Anyone running an ITB set up on an LS3?

[FLYNAVY53]

Just curious....looking at options for my '64 Corvette. I've been emailing back and forth with Jim Inglese and it sounds like the most up to date versions of his ITB manifolds for the LS motors are using all factory GM sensors and can be run using the Holley Terminator X. I know back 8-10 years ago, there were big issues with getting all 8 throttle bodies to work in unison, but it sounds like a lot of that has been fixed in the newer offerings.



Any input would be appreciated!

[parsonsj]

I'm running Jenvey ITBs on my Radical SR8. Dual DBW servos, custom linkage, ID1050 injectors, etc. But I'm using a MoTeC M150 ECU, not a Holley.

I found that the notion of trying to run a speed density tune via MAP using vacuum lines from each ITB to a common plenum didn't work very well. Last year, MoTeC actually came up with a different method in their firmware to accommodate ITBs and it works really well. It's an alpha-N (throttle position-based load) strategy.

[FLYNAVY53]

Thanks for the response John. My set up would be significantly less radical...I'm looking at the GMPP LS3 long block, then swapping the stock cam for a Cam Motion low lash solid roller set up and an ITB manifold. My car is a small tire street car, so I'm not looking for huge power or torque....more the high revs and snappy throttle response of the factory L76 solid lifter 327.

You bring up an interesting point about the MAP sensor....the pic below is of the current offering from Jim Inglese...I need to shoot him another email, but it almost looks like there is a "log" cast into the manifold itself as you can clearly see the MAP sensor and IAC in the front of the intake.

[parsonsj]

That photo does show a MAP and an IAC. I wonder if that means it is set up for cable throttle? LS3s are DBW, though I suppose the Holley can do whatever you want.

And what the heck is that breather?

Also, what are your plans for PCV? Are you running a dry sump?

[parsonsj]

Also: ask about the throttle balancing procedure, and if you need to buy a set of synchrometers for that.

[dontlifttoshift]

The breather is the intake for the IAC. As far as I know all of these are cable operated and that is the problem, they take a pretty heavy foot or a lot of travel in the pedal. We have printed cams for the bell crank in the center to soften up the throttle from idle to halfway.



You definitely need to sync all the throttles. It's a tedious process but well worth the effort. I've done them with an old unisyn but the one that Borla sells works far better.

[FLYNAVY53]

Again, this is all in the planning/feasibility stage. If I were to go this route, I would go cable throttle with the Terminator X....I actually much prefer a cable throttle to the drive by wire set up. I like the increased resistance as you get deeper into the gas. Jim does not advertise a DBW option for his intakes.

I am running wet sump, and as far as PCV goes, my initial thought was to run breathers on the valve covers for the clean air side, and run the stock LS3 valley pan/ PCV vent to a vacuum pump that I would mount on the accessory drive in place of the A/C compressor to evacuate the crank case as I'm not running A/C on this car.

I'll have to inquire about the sync process....he alluded to the fact that everything he builds is test run prior to shipping in order to ensure its ready to install right out of the box. I understand they process, but dont know enough to evaluated whether you can synchronize the throttle bodies on one motor, then swap the intake to a different motor and still have they in sync.

[parsonsj]

Since you're still just planning, this setup looks like one of the best I've seen. I know you said you like cable throttles, but that along with an IAC makes for difficult idle tuning. This AT Power kit seems like a tuner's delight -- one that you'll really be able to dial in.

https://www.atpower.com/products/che...hrottle-bodies

Vacuum pump for fresh air crankcase evacuation sounds good, but are you sure about no A/C? I just think that's a required part of a street car. I will admit to being 61, so maybe the kids go without A/C these days, lol.

[FLYNAVY53]

That does look interesting....I'm curious what ECU they're using and how user friendly it is when it comes to tuning. I'm not opposed to DBW, I just prefer the cable drive if given the option....or the lack of DBW is not necessarily a negative for me.

When I LS swapped my '72 Suburban, I did the Vintage Air thing, and honestly, I dont use it that often. Its extremely loud with the fan at max, and its still only enough to barely cool the front seats in the summer. Admittedly that's largely due to the volume of glass and old seals in that truck. I'm generally comfortable with the windows down up to the low 90s, and anything over that, I'm probably going to take my 4runner daily driver anyway. The Corvette doesn't have A/C now, so I had no real plans to add it. The compressor location just seemed like a logical place to add a vacuum pump if one was require (as in the ITB application).

[FLYNAVY53]

I found that the notion of trying to run a speed density tune via MAP using vacuum lines from each ITB to a common plenum didn't work very well. Last year, MoTeC actually came up with a different method in their firmware to accommodate ITBs and it works really well. It's an alpha-N (throttle position-based load) strategy.

Do you know if the Holley Dominator can accommodate an alpha-N strategy?

[FLYNAVY53]

Answered my own question....

https://www.youtube.com/watch?v=-a94kzQ1XqU

Looks like the Dominator can accommodate alpha-N, or a combo strategy that uses alpha-N at idle and low engine speed and switches to speed density.

So if you eliminate the need for the MAP sensor and IAC in an ITB scenario, what other sensors do you need on the intake?....Just Inlet Air Temp and Throttle Position?

[parsonsj]

Right: inlet air temp, throttle position, and either airbox pressure (if you've got some sort of ram air intake) or ambient pressure. RPM as well, but that's not an "intake" sensor. You'll need dual widebands too on the exhaust.

[FLYNAVY53]

So in your experience, would you go with the Jenvy set up again, or the AT Power? Aesthetically, I like the Jenvy side draft set up as it most closely replicates the look of the 1963 Grand Sport Corvette motor which is the inspiration for this little project.



That being said, priority number one is a system that will function the best, so Im not opposed to the vertical down draft style of the AT Power set up.

[parsonsj]

It's interesting that you ask about Jenvey vs AT Power. I'm installing a new engine in the Radical, and am working through the packaging to swap my existing Jenveys to an AT Power setup. My issue with Jenvey is the throttle linkage. They use a set screw / linkage arm for each TB to the next. It's very flexible, but needs lots of care to stay in balance. In contrast, AT Power uses a central linkage shaft to bind the butterflies together, which seems more robust and easier to keep in sync.

In working with the two companies, Jenvey seems a bit more "good luck with your setup" whereas AT Power is more interested in working to help solve them.

[andrewb70]

My words of advice is to tread lightly...The ITBs can work well, but they bring up a can of worms for tuning. Alpha-N works great for cars like JPs Radical race car, but it isn't optimal for street driving. All Holley EFI systems have Alpha-N and also Combo, which combine Alpha-N and speed density.

At the end of the day, a stock LS3 intake and 90mm throttle body is hard to beat for overall performance, and excellent drivability.

Andrew

[FLYNAVY53]

It's interesting that you ask about Jenvey vs AT Power. I'm installing a new engine in the Radical, and am working through the packaging to swap my existing Jenveys to an AT Power setup. My issue with Jenvey is the throttle linkage. They use a set screw / linkage arm for each TB to the next. It's very flexible, but needs lots of care to stay in balance. In contrast, AT Power uses a central linkage shaft to bind the butterflies together, which seems more robust and easier to keep in sync.

In working with the two companies, Jenvey seems a bit more "good luck with your setup" whereas AT Power is more interested in working to help solve them.

Good to know....I appreciate all of the first hand info.

[FLYNAVY53]

My words of advice is to tread lightly...The ITBs can work well, but they bring up a can of worms for tuning. Alpha-N works great for cars like JPs Radical race car, but it isn't optimal for street driving. All Holley EFI systems have Alpha-N and also Combo, which combine Alpha-N and speed density.

At the end of the day, a stock LS3 intake and 90mm throttle body is hard to beat for overall performance, and excellent drivability.

Andrew

Thanks Andrew, I was hoping you'd find your way into this thread. Completely understood that the stock LS3 intake/TB combo is about as good as youre going to do on the stock crate motor for a street car.

That being said, there is some part of this project that is aesthetic and driving characteristic over all out performance. The limit is really going to be the 225 tires at all 4 corners. What are the shortcomings of any ITB set up on a stock LS3 with regard to tuneability/driveability?

Thanks for the help!!

[andrewb70]

Thanks Andrew, I was hoping you'd find your way into this thread. Completely understood that the stock LS3 intake/TB combo is about as good as youre going to do on the stock crate motor for a street car.

That being said, there is some part of this project that is aesthetic and driving characteristic over all out performance. The limit is really going to be the 225 tires at all 4 corners. What are the shortcomings of any ITB set up on a stock LS3 with regard to tuneability/driveability?

Thanks for the help!!

If the system is not well made, you'll have so much air leaking past the throttle blades that you won't be able to achieve any reasonable idle speed. This was an issue with one of my customers and he is currently swapping to a stock LS3 intake and DBW.

Cam selection is also critical. You want no less than 50-55kPa at idle. The short intake runners also don't do anything good for low to mid-range torque.

I don't know what the Inglese system costs, but a mild cam with a super charger would be money much better spent.

Andrew

[FLYNAVY53]

If the system is not well made, you'll have so much air leaking past the throttle blades that you won't be able to achieve any reasonable idle speed. This was an issue with one of my customers and he is currently swapping to a stock LS3 intake and DBW.

Cam selection is also critical. You want no less than 50-55kPa at idle. The short intake runners also don't do anything good for low to mid-range torque.

I don't know what the Inglese system costs, but a mild cam with a super charger would be money much better spent.

Andrew

I think the Inglese system comes in right around 5K. Honestly the smart money is probably the stock intake and TB with a '63 fuel injected radiator core support (with the offset hole already incorporated) with the intake run outside the engine bay for cold air...

[andrewb70]

I think the Inglese system comes in right around 5K. Honestly the smart money is probably the stock intake and TB with a '63 fuel injected radiator core support (with the offset hole already incorporated) with the intake run outside the engine bay for cold air...

It would be hard to beat that combination for performance and drivability.

You could definitely make the engine look better with Holley valve covers and a neat harness installation.

That square radiator is also begging for a brushless c7 Corvette fan.

Andrew