I always wanted to put 3 Chevy TPI 48mm throttle bodies on my 3 liter Volvo 6 cylinder fuel injected B30 engine. 
But now just dream of stuffing 2 Mitsubishi td03 turbos in the trunk, each run off of 3 cylinders through dual exhaust. Maybe td04's?
I always wanted to put 3 Chevy TPI 48mm throttle bodies on my 3 liter Volvo 6 cylinder fuel injected B30 engine. But now just dream of stuffing 2 Mitsubishi td03 turbos in the trunk, each run off of 3 cylinders through dual exhaust. Maybe td04's?
DarkMonohue said:Pete. (l33t FS) said:How big are the cams?
The ITB-ified bridge ported 13B in my "fun" car has low load/part throttle drivability like a stock engine. Way way better than similar engines I have had using OE type manifolds or godawful plenum manifolds that I thought were a good idea at the time.
Not enormous. They're 226° @ .050" (Web 577). Peak power comes in around 7000 RPM, though I am starting to wonder if it's not valvespring limited. Drivability with a stock plenum style manifold is acceptable, but not inspiring. Would be better with more time tuning the MS.
The real key will come up with a tight lobe separation. You would be able to advance the intake and/or retard the exhaust to bring midrange torque up with little loss in low speed drivability.
The top end would drop, but you have to go through the midrange to get to the top end...
Pete. (l33t FS) said:The real key will come up with a tight lobe separation. You would be able to advance the intake and/or retard the exhaust to bring midrange torque up with little loss in low speed drivability.
The top end would drop, but you have to go through the midrange to get to the top end...
LSA is probably pretty tight. Many, many years ago, before I went to MegaSquirt and was still messing around with cam timing, I set the cam timing up to give as much area under the curve as it would give. I used Streetdyno back then to measure acceleration (by way of ignition waveform) and approximate a dyno run. Not glamorous, but entirely repeatable. Based on comparison with a bone stock example, this should be roughly comparable to Dynojet numbers.
The point is that this engine makes a pretty good spread of torque and is incredibly flexible, minus the slightly crappy low-throttle behavior below about 2100 RPM.
There's also a bigger set of cams (234° in / 240° ex @ .050") on the shelf, but I have always assumed they'd be too much for street use (and the stained glass connecting rods), even with ITBs.
Maybe the answer to David's question is, "Yes, and some cams while you're at it."
To clarify the above a little bit, I don't actually know where the cam timing is by the numbers. This is an oddball engine with a tall block, and consequently, cam timing is skewed relative to the crank, so rather than doing the math every time and keeping records like someone who knows what he is doing, I just moved them until I stopped seeing improvement.
In reply to DarkMonohue :
In your case, they would probably help with the drivability, although it seems like your engine is pretty well sorted, and who drives below 2k anymore anyway?
Pete. (l33t FS) said:In your case, they would probably help with the drivability, although it seems like your engine is pretty well sorted, and who drives below 2k anymore anyway?
As ludicrous as it sounds, I upshift at 2100 around town if I'm not in a hurry. And the car will probably get a transmission swap to bring the engine speed down at cruising speeds. With the driving I do and the grunt on tap, there's just no need for stump pulling gears. So maybe the ITBs, with a nice progressive linkage, would bring some tractability back to the combination. Or maybe I should just start taking the bus...
Anyway, this has derailed the thread long enough. Hopefully there is enough relevance to the original question to be of some value.
In reply to DarkMonohue :
It's all good info.
The biggest concern about going to throttle bodies: losing the car's current drivability. Even with the tuned ECU, the aluminum flywheel, the typical bolt-ons, etc., etc., the car still starts, idles and behaves like a stock Miata.
But IRTBs would look and sound so sweet....
Here is the answer for your problem.
3D print some fake throttle bodies and glue them to the plenum.
Still drivable? Yes! Throttle-body-ness? Yes!
In reply to Noddaz :
Ooooo, I like that. :)
In reply to David S. Wallens :
I understand this, but having gone down the road for a year now, it is possible to achieve near stock drivability by adapting a Miata IACV to the ITBs. My car starts, idles, and cruises almost stock-like (cold tip-in is still problematic). I'm using an MS3Pro PnP ECU in an otherwise stock BP-4W, running ITB mode on firmware 1.5.1.
I drove the car successfully to Flyin' Miata summer camp this year, an 8 hour roadtrip, averaging 34 MPGs if I wasn't WOT....which is harder than it sounds. Elevation changes were no problem, and hearing the snorts and hunks through the tunnels makes the whole thing magical, and the noise at 7500 RPM is intoxicating.
I won't lie though, it has taken many hours of tuning, self-learning, testing and research to get it to where it is. Tuning it with the stock plenum in Speed Density was considerably easier and faster. 10/10 will do again. For whatever is worth, this is my first full standalone ECU, and also my first go at ITBs...so if I can do it, so can others. I haven't been to a dyno yet, all tuning has been on the road and track, but Megalogviewer HD has made it all possible.
I have videos on youtube and my MSQs available on Google Drive if interested:
https://youtu.be/ivztk6lgnGA?t=98
https://drive.google.com/drive/folders/1965KMVTPOUDmEtPViJejTJip_vJeBtNP?usp=sharing
In reply to Ricardo :
Welcome to the board, that's an epic first post.
In reply to Captdownshift (Forum Supporter) :
thank you! I'm always too shy to post in forums, but I would like to see more ITBs around.
Another newbie here, planning to go the NA6, Jenvey Heritage DCOE ITBs and MS3ProPNP
I am currently mocking everything up for placement and wiring and fuel line placement. I have got all of the wiring sorted out with the exception of the IACV. Hopefully, Ricardo might be able to offer some insight into how he got a stock Miata valve to work with ITBs. I was considering the solution offered by DIYAutotune, but have wiring confusion.
Physically I need to move the engine removal fastener fitting by the main earth and the manifold mount and solve the issue of the PCV valve, but otherwise there aren't any major space issues.
Once I have this stuff mocked up, then I will clean everything up before putting it back together and trying to start it and configure all the new parts.
Help appreciated, I understand it isn't going to be a power monster, but looks, sounds and handling are important in these little things.
Nick
In reply to Spoons66 :
Very cool and thank you for sharing. Welcome to the forum as well.
I'm sure the rest of the forum can help answer your questions.
In regards to the IACV, has anybody taken an NB IACV, fabricated a mount with two brass threaded hose barbs, then placed it between the vacuum coming from the ITBs and the Vacuum distribution block that most folks seem to use?
It looks like a relatively simple exercise probably by repurposing some kind of blocking plate and some drilling.
It could then be mounted to the bulkhead underneath the front suspension mount.
This would seem to be the simplest solution from both a wiring and fabrication basis, as it retains the two wire connectivity of the NA6 Idle switch?
Nick
Apparently it is necessary to have one end of the IACV open to the air, so a T fitting might be needed. Not sure...
Apparently it is necessary to have one end of the IACV open to the air, so a T fitting might be needed. Not sure...
The IAC mounting block is the vacuum distribution block. There's at least one UK company that makes one, and I had one originally intended for a supercharger on my car. Just put a filter on the IAC inlet. It's fundamentally not complex but a lot of IAC installers view it as rocket science so they don't bother. The car runs much better with it.
Keith thanks. Can you recall the name of the UK Company?
I will GTS it and see what I come up with.
Thanks, really appreciate FM and your forum contributions.
Nick
I've been trying to find it again. It showed up in the ITB Miata facebook group a while back. The one I used was (I think) from a BRP supercharger. But really, it's just a block that has holes drilled in it :) Something like this:
No pics of the unit I used other than this one - it's the bit with the four red vacuum lines running to it. No check valves or anything goofy. I don't think I have it anymore but I'll take a look in my ITB parts stash.
OK, "fit for purpose" as they say !
Looks kind of like what i was planning on fabricating.
Thanks much
Nick
YES.
Ok now I'll go read the article.
The 2 wire VW valves already use 3/4" hose connections and are pretty easy to integrate and control. I usually use a bit of fuel rail extrusion and put a hose barb or weld on a fitting for the valve, and filter on the other end.
https://sps-motorsportshop.com/shop/en/part-shop/performance-parts/mazda-mx-5-nb-1999-2000/enginebay/1-6-l/equipment/2596/idle-control-valve-kit-for-itb-mx-5-na/nb/nbfl?number=LLRV-ITB
German manufacture of a solution.
Sorry for not noticing this before, but Keith has gotten you in the right direction, and the SPS solution is a good one too.
I plumbed my IACV to the vacuum manifold I share for the MAP and the ITBs. The Borla Induction setup has a big vacuum port that's shared by all the runners and that's what I plumbed to the vacuum block and put a small air filter on the intake side of the valve. With that said, my setup isn't able to increase the RPMs very high when the engine is cold, so something is wrong. Something like what Keith posted might work better because it's more direct. I intend to redo the vacuum in my car after the holidays to solve this problem.
I'll look for pictures, and could take better ones when I get back home in a few days
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