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ITB's bog on accel


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Alright HybridZ, don't let me down! I've been battling with my ITB's for a little bit now and am getting properly frustrated. They are great at wide open, but have a really serious bog on tip in. This is very evident in a 1-2 shift under full power, rather than having smooth power once in 2nd gear, it jerks for a half second, then ramps in power. For auto-x this is super frustrating since there is a LOT of throttle stabs, modulation etc that accentuate the issue. 


A little bit about the motor, its a L28 Rebello built auto-x motor, 63DE cam, 45mm OER ITB's, 440cc high impedance injectors and LS1 coil packs. I'm running an MS3/3x. Tune and log are attached, I'd love it if somebody was able to look in this and tell me if I'm missing something obvious, or if something just looks off. I've had the car on several dynos, and the power is pretty good once it chokes through the stumble/bog. I'm going to have the injectors flow tested tomorrow, hoping that there is some sort of mechanical issue at play here. Coils were replaced recently and in testing, I've got VERY strong spark. 


Let me know if there's anything else that I can post up or answer! Thanks!

Datsun Tune 2018-08-11.zip

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Quite a few things wrong with that Tune. No wonder you are having issues with AE.  Made some revisions to.


1: AE settings. No where near correct. Made several changes there that should be positive. 

2: Target AFR table far too lean at low RPM. VE table greatly affects transition off idle. Going too lean creates a bog. With proper Ve Table, less AE is required.

3: You were running Alpha N. MS3 has a special Fuel algorithm for ITB's. I have enabled that. 

4: Spark Table needed some work

5: I've noticed that you have your O2 feedback control disabled. I have enabled it but set proper settings and filters on it. 


Send me a PM with your E-mail address and I will send you a touched up Tune. This is just a Baseline . but should be an improvement. I also do Remote Tuning and offer full Tunes built for your particular engine specs. 

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BTW, I've got 35+ years of experience under my belt Road Racing, Hillclimbing and Autocrossing. I've always been very successful in Tuning Carbs and now EFI for these types of events. Part throttle and Transitional Tuning is much, much harder to dial in than WOT Tuning. It's an area I concentrate my Tunes on.   

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