Importance of stock intake when boosted.

[NotSoSlowSHO]

Hey gang.

Im itching for a project. A while back I had considered a custom SC setup, then I looked into a lightweight SHO transplant project.... Now Im back to the SC. I have some "interesting" intake designs hidden in my notebook, but I need to consider the pros and cons before I even attempt to fabricate anything.

Anyhows... lets talk about the stock intake.

Ill line out some questions:

1. Is the stock intake really needed when a SHO motor is boosted?
2. Ive read that boosted SHOs run without butterflies. True?
3. How much improvement (ona boosted SHO) does EH runners and a ported intake show?
4. would there be negative effects to fabbing an intake thateliminates runners all together wen boosted?

Thanks for any help.

Oh, and a little hint:

I have two designs. One using a single eaton m-90. Second using dual m-45's. Both clear the stock hood, and SHOULD have room for an intercooler.

 

[Toolman]

I use BBB's and EH intake. If for nothing else, I could not bear to open the hood and NOT see the sweet SHO snakes. It for sure is not a limitation to making power. I have no doubt I will have a very broad usable powerband with over 450whp/450ft lbs when I dyno this car next. For me, it would not be worth the work. But by all means, something different would be cool, but I do no see the benefit being worth the time/etc, but that is just me.

 

[NotSoSlowSHO]

primary reasons are simple. Cost, and space. I could fab an intake for pennies, and make a dirt cheap m90 fit under a stock hood.

But the powerband is what Im really interested in. And how the use of runners effects the powerband in a boosted app.

 

[SinisterSHO]

I believe Todd Cook uses a sheet metal intake on his Pikes Peak car. A friend of mine had taken his car to a guy who does alot of four valve head porting. He deals alot with DSMs. He asked my friend if he wanted to make a sheet metal intake. So, what I get from that is by him just looking at it, he could tell that it is a restriction. As far as s/c cars running with out butterflies, I've never heard of that, and to me it wouldn't make any sense. If an N/A car loses low end torque with the butterflies open, why wouldn't a s/c car?

 

[K-Dawg]

I have nothing helpful to add other than sheetmetal intakes are sweet!

 

[Toolman]

A friend of mine had taken his car to a guy who does alot of four valve head porting. He deals alot with DSMs. He asked my friend if he wanted to make a sheet metal intake. So, what I get from that is by him just looking at it, he could tell that it is a restriction.

I would put more trust in the actual results I see, rather than some guy that just looked at it but has no experience with SHO's. Granted, it was designed with a 220hp car in mind, but the fact that there are SHO's putting down more than 500hp with it prove it is far from a restriction. What you may gain in high rpm hp will not be worth the loss of driveability and nice flat tq. Race engines are great, but only on the track, not on the street.

 

[NotSoSlowSHO]

But that is N/A.

Im taking boosted. Roots boosted

This is a post that I was trying to get at:

A roots blower negates the need for different length runners. The reason for the different lengths is for air velocity of a N/A engine. When you are running positive PSI, there really is no need for it, just bigger openings into the cylinders so you can cram more air in.

And another post from the same thread:

velicity stacks are controversial when a positive displacement blower is used. They have discussed this in great detail and debate over at www.v6power.net

They seem to help with a centrifugal setup, but don't really do much of anything when a roots/screw blower is used. Seems the more boost you have, and the quicker it comes on, the less the need for runner length. Look at the supercoupe, which uses virutally no runners other than the ports in the heads. My supercoupe makes over 350 rwtq at the 1,500 rpm that I started the dyno pull at (manual transmission).

Jeramie

From a thread showing Tyler's M90 setup http://www.shoforum.com/showthread.php?t=38564&page=4&pp=30

 

[60kmaintenance]

If an N/A car loses low end torque with the butterflies open, why wouldn't a s/c car?

It doesn't work that way under all circumstances.... The stock SHO's balance of air and fuel, via velocity and flow...... None of that matters with a forced induction vehical when building boost, the air is pushed with the gas into it, so velocity is taken care of...... Low end rpm's is where velocity is important, flow at higher rpms, of course both are important, but when your forcing the air in, you have velocity and flow all the time.

Now the thing is where the S/C builds boost, at what rpm, and below that it could hurt the engine to have to much flow, because it consequently kills the velocity. That would be a problem for when it isn't building boost. Now there are ways around that, like with turbos, but getting them to spool up a little at idle wears on them faster as well as the constant use of WG's, plus you'll probably be looking into two turbos for the lower rpm boost levels. Also knowing the broad range of rpm on the sho, it's probably not a good idea to twin turbo to get low end power, and not be able to build enough boost for extream top end (depending on what you want to put out). Also smaller constantly spinning turbos produce a lot of heat, you're gonna want a intercooler for sure. I guess you could, but since the sho doesn't live in the lower RPM's (unless drag racing, and if your gonna seriously consider a SHO as a drag racer you'll want an ATX with custom stall converter) why bother. With an MTX you'll always be in the power operating ranges if you want (you know past 25-30mph).

All in all, stick with the butterflys, don't program them to open until you build boost. However not having them will not hurt the car under boost.

 

[K-Dawg]

Just a quick phyics note:

Even in a N/A application, air is pushed into the cylinders by atmospheric pressure. With a compressor, you are creating a larger difference in pressure between the intake manifold and cylinder than you would have otherwise. This forces more air into the cylinder.

I'd imagine that properly tuned intake runners (not necessarily stock) would still be beneficial under boost. However, as long as you have the flow, I don't think intake design changes would make as much of a difference under boost as they would N/A.

I think as far as most people on this forum, and elsewhere, are concerned, issues like this are best resolved by trial and error. Not many people have the knowledge to say for sure exactly what will work best for each application.

Really, I don't know anything, just thinking aloud (visually).

 

[1slickRED89]

I had thought about it my own intake as well, something about 12 indivdual throttles gives me tingles.

realistically, there are better design I think, but you'd really have to outsmart the engineers to make things work better than what is on there already. so read some ASE papers ($5-$10 each) and get some books (heywood etc.) before you start.

 

[Off Road SHO]

Secondaries, SECONDARIES?! I don't need no stinkin secondaries. With a positive displacement blower you don't need them anymore. And that IS through trial and error or should I say fun and more fun.

Tom

 

[PanamaPat]

Secondaries, SECONDARIES?! I don't need no stinkin secondaries. With a positive displacement blower you don't need them anymore. And that IS through trial and error or should I say fun and more fun.

Tom

No secondary butterflies on my track SHO (boosted) and it breathes much better at the top end.

 

[NotSoSlowSHO]

sweet deal. Ive got the needed responses.

This project is a GO!

At least the preliminary intake design

 

[Toolman]

No secondary butterflies on my track SHO (boosted) and it breathes much better at the top end.

How is it down low? I have been toying with the idea of removing my BBB's completely.

 

[PanamaPat]

How is it down low? I have been toying with the idea of removing my BBB's completely.

With the s/c, its hard to really notice the loss, but I'm sure there probably is some.

 

[Off Road SHO]

With the s/c, its hard to really notice the loss, but I'm sure there probably is some.

Maybe with a centrifugal blower. With a PD blower the torque is there, no waiting.

Go for it. I want to see that intake when you're done.

Tom

 

[revhardSHO]

You could always do what that guy did with his top mounted blower. Cut up the stock manifold which will enable you to use 3-4" of the stock runners for tuning while being able to put an nice sheet metal intake on top for the s/c to mount up to.

 

[NotSoSlowSHO]

The only thing related to Tylers setup with my design is the usage of a M90.
I had thoughts about using such a box, but Ive got another idea cooking. Plus, I want to close a stock hood to hide this thing, so the blower will not reside directly above the valley.

I tore the intake off of my junk-SHO today to take some measurements and eye-ball a few things. Lucky me.... I had a brain fart that SIMPLIFIES things :laugh_ti:

 

[NotSoSlowSHO]

here is an interesting find.

Ive been casually doing intake research online. I found a site talking about a LS1 Positive displacement blower kit.

link here: http://www.popularhotrodding.com/tech/MagnaCharger/

Now, take a look at thise included pics, one described as a stock intake, and one described as a "prototype" for the SC setup.

stock:

"prototype":

notice the difference? All they did was remove a majority ofthe runners.

 

[luigisho]

Interesting. It's been a while since I've had the intake off and got a good look at the head ports and runners. Are the long and short runners using a common wall? Now I'll have to pull the one off the GenI to get a look. How about a little clarification on your intake modification thoughts??