S2000 Lean VTEC | AEM
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Jmz
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Joined: 06/17/2018 - 08:21
S2000 Lean VTEC

I have a supercharged 2000 S2000. Recently got hte car tuned on AEM infinity and there is a lean spike at vtec transition. I tried richening that part of the map but the jump is still there. It makes pre-vtec too rich and the ECU does not react fast enough to lean richen the mixture as VTEC hits.

How is everyone dealing with this? Given that I spiked to 13 AFR at 2 psi, i think it should be safe for hte engine. However, is there anyway to make the transition smoother? We lowered the vtec to 4500 RPM so thats where the spike is.

AEM_PT
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Joined: 05/22/2014 - 08:13
Are you using two VE tables

Are you using two VE tables for Vtec Low/High cam activation? Try the attached guide https://www.dropbox.com/s/yotxa7ihilh70gr/AEM%20Infinity%20DIY%20Tech%20Guide.docx?dl=0

Jmz
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Joined: 06/17/2018 - 08:21
Thanks for the guide. Yes I

Thanks for the guide. Yes I am using a VE blend for vtec. It takes a split second after vtec active is on before spiking to lean. I tried adding several more rpm breakpoints, 100rpm increments around vtec activation to see if I can fine tune the imperfections. However I have not had a chance to take the car out for the drive yet.

Jmz
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Last seen: 1 year 1 month ago
Joined: 06/17/2018 - 08:21
I'm still getting a spike. I

I'm still getting a spike. I've made several breakpoints around vtec and can't get it right. Looks like from 3rd and 4th gear there are different areas of spike around vtec. My question now is... Is it normal and is everyone else experiencing this issue?

Ive added a log and tune file if anyone could take a look. Thanks!

 

JoshR4 d6.itlog

JoshR4 d6.itssn

AEM_PT
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Joined: 05/22/2014 - 08:13
Your log/s do not appear to

Your log/s do not appear to be coming through. Please send them to ems.tech@aempower.com and reference the link to this thread.

AEM_SB
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Joined: 06/07/2014 - 14:29
I found the logs, they had

I found the logs, they had been attached to your forum post but you need to press the 'insert' button so people can see them to download. I edited your post, the logs should be viewable now. 

This screenshot shows your log data viewed using our base layout's Tuning tab, plus I added a new plot showing VE % (which is the result of any map switching or blending) and VTEC_Active. 

 

It looks like a pretty simple tuning problem, don't forget that the O2 sensor's readings will include a slight time delay since the exhaust has to exit the cylinder, travel through the header, then physically get near the sensing element. In other words, it looks like you adjusted the wrong cells in the VETable so you added too much. If you're seeing logs show the O2 is too lean at 4700 RPM, you may need to increase the VETable values at 4500 RPM (or even earlier) to compensate. 

As an aside, for a VTEC car using the second VE Table it's a good idea to set the switchover RPM to something very low (such as 3000 RPM) and tune the lower RPM values in the second VE Table so it runs well from 3000 RPM. Then, set the the switchover RPM to something extra high (maybe 6000 RPM) and tune the main VETable so it runs well in those cells also. Try that, then move your switchover RPM back to the original setting and you should get good results. Seeing where the table values overlap may help choose a better switchover RPM, if you haven't already used a dyno to find which switchover RPM makes the best combination of mid-range and high-RPM power.

 

Hope that helps,

SB

Jmz
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Last seen: 1 year 1 month ago
Joined: 06/17/2018 - 08:21
Thank you very much! Problem

Thank you very much! Problem solved. I was aiming the wrong values because of the delay. Adjusting 4600 rpm hits the spike dead on.

Jmz
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Last seen: 1 year 1 month ago
Joined: 06/17/2018 - 08:21
I found something interesting

I found something interesting. When VTEC switches on, there is a 50 rpm delay before it actually requires the extra fuel. So when i tune high cam VE table for lower RPMs, it becomes too rich at the 50 rpm window where VTEC_Active turns on to where it actually needs the added fuel.

Does AEM have a feature to delay the VE table switchover? Also, I noticed when I tuned the table nicely for 3rd gear, the 50 rpm window becomes too lean in 4th gear. 

Thanks

AEM_SB
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Joined: 06/07/2014 - 14:29
Sorry, there's not a way to

Sorry, there's not a way to adjust the VETable vs VETable2 switchover like you're describing. Have you ever measured wideband O2 on a stock Honda ECU this closely? Are you certain it behaves differently during the VTEC switchover? I'm always surprised when I see the actual fuel ratios measured by adding a wideband to OEM ECUs, it's often different than you might assume. 

In the Diagnostics page of the wizard, there is a channel named 'CrankEdge RPM Smoothing Filter'. It affects the response vs smoothness for the EngineSpeed [RPM] calculation, which gets used in fuel calcs. The wizard describes what it does pretty clearly. Default value is 95 for most calibrations, try decreasing to 80 on your car and see if this affects your engine's 3rd gear vs 4th gear behavior.

 

Remember, if you have to make tradeoffs for different situations it's safer to be slightly rich for a few moments than slightly lean for a few moments.

Aynadzhiev
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Joined: 02/26/2015 - 09:48
AEM_PT wrote:

AEM_PT wrote:

Are you using two VE tables for Vtec Low/High cam activation? Try the attached guide https://www.dropbox.com/s/yotxa7ihilh70gr/AEM%20Infinity%20DIY%20Tech%20Guide.docx?dl=0

Can you re-upload this guide. 

Thanks.