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Discussion Starter · #1 ·
Well I've been searching for info and haven't found much really, so i thought maybe you guys could help since this seems to be a pretty good forum (and my girlfriend reads it for about 6 hours a day)

anyhow, I've recently acquired a first gen ford explorer w/ a 4.0 OHV and automatic trans. oh, and a t-4 60 trim turbocharger. well i've got the exhaust all plumbed up, the oil routed, the air pipes made, and today took it for its first test-driving. ....and it ran like crap. below is a video.

once the turbo spools and the boost starts kicking in, and/or it gets above about 2500rpm, it starts running bad, looses power and sounds generally bad.

a brief summary of the engine, it's bone stock (except for the turbo), but here's how it's built. it's a 60° "cologne" v6 engine block, 90tm cast iron heads, hyd roller cam, 9:1 compression, and it has MAF fuel injection.

so, why does it run horrible as the boost kicks in, is there something i need to modify, change or tune differently?

i'll post up some close up pics and stuff if anyone wants to see them as well.
 

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MM's Ford Truck Guy
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yes a tune is very neccessary cause you need more fuel for that boost to get a better A/F mixture
 

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Discussion Starter · #4 ·
Well, that's what i was leaning towards, but how to i go about doing this? i'm a noob to turbos, and i've never modified a fuel injected vehicle before (done quite a few carb builds, but changing jets and metering rods is a little different than FI)

do i need bigger injectors? i was thinking it's probably the that the ECU isn't setting the pulse width for enough fuel, more than that the injectors wont inject the necessary fuel. what about fuel pressure, would increasing that help anything? do i need to get a "chip" or something?
 

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MM's Ford Truck Guy
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ok look what you need is a set of im gonna guess 42 lbers from ford racing and get a matching maf which would be a lightning maf (90mm) and look on sct's website to get a idea how much it will be for a Tuner
 

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Discussion Starter · #6 ·
So i have to match the MAF with the injector size? or do i just need a maf capable of measuring the increased volume of air? i believe my stock injectors are 19#

is there any concern about impedance/electrical load on ecu change from switching injectors?

are the injectors and maf bolt in swaps? what about a stock maf from a 5.0, 4.6, 5.4 etc (or some other junkyard-findable vehicle)? or is the lightning one a direct swap (is the wiring different etc?)

i found a tuner on that website, but it says it flashes via obd-II port, and this is an obd-1 vehicle (1991) yet it also says that it works with "most 1989 and newer fords"
(here is the link SCT Automotive Performance Products )

sorry for so many questions, but you're help is appreciated. taking me in the right direction at least.
 

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MM's Ford Truck Guy
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as far as your injector size goes i belive they are 16's im not sure but thats what 3.0's are and no you wont have to worrie about electrical load it will be fine and as far as the maf from a lightning working i have not a clue if it will be able to plug in to your factory plug for your maf but i dont think it will since your xploder is a obd1 vehical so i have not a clue what you can do for a maf.
 

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Discussion Starter · #8 ·
Yeah, i'm starting to think that obd-1 is going to make things a pita. is there a way to convert to obd-2 easily? i know later versions of this same engine came with obd-2. i wonder what parts i would have to swap (wiring harness as well?) etc.
 

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MM's Ford Truck Guy
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i have no idea man i dont mess with explorers lol
 

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You should check things out on turbomustangs.com. There's plenty of parallels with the Explorer, I'm sure.

How is the intake laid out? Blow-thru or suck-thru MAF configuration? How much boost are you getting?

I would recommend suck-thru because some MAFs don't like blow-thru and give bad readings as soon as the turbo spools. Not sure if the stocker behaves this way.

As far as fuel requirements, as long as the MAF is getting an accurate reading the ECU will attempt to deliver the proper fuel mixture. You might be running the limits of your injectors and/or fuel pump. An air/fuel gauge can tell you if you're running lean, such as a wideband. Or, simply hook an air/fuel gauge or voltmeter into the O2 wires going to the ECU. If you're going into 0.9V and up at WOT, you're running lean.

Unfortunately, I can't view videos from work, so I can't make a guess on what's wrong.
 

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You are definitely running lean.

You are introducing all of that air into the engine, but the stock fuel system cannot supply enough fuel for it to run properly.

Until you take care of the fuel situation, stay out of boost or you are going to burn it up.
 

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Discussion Starter · #14 ·
You should check things out on turbomustangs.com. There's plenty of parallels with the Explorer, I'm sure.

How is the intake laid out? Blow-thru or suck-thru MAF configuration? How much boost are you getting?

I would recommend suck-thru because some MAFs don't like blow-thru and give bad readings as soon as the turbo spools. Not sure if the stocker behaves this way.

As far as fuel requirements, as long as the MAF is getting an accurate reading the ECU will attempt to deliver the proper fuel mixture. You might be running the limits of your injectors and/or fuel pump. An air/fuel gauge can tell you if you're running lean, such as a wideband. Or, simply hook an air/fuel gauge or voltmeter into the O2 wires going to the ECU. If you're going into 0.9V and up at WOT, you're running lean.

Unfortunately, I can't view videos from work, so I can't make a guess on what's wrong.

I'll check out that forum now as well. I like you're thoughts it sounds like you have a pretty good idea of how this stuff works.

I've got the MAF sensor before the turbo (suck through) my thoughts were with yours about the MAF reading the increased air and telling the ecu to inject more fuel, which is why this problem has me so baffled. it starts to run bad with even just 2 psi of boost (pretty much as soon as the boost gauge sweeps past the 0 it starts running worse, sounds lean to me) I'll try an o-scope or high impedance volt meter or something on the o2 sensor in the morning and see what happens.

as far as i can tell, the ECU does nothing to account for the increased air volume entering the engine. i suppose that could suggest that the MAF is bad and the ECU is just using a fuel map or something?

i dont suspect that the fuel system cannot keep up, because it gets lean immediately when boost hits (and i know it must have SOME headroom) and not only that, it's lean even with only 2500rpm.. i'm sure no boost at 5000 rpm WOT eats more fuel than 2psi at 2500...
 
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