hairdryers

[1990LTD]

I'm curious about turbocharging in general,



twin vs single turbo on a motor with two cylinder banks - I see single turbo V motors but there's gotta be something I'm missing. I would think sticking a hairdryer on one exhaust side would make it flow differently but it must be compensated for.


in general, what dictates the size of the turbo you put on your motor? CID? overall desired power? power that the motor can safely handle? intake or exhaust flow of the motor you're modifying?


regarding boost - can you "dial it back" as easily as it sounds?

[Grand Marquis GT]

There's a lot of things to determine what you need.

As for a single on a v-type engine, they use a Y-pipe. Simple.

[1990LTD]

What are some of the determining factors?

[1990LTD]

another n00b one: how does one build a motor for boost? the bottom end, that is. boost seems like the kind of thing you want to plan for

[1980c10]

Forged everything lol. Go to www.turbomustangs.com and start reading. Tons and tons of super knowledgeable guys over there, lots of tech info and alot of good builds to browse. But careful turbochargers are a sick disease once you get it, they won't let go lol.

[Grand Marquis GT]

What he said.

I am looking to do a TT 4.6 DOHC in my truck, and I still have a LOT to learn...

[P72Ford]

You need to read. There are books and forums.

When you think you understand, you have no idea. And I am not claiming to know a damn thing about turbocharging, proper. I do know some things about fluid mechanics, though.

People talk about budget turbo builds; but to build big power (and you certainly can), reliably, takes big dollars.

I fooled around with boost, albeit from a centrifugal supercharger (different animal), and spent $3800 without opening the engine up. Granted, what I built was really nice, but I'd have had to spend another $5000+ to build the engine to safely handle the boost, $2000 on an AWIC system, $1000 in the clutch, some work in the rear end...

You get the point.

[1990LTD]

You need to read. There are books and forums.

When you think you understand, you have no idea. And I am not claiming to know a damn thing about turbocharging, proper. I do know some things about fluid mechanics, though.

People talk about budget turbo builds; but to build big power (and you certainly can), reliably, takes big dollars.

I fooled around with boost, albeit from a centrifugal supercharger (different animal), and spent $3800 without opening the engine up. Granted, what I built was really nice, but I'd have had to spend another $5000+ to build the engine to safely handle the boost, $2000 on an AWIC system, $1000 in the clutch, some work in the rear end...

You get the point.

I've got a vague idea. I know the $$ part of it is true...even the "shit" ebay turbo kits cost more than you could buy a decent box Panther for around here. The fabrication seems to be the expensive part of the actual turbo build but that's without even "cracking the case"



It sounds addictive, though. I mean, if you're rebuilding the motor and drivetrain anyway, why not build it with a turbo in mind? My drivetrain is getting rebuilt eventually but I've got time between now and then to research.


Will a 302 block just get to the point where it won't have it anymore? Obviously a 351w is a stronger specimen to start with but I'm just brainstorming about now. Assuming we built the drivetrain, rotating assembly and valvetrain to accommodate the level of boost (14.7 for argument sake) being fed into the cylinders, would a late model roller block eventually just say "nope" and fail spectacularly?

[Crownvicman289]

14.7psi of boost would put you well into block splitting territory on a 5.0, I'd definitely get either an old 302 block or a 351W block. Of course a boosted V8 would rip the guts out of an AOD so you have to rethink that too. Then you need a fuel pump, injectors, possibly rails(?), and a way to tune it. Then you need to get it tuned assuming you can't do it yourself. And you haven't even bought the turbo, intercooler, or plumbed it in yet. You might get it all together and decide you want a larger/smaller exhaust housing to hone in on the point you want it to spool up, or maybe it was choking the top end so you get a bigger housing and deal with later spool. It's not cheap by any means. I think 88what's his name says a T70 is a decent turbo for an HO so there's a start. You flip the headers upside down, plumb it in, and do everything else I mentioned. Piece of cake.

[1980c10]

Also boost is more a resistance deal. 14lbs of boost through a stock motor is different then 14lbs on a car with huge heads and intake setup. Also completely different is the amounts of boost from a small turbo to a large turbo, for example say a t3 moves 700cfm of air on a certain motor at 10lbs of boost then say a t6 based turbo on the same engine moves 1400cfm at the same 10lbs. I hope that makes sense.

[Crownvicman289]

I was being generic with the boost pressure. Cams can also play a role in boost pressure, like 1980c10 said it's about resistance. P(ressure)=V(volume)T(emperature). If you increase the volume of air being pumped, you increase the pressure. If you increase the temperature, you increase the pressure. A smaller turbo creates more heat than a bigger turbo, so it moves less air at the same pressure.

[1980c10]

I know you where being generic. The comment was toward 1990ltd to help inform him.

[1990LTD]

The 14.7 was an arbitrary number. I do not plan to put 14.7 psi of boost (or any for that matter) through a stock 5.0 - I am just curious about the concept in general, and am wondering at what level our blocks in particular, assuming everything BESIDES the block was built for it, would just give up.

14.7 might be block-splitting territory but I'd like to know where the border of that territory lies.


thanks guys!

[P72Ford]

14.7 is atmospheric pressure at seal level; 1 atm. Folks use that as a benchmark, if you didn't already know that.

I was being generic with the boost pressure. Cams can also play a role in boost pressure, like 1980c10 said it's about resistance. P(ressure)=V(volume)T(emperature). If you increase the volume of air being pumped, you increase the pressure. If you increase the temperature, you increase the pressure. A smaller turbo creates more heat than a bigger turbo, so it moves less air at the same pressure.

I'm not sure where you got this P=VT equation, but it is false. Whereas there is a relationship between the 3 (which may have been your point), they are not related in that way. Pressure is directly porpotional to temperature, and inversely proportional to volume.

It seems like you may have been alluding to an ideal gas law; either Lussac's, Avogadro's, Boyle's, etc laws. Or more commonly, an ideal gas law. PV=nRT, (sometimes PV=kNT). Pressure * volume = the molar quantity of the gas*the universal gas constant (8.314472 J/k*mol; I believe those are the units)* the temperature. When you have a gas that is actually multiple gasses mixed (which is typically the case), you have to use partial pressures and such to work out this equation, which adds a little complexity.

Understand that the ideal gas law(s) aren't always appropriate. They provide good approximations under some circumstances, and poor approximations under other circumstances. When you have a higher pressure, lower temperature, gas or gas mixture is when your results are going to become inaccurate; that behavior is outside of ideal.

Also, the ideal gas law is primarily a static gas law. When we are in the business of a flow, like we would be with a boost application, the law becomes inappropriate. It is really inappropriate because we are compressing a gas, which the ideal gas law does not take into account. The IGL can be modified with a compressibility factor, but in my opinion, there are better ways to go about it.

Its good to have an understanding of basic fluid mechanics. An increase in pressure does not mean an increase in flow, flow velocity, etc. Some people fail to get past this trivial aspect, thinking that larger boost numbers mean more power. Lowering the resistance to flow will drop pressure, but provide a much better volumetric flow rate.

There is alot to know, really.

[Crownvicman289]

One thing to point out is that if you go as deep as P72Ford has illustrated, you're making serious power, as even a crap turbo setup on a 5.slow would satisfy most people. 500ish hp is generally accepted as block splitting territory for the 5.0. Some split them sooner, others later. I don't know how boost plays into this because even though it sends dynamic compression through the roof, the revs of a boosted engine are generally lower than a balls out N/A build and I'm reasonably certain the revs are what shake that bottom end loose.