View Full Version : Multiple TB questions


xfactor_pitbulls
05-29-2006, 01:01 PM
I plan on fabbing up either an adaptation of an existing intake with a segmented plenum and 4 TBs or building a sheetmetal with 4 from scratch. If I didnt go that route, I already decided to use a single 105mm accufab with a single plane intake. My thoughts are to use 4 30mm tbs in place of the 105, but it that logical? Please dont try and diswade my thoughts on the initial sizing, it works and that is my starting point. Is there anyway to use the stock pcm to control multiple throttle bodies? How about adapting a TPS to work with the smaller ITBs? The electrical system on LSX setups is my weakest subject, so just playing around with ideas. What are the guys doing to run the accufab 105mm ford, I mean from the TPS aspect? Iam sure many of you guys have had the same ideas as I am having.

Brandon

Haans249
05-29-2006, 01:13 PM
Interesting you just brought that up. I infact was just thinking of something similar. As I was going about the mechanics of it in my head, I started to wonder how you would get a IAC valve somewhere in the mix for idle/driveability. But I have no idea how to solve that, but I haven't really thought about it too much.

As far as controlling the multiple throttlebodies, I don't see that as being a problem. You'll just have to setup one of the throttlebodies with the TPS, and use some sort of adapted mechanics to run all the throttlebodies together, so that they all open at the same time. Therefore when the TPS reads WOT on one throttlebody, all of the throttleplates will be open as well.

xfactor_pitbulls
05-29-2006, 01:57 PM
Interesting you just brought that up. I infact was just thinking of something similar. As I was going about the mechanics of it in my head, I started to wonder how you would get a IAC valve somewhere in the mix for idle/driveability. But I have no idea how to solve that, but I haven't really thought about it too much.

As far as controlling the multiple throttlebodies, I don't see that as being a problem. You'll just have to setup one of the throttlebodies with the TPS, and use some sort of adapted mechanics to run all the throttlebodies together, so that they all open at the same time. Therefore when the TPS reads WOT on one throttlebody, all of the throttleplates will be open as well.

Honestly I dont see making a linkage to run all he cables together being a problem. The IAC and TPS is my only worry. The IAC being the big problem if you have a segmented plenum, obviously you would have to have one per TB. Having a single "control" TB for the TPS makes sense. I need to study what they are doing with the harrop alittle more for it to get some ideas. Just dawned on me, I have another contact I can ask about this as well. Have to wait until tomorrow when they are back in the shop. What TBs were you thinking about running? Do they make sense for adaptation?

Brandon

Haans249
05-29-2006, 02:16 PM
I haven't really thought about what throttlebodies to run, but it also just dawned on me that the LS2 based, fly by wire, tb's use automatic throttleplate adjustments to act as the IAC valve. Maybe there is an answer to the Iac valve issue with flyby wire throttlebodies, but that maybe too complicated.
As far as the Harrop intake, i have no clue how they run the IAC aspect, thats a good thought.

Beast96Z
05-29-2006, 02:18 PM
If there's one thing I know about, it's the Harrop. The throttle linkage is controlled from one opening point, just like the LSX type intake. It then has linkage that attaches all the other TB's. The TPS is controlled just like the normal LSX intake and even uses the stock sensor on the bottom of the throttle cam. The Harrop has a single tube that runs down the center of the intake that the stock IAC sensor bolts to. This tube ties into all the runners thus giving you normal IAC control. It's hard to explain in words, so I'll see if I can find the pics that had all these things covered. Not trying to disweigh your TB sizing, but just wondering why you would choose 4 30mm's? Total surface area of the 4 would be less than a 90mm intake. If you think about it, the Harrop for stock cubes uses 8 52mm TB's, and big cubes use 8 55mm TB's. You can't simply multiply 30mm times 4 and get 120mm worth the surface area. Something to do with radius times pie(3.14) blah blah geometry stuff. I'm sure somone will post the formula.

Here's the pics, hopefully Drewman won't mind me posting his pictures:
Go to the last pic in the first set of links and you can see the IAC/TPS stuff. http://www.ls1tech.com/forums/showpost.php?p=3751838&postcount=42


Here's the top.
http://www.ls1camaro.net/freehosting/harrop.jpg

Haans249
05-29-2006, 02:38 PM
That is very true, rough surface area calculations puts the Harrop intake at 16,981 square mm's with the 52mm plates, while the 4 30mm throttlebodies entails a surface area of only 2,826 square mm's, which is not even half of just one 90mm throttlebody, which is at 6358 square mm's. Something along the lines of being closer to the harrop would be to use only two 90mm throttlebodies which will yield an effective area of 12717 square mm's. Much closer to that of the harrop. If you really wanted to get crazy, you could use two holley, or accufab 105mm's and get you 17,309 square mm's, which is right inbetween the small and large version of the Harrop.

My original thoughts were to use two 90mm's mounted facing frontward on the engine, using a simple modified throttlecable to run them both, and then using custom tubing to connect the outside parts of where the IAC valve plugs into, connecting both the thorttlebodies IAC passages from the outside, and then putting the IAC valve into one throttlebodies....is that really mad any sense haha.

xfactor_pitbulls
05-29-2006, 03:19 PM
If there's one thing I know about, it's the Harrop. The throttle linkage is controlled from one opening point, just like the LSX type intake. It then has linkage that attaches all the other TB's. The TPS is controlled just like the normal LSX intake and even uses the stock sensor on the bottom of the throttle cam. The Harrop has a single tube that runs down the center of the intake that the stock IAC sensor bolts to. This tube ties into all the runners thus giving you normal IAC control. It's hard to explain in words, so I'll see if I can find the pics that had all these things covered. Not trying to disweigh your TB sizing, but just wondering why you would choose 4 30mm's? Total surface area of the 4 would be less than a 90mm intake. If you think about it, the Harrop for stock cubes uses 8 52mm TB's, and big cubes use 8 55mm TB's. You can't simply multiply 30mm times 4 and get 120mm worth the surface area. Something to do with radius times pie(3.14) blah blah geometry stuff. I'm sure somone will post the formula.

Here's the pics, hopefully Drewman won't mind me posting his pictures:
Go to the last pic in the first set of links and you can see the IAC/TPS stuff. http://www.ls1tech.com/forums/showpost.php?p=3751838&postcount=42


Here's the top.
http://www.ls1camaro.net/freehosting/harrop.jpg

I was not saying that 4 30's was right, I was asking. Just making mention that if I ran one, it would be a 105mm. I didnt do the math to try and find correct surface area, even if I did it wouldnt have been right. I am just not too proud to admit that. Hence, me posting in this forum. It makes sense what you are saying about the IAC running through a common tube. Just dont know if that would fit will my idea. Obviously there are several very big challenges to overcome, and a variety of ways to get there. Brainstorming is next.

Brandon

xfactor_pitbulls
05-29-2006, 03:23 PM
That is very true, rough surface area calculations puts the Harrop intake at 16,981 square mm's with the 52mm plates, while the 4 30mm throttlebodies entails a surface area of only 2,826 square mm's, which is not even half of just one 90mm throttlebody, which is at 6358 square mm's. Something along the lines of being closer to the harrop would be to use only two 90mm throttlebodies which will yield an effective area of 12717 square mm's. Much closer to that of the harrop. If you really wanted to get crazy, you could use two holley, or accufab 105mm's and get you 17,309 square mm's, which is right inbetween the small and large version of the Harrop.

My original thoughts were to use two 90mm's mounted facing frontward on the engine, using a simple modified throttlecable to run them both, and then using custom tubing to connect the outside parts of where the IAC valve plugs into, connecting both the thorttlebodies IAC passages from the outside, and then putting the IAC valve into one throttlebodies....is that really mad any sense haha.

My thoughts are to use 1 tb per each 2 neighboring runner, each half of the head having 1 tb. If centered on each of the runners and a short run from the runners through the plenum and then into the tb, it would dynamically produce almost the same effect as using 8 ITB. Is my thinking wrong on that? Characteristics of this setup would atleast be much more close to the harrop than a traditional forward or top mount single tb.

Brandon

chuntington101
05-30-2006, 06:48 AM
id go for eight bodies on a V8!

but then ilove the sound and looks, as well as the performance, that indavidual TBs give you! :) also i was brought up on 4 pot running bodies and the noice they make is fantastic at high rpm! also you see much better topend than what you can ever get on a plenum. but with VERY big cams you do loose a little idle quality on bodies.

thanks Chris.

PS. anyone got the Harrop website link????

DavidNJ
05-30-2006, 10:51 AM
http://www.harrop.com.au/

Two things.

First, only one or two cylinders are breathing at a time. So with a plennum, the TB has to handle that. With ITBs, each ITB has to be able to handle the full volume from a single cylinder. With paired cylinders what was required would depend on the firing order and the pairing.

Second, is there an instance of two cylinder intake pairing used in a high performance or race application? All multiple carb setups I know go into a single plenum.

xfactor_pitbulls
05-30-2006, 11:54 AM
http://www.harrop.com.au/

Two things.

First, only one or two cylinders are breathing at a time. So with a plennum, the TB has to handle that. With ITBs, each ITB has to be able to handle the full volume from a single cylinder. With paired cylinders what was required would depend on the firing order and the pairing.

Second, is there an instance of two cylinder intake pairing used in a high performance or race application? All multiple carb setups I know go into a single plenum.

Good points, and I was asking about sizing for just those reasons. Obviously you never would have two cylinders firing at the same time in the pairing, so it would basically be like having a true ITB like the harrop. I was thinking that dividing the plenum would create singular atmospheres and stabilize the engines vaccum and response from shorter distance to the tb opening. My thoughts did change somewhat I about the IAC though. Obviously if you did an open plenum its an easy fix, but if it is divided it isnt that hard to overcome either. Just put very thinly gapped double wall in the divider with a small opening for each section. It would all pull from a standard forward mount LS1 IAC. The only problem with my design though, it might be easier to run an extra air inlet/small air filter dedicated for the IAC. The design has the TBs off to either side, if that wasnt apparent. TPS can again be handled by a single accufab tb already equiped with a ford tps and adapted for LS1 use. Back to the beginning of the post. There are two ways to make the approach from the intake plenum into each of the runners and into the head. One would be like the typical fab sheetmetal intake, individual runners from a center plenum and into the head. The other would be to use half the runners and use rounded divider that tapers outward toward each head runner spliting flow. Again, this would shorten the distance from opening of the head to opening of the TB. It would add volume to the plenum though..........

Brandon

xfactor_pitbulls
05-30-2006, 10:42 PM
Figured more of you tech brainiacs would chime in.

Beast96Z
05-30-2006, 10:46 PM
One aspect you would loose is the single atmosphere for each cylinder. With 2 runners sharing one TB, that still leaves room for contamination of the incoming air charge. Seems like you would loose some of the "driveability" factor that is so great with the ITB set-up. However it may still be better than a single inlet manifold. If it is economically feasable, it would be interesting to see the results.

xfactor_pitbulls
05-30-2006, 11:18 PM
One aspect you would loose is the single atmosphere for each cylinder. With 2 runners sharing one TB, that still leaves room for contamination of the incoming air charge. Seems like you would loose some of the "driveability" factor that is so great with the ITB set-up. However it may still be better than a single inlet manifold. If it is economically feasable, it would be interesting to see the results.

No doubt you are right, but the fact that each runner would feed at opposing intervals it would still be more toward the ITB than the single plane, in pricipal anyways...........I think. Economically feasible, yeah I guess it would be. Basically I would only be out raw materials and time. I figure less than $1K would cover the whole venture. The whole idea behind even wanting to do this would be to run the L-92 head. Otherwise I probably wouldnt be so hell bent on it. Its a concept I have thought about for a while, but never had the incentive to pursue.

xfactor_pitbulls
05-30-2006, 11:30 PM
Also, just by using the harrop as a guide line, (4) 50 mm would be the ticket. If that is the smaller of the two setups, then it would suffice for what I am doing. Basically it would only feed one cylinder at a time per TB, so therefore would only require about the same amount of air as an equally sized ITB. Pretty sure there is more to it than that though. The added plenum volume would have some effect on the air efficientcy I would think. It just hard to even guess at how much. The smart thing to do in this situation would be to start where the harrop is or just a tad above and go from there. Make the TB mounting plates just big enough to allow for an additional growth of maybe 10mm. That should cover any needed additional capacity.

Brandon

FieroZ34
05-30-2006, 11:54 PM
I think this has already been figured out, but if not, hope this helps.

Most ITB setups have a vacuum line from each throttle bore, after the throttle plate. Then you would run each line to a common vacuum accumulator, just a box that sits near the throttle bodies. From here, you can plug in your brake booster line, MAP sensor, PCV, and any other vacuum source. If you have access to the machining tools neccesary, this is where you want/need your IAC. You'd plug it into the vacuum accumulator on the post-IAC passage, and get it's feed/inlet from after the air filter and before the throttle plate. It's hard to explain. One other way to do it is run a pipe from after the air filter, but before the throttle blade, to the accumulator. Inline somewhere in this tube you'd place the IAC. But you'd need to machine the pipe at this point so that it not only accepts the IAC, bolted on with no leaks, but that the spindle/plunger seals onto a recieiving conical piece. Hard to fab...I've been looking EXTENSIVELY for some remote mount IAC valves, that you just plug in a rubber 5/8" line or whatnot on both sides, but havn't found crap. I did find one that has an internal plunger, and it can mount flat, but making the flanges and dividers would be just as much of a pain in the a$$. Let me know if you find one...

Another option is to not use an IAC, and just use the blades as idle adjusters. They should have an idle screw on them. And if you bought ITBs in the first place, idle quality is a secondary concern. But I understand, if you have EFI, one of the major advantages is great idle, even with ITBs.

As for the TPS. This has a lot to do with tuning, but generally, you just use a standard GM 3-pin TPS on a single throttle body. Most aftermarket ITBs have a mating surface for a GM TPS. Mine do, pics below, courtesy of my checking account and TWM Induction (www.twminduction.com). Let it be known, your factory EFI will probably not be very accepting. The LS1 EFI uses a MAF input for airflow. MAF + ITBs = bad. The alternating "gulps" from the ITBs will play fun games as your MAF tries to figure out wtf is going on. Generally speaking, a AlphaN or MAP based EFI system is preferred. AplhaN is out of the equation on the street. Thus a MAP based system is preferred, one that can be tuned. This sucks, because most MAP based ECUs, both stock and aftermarket, are also MPFI and not SFI. The LS1 SFI is more efficient and smoother, better tq and MPG, at lower RPM. But past ~3000rpm it goes to batch fire anyways. So your Camshaft Position Sensor is useless, as is your extra Crank Position Sensor.

Done rambling, here are some pics of the 48mm TWM throttle bodies that will go on my 3.4l DOHC V6 Fiero if I ever get off my a** and do it.

http://img.photobucket.com/albums/v336/AaronZ34/DOHC%20V6/Enginemockup003.jpg
http://img.photobucket.com/albums/v336/AaronZ34/DOHC%20V6/Enginemockup008.jpg

xfactor_pitbulls
05-31-2006, 12:32 AM
Very good post and I am about to go to bed, but real quick. The system will not use a MAF (speed density setup). It will maintain a stock MAP sensor though, I dont figure it to be a problem with my simple design and a double wall that goes front to back. You can also use the back side of the intake to handle all vaccum related accessories since it would have limited common airspace through out the plenum. I guess this kinda dances back and forth between a single plane and ITB. I think I will make two manifolds, one traditional forward mount with a single TB and the one we have been speaking of. It would be alot easier to build two at once, rather that at different times.

Brandon

GIGAPUNK
05-31-2006, 12:40 AM
I forgot where I stole this from but here ya go:

I had been thinking about building a itb system using motorcycle itbs. After quite a bit of digging, I found out that the Suzuki GSXR 1300 aka Hayabusa, and Kawasaki ZX12R have the biggest that are available for an inline 4, both measuring 46mm. They are on a smaller bore center of course. On ebay they usually go for close to $200, and we'd need two of em + a lot of creativity.

Basic references for BHP per cylinder, assuming ca.(ca.= approximately) 120mm from butterfly to valve head and a max of 9,000 rpm are:

Up to 30 BHP/CYLINDER - 30mm
up to 33 BHP/CYLINDER - 32mm
up to 39 BHP/CYLINDER - 35mm
up to 46 BHP/CYLINDER - 38mm
up to 51 BHP/CYLINDER - 40mm
up to 56 BHP/CYLINDER - 42mm *8 CYL = 448 + 10% = 493 HP
Up to 65 BHP/CYLINDER - 45mm *8 CYL = 520 + 10% = 572 HP
up to 74 BHP/CYLINDER - 48mm *8 CYL = 592 + 10% = 651 HP
up to 80 BHP/CYLINDER - 50mm
up to 87 BHP/CYLINDER - 52mm
up to 93 BHP/CYLINDER - 54mm.

These power figures may be increased by up to 10% in a purpose - designed, well proportioned system.

As butterfly to valve distance increases, butterfly size will need to increase in proportion to system taper and vice versa.



And here's my motorcycle research:

Motorcycle ITBs:

Kawasaki
Z750S 34
’06 Vulcan 2000’s twin 46
’02 ZX12R 46 bore spacing 85.4 mm/2=42.7, (111.76/2=55.88)
’06 ZX-14 44
’04-‘06 ZX10R 43


Yamaha
’04 R6 38
’05 R6 40
’03 R1 40
’04-‘06 R1 45

HONDA
CBR954RR ’02-’03 up to 42 from 41
CBR1000RR ’04-‘06 44
CBR1100XX 42

Suzuki
’03 GSXR 1000 (42) 50mm@ airbox side to 42mm @intake-manifold side.
’99-‘06 Hayabusa 46 81mm bore =3.2”

94-99 neons had 49mm

Jdm Toyota AE111 Levin 20v MAP 44mm ITB's funky shape at outlet though.

Beast96Z
05-31-2006, 07:08 PM
The obvious thing here is that you'll have to pair the cylinders that fire oppisite of each other so 2 cylinders aren't feeding from the same TB at the same time. Once you figure the order, you'll have to find a way to pair these runners and still have room to fit it under the hood. You still face the problem of incoming air contamination with the cylinders paired, but I doubt it would be as bad as the single inlet.

xfactor_pitbulls
05-31-2006, 07:59 PM
The obvious thing here is that you'll have to pair the cylinders that fire oppisite of each other so 2 cylinders aren't feeding from the same TB at the same time. Once you figure the order, you'll have to find a way to pair these runners and still have room to fit it under the hood. You still face the problem of incoming air contamination with the cylinders paired, but I doubt it would be as bad as the single inlet.

With using the pairing I said, right rear, right front, left rear, left front.......it would have the obvious 2 position gap between firing. Thats the best I can do with this setup, should be enough. Thinking about doing everything ovalular to help with height issues and already sketched up the general top shape and mounting positions. Stock LT1 TBs or something alittle smaller might be just the ticket. I think they use the same TPS too. Is there another gm late model car that uses a small oval TB? You know what.........that is it. You could run the IAC in tandom (piggy back) and route all back to the stock connection. If that was done, and tps was controlled on a single tb, you could run a hardline like stated before that would connect behind each tb plate and back to a central block to control vaccum accessories. This would alleviate any sharing of air space (aside from partnering cylinders I mean). Just brain storming again. There are about 10 different ways to go about this deal.

Beast96Z
05-31-2006, 10:22 PM
I couldn't Imagine 4 LT-1 Tb's under a f-body hood. Depending on what size your looking to use, the Motorcycle TB's may be more sleek and easier to work with.

njn63
05-31-2006, 10:29 PM
not sure how much this will help you, but there have been more than a couple people who have made their own individual throttle bodies for Hondas.
http://www.tuner-junction.com/TJForum/showthread.php?t=144
http://www.homemadeturbo.com/tech_projects/itb/

That's 2 really good writeups.

chuntington101
06-01-2006, 06:39 AM
there is a bit of a craze starting over here (and i can see why) for using moptorbike carbs or throtle bodies on 4 cyclinder engines upto about 2.5ltr. the bodies seam to handle the flow no problem and four can diliver over 250bhp i think!

now on a BIG engine you are goiong to start running into the flow limits of the boddies very quickly! if i wehre doing it and wanted to use bike TBs id go for three banks of four (giving 12 TBs in total)! this way you will def not run out of flow through the bodeis anyway!

Thansk Chris.

xfactor_pitbulls
06-01-2006, 07:36 AM
there is a bit of a craze starting over here (and i can see why) for using moptorbike carbs or throtle bodies on 4 cyclinder engines upto about 2.5ltr. the bodies seam to handle the flow no problem and four can diliver over 250bhp i think!

now on a BIG engine you are goiong to start running into the flow limits of the boddies very quickly! if i wehre doing it and wanted to use bike TBs id go for three banks of four (giving 12 TBs in total)! this way you will def not run out of flow through the bodeis anyway!

Thansk Chris.

That is too many for my taste. 4 is hard enough to link together, X 3 and you add even more problems. Think I will stick with 4 total, just need to figure out if there is another gm based car that would have tbs that make sense, and i bet there is.

Brandon

J-Rod
06-01-2006, 11:12 AM
Ok, a couple of things. My buddies in Australia built ITB intakes before Harrop came out with the production model.

You can buy TB's from Accufab and others.

30MM is far to small. For an 8 runner ITB setup on an ls1 a small TB is 48MM, a medium is 50-52, and a LARGE is 55.

You ditch the MAF and convert to SD.

All the TB's are synchronized, so you only need on TPS input. So, you mount one TPS. Its probably easiest to reference off the linkage, or one TB.

As for an IAC. You can tune to not need one. If you really want one, work from the factory unit. Create a distribution block, and feed it from the ITBs. But I think you can get by without needing one

MAP - A must. You need to have a small hose coming from each TB, and feed a distribution block with your MAP sensor installed.

8TB setup
http://users3.ev1.net/~black_ops/AUS/dsc00025.jpg
http://users3.ev1.net/~black_ops/AUS/dsc00027.jpg
http://users3.ev1.net/~black_ops/AUS/dsc00028.jpg
http://users3.ev1.net/~black_ops/AUS/dsc00037.jpg



4ITB intake.
http://www.ls1tech.com/forums/showthread.php?t=481985

chuntington101
06-01-2006, 12:04 PM
J-Rod, who builds the 8 TB set up?? any idea on cost??

thanks CHris.

xfactor_pitbulls
06-01-2006, 01:39 PM
Ok, a couple of things. My buddies in Australia built ITB intakes before Harrop came out with the production model.

You can buy TB's from Accufab and others.

30MM is far to small. For an 8 runner ITB setup on an ls1 a small TB is 48MM, a medium is 50-52, and a LARGE is 55.

You ditch the MAF and convert to SD.

All the TB's are synchronized, so you only need on TPS input. So, you mount one TPS. Its probably easiest to reference off the linkage, or one TB.

As for an IAC. You can tune to not need one. If you really want one, work from the factory unit. Create a distribution block, and feed it from the ITBs. But I think you can get by without needing one

MAP - A must. You need to have a small hose coming from each TB, and feed a distribution block with your MAP sensor installed.

8TB setup
http://users3.ev1.net/~black_ops/AUS/dsc00025.jpg
http://users3.ev1.net/~black_ops/AUS/dsc00027.jpg
http://users3.ev1.net/~black_ops/AUS/dsc00028.jpg
http://users3.ev1.net/~black_ops/AUS/dsc00037.jpg



4ITB intake.
http://www.ls1tech.com/forums/showthread.php?t=481985

I realize that you can buy the TBs anywhere, but just wanted to retain the GM IAC. Didnt realize you could do without the IAC.........thats good to know. Obviously the MAF was going to go anyways. I hear you about the MAP that was my most recent thought as well. I appreciate the input guys, this is the kinda thread that really helps people. Gonna start looking for TBs now, the easy one if the circle, I really think an oval would work better for what I thinking.

Brandon

MrDude_1
06-01-2006, 02:02 PM
I realize that you can buy the TBs anywhere, but just wanted to retain the GM IAC. Didnt realize you could do without the IAC.........thats good to know. Obviously the MAF was going to go anyways. I hear you about the MAP that was my most recent thought as well. I appreciate the input guys, this is the kinda thread that really helps people. Gonna start looking for TBs now, the easy one if the circle, I really think an oval would work better for what I thinking.

Brandon

since you ahve to tie in all the runners together for the MAP, i dont think its a big streach to connect the IAC to that "tied in" point..

xfactor_pitbulls
06-01-2006, 02:05 PM
Its alittle more complicated than just running a vaccum feed. I am all about simplicity, especially for the first go round. Obviously I could modify as well after it is done.

Brandon

FieroZ34
06-04-2006, 12:47 AM
I realize that you can buy the TBs anywhere, but just wanted to retain the GM IAC. Didnt realize you could do without the IAC.........thats good to know. Obviously the MAF was going to go anyways. I hear you about the MAP that was my most recent thought as well. I appreciate the input guys, this is the kinda thread that really helps people. Gonna start looking for TBs now, the easy one if the circle, I really think an oval would work better for what I thinking.

Brandon

Don't take this the wrong way, but did you read my post? I explained the idle thing. You can run it with no IAC, but I wouldn't suggest it, especially when it wouldn't be difficult to incorporate.

Also, it really isn't more complicated than running a vacuum feed from each TB, so long as the IAC lets air into the vacuum accumulator.

Idea: The LS1's IAC is incorporated into the TB. Now what if you cut off the rest of the TB, only leaving the IAC part, the inlet, the port, then the outlet. Then just weld, JB weld, or anything a pipe on each end? Stock IAC, stock wiring, etc. A cheap, easy to fab, accurate, reliable IAC valve. I may just do this on some cheapa** TB from like a GM 3.1 or something. Most GMs use the same inline 4 pin IAC connector, and runthe same IAC voltage, so you can use almost any model IAC too.

zuluman13
06-07-2006, 08:48 PM
I am planning on building an itb for the motor im building. I have most of everything figured out except i havent figured out the best way to transition the round throttle body into the cathedral intake port style of the ls1 head the only thing that i could think of is a plate about an 1-1.5 inches thick and blending it. Does anyone have any ideas for this.

FieroZ34
06-07-2006, 08:53 PM
I am planning on building an itb for the motor im building. I have most of everything figured out except i havent figured out the best way to transition the round throttle body into the cathedral intake port style of the ls1 head the only thing that i could think of is a plate about an 1-1.5 inches thick and blending it. Does anyone have any ideas for this.

I'm in the same boat, just not as bad, I have to go from my circular throttle bodies to a rectangular intake port. Still havn't decided how I'm going to do that one...

cueball
06-12-2006, 01:24 AM
I plan on fabbing up either an adaptation of an existing intake with a segmented plenum and 4 TBs or building a sheetmetal with 4 from scratch. If I didnt go that route, I already decided to use a single 105mm accufab with a single plane intake. My thoughts are to use 4 30mm tbs in place of the 105, but it that logical? Please dont try and diswade my thoughts on the initial sizing, it works and that is my starting point. Is there anyway to use the stock pcm to control multiple throttle bodies? How about adapting a TPS to work with the smaller ITBs? The electrical system on LSX setups is my weakest subject, so just playing around with ideas. What are the guys doing to run the accufab 105mm ford, I mean from the TPS aspect? Iam sure many of you guys have had the same ideas as I am having.

Brandon



You could just use an older style tbi IAC that physically moves the throttle blade to control idle.
hope that helps. :)

MrDude_1
06-12-2006, 08:10 AM
You could just use an older style tbi IAC that physically moves the throttle blade to control idle.
hope that helps. :)


what TBI is this?

every GM TBI ive seen uses a standard IAC like all of the other cable operated throttlebodys have had..