MicroSquirt.com read only forum (Jan.15,2018)

I've read a lot of posts in which people indicate tuning ITBs is difficult for a variety of reasons. Before I venture down that path, I wanted to get a feel for how many folks have successfully implemented ITBs and are happy with the results.

Thanks,
Robert

I've had very good luck with my own ITB's. They do typically have a distinctive VE curve but once you recognise what to look for it's as tunable as anything else. I've found revving from a free load idle to be the trickiest part of tuning but that's just my car. As far as the VE table goes, you would probably wind up with one with relatively low numbers right up until 90 or so kpa and then a rapid increase. If you were to use a generic table generated by Megatune it would probably require alot of tweeking. As far as performance, my own car had a single plane intake and carb before and the 'squirted ITB's are superior in every way. There's a dyno comparison in my success story that shows a bigger torque curve at all rpms. The low speed drivability is nice too. I had expected a touchy off idle response but for some reason it's not like that. They do require attention to detail during setup to the linkage. It has to have enough spring pressure to return the butterflys but if you have many ITBs you may have to have modify the linkage to allow good off idle control.

I run MS2 684 code with ITB's on a 4 pot 2300 8V with a race cam and big valve head. The VE tuning is a bit of an art and a WBO2 is a very good idea as the shape of the VE table is very different from the one generated by the built in table generator. I have found that damping the MAP signal is the biggest challenge. I use a MAP damping factor of 15 with the 4 vacuum pipes commoned to a single plenum of around 40CC's. This seems to work OK but makes the MS react a little slowly when the throttle is buried at lowish RPM's. The XTAU of course is also delayed marginally too. I compensate for this with a small amount of TPS based enrichment as this is instant. I now have no problems with AE at all. I still have a little work to do but despite panicing at times about if I had mode an expensive mistake with ITB's I am now 100% sure they were a good call. They also sound horney as hell! My idle is 1160 RPM and not too lumpy but all my driving MAP is between 85 and 100 so you end up with a very compressed VE table. This means that you cannot afford a rough MAP signal as the bumps and troughs on top of it can throw you a bin or two up and down when in reality the MAP really did not change. Of course this trigger MAP AE and XTAU also and this makes tuning horrible. Get the MAP smooth and all the problems go away and you have the ultimate intake system for making real power.

In short, for a weekend car or a racer I would say go for it. For an everyday car that needs to give good MPG and be easy to tune and good drive in traffic you may want to go for a single body but my experience is that its not as bad as some folks indicate if you think about what your doing, take your time and keep your temper.

Jon