Phenolic Spacers to improve performance

[yoshimitsuspeed]

I searched and found one other thread on eng-tips talking about this and it was pretty well agreed that adding an insuliative spacer between the head and the mani doesn't do anything significant. It also didn't have any useful data in it.
Once you start to understand the sheer volume of air passing through the intake it's hard to believe it does anything at all but so many people out there are so convinced it works you can't even suggest the possibility of it not without people getting upset. Unfortunately all dynos I have seen that suggest it may give some small gains are always done by the people trying to sell the spacers.
I'm not bad at math but accurately calculating how much x amount temp drop in the runner would lower the temp in the air would be far more hassle than I am interested in. It just does not seem possible that air traveling through say a .4 liter runner even 30 C above ambient at say 800 liter per min could be warmed by any significant amount.
Does anyone have personal experience with this. Ever seen or done a scientific study? Ever seen unbiased dyno results? Anything else productive to add to the conversation?

Hopefully I can test this theory once my engine dyno is setup but I would love to see what other people thought about the subject. It almost feels like even taking the time to test it would be a waste of resources.
In the other thread it was said that for carb motors it can help reduce chances of vapor lock which completely makes sense. Does it do anything more than that?

 

[BrianPetersen]

Temperature change of the air going through the carb might not be the real effect (and I agree that it ought to be insignificant).

But ...

Heat conducted up through the manifold into the float bowls can boil the fuel and wreak havoc.

The fuel being drawn into the air stream is not being drawn in symmetrically. Having a little extra distance for the mixture to flow before it gets to the plenum might change the cylinder-to-cylinder fuel distribution.

The spacer builds in a little more effective plenum volume and a little more effective total induction length.

 

[yoshimitsuspeed]

I should have explained better. My question is for EFI engines.
We could also focus on just the airflow aspect for carb engines but I see this being more complicated since the heat will have other effects like heating up the fuel, changing the rate at which it evaporates, changing the amount of time before entering the engine and maybe other variables.
Getting rid of those variables and just looking at air entering the engine is there any way an insulator could have any notable effect on performance?

 

[BrianPetersen]

I can't see such a thing making any meaningful difference on a multiport fuel injected engine.

A lot of people see some fancy gizmo in one application where it serves a purpose, and then think it works in every application including the ones that don't have whatever issue the gizmo solves in the original instance ...

 

[yoshimitsuspeed]

That pretty well sums up my feelings as well. Unfortunately I have found less documentation or intelligent conversation trying to disprove it than I can trying to prove it. Of course I haven't found much intelligent conversation on it at all. Mostly just things like this.

http://www.hondata.com/heatshieldgasket.html#Details

Ooooh it lowers the temps of the outside of the runners by X amount so it must make a significant difference in HP.

 

[yoshimitsuspeed]

Still interested to hear what others have to say. Especially if anyone has had any actual personal experience studying this or seeing it's effects or lack thereof.

 

[ornerynorsk]

Fishing lures are manufactured more to catch fishermen, rather than fish. So it is with some products. I can't see any advantage in having a spacer, other than to provide a location for instrumentation sensors???

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[140Airpower]

This is a case of an effect that is virtually guaranteed to be beneficial being perhaps not worth doing because the benefit is so small. It may not be measurable on a dyno under steady-state conditions, but might show up on an inertia dyno where there has been heat soak into an aluminum manifold over a period of time before the run. So, it might be significant in drag racing.
Historically, American manufacturers have gone to lengths to isolate the manifold runners from engine heat in special cold-runner NASCAR manifolds. This often involved separating the runners of an aluminum manifold from the valley cover and hot oil. Compared to that, insulators alone would have much less of an effect.

 

[1gibson]

Biggest benefit is probably that they are easy to "gasket match" using a drill or dremel and a sanding drum, and you can easily confirm that there is a smooth transition by checking against each mating part. Still not going to do a whole lot but if you need every last bit of power, should be cheap and it won't hurt.

 

[inline6]

i suspect most feedback is a seat of the pants thing coming from the longer length.