Mivec and boost
Jul 10, 2007, 01:24 PM
#1
Mivec and boost
Has anyone else identified a possible correlation between mivec advance and boost levels? I removed a dip in my mivec and and it flattened out a dip in my load levels and my boost seemed to hold better through that area although I dont have logging ability with my map based boost gauge (AEM) so I'm not sure if it only affected 2byte load or actual boost as well.
Jul 10, 2007, 01:27 PM
#2
I can see where this could happen if the MIVEC was actually causing a drop in load. I would think that MIVEC would have greater effect on decreasing boost levels if set improperly than increasing when properly tuned. This is sort of what you described ... not necessarily gaining boost from the MIVEC but more so not losing boost. Someone more knowledgeable is sure to chime in though.
Last edited by TouringBubble; Jul 10, 2007 at 01:29 PM.
Jul 10, 2007, 02:21 PM
#5
and this is what I'm running now. Essentially still the bradley map with smoother transitions and no dip at 3500. one of the things I noticed is that my boost was nice and flat from 4500 -5000.
Last edited by Mr. Evo IX; Jul 10, 2007 at 02:32 PM.
Jul 10, 2007, 03:04 PM
#6
An observation (Yes John you are right), after many weeks of tuning (evogreen) I have found that more advance after 4500 rpm causes loss of boost and timing and leads to det, although does feel like it is holding more torque, but not dyno proven. My conclusion, in this case and with high level of boost, less advance on mivec once turbo is spooled and you'll make better power! If your running low boost I guess there is some gain by advancing the mivec? But not dyno proved.
SK
SK
Jul 10, 2007, 04:52 PM
#7
WOW, my map really gets around (albeit an older version). You got that from someone on another board right, Brady maybe gave it to you after he got it from me?
More advance at like you have in the second map allows for more timing at the same boost level on a stock turbo. Even on a Green it seems you can cram more air. As far as more advance after 4500 CAUSING det or a drop in boost I have yet to see that happen nor seen any log of any car I have tuned have that issue.
I am not saying it cant happen but I am saying its unlikely to happen. Even in high heat and high humidity I havent seen any cars knock. 26psi at peak torque and holding 21 to redline (7500).
FWIW, anytime you have an increase in load it means more air volume and more power. It doesnt always mean more boost but generally it does if everything else was the same (cams, turbo, etc.).
More advance at like you have in the second map allows for more timing at the same boost level on a stock turbo. Even on a Green it seems you can cram more air. As far as more advance after 4500 CAUSING det or a drop in boost I have yet to see that happen nor seen any log of any car I have tuned have that issue.
I am not saying it cant happen but I am saying its unlikely to happen. Even in high heat and high humidity I havent seen any cars knock. 26psi at peak torque and holding 21 to redline (7500).
FWIW, anytime you have an increase in load it means more air volume and more power. It doesnt always mean more boost but generally it does if everything else was the same (cams, turbo, etc.).
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Jul 11, 2007, 02:51 PM
#10
I'd like to check out your latest mivec implementation as well. Although my car is running strong as an ox right now. As far as the one listed, I'm pretty sure I got it directly from you in a thread you linked to a screenshot of it per my request.
Last edited by Mr. Evo IX; Jul 11, 2007 at 02:54 PM.
Jul 16, 2007, 12:24 PM
#13
I'll retract the statement I made early in this thread. I've found that with the stock cat in place (I haven't tested otherwise) that lowering the values in the upper RPM range of the VVT map can actually allow you to hold more boost to redline. I was able to hold about 1.5 psi more @ 7000.
However, this also seemed to reduce to power output even while AFRs and timing stayed mostly consistent.
Testing was done using Mrfred's Excel calculations and EvoScan on the same piece of "track" and in similar conditions. I made one pass, changed the values, then made another pass about 20 min later.
Anyone have thoughts on this?
However, this also seemed to reduce to power output even while AFRs and timing stayed mostly consistent.
Testing was done using Mrfred's Excel calculations and EvoScan on the same piece of "track" and in similar conditions. I made one pass, changed the values, then made another pass about 20 min later.
Anyone have thoughts on this?
Jul 16, 2007, 02:18 PM
#15
Bubble, did you also notice a decrease in the load the car is running in? If the power dropped off because of the MIVEC I would think the boost would also have dropped off. Odd, but if you say so I will believe it. Any logs to compare though?
What myself and others have been noticing is that some cars will respond favorably to a little advance, some wont show any changes, and some will lose power. There doesnt seem to be anything connecting which ones will behave which way. Altitude, humidity, MR or GSR or RS, none of it seems connected.
What myself and others have been noticing is that some cars will respond favorably to a little advance, some wont show any changes, and some will lose power. There doesnt seem to be anything connecting which ones will behave which way. Altitude, humidity, MR or GSR or RS, none of it seems connected.