Skunk2 intake manifold observations
 

I've been curious about the power benefits of intake manifolds for a while. I've had a MAP v3 on my Evo for about five years, but after talking to a number of people, I decided to purchase a Skunk2 intake manifold. I just received it today, and the first thing I did was make some measurements on it. Plenum volume and runner length are my main interests.

The plenum appears to be significantly larger than a stock Evo IM, but after looking a little more carefully at the stock IM, I realized that while the explicit stock IM plenum is quite small, the openings into the runners are quite large, effectively making for a larger plenum volume. So I decided to measure the volume. The best that I could easily do was to fill the entire manifold with water. With the help of a bunch of duct tape, I found that the stock IM has a total volume of ~2.75 liters while the Skunk2 IM has a total volume of ~3.75 liters. Granted this is not a direct measurement of plenum volume because the runners are included, but after eyeballing both manifolds, I think its reasonable to conclude that the Skunk2 IM has a somewhat larger plenum volume, probably by ~0.5-0.75 liter. So the Skunk2 does have a larger plenum that can potentially help accommodate the pulsed flow that occurs. Unfortunately the Skunk2 plenum size pales in comparison to the claimed 5L volume of the Magnus V5, so I think of the Skunk2 has having good intentions, potentially with some mild benefit.

Runner length plays a role in determining the engine speed where peak IM scavenging efficiency occurs. The shorter the runner, the higher the rpm where peak resonant scavenging occurs. Somewhat surprisingly, the Skunk2 runner length does not seem any shorter than a stock IM when accounting for the fact that the first few inches of the runners in the stock IM appear to be more like a plenum than a runner. However, my interpretation is certainly debatable because the resonant frequency is likely somewhat dependent the length to the true plenum that is a few inches longer than for the Skunk2. Depends a lot on whether those first few inches of the stock IM play a role in setting the resonant frequency.

So overall, the Skunk2 looks to be a mild enhancement of the stock IM. I'm looking forward to getting it installed and seeing what it does compared to the MAP v3. BTW, the latest Skunk2 casting appears to be much nicer quality than the earlier castings that was used for many of the original reviews of this manifold. I'll try to post some pictures this evening.

Awesome, I've been curious about this manifold for a while and I'll probably pick one up eventually. I have a fair bit of flow bench test experience with intake manifolds and cylinder heads. I usually lean towards smaller plenums for anything that isn't drag racing, if you go too large on plenum size it can negatively affect throttle response.

I think the biggest thing that the Skunk2 mani brings to the table IMO is better flow balance. The evo has one of the better factory intake manifolds I've seen compared to most 4 banger stuff but the two big things that hurt balance one it are the sharp radius that air has to make coming through the throttle body to get down the cyl 4 runner, and the curvature in the cyl 1 runner. It looks like the Skunk2 piece addresses both of these so I'd be willing to be it's flows a fair bit more evenly across the cylinders.

I haven't spent much time looking for photos of the inside of it so I'd interested to see what you post up.

Would be great to compare. Wish I had one to borrow. Maybe ER would let me borrow. Was just there this afternoon. Discussing the Skunk2 IM install.

Good info, subbed for findings.

Here were my results of Skunk 2 vs Curt Brown Extreme Port with no other changes....
https://www.evolutionm.net/forums/ev...l#post10190934


Red - Skunk 2 / stock TB
Blue - CBEP / 70mm FB TB

https://cimg1.ibsrv.net/gimg/www.evo...f3435518a5.jpg

Probably good to try to accumulate all the Skunk2 IM dyno results in one thread. I have probably seen as many favorable as unfavorable results for the Skunk2. I did see yours before deciding to buy. Its not quite 1:1 because of the TB differences.

Mychailo , we spoke on this but I'd like to contribute to the class as well.

FWIW, I tested a
Stock IM and stock TB
Ported stocker with ported 65mm stock TB
Unported skunk IM ported 65mm stock TB .

The skunk 2 was worth about 15whp+ at the 500whp mark with stock cams/red. It made the same power at 1psi less boost up top. The dyno graph looked identical. This was done the same week/ boost leak tested between intakes. Testing was done in SAE on a dynojet. No doubt something making big power would make more with an aftermarket intake. Now, the stock IM is pretty good and we can thank mitsubishi for years of rally car development.


On the street if you are really looking for it the skunk 2 has slightly less response then the stock IM. Very minimal difference in response at least on the MHI red/stock cam combo. Something with big cams or turbo may have a bit more difference in response then what I experienced. Still respectable in today's world. Some of us get caught up in 30psi at 3300 even though the engine can't move the air out.

Going off historic data a large plenum manifold like the Magnus should move the power band to the right vs the skunk 2. They are both great pieces, but its important to build your cars for your goals. A back to back to test would be great. We all love data.

We are looking forward to your results.

You lose port velocity with the short runner large plenum manifold, which is why the ported stocker will crush the Skunk2 below 7K. I don't think the 70mm TB does anything to improve low end response, but don't actually have data to support that assumption. For all out power the Skunk2 is the way to go, but for a daily driver it just didn't make sense based on my results. Curt convinced me to do the switch because he had other customers reporting the same thing.

The same trend holds true in the GTR community when comparing ported stocker to the aftermarket manifolds. Ported stocker provides much better low end response vs Greddy, AMS, Boost Logic, etc., but for all out hp those manifolds are the way to go.

Looking forward to seeing your results.

My skunk 2 was ported at stm, formerly mated to a 71 hta and currently paired with a gen 2 3582 1.01 twin scroll on a 2.4 lr. I hope it's worth some berries and im anxious to see what you do.

Not to hijack, but do you have a link to your setup and results?

no sorry, I had sold the car to my best friend and I'm heavily involved in the construction and parts make up, but unfortunately we are held up by small items like injectors, time, and cam seals.. probably some other stuff too. Just taking time.

Not sure how many people remember this review from 2010 of the Skunk2 IM done by Pure Tuning:

http://pure-tuning.com/blog/?p=207

The review looks like a good 1:1 comparison against a stock IM in the 350 whp range showing good gains throughout the boosted rpm range and no loses anywhere. Here is the Skunk2 vs stock IM dyno plot. As with Abacus, it appears that the Skunk2 outdid the stock IM at higher rpm even though the Skunk2 setup was at slightly lower boost.


https://cimg2.ibsrv.net/gimg/www.evo...bdd6b2c662.jpg

are you on maf still? Would be pretty interesting the hz increase!