Snowman3karrotz Posted October 21, 2009 Report Share Posted October 21, 2009 Hey whats up everyone? I was wondering how accurate are the stock boost gauges? it says im boosting 7psi BUUT i bought a new boost gauge from AEM and it says im boosting 4psi. which one should i trust? and i know I installed it right because I took it in and they rechecked it thanks in advance yo Link to comment Share on other sites More sharing options...
BrazilBoy Posted October 21, 2009 Report Share Posted October 21, 2009 Stock boost gauges are crap... Link to comment Share on other sites More sharing options...
ucw458 Posted October 21, 2009 Report Share Posted October 21, 2009 Stock boost gauges are pretty close to actual boost but not 100% accurate. My stock gauge was reading within 1/2 psi of correct boost when I replaced it for an autometer unit. Is your wastegate actuator loose or did you have to pull it hard to connect it to the wastegate? The actuator should be tight. As in with it off it should be adjusted to almost 1/4 inch short of where it needs to be. Then use compressed air or muscles to get it attached to the wastegate. If you don't do it that way you wont get stock 7 psi of boost. You will be a few psi short, and will only get 4-5 psi of boost. Link to comment Share on other sites More sharing options...
Snowman3karrotz Posted October 21, 2009 Author Report Share Posted October 21, 2009 Stock boost gauges are pretty close to actual boost but not 100% accurate. My stock gauge was reading within 1/2 psi of correct boost when I replaced it for an autometer unit. Is your wastegate actuator loose or did you have to pull it hard to connect it to the wastegate? The actuator should be tight. As in with it off it should be adjusted to almost 1/4 inch short of where it needs to be. Then use compressed air or muscles to get it attached to the wastegate. If you don't do it that way you wont get stock 7 psi of boost. You will be a few psi short, and will only get 4-5 psi of boost. damn dude, your a monster lol hey i just sent you a pm.. Link to comment Share on other sites More sharing options...
mikec Posted October 22, 2009 Report Share Posted October 22, 2009 What model year is your car? The 87-later cars use a boost gauge driven by the ECU; it's an estimated boost level based on airflow sensor output (frequency/counts) and engine RPM. The earlier cars have an actual boost pressure sensor mounted to the firewall, near the brake booster. If you have that sensor, verify the vac hoses going to it, and to the little vacuum/boost switching solenoid next to it, are tight and don't have any leaks. For your aftermarket boost gauge, where do you have it connected? If you meaasure boost pressure between the turbo and intercooler, the aftermarket gauge will read 1 to 2 psi too high. For StarQuests, the airflow sensor MUST be the correct part or one specific "upgrade" sensor from a certain Mitsu engined cars. Most Mitsu cars of the 80s/90s used similar/compatible airflow sensor assemblies but they are "calibrated" differently based on different sized engines. Open the air filter canister and remove the lid + airflow sensor assembly. Look at the two plastic tubes attached to the sensor assembly - the "bypass tubes." Both tubes should be open (some other Mitsu models have one or both tubes capped/plugged) and both should be the same internal (open) diameter. If you have a capped tube, or if they are different diameters, you've got an airflow sensor for a smaller engined car... and since less air is being bypassed around the actual airflow sensor portion, the whole assembly is giving incorrect information to the ECU and the ECU thinks more air is going into the engine... ergo a high boost reading. That'll make the ECU run the engine over-rich: you'll get lousy fuel economy and likely horrible emissions plus black exhaust smoke from the excess fuel. Next, look at the electrical connector of the sensor. It should have 6 pins, and a solid plastic rim around the pins. If your sensor looks like it has (or had) 7 pins, and/or if the plastic around the pins has a busted part, your car has a sensor from a first-generation Diamond Star Motors car (1G DSM ==> Eclipse, Laser, or Talon). That's okay - that sensor can measure higher airflow than stock but it does have a different calibration from the factory StarQuest sensor and your dash gauge can read incorrectly. The 1G DSM airflow sensor is the only "plug in" non-stock sensor that'll work correctly on the 87-later StarQuests. On the earlier StarQuests, the pinouts are different enough that it's not a direct plug-in though it can be rewired to work. While you have the sensor out, look at the "honeycomb" grid at the inlet (bottom end) of the sensor assembly. That honeycomb MUST be installed and un-bent on the factory StarQuest airflow sensor; and should be installed for the 1G DSM "upgrade" sensor. It straightens the airflow... because the sharp turn the air has to make to go from the air filter to inside the sensor leads to turbulence. This honeycomb "chops up" the turbulence eddies into dinky eddies that quickly die out, leading to nice even "laminar" airflow through the body of the airflow sensor. Then the air hits that plastic wedge-shaped piece; that wedge causes new eddies/vortices which the actual sensor "counts" to measure the airflow. Without the honeycomb, you'll have eddies/vortices caused by that sharp turn; they'll go to the sensor assemblies and get counted as if they were made by that plastic wedge, leading to an excessively high count ==> a high count is "lots of air" to the ECU. mike c. Link to comment Share on other sites More sharing options...
Recommended Posts