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shortening a 16v intake manifold, tell me how bad of an idea it really is

DaytonAE86

DaytonAE86

Active member
Joined
Jan 28, 2006
Location
Gem City, USA
I was just hoping some of turbobricks greatest minds could inform me. I need to either shorten the stock runners and move the plenum closer to the head, or have a new plenum made with the throttle body moved for a 16v in 240 swap (or small brake booster and b204gt intake).


My questions are really about flow and runner length, how badly are they effected by modifying them from stock.

1) How short is too short, and would shortening the stock manifold even work (somewhat well, or possibly better than stock?!).

2) Would I be better off the have a new plenum made to fit over the stock manifold runners, cutting the stock runners as long as possible and welding a new plenum around them (extend them inside the tubular plenum, yet move TB position and change the shape a bit to accommodate the brake booster?).

3) Will a STOCK 16v intake clear the small brake booster, or is a shortened/custom intake still needed.


Thanks.
 
1. How high are you going to be revving it? I kept my runner at the stock length and am VERY happy with the results. Very broad power band and it flows nice up top.

2. I think a new larger plenum is the way to fly. Solves the uneven flow issues with the 16v manifold and gives you the plenum volume you want to make biggie power at higher rpms.

3. Stock manifold will clear even a stock location 240 brake master, its the throttle body that fouls. If you could jimmy a thin brake master on a 240 you MIGHT be in the clear...

Here is the plenum I built for my 242

1.jpg


I am also making a run of these manifolds, PM if interested.
 
I don't really plan on taking it past 6500, maybe 7k. The intention is to keep everything as stock as possible for reliability, stock Mahle's with 16v reliefs cut in, OE HG, 13mm rods, so the rotating mass is an issue at higher RPMs.

What are you using for a TB on your setup and would you have a picture of inside the plenum, I want to see how you mated the runners to the new plenum.





Thanks.
 
Short won't matter under massive boost. If you have a 740, the stock 16v NA intake manifold will fit with the stock 16v na brake booster. If you have a 240, who cares... Ha.

Simon
 
sbabbs said:
Short won't matter under massive boost. If you have a 740, the stock 16v NA intake manifold will fit with the stock 16v na brake booster. If you have a 240, who cares... Ha.

Simon
Click to expand...

Runner length has a lot to do with powerband. Runner length does the same thing even under boost.

My manifold uses a 960tb. The runners are not fancy, just cut where the runners have a chamfer which I smooth out before welding the plenum to it. Its nothing fancy but effective enough for anything you are going to put though a stock block.
 
i shortened my runners on the b234f manifold from the fuel injector bungs right up to where the runners start to change from that oval shaped. overall probably cut 3" out of the runners. Here is a ****ty camera picture of the manifold. As you can see there is a bunch of clearance between the throttle body flange, and the master cylinder...definitely enough clearance for a 90 degree elbow.

Photo_091109_001.jpg
IMG_5995.jpg

IMG_5997.jpg

IMG_5998.jpg
 
isn't that my manifold that I sold you? I recognize those welds.

shaved240 said:
i shortened my runners on the b234f manifold from the fuel injector bungs right up to where the runners start to change from that oval shaped. overall probably cut 3" out of the runners. Here is a ****ty camera picture of the manifold. As you can see there is a bunch of clearance between the throttle body flange, and the master cylinder...definitely enough clearance for a 90 degree elbow.

Photo_091109_001.jpg
IMG_5995.jpg

IMG_5997.jpg

IMG_5998.jpg
Click to expand...
 
Intake runner length makes a fairly big difference, what I'm wondering is, with your setup, which is the absolute cheapest way to do it, will it make low RPM driveability suck?

------cost
-----/---- \
----/--- -- \
effort -----returns


Any other suggestions, I think these are about the cheapest ways, short of cutting the throttle body off and moving it towards the cylinder 1 runner pointing at the headlight bucket.......... would this cause mismatched flow to 1/2/3/4?

Obviously SD's is the best, Shaved240's is 2nd cheapest, best for high end, and who knows about relocating the the TB.

Just trying to figure out the best budget solution for 16v 240 intakes, its the last if with my project (that I can think of right now).
 
Just thought about it, any thoughts on moving the throttle body to the front of the stock plenum, vs the center, or pointing it downwards and out of the way of the booster.
 
What engine-management is running it ... it wouldn't be aftermarket would it?
If it's aftermarket, there's no way you could bodgy-up something like a TVIS manifold off a 4AGE or 3SGE could you? 3SGE heads are kinda a similar length to a SOHC redblock head; has anyone ever measured one? There are probably other 4cyl engines with compact variable-length runners, aren't there?
 
Forg said:
What engine-management is running it ... it wouldn't be aftermarket would it?
If it's aftermarket, there's no way you could bodgy-up something like a TVIS manifold off a 4AGE or 3SGE could you? 3SGE heads are kinda a similar length to a SOHC redblock head; has anyone ever measured one? There are probably other 4cyl engines with compact variable-length runners, aren't there?
Click to expand...


Think of the bore/port spacing, unless your talking about just using the plenum off of something with alot of volume, to cut down on fabrication costs (since I can't weld aluminum, but know those who can).

About the only other thing I can think of would be to find a b204 intake, not running an 8v, too many people say they suck.

Thanks for the advice.
 
I think somebody has posted photos of the intake manifold of a car roughly similar that you have.

That entire ENGINE and Manifolds /ports/ everything was designed from a clean sheet of paper as a manifold to be used on a turbo engine.
The designers were who GM and BMW and Mercedes went to when they wanted a good head.

There's some small chance they may know just a bit more---maybe 4-5% more---than all the collected wisdom here on Turbobricks and it seems they had rather short runners.

IF, as the guys here insist the resonance effect fuctions "the same" as on Normal aspirated and IF as we know longer runners gives a lower resonant frequency, and that is supposed to result in improved TORQUE, then looking at the that "designed from the outset as a ONLY turbo engine" and knowing it's intended use, don't you think they woyuld have given that motor some LOOOOOOONG runners---if it was critical?

Want photos?
 
don't sweat it, just shorten it if you think it'll clear like that. The rest of the 'build list' points towards a non-aggressive setup, so don't sweat the effect shorter runners will have. If you're jonesing for a larger plenum, copy sdturbo's manifold.
 
DaytonAE86 said:
Think of the bore/port spacing, unless your talking about just using the plenum off of something with alot of volume, to cut down on fabrication costs (since I can't weld aluminum, but know those who can).
Click to expand...
I know the chances may not be that high; but a mate & I once bought an EFI manifold off an 18RG[TE?] 'cos it lined-up perfectly to the 2.0L Pinto engine we were planning on putting in the Mk1 Escort. The holes where we'd bolt it up were wildly off, but the spacing & runner-shape shape was close to perfect; we would only have had to take a tiny bit of meat off the intake ports to port-match to the intake manifold.

What JohnV says is very true; but if you've got the time to fiddle with the tuning, and there's something that's variable that will fit, then it'd be kinda interesting to give it a try (I must admit, though, I don't think I'd have the patience).
 
John V said:
That entire ENGINE and Manifolds /ports/ everything was designed from a clean sheet of paper as a manifold to be used on a turbo engine.
The designers were who GM and BMW and Mercedes went to when they wanted a good head.

There's some small chance they may know just a bit more---maybe 4-5% more---than all the collected wisdom here on Turbobricks and it seems they had rather short runners.
Click to expand...

With that logic, we should not be messing with these cars at all. The fact is that we are trying to do things that these engines were never designed for. If you told these incredibly smart/talented/good looking engineers to design a 400hp sports car ENGINE/manifolds/ports/etc. things might look a bit different. That said, I think the stock runner length is about right for what most are trying to do but the plenum could be a bit bigger.
 
John V said:
IF as we know longer runners gives a lower resonant frequency, and that is supposed to result in improved TORQUE, then looking at the that "designed from the outset as a ONLY turbo engine" and knowing it's intended use, don't you think they woyuld have given that motor some LOOOOOOONG runners---if it was critical?

Want photos?
Click to expand...

Longer runners to not make more torque. The changes in frequency just change the torque curve.

I's designed as a system. Boost response, camshaft design, and intake/exhaust layout.

It's entirely reasonable that an engine whose turbo or camshaft has been altered from OEM will also require an alteration in intake manifold geometry.

I do think it'd be worth doing the math first rather than just guessing though, if that's what you mean.
 
sdturbo said:
With that logic, we should not be messing with these cars at all.
Click to expand...

What?
Of course we can mess with them and have loads of fun, but somewtimes we mightstop repearing stuff we read from "some guy" and look at specific solutions.
You know? Measure what we've been told and read against REALITY.



The fact is that we are trying to do things that these engines were never designed for.
Click to expand...

So why not consider LOOKING at similar lager bore, shorter stroke 2.0-2.3 motors that WERE designed from the get go to be a a World beater competition motor?
The good Volvo redblocks have a lot of the elements to make it a rewarding motor, and air moving thru some runner of a given volume doesn't know if that runner is bolted to a Volvo B234 or a YBG Ford.

If you told these incredibly smart/talented/good looking engineers to design a 400hp sports car ENGINE/manifolds/ports/etc. things might look a bit different.
Click to expand...

The motor I'm suggesting it MIGHT be rewarding to look at the intake design did have the design brief of being able to make a reliable 500bhp in GpA BTCC, DTCC and similar.

That said, I think the stock runner length is about right for what most are trying to do but the plenum could be a bit bigger.
Click to expand...

That's nice.:)
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