I just found a machine shop that is going to charge me $45 to bore my maf. It's only a 3 minute job. They can precision bore it to the diameter I want so I guess there's no other way. I'm thinking about going from 50mm stock to 52.5mm or maybe 53mm. I'm trying to lean out the af ratio so I'm not going to do any fuel compensation.

How much bore would be safe without a jwt ecu program or fuel adjustment? Are there anyone here using a bored maf without setting the fuel?

yeah, if you are not going to have the ECU reprogramed, it will do nothing, and if you did this, it will not do anything preformance wise, I did the Stillen bored MAF&TB w/reprogramed ECU, it was a waste of time and money.

Your car may go into limp mode with the bored MAF. Well with a 53.5mm bored MAF, a car we worked on here with a stock ECU went into limp mode!

if youre going to bore it to lean it out, only bore it like 0.5mm

i do not think 0.5 will do anything at all
just poilsh the sucker with out bore

I think EricDD(or something like that) on this forum has done it, but he also compinsated for it with adjusting the TPS somehow...
~RYan

just do a quick calculation of the areas of the stock maf and the size that you want. you can then figure out the percent difference which would be the same change in A/F I think....

Khiem

I have one installed. I have s4 and s3/s4 program but jwt forgot to do the bored out maf prog. According to Clark Stepler of JWT it will lean out about 6% w/o the program. For $100.00, that's not enough reason to do the program. I don't think it will hurt my motor. I'll find out the end of this month if there are changes and hp gained.
Bob

lucino vzr,

How much was the bore?

Good thread to keep track of...since I have the turbo program and I think it is tooo rich

Why not get a safc to lean it out a little. Of course if you dont have/want to spend the money I see why not. The safc is good to use for that purpose.

well i ran for a while without fuel compensation, but I don't know how much I bored. I decide to increase the TPS voltage a little untill I can dyno and get a good air fuel reading to use as a guide with my EGT gauge. the TPS doesn not add that much more fuel anyway.
yeah, if you are not going to have the ECU reprogramed, it will do nothing, and if you did this, it will not do anything preformance wise, I did the Stillen bored MAF&TB w/reprogramed ECU, it was a waste of time and money.
the reason you didn't see any is BECAUSE it was programed for. your not leaning it out your just running a bigger product. at best that way you will only see an increase in throttle responce. if you bore it and leave it you will lean it out increassing performance and gain the throttle reponce.

I would not think you would be in that much danger because the 02 will add fuel anyway. but I wouldn't bore it to 53mm, I would go less.

I just bored it out myself. Screw the machine shop! It's easy, only took 15minutes for the boring with an electric drill and another 30 minutes for sanding and polishing. I estimate the bore to be 2.5mm. I'm going to test drive it right now. Will report back later!

I used a rough file and sanded it smooth after. I would guess I bored it some where close to that maybe a little less. but at the opening I would say I bored it more like 4-5mm, to give it a funnel effect. just guessing on the measurements though

Yeah, I just thought of something, a while back someone oh here was saying that a big tunner was doing some tunning trick to get the car to lean out by adjusting the TPS, I'm not sure if the TPS is the only thing they used to lean it with, but if you could get to a dyno, I bet you could figure out what voltage you need to be at.

It's actually kind of easy to tell how much you bored it. The outside diameter of the pipe is 54mm and the inside is 50mm. The pipe wall is 2mm thick so you can see how thick it is by looking at the slit inside the hole. Anyone who took out the maf will know what I'm talking about. Just look at the slit to see the remaining thickness of the wall to determine how much you bored it. On mine, it is now half the thickness of stock, around 1mm left so I know the bore is around 52mm to 52.5mm which is 2 to 2.5mm bigger than stock. I don't know what the tool I used is called. It's a round 2" diameter disc shaped polisher made of metal wires pointing outward. I then sanded it down real good with light sand paper. It's now much smoother than stock.

The difference is noticeable especially right after I put it back on. From 2000rpm to 3000rpm, it just lunged forward like how it felt from 3000rpm to 4000rpm ** the mod. I went straight to g-tech it to determine whether any real change in power was noticeable.

On monday, my average 0-60mph time from 3 runs was a 6.25sec with a very small +/- .05sec variation.
Today, my 0-60mph time avg 6.05sec with just as small a variance between runs.
All my runs were on the same road, at the same starting point.

To give you an idea of how consistent my times are and how accurate the g-tech is, half a year ago, I g-teched my car after I put on light weight rims. The times were from 6.23-6.31sec. I haven't made any changes to my car until today when I bored the maf.

I am damn happy with my new record time of 6.03sec. However after driving for a duration of time, it seems that my low end power seemed weaker than right when I put it on, but still feels better than with the stock maf. I guess the car running in close loop learns of the mod from the O2 sensor and gradually compensates with more fuel therefore losing the lean af ratio effect. I am afraid the ltft will adapt to the change from the stft and cause the open loop(WOT) to run at stock af ratio thereby negating the hp gain from running lean. However the effect of the smoother, polished maf is still there(higher velocity due to less air/surface friction).

I will g-tech my car again after a week or two to see whether the ecu adapts. But at least I dispelled the myth spread by countless people that running a bored maf without reprogramming the ecu or adjusting the fuel map is detrimental. At least for my car this isn't true. It is one of the easiest and cheapest mod I've done to my car and I encourage everyone to do this mod. Stay tuned.......

Sorry for typing so much.... I didn't even realize how long it was... just too excited after the test drive..

I got my maf bored out to 53.5mm for free. My friend in the military did it for me. If you know someone, make sure to tell him that it has to be a precision boring.
Now I have a question. If with out a program it's only 6% leaner, do you think I'll gain more hp if I adjust my tps to like 47? The range is 45 to 55. My tps is set at 50 right now. At what point do you think it will make more power.
TIA
Bob

Typical stock air to fuel ratio is 14.7:1. I think the engine should be able to handle up to 16:1 without any harm. The difference from 14.7 to 16 is an 8.8% increase. There's no way to say how much gain, if any, you will get from adjusting the tps voltage. The only way to find out is to do back to back comparisons on a dyno, g-tech, or 1/4 mile run.

Whether the ecu will gradually revert to the stock af ratio is still a mystery to me. My butt dyno now tells me my car feels the same as before the bored maf. It could just be mental. I will do another g-tech run in two weeks to find out.