4.0 ohv turbo hotsides

[59bisquik]

With a 91 4.0 and MAF, would running at low boost (5-6psi) work with a factory ECU? Would it need a retune or would a piggyback or standalone be the ticket? Looking for something simple, since it would need to be removed every two years for California smog check.

 

[gribly]

Again, not really nessesary. The whole pre-turbo exhuast system is under pressure, you're not relying on scavenging when you've got 10-20+PSI drive pressure.

That's not the point. When you have different amounts of resistance to flow for each cylinder, you have different amounts of cfm through each cylinder. You won't be able to tune it properly.

To 59bisquick - you can re-flash that ecu, get a dyno shop to do it.

 

[59bisquik]

Sticking with the 5-6psi range, would an injector upgrade be needed or would the tune be enough? I have a spare VF11 turbo off my Subaru sandrail just sitting around...

 

[AllanD]

That's not the point. When you have different amounts of resistance to flow for each cylinder, you have different amounts of cfm through each cylinder. You won't be able to tune it properly.

To 59bisquick - you can re-flash that ecu, get a dyno shop to do it.

You don't understand turbocharging.

almost NO factory setup bothers worrying about equal length flow path because it was discovered long ago that it simply doesn't matter.

It's all about pressure.

When the air is BLOWN into the cylinders the whole game changes.

Frankly I've never considered turbocharging a CologneV6

To me it just sounds like a bad idea.

If you ever hear that I'm going to build a turbocharged Ford 6cylinder you can assume
(God's lips to your ears) that I'm putting small (2.3T T-03's) twins onto a 4.9 and I'm doing
it in an F-series.

I think a 4.9TT running 8psi in an F-150 supercab would be "neat"

AD

 

[gribly]

Yes, it does matter. It just matters more on an n/a motor. Look, I don't want to get into a childish argument, but to put it simply - the "distance" I am talking about it more than just the physical length, you also have to account for turns, which add resistance - so you tack the bend's equivalent distance onto the length. Equivalent distance is the term for the amount of straight piping that would have the same resistance to flow as the bend does. Just because it's under pressure doesn't mean you can throw physics out the window.

The reason the factories don't do it is because manufacturers use cast manifolds, as it is impractical to sell a factory car with a welded manifold as they don't last as long. If you look at almost any turbo racing engine, you'll notice equal length manifolds, divided inlets, and all sorts of fun stuff that you say "doesn't matter." You even have to account for firing order when designing your collector, as you don't want say, one cylinder to have it's exhaust valve open at the end of a cycle with another cylinder opening it's exhaust valve, with these two cylinders having their runners on opposite sides of the collector, and you'll send a pressure wave back into the former cylinder, reducing efficiency of the whole setup and possibly pushing some of the exhaust gas back into the cylinder right before the valve closes.

Now, I know it's not the best idea to build a racing engine out of a 4.0, but any setup should be reasonably good to make it worth the effort. Which is why I am a fan of remote mounts on trucks. I sure hope you're not actually defending the manifold in this thread...

 

[gribly]

Sticking with the 5-6psi range, would an injector upgrade be needed or would the tune be enough? I have a spare VF11 turbo off my Subaru sandrail just sitting around...

I believe, but don't hold me liable for this - that turbocat ran without a tune or changing the injectors with two small parallel turbos on his explorer. I don't think a vf11 is worth putting on a motor that's almost twice the size of the motor it came off of. If you're going to go through the effort, do some research and find a turbo with a compressor map that suits your budget and motor.

 

[rocks]

Equal length manifolds do NOT MATTER ON A STREET CAR. You sir are a goober if you think that. Hell my Cummins turbo has a cast non equal length manifold. It makes 350hp 650 tourqe. 81 280zx non equal length. Subarus are the same. Only time you need one is for um pro racing, when you are trying to win for money. Equal length manifolds or headers do not really much on a NA motor unless you are trying to extract all the horsepower you can.

We are not talking about turbo racing engines with exotic collector designs. You are a arm chair / magazine racer. Go over to http://www.theturboforums.com/smf/index.php and look at the home made crap people put together and the times they run.

With low boost on a 4.0 it would be possible to plumb cold start inectors into the intake manifold with a hobbs switch to come on under boost. It is not ideal but it works, can also use a rising rate fuel pressure regulator. Look into how turbo cars were tuned in the 80s. The vf11 would be fine the 4.0 is dead by 4200 rpms anyway. Not like your gonna be spinning it to 8000 rpms like i turn my 350z motor. Just make sure you use a Wideband O2 sensor. You can get kit to build one with a gauge I think its call just another widerband or JAW.

 

[gribly]

rocks, I understand what you are saying - you don't need perfection, but take a second look at the picture of the manifolds that this fella was thinking about selling unsuspecting people and you'll understand my reaction to this mess.

 

[Hahnsb2]

rocks, I understand what you are saying - you don't need perfection, but take a second look at the picture of the manifolds that this fella was thinking about selling unsuspecting people and you'll understand my reaction to this mess.

I'm sure he saw it. Again, not a big deal.

Here's another one. I'm sure tuning will be a nightmare, if it even ran

 

[rocks]

You dont want it running back through the other manifold. Flip both of them and make a crossover pipe where both manifolds blow into the crossover pipe. Issue solved. I did see the pictures but again there are countless numbers of single turbo V engines without equal length manifolds.

 

[gribly]

You dont want it running back through the other manifold. Flip both of them and make a crossover pipe where both manifolds blow into the crossover pipe. Issue solved. I did see the pictures but again there are countless numbers of single turbo V engines without equal length manifolds.

I went off on a rant because AllanD said that the distance simply doesn't matter, and it does. It doesn't matter as much on some kludged together setup, no, but that is because there are going to be other factors bottlenecking it much worse. I'm not some elitist benchracer, I've used cast manifolds on all my own turbo builds, because the budgets for what I've done weren't enough to justify anything else.

That picture, Hahnsb2, is of a better setup. Something like that probably gave the OP his idea in the first place, but it's still going to have some drastic differences between the cylinders, especially the front two, which will be holding it back.

 

[donfordguy]

I'm sure he saw it. Again, not a big deal.

Here's another one. I'm sure tuning will be a nightmare, if it even ran

that picture is how the chevy diesels are set up

 

[RacinNdrummin]

You don't understand turbocharging.

almost NO factory setup bothers worrying about equal length flow path because it was discovered long ago that it simply doesn't matter.

It's all about pressure.

When the air is BLOWN into the cylinders the whole game changes.

Frankly I've never considered turbocharging a CologneV6

To me it just sounds like a bad idea.

If you ever hear that I'm going to build a turbocharged Ford 6cylinder you can assume
(God's lips to your ears) that I'm putting small (2.3T T-03's) twins onto a 4.9 and I'm doing
it in an F-series.

I think a 4.9TT running 8psi in an F-150 supercab would be "neat"

AD

While I agree with you that its nearly inconsequential for 99% of turbo setups to have equal length "tuned" setups, that most wouldnt even notice and its not worth the extra cost, you are wrong in your thinking that it doesnt make a difference when it is executed properly. Boosted engines are no different (For the most part, obviously there are subtle differences) than N/A engines when it comes to pulse tuning and pressure waves, as well as general flow through a given manfold or port. The only thing boosting does is increase the pressure ratio at which the air flows through the port, not the actual flow itself. A port, manifold, header, etc that flows, lets say 200 cfm at 14.7psi absolute (atmospheric pressure @ sea level) is still going to flow 200 cfm at 30 psi absolute or whatever other pressure you can think of. The only reason you get more air into the cylinder, is because the air is compressed. So with that said, if you can move Air/Fuel in or exhaust out at a faster rate (More CFM) your going to see even more benefit with boost. Because 214 or 230 cfm at 14.7psi is exponentially less air than 214 or 230 cfm at 29.4 psi (2:1 pressure ratio). Porting, manifold design, sizing, etc, all work just as well if not moreso on a boosted engine as an N/A engine, However, something as low performance as the 4.0 OHV, your not going to see a world of difference with tuned setups, your just better off with something that will get the turbo to boost and the engine to put out more power than stock, plain and simple. Size the turbo to put out peak boost around the torque peak, and not run out of steam or superheat the air by redline, and your going to have a setup that will put a smile on your face, regardless of what style manifold your running...