Just a quick look at your plot screens I think I saw something that you might want to investigate closer. I may be wrong in what I saw but: Looking at both screens, it appears that the #1 cylinder is running cooler than others (especially #2). #3 and #4 look very comparable, but still slightly lower than #2. Since you have individual injectors in each cylinder, can you adjust the ECU to give you a little more fuel to the low cylinders to get just a little more heat (read power) so that you get closer to the nirvana point of 4 cylinders of identical power output? Another benefit of having the EGT's is something that is well known in aviation - the ability to tune for more power per gallon of fuel. Keep up the good work!
Yes, with Motec ECU I do have that capability. Keep in mind the EGT sensors can have some variation in temp if the probe is not in the identical depth and distance from the value. But you point is on target and the idea is to get the car on a chassis Dyno to work further on the tune. Thanks for the comment!
The interesting thing about EGTs is there’s not a linear relationship between the amount of fuel being injected and heat. In this case, we can’t just assume adding more fuel to cylinder 1 will raise the EGT because cylinder 1 might have been running a little rich which would bring the EGT down. And as cylinder 1 is leaned out (a little fuel is removed), the EGT goes up
And assuming cylinder 1 is facing the front of the race car, I’m inclined to believe it would tend to run a little rich because the ram air from the intake plenum would seem to want to favor the rear two cylinders (3&4) as the path of least resistance of the air forces it to the back of the engine. This would mean cylinders 3&4 are getting a little more air when driving at speed with the ram air effect which leans out those cylinders a little more and brings up their EGTs a little bit
If you don’t already have this installed, it would be quick and easy to put a pressure sensor on your intake plenum so you can data log your intake plenum pressures in various gears and at various speeds (keeping in mind there will be some variability from head / tail winds and whether or not you’re following someone that’s causing turbulence). But once you have this data, you could use an appropriately sized air blower (a good leaf blower is one example) to force air into your intake plenum when on a chassis or engine dyno to simulate the ram air effect. Just adjust the blower up or down to achieve the intake plenum pressures you logged
Hi Jeff, I like that idea. Currently I do have a pressure sensor in plenum and throttle bodies. Not a bad idea, I do see what pressure I get at speed. I’ll try a blower in garage and see how it does. Thanks
Assuming you already have (or will buy) a blower that can supply enough cfm for your engine, this will enable you to test not only the additional overall pressurized airflow the engine is receiving, it will also enable you to look for the small imbalances that typically occur between cylinders when you are on track and the ram air effect is kicking in (or using the blower to simulate). You can then improve your individual cylinder tuning to take into account these differences
Air behaves in strange ways but my initial assumption is the rear two cylinders are probably the most likely to receive the most airflow because the forced air has more of a straight shot to reach these cylinders. And to reach the front most cylinder, the air has to make more of a sharp turn so I suspect this cylinder might be receiving less of the forced airflow. But like I said, air does strange things and I could be completely wrong with those initial assumptions. That’s why doing your best to replicate the ram air flow and pressure is important
I'm for putting it on the chassis dyno! Let's see the correlation between EGT and AFR with no ram air effect vs. at speed. Also interesting to see what HP loss you'd have through the drivetrain.
That's what I was wondering, the afr, because it does effect temps. This car is getting where if the sensors and the wires associated etc could shed twenty pounds it seems 😂
