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This actually sounds like something I'd love to see and try, but I'm mostly just looking to clean up the seams. The plastic isn't really thick enough to do anything serious with and it looks like there is only two places I might be able to mess with to increase plenum volume and I wouldn't want to get too aggressive with that.
Are you able to simulate airflow and whatnot? I do have a model for a more performance oriented manifold I poke at from time to time and I keep starting over due to being unsure of the plenum and throttle body location.
Been working a lot lately so slow progress here. I've been able to open up the manifold to have a 74mm opening, any more and I'm pretty sure I'll have a hole behind the throttle body. I've also made and blended in an adapter for the 76mm throttle body I have laying around. Of course the ecu doesn't like the larger throttle body, I'm hoping to get that resolved with some help from ovtune. I don't know what to expect for gains, hopefully something like 5hp can be had from this.
Max Bore www.maxbore.com is able to bore the OEM TB. I received a quote for $125.
Has anybody done this yet? If so, how did the factory ECU react?
-Kenji
Originally Posted by DickH
Been working a lot lately so slow progress here. I've been able to open up the manifold to have a 74mm opening, any more and I'm pretty sure I'll have a hole behind the throttle body. I've also made and blended in an adapter for the 76mm throttle body I have laying around. Of course the ecu doesn't like the larger throttle body, I'm hoping to get that resolved with some help from ovtune. I don't know what to expect for gains, hopefully something like 5hp can be had from this.
I have sent a throttle body to maxbore, I believe I mention it a few pages back. If you do this, the largest you can go with the manifold without modifications is 72mm which didn't really show much for gains. The ecu can deal with a 72mm throttle body without too much hassle, I can't say how large is doable before you have problems. I have debated sending out my spare throttle body to have it machined to 74mm which is about the limit of how far you can open up the upper manifold.
I use measured maf values to compare mods for gains, I would never expect to actually feel it. Peak airflow gains were ~2g/s which is within what measured readings would vary throughout the day. I would say that the cost is not worth it for what little gains I saw with the 72mm throttle body.
I have made some changes to the tune so that the throttle body doesn't start to close up on me at WOT and figured I should revisit using the larger throttle body. I have modified an upper with a 3d printed adapter that I tapered back into the manifold at a gradual angle. This required adding material to the manifold to fill in some holes that formed. I also modified the throttle body by taking out half the shaft and machining out the inlet so it tapers to an edge that sits flush with the coupler. I figured this would supply all of the air I would need. As for results, with the adjusted tune, my peak MAF readings with the 74mm throttle body increased to mid 260s. I have a few low 270s with 40F IATs. Switching over to the 76mm throttle body was disappointing as so far my best peak MAF reading has been 258. I am not sure why it is worse, everything about the larger throttle body is better and I had expected at least the same peak values.
I don't have a stock throttle body to compare with and its not fair to compare with some of my older logs as some things have changed with my car. Shortly before the changes in the tune it would be in the high 250s-low 260s, with the highest maf value I had recorded being 264g/s. Changes made to the tune were to requested torque so the throttle body would actually open all the way at WOT. I had noticed that the throttle body would taper down to ~60degrees at WOT and I swear I could feel it pulling back when driving. This has been corrected and I am seeing ~82 degrees throughout the pull. So not really a dramatic change, maybe a peak difference of 3-5hp.
I'm using BitEdit, there is a table named "optimal torque" that has target power values for throttle position and RPM. The ecu uses this in calculating how far to open the throttle body.
I think my maf may have gotten dirty somehow when I was swapping out the intake manifold. My values were notably lower when I swapped back to the ported stock throttle body. Messing with my maf was the next thing on my to do list so I just moved on. I cleaned the maf and installed it in a full 3.5" intake system. I'm on my second revision for rescaling my maf for the intake. New peak values are hovering around 270. I was aiming for 265 so I think I am really close. Once I am finished with this I'll go back and try the larger throttle body again.
03-08-19, 07:32 AM
