Hokay, so I tried something new.....
As those that are ready to lynch me if I do not get this done soon know, the car was bogging badly when floored between 2500-3000RPM. According to some data logs I took, the AFR was hitting 19.5:1...BAD BAD BAD! Throughout the rest of the range, the car was better than new.
So, one of my biggest goals with this was to have it work with the stock air filter box. Well, before doing too much work redesigning the circuit and adding a throttle position input and all sorts of jazz, I went to TAP Plastics after work and got a few feet of 2 3/4" (70mm) OD acrylic tubing. The intent: velocity stack.
So, I basically made the longest one I could...8" (200mm) off the front of the MAF. I stuck it in the enormous cone filter I had laying around and went out for some tests.
For the gist of it, go to the end where I summarize the below info.
The bogging is not gone, but is a LOT better. I might have a chance to run out tonight and do some logging to see exactly how it has improved, but flogging the car on & off of the highway for 40 minutes seemed encouraging. Things are getting closer & closer to finalization.
A question...IF I was to leave it they way it is, how would buyers feel about the following conditions of use:
- Basically, do not open the throttle over 70% under 3000RPM.
My Note: From driving experience, the best performance comes by gradually opening the throttle anyway. Under 3500RPM, it seems that throttle openings above ~60% all have about the same result in acceleration. If you DO slam open the throttle with ANY sensor on there, the car can actually bog, or at least not perform as well as a more gradual, smooth opening. I am sure most of you have noticed this. The resonance on this motor at those RPM's was already there, the VAM was just not as sensitive and more or less "ignored" this effect.
This is in no way to say that I will not solve this. I have just been working on a solution in almost every free moment I have, and some moments when I should be sleeping. I now have a solution or 2, one of which is more likely to work, but will involve interfacing with the TPS, which means more code, more parts and more cost to everyone. I am somewhat anal retentive as far as engineering a product goes, and I suspect that I may be starting to over-engineer this. I know I expect perfection, but maybe I am losing sight of the customers' desires; and for 1/4 the cost of the next available MAF solution they would be willing to make a little compromise.
So, in brief:
- Ditching the air box has improved results...not PERFECT, but far better. Will post data logger results soon.
- Would "customers" be willing to NOT open the throttle more than 70% under 3000RPM (and as we have noticed with this motor, opening it over 60-100% under 3500RPM is all the same performance-wise)?
- Would "customers" be ok with ONLY using an open-element filter with a velocity stack tube (a tube which I could supply with the converter)? Mounting and heat shielding are the responsibility of the buyer (I MIGHT look into making mounting brackets, but that would add $$ to the unit cost).
