the "Air temp multiplier" times the current IAT sensor reading. The above mulitplier curve will need to be tuned based on the position of the IAT sensor. You will also need a multiplier of RPM as well to take into consideration the difference in voltage of a linear MAP sensor vs an expotential MAF sensor. I would then apply the ideal gas law and see what happens.
My advice is that unless you have a good understanding of microprocessor design and implimentation and a good tuning back groudround then DO NOT DO IT!!
Actually I go to a engineering school that also educates in microprocessor design tough it's not what I study(Machineengineering). But I do know a couple of buddys that do that course. I was also thinking of the MegaSquirt ecu system wich is a opensource system. All Megasquirts can run MAP system på default and they should have knowledge of how ideal gaslaw is applied and the correct scalars and mathematical operations needed based on pressure, temperature and tps signal
I'll try that forum, and if I get good answers I'll get somebody at school to solder me a PCB with a microprocessor that does what I want.Another idea is to actually use a megasquirt ecu, wich has map sensor and everything it needs, included output lines. All I'll need is a new firmware for it. And then use the megasquirth purely as a converter from map to maf, it's so cheap it will be well worth it.
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You've answered your own problem in a way.
Put e decent plumb-back BOV setup on (GTR is fine), and move the AFM further away, even before the throttle body end if you must.
Will fix all your issues for a couple hundred $$
I have allready tried this, used the HKS SSQV with resirc kit. Improved slightly, but didnt quite do it...
stop suggestion MAF alterations, the point is converting to MAP. darnit =)
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I know it's off topic but are you running a GT4088R on an RB25DET with that engines head/inlet system/valve train ?
A .
Im running with oversized wiseco pistons and eagle rods. the head is heavily ported and polished but with stock valve train except tomei cams. I am however considering upgrading the head to solid lifters, 272 cams and stronger springs etc.
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If it is on an rb25, then you can sell the PFC for more than you can buy an rb26 D-jetro PFC. Send it to URAS, he can make the internal mods to run the rb26 ecu on a 25, although you do lose the VCT which can be controlled seperately. BUT the question is why? I have an AFM that will hit 5v at approx 500RWKW, and wont cause a restriction at that power level, and cost almost nothing to make.
I've made a 4" maf from a Q45. I still max it out with 5.2v at 5000rpm when running 2.0Bar of boost. I run a rb25det with approx 800ps at the flywheel, reving up to 8000rpm. I want to try map =)
Stop entering negative posts like "upgrade MAF, change MAF, buy d-jethro". I know I can, but I don't want to. I want to trick a PFC to use MAP.
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is your issue that you are hitting 5v or running out of load axis on the PFC
both.
I allready put the Q45 internals into a 4" pipe and remapped. Problem is with such a large MAF im having trouble with idling and driving in the city. It's to rough and the signal also fluctuates because of fanblade turbulense. I have a rather large Garrett GT4088R turbo with 4" inlet and not to much space for inlet piping. Also using a atmospheric dump valve, im having a very hard time driving around without stalling the engine. But high speed driving it's no problem with a large maf. Dragracing and trackdays go very well.
But still, this is a topic I am very interested in.
pV = mRT
I've talked to a company(SplitSec) that makes alot of MAF and piggyback fuel products and I qoute them:
"Deriving MAF from pressure is very difficult. The VPC never worked well
which is why HKS obsoleted it. If you want to go map based, which you
should anyway with a big turbo, you need an ECU that can work directly off
of a map sensor"
I agree it might be difficult, but when a d-jethro can do it, im sure another unit also can and convert the output to 0-5v.
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Allright I forgot about the air temp sensor the MAP sensor requires.
Forget about buying a new PowerFC, ofcourse I know one sollution is "just buy a new" ecu. I could also sell my skyline and buy new car if I want more power. But it costs money. The whole point of this topic is exploring options to convert a regular PowerFC from MAF to MAP, and as cheap as possible.
What I want is a small box with 2 inputs and 1 output:
In:
Map sensor
Air temp sensor
Out:
0-5v MAF signal
Ofcourse this small box requires a cpu of some sort to calculate out the final signal to represent air load.
So far the alternatives that have been suggested is:
HKS Vein Pressure Converter
MAF Translator Pro
Both these products does what I need, but it also does alot more I don't need. Wich makes them expensive. The HKS VPC costs the same as a used and complete PowerFC on ebay. And they also offers alot of tuning options similar to AFC units. I don't need it since I have the PFC and it's fuel map for tuning.
There must be somebody who has thought about this and actually done something?
And Im shit tired of hearing: just buy a PFC D-jethro. I want to modify what I have.
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Alot of people max out a MAF setup with the powerfc. The Q45 maf can't make as much kW as im running.
The maf has 3 wires:
12volt IN
Ground
Signal out(0.2 to 5.2 volts)
Now I've found a Motorola 2.5BAR MAP sensor wich has 3 wires:
MPX4250A series
12volt IN
Ground
Signal out(0.2 to 4.9 volts
Now im might be thinking way to simple, but WHY should it not work to use this map sensor on a completly regular Apexi Power FC and feed the map sensor signal into the afm wire. In simple terms, to convert the MAF to MAP system and remap the ecu with new voltage values depending on load.
Can anybody explain to me if this would not work, why should it not?
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hmm...It would help with a picture
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I'm still doing a bit of research on this area because I DO want to go for a dual afm setup if only because nobody else has done it yet
Anybody know where I can buy a prefabricated Y-pipe like this one on the picture? it's from a singelturbo rb26dett conversion:
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I have a 93 model R33 gts25t and I use it for trackdays, I am satisfied with the brake performance of the stock discs but now they have become worn and show hints of small cracks. So I have to change to new rotor discs, but I cannot afford to buy a complete big brake kit. But instead of just buying new stock discs from Nissan I want to upgrade the looks by changing to discs wich is grooved and drilled from someone like Brembo or EBC. Do anybody know what to buy or where? I can't find anything on ebay or product catalogs :\
I actually found the R33 gts25t in a EBC brake rotor catalogue, it's the same parts nr as the R32 GTR.
front: GD1226 V 5 296 54 32 / 30
rear: GD699 V 5 295 64 18 / 16
Anybody knows where to buy EBC's? or know of other alternative brands
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I have a 93 model R33 gts25t and I use it for trackdays, I am satisfied with the brake performance of the stock discs but now they have become worn and show hints of small cracks. So I have to change to new rotor discs, but I cannot afford to buy a complete big brake kit. But instead of just buying new stock discs from Nissan I want to upgrade the looks by changing to discs wich is grooved and drilled from someone like Brembo or EBC. Do anybody know what to buy or where? I can't find anything on ebay or product catalogs :\
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I have 2 suspicions, either my coils might be the source of the problem, or it is because of the large size of the q45 throttle body. Very little throttle percentage lets in large amounts of air into the plenum and Im suspecting the pfc doesnt let go of the "idle" mode.
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can you take a few pics of your engine bay please? can you take a few of the air filter setup and AFM position ? I need to see how its setup.
What afr are you running when your getting this miss ?
Take pics of the location of your AFM from the mouth of the turbo and post em up then PM me once done so i can check it out.
My engine bay:
Only difference since pictures is that I have a much larger air filter on now, about double the size.
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You have some sort of ingition issue then
Stock coils combines with the HKS box has many a time run over 500rwkw.
Plenty of Jap cars have done it
excactly, thats why I need a HKS box that fits my ignition system. the DLI2 amp unit apparantly doesnt. I cant find anybody who has made it work and how.
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Do you get what he meant though?
Doesnt sound like it as it would solve your problem, and not cost much
At first I didnt understand it, but after reading it a couple of times I think I get it =) only running on MAF, and making a tune to compensate for the "false" air that runs trough the other funnel. I get it...interesting suggestion.
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Changing to map sensor is very expensive since I need to change my pfc unit. And since I live in Norway it is not very eazy to sell used skylineparts locally =)
I was hoping there was a easy and cheap fix with paralell wiring for dual afm's =)
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Why have 2 AFM's? You don't need them, you can tune off one. So just use a "Y" inlet, the Q45 AFM on one and no AFM on the other.
Yes
cheers Because I maxed out the q45 afm I have already at 1.0bar, and I'm currently running 1.5 bars. And I want to go even higher =)
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What setup are we talking about?
Bottom end:
RB25DET bored 2580CC
Wiseco forged oversize pistons
Eagle forged conrods
Calico Racing bearings
Top decked
Head:
Shaved head
Ported and polished
Valve and valveseat cut
Tomei poncams 254
Cometic multilayer steel gasket 1.6mm
Other:
OBX T4 Pulse split manifold
OBX 50mm wastegate
Garrett GT4088R pulse split turbo
JUN-style intake plenum (portmatched)
Q45 90mm throttle body
Q45 90mm MAF sensor
Nismo\JECS 800cc injectors
Nismo Adjustable fuel pressure regulator
Apexi PowerFC
Apexi pod filter
Apexi AVC-R boostcontroller
HKS SSQV bov
Innovate Motorsports LC-1 with XD-16 Wide Band Kit
BOSCH 040 fuel pump
Oil catch tank
Oil cooler and filter relocation
OS Giken twinplate racing clutch
HICAS removal bar
Hybrid FMIC
3" straight exaust with 5" jap exaust tip
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Yep. I think the "more boost, smaller gate" theory is a bit whack. You basically need enough wastegate to drop the turbine pressure sufficiently to stop spinning the turbo more. GT4088R on an RB25 is an interesting combination - what is the spool like?
In low gears it's pretty slow, I geet boost at 4500rpm and then it just explodes with power. But in 4th gear I get 1.5bars from 4000rpm. Im running a pulse split\divided exhaust manifold so it helps spool-up alot
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Adjusted my TPS yesterday, was at .450v, set it to .600, hesitation is near gone, I can just hear it, but cant feel it
I just checked, my TPS is also set to .450v. I'll try .600 tomorrow and see if it helps me to!
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You dont need stronger spark i reckon
You need GOOD coils, and GOOD plugs, and a GOOD tune.
Thats it.
The HKS spark box is only for when you get above 350rwkw, if your breaking down before that... coils is the likely option
I'm running a GT4088R with about 1.5 bars of boost now. It starts popping and misfiring under boost after that. But I want to run about 2.0 bar. And im aiming for about 650-700hp at the wheels
don't remember the url but a google will find it
cheers 
Faq: Apexi Powerfc - Frequently Asked Questions
in Tutorials / DIY / FAQ
Posted
Hi,
Will you update the FAQ on apexi's release of new PFC's with d-jethro for RB25DET ECR33 ? The part number is 4E14BN32 and fits series 1&2. Finally gts-t owners can get rid of the AFM unit and still keep the NVCS system(since RB26DET pfc d-jethro conversions lost that feature).