98 TRD 3.4L Turbo , Methanol , LT

MAF pre turbo would be good, however your stock mAF won't give an accuratemeasurement on a 4" pipe; you will be running way lean.
The boost will not affect the MAF, what will affect the MAF is mostly yourBOV. A couple of options:

1: Position your MAF before your BOV. Don't do this. When your BOV releases,all the air measured by the MAF goes out the BOV and your run way too rich. Ifyou do a WOT run and suddenly take your foot off the gas, chances are yourengine will stall.

2: Position your MAF after the BOV. A little better. However, when your BOVreleases, you can sometimes get air flow that goes backwards over your MAF.Unfortunately, the MAF still measures this air flow, again causing you to runrich and possibly stalling. You can tune how hard the BOV releases to limit this.

3: Dont run a BOV. When you can still run rich as the manifold pressurereleases via the turbo, it’s a gradual change and the engine isn't"shocked" with too much fuel too fast. Some say the Turbo thrust bearing will go bad prematurely without a BOV but Ive seen turbos go 100k+ miles with turbo's. Im not use a BOV.

4: Run your MAF pre turbo. You willneed to find an aftermarket solution to fit the 4” pipe; stock MAF won’t work. This is not so different form option 3 if you are not running a BOV, you will still have air back flow over your MAF. However, if you run a BOV, this is the best option.

 

You'll be fine dude
Just get a 4" to 3" reducer for the turbo inlet and use a 3" air filter... done deal.

 

I wouldn't

 

I'm going to try it pre turbo. Gio, you and I have the solid one piece maf with housing, way different from the plug in one. I have a bov that I bought but I don't want to put it in just yet. I think what you were saying is valid too Andrew, that properly adjusted, the bov may prevent that pressure from blowing back out the air filter after a long pull and just going to neutral. I'm not convinced yet that it is necessary. Seems there are two schools of thought on the bov thing.

 

Would be the best place if you can get the correct diameter intake.

 

The pressure has to exit somewhere, and with a recirculated BOV, it's still going to exit the air filter. You might as well just plan on deciding whether to have slightly inaccurate MAF readings while accelerating (MAF post turbo), or slightly inaccurate readings when you let off the gas (MAF pre turbo). At this point in your situation, the only good thing a BOV is going to do is get rid of turbo surge/flutter and MAYBE help the stall thing due to air not going back out through the MAF. You can have the best of both worlds, but at the expense of more piggybacks, more tuning, and more $$$. IMO your best compromise would be MAF pre turbo and UNcurculated BOV. That way your MAF sees as-accurate-as-possible readings at idle & under heavy acceleration AND there is less of a chance that backward flowing air will stall your truck when you let off the gas.
Your biggest tuning chore is going to be equalizing your AFRs in boost while your ECU goes from closed to open loop fueling. My part throttle boost AFRs linger in the 13-14.5 AFR range, but when I open that throttle all the way and the truck goes into open loop, it tightens up in the 11-12 AFR range. This is all due to my FPR hose being attached to the intake manifold as opposed to ambient pressure like it came from the factory.
I still haven't tuned anything (if you don't consider tricking the FPR into increasing fuel pressure because of the positive pressure on the diaphragm from the intake manifold "tuning") and I'm still learning just like you are, so you are kind of on your own with going above what the stock injectors and ECU can handle and compensate for (5-6 PSI of boost) and having your truck make a nice and even transition between closed and open loop.

I will figure that out and fix it one day, but for now 1-3 PSI of part throttle boost in the 13-14.5 AFR range is not going to damage anything, and my stock fueling system is good enough for the boost levels that I am currently running

EDIT: and another good thing about putting the MAF pre turbo is that it greatly suppresses the sound of the turbo flutter. Everyone that rode in my truck said one way or another that it sounds like there's a giant pigeon under my hood lol

 

If he's tuning off a MAP, the MAF wont make any difference when in boost. MAPs don't do well for low engine speed/idle so you want to make sure the MAF is positioned correctly for daily driving use.

I miss spoke early. MAF pre turbo is only good with a BOV if its a recirc that dumps between the MAF turbo. Otherwise you wind up with option 1 pretty much.

 

In my opinion, a BOV dumping to atmosphere downstream of the MAF is the worst setup you can have. You're releasing a bunch of air that the MAF has already metered, which will cause the engine to go really rich and the ECU to go haywire.

The way I see it, there's two ways to do it. First, I'll say that a BOV is completely unnecessary, but if you absolutely just HAVE to have one, then you pretty much have no choice but to run the MAF post turbo, keeping the BOV upstream of the MAF. That way when the BOV opens, the air exits and never crosses over the MAF. Forget all the recirculating stuff. Several others, especially rear mount turbo guys don't seem to have an issue running the MAF post turbo.

If you run the MAF pre turbo, then the way I see it, you pretty much have no choice but to run without a BOV (which is perfectly fine). When you lift off the throttle, all the air isn't going to exit back through the turbo all at once. The turbo still has a fair amount of momentum, so the air in the charge pipe will "leak" out past the turbo instead of rushing out all at once. The pressure reduction will look like this:

 

I agree the BOV is unnecessary. I also agree with the BOV placement. You will be dumping measured air. Most ppl agree that if you have to run a BOV, it MUST be mounted upstream of the MAF, as far away as possible. I disagree, the best way is to mount the MAF downstream of the Turbo and circulate the BOV to dump b/t the MAF and turbo. This will actually cause you to run a little lean when the BOV releases, but since you are off the gas, you should be ok. You won't have to worry about stalling or sputtering engine.

 

It's going to run a little rich in certain spots regardless of where you put the BOV and regardless of you even use one, and in my experience that misreading is NOT a big deal. The most important time for the MAF to get proper readings is when the engine is under heavy load. Without the BOV, the air is STILL going to come back out of the turbo and go back through the MAF, making it double read and show rich. This phenomenon last a maximum of half a second in my experience.

 

I'm not going to use the bov. Unless someone knows something incredible about them, I agree that they are not needed from what I have read. Maf is going pre turbo.
Had to work on some lighting yesterday. Since I moved my license plate to the tailgate I had to mod up lighting for it. Came out nice. I'm also going to be putting in turn signal lights inside the fenders.

 

No BOV club here. The compressor surge sounds awesome too

 

That flutter gets me excited. If you're harder into boost it's like a screaming flutter. Awww yeah.

 

Whaaa? Guess I just have to be there. And I will!

 

You copy cat lol.

 

Absolutely! That's why many of us are here. To learn and get ideas from each other. Your idea rocked, plus it's way easier than risking breaking one of those damn side mirrors again. lol! Have to post my license plate mod light pics later. And the leds I'm putting under the hood to illuminate my hood vents.

 

It's definitely cool but I like sleeper mode

 

It's all good dude!
I hooked these up for $7.50 using some old wire and an alligator clip I had laying around

 

I'm half sleeper.......I ordered a 4 to 3" 45 degree reducer to place my Maf pre turbo. Need to get the oil drain welded in. Gio.....can I buy your extra oil pan?

 

I can't tell you for sure if that 45 deg is going to allow your MAF and filter to fit. Mine is a very tight fit. You may need to use a shorter filter