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THE WITZL
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July 2002

Re: Boost issues with 4AGZE

Mon, 04 July 2005 04:08

Irish wrote on Mon, 04 July 2005 09:02

All you should have to do is remove the knock sensor from the block and wrap it in some plastic and cable tie it out of the way in the engine bay. Don't forget to leave it plugged in though. You could also bridge it with a resistor at the ECU end. I did this with my GTiR and never had any problems dropping maps after that.

This will most DEFINITELY NOT WORK with a post 09/89 4A-G*** series engine on factory ECU. It has been thoroughly tested with a scan tool on the serial data line from the ecu, and proven that knock control was WORSE with the knock sensor as listed above, inferring that the knock sensor input to the ECU is not only looking for knock, but is looking for a GOOD signal too.....

... hence your suggested solution will not work.

If you are talking about intake temps ABOVE 100degC, then its pretty damn fkn obvious that you are pinging the p00hole out of your GZE, and producing what you call "partial boost" because of the lower density of hot air.....
.... remember that high school science experiement where you heat up a metal can with the lid open, and then put the lid on? Well that's a basic example of the difference in intake pressures between say 30degC and ~90degC intake temps. THINK ABOUT IT.

I myself have a great deal of experience with knock control problems using an AE92 MAP gze ecu + greddy emanage with my 100kW turbo 4a-ge.
The theories were endless, but the most commonly accepted theory was that top end rattles are a VERY similar accoustic noise to knock... smallport 4ag* engines produce top end rattles at as little as 100,000kms. This combined with engine conditions pertaining to knock sends the knock control circuit spastic, and it retards timing to poo-land.

With a supercharger, it is MOST DEFINITELY going to produce lower boost due to the FIXED nature of a supercharger, and how it produced boost. The simplest explanation is that it multiplies intake air pressure... thus if intake air pressure is LOWER due to EXTREME HEAT - you have less boost. Am i not correct (looks around for someone with more of an idea than me).

With a turbo of course, this is difference because you have a wastegate - ie a variable boost control device which compares intake pressure to relative pressure (atmosphere) and opens/shuts a valve accordingly to control intake pressure to a set level. So it will still make the 10psi it normally makes (for example), it will just take longer to get there.

In the end, i gave up and decided that aftermarket engine control and a top end rebuild was the solution... but sold the turbo kit and car separately instead.

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