90mm t-body ?
11-25-2008, 09:12 AM
#12
Well, I tuned for it when I did the 90mm upgrade with the Radix and I am doing it again with my 408. Really there is a minor change and it is possible to leave your tune the way it is and be totally fine as it only messes with idle and just off of idle driveability IMHO. If you are going to change your tune based on just a TB upgrade, there are two tables you can mess with. First one is the ECT Scalar as previously mentioned. The stock value for a 78mm is most likely 0.0255 or around there so if you went with an LS2 90mm TB, the correct value is 0.0190. Since you have an 87mm (as I understand it) there will not be a big difference at all. If you choose to adjust this value, the scalar should move down in value not up as it's an inverse relationship to the throttle body "size" (hence going from 0.0255 for the 78mm to 0.0190 for the 90mm). The next table that can be adjusted is base running airflow to make the STIT and LTIT happy (within 1 g/sec), however, it will most likely be a minor change if your base running airflow table was already dialed in. That's about it. You can also go into the "IAC steps VS effective area" but from what I have experienced with both of my set-ups, it wasn't necessary really.
Last edited by krambo; 11-25-2008 at 09:16 AM. Reason: spelling
11-25-2008, 09:24 AM
#13
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Well, I tuned for it when I did the 90mm upgrade with the Radix and I am doing it again with my 408. Really there is a minor change and it is possible to leave your tune the way it is and be totally fine as it only messes with idle and just off of idle driveability IMHO. If you are going to change your tune based on just a TB upgrade, there are two tables you can mess with. First one is the ECT Scalar as previously mentioned. The stock value for a 78mm is most likely 0.0255 or around there so if you went with an LS2 90mm TB, the correct value is 0.0190. Since you have an 87mm (as I understand it) there will not be a big difference at all. If you choose to adjust this value, the scalar should move down in value not up as it's an inverse relationship to the throttle body "size" (hence going from 0.0255 for the 78mm to 0.0190 for the 90mm). The next table that can be adjusted is base running airflow to make the STIT and LTIT happy (within 1 g/sec), however, it will most likely be a minor change if your base running airflow table was already dialed in. That's about it. You can also go into the "IAC steps VS effective area" but from what I have experienced with both of my set-ups, it wasn't necessary really.
you wernt joking when you said you would have a nice long write up when you were done with the idle tune.
I have been running 90mm for while and i havn't messed with the tune at all and it's fine. I could use some tuning with my cam but its fine as is.
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