Intercoolers are always mentioned as having a major effect on VW IDI turbo engines. But every time I look at the exhaust manifold, parked right up tight to the intake manifold, I have to wonder how efficient an intercooler is going to be. After it takes heat out of the compressed (turbocharged) air, I expect the heat from the exhaust manifold just bakes the air passing through the intake manifold right back to an ungodly hot temperature. That intake manifold has no way to stay cool, sitting right next to the exhaust.
Has anyone done anything to try to reduce the heat soak on the intake manifold? Wraps, ceramic coatings, etc.? Maybe cross-flow cylinder heads? :lol:
The air doesn't linger in the manifold for long. About 3800 litres (1000 gallons) of 10-15psi air pass through the manifold every minute at 4000rpm. The manifold also has a very small surface area compared to something like an intercooler. This large volume of air will not be heated very much as it passes through the manifold. It might be worth a few tenths of a HP to insulate it, I wouldn't expect a lot more.
This is sorta within the spirit of this thread.
How much real world difference does an intercooler make. When I installed the TD in my pickup I also installed a Probe intercooler but havn't hooked it up. The stock TD does so well I'm not sure I need any more performance. Until I get a boost and EGT gauges I really can't be turning it up anyway.
Any thoughts on this.
The effect of my intercooler is pretty dramatic. I removed it once to repair a bracket. I reinstalled the original turbo to manifold plumbing temporarily. All of my fueling mods have been done after the intercooler was installed. My setup with the IC was pretty much smoke free. It didn't take long to see that the IC was pretty effective, without it the car smoked like a tire fire at anything over half throttle, was noticably down on power and EGT's were 50-100ºF higher across the board. Upon reinstalling the IC it was back to its powerful, smoke free self.
I wonder how much Jet Hot would want to coat the exhaust manifold on my 1.6 IDI. Think it would make a difference? How about that and the down pipe? You could also extrude hone them, think that would benefit at all?
Thanks Quick, guess I better get off my duff and plumb it in.
I have measured a bunch of intake air temps. The intercooler indeed works to cool the air charge (especially for high-boost setups, but still helps noticeably at stock boost pressure), assuming the intercooler setup is free-flowing and efficient (a measure of how much degrees temperature it cools compared to how much it possibly could if it were a "perfect" heat exchanger - IE, 100% intercooler would have air coming out of it the same temperature as ambient air temps), it is definitely beneficial. The result is more air density which allows for noticeably improved power with adequate fueling.
Back when I did the air intake temp measurements, I also took some measurements inside the intake manifold as well. Indeed, when the engine was switched off so air was stagnant in the intake manifold, the air inside there would rise in temperature dramatically due to the heat soak. The air cooled down dramatically after it was running the the car in motion to get airflow through the engine compartment cooling it off. A quick way to measure the temperature of the intake manifold is with your hand - give it the test of whether it's too hot to touch or not. That works for me in a pinch when I don't have my pyrometer thermocouple probe setup all handy. I found that between autocross runs, I can keep coolest intake manifold temps by keeping the engine idling constantly with the hood closed. That keeps the intake manifold cool enough to touch. Engine off with hood open, really heats up the intake manifold smokin' hot. Not good for autocross!
Ceramic coating on the inside and outside of the exhaust manifold helps the turbo to spool up a little bit quicker. In theory, it might help reduce intake manifold temps a little, but fact is the exhaust manifold still gets HOT even with some coating on it.