EFI intake plenum volume on a supercharged engine??

Fordman75

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I'm working on laying out my engine plans and I've been doing some research but am getting conflicting info. I'm going to run an Eaton M112 supercharger on my 300 and have decided to go with EFI.

I'm going to lay out the intake system so it's in this order. Air cleaner, supercharger, intercooler, throttle body, intake plenum. I'm going to run a ported stock lower efi intake. But I plan to fab up a custom upper intake/plenum.

My question is what volume should the plenum be. I know on a naturally aspirated engine it should be around 50%-70% of the engine size. But on the supercharged engine is where I'm getting some conflicting information. Some are saying it should be larger ( up to 150% of the engine size ) . And others are saying it should be smaller then a plenum on a NA engine.


So what's the correct answer? Bigger, smaller or the same size as a NA engine? :?
 
That's quite a can of worms to be opening. I wrote a really technical sounding response but then realized that it was just a long way of saying I don't know. Not sure that anyone does. If plenum volume makes a huge difference, then I think you'd be able to find hard data from the dyno saying specifically "do this" and "don't do this". I've never found such information, and it looks like you haven't had much luck either. From this I'll conclude that it doesn't matter enough to worry much about. With natural aspiration you rely on the atmosphere, pressure waves and crossed fingers to get the most power out of your engine. Forced induction, on the other hand, leaves you relying on common sense and self control to avoid making too much. I don't think you'll be held back by any sensibly sized plenum.

Just my thoughts. I'm not an expert on, well, anything really. But it's still fun to discuss!
 
Id concur, I doubt that it will make one zot of difference, and your more likely to need to build something that isnt ideal because of physical limitations, QED stop worrying.
Wouldnt you throttle go before the compressor?
A7M
 
I have to fabricate my upper intake so I was just thinking if I had to build one I'd like it to perform as good as I can get it to. If it doesn't matter I'll just make the plenum out of a 5" O.D. pipe and do a slope cut that decreases in size towards the farthest cylinder. I just didn't want to go too large and lose too much throttle response. :lol:

I'm not sure where I'm going to mount the intercooler yet. It may need to go behind my front bumper. Which is going to be 6" or so in front of my front clip. The supercharger is going to be remote mounted( not mounted on the intake ) . Again I'm concerned with throttle response so I thought it would be better to mount the tb on the intake and run a bov.
 
Do you need an intercooler, if your under about 100kPa boost and your supercharger is fairly efficient adiabaticly then you shouldnt need one, particularly in Minesota, its cold there isnt it? And as to a Bov I think that a bit of unneccesary romance as well.
If you want throttle responce then keep all you plumbing to a minimum, thus no IC, there fairly expense too and given that your only on full noise for a few seconds why have it.
Dont just go with whats fashionable by the Skyline boys, most of them know nothing, your 300 isnt likely to rev much either so you have to fatten out the lower rpm, which is where the most impressive results are.
Its going in the truck after all!
A7m
 
The plenum is important. It's there to cushion the air, for static regain, to stop scavaging between runners, etc. It should ideally be tapered for regain, it should have an overhang on the dead end and a spigot between it and the throtlle body.

To ballpark size you will need:

Intake opening (advertised)
Intake closing (adv)
Exhaust opening (adv)
Exhaust closing (adv)
Exhaust port area
Intake port area
Boost pressure
Preferred RPM
Bore and stroke
Compression ratio
If intercooled
 
Talk about confuse some folks.

Use the OE efi manifold, mount a roots blower to it, then it would protrude from the center of the hood, giving folks the impression its a v8 but wonder why na hell does it sound like that. :D
 
aussie7mains":3hme5agg said:
Do you need an intercooler, if your under about 100kPa boost and your supercharger is fairly efficient adiabaticly then you shouldnt need one, particularly in Minesota, its cold there isnt it? And as to a Bov I think that a bit of unneccesary romance as well.
If you want throttle responce then keep all you plumbing to a minimum, thus no IC, there fairly expense too and given that your only on full noise for a few seconds why have it.
Dont just go with whats fashionable by the Skyline boys, most of them know nothing, your 300 isnt likely to rev much either so you have to fatten out the lower rpm, which is where the most impressive results are.
Its going in the truck after all!
A7m

I asked that question here and the answer everyone seem to tell me was yes. To tell you the truth I have no idea how much 100 kPa is. :oops: I was shooting for 7-10 pounds of boost but depending on the pulley I run it could be as high as 12-14 pounds.

It's only cold in Minnesota 6 months out of the year.:lol: Our temps around here can range from -20 F to + 100 F.

But I will also be running multiport fuel injection with E85 which has a 105 octane rating and also acts like a chemical intercooler.

I've got a very aggressive driving style. I'm on the gas alot! And I also tow some very heavy loads. so the throttle is going to get used.:lol:

I don't really think I need an intercooler. But I'd rather spend the money now and be safe instead of finding out later that I should have ran one.

I could care less what the import guys do. And I could care less what the intercooler looks like ( It most likely won't be seen anyways ) . I just want my engine to live. So if an intercooler will cut down the chance of detonation then I'll run one.

It's going to see a max of 5500 rpms. which isn't a lot for a import but it's quite a bit for a 300. And with the gearing my truck has I'm not concerned about the low end nearly as much as I am the mid range and top end. At 70 mph my engine will be turning over 3000 rpm.

This may be a truck but I drive my trucks like they are Mustangs.:lol:

XPC66":3hme5agg said:
The plenum is important. It's there to cushion the air, for static regain, to stop scavaging between runners, etc. It should ideally be tapered for regain, it should have an overhang on the dead end and a spigot between it and the throtlle body.

To ballpark size you will need:

Intake opening (advertised)
Intake closing (adv)
Exhaust opening (adv)
Exhaust closing (adv)
Exhaust port area
Intake port area
Boost pressure
Preferred RPM
Bore and stroke
Compression ratio
If intercooled

That is the plenum design I had read about and was planning on making. As for the rest of the info it looks like I should have got a mathmatics degree.:lol:

I take it you are refering to the cam/valve timing for the Intake and exhaust opening and closing? :?

So it looks like the intake will have to be the last part of the engine I build.



inline300":3hme5agg said:
Talk about confuse some folks.

Use the OE efi manifold, mount a roots blower to it, then it would protrude from the center of the hood, giving folks the impression its a v8 but wonder why na hell does it sound like that. :D

This is my reason for this post. Everywhere I looked I was getting a different answer. :lol:

I'm going to use the stock EFI lower intake but I'm making my own upper intake. I'm running an Eaton not a roots blower. And with my cab body lift and the bubble hood there is no way anything mounted on the engine would stick thru the hood. :lol:
 
If your measuring boost as kpa, roughly 100kpa is atmospheric pressure or 0 psi.

so if you read 155 kpa, you would have about 8psi

To convert kilopascals to pounds per square inch, multiply the kpa value by .14503773773020923

.14503773773020923 X 55kpa = 7.9psi
 
Ok I looked up a convertor to convert kPa to psi. 100 kPa looks to be just a hair over 14.5 psi. There is a very very chance that I'd be running that much boost.

It looks like I'll most likely be running 55-70 kPa of boost. So should I run an intercooler or not? :? I know the Eaton M112 supercharger I'm going with is pretty efficient. Better then a roots but worse then a Whipple. But like I said I'd rather be safe then sorry. :lol:
 
Fordman75":37icme0r said:
That is the plenum design I had read about and was planning on making. As for the rest of the info it looks like I should have got a mathmatics degree.:lol:

I take it you are refering to the cam/valve timing for the Intake and exhaust opening and closing? :?

No not the cam events, the advertised i.e. valve events. Cam events are pretty useless for anything, but for grinding, big noting and one or two calcs. It will be the figures associated wth bigger duration numbers e.g the cam events might have a duration of 204°, while the corresponding advertised might be 250°.
 
Fordman75":1wz6u5z1 said:
Not in conventional location. :lol:

I'd run an IC, even if it's just a baby one. The gain in density usually outweighs the introduced pressure drop.

You sure you want to install a S/C...turbo's are so much more rewarding?
 
XPC66":10u627a9 said:
No not the cam events, the advertised i.e. valve events. Cam events are pretty useless for anything, but for grinding, big noting and one or two calcs. It will be the figures associated wth bigger duration numbers e.g the cam events might have a duration of 204°, while the corresponding advertised might be 250°.

Ok I understand now.:lol:

XPC66":10u627a9 said:
Fordman75":10u627a9 said:
Not in conventional location. :lol:

I'd run an IC, even if it's just a baby one. The gain in density usually outweighs the introduced pressure drop.

You sure you want to install a S/C...turbo's are so much more rewarding?

Ok, any sceintific info I'll need for figuring intercooler plumbing size?

I've always liked Eaton superchargers ever since I drove my younger brother's old T-bird Supercoupe that had the supercharged 3.8L. I loved the sound of the suprcharger and the instant response when you stepped on it. And the breaking the rear tires loose while at 45 mph was pretty fun too. :lol:

I've driven a couple turbocharged cars. But I just prefer a blower. :D
 
Preferably an intercooler with static regain header tanks both ends, spigots equal to or greater than your throttle plate, 1 psig drop at full flow and about 75% or greater heat rejection efficiency (unless you are stuck for space, then use something like a Nissan Godzilla unit).

Ballpark your throttle body sizing to 1psi drop and 30m/s. Whatever the subsequent plate size, your req'd minimum piping ID will follow.
 
Nope not going to use the stock upper intake! But you might like the way way I'm going to set it up. :lol: I'm going to have a carb scoop with an aircleaner/s mounted on top of the supercharger.



Thanks for the link. I've seen that one many times. His is a whipple supercharger. And that supercharger probably cost as much if not more then my entire engine will cost! :shock:
 
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