ignorant question/comparison of JWT ECU and S-AFC

[240marcuSX]

im a bit confused on the matter of which one to get the ECU or S-AFC. I know that with the safc you can play with the amount of fuel sprayed by the injectors to run higher boost? so how does the ECU do about the same thing, since you dont just fiddle with the ecu to switch fuel maps. If i were to get an ECU for 50 lb/hr and the whole works, I dont get how i would be able to change the boost using the same ecu? Help me out, im stupid. :bandit

[:: orion ::]

First, an AFC cannot make the injectors spray more fuel than they're rated for. You can richen up the low end if need be, but up top, if the injecotrs are maxed, and AFC can do nothing.

And just an AFC doesn't address ignition timing - At stock timing with 6psi you can blow a motor easily. It needs to be retarded some, roughly .5 degrees per PSI as a rule of thumb.

JWT addresses both - Proper fuel trim with bigger injectors, and timing. But the timing maps are conservative enough to run 13-14psi, so you'll be down on power with less boost and JWT.

The "Basic KA-T" formula that seesm to work is:

370cc injectors, AFC, and base timing retarded appropriately = ~250rwhp at a max, maybe 8-9psi (depends on the turbo).

JWT + 50lb/hr + stock timing + Cobra MAF is good for another 100rwhp over what I posted above...bascially up to 350rwhp.

(And BTW - Boost is controlled by the wastegate via a boost controller that modulates the signal the wastegate sees...not by the ECU in our cars)

Hope that help you begin to understand - Read up on this and know a good bit about turbo systems or you'll blow motors while you figure it out...i.e. learn to read compressor maps, figure out BSFC, etc...

Later - Brian

[fiznat]

damn I still need to decide if I want to go JWT + MAFS or the do it yourself setup with MSD BTM and S-AFC.... Arrugh I have a feeling the former would be easier, but the latter will give me more room to spread out. Dammit decisions decisions.

[Silent Drifter]

Secret Services here in Tampa is reprogramming s13 ecus an giving you dyno time so they can make each ecu for your personal setup. I cant wait to get my car done an get it programmed by them. It will put a JWT to shame.

[WDRacing]

For a non skilled person, which tends to be most everyone, no offense, the JWT is a good deal. They run safe maps and you don't need to mess with anything other then the install.

I wish I had my fuel system available for purchase. With that and a simple MSD timing retard box you can run all the boost your internals will stand. Oh well, I can wait till December when I finnally get home.

Not that the SAFC is a bad thing, especially since it has a knock meter included now. But you need to know what your doing with it. Or pay to have it tuned.

WD

[fiznat]

"your" fuel system?

[WDRacing]

Email me Fiz, I don't want to hijack anymore threads.

WD

[240marcuSX]

thanks for all the info. I think i know a good amount about the turbo and turbo motors. there were just a couple things i get hung up on. I knew that if i got the JWT ECU + 50 lb injectors + 255 pump. id be pretty good to go til about 9 psi. I just never completely understood why the said would work.

so if you were running 7 psi with a SAFC, you would need to retard the timing 3.5 degrees?

where can i buy a cobra MAFS? Link please?

once again thanks for all the great information

[Silent Drifter]

http://www.ebay.com

[klattr1]

http://www.ka24de.com

[fastpace]

not to hijack the thread, but I am selling a used cobra mafs for $120 bucks shipped. pm me if interested.

[Structure240sx]

u can always get a jwt and then a safc to get a little more aggresive. i think thats what i might be doin now

[:: orion ::]

Guys...

Give up on the "JWT runs too rich" thing - That was true in the past, but not now - They have leaned things out a bit and they run ~12:1 A/F under WOT, which is about dead on...

Their timing curve sucks for low boost, though...

Later - Brian

[fiznat]

thats a lotta dough- almost a grand right there, and that doesnt even include a pump or injectors or MAFS or...or...or.....etc

[240marcuSX]

is the MAFS interchangeable between the E and DE? id guess they are, just making sure,

Im planning on getting:

for fuel:50 lb/hr injectors walbro 255 fuel pumpJWT ECURRFPR(comes with the kit below)

Turbo:the IAP kitTurbo XS DSBC

and then eventually get some new internals when i get the itch to up the boost past 10, I was told it wasnt smart to go above 10 psi on stock internals.

Ive got about $4600 (not to flaunt) to start with right now, so that should get me boosting at like 7 psi.

orion - "Their timing curve sucks for low boost, though..."what psi do the timing curves suck for, at what point does the curve not suck?

[:: orion ::]

1) is the MAFS interchangeable between the E and DE?

2) for fuel:50 lb/hr injectors walbro 255 fuel pumpJWT ECURRFPR(comes with the kit below)

3) and then eventually get some new internals when i get the itch to up the boost past 10, I was told it wasnt smart to go above 10 psi on stock internals.

4) orion - "Their timing curve sucks for low boost, though..."what psi do the timing curves suck for, at what point does the curve not suck?

1) No - Quite different actually.

2) No need for the RRFPR with 50lb'ers and JWT ECU - It would be WAY too rich then...

3) Stock internals and conservative JWT ECU has done 350rwhp stock internals - And 12psi daily for a handful of cars, which is ~300rwhp average.

4) I'd say 13-14psi it's reasonable. 15 degrees total timing is not much - 2-3psi you can use stock curve with advance, 4psi you need to start dropping it per PSI. 8psi will make good, safe power with ~20 degrees total timing...JWT gives 14-15 degrees at WOT, no matter the boost.

Later - Brian

[fiznat]

hey orion- quick question- how many degrees BTDC is the timing at idle? also, do you know how much advance the ECU gives under normal conditions at WOT?

[:: orion ::]

Timing at idle should be 20 degrees base for the DE, but the ECU will move it around 22-25 from my experience. When you set the base timing, you HAVE to unplug the TPS so the ECU feedback is broken and the timing will not jump around.

As for total timing at WOT...IIRC, it's around 30-32, depending on load. So the ECU feeds 10-12 degrees advance (15 as a max I'd bet), under load that is. I have seen 40-45 degrees total on the highway just cruising...part throttle.

I could use some better #s for a stock ECU...But I don't have a MDM-100 to use locally - If anyone on here does, go do some long pulls and let us know what it reads once you punch it...and we need to know the correct base timing.

Later - Brian

[fiznat]

wow you saw 45 degrees advance? that seems like alot considering highway "cruise" RPMs..

eh anyways thanks for the info... I didnt know where the base timing started so this gives me a good reference to think about when I'm considering retard under boost etc. :thumbup what do you figure is usually a good amount of retard per psi boost- about .5 deg?

[240marcuSX]

1) what MAFS can I use for the E then? Z32?

2) Could I switch the 50lbers to 370cc's and use the rrfpr, jwt ecu, and walbro 255? that way i wouldnt have to swtich the fuel rail, or should i just drop the rrfpr and use the 50 lbers?

Thanks for all the great information Orion :bowdown Ill trouble you no longer....

[huguetpj]

1) what MAFS can I use for the E then? Z32?

2) Could I switch the 50lbers to 370cc's and use the rrfpr, jwt ecu, and walbro 255? that way i wouldnt have to swtich the fuel rail, or should i just drop the rrfpr and use the 50 lbers?

Thanks for all the great information Orion :bowdown Ill trouble you no longer....

1 - Why not have JWT program the Z32 MAF for ya?

2 - What inyectors does the JWT ECU come programmed for? I wouldn't recommend changing the inyectors if the ECU is already programmed for a specific size. Just RRFPR and 50lb'ers won't work. You'll probably won't even idle

[Nathan]

The JWT ecu can be programmed for a variety of injectors...you have to tell them what you are using before they program it. They also have an injector flow bench so they can do odd sized injectors like my 75# hr. delphis

[240marcuSX]

I dont have any of the items i have listed yet, so i dont have the JWT ECU yet, I do have another ecu though. im making plans to buy these items soon. im just seeing exactly what im going to do.

we're having our garge built now, and it should be finished in like 3 or 4 weeks, so i need to get moving and ordering some things and maybe i can install it all during thanksgiving break or so.