Re: Knock. A question for Graham or Marc - Page 4 - ZR-1 Net Registry Forums

XfireZ51 · 10-21-2019

Very true on the SA v MAT table. That explains why we perceive that the LT-5 LOVES cold air and delivers snappier performance. Under normal operating conditions, the MAT will typically show an air temp of 70-90C. If its located, as mine is downstream of the radiator but ahead of the airbridge, it never reaches higher than 45C or so. If that table is not modified, u would end up w an extra 3* SA which could create a situation (ie knock) where the knock sensor invokes the ECM to retard timing.

Marc, so I assume when u relocate the MAT sensor and basically convert it to an IAT (Intake Air Temp) sensor, you also modify the MAT/CTS Blend table for fueling.(see attached).
Once the MAT is relocated and used as an IAT, the ECM will likely NEVER see the air temps where the stock calibration assumes normal operating conditions to be. So they need to be modified to operate correctly with the "new normal" relocation of the MAT/IAT sensor brings about.
Some would make the argument that u would compensate for the MAT relocation using the VE tables, but that would be incorrect. If you datalog the motor during varying outdoor ambient temps, u would find that what may have been an optimum tune in say temps of 70F, are not in 50F or 90F. When u modify the VE table to achieve a particular BLM or AFR, the modification will only be valid for those particular conditions found during ur datalog. In fact, if you sit there idling, intake air temps rise, what was a good BLM when u first started idling will go likely rich as temps rise if the table was kept stock. The MAT Compensation table is used to modify the VE in order to maintain a stable BLM regardless of intake air temps.

Perhaps Graham could chime in on whether the MAT Comp table is active for both Closed and Open loop operation. I would think it would be for both.

Hib Halverson · 10-26-2019

Quote:

Originally Posted by XfireZ51

Very true on the SA v MAT table. That explains why we perceive that the LT-5 LOVES cold air and delivers snappier performance. (snip

Any performance engine loves cold air and delivers "snappier" performance when it has it.

10-21-2019	#31
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,696	Re: Knock. A question for Graham or Marc Very true on the SA v MAT table. That explains why we perceive that the LT-5 LOVES cold air and delivers snappier performance. Under normal operating conditions, the MAT will typically show an air temp of 70-90C. If its located, as mine is downstream of the radiator but ahead of the airbridge, it never reaches higher than 45C or so. If that table is not modified, u would end up w an extra 3* SA which could create a situation (ie knock) where the knock sensor invokes the ECM to retard timing. Marc, so I assume when u relocate the MAT sensor and basically convert it to an IAT (Intake Air Temp) sensor, you also modify the MAT/CTS Blend table for fueling.(see attached). Once the MAT is relocated and used as an IAT, the ECM will likely NEVER see the air temps where the stock calibration assumes normal operating conditions to be. So they need to be modified to operate correctly with the "new normal" relocation of the MAT/IAT sensor brings about. Some would make the argument that u would compensate for the MAT relocation using the VE tables, but that would be incorrect. If you datalog the motor during varying outdoor ambient temps, u would find that what may have been an optimum tune in say temps of 70F, are not in 50F or 90F. When u modify the VE table to achieve a particular BLM or AFR, the modification will only be valid for those particular conditions found during ur datalog. In fact, if you sit there idling, intake air temps rise, what was a good BLM when u first started idling will go likely rich as temps rise if the table was kept stock. The MAT Compensation table is used to modify the VE in order to maintain a stable BLM regardless of intake air temps. Perhaps Graham could chime in on whether the MAT Comp table is active for both Closed and Open loop operation. I would think it would be for both. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX Last edited by XfireZ51; 03-08-2024 at 02:09 PM.