[Ecotec] Ecotec intake manifold, restrictive at 291rwhp

[GTP 85]

I have a dilemma.

Please take a a look at my thread i.e. mods, power etc... here > http://forums.justcommodores.com.au/vr-vs/47660-gilbs-custom-vs-7.html

Anyway... Got the new combo all tuned up and the injectors weren't up to the task at 291rwhp, so put some Super 6 injectors in and went back today to get the tune finished. That fixed the leaning out issue up top, so now it's 'safe' fuel wise. Now another problem.... According to the graph (and the tuner) the power still seems to be falling over at approx 5000rpm. Fuel and timing are sweet, so it's not that. He reckons the problem is now the manifold/ plenum is becoming a restriction (same theory as the manifold on a hot 5L v8). I suggested maybe a plenum spacer and he said it will do s.f.a. I have researched twin throttles, and that wont do the job for this application either... He also told me not to bother with that... So basically we need to redesign a new manifold!

I have always wanted to do this, so what better an opportunity. The tuner has crunched the numbers and he has dimensions for a setup that has two individual plenums and two individual throttles. From his R&D in the past the v6's biggest problem is the intake ports sucking air from so close together. We will probably use sheet ally to make the plenums

Manifold becoming a restriction... Has anyone ever heard/ seen/ experienced this on the Australian ecotec before?? Not looking for negative criticisms, please comment if you can advise or help

Thanks

Oh and i'll go back to get my latest graphs on monday if anyone is interested in looking at them

 

[ephect]

will we finally see the walky manifold on and running?!?!?!?!?!!! doooo it!

i've never heard of the manifold being a restriction!

 

[HamaTime™]

dude, this is so exciting. That manifold looks awesome ^^^

That designed for an Ecotec?

 

[MACE]

I suggested maybe a plenum spacer and he said it will do s.f.a.

To add to the above statement plenum spacers have been around for ages for other engines which have been proven to work

Plenum Spacers - Nissan 350Z & 370Z Wiki

Here is a replacement plenum cover for the same engine.

Nissan 350Z Performance - North American Specification

The main reason, that they increase power is they slow down the air speed allowing the air to distribute more evenly between runners.


“From his R&D in the past the v6's biggest problem is the intake ports sucking air from so close together.”

Lots of engine have intake ports sucking air close together, the problem with the ecotec manifold is that the throttle body is relatively close to cylinders 3 and 4

Shown below is a standard Ford Winsor manifold. Notice where the throttle body gets channeled to the middle cylinders on a 8 cylinder (potentially worse air distribution then a factory ecotec!)

Mustang Intake Manifold Test FRPP GT 40 Intake Photo 4

Below is another Ford manifold for the same engine which is an excellently designed single throttle manifold, with the throttle body far away from the runners with a “funnel” style of channel to the runners, for excellent air distribution.

Mustang Intake Manifold Test Trick Flow Track Heat Photo 10

The only thing I would do with the above design would not be so much with the manifold by the orientation of the throttle body

For high end ecotec builds the twin throttle body manifolds we use to sell, provided they were setup properly (less then 10% of the installs were done this way!), worked quite well.

In saying all of this though you can certainly develop a better setup then what is already available off the shelf, I guess it depends on how far you want to go with the build I guess

Hope this constructive feedback was of any use

Cheers
Steve

 

[GTP 85]

Thanks Steve... By no means take what i have written as exactly what he said. Althought he can be a little blunt sometimes, i'm sure he was pushing me toward developing my own twin plenum rather than mess with spacers/ twin throttles etc... purely to be different.

He is an old schooler messing with chev v8 etc in his younger days, before getting involved with v6 development (4.3 stroker). He is my "oracle" on all my personal v6 mods, so i do respect both his opinions as an experienced v6 specialist as well as yours Steve. I do appreciate your imput.

I did run the plenum spacer idea by him, as well as the twin throttle mani. Thinkin he just got excited than now we have an excuse to custom fab a new piece of gear.

 

[PanthaVS]

Lots of engine have intake ports sucking air close together, the problem with the ecotec manifold is that the throttle body is relatively close to cylinders 3 and 4

Agreed. What you "could" do, is twin throttle body the manifold...

I have researched twin throttles, and that wont do the job for this application either... He also told me not to bother with that... So basically we need to redesign a new manifold!

What research have you done? If we are to beleive this, I assume you've used a flow bench? And there are quite a few different types of TT manifolds out there...

I've seen where people cut up a set of manifolds, and weld a set of 2 TB mounts to one side, then they run 2 factory TB's. Thus, eliminating what Steve at mace is saying about cylinders 3 and 4. You could then further the intake amount by using 69-70mm TB's on it.

But... we have to ask you... what are you running between the intake manifold and the atmosphere...???

Do you have a MAFless tune? I assume you do, or you are running an LS1 MAF?

What air filter are you using (if any)?

What's the size of the piping between the filter and the manifold....?

 

[Immortality]

the walker manifold like nice but i think better can be made. it doesn't look like it has trumpets at the end of the runners which isn't a good thing.

there is the COME option but in reality i don't think it is much better then a stock plenum with the appropriate MACE spacers used.

shall be watching this with interest

 

[GTP 85]

Whether you believe me or not, doesn't faze me. It's not me, it's my tuner who has the years of experience.. yes he has done all the associated testing long before i came along with this problem.

Don't get me wrong, if it were as easy as a plenum spacer or a ttb plenum i'd do it... but i can't justify outlaying that much money for a ttb setup. Sure it may fix the distribution issue, but the plenum volume issue will remain. Personally i dont like the look of the spacer, so it's a no brainer on that one, i don't want it. What i'm saying is i would much rather put that money into customising my own twin plenum, dual tb manifold. He has the tig welder, the sheet cutting machines, the sheet benders.. so i'm gonna do it.

He stressed i will get excellent results if i separate the two banks into two plenums, there must be a reason for him suggesting that so i'm sticking to it. It's a great opportunity to make up the manifold that i always wanted to put together

I have an enclosed K&N pod with plenty of fresh air access, 3.5 inch stainless pipe, ported tb, still running maf. I dont see the point of running mafless, and the tuner has never suggested i go mafless so it's still there.

 

[soop]

Great to hear, always good to see people taking the initiative to try something different.

Frankly, I think your setup is probably past the point of a manifold spacer anyway.

 

[GTP 85]

Hmmm.. Just had a quick look at the thread about maf limitations. I might ask him if the maf could be the issue?? But id assume he's pick up on that if it were the case?? might ask

Also a mate just sent me this pic! WOW. :yeah: