Guest Ash Posted November 8, 2001 Share Posted November 8, 2001 It is true that a wideband sensor setup is no better than a homebrew setup when comparing *general* rich or lean conditions (where the definitions of the words rich and lean are in accordance with what appears to be the general BBS definition of these terms). But in setting up the fuelling of a high power forced-induction engine it is not enough to know the general conditions: it is vital to know the specific conditions. Hence the requirement for proper calibrated instrumentation. Further, because a MKIV engine can be said to be running "rich" at WOT does not necessarily indicate a correct condition. I note people on this list take the word "rich" to mean any condition less than 14.7 A/F and "lean" to be any condition above it. It would be perfectly possible to have a situation with a MKIV where I would conclude the car was running lean at WOT; and where someone using a Pete-type setup would conclude the car was running rich, under the same conditions. A forced-induction engine at WOT, at maximum torque, should be running between 11.8 to 12.1 A/F. Though with a car that has had its boost raised from stock, using stock turbos, I would play a little cautious and tune for around 11.0 to 11.5. Toyota play it even more cautious and tune the car to 10.0 (well the VVTI car that is, as it is the only bog-stock car I have managed to test to date). According to (what I would say is) the true definition of the conditions rich and lean, I would regard any fuelling measurement above 12.1 A/F, at maximum torque, at wide-open throttle, to be a lean condition. However, according to the general list definition of the two conditions, a reading of 12.2 A/F, say, would still be thought of as a rich condition (and therefore okay presumably). The converse could also be said to be true. In that it would be perfectly possible for me to conclude that a MKIV engine was running rich, at maximum torque, at wide open throttle. And I suppose most (if not all) members on this list would say, "That is how it is supposed to be!" Well, no, not exactly: it could well be the case that the engine was running an A/F of, say, 8.5 when it should be more like 11.5. The only reason why Toyota (and other manufacturers) fit an oxy sensor is so that, under LIGHT CRUISE conditions, they can run the engine with the maximum possible efficiency. Which in turn gives the lowest emissions and maximum possible fuel economy. Closed-loop is a feature that was born from the result of ever tighter emissions regulations. As such, virtually all cars use the most basic oxy sensor their manufacturers can buy... one that is heavily optimised to give an accurate reading at 14.4 A/F only. The VVTI car I tested ran lean simply because the FCD clamped the pressure signal (or was it the air-flow signal - I mislaid my notes). There is no mystery in my mind as to why the lean condition came about. If you take a MKIV and clamp the pressure signal... fuel-flow stops. It really is that simple. Also, there is also no merit in judging the result of an experiment unless one can be absolutely sure of a sound basis. A basis upon which any particular measured condition can be compared. For example, if a MKIV has a suspect fuel-system then any comparisons made between that car and others will be thwarted. Likewise, if a car has had the fuel pressure raised then any comparison with a bog-stock car will have no real bearing. But, provided it's not my engine........... Yours, J Quote Link to comment Share on other sites More sharing options...
Guest Ash Posted November 8, 2001 Share Posted November 8, 2001 Quote: from Martin F on 11:14 am on Nov. 8, 2001[br] Just that most of us with the DSBC or SBC-iD are running gains of no more than about 15, as any more results in very large boost spikes. This also correlates with the settings given in the un-official user manual. What peak reading did you get after a run with the gain set at 50 ?? No large boost spikes in our case. Boost peaked at 1.02 to 1.04 Bar and settled at about 0.98 to 1.0 Bar. We did several runs just to be sure. I did read something about what you are saying and set the gain to 10, initially. But 50 ended up about right. It did cross my mind that it seemed a bit way off when compared to the general concensus. But when did anything I ever do agree with the general concensus. I suppose I just put it down to people not fitting the unit correctly, or such like. Also, at the back of my mind, I did think that all the talk of boost spikes seemed a little strange. Especially considering the fact that the Blitz double-solenoid setup was designed precisely in order to prevent such spikes (or at least that's how I understood it). As I say, maybe people aren't fitting it correctly, or something. Yours, J Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted November 8, 2001 Share Posted November 8, 2001 I must say that JA's argument was very valid. I was assuming that 14.7 was the ideal and forgot that in fact 14.7 is a compromise and is for efficiency mainly and not power. I have a graph somewhere showing this and yes around the 11's,12's is ideal for more power. I still think a simple device can give warning of impending doom but now maybe it should ONLY be viewed with a better sensor like a wideband sensor. More investigation is needed I think. It's a shame they changed the fuel mapping of the VVTI so much that it goes lean just above fuel cut. Have you done the exact same test on an equivalent non-vvti'd car? Ummm! Got me thinking now... Nice discussion. POete Quote Link to comment Share on other sites More sharing options...
Alex Posted November 8, 2001 Share Posted November 8, 2001 On my SBC-iD I have now set the following programs after reading Ash's post and deciding that it was worth an experiment. Channel 1: Set 30 Gain 15 Channel 2: Set 40 Gain 20 Channel 3: Set 50 Gain 25 Channel 4: Set 60 Gain 25 The only one I've tested is channel 3 and that goes like stink all the way to 1.1bar in 5th (got both cats in still). Compared to Set 50 and Gain 15 which it was on it goes like a train right through the rev range...to be honest it scared the cr4p out of me Set 50 gain 15 only got me .95bar so upping the gain upped the boost. The temperature gauge was still normal and of course I have no Stress-o-meter to see if I was really pushing the engine too hard but hey I've never seen a motorbike disappear into the back ground so fast in all my life (admittedly it wasn't a sports bike but it was a bike none the less)! I have no real idea what gain and set mean but turning up the gain has brought a big grin to my face. Channel 4 is scramble mode really used fleatingly, I can see its new gain position pushing thru 1.3bar which would be a high for my engine, and only something I'll do in cold weather. Quote Link to comment Share on other sites More sharing options...
mark brown Posted November 8, 2001 Share Posted November 8, 2001 The gain sets how fast the boost builds, if set too high say 70+ you can get spikes but they are not large, but mine is set to 45. The setting sets the level of boost achieved. I can't say I've noticed much difference between 45 & 70 on gain You can't limit the boost below the stock level, and without cats that is 19 psi for me. I have set at 70(21psi) 80 (23psi)90 (26psi), 100 (30psi). At 100 the wastegate is held closed I believe. Anything below 70 has no effect and just gives 19 psi. Don't ask what I run most of the time Mark Quote Link to comment Share on other sites More sharing options...
Guest Ash Posted November 8, 2001 Share Posted November 8, 2001 Quote: from TRL Performance on 2:42 pm on Nov. 8, 2001[br] Nice discussion. POete Yes, me likewise. Such discussion is exactly what the technical section of this BBS was made for. Yours, J Quote Link to comment Share on other sites More sharing options...
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