StAndrew's Build

I still think there is a vac leak somewhere. Exhaust leak wouldn't do that and it would have to be pre O2 anyways.

And he is right in terms of running the MAF pre boost. It can be done just fine. That's how the 7mgte supra motor works. MAF pre turbo. It works the same, just instead of the air being pressurized it just moves very fast past the MAF.

I mean, think of how the supercharger runs on our trucks. Boost happens post MAF.


Granted I've never seen a taco do that that's turboed, but it's an interesting thought..





But I agree with you he didn't have to be such an ass hat in his delivery of said information.

 

Listen Mike, I appreciate your input but don't agree with a lot of what you think. If I'm wrong, its my loss but please feel free to weigh in as you see fit, just please be mature about it.

 

I don't know how Id run this MAF on a 4" intake though It won't read accurately. I would need a different length MAF to position the sensor correctly.

I plan to run either the pressure test or smoke test, just need to look around locally for some help.

 

You can run maf on the pressure side. I have mine pressure side just because it was easy for me. I kinda like it like that because the blow off doesn't make me run rich. Only down side with stock why is you get this weird lean condition until the intake temps go back down. You want stock maf diameter. It takes a good chunk of power to max out the maf. By the time you get there your piggy back should have a voltage clamp and run off speed density fueling.

 

Well on the supra, the MAF was about 6" long and had a 8" tube from the turbo to it then the air filter.

You don't have an intake tube?? I guess I need to look at the bay shot again.

Edit. Hike way tighter then I thought.

Well that idea isn't totally feasible then without a custom tube made and other stuff.

Get the vac test done and that'll be the best thing to do before doing ecu stuff

 

I am... you ignore a lot of people and they're tired of helping you

The blowoff valve could also cause CELs and shitty running characteristics if it's venting to atmosphere air that has already been metered.... depending on how it's set, it can flutter open at idle after the engine is warmed up and RPMs drop

 

And my intent on the MAF, if you rule out everything else, it may be worth your time to temporarily rig it up on the suction side and see if it makes a difference

 

Yea, I actually took that stuff off so the filter goes directly to the turbo. It was very tight how I had it and this gives me a bit more room. I think the MAF is good where it is. Remember, the truck was running great until I picked it up from the stupid offroad shop

 

Dayum this crap is getting overly heated and complicated for no reason. Regardless of who has the most experience, the MAF location (whether post or pre turbo) is not going to make the truck barely run at idle and soft acceleration. That's absurd. No need for air compressors and smoke, just rig up the intake to where you can put a section of it over your mouth so you can blow to see if it's air tight.
Chris, what EXACTLY did that offroad shop do?

 

Haha, chill, I just put him on *ignore* for now. Don't need this thread going stupid.

The shop just welded some rear shock mounts afaik. I'll get to the truck Friday; just found out I start work Monday

For now, got some work to do on the new car (of course); O2 sensors, spark plugs, and brake pads should put me back in business.

 

What about the cylinder with an open intake valve preventing pressure buildup for this check ?
Most people cap off the piping at both ends, then pressure check by putting a Schrader valve in one cap (use pvc caps), that way you know all piping is good... the MAF can indeed affect the way the truck is running, if it's not able to meter properly, seen it happen

 

Either the intake valves or exhaust valves are going to be closed at all times. If the engine stopped on an intake cycle, then you won't hear hissing as you blow... But rather a very very slow release of air from the small gap in the compression rings (I've had to do it plenty of times on my truck). His MAF is NOT going to get an incorrect reading being mounted in front of a straight 3" pipe like it is set up now without the thing being dirty or defective. I have been running my MAF post turbo for two years now and nothing is wrong. The thing is meant to have a straight pipe in front of it.

 

The MAF position shouldn't matter unless you are running a BOV (Im not). With a BOV, the MAF before the turbo would prevent the BOV from affecting the air flow over the MAF however, I would have to find a compatible MAF that is fitted for 4" piping. If I put the OEM MAF before the turbo right now, it would run like shit, probably even more so than now.

In all honesty, on a turbo, the best position for the MAF is the trash. MAP is much better for boost.

As I said before, Im capping my MAF voltage to keep the ECU from seeing any boost via the MAF and compensating via the tune off the FIC MAP and extra injectors.

I appreciate all input and advice, even from you Mike. Not going to get anything done on the truck until at least Friday though.

 

New car

 

U Should boost the Honda too. Haha

 

Ahh another s13 owner
I gotta 92 with an sr in it
Yours a hatch or coupe?

 

No BOV/Recirc valve ??? How much psi will be at full boost ? And you're running a China cheap turbo ? Not a smart idea, but that's neither here or there.

If you're playing around with limiting MAF voltage, therein MAY, i say MAY lie your problem... The way you're describing is not good... The ECU relies heavily on MAF input to determine fuel injection, it fine tunes based on O2... that's why when O2 sensors fail, cars run rich, the default failure is rich to prevent detonation.

Maybe you're not describing it well, but you would never want to prevent the ECU from seeing any boost, unless you were running a piggyback fuel controller like an APEXi S-AFC, but that doesn't blind the ECU, it just tricks the ECU in order to obtain the desired result.

valves are NOT closed at all times when the engine stops in the middle of a cycle, that's a shitty test for a vacuum leak.

1993 Nissan 240SX, SR20DET motor, T3/T4 turbo, 10 psi, 257hp at the wheel, hot wire style factory MAF, plumbed inline with turbo.... MAF failed after 12,000 miles... installed on suction side, allowed car to run, still defective sensor

Saw similar symptom on a WRX as well

I didn't say it WOULD be faulty like that, I said it CAN, meaning it's POSSIBLE... I've seen sensors with enough variation in the manufacturing they just don't run consistent in certain setups.... You're an expert I see, since you have one turbo vehicle

And as I stated, MAFs actually get a more accurate reading and improve throttle response when mounted within 12inches of the throttle body, I said some sensors don't like it.... read much ???

 

Let's hold on a second. "Controlling the MAF ".... that would have to be done with the FIC. Is the FIC still installed, or not? I swear I thought you had said it was removed. Trying to get a basis of where the truck is right now.



Side note* Turbulence across the MAF is worse than pressure, at least in low boost scenarios. Never went over 15 psi with mine, but it never had a problem. Turbulence however skewed all sorts of stuff up. Location, proper diameter, BOV before (if MAF is post turbo), BOV after (MAF Pre turbo, and BOV MUST recirculate or there with be a vacuum leak every time it vents ), flow straightener (highly recommended is MAF is in pressurized tubing) can be used on a pre or post turbo setup.

 

FIC is out, yes. Not controlling; capping at about 4.3V. I ran it WOT stock and measured the highest output volt on the mAF and capped it there (of note, while there is no tune, Im using a different profile with no MAF cap to insure max fuel just in case, however, Ive yet to go past 2500 rpms).

I'm going to recheck the vacuum tomorrow probably. I don't think its under the hood, might be the vacuum line that runs to the cabin

I'm also going to re-tighten the V-Band clamps and double check the MAF sensor (and may even replace it with the old one I still have). If that doesn't solve anything, Ill start taking voltage readings on the ECU.

Anything else I should be looking at?