mom I’ll find a different one then. Thank you!!!!

 

Its easy to diagnose when running. If it behaves in a way you don't like pull the intercooler and replace with a section of pipe. If the problem goes away you know its the intercooler.

 

Mom...? Stupid phone. Lmao. Awesome! I’ll give that a try. I have a little ways to go before I get that far. Thank you very much!!!

 

The pressure test is a crucial diagnostic that most people skip. You MUST apply 'boost pressure' (20-30psi or whatever you run +5psi) to the turbocharger compressor inlet, and let the entire plumbing through the intercooler and into the intake manifold fill with and hold compressed air. This is absolutely essential do not overlook and do not skip this test. You will need to block off one of the compressor inlets, use a plug from home depot like a pvc plug or something, you can grind off any threads and use a coupler to achieve this. you must also disconnect any crankcase lines or crankcase tubes from the plumbing to avoid pressurizing the crankcase during this test. Speaking of which you also need PCV from the turbocharger inlet tube attached to the crankcase as a fresh air vent tube when you are finished with the whole setup to keep oil inside the engine and out of the intake manifold during boost. You will want to use the 1998 toyota supra turbo PCV valve between the intake manifold and crankcase to achieve part throttle PCV as well. Do not skip or overlook these items they are crucial to oil control.

So what happens if you forget the pressure test? I will paint a vivid picture for your imagination so you do not overlook this critical step in turbo learning.

Every air molecule the compressor wheel ejects must make it to the engine. For each molecule that leaks out, the boost pressure will drop slightly, which will cause the wastegate reference to notice and demand more from the compressor. That means additional exhaust gas pressure and volume will be required from the engine. So as more air is leaking out, the EGT and EGP will begin to rise, and it can in a dramatic fashion causing a melt-down of the engine, pistons, manifolds, etc... will get excessively hot and melt or the piston can even expand so far in the bore the ring will seize and rip the piston apart. These are the consequences of forgetting to perform the critical pressure test. The best case scenario is a moderate increase in exhaust temp and pressure which will limit power and leave you scratching your head why doesn't the engine make the power it should?

 

As to your intercooler question, its a good question I think worthy of one more look.
The intercooler can fail you in two ways.
1. It can fail to maintain an intake manifold temperature near ambient. e.g. The IAT at the intake manifold should be between 80*F and 100*F when the ambient temp is near 80*F. Boost pressure is irrelevant here; what matters is total flow capacity of the intercooler and heat exchange coefficient of the intercooler, which we don't care about because we don't know these things. ALL we can do is measure the IAT at the intake manifold and make sure it stays DOWN near ambient temp. Do NOT run the IAT much above 110*F when using gasoline, any type of gasoline fuel will NOT tolerate that high IAT for very long. It will begin to create pressure spikes... not exactly detonation. Not exactly preignition. Just the chemical reaction of gasoline type fuels (87-93-98 octane hydrocarbon chains with lengths ranging from 7 to 9 carbons long) is going to SPEED UP DRAMATICALLY when the intake air temperature rises beyond a certain point, and this will create a large pressure spike in the cylinder which will hopefully teach you a quick lesson by only blowing the head gasket. Assuming you used a OEM style head gasket, which by the way: I recommend OEM gasket materials for sealing the heads for this specific reason. If the head gasket doesn't blow, it will put a hole somewhere else, like the piston. It will remove a chunk from the piston. You can find evidence of this all over the internet, the most common failure point for OEM cast aluminum pistons in forced induction application is due to this exact scenario: Pressure boost leaks out, EGT rises, Demand on the compressor wheel increases, pump total flow mass increases, pushing the compressor off the map and taxing the intercooler assuming the leak is after the intercooler, Any/All of these things will create a high IAT and if you don't catch it in time the piston will break and catastrophic failure will ensue.

The second way the intercooler can fail you is due to total volume flow rate pressure drop. In other words, when any piece of pipe, doesn't matter if its an intercooler or a straight piece of pipe, they can max out near the speed of sound of volume flow rate in CFM. These conditionals depend on several fluid dynamics properties we won't get into (viscosity, pressure, wall roughness, laminar flow vs turbulent, boundary layer, bends, necking, mixing/eddies, etc... ) but suffice to say once your pipe hits that wall (or intercooler) the flow rate in terms of volume per unit time will rapidly stop increasing the power will taper off from the engine, regardless of how much pressure (in boost) or temperature you control.

All that said, in street applications where you size the turbo properly (I recommend you size them using match bot or do so on paper to ensure they will run the way you expect) it is generally ideal to run the largest intercooler you can fit. Intercoolers will remove power because they both represent a slight restriction and they remove internal and kinetic energy from the air, but these two things are negligible in a turbo application because the compressor can often support far more flow than the engine and combination in question can use, when sized appropriately.

 

Holy crap! Thank you very much for this information! So I’m understanding you correctly, I need to pressurize the charge pipe side intercooler and all to whatever boost pressure I plan to run +5 psi and make sure it holds? I’ll also get the PCV valve and get that set up as well.
Again thank you very much!

 

here is a short video of an intake manifold pressure test, and then at the end a boost leak pressure through the compressor.


That should help explain what you are trying to do.
Be warned plastic intakes won't take a ton of boost pressure. It depends on the design. So be careful not to use more pressure than you think the intake can withstand. For example I've seen the ls1 intake explode with something like 22psi. The LS6 intake seems to do better. So just be careful about that.

 

Wow! I can’t thank you enough for the information. I’ve copied this and will get into this further. Thank you!

 

I made my tester myself with stuff from the hardware store and old couplers. I test every system before they go on the dyno. A boost leak can cause the turbo to overspin and come apart.

 

I got the pressure regulator and air hose from harbor freight.

 

Great!!! I’ll definitely put the parts together for this test. I really appreciate it!

 

Good old gen 1 abc turbo build.
A man after my own heart.

 

Thank you! It’s a work in progress but with everyone’s great advice it’s should be fun!!!