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Fabricating Aluminum Intake Manifold, need help

7K views 10 replies 6 participants last post by  Project89 
#1 ·
Hello all and Happy Holidays.

I have a stroked Volvo B20 engine that I am building and will be turbocharging and I am looking into fabbing a new intake manifold out of aluminum, yes I do weld aluminum.

My question is about tuned port, pressure waves, runner size to name a few. A cursory search found this article, http://mysite.verizon.net/vzezeqah/sitebuildercontent/sitebuilderfiles/inductionsystems.pdf

Volvo does have a Fuel Injection manifold that I can use, but space will probably be an issue, hence the idea of creating a new intake manifold to make more room for the turbo.

This article points to pressure waves and equations for, as far as I can tell a NA engine. Do the same principles hold true for a Forced Induction?

Any help or direction is appreciated.
 
#3 ·
Thank you for the replies.

Because the intake and the exhaust are on the same side I have been wondering about throttle body and plenum on the other side of the engine with the runners going over the top of the valve cover and then doing a 180° to the intake valve. I am a little leary about the 180° turn.

Here is the stock intake look. With a turbo in there it will be tight.


This is from another forum, but the basic design of what I am thinking about.
 
#4 ·
In my opinion, tuned port, pressure waves and runner size can be tossed out the window when you go from naturally-aspirated to turbocharger-aspirated. All you will need is a plan to deliver the proper air/fuel ratio to the motor and a way to keep the charge cool. In your case, using FI simplifies keeping the A/F ratio in line. I like your "over the top" runners, same as the intake system on my old '91 Ford 300 six cylinder motor, but I think if I were doing it, I would fabricate an intercooler to fit in that space also.

I understand that you have little room on the driver's side for the turbo unit, but weigh making room there by doing a little surgery on the existing parts against running exhaust tubing to the other side of the motor to run the turbine. I have made the comment many times that with a cutting torch, a Sawzall, a MIG and a good hand grinder, you can make anything fit anything.

I think if I were doing your project, I'd mount everything on the driver's side by doing some surgery, then I might mount an air-air intercooler down low in front of the car.

I'm certainly not the forced induction guru on this board, just presenting a few thoughts......good luck.....:thumbup:
 
#5 ·
In my opinion, tuned port, pressure waves and runner size can be tossed out the window when you go from naturally-aspirated to turbocharger-aspirated. All you will need is a plan to deliver the proper air/fuel ratio to the motor and a way to keep the charge cool. In your case, using FI simplifies keeping the A/F ratio in line. I like your "over the top" runners, same as the intake system on my old '91 Ford 300 six cylinder motor, but I think if I were doing it, I would fabricate an intercooler to fit in that space also.
That is what I needed to hear, I did not think that the pressure waves, length, etc, etc held that much importance when going to forced induction.

My CR is going to be right around 9:1, with a turbo I know that is higher than recommended. Can I place knock sensors on the engine to prevent detonation? If so, where on a loud and noisy 4 cylinder would be the best place?

Thanks
 
#7 ·
long time ago.

50 years ago my engineering college project was designing a tuned injected manifold, as I remember tuned length was calculated using temperature , density and cam and rpm for max horspower. to get the numbers right. But I needed more money to finish college and sold my roadster. but I did get an A on the design project.
 
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#8 ·
I would copy the stock intake out of larger 1/4 thick wall alumiunum tubing.
Do you mean copy the inside diameter of the stock intake manifold? The original engine size is 2.0, I am stroking it to a 2.3. Will this make a difference in tubing size? I was thinking that 1/8th of an inch for the intake runners would be thick enough?? No? :confused:

I am also planning on reinforcing the runners by welding some 1/8th inch between the runners, like webbing. The flange I agree needs to be at least 3/8 inch.

Inside the intake/plenum should I run air horns or just smooth it down with the same idea of the air horn?

Thanks again for the input!!
 
#9 ·
IMO I would keep inside diameter the same and go fairly thin on the tubing especially with gusseting; no sense in adding weight. The tubing gauge from the early 90's Geo Prizm/Toyota Corrolla intake should be fine. You may want to look up some photos of these manifolds as it could be an alternative to the over the top (which is a GREAT design and will yield good low end torque prior to boost).

The engine will be used for low end accelleration/cruise, not just boost and a good normally aspirated design should be adhered to for optimization over the entire range. Log style exhaust manifolds should be avoided as well.
 
#10 ·
what cam/s do u have in the engine and what size turbo charger
whats the engines redline and were do u want it to make the most power

on my 2.8L turbocharged v6 engine i picked up 28hp and 35ftlbs at the rear tires with a manifold i made for it

i shortened the runners 3 inches and and increased plenum volume almost 2.5 times over stock

the plenum volume increase helped it pick up power uptop but made off boost,low rpm driving responce a tad sluggish
 
#11 ·
here one o fthe ones i built . i reused the stock lower and middle section but did a whole new top

heres the cutup stocker

and what i made










urs will be much simpler to make over what i made for my car

for the plenum u want a flat bootom were the runners meet it, and u want all entrys bellmouthed , then use a half round plenum , u can tune runner lenght a lil bit to fine tune the intake

what i would do is make the plenum bolt to the runners , so u can make 2-3 diff sets of diff lenght runners and see what works best
 
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