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Location:
Newcastle, NSW
Registered:
May 2004
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Multiple throttle bodies + forced induction
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Wed, 21 September 2005 00:55
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hey i was just reading an efi vs carby thread and it was stated that throttle body per cylinder setups gave greatly increased engien response and flow. given this is for n/a engines, i can only assume the better flow and response would be even more noticable on FI engines? what do u guys reckon..and why?...im sort of trying to get ideas on ultimately where to take my gtfour...EVENTUALLY i want to do something really different with it.
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Location:
Perth
Registered:
October 2003
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Re: Multiple throttle bodies + forced induction
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Wed, 21 September 2005 01:37
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Look at the factory setup on the RB26DETT, SR20DET GTiR version and the 2L in the Cosworth Sierra.
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Location:
Rosanna, Melb
Registered:
June 2002
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Re: Multiple throttle bodies + forced induction
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Wed, 21 September 2005 01:45
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I have seen multi throttle bodies run on FI engines (namely turbo 20Vs, and GTRs) and clearly it works. However I don't think they are quite as important as on an NA car.
This is because ITBs become useful when chasing that extra little bit of flow (and therefore power) on a hard built NA engine. On an FI engine they should do the same thing, but the same result could be achieved but turning the boost up ever so slightly. Less effort for the same result.
Also I've read that when chasing BIG horsepower, the multithrottles on GTRs are ditched for a big single. No solid backup for that last one though.
Hen
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Location:
Brisbane
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Wed, 21 September 2005 02:54
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GTR's are converted to a big single throttle purely for cost reasons. A custom plenum is cheaper than 6x larger throttles.
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Wed, 21 September 2005 03:01
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| Henn wrote on Wed, 21 September 2005 11:45 |
Also I've read that when chasing BIG horsepower, the multithrottles on GTRs are ditched for a big single. No solid backup for that last one though.
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Usually because one big throttle body is cheaper than 6 slightly bigger throttle bodies. Also drag engines/dyno queens aren't usually chasing instant throttle response or a flat midrange.....
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Registered:
September 2005
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Re: Multiple throttle bodies + forced induction
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Wed, 21 September 2005 04:27
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| Norbie wrote on Wed, 21 September 2005 12:24 |
GTR's are converted to a big single throttle purely for cost reasons. A custom plenum is cheaper than 6x larger throttles.
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i think you will find its also for tuning reasons. Its a lot easier to tune a single throttle setup then a multiple set up. However multiple throttle set ups when done right, seem to be the better result.
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Location:
Terrigal
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Wed, 21 September 2005 04:43
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I was considering doing this on my 3S-GTE project.
Was going to use 20v blacktop throttles with an adapter plate and then a plenum over them.
Ended up getting a bit costly so stuck with the standard single throttle setup.
But good luck with it, very interested to see how you get on.
I might investigate it again down the track.
Cheers
Joel
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Location:
Newcastle, NSW
Registered:
May 2004
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Location:
perth wa
Registered:
June 2005
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 01:49
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on the topic of gtr's..
ive read some workshops ditch the multi throttle setup for a BIG single throttle because at full throttle the single throttle will cause less of a restriction than the six smaller ones.
i havnt seen any dyno proof of gains tho...
cheers
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 02:17
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| t18_psi wrote on Thu, 22 September 2005 09:49 |
ive read some workshops ditch the multi throttle setup for a BIG single throttle because at full throttle the single throttle will cause less of a restriction than the six smaller ones.
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Unless it's a massive throttle body, I doubt it. From what I've read it's to do with cost and ease of tuning.
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 07:06
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| t18_psi wrote on Thu, 22 September 2005 11:19 |
ive read some workshops ditch the multi throttle setup for a BIG single throttle because at full throttle the single throttle will cause less of a restriction than the six smaller ones.
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This is fine if your at WOT all the time.
It would be hell for daily road driving.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 07:15
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mmmmm multiple throttlw bodies 
as everyone has suggested, better response, better mid range, less top end. less useful on FI than NA, but still good (see rb26dett etc etc)
cheers
ed
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Location:
Sydney
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 08:26
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Nice plenum Ed 
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Location:
Newcastle, NSW
Registered:
May 2004
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 11:11
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| ed_ma61 wrote on Thu, 22 September 2005 17:15 |
as everyone has suggested, better response, better mid range, less top end. less useful on FI than NA, but still good (see rb26dett etc etc)
cheers
ed
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ed if i was to use 4 stock 3sgte throttle bodies on a custom manifold of some discription, would there nessecarily be a negative effect on top end?
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 11:22
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unless it's a W16 engine I can't see why you'd want to. ITBs are a lot smaller than single throttles. (and I'm 90% sure the 3s in all forms is single throttle/plenum)
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Location:
Canberra
Registered:
July 2005
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 11:57
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BEAMS has quads AFAIK  no 3SGTE had quads though. 4 x 3SGTE throttles on a cusso manifold would probably suck. I'd hazard a guess that you'd have a lot of difficulty getting a plenum to fit around such big ass throttles, not to mention port spacing could be a limiting factor!
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Location:
Menai area of Sydney
Registered:
June 2003
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 23:03
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I didn't think the BEAMS 3SGE had quad throttles. 3SGTE TB's are tiny as well, but still larger than I'd want to use as ITB's
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Location:
Brisbane
Registered:
March 2004
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 23:16
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I remember when i had a gen 2 3sge, in the manifold there was some sort of tvis setup but it was on all 4 runners but they where about 6-8" from the head could something like that be setup to be used as TB's? I guess the main concern would be if it could handle high psi. Just a thought
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Thu, 22 September 2005 23:54
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| Manny wrote on Thu, 22 September 2005 18:26 |
Nice plenum Ed
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piece of crap 
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Location:
Rosanna, Melb
Registered:
June 2002
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 01:24
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| Scorpion wrote on Fri, 23 September 2005 08:17 |
Individual throttle bodies per cylinder benefit n/a as you can tune the length and diameter to set up standing pressure waves.
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That's true as far as my basic understanding goes.
| Scorpion wrote on Fri, 23 September 2005 08:17 |
Forced induction (depending on amount of boost) can override these standing waves and with enough boost cause greater volume of air intake anyway.
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I disagree slightly here. Having higher than atmospheric pressure in the plenum shouldn't affect the whole standing wave issue (other than maybe a change in their speed of propogation), you can still tune your runners and bellmouths on an FI engine. The boost doesn't "override" the intake tuning.
It's just that it is often not worth the effort doing so much intake tuning on an FI engine as you can just up the boost a little for the same result.
Hen
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Location:
Tasmania
Registered:
April 2003
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 01:51
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Hi,
One of the biggest advantages of ITB in a N/A set-up is the ability to fire the injector down the length of the T/B trumpet. This leads to a superior atomisation of the fuel.
A good place to see this is with the old 2 litre Super Tourers. The were putting out ~300hp from 2 litres.
There are photos of the Ferrar 550 that was privately run at Le Mans that shows injectors firing down the trumpets to all 12 cylinders.
Another point, one large T/B doesn't have anywhere near the flow ability of ITBs.
Cheers,
Justin
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 03:29
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^^^^
thats crap... sure, upstream injectors are 'a' benefit, but certainly not the 'main benefit'...
as for mass flow capability... hmmmm... so tell me why a 'driver's vehicle' would have ITBs, but a crazy WOT drag car runs a single large throttle?
and yes, harmonic tuning is still just as relevant on an FI engine as it is in NA...
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 03:46
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Anyways....
it can be done. However, there are cheaper ways of ensuring good throttle response from a FI car than by setting up ITBs. Plenum design, runner length, well matched roller bearing turbo....you'd be doing all this anyway so why not be smart about it rather than adding an extra degree of difficulty?
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 04:54
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more pics of ^^^^^^ f1 engine??
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 05:14
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| M.W.P. wrote on Fri, 23 September 2005 14:20 |
Factory sequential injectors are setup to spray fuel onto the back of the closed inlet valves which then causes the fuel to evaporate which gives better fuel economy and low-rpm torque.
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not necessarily true  , it depends greatly on the particular engine involved as to what phasing is the best for power or emissions, and those two points to not necessarily coincide.
many factory injectors actually spray against the side of the ports, which helps atomisation not from the jet of fuel itself, but from the rebound/spray off the port wall
for high rpm motors, because of the high intake velocity, more time may be required for decent mixing, and time = distance. can't afford to have sharge stratification in a high $ motor (unless it is designed for it ).
for a motor which is NOT going to be run at WOT all the time, there is little benefit in fitting high injectors, and the couple of % difference will not be noticed/useful.
perhaps 
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 05:46
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| ed_ma61 wrote on Fri, 23 September 2005 14:24 |
more pics of ^^^^^^ f1 engine??
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Yeh, lots...
I cant find them on the net again, so ill have to upload them.
Will take a little while.
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Location:
nelson, new zealand
Registered:
October 2004
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Re: Multiple throttle bodies + forced induction
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Fri, 23 September 2005 06:44
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| Quote: |
I was considering doing this on my 3S-GTE project.
Was going to use 20v blacktop throttles with an adapter plate and then a plenum over them.
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guess what the TRD intakes for the 3sge are made from...
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Location:
Sydney
Registered:
April 2004
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Re: Multiple throttle bodies + forced induction
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Sat, 24 September 2005 23:54
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| Henn wrote on Wed, 21 September 2005 11:45 |
I have seen multi throttle bodies run on FI engines (namely turbo 20Vs, and GTRs) and clearly it works. However I don't think they are quite as important as on an NA car.
This is because ITBs become useful when chasing that extra little bit of flow (and therefore power) on a hard built NA engine. On an FI engine they should do the same thing, but the same result could be achieved but turning the boost up ever so slightly. Less effort for the same result.
Also I've read that when chasing BIG horsepower, the multithrottles on GTRs are ditched for a big single. No solid backup for that last one though.
Hen
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Couldnt have stated it better myself. Once you cross a certain threshold on bigturbo engines you just basically want to get as much air in there as possible
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...so im more or less trying to build my knowledge base so i can decide where to take it when the time comes 
