Mr. Fish Posted July 30, 2008 Share Posted July 30, 2008 As the VVTI is MAF based I wonder how it differs from the MAP based cars? BPU works okay on the MAP cars because the sensor can't read above 1.1bar so in terms of fueling it makes no odds whether it's clamped or not. The only drawback of the greddy is that it completely removes any boost cut and has no safety margin if it overboosts thats not the case with the HKS ones (i.e Non Clamped) as it goes...Map Sensor---> FCD-----> ECU, surely that means that the ecu is never going to get the correct reading from the map sensort as the HKS unit fools the ecu into thinking its running alot less boost than it acutally is, hence it not hitting fuel cut...that then means you end up running more boost and less fuel...you then end up running pretty lean... Or have i got that completely wrong ? Quote Link to comment Share on other sites More sharing options...
Mike B Posted July 30, 2008 Share Posted July 30, 2008 (edited) A question... is the det detection set up on a VVTi easy to test to make sure its working ? It will produce power for half a second and then shut to 2/3rd throttle.. then as the revs rise and any det goes it will feed throttle back in, unless it's detting bad, then it will not give you anything more. I can see it happen on mine with bad fuel, too much advance and it can be seen clearly in the dyno, according to different levels of tune. It's very good! On hot track days heat soak will cause the throttle to shut as the engine gets warmer and warmer. It is so sensitive that I have had to fit an external det monitor to the car to check what it is reading.. but it will really get a hold of your throttle. The dyno operator was seing power fluctuations and boost drops, yet could not hear det.. retard the ign and car pulls perfectly so it seems very sensitive. In theory impossible to blow up a VVTI with everything working properly. In theory..... What is surprising is how dangerous your map gets when you use your car on track... mapping is done with a reasonably cool engine, but take it to marham and run it at 4mpg for 35 minutes and feel the heat from the thing when you pull up. The FBW gets really uppity then.... I have 2 afr's in the car and they read about .3 away from each other, always have... one is HKS the other AEM. Edited July 30, 2008 by Mike B (see edit history) Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted July 30, 2008 Share Posted July 30, 2008 One thing to remember is that knock sensors actually ware/deteriorate with age, and will also respond differently dependant on mods done to the engine, i have also wondered at what point the std ones start to loose sensitivity:( Quote Link to comment Share on other sites More sharing options...
Ewen Posted July 31, 2008 Author Share Posted July 31, 2008 VVTi's run very rich as stock, to stop the cats melting. You should have plenty of ceiling de catted. Try nailing it in 4th and see what the mixture is. Not wanting to open a can of worms but some AEM meters don't tally at all with my NTK sensored Motec PLM, and I know which I believe... Sorry Chris, didnt spot your post before I rang you. I took your advice, tentatively... I saw a 11.5 to 12 at around 0.5 bar on a quick stab of the pedal, got a 10 briefly second stab...not taken her up above 3000 rpm foot down yet though. Still, given me some confidence back. BTW, why does the AEM gauge say POO on start up ? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 31, 2008 Share Posted July 31, 2008 Have faith in me, my boy! 10's AFR are very rich, you can pull about 50 BHP more from a VVti with just a Motec and some fuelling mapping, really wakes the things up. Poo? Couldn't possibly comment.... Quote Link to comment Share on other sites More sharing options...
steb9780 Posted July 31, 2008 Share Posted July 31, 2008 The POO, I think is the calibration and selector setting on the back. I think if you had changed it, it would start up with P01,P02,P03,P04 etc. Well that's what I think it is anyway. Quote Link to comment Share on other sites More sharing options...
Ewen Posted July 31, 2008 Author Share Posted July 31, 2008 The POO, I think is the calibration and selector setting on the back. I think if you had changed it, it would start up with P01,P02,P03,P04 etc. Well that's what I think it is anyway. Yup, just reading up on it now. Quote Link to comment Share on other sites More sharing options...
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