Worth doing ITB + turbo?
 

I have a set of 4AGE ITBs + manifold and stacks from when I was going to go built N/A... I just bought a GT2554R turbo (I know, small, but I wanted a fast spool and know I cant trust myself with a 250whp+ Miata), and have the manifolds and everything coming shortly - is it worth it fabbing up a single "collector" tube for the ITBs to use in conjunction with the turbo? Or will it just prove to be more of a hassle than it is worth, despite having the "coolness" factor? I was thinking that with the small Garrett, it might be some really great throttle response when tuned properly

More hassle than worth, unless you value cool enough to flip it the other way.

do it, and tell us if it was worth it. no one ever does....

I suppose we will see if I still have the ITBs once everything gets here and I get the turbo installed, should only be a few weeks... I was moreover wondering if the ITBs themselves will really provide any gains in terms of top end that would make it worth the hassle, or if I'd be better off going for the squaretop/skunk mani and TB for a similar end result

A bit off topic, but will the RX8 yellow injectors be enough to max out a GT2554R? I was told to just go with the Flowforce, but there is someone near me who has barns filled with rotary parts and can get me a genuine set for ~$70 so I don't want to spend five times as much if it won't get much benefit, for now

You are not including the cost of cleaning those injectors. Let alone if they will flow anywhere near each other. Injectors are not something that is worth risking even on a low budget build. Especially when we have someone who offers a fantastic product and is a great contributor to the community.

My understanding was they were good sets that are cleaned, that he had set aside for full overhauls on the wenkels - but, you are right, I'd have no cards or anything on them. The $250 difference goes a long way towards other things on the car, though

I'm with Brainey on this one. A lot of folks talk about it, but I can't recall seeing one actually finished. I doubt you'd see any gain on the dyno, and am highly skeptical about quantifiable gains in throttle response. Still, it'd look cool.

What's the plan for engine management?

I have a MS3X, but I really don't know where I would start with tuning it

What was your original plan (back when you first acquired the ITB setup) for obtaining a stable MAP or airmass signal?

The manifold has barbed nipples on each throttle body - I was going to take a steel line, and run it to a piece of tubing that was tapped for four barbs + another barb on the end, then capping the other end and welding it shut.

I also bought a TPS

This is a 1.6 engine?

BP4W

Yeah, I've stopped telling people about my cars and bikes because they look at me like I'm crazy.

New to Miata tuning - is the VICs going to give me benefit over a gutted square top in a FI application like this?

Im not sure is MS supports it but some EMS have a way of doing alpha-n blended with MAP. Its "the" way to do ITB + Boost, apparently.

MS does support that.

MS has a couple strategies like that:

• "Hybrid Alpha-N," which is what happens if you pick Alpha-N while leaving the default setting of "Multiply MAP" on. This uses TPS as a load axis but incorporates MAP into the fueling calc. The TPS-indexed table entries are VE, and the VE value gets multiplied by the (usually cycle-averaged) MAP value.

• ITB mode uses a calculated load value for the VE tables that is a nonlinear function of both MAP and TPS, which is influenced by MAP more at low loads and less at high loads. This is meant for better drivability on N/A ITBs, and most normal strategies for this mode would not work for boost, since it actually phases out the influence of boost on the load axis as you hit higher rows.

Not worth it. Not first hand, but second hand experience. A buddy of mine did it on his car and he spent a lot of time fine tuning everything just to make it drivable for very little gains. Its been almost 10 years and he still complains about how hard it was to tune the throttle tip in because there are so many variables that had to be tuned to make it work. Not just ECU adjustments, but he played around a lot with vacuum chambers to get a consistant MAP reference and brake pedal (before converting to manual pedals). Based on his recommendation, for a simple car to tinker with, leave the ITBs to NA use and single throttle body for boost.

This was what I was thinking of. No personal experience but I talked with a tuner a while back who was tuning my buddies Evo using this strategy with AEM Infinity. The "fuel" map was very flat and weird looking because it was being scaled with MAP in another table.

Gotcha. I was a little mixed up when you said you'd purchased a TPS; usually that's something that B6 people say (since the 1.6 engines didn't have a "real" TPS), but I forgot about ITB.



MS does support Alpha-N, but it gets hairy when you add forced induction to the mix. At that point, you're better off running straight MAP, which is its own can of worms with an ITB setup. (You need to construct a plenum chamber for the MAP signals themselves, which the OP has apparently already considered.)