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PostPosted: January 18, 2017, 10:13 pm 
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Joined: January 5, 2010, 12:13 pm
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Location: Little Rock, AR
I was on the site looking for other information, and after looking around, thought a project that I did a few years ago may be of benefit to those that want a unique LS fuel injection option that would be more affordable than the typical aftermarket offerings. My goal was an 8-stack EFI that would fit on my LS2 mid-engine project, but be low cost. Seeing $4k and above for most set-ups, I set out to fabricate my own, but without the benefit of a machine shop. All I had was a heavy-duty drill press, and lots of hand tools.
What I ended up with was this:

Image

Major parts used were;
1) A cut up and re-welded Idelbrock Pro-Flow intake manifold.
2) 8 Chrysler LHS 3.5L throttle bodies (they are Holley 48mm bodies with one vacuum port, and a throttle shaft...very simple) from the salvage yard.
3) Various pieces of plate aluminum for mounting plates and adapter plates.
4) Hardware bits and pieces from McMaster Carr.

In the end I had about $800 in the actual intake system, and then additional money for the fuel management and aluminum ram-tubes. A photo sequence of the work, and captions explaining the photo are located at:

http://toxandale.fototime.com/Manta%20ITBs

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Last edited by blueovalz on January 19, 2017, 12:23 pm, edited 2 times in total.

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PostPosted: January 18, 2017, 11:02 pm 
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Very interesting. How does it perform?


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PostPosted: January 18, 2017, 11:11 pm 
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kreb wrote:
Very interesting. How does it perform?

This. A back-to-back comparison to the OEM LS3 intake manifold and throttle body would be very informative.

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PostPosted: January 18, 2017, 11:26 pm 
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I love it! :cheers:

In my opinion: As long as it's not massively down on power, if it provides the right look, feel, and sound to go with the car, then it serves its purpose...And if it does happen to offer some gains, all the better.

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PostPosted: January 19, 2017, 9:10 am 
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Joined: February 8, 2014, 10:47 pm
Posts: 781
Location: Cornelius OR
Too many detractors on ITBs.

Synchronization
Idle quality
Idle control
Throttle response
Power loss

The biggest being power loss due to the disturbance of airflow by the butterfly.
The science behind induction systems is to accelerate the air smoothly from the entrance of the tract to the valve.
Air should be admitted at a larger diameter and steered towards it's destination smoothly,
on it's way it should be gently squeezed and accelerated so a column of air is rammed into the cylinder.
Given this the cross sectional volume of a runner should be gradually reduced without any variation that might take away the energy of the mass of moving air in the column.
A butterfly valve placed at the bottom of the column disrupts this flow and dramatically reduces air speed.
During my time helping with the R&D on a patented 2 roller air valve, I have seen on a flow bench as much as a 20% loss in flow caused by a butterfly valve.
This results in the need for oversized runners and TBs to make up for the flow loss,
however velocity is permanently lost and velocity is the key to ramming in more air than the piston can suck.

The rest of the issues with ITB's make tuning and driving difficult.
It is very difficult to modulate ITBs, they feel like more of an On Off switch.
A consistent idle speed is next to impossible to maintain.
With that Idle AFRs will be all over the place.

I could go on but the first point is easily proven on a flow bench or Dyno and results in a thumbs down for the ITB.
If this was a good idea it would be found on most all production motors.

Many equate ITBs "performance" due to ITBs almost uncontrollable tip in.
Their butt dyno pegs from the hit and they are so impressed they completely miss the missing power part.
The inrush flow on a butterfly valve is huge and when you have 4 6 or 8 of them (usually oversized to make up for flow loss)
the inrush is so big you are at 1/2 total airflow at 1/8 butterfly rotation.
This is the same effect as installing a Super E Carb on an Ironhead, the carb is way too big and by the time your arms snap back into their sockets
you don't realize that from 3/4 to full throttle there is no difference in power.
But your butt dyno is happy even though Im going to beat you in a race with a tiny 38mm round slide carb.

But for eye candy there is nothing better!

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Last edited by Bent Wrench on January 19, 2017, 10:10 am, edited 3 times in total.

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PostPosted: January 19, 2017, 9:45 am 
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Terry
Thanks for sharing. You differntly have one hell of a project going there.
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PostPosted: January 19, 2017, 10:24 am 
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Location: Little Rock, AR
Bent Wrench wrote:
Too many detractors on ITBs.

Synchronization
Idle quality
Idle control
Throttle response
Power loss


Sychronization - is very good here, but it took some work for that. I'm not sure slight differences in castings of intake manifolds or a/f distribution would be any better in a non-ITB set-up.

Idle quality - as good as any OEM intake or program. The fuel management system has more to do with this than the ITBs do. Current day fuel management systems offer a large variety of inputs. Idle quality and control are as good as the OEM idle once this is figured out. Self learning systems are great.

Idle control - I have nothing on the motor that is on/off, so no IAC. Idle control is RPM/temperature/pressure/TP based.

Throttle response - is excellent. I specifically designed it for maximum progressiveness on the throttle wheel. Again, it has an OEM responsiveness and feel.

Power loss - a purposefully designed system with tuned runners and injectors well separated from the throttle plates provides excellent VE.

My guess is that these "detractors" are based on systems from 20 years ago, under-developed electronic or simple mechanical ITBs, poor understanding of how they work and hence poor application, and based on power at an application not associated with any street use. I'm also inclined to believe ITBs are not used on OEM high performance cars for the reason of cost, packaging, and complexity, than performance or anything that fuel mapping can't overcome. Considering the nature of this project, the OEM intake was a no-go. I have not observed the "detractors" noted above, and have good reason to believe I've lost nothing with this set-up except for the occasional maintenance, set-up time, and under-hood clearance (not applicable), but it's not a daily driver either.

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Last edited by blueovalz on January 19, 2017, 12:25 pm, edited 1 time in total.

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PostPosted: January 19, 2017, 11:34 am 
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I'd say you've done a pretty impressive job of coming up with a low cost solution. I love the "CanAm" look to the system too. I'd love to see a video with sound of your engine running.

Congratulations!

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PostPosted: January 19, 2017, 4:04 pm 
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I think the subject of modifying intake manifolds to make things we want is well worth exploring. I'd be happy with a single throttle, but I sure would like to see lower profile manifolds for our little cars. Especially for Ford 302...

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PostPosted: January 20, 2017, 4:05 am 
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Joined: November 11, 2013, 4:47 am
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Just sold my Edelbrock SBC Pro Flo FI setup.
Currently working on adapters for ITB's to varied Weber intakes.

To respond to a post above, BMW uses ITB's on some models.
in fact I may be using BMW ITB's for some of my conversions as they are simple to work out linkage for.

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PostPosted: January 21, 2017, 3:50 pm 
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Bent Wrench wrote:
Too many detractors on ITBs.

If this was a good idea it would be found on most all production motors.



It certainly is in motorcycles. The throttle response on my ZX6R is incredible, and the power is very easily modulated. It's hard to argue with an engine producing over 200hp/L naturally aspirated.


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PostPosted: April 18, 2024, 1:40 am 
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Location: Little Rock, AR
I know it's been a long time, but noticed I had not updated this site for my project. The home-made ITB set-up works great. Uses the Holley EFI self learn management, and I utilize speed density metering (not Alpha-N as so many said I should). I got it close as possible without a dyno, and then had the dyno guys finish it up. Result was (at the wheels) 480 HP/517 ft/lbs out of the the stage II cammed 6.0L. Throttle response was great for street driving, and start-up and idle quality very good. So yes, ITBs work really well on the track or the street (or both), and Alpha-N is not the only option for doing this.

So...with that said, I bumped the rev limiter to 7K due to the track configuration (and a pesky GT2RS that I was trying to outrun), blew the motor after 30 laps, and am starting all over again with a new, and different motor configuration. New motor is an LS3 this time (building it as of this posting). The new motor be slightly larger (6.3L), and with the rectangular port heads, which means an new intake manifold. Before going into that project, let me say that I believe I could reasonably use the ITC billet adapter plates (LS2 intake for LS3 heads), and yes it would be a little wonky on the runners, BUT, it appears to be a better configuration than the more common LS3 intake for LS2 heads. It's not as bad as one would think.

Anyway, on to what I'm doing now. For the ITBs, I purchased (because it was relatively dirt cheap) a Walmart offered LS3 55mm ITB kit that was $260. Basically it was an OBX product, using 52mm ITBs (fairly decent), but nothing else of much use (intake runners where what I would call ridiculously small, and the hardware kit was a puzzle (NO instructions or paperwork), so all that I used was the ITBs. But even with that, the price for 8 ITBs was pretty good. Anyway, the manifold was the cheap Chinese copy of the Holley Hi-Ram (I could have gotten just the Holley base of their Hi-Ram for close to the same price, so that was a lesson learned). Yes, it has it's issues with quality, but this project is to see what can be done on the cheap. This Amazon offering was cut up into pieces on the table saw in the same fashion the Edelbrock intake was cut up for the LS1 heads (cathedral port), so exact same process. After some welding and burring, I've got and intake sized for the 52mm ITB. The OEM configuration for these ITBs would probably have worked fine, BUT, I NEVER had an issue with the way I set up the ITBs on the orginal project (shaft couplers from McMaster-Carr), so I duplicated that effort with the OBX ITBs. This entailed a lot of work because I had to extend the shafts just so the couplers could be utilized. Yeah...lots of work on that, but again, this is a study in making the most out of the least, with all the time in the world to do it (am retired). There are a few ITBs out there with longer shafts, but over $1K just for bare ITBs (Linkage kits for them are also $$$).


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PostPosted: April 18, 2024, 9:14 am 
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What was the failure mode of the previous engine?

The hard question is determining whether airflow is uniform to all cylinders. A tell-tail sign will be spark plug color, but AFR to each cylinder really needs to be confirmed to do it right. Without going to the extreme of having 8 AFR meters, one could be used and moved to the next cylinder between dyno pulls.

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PostPosted: April 18, 2024, 12:13 pm 
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KB58 wrote:
The hard question is determining whether airflow is uniform to all cylinders. A tell-tail sign will be spark plug color, but AFR to each cylinder really needs to be confirmed to do it right. Without going to the extreme of having 8 AFR meters, one could be used and moved to the next cylinder between dyno pulls.
Without complicating things too much, a common vacuum log can be plumbed between the 8 runners to help balance airflow. Can be done pretty much out of sight so won't impact aesthetics.

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PostPosted: April 19, 2024, 11:20 am 
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An air synchronizer could be used as well, no?

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