The theory I understand is that the more boost you make, an increasing portion in measured PSI comes from the thermal expansion caused by compressing the air in the intake stream. Cooling that off will reduce some of that pressure but there are still more air molecules getting to the engine. A loss of 1-2 PSI has been reported over on OBN, but not the ~7 PSI and up that some have claimed.

What I don't understand is how a larger intercooler with more flow capacity can cause a restriction on the intake compared to a smaller one. I understand that line of thinking for a turbocharger, but an intercooler isn't really the same thing.

 

Mother nature only has one set of laws. Bigger surface area means bigger heat transfer which means lower temperature. The volume of the cooler will slow the pressure rise through it, which would be insignificant when compared to to higher HP possible.

Almost forgot, the bigger the cooler, the less pressure drop through it.

 

You are kinda answering your own question. Think, cooler, denser air = less space that piece of air takes up hence the lowering of pressure. Think about it the other way, if you compress air to a higher pressure you get heat!
I think alot of people talk out there monkey butts when it comes to effeciency of the different coolers, not fully understanding what they themselves are talking about. But sometimes they're convincing yet can't show any data to back it up.

 

My only thoughts on that much pressure drop would be to many tight bends in the piping.
Intercooler to small for the flow.
Pipes to small.

If the cooler air is reducing the EGT's far enough, that could mean the turbo is not spooling as well, but more fuel to go with more air would fix that fast enough.

 

I think I might be the guy who said the ATS stuff was in stock. And it was. I did actually get put on a waiting list and after calling ATS and bugging them for weeks, they finally called me and said they had the upgrade kit in stock (turbine housing, outlet housing and down pipe) and I gave them the card number and they shipped it right out. Trouble was when I found out the fits on the y pipe and the up pipe were bad and didn't want to put new parts on old worn out ones so I called ATS and they had those in stock, along with a new cross pipe. So basically the whole system is new with the exception of the compressor housing and shaft. The gal I talked with mostly was Kelly I think. I can check for sure on my receipts and post it. I did hear talk recently about ATS running till the tooling goes bad and calling it quits. That was long after I got my stuff. I know I made a post on here saying the stuff was in but evidently they only had one or two kits. What a mess. Sorry for any confusion. What a coincidence, my truck was one of the last to roll off the assembly line with the IDI and now I got one of the last upgrade kits for it.

 

Oh ya, my understanding of the whole "lag time" from an innercooler is basically it's like blowing up a small balloon and a large one. With an IC there's more volume to fill and build up the pressure in so it's gonna take a little longer. Crap. I also forgot why I hoped on here to begin with. I lose oil pressure under acceleration. Running just the dummy gauge but it's up where it's always been cruising down the road but when I load it up, pressure drops. Not out of the "normal" range but clearly drops. Oil pump going bad or any other experiences?

 

What you guys are saying make sense and I would fully expect to see a slight drop in 1-2 PSI from reduced thermal contraction alone.

The part that really had me confused all to heck was the assertion that big intercoolers are automatically "less efficient" but no real reason was given. I can understand lag time since the more pressure vessal volume between the compressor and intake - the more lag, but once its spooled there shouldn't be any difference in boost pressure (other than the slight drop fron non intercooled). Huge intercoolers might be a waste of space and money on engines that rarely boost above 15 PSI but to eat up 7 PSI of boost? That sounds - "off".

 

If a turbo was a positive displacement volume pump, I could see the pressure drop.

But with it being basically a fan, I can't see the reasoning behind an effecient intercooler dropping the pressure on a pull.
Yes I can see the spool time being slower, more volume to fill with charge air.
But once the turbo is spooled and the charge air boost level is reached, the difference should be minimal.

One thought did occur though.

On flat ground where you would only see much boost would be while getting up to speed.
So the turbo lag would appear as lower boost pressure.
After you were at speed, the increased air density would also mean you needed less pressure to maintain speed, hence the apperance that less boost was being produced.

Get that same vehicle on a big steep hill where you are into the throttle for a much longer time with the engine working pulling the hill, and the apparent drop should be much less.

I see this constantly when I drive down the interstate here.
5 or 6 PSI going downhill, 20+ PSI going up the next hill maintaining 70 MPH with even a very small load.

So the bottom line, non intercooled you run down the highway at 10 pounds of boost at a given speed.

Then you install an intercooler, the denser air means you only need 4 PSI of boost to maintain the same given speed.

So does that mean you lost 6 PSI of boost or the increased air density increased the effecieny enough that 6 PSI less boost was required?

I think it is more the second option than the first.

As far as the oil pressure goes, I would question the oil pressure sending unit before I questioned the oil pump.

 

Thats what I'm thinking. The engine is likely still getting more air but the measured boost isn't as much. Although still, other than initial lag, there should be no drop in performance once you have the fuel flow, boost and EGTs were they need to be at constant load (long hill or long heavy acceleration).

I wonder if you might actually see a drop of about 7 PSI in your case simply because you have so much boost already. But there should still be a gain in performance provided you can fit everything in there properly.

So I guess we are in agreement that an oversized intercooler will not acutally be less efficient other than increased lag time (which can still be a real problem depending on the application). That question was really bugging me.

Reading accounts from guys over on OBN that have towed heavy loads before and after intercooling, the indicated 2 PSI drop is noticable and lag does seem to be longer on the gauge but pulling power and off idle response was reported to still be better. Typically those trucks used to peak at around 15 PSI and now pull better at 12~13.

 

All I can say for sure is this.

I don't have a temp measurement before and after the turbo on my IDI so I have no idea how hot the turbo is making the air.

But I can tell you, I wish I could supply the same temperature air to the engine as I am seeing when the outside temp is about 15 below zero.

If I could get air that temp into my engine at an outside temp of 90 degrees, I would be more than happy to lose 7 PSI of boost.

Even with my injectors and IP settings, no black smoke at all at temps below -10 degrees with my ram air hooked up.

I am thinking hard about an intercooler on my Stroke.
If I put one on, I am also wanting to put temp sensors in the turbo outlet and intake inlet to see how much temp drop I see with the intercooler.
Since I already have an intake air temp sensor, and boost levels close to what I am running on the IDI I could figure out something close to how much heat the turbo is adding to the charge air at a given boost level and how close to ambient temp the air going into the intake after the intercooler is.

 

In all honesty, I probably don't even need one on my truck considering how light my truck usually is. Even if I were to go with an intercooler some day, a turbo rebuild or swap to a better setup would probably be in order becasue I am currently just below the boost thresh hold needed to really take advantage of an intercooler.

I wonder what a water cooled center section for the turbo would get me. I have a couple used ones....

 

I wonder if this is one of those things where way too much thought is being put into it and it's time for a beer and some dirt. LOL Given the age of the truck, odds are it could be the sending unit. Gonna give her an oil and filter change first and see if that makes a difference. I've been looking at innercoolers for my truck for quite some time but don't want to get into it till I have the time and money to get it done right. I'm still looking for the piping/ducting to get the monster K and N filter put on that I have. Biggest hassle has been the sharp bend that needs to come right off the turbo and then have to step it up to the 5" opening in it.

 

intercooler is never a bad idea. gives you the room to upgrade later while keeping your egt's safe. im still looking to keep mine in check under full load. cant wait to get my gears.

 

Since we moved to the high desert, I want to keep things as cool as possible at all times. I've noticed my tranny temp runs a lot warmer here than in WA.
Some days it hits 205 degrees. In WA it always ran between 165 and 185. Heat is the enemy to watch for in any application of a rig.

 

Crew-it,
Do you also notice the engine temp running higher as well?

If so, that could be the source for your lower oil pressure readings.