Installed DM "new" 7MGTE Intercooler.. question about boost...

[Grandavi]

Okay.. so after 3 days of fiddle-phuquing got my Driftmotion "plug-and-play" intercooler installed. I had to make a manual to map out the pipes because there is no instructions at all... lol.
AFter playing around with the 3000 pipe replacement (which didn't fit properly) and its attached pipe to the fender, I could not get it to go in at a proper angle without cutting out some of the inside fender (cut and repainted... ). After all that work.. went back to the custom pipe I had with the HKS 3000 pipe (which is oddly larger than the supplied hardpipes). The supplied pipes were sitting too high, plus the BOV was directly above where the hose needs to go to reintegrate.. which wouldn't work.

Therefore.. no SSQV BOV on the car, just running on stock BOV until first week of april. Getting a mount welded onto my custom pipe that sits a bit farther down. Had to move the rad overflow to under the headlight and put the oilcooler on the upper front part of the intercooler core. All fits nicely now and is tucked in good. Couldn't use those 2 supplied pipes for reasons listed along with the fact that they sat too high for my tastes. Ah well... almost done.

QUESTION:
I noted that driving the car now (still stock BOV, but all hard piped and intercooler installed) with the boost controller disabled (just running on wastegate), I only get 7 lbs of boost whereas I used to get 10 pounds on the 60-1 CT26 wastegate.

Anyone know why that happens?


Thanks!


**been thinking... is this perhaps due to the cooling effects of the intercooler along with the increased airflow potential? (meaning... cooler air = denser mixture). I haven't turned on the boost controller yet, so I am guessing that until I do I will be at a 7lb boost at the wastegate for some physics reason... I thought the pressure drop was 0.5 - 1.5 lbs max... this is more like 3.0 lbs.

 

[hvyman]

Could be pressure drop in the bigger ic pipes.

 

[Supra NA-T]

yea sounds like bigger pipes could drop the pressure a bit.

 

[Grandavi]

I'm not fluent enough in turbo/intercooler physics.

The wastegate is (normally) sprung activated set to a certain pressure?
I thought my 60-1 ct26 had a 10 psi wastegate because that's my max boost with a stock intercooler (not fuel cut related... I never hit that)
Trying to understand how the bigger pipes and core would drop my max boost by 3 psi. Is it air flow?

No leaks btw, I double checked

 

[IJ.]

The extra volume in piping won't drop the maximum boost it will only change the response time to reach it.

 

[Grandavi]

Hmm, odd then. I took it to redline in second and third, it wouldn't top 7 psi. Wonder if the hks boost controller is metering somehow even though I am running it in display mode only

 

[Dan_Gyoba]

Bigger intercooler means cooler air. Cooler air is less pressure.

The stock setup takes pressure from the turbo outlet and directs it to the wastegate, so pressure is "read" before the intercooler. A bigger temperature drop means a bigger pressure drop as well, so if your boost pressure goes down from changing only the intercooler, it means that the intercooler is working well. You're probably getting the same mass of air, but at lower manifold pressure.

The other possibility (Though highly unlikely) is that the intercooler is more restrictive, and therefore a greater pressure drop. I really don't think that's the case though.

 

[Grandavi]

After thinking about this... what I am wondering is, how the overall performance is impacted in "real terms".
Boost isn't all about pressure (if I understand correctly) its more about air flow. However, the pressure does come into play when considering the turbo as an air pump.
So, with no real restrictions in my intercooler any longer, I am flowing more air and cooler air than previous (with the stock intercooler). So, when my turbo is topping out at 7 psi on the wastegate (no boost controller involvement) now, I have lower pressure, but there is more air involved?

That's the thought that is confusing me, because the pressure "compresses" the air into the chamber with the fuel (you can only fit so many "air" molecules in with the "fuel" molecules.. so you have to press them together to get them to fit in the combustion chamber). So, in comparison.. is the 7 psi I read on my gauge accurate? And if it is, am I getting similar performance to the previous reading of 10 psi on the stock intercooler?

Just trying to understand how the numbers factor in correctly. Its a little confusing because I'm dealing with temperature variances along with increased flow.

 

[Supra NA-T]

Just hook up the damn boost controller. no seriously was looking on the net for some answers and came across this. Dunno if it helps or not.

The difference in pressure required for a given amount of air to move from turbo to intake manifold is an indication of the hydraulic restriction of the intercooler, the up pipe, and the throttle body. Let's say you are trying to move 255 gram/sec of air through a stock intercooler, up pipe, and throttle body and there is a 4 psi difference that is pushing it along (I'm just making up numbers here). If your boost gauge reads 15 psi, that means the turbo is actually putting up 19 psi. Now you buy a PT-70 and slap on some Champion heads. Now you are moving 450 gm/sec of air. At 15 psi boost in the intake manifold the turbo now has to put up 23 psi, because the pressure drop required to get the higher air flow is now 8 psi instead of the 4 that we had before. More flow with the same equipment means higher pressure drop. So we put on a new front mount intercooler. It has a lower pressure drop, pressure drop is now 4 psi, so the turbo is putting up 19 psi again. Now we add the 65 mm throttle body and the pressure drop is now 3 psi. Then we add the 2.5" up pipe, and it drops to 2.5 psi. Now to make 15 psi boost the turbo only has to put up 17.5 psi. The difference in turbo outlet temperature between 23 psi and 17.5 psi is about 40 deg (assuming a constant efficiency)! So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost.

 

[IndigoMKII]

Bigger intercooler means cooler air. Cooler air is less pressure.

The stock setup takes pressure from the turbo outlet and directs it to the wastegate, so pressure is "read" before the intercooler. A bigger temperature drop means a bigger pressure drop as well, so if your boost pressure goes down from changing only the intercooler, it means that the intercooler is working well. You're probably getting the same mass of air, but at lower manifold pressure.

The other possibility (Though highly unlikely) is that the intercooler is more restrictive, and therefore a greater pressure drop. I really don't think that's the case though.

This information is slightly off.. That's why intercooler manufacturers post up that have they X% efficiency with only a XPSI drop from inlet to outlet.

Not to mention the stock intercooler was reading a 3psi drop at 10 psi.

 

[IndigoMKII]

Just hook up the damn boost controller. no seriously was looking on the net for some answers and came across this. Dunno if it helps or not.

The difference in pressure required for a given amount of air to move from turbo to intake manifold is an indication of the hydraulic restriction of the intercooler, the up pipe, and the throttle body. Let's say you are trying to move 255 gram/sec of air through a stock intercooler, up pipe, and throttle body and there is a 4 psi difference that is pushing it along (I'm just making up numbers here). If your boost gauge reads 15 psi, that means the turbo is actually putting up 19 psi. Now you buy a PT-70 and slap on some Champion heads. Now you are moving 450 gm/sec of air. At 15 psi boost in the intake manifold the turbo now has to put up 23 psi, because the pressure drop required to get the higher air flow is now 8 psi instead of the 4 that we had before. More flow with the same equipment means higher pressure drop. So we put on a new front mount intercooler. It has a lower pressure drop, pressure drop is now 4 psi, so the turbo is putting up 19 psi again. Now we add the 65 mm throttle body and the pressure drop is now 3 psi. Then we add the 2.5" up pipe, and it drops to 2.5 psi. Now to make 15 psi boost the turbo only has to put up 17.5 psi. The difference in turbo outlet temperature between 23 psi and 17.5 psi is about 40 deg (assuming a constant efficiency)! So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost.

Um, what?

 

[Grandavi]

All the differences in pressure and temperature kind of makes sense, however, the confusing part to me is the drop in max psi reading of the waste gate. That is spring controlled by my understanding, so regardless of intercooler used I would think flow through the turbo would be consistent.

Sorry for sounding like an idiot here, but it still kind of baffles me. It would take 10 psi of pressure to open the wastegate (if I understand how it functions) because that is the set spring strength. That would be not relational to intake, throttle body or intercooler. Max boost using waste gate strength should remain consistent.

That's why I am confused as to why the. 10 psi changed to seven. The turbo has not changed, just the intercooler.

So 10 psi physically should be 10 psi. I'm not seeing why the max psi dropped to 7 unless something else other than the wastegate spring factors into when it opens.

It's not a concern as much as it is just me being baffled on how that occurs.

The only thing that makes sense to me is that the reading is different for the gauge..

I'm not using the boost controller until I'm not running on the stock bov. That won't be until first week of April.

Gonna ask my mechanic for a verbal explanation to see if he can get my thinking straight.., lol.

... Would be easy for me just to say... Oh I see. And continue in my baffled way. Funny how my research doesn't quite explain it so that the "light comes on"

 

[Grandavi]

Talked to my mechanic. They are going to smoke test it.. just to be sure, however, I think I understand what is happening now.

So.. basics...
7MGTE
Driftmotion (CXRacing) Intercooler - thier "new" one with both pipes on the same side
60-1 CT26 Turbo
HKS 3000 pipe + custom pipe to the fender (2.5" slightly larger diameter than the provided piping)
all hardpipes with silicon connectors, transducer on the turbo (pipe #1) so the turbo is blowing from a slightly smaller pipe into a slightly larger pipe, going through the core and into a slightly larger pipe, so no restrictions until sizewise. It always steps up slightly in size (not ideal, but I really didnt want to dick around with the provided pipes that fit from the fender to the intake seeing as I already had a custom pipe made).

From the explanation...
The turbo is pushing the air to the intercooler core at its rated wastegate pressure of Max 10 psi. Because it is not a larger system, that pressure is actually dropped as it moves through the core and piping (no restrictions like the stock) and as it hits the intake (where the gauge reading is being taken) ther is a pressure drop of 3 psi. Driftmotion (or CXracing, I can't recall) states that I should expect a .5 - 1.5 psi pressure drop with this core, and I just happen to get a 3 psi drop. Therefore, we will check it for leaks just to be sure.

However, what it means is that when I up the boost, the turbo will have to work just a bit harder (not really because there will be less resistance to its actual work), but my efficiency should be better because I will be able to flow more air through the system. This will mean if I set up for 18 psi, the turbo will (theoretically) have to start pushing 21 psi to get that to the intake manifold. This is a little shaky thinking because from my understanding its an exponential thing so that the flow is easier at higher boost. Therefore, my piddly stock boost is just not enough for the system (meaning.. the intercooler is too large for a stock application). It demands a bigger turbo. (thats the basic idea)

You can get too large of an intercooler, but this one is on other 7M vehicles without any discussion so I believe it will work very fine for me at the higher boost levels.

I think I understand now.. funny how this isn't discussed anywhere that I have found so far. (in a simplified way that is).


Good little FAQ site for intercoolers..
http://www.bellintercoolers.com/pages/techFAQ.html#FAQ_2

My only concern is that 3 psi pressure drop is a bit significant as the expected drop should only be .5-1.5. That is very near the max psi drop to tell me the intercooler is too big for my application.

 

[Dan_Gyoba]

That was basically what I was trying to get to. The wastegate spring works on pressures before the intercooler, but the gauge reads after.

The turbo is flowing the same amount of air (Maybe more, actually) but you are seeing less pressure in the manifold at the same flow rates. That is the reason why manifold pressure isn't a good measure to compare. 14 PSI manifold on a stock CT26 with stock intercooler won't make as much power as 10 PSI with a better turbo and good intercooler.

 

[Grandavi]

yeah, the confusing part is that I was assuming 10 PSI would be consistant throughout, but it drops traveling to the intake manifold so the manifold pressure is less. I am assuming that with higher pressure, the air flows faster (slower actually as that's the nature of increased pressure, but you get the point) so the power at the upper boost area will be more consistant throughout to redline because I will not max out the intercooler flow. Add that to a cooler charge temperature (assumed) and I get a denser mixture without "leaning" the air out at higher boost.

I believe I have my head wrapped around it finally... lol.

 

[IndigoMKII]

You're not understanding the information.

It doesn't matter of the size of the pipe. 10 psi before will be 10 psi after. You'll just have a little more 'lag' to fill the extra space, you won't receive a PSI drop.

 

[Grandavi]

Then why has my max psi at the wastegate dropped from 10 psi to 7 psi?

 

[IndigoMKII]

Then why has my max psi at the wastegate dropped from 10 psi to 7 psi?

Have you had it boost leak tested?

Think of it this way, when you apply 10 PSI to a set of sealed pipes that are 2" in diameter, you'll receive 10 psi at the opposite end right?

Now apply that same theory to 6" diameter pipes, you'll still receive 10 PSI at the opposite end, it will just take a little longer to reach 10 PSI.

 

[Grandavi]

That was my original thinking but my reading states there is a pressure drop, depending on the size of the pipes and core. It's too cold and snowy right now but it is going back in to be tested hopefully this week.

 

[Dan_Gyoba]

And cold and snowy means a greater temperature drop. It would be different if it were even 15 degrees warmer outside, but in this weather, I would expect that a good intercooler would mean a larger temperature drop and a corresponding pressure drop. I would bet that the issue would be less once it warms up.

It has nothing to do with the size of the pipe. The pipe diameter affects the airspeed within the pipe. A smaller diameter means faster speed, and more losses due to friction, but that's not really relevant here.

It's the fact that mass X of air at temperature Y will exert more pressure than mass X of air at temperature Y-Z where Z is the temperature drop across the intercooler.

Therefore, if you are taking a regulatory pressure reading from before the intercooler, an improvement in intercooler performance will result in a lower pressure reading.

This is mitigated somewhat by the fact that the higher pressure/temperature before the intercooler will force the pressure to increase on the other side of the intercooler somewhat, which will be based on the flow rates possible through the intercooler itself. In an ideal situation, the pressure would become equal on both sides, but real-world conditions are not ideal.

If you're going to treat things as ideal, a leak would also not cause a pressure drop at the manifold, since a leak would also then reduce the pressure at the turbo outlet, causing the wastegate to keep closed. More air through the turbo intake, but still the same amount entering the intake manifold. This is true up to the flow amounts where the turbo is no longer of maintaining pressure for the mass of air. For a 57 or 60-1 trim turbo, that's a very high flow rate, more than enough to cause other noticeable issues.

For a real-world example, while I was still using the stock turbo, I would see a 1.5-2 PSI drop in intake manifold pressure, with no changes tot he boost controller made by dropping a bag of dry ice onto the intercooler on a hot day. Now that I am taking the pressure to the boost controller from after the intercooler, the dry ice makes no difference to manifold pressure (Though I'd be willing to bet that it means that the turbo is taking in more air.)