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I supported Toymods
Banned User
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May 2002
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Inlet manifold designs
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Wed, 03 March 2004 12:42
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Well i'm nearing the time to start getting a inlet manifold made for my 3S-GTE but i'm not sure how to get it made.
So does anyone have any good designs?
Any help? Thanks
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Location:
Brisbane
Registered:
June 2003
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Re: Inlet manifold designs
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Wed, 03 March 2004 13:05
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id design it - just a thought.
to have a rail with an extra injector in it. My dad's Vl commodore used to have 7 injectors, and it made a big difference.
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Location:
Finland
Registered:
November 2002
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Re: Inlet manifold designs
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Wed, 03 March 2004 15:36
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What made you decide to not to modify and use your existing one?
Or is my conception wrong?
And V8_MA61 how on earth is 7 injectors going to perform better? Is your dads commodore 7 cylinder  ? Dont you think that 1 right sized injector per 1 cylinder works best on most of the applications?
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I supported Toymods
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May 2002
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Re: Inlet manifold designs
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Wed, 03 March 2004 21:16
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The current manifold has the TB in the middle was as I need it on the end.
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Location:
Terrigal
Registered:
May 2002
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Re: Inlet manifold designs
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Wed, 03 March 2004 23:28
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Large tube with internal bellmouths.
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I supported Toymods
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Re: Inlet manifold designs
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Wed, 03 March 2004 23:40
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Should the plenum be tapering, or is that less critical as it will be a forced induction setup?
I seem to remember plenum volume being an issue - something like 3x the engine capacity.
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I supported Toymods
Banned User
Location:
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May 2002
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Re: Inlet manifold designs
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Thu, 04 March 2004 00:28
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Yeah thats what I was wondering about. I have seen alot plenums that taper off at the back. Also i'm not 100% sure what volume it should be as I have read of a few formulas to use.
Anyway, whats the idea of the bell-mouths? Got any pictures that can explain it?
Thanks
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Location:
Adelaide
Registered:
September 2003
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Re: Inlet manifold designs
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Thu, 04 March 2004 00:33
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If you can, get a hold of Corky Bell's book on Turbos, as he covers most of your questions there.
The best design for the intake manifold is to have the T/B inlet in the middle, right where it is now.
There are successful manifolds either way, but there have been known problems for an inline engine with the T/B at the end !!
Cheers
Michael B
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Inlet manifold designs
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Thu, 04 March 2004 00:36
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An easy way to do it would be to use the original runers and weld on a new fabricated plenum per your specs.
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I supported Toymods
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Re: Inlet manifold designs
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Thu, 04 March 2004 00:54
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That was the original plan, but the problem is that the runners turn directly up from the flange to put the plenum above the head.
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Location:
Brisbane
Registered:
June 2003
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Re: Inlet manifold designs
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Thu, 04 March 2004 04:02
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| Jayem wrote on Thu, 04 March 2004 01:36 |
What made you decide to not to modify and use your existing one?
Or is my conception wrong?
And V8_MA61 how on earth is 7 injectors going to perform better? Is your dads commodore 7 cylinder ? Dont you think that 1 right sized injector per 1 cylinder works best on most of the applications?
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There is an extra injector for when the car comes under high boost. yes it does make a difference.
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I supported Toymods
Location:
Perth
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May 2002
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Re: Inlet manifold designs
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Thu, 04 March 2004 04:44
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What is the point of doing that when you can have 6 equal sized injectors doing a more accurate job? Sounds like a bandaid solution to me 
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Location:
Brisbane
Registered:
June 2003
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Re: Inlet manifold designs
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Thu, 04 March 2004 04:48
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to throw more fuel in with the force of the turbos. Whats so difficult to understand about that?
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I supported Toymods
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Re: Inlet manifold designs
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Thu, 04 March 2004 04:50
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Used to be the way it was done.....run a pressure regulated microcontroller - when intake pressure was X, the microcontroller switched on the injector. Bodgy, but it worked.
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Location:
Brisbane
Registered:
June 2003
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: Inlet manifold designs
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Thu, 04 March 2004 05:19
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Oh I understand how it works, it just doesn't seem as good an approach as having larger injectors handling whatever conditions the turbo was producing.
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Location:
Brisbane
Registered:
May 2002
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Re: Inlet manifold designs
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Thu, 04 March 2004 06:28
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Yes, microfuellers (aka 7th injectors) were popular back in the days when people didn't understand the benefits of upgrading the ECU and/or were too cheap to do the job properly. It's definitely very bodgy, you get into all sorts of problems with even fuel distribution, atomisation etc. For relatively low power it works OK, but if you want to make serious numbers it's a great way to blow up your engine.
These days you'd have rocks in your head to do it. Just upgrade your injectors to the required size and upgrade/modify the ECU to suit.
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Lost in the K hole
Registered:
May 2002
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: Inlet manifold designs
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Thu, 04 March 2004 12:42
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Ok the plan so far is to have a tapered plenum with bellmouths internally and a volume of about 3x engine capacity.
What I need know now is what effect does the runner length have on performance, and how much should the plenum taper towards the rear?
Also can anyone point me towards some pictures of custom made manifolds that I may be able to get some ideas from?
Thanks
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I supported Toymods
Banned User
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Re: Inlet manifold designs
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Fri, 05 March 2004 00:07
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| bbaacchhyy wrote on Thu, 04 March 2004 10:33 |
If you can, get a hold of Corky Bell's book on Turbos, as he covers most of your questions there.
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Is this the book your talking about: Maximum Boost: Designing, Testing, and Installing Turbocharger Systems
If so does it have pictures in it of inlet manifolds?
Thanks
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 00:21
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long runers = low torque
short runners = higher torque
there IS a thread on here discussing runner length, belmouths and plenums. be fucked if i can find it. theres a heap of good links in there from memory...
ill just go check the old forums...
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I supported Toymods
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Re: Inlet manifold designs
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Fri, 05 March 2004 00:28
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Yeah I remember seeing some threads on here about bell mouths and runner length, but the search feature isnt very friendly 
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I supported Toymods
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:19
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| ed_ma61 wrote on Fri, 05 March 2004 11:21 |
long runers = low torque
short runners = higher torque
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I have a dumb feeling it's the other way 'round.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:26
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sorry, ill clarify:
long runners = good low rpm torque
short runners = lost low end torque but a mild improvement in high rpm torque
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Location:
Terrigal
Registered:
May 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:30
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Just clarifying what ed_ma61 said is correct. I've read this numerous times.
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I supported Toymods
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Perth
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May 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:31
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The way I always remember it is the 3UZFE intake manifold. At low RPM it has to travel all around the piping before going into the engine whereas at high RPM the line of 8 throttles opens up and provides a short path for the air
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Registered:
August 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:36
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long runners should also improve peak torque
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:39
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frank, if you want to remember it in a more technical way - just think LOW frequency sounds/tones have a LONG wavelength, whereas HIGH frequency sounds/tones have a SHORT wavelength.
you are, infact, playing with these wavelengths when designing your runner length, trying to set up harmonic standing waves in the runners. so the lower the RPM (and the opening and closing rate of the valve) the longer the wavelength is, thus the loner the runner needs to be to establish a harmonic.
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I supported Toymods
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Re: Inlet manifold designs
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Fri, 05 March 2004 01:59
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Ok so long runners are obviously the pick of the bunch, but how long is long enough?
The standard manifold has the runners looping out from the head and up above the cam cover. If I took the length and diameter of these runners, would this be a good starting point?
I could have the runners come out from the head loop up and out a little, and then loop them down onto a flat plate which would make up one side of the plenum. Hows this sound so far?
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 02:12
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a little loopy.
sorry I'll shut up now.
Friday's do it to me every time.
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I supported Toymods
Banned User
Location:
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Registered:
May 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 02:23
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I just thought I should make my own loops now that they are closing down the rollacoaster at dreamworld
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Registered:
August 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 03:58
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"US based engineering guru David Vizard suggests that a runner length of seven inches at 10,000rpm makes a good starting point. (Note that runner length is the distance from the plenum chamber right to the intake valve seat.)
Add to this another 1.7inches for each 1000rpm less than that which the system is being tuned for. Tuning for peak torque (not peak power) is the norm, so if the engine were being tuned for 4000rpm, a runner length of 17.1 inches (43.6cm) would be required."
-Julian Edgar, 2000 21st Century Performance
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I supported Toymods
Banned User
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Re: Inlet manifold designs
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Fri, 05 March 2004 04:13
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Wow, Thanks for that great bit of information.
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I supported Toymods
Banned User
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Re: Inlet manifold designs
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Fri, 05 March 2004 04:18
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I just checked up and the peak torque is at 4000rpm for the 3S-GTE, so for optimum performance the runners should be 43.6cm.
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Location:
Adelaide
Registered:
September 2003
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Re: Inlet manifold designs
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Fri, 05 March 2004 04:20
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| Cool1 wrote on Fri, 05 March 2004 11:07 |
| bbaacchhyy wrote on Thu, 04 March 2004 10:33 |
If you can, get a hold of Corky Bell's book on Turbos, as he covers most of your questions there.
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Is this the book your talking about: Maximum Boost: Designing, Testing, and Installing Turbocharger Systems
If so does it have pictures in it of inlet manifolds?
Thanks
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Yes, but basics only rather than in depth drawings
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I supported Toymods
Banned User
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Registered:
August 2002
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Re: Inlet manifold designs
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Fri, 05 March 2004 05:15
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Well now you know the size of the plenum and the length of the runners
Time to get to work designing
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I supported Toymods
Banned User
Location:
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Re: Inlet manifold designs
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Fri, 05 March 2004 07:44
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Well I have a design in my head which is basically a copy of the original.
I want to use the idea of the throttle body mounted in the middle of the plenum, the problem is I'm not going to have enough room to attach the intercooler piping to the throttle body in this position.
So to get around this problem I'm thinking of having a tube(3 inch maybe) attached to the plenum and bend it around to be parallel with the plenum and have the throttle body on the end of this.
Hows this idea sound?
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I supported Toymods
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Re: Inlet manifold designs
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Mon, 08 March 2004 10:14
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Ok crutual is the length of the inlet runners? I spend a few hours today trying to figure out how to have longer runners but its just not going to work. Probably 150mm is all I am going to be able to do 
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Location:
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February 2003
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I supported Toymods
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Re: Inlet manifold designs
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Mon, 08 March 2004 11:19
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Thanks mate, that was helpful indeed.
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Tue, 04 January 2005 10:12
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hi how did you go with your plenum designs? i tried the calculater, is 1.6" runner area.
does that seem small? i was using 2" pipe= 3.1" square area.
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I supported Toymods
Banned User
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Re: Inlet manifold designs
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Tue, 04 January 2005 10:34
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I just made a cheap one that will get the car running for now. I'll get someone who knows what their doing to make me one later.
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Tue, 04 January 2005 10:38
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what did you do? i'm getting itchy getting my car going too
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I supported Toymods
Banned User
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Re: Inlet manifold designs
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Tue, 04 January 2005 10:40
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Just a 3 inch pipe with runners hanging off the side!
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Tue, 04 January 2005 11:08
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yep that's all mine is so far
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Inlet manifold designs
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Tue, 04 January 2005 11:09
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Bit of a backtrack, but thought I'd give my 3 cents on the whole extra injector thing... They're a very poor/cheap way to get extra fuel in where it's needed, but do have the advantage of allowing the latent heat of the fuel evaporating to cool down the inlet manifold a bit.
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Tue, 04 January 2005 11:15
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3s manifold has an extra injector, dunno weather ill keep it, or maybe.....water-metho....nah thats silly
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Inlet manifold designs
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Tue, 04 January 2005 11:58
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Nitrous 
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Location:
Wollongong
Registered:
November 2004
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Re: Inlet manifold designs
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Tue, 04 January 2005 12:04
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| rokusan wrote on Tue, 04 January 2005 22:15 |
3s manifold has an extra injector, dunno weather ill keep it, or maybe.....water-metho....nah thats silly
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Keep it...
I'd suggest keeping the extra injector for a tuners perspective...
Large injectors are harder to tune (Same amount of time, huge amount of fuel) therefore, to get the right amount of time takes LOTS of tuning, and is usually unable to be done...
If you run 6 injectors, you will need a smaller size, then, set the 7th up for when boost comes on...
Means tuning is easier...
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Tue, 04 January 2005 12:09
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ok, so just behind the TB ok?
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Inlet manifold designs
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Tue, 04 January 2005 12:16
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Depends how big the injectors are anyway. Unless they're something silly like 1200cc bucket fillers, then a decent (e.g. Motec) ECU can do a pretty good job of keeping them in line anyway.
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Location:
Brisbane
Registered:
January 2005
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Re: Inlet manifold designs
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Wed, 05 January 2005 06:49
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43.6cm runners sounds good, I use the old 14inches rule for all personally but anyways
The plenum for NA cars should be 2 x engine capacity in cc
Not sure about turbo cars, look at a GTR, tiny plenum. I think they have tiny plenum to keep velocity up cause of there very short runners.
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I supported Toymods
Banned User
Location:
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Re: Inlet manifold designs
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Wed, 05 January 2005 06:58
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Regarding plenum volume, Corky Bell says:
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The plenum volume should be a function of engine displacement-in general, 50-70%.
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From all the experienced engine builders I have spoken to, they have all backed up this claim. 2 - 2.5 times engine capacity is a myth!
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Wed, 05 January 2005 10:38
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had a good chat with paul gilbert from the head shop about runners today as he's done the head, he's getting the flow tests out to do some calc's, told him about our glass plenum idea, and matching runners to port size. he said 8" ok, but 11" perfect! and theres 3.5" to the port seat so it might just fit on ok, i'm going for 1 litre per runner i hope it all adds up, will find out more tommorrow
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Location:
Brisbane
Registered:
January 2005
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Re: Inlet manifold designs
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Thu, 06 January 2005 01:47
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With the 50-50% rule, some manufacturers seem to use that (like the mirage - what plenum!)
I beleive that plenum size depends on the runner length and diameter, also depends on whether your after torque or power. I small plenum will increase torque as it increases the velocity of the air, a large plenum will offer no restriction so good for top end power.
I guess the only real answer is experimentation. Make a large plenum, then 'tune' it by filling the plenum slowly with something to reduce its internal size.
Ultimately you want variable runners like the mazda quad rotor sliding trumpets. Or even what most manufacturers do is to have a secondary chamber in the middle of the runners and a ECU controlled butterfly to direct air to or around it.
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Location:
western queensland
Registered:
September 2004
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Re: Inlet manifold designs
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Thu, 06 January 2005 07:51
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sounds like TVIS i was intending to toss that
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Location:
Brisbane
Registered:
January 2005
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Re: Inlet manifold designs
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Thu, 06 January 2005 10:24
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tos the tvis, it does FA
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Location:
Adelaide
Registered:
December 2004
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Re: Inlet manifold designs
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Thu, 06 January 2005 17:55
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Actually TVIS makes a big difference on a stock engine - if you remove it you will see a slight increase in top end but a substantial loss of torque across the range. Once you start upping the power output of the engine TVIS will be quite a restriction and is best removed.
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