GSXR ITB Experiment: The Aftermath

Posted: August 4, 2011 in Uncategorized

The Intro-

I got some miles under my belt and a couple of issues have crept up, but overall it runs good, 30-35mpg (I still need to use my GPS and figure out exactly what my mileage is), the TB’s have not left me stranded (the tranny is another story grrrrrrr), and I think I have sorted my tune for the most part.  This blog is going to A/V rich, I have lots of pics, a few screen shots of my tune, and a in-car vid so enjoy.


I don’t want to call it a design flaw but the manifolds are a flawed design….with silicone couplers.  I have had numerous times that the TB’s partially popped out and numerous times that the silicon couplers have torn.  I bought a set from a different company and had the same results.  Well my notch is now sponsored by home depot racing, lolololol, just kidding.  Seriously, I went to lowes and got some pcv couplers that were somewhat the right size, cut them to the length I wanted and have been running them.  So far so good, and I suspect they will be just fine.  Hopefully that issue is solved.


Number 2, would be the tune.  I tried using Alpha-N and that never worked as good as Speed Density.  So I went back to Speed Density, got “creative” with the map indexing, and added a 500mL bottle in the vacuum circuit.  It’s working friggin awesome, when I romp on it I got 12.5 AFR and when i’m cruising I got 14.7-15.0, perfect!  The creative indexing makes a night and day difference, changing tune to match my engine is a lot easier then the other way around.

Idle, sweet idle.  We got a love-hate relationship.  This issue is just messing with my insanity, so I have settled on a 1100 rpm idle, and that seems to be the sweet spot.  Anything lower and it gets chunky.  I right now got the cranking trim dialed in to be able to fire up with my foot off the pedal but it’s chunky until i work the throttle and keep give it a little gas till it’s warmed up.  I’m pretty sure it’s just a after start enrichment issue, gotta keep playing with it.


What would I do differently if I were to do it all over again?  Instead of using t4 fi mani’s and clamp/coupler method I think modified IDF mani’s and flange spigots would be much more elegant.  Either cutting off the flanges and moving them to the correct center to center distance or cutting them off and using weld plates.  I could shorten the shit out of some IDF mani’s for my type 3 engine bay doing it that way too, or leave then long for type 1/2/4/914 setups.  Type 1 IDF mani’s would be difficult to shorten since the ports are so damn close.  I’m just thinking out loud, it looks like version 1 setup has become a winner.

The outro-

So I’m finally happy with my engine, fuel system upgrade is on the plate and then ethanol tune.  May or may not happen right away.  There is a big VW show in Austin in the begining of October.  That will be the first long trip for the notch (I think it’s about 200+ miles away).  A great oppurtunity to use the gps and get a accurate mpg calculation, should be interesting.  I’m going to leave you with a little in-car vid, till next time…same bat channel, same bat station!


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