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Member Since 12 Aug 2017
Offline Last Active Yesterday, 10:25 PM

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In Topic: G25-660, Low torque 1,500-3,500rpm ?

13 October 2020 - 11:04 AM


 but will be improved by ramping in full cam timing until just before full boost is obtained.  



What is cam timing in Datazap, vvt intake angle? What value should be before full boost?

In Topic: G25-660, Low torque 1,500-3,500rpm ?

13 October 2020 - 09:25 AM


I only viewed 1 of the 3 logs, but it shows why you are so laggy.  If you look at your log below I provided some comments to explain what is happening.  When you stab the throttle the tune still commands 0% WGDC until you hit 2800rpm where WGDC goes to 65%.  I don't think the 0% being commanded has much affect on spool since at 2800rpm you are still under the spring pressure on the gate.  However, the fact that you are commanding only 65% WGDC is one reason the car has lag.  For maximum spool you would command 100% WGDC until just before you hit the desired boost and then you ramp it down quickly so that you do not overshoot the boost target.  Remember, boost control on the GTR is all open loop.


The other issue I see is with your intake cam timing, which is also affecting spool.  You want to ramp in full cam timing to promote spool and then just before you hit full boost you want to start ramping out cam timing to promote flow.  I typically ramp out all of the intake cam timing by 6000rpm, but the optimal curve would be determined by a dyno tune.  However, as a rule of thumb the intake cam timing I show in orange is a good starting point. 


Bottom line, the tune is contributing to the lag you experience.

Thank you for explanation. I am still in puzzle here.  What rpm do you get full boost from small turbos like G25-660? Mine has full boost at 3900rpm. Full throttle from 2200rpm, full 2 seconds to be 3000rpm with boost only 10psi which I think it is suck. Is it possible of wastegates leak or someone swapped my turbos and put on old style big turbos?

In Topic: G25-660, Low torque 1,500-3,500rpm ?

12 October 2020 - 11:27 PM

I know comparing dynos is a bad idea but ets hit almost 600ft/lbs at 3000rpm. Not sure what gear they typically dyno in.

At 3000rpm, my boost looks like only 10psi. 

In Topic: G25-660, Low torque 1,500-3,500rpm ?

12 October 2020 - 11:09 PM

Data Logs. 4th gear.



In Topic: G25-660, Low torque 1,500-3,500rpm ?

08 October 2020 - 01:03 PM

Dyno attached