VTEC Crossover
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Joined: Nov 2009
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VTEC Crossover
Hi - I know this has been asked many times and I've searched a lot but still need a bit of advice.
When my tuner set the VTEC he said something about a torque crossover on the chart and then set it @ 5700.
My setup is currently a Novi1000 @ 14psi but I'm just about to put a 1200 on at 16PSI+ .. should this lower the current crossover based on the method he did previously? At the moment when it goes into VTEC it just goes crazy at that RPM so I'm wondering if we lower it then it may be a bit more linear.
What should he be setting this to with my new setup as I feel 5700 is a tad high and it sometimes breaks traction in 3rd when it switches over.
Thoughts?
When my tuner set the VTEC he said something about a torque crossover on the chart and then set it @ 5700.
My setup is currently a Novi1000 @ 14psi but I'm just about to put a 1200 on at 16PSI+ .. should this lower the current crossover based on the method he did previously? At the moment when it goes into VTEC it just goes crazy at that RPM so I'm wondering if we lower it then it may be a bit more linear.
What should he be setting this to with my new setup as I feel 5700 is a tad high and it sometimes breaks traction in 3rd when it switches over.
Thoughts?
Joined: Jul 2014
Posts: 13,816
Likes: 1,543
From: Chesterfield VA
Since the torque and horsepower curves of every engine ever made always cross at 5252 rpm (assuming the engine can rev beyond this point) I'm wondering what this is all about.
Torque is a scientific measurement. Horsepower is an arbitrary, made-up formula.
-- Chuck
Torque is a scientific measurement. Horsepower is an arbitrary, made-up formula.
-- Chuck
Thread Starter
Joined: Nov 2009
Posts: 358
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I'm honestly not sure how he got that crossover at 5700RPM I'll have to ask him and just relay what he says - I just haven't got the level of understanding. It just seems high to me. I've attached how it behaves at that crossover;
Joined: Dec 2007
Posts: 4,289
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Lol so the correct way to determine a proper vtec is to set it to engage VERY low, (like 3k rpms) and do a dyno pull. Then set it VERY high (like 7k rpms) and do a pull. Then you take both of those graphs and look at where the torque curves meet.
Note my excellent visual aid
The blue line is what the torque curve would look like only running on the low cam profile (no vtec)
The red line is what the torque curve would look like only running on the high cam profile (always vtec)
Your goal is to replicate these graphs for your car, note where these two points intersect, and set that as your vtec engagement point, that way you maximize your low end torque on the low cam profiles as well as maximize power on the vtec cam profiles.
Since you have a test pipe, it should be around 3500-4200 rpms would be my guess.
Note my excellent visual aid
The blue line is what the torque curve would look like only running on the low cam profile (no vtec)
The red line is what the torque curve would look like only running on the high cam profile (always vtec)
Your goal is to replicate these graphs for your car, note where these two points intersect, and set that as your vtec engagement point, that way you maximize your low end torque on the low cam profiles as well as maximize power on the vtec cam profiles.
Since you have a test pipe, it should be around 3500-4200 rpms would be my guess.
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Joined: Jul 2014
Posts: 13,816
Likes: 1,543
From: Chesterfield VA
Thanks for the diagrams. Where the two torque curves cross based on different cams. Suddenly makes sense! 
Crossing looks remarkably like the 3600rpm VTEC set point my Gernby FlashPro tune is set for.
-- Chuck
Crossing looks remarkably like the 3600rpm VTEC set point my Gernby FlashPro tune is set for.
-- Chuck
Joined: May 2012
Posts: 4,255
Likes: 3
From: SOMD
Lol so the correct way to determine a proper vtec is to set it to engage VERY low, (like 3k rpms) and do a dyno pull. Then set it VERY high (like 7k rpms) and do a pull. Then you take both of those graphs and look at where the torque curves meet.
Note my excellent visual aid
The blue line is what the torque curve would look like only running on the low cam profile (no vtec)
The red line is what the torque curve would look like only running on the high cam profile (always vtec)
Your goal is to replicate these graphs for your car, note where these two points intersect, and set that as your vtec engagement point, that way you maximize your low end torque on the low cam profiles as well as maximize power on the vtec cam profiles.
Since you have a test pipe, it should be around 3500-4200 rpms would be my guess.
Note my excellent visual aid
The blue line is what the torque curve would look like only running on the low cam profile (no vtec)
The red line is what the torque curve would look like only running on the high cam profile (always vtec)
Your goal is to replicate these graphs for your car, note where these two points intersect, and set that as your vtec engagement point, that way you maximize your low end torque on the low cam profiles as well as maximize power on the vtec cam profiles.
Since you have a test pipe, it should be around 3500-4200 rpms would be my guess.
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