OK, maybe this is a newbie type question. Thinking of fabbing up an inexpensive turbo system for my 97.(I know, turbo=expensive, but bear with me) I have seen all roots and eatons and whipples have a suck through system due to design. i have seen centrifugals with blow through and suck through MAFs. I cannot find any of my mags that show how a turbo system is fitted. Would you use a blow through and the MAF sees stalled airduring boost conditions? or use a suck through and Tune according to that? yes i know that a tune is necessary for any turbo app. I know many turbo systems use a stand alone or piggyback ecu, but what about guys using the eec4s and 5s? Any ideas?

 

There are MAFs that are designed to be used as blow thru. But I have only seen blow thru setups on supercharged rigs. And due to tuning issues, a long stretch of straight intake tubing must be pre and post MAF for best results.

Typically, a draw thru MAF setup is much easier to tune. And I have never seen anything but draw thru on turbo setups.

I have a boosted SHO Taurus, and it uses a draw-thru MAF.

 

No argument, but its a challenge to get any length of straight pipe on the intake tract on either side of the mass air meter.

 

I completely agree. Thats one reason why people try and fail with blow-thru setups, and wind up resorting to draw thru.

Unless they are simply willing to deal with a marginal tune.

Also, proximity to the blower/SC as well as the throttle plate plays a big roll in how acurately the MAF meters air. Yet another reason why they go to draw thru.

 

My 98 STX 4,6L is one of the very few blow throughs that I know of. In fact I don't know if there is another one around. There are some tuning issues but a few tricks to take care of those issues. My MAF sits right in front of the TB and the AIT is infront of the Univer Blow through. The blow off valve is vented to atmosphere which is way cool. When I do my burn outs at the track, the crowd really likes the sound when I come out of boost. Sometimes it even scares people! I am right at 500 rwhp with this set up.

 

Flats man - My truck is slowly becoming a close copy of yours. Did you have to modify the Long Tubes to fit. I thought that only shorties were available for the 98 4.6.

[IMG][/IMG]

 

[QUOTE=Flats Man]My 98 STX 4,6L is one of the very few blow throughs that I know of. In fact I don't know if there is another one around. There are some tuning issues but a few tricks to take care of those issues. My MAF sits right in front of the TB and the AIT is infront of the Univer Blow through. The blow off valve is vented to atmosphere which is way cool. When I do my burn outs at the track, the crowd really likes the sound when I come out of boost. Sometimes it even scares people! I am right at 500 rwhp with this set up.

Sorry to get off the topic for a moment but you touched on something that I've been wondering about. The factory ATI Procharger intake set-up has the blow-off tube going back into the intake. The part it connects to is a source of some restriction. Many have changed the intake for a less restrictive system. So my ? is, does the blow-off tube need to go back into the intake or can it, as you say, vent into atmosphere?

 

Yes it can just vent to the atmosphere. no problem

 

Ok, so in theory then, one could remove the metal piece that the blow off tube connects to which is the cause of some restriction and replace it with another coupler of the correct diameter and allow the blow off tube to discharge into the air. Does this work on daily drivers and or just race applications?

 

Nope, you can't do that because you would be venting metered air assuming you have my set up. Your truck would not like that at all! lol I am real busy right now but I will take some pictures of my set up and post them for you. Basically if your are blow through, the hose that goes from your idle valve into the elbow just before your blower, has to be rerouted back to just infront of the butterfly on the TB. On my truck, the blow through is right in front of the TB so I had to drill a PT hole and put a AN fitting to accept the hose from the Idle air valve. Sounds complicated but it really isn't. All the air that is vented to atmosphere, is vented before it is metered. I will get you some pic in the next day or two.

 

Alright, but I don't want to highjack this thread so look for a new thread called "Reroute the blow-off tube" We'll talk more there. Thx.

 

The long tubes will fit the 5.4 without any mods but on the 4.6L I had to dent the tube by the starter and cut one of the tubes on the drivers side and reweld it with an extention.