liam821

Im sure you all know about the honda-tech afc hack....poor mans hondata. Where you control boost using an afc with a MAP sensor hooked up to the TPS on the apex...i found a better one.

When i rebuilt my last engine i didnt want to use the secondary injectors (f-max erl mf2 fuel system although i had 550cc secondary injectors not 440cc) anymore and wanted something better. I read about the afc hack and thought i would give it a shot. I have a dsm so finding dsm injectors were easy.

My first impressions once i had it all working is...well it worked! I got the boost up to 9psi and it seemed to work pretty good, at least at WOT. EGT and a/f gauge both showed good numberes, and i was also monitoring the o2 voltage by using the "blue wire mod" on the afc which was also good.

The problems started happening while at 1/2 throttle. I drove my honda to oregon from san diego last week and going up and down through the mountains really sucked. I kept having to change the damn cross over point from vacuum into boost on the afc to match the current altitude so the car wouldnt run lean. But even with the right cross over point the car would start going into boost and the honda computer would change the air/fuel from rich (cuz of the afc) so a leaner value. (thats what close loop mode is all about right?) I could watch the EGT increase as this happened. There was also a stumble as the honda computer fixed this. It was pissing me off to no end.

So for a few hundred miles i was playing with the afc trying to make it better...and i just couldnt get it right. So then the thought came.

The afc hack you use a MAP limiter, and then step up from a negative value for fuel with the afc (i was stepping up to around +5%) once the car starts to boost.

So i was thinking, isnt a limited MAP (with a missing link check valve whatever) and the afc stepped all the way to +5% the same as an unlimited map with the same boost? (that is if i got the damn thing tuned right)

So i pulled into a gas station and modded the fuel system. I removed the missing link so i had an unlimited map. I set my AFC at -40% from 1000rpms to 8000rpms so it would keep it no matter what boost level i was running.

I started the car....and it works. It works really well. Its night and day difference. Its AMAZING. In and out of boost you cant tell the difference from a driving stand point. Transition into boost...well there is no transition..its not there because its that smooth. Its as smooth as my eclipse. 1/2 throttle into boost is the same way. 1st gear burnouts feathering the gas so you dont slam the rev limiter...smooth as silk as if you didnt have a turbo. Its a poor mans hondata only i think its just as good.

EGT, a/f, and o2 voltage are all good also.

I have a friend with a b16a/turbo in a 95 civic coupe running 7-9psi. He was running the afc hack like i was. He drove my car...almost drove it off the road because of the torque steer (hah gotta love the d-series axles) but was really impressed by how smooth it was. We rewired his AFC back to stock removed his check valve set his afc at -40% across the board and took it for a spin. The first words out of his mouth were "wow..what a difference that made..its smooth." His over rich in boost, ugly transitions, and all the other bad side effects were gone. Hes using a p28 chipped ecu with a dohc mugen program.

So this is my currect setup:

d16y7 block with z6 head (hey it was cheap) z6 head gasket
p28 ecu (stock unchipped)
99 Turbo DSM 450CC injectors
89 CRX Si resistor box
Apex AFC fuel computer
Walbro 255 lr/hr high flow intake pump
Stock honda MAP sensor (connected to the t/b in stock location not limited)
Stock honda FPR (off the the fuel rail)
Stock fuel pressure, ~40psi at WOT, increases as car boosts. (1:1)
boost set at 10psi regulated with an apex avcd boost controller
garret t3/t04e .48a/r 54 trim

apex fuel settings are, -40% from 1000-4000rpms, -35% from 5000-8000rpms (to be safe i increased the 5000+ rpms by 5%). The settings are the same on high and low throttle settings.

I dont get a CEL with 10psi of boost, but i do with 11psi. Im sure if i changed my high rpm fuel from -35 to -40 i could squeeze a little more boost outa the system but i dont wanna push my stock mutt engine any father then it already is. But i have been running around with 10psi with this system for a while now without any problems what-so-ever. And i have been really enjoying good gas milage and just awesome throttle responce.

I highly highly highly recommend this setup for anybody that wants a cheap hondata like driveablity without spending the money. Almost everybody has a afc and DSM 450CC injectors are really cheap. Not to mention you dont have to hack anything..just set fuel at -40% and go with it and have the afc wired like its supposted to be.

Comments are welcome.

liam

dustin

Haha, that's a great idea.....! I see no reason why it would not work exactly like you say. Basically just indirectly 'extends' the stock fuel map into boost...

Dustin

zojirushi

soo, theres no need for a fmu???? Could i try this on my 95 integra ls?


[Modified by zojirushi, 3:31 AM 3/1/2002]

liam821

Nope, no FMU. Just an afc and DSM injectors. I dont see why it wouldnt work on your ls. My friends running it on his b16a and is loving it.

liam


[Modified by liam821, 12:39 AM 3/1/2002]

zojirushi

wow, awesome

intekragsr

sounds great, but why is it called a hack?

DSF

That's probably because of the limitations of the OEM MAP sensor, which is said to be good up to 11-12psi. You could probably swap in a 2bar MAP sensor and just change your fuel calibration settings to compensate for the change in the boost/voltage ratio.

Great work, man If part throttle detonation is ever an issue again, you could always use the TPS mod to throw the ECU into open loop at earlier throttle openings.

Mr. Vapor

dbman is gonna love this post hehehehe

zojirushi

haha, another addition to honda-tech's ghetto engineering

apexii

Very, very interesting....

VTC_CiViC

Ok perhaps I'm stupid or I just didn't catch it, but how exactly do you prevent a CEL from the MAP picking up boost since you removed the missing link?

dbman96

he's using the AFC to reduce the map sensor signal enough to prevent a CEL. So if for example the MAP is reading like 4.2 V and at -40% that brings it down under 3 V so it doesn't CEL on him. If he boosts 11 psi, it makes it 4.4V (I'm guessing on the voltages but you get the point) and the -40% only drops to 3.1 so the CEL comes on.

This is thoroughly interesting; I'm still a little confused on why it improves matters but I'm all for progress. The reason this helps you is that you were running a missing link. If your map signal is physically limited, the AFC hack I described is absolutely worthless, since there is no "boost" signal reaching the AFC. The only way it works as I described is if you use something electronic to limit the MAP signal, a topic that was discussed at some length when this whole ghetto thing came up in the first place. That is DEFINITELY why you were having trouble leaning out on your road trip.

With your new setup the only problem I see is that you were worried about part-throttle leanouts under boost. The reason this happens is that the VAFC hack is reducing the MAP input so it doesn't trip into open-loop. The way you've got it set up now, it's still reducing the MAP signal (-40% under any conditions) enough to prevent it going open-loop until you reach full boost, unless the throttle is wide open. Sounds like it's working great for you but I'd be interested in watching a wideband O2 plot of your car at part-throttle boost. Aside from that I think this is a great solution for people who don't have an electronic map signal limiter like on the J&S V.2

Keep us posted!

VTC_CiViC

Ahhhh.. VTC=

I see now, I forget that the AFC manipulates the MAP's signal directly. I've gotta give that a try tonight! Good thinkin Liam

boosted hybrid

I might have to try this on friends boost car. Quick question though:

How are you running DSM low impedance injectors with the stock ecu?

VTC_CiViC

Resistor box from P/H Honda's.

boosted hybrid

Thought so...he just didnt mention that. I wondered how the AFC was able to provide the variation in resistence to run them.

niedejb

Could you remove a portion of the check valves so that the MAP reads "partial" boost. This could allow you to run lets say -20% on the AFC and still have some tunability for fuel vs RPM?

If you need -40% to get the MAP to work, you have no way to lean any part of your RPM band down if you were way too rich at any one point.

Curious.

synthtk

actually he did, thats why he listed the 89 CRX Si Resistor box

you can also just wire up some resistors inline with the injectors (like i have) and it works also.

-Chris

cyan1de

liam... with your turbo (specifically your exhaust .48a/r), when do you get full boost?

btw, nice idea... i may do that instead of waiting for hondata 1b to come out.

synthtk

Also Liam forgot to mention that the Throttle points are set to 98% low and 99% high in the AFC.

-Chris

liam821

It should be hooked up the correct way with high and low throttle both set at -40%. I just havent gotten around to do any of that (been lazy). But thats the idea. I would set my cross over point at around 72% because thats when the honda ecu switches to open-loop mode.

(i just didnt wanna confuse people about the system..it should be hooked up like a stock afc it hooked up)

liam

liam821

dbman:

I was using two map sensors with my last setup. One limited one unlimited into the TPS input on the afc. It works pretty well but it wasnt very smooth!

The new system works much better.

liam

liam821

I get around 5psi at 3000rpms in 3rd gear. I hit full boost by 3300-3400 in 3rd normally. I cant handle a laggy turbo no thanks. At 3800rpms and above when you floor it you get almost instant full boost! (very nice)

liam


[Modified by liam821, 11:18 PM 3/1/2002]

Xerxes

wait so now are you just running the TPS signal back into the VAFC like it's supposed to be done?
the % crossover shouldn't matter because you said you're using the same -40% maps for both high and low throttle, right?

-Xerxes

VTC_CiViC

Right
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