ritzblitz

i cleared some space

Rogue_Ant

His pricing is right on with other 4-cylinder phenolic spacers I've seen.

ZW 944

Same

yellowline

The more you mess with your intake-head connection, the greater the chance of creating a giant leak or something else that will really throw off your engine. Then it leans out, burns a valve, you know the deal.

It's the type of thing you get laughed at for doing. How do I know this? My buddy put $150 spacers on his SR20 Sentra SE-R, it did almost nothing, and my other buddies and I (E36, Mustang 302, etc.) chuckle about it. I think lightweight pulleys are next on the list...

V2Rocket

i think that so long as the manifold and head mating surfaces are flat and true there wont be any issues with sealing as the phenolic material is true to within a few thousandths. also two new gaskets per cylinder should keep things tight.

while the benefits of the spacers in and of themselves may be negligible, the more mods you make the more they will probably benefit you. clearly turbo guys are the greater beneficiary of this but the dedicated NA guys running cams and chips and whatnot could probably appreciate this.

944Ross

With the phenolic, the intake will not grow the same as the head, the difference front-to-rear is what I would expect to cause gasket leaks.

ritzblitz

Things work better cold.

luftpirate

That's really an over simplification. Granted the spacer may keep your intake cooler but if you are worried about underhood temps there is much bigger monster in your bay and thats the 800+ degree header, vs. 200 degree aluminum intake manifold. Exhaust gases flow better the hotter they stay so wrapping your header to keep the heat in will help also.

ideola

We investigated this some time ago on 924board. To sum it up, there is absolutely no empirical evidence ANYWHERE that phenolic spacers do anything to reduce the charge air temps. I have personally talked to dozens of manufactures of these, and they ALL claim air intake temp reduction, but when I asked them to provide before and after testing data based on IAT sensors, every single one of them clammed up and stopped talking.

If you look carefully at the data promulgated by manufacturers of these devices, without exception, their temp reduction values are based on the temp of the intake manifold itself, NOT the charge air passing through it.

Now, think for a minute about the purpose of an intake plenum. It is designed specifically to move air as quickly as possible through the plenum and runners. Now think about how differently an intercooler must be designed to achieve measurable reduction of intake air temps: they are all based on the principle of slowing the air down, forcing it to come into as much surface area contact as possible. Those are two completely opposite design principles at work. And that's to say nothing of the boundary layer of air that quite probably insulates the large volume of flowing air from the "hot" intake plenum / manifold.

I am no fluid dynamics expert, and make no claim to understand the physics involved. However, I am highly skeptical that air passing very quickly through an intake plenum would be measurably affected by the temp of the plenum itself. If it were measurable and favorable for phenolic spacers, somebody would have measured it and touted the results. The fact that NOBODY has these figures is cause for skepticism, IMO.

There's no doubt that phenolic spacers can, in certain circumstances, reduce the temp of the intake manifold. However, there is no evidence that it in turn reduces charge air temps.

As for the benefits of reducing the intake manifold temp, I have talked to a couple of local Detroit engine builders who debunk the value of that as well. The argument I've heard from them is that eventually, everything under the hood will reach an equilibrium temperature-wise. So even if the phenolic spacer will temporarily reduce conducted heat from the head to the intake, the intake itself will eventually reach the same approximate temp any way due to inducted and radiated heat coming from other parts of the engine. Remember, the air outside the manifold is not moving nearly as fast or in as much volume as the air inside, so heat gain from induction and radiation will occur.

Here's the aforementioned thread on 924board. You'll see that I wasn't always a skeptic, but after listening to others and doing some of my own homework, I have become quite skeptical. I'm willing to change my mind again, but the principle would need to be proven by showing actual long-term, sustained reduction of intake air temp based on quantifiable measurements.

carlege

/ \ what that guy said
I

KuHL 951

I'm skeptical also about the reduction in IAT. With every car manufacturer trying to squeeze out every ounce of performance and fuel efficiency you would think every new vehicle would be so equipped with a <$10 set of spacers. They aren't. Would a spacer possibly move the injectors out of it's optimum location?

ideola

I don't know about that issue specifically, but also bear in mind, the spacer WILL change the length of the intake runner...something that could disrupt the Helmholz resonance, as I believe both the 2.5L+ and 2.0L intake manifolds are tuned for specific applications.

For example, the 931 manifold runners are approximately 1" or so longer than their NA counterpart. Haven't measured the 944 NA and Turbo manifolds myself, but I suspect they are also tuned.

Now, in the case of the 2.0L motors, a bit longer runner length might help improve the low-end response (longer runners = higher velocity = better torque at low RPM), but at what expense to top-end??? Hard to say...however, I've had some discussions around using spacers specifically for tweaking the flow characteristics, improving the angle of injection, etc., which seems to have more merits than the heat dissipation theory.

Of course, this is all conjecture, lacking any sort of real world testing...but it's definitely something to think about relative to what your goals are...

One more thing I forgot to mention above...it's important to recognize that the intent of phenolic spacers on carbureted engines has very little to do with decreasing intake air temps. Their use on carbs is strictly to prevent the carb from heating up as much in order to avoid vaporizing the fuel in the bowls...a much different concern than what we're discussing in this thread.

V2Rocket

if it turns out to be true that there is a minimal gain for NA cars then so be it. like i said in the original post, i will be doing some actual testing and will be posting up the temperature results whether they show a major difference or not. thats why this is a feeler thread, to see if there was interest, conditional on actual results


of course, the air temperature gathered from runners will be compared to ambient as there shouldn't be any reason for the air to heat up in the rubber j pipe, excepting maybe some oil mist.

ideola

What you want is a controlled environment to be able to show actual results on a fully warmed up engine before and after installation of the spacer. I'd encourage you to be as methodical and systematic in your approach and documentation as possible...we all know how the 924/944 crowd can be ;-)

A turbocharged application would be the most compelling platform to test on...

ritzblitz

My friend did actual dyno testing for phenolic spacers on a saab 9-3 (or 9-5, i forget). The car was turbo charged. I forget the actual dyno numbers but there were significant gains with the spacer. I want to say like 5hp 8tq at the wheels but I dont remember, I'll tell him to chime in here.