MALAK
Senior Member
We always see threads about overheating, radiators, 2 vs 4 blade fans, effects of engine pans, GAV adjustment, what thermostat temp to run (if any), etc.
And then there's the #4 cylinder running hot thread. What does that even mean? I've seen the effects but never quantitative data saying how much hotter it runs.
With all this there are many opinions, some with corroborating data, most without.
I set out some time ago to quantify some of this data. So with a couple current threads going on about overheating/radiators I thought I'd post this to titillate those who might find it interesting.
I've added a data logging system to one of my A's. Currently logging Lambda, IAT, MAP, Ambient Temp, Engine Inlet (coolant) Temp, Engine Outlet (coolant) Temp, and Throttle Position. Ultimately I will be adding individual cylinder EGT, and a coolant temp sensor in the block behind cylinder #4.
My ultimate plan is to test the various things noted above on a triple digit SoCal summer day, then also during less severe conditions.
I've already found some interesting things: for instance my A experiences a mild stumble, right off idle, when accelerating from a stop. Initially I thought this was a lean stumble since the Zenith doesn't have an accelerator pump. Looking at the data its clear this is actually a rich stumble condition. The carburetor is rebuilt and I've checked the float level several times. I hypothesize the stumble is caused by the cap and main jets filling up during idle and the sudden rush of air when the throttle blade is opened draws the fuel out of these 2 jets down to their running level causing a short, but noticeable rich condition. So I may play with float and jet settings as well. The car runs fantastic and the stumble doesn't cause any drivability problems but I do notice it.
A couple other interesting things noted are: there is a sharp increase in IAT after idling. I suspect this is due to heat soak and lack of air flow from the fan and currently the car doesn't have pans. I'm thinking pans may help this but I'm gonna find out.
In the near future I'll be adding the EGT's using a plate between the manifold and block and a coolant temp senor located on cylinder #4.
Finally, with the Lambda probe (wideband O2) I've installed a mixture gauge on the steering column. I find this gauge very useful for adjusting the GAV.
And then there's the #4 cylinder running hot thread. What does that even mean? I've seen the effects but never quantitative data saying how much hotter it runs.
With all this there are many opinions, some with corroborating data, most without.
I set out some time ago to quantify some of this data. So with a couple current threads going on about overheating/radiators I thought I'd post this to titillate those who might find it interesting.
I've added a data logging system to one of my A's. Currently logging Lambda, IAT, MAP, Ambient Temp, Engine Inlet (coolant) Temp, Engine Outlet (coolant) Temp, and Throttle Position. Ultimately I will be adding individual cylinder EGT, and a coolant temp sensor in the block behind cylinder #4.
My ultimate plan is to test the various things noted above on a triple digit SoCal summer day, then also during less severe conditions.
I've already found some interesting things: for instance my A experiences a mild stumble, right off idle, when accelerating from a stop. Initially I thought this was a lean stumble since the Zenith doesn't have an accelerator pump. Looking at the data its clear this is actually a rich stumble condition. The carburetor is rebuilt and I've checked the float level several times. I hypothesize the stumble is caused by the cap and main jets filling up during idle and the sudden rush of air when the throttle blade is opened draws the fuel out of these 2 jets down to their running level causing a short, but noticeable rich condition. So I may play with float and jet settings as well. The car runs fantastic and the stumble doesn't cause any drivability problems but I do notice it.
A couple other interesting things noted are: there is a sharp increase in IAT after idling. I suspect this is due to heat soak and lack of air flow from the fan and currently the car doesn't have pans. I'm thinking pans may help this but I'm gonna find out.
In the near future I'll be adding the EGT's using a plate between the manifold and block and a coolant temp senor located on cylinder #4.
Finally, with the Lambda probe (wideband O2) I've installed a mixture gauge on the steering column. I find this gauge very useful for adjusting the GAV.
