I have a b3 engine, slightly modded running lean

[lancerevo]

I have a b3 engine. Slightly modded. Fms street cam, Cold air intake & 2" straight exhaust. My problem is the engine is running lean at the top end (4000 - 6000rpm). I have modified the vaf meter to set the idle right. I can't make it richer because it will run rich at the low, mid range and still run lean at the upper range & the fuel economy will be horrible. I have an adjustable fuel pressure regulator. If I install it will it enrich in the upper range?

Thanks

[blkfordsedan]

just a few questions....
How do you know it's lean on the top end? do you know how far off it is?Are you using an AFR meter?
Have you changed the fuel filter?
Are you sure the VAF meter is working correctly?

I was thinking the other day about possible mods for the B3. One of the things I thought about was using a B6 ECU and B6 injectors on a B3.
My thought was that the fuel map for the 323 B6 ECU may be a little more aggressive than the B3 ECU. As long as you use the matching B6 injectors, it should be fine, and the tuning may be more appropriate for a modded B3. Of course, I could be way off base. Maybe someone has already done or tried it?

[festyfreak39]

give us some more info, do you have a wideband? what are your afr's at? depending on the exact number you might be doing just fine

im not to sure what festivas run n/a but i know miatas and they run pretty lean around that rpm.

the cam is the culprit of your problems, if you want to fix it the proper way maybe a n/a FMU unit or a SAFC or smoother sort of piggy back



hope this helps

[sasquatch]

you could try a b6 airflow meter but i dont know if that would fix your problem... your motor is drawing more air so give it more air.... probably give you a few extra hp in the top end too but i would get a wideband (or atleast a narrow band... but the wideband would be much MUCH better...) then get a safc on it to "trim" up your map and make it run good again...

[blkfordsedan]

I wouldn't think that those minor mods would throw the system so far out of range that it can't get the mixture right. I can't believe that the factory air intake is so restrictive (especially for a B3) that an aftermarket CAI would effect it to any significant extent. Plus, people put a header on the B3 and don't have any issues. A long tube header will increase air flow about as much as anything you could do to the intake, including the mild FMS cam, with a stock flowing head. It seems to me that his mods on an otherwise stock B3 can't be putting out more than about 70hp max, which is less than a stock B6.

I would first check the VAF meter and fuel pressure regulator are working correctly and that the fuel filter isn't partially plugged. Especially since you had the VAF apart and messed with the spring. Something doesn't add up. I would look for the simple things first.

I think adjusting the regulator for more fuel pressure will richen the mixture across the board as well. I believe the ECU assumes a set pressure when determining the pulse width of the injector. If it was OBDII it may self adjust based on the O2 sensor feedback. Maybe our system will do the same?..........I'm just throwing some ideas out there. I really don't know for sure how our VAF system works.

[iceracerdude]

...I was thinking the other day about possible mods for the B3. One of the things I thought about was using a B6 ECU and B6 injectors on a B3.
My thought was that the fuel map for the 323 B6 ECU may be a little more aggressive than the B3 ECU. As long as you use the matching B6 injectors, it should be fine, and the tuning may be more appropriate for a modded B3. Of course, I could be way off base. Maybe someone has already done or tried it?

Actually what happens is a b3 ecu will "seem" more aggressive. The way that happens is the b3 ecu actually holds the b3 injectors open a little longer, so now when you put in b6 injectors behind a b3 ecu, it runs slightly rich. Well I say "slightly rich" but you'd actually be bummed out by what happens to your mileage, This is how I run my b6 aspire with a turbo, I'm down to about 25mpg from around 39, but it's not my dd anymore. I did just do new rings and valves, so that might be slightly better now.

[lancerevo]

I am using a volt meter to monitor the o2. I know how to read it. And I have just installed a Mazda miata vaf meter. It works perfectly. What I had to adjust was the spring inside to make it softer because it was way to lean and the engine kept turning off if I let it idle. Also I drilled the hole on the vaf to adjust the idle mixture screw and found that it was already screwed in all the way from the factory. That's all the difference of a mx5 vaf. Not that it will increase power because the voltages comes from the ecu to the vaf not the other way around. I think, I will leave it as it is for now or try adjusting the fuel pressure a bit. I don't want to buy the b6 injectors because I don't want to get worse mileage. Right now I'm averaging 34 imp mpg.

[resuwrecked]

You gotta pay to play, in this case with worse gas mileage. More power requires more fuel. I can get 20mpg with my current setup easy if I am boosting all over the place. Driven like a sane person it will do 32-33. I think the cleanest setup/solution would be a SAFC with b6 or even b8/bp injectors and tune it like festyfreak said, the na fmu is also a great idea.

[festyfreak39]

Also, get a wideband because monitoring the single wire o2 sensor is not helping you much at all, it might even be putting you backwards. a wideband is also a little expensive too so it all depends on your budget.

[sasquatch]

widebands are awesome tools, you can watch your a/f's and see what your motors doing at all time... if your vaf is out of adjustment (mine was) you can adjust it and get even better fuel mileage (some people dont need to worry about this but i did) i also used mine to help me pass smog testing... and after i tuned it up, i passed about 30% better WITH the bp than i did with the b3... and when i put the b3 thru it had a BRAND NEW (few hours old) cat AND O2 sensor on it...

[blkfordsedan]

Actually what happens is a b3 ecu will "seem" more aggressive. The way that happens is the b3 ecu actually holds the b3 injectors open a little longer, so now when you put in b6 injectors behind a b3 ecu, it runs slightly rich. Well I say "slightly rich" but you'd actually be bummed out by what happens to your mileage, This is how I run my b6 aspire with a turbo, I'm down to about 25mpg from around 39, but it's not my dd anymore. I did just do new rings and valves, so that might be slightly better now.

I was suggesting running the B6 ECU and B6 injectors on a B3, not trying to fatten it up by running B6 injectors with a B3 ECU. As long as the injectors match the ECU it shouldn't run rich or lean. My thought was that the over-all tuning on a B6 ECU from a 323 may be more performance oriented then the factory B3 (since MPG was the purpose of the Festiva). It may not be any different, but it would be a cheap & easy mod if it made a noticable difference.

[lancerevo]

if I buy a set of injectors rated at 240cc. will it run very rich all the time with the stock b3 ecu?

http://cgi.ebay.co.uk/FORD-PROBE-MAZDA-MX6-626-INP-480-RECON-INJECTORS-/110596493539?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item19c01090e3

[muscle_Car1]

yeah because the ecu thinks you still have the tiny 120cc. so yeah you'll be dumping 2x the fuel in there, that might be enough for you to call it rich

http://www.fordfestiva.com/forums/showthread.php?p=197722

[lancerevo]

I found a way to improve the fuel issue. I have modded the ect sensor to make it run richer. I used a 12k resistor and wired everything to a 2 way switch, so I can switch it to the 12k resistor or the stock ect sensor. The car is more powerful across the whole rev range especially at the top end.

[Aaronbrook37]

I found a way to improve the fuel issue. I have modded the ect sensor to make it run richer. I used a 12k resistor and wired everything to a 2 way switch, so I can switch it to the 12k resistor or the stock ect sensor. The car is more powerful across the whole rev range especially at the top end.

Interesting... I'd love to see a picture of this setup. I know a lot of tuners frown upon ECU trickery, but did you experiment at all with different sized resistors? It'd certainly be unique to have a multiple-way control switch with a whole bunch of different sized resistors. Really cheap way to tune haha!