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Individual Cyl trims and EGTs

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So in one of your videos I saw that you aim for a 10-15 degree variance in EGT temps per cylinder. I've found in JZ engines under high boost/high backpressure situations (figure 1000-1500hp+) that the sheer volume of fuel and/or timing to bring the offending EGT(s) in line with the rest seems very excessive. In some instances changes as high as 30% or more additional fueling, which I know is too much as the drop in power can be substantial.

I decided to do some testing and made sure that all the injectors were cleaned/flow matched, installed new EGT probes and replaced the wideband sensor (bosch LSU 4.2). During testing, I also had the dynojet wideband in the downpipe, which matched up very close to the one in the car and hooked up to the ECU for logging.

Mechanically, the engine is a 3.2L 2jz with 10.5:1 pistons (so add more compression with the stroke), "greddy style" custom intake manifold, tubular exhaust manifold , T6 turbine, 150 direct port and e98 fuel. Down the track the hottest cylinders (4 and 5) flirt with around 920-950c by the end and are roughly 100 or so degrees hotter than the rest.

First, what do you think about those EGT temps at the end?

Second, any suggestions to look at on bringing in the hotter cylinders in line? The ECU we are using has individual trims per injector and ignition as well, both via tables that are Load X RPM.

Interesting read, as we'll be in the same spot in a couple of weeks, when we've finished our 2JZ project car.

Personally, I think that it might be an uneven distribution of air going into the cylinders at high load/rpm caused by the intake manifold deisgn.

We're using the hypertune intake manifold with CNC'd runners (sample picture: http://www.brewedmotorsports.com/assets/products/Hypertune/2jz_hypertune_largeport_race_manifold_18_injectors.jpg), and also 6 individual open tip EGT probes, so I'll report back what we've found out about EGT's at that point.

We'll be also using MoTec's Lambda to CAN for the first time and will compare the results to our Dynojet's Dyno lambda readings.

Not any help at this time, but hopefully we can compare our findings at a later point

I've seen this behavior before with different intake manifolds, so I'm not entirely convinced it is that. I'm betting on the exhaust manifold as the runners are not equal length. I'm betting the shorter runners towards the middle of the engine are seeing higher back pressure than the others, thus throwing the egt reading off. What I don't know is how much the higher pressure affects the egt probe if at all.

MegasPSI, Personally I typically like to aim for around a 15 degree variance between cylinders. It's not uncommon to see a 25%+ difference in fuel trims between cylinders to get these in line. The last engine I tuned while using EGT's was a Twin Turbo 1UZ on Methanol, this required a 24% difference between the hottest and coldest cylinder, still requiring some tweaking at the track. It would not surprise me if I end up closer to 30%.

The variations I felt were more influenced from the intake manifold in this case.

Your EGT's I feel are quite high for an Ethanol fuel, I would of thought in the mid-lower 800s. 900+ is something I would expect from pump gas and a 100degree difference is huge. What lambda are you targeting? Ignition timing? Have you tried trimming more into those cylinders and what happens? Any log files?

Hey Chris,

Thanks for the feeback. 30% seems HUGE, I'll have to give it a shot and see how it behaves. Last time we started approaching numbers like that it was really hurting power and in some cases causing a rich misfire, so I assumed it was an erroneous reading to a point. Reading plugs on ethanol is nothing like reading plugs on gasoline from what I'm told.

I too think the EGTs are higher than I'd want, but they don't seem to want to come down regardless of whats being done. This particular 3.2 is making well over 1400whp using boost AND nitrous through a powerglide, so the cylinder pressure WAY up there. Off the nitrous the car has around 10-11degrees at peak torque and as the RPMs approach the redline (9k) it'll creep back up to around 15-16. On the nitrous, we are pulling 3-4 degrees from the base timing. We have tried some other fuels as well, such as Ignite Red and FTW, but had similar results in regards to the EGTs.

The target Lamda is .75. I do have some logs that illustrate this and will dig them out.

One thing I forgot to add as the higher EGTs are typically only on the nitrous. With boost only it'll fall perfectly into 800-850c

Typically I like to see the individual cylinder fuel trims in the region of about a 15% spread from richest to leanest, but it isn't uncommon to see higher. That's where I've tended to end up with most of the drag engines I've been involved with. At the same time it isn't always the case and you need to understand how the EGT can be influenced.

Obviously the EGT will be effected by cylinder to cylinder AFR as that's what we are trying to optimise here. On top of this though it can also be seriously affected by ignition trims (retarded timing will increase EGT) and just as importantly how the EGT sensor is fitted. If you want accurate results, it's important that each sensor is mounted the same distance from the exhaust valve and also that the tip is located as close as possible to the centre of the runners. Lastly even with perfectly matched AFR and consistent ignition timing you can still see EGT fluctuations cylinder to cylinder related to the actual heat distribution in the block and cylinder head.

The key point though is that if your fuel trims are moving in the right direction you won't be losing power. If you doubt the EGT sensors, you can also have a look at the spark plugs. These should give you a guide as to the combustion temperature that we would hope lines up with the EGT readings.

The better way to tune the individual cylinder fuel trims is to use individual cylinder lambda sensors in each runner. One of the biggest problems with EGT sensors is their slow response which makes it impossible to build a 3D cylinder trim map with respect to load and rpm.

With regards to your actual EGT, I agree with Chris, that seems higher than I would expect. Of course this is dependent on the boost, AFR and ignition advance among other things. On E98 I would be expecting EGT's in the mid 800's.

You mention that you are using a direct port nitrous system. If the foggers aren't spraying evenly, this could easily cause all the discrepancy you are seeing. Are you spraying the entire way down the strip? Is it a wet kit or are you delivering fuel through the injectors?

Hi Andre,

We are spraying a wet shot. That was the first thing we inspected and took the jets apart and bench tested. All good there. I considered jetting the hotter cylinders with extra fuel but wanted to explore some other options first to confirm what was really happening.

I'm curious about putting Lamda sensors in the runners. I saw in one of your other vids that the AEM 4 channel uego has a pressure calibration component but is it still viable with pressures and temps this high?

We are spraying all the way down the track. Given your experience and the fuel we are running what do you feel about the timing we are running? Remember on the spray we are running around 12-13 degrees on the back half of the track in 2nd gear (1:1) towards the top of the rev range 7800-9000.

Another successful tuner in this area told me we need to target richer afrs closer to .7 lamda or lower. The ignition will handle it but that seems really rich and a band aide to the real issue.

wow 15%... Does this mean that say for example you were targeting Lambda 0.78 and the overall O2 reading was 0.78 but EGT's were off on one cylinder (Straight 6 for example) and you had to add 15% of fuel to that cylinder then it would have been running somewhere around 0.92??

Or is it more a case of you were reading 0.78 at the collector, Add fuel 15% to the hot cylinder and you end up reading say 0.75 And then you trim your fuel map back to regain your target of 0.78... And that one cylinder isnt actually 15% off of your target AFR but somewhere in between.... That is still quite scary tho that cylinders can be running such varied mixtures!

I highly doubt that the any of the cylinders were as lean as a you are thinking or they would most likely have long since melted a piston, burned a plug or torched the head gasket. Granted, it might not be .75, and quite possibly .8-.85 though.

Hey MegaPSI,

The individual cylinder lambda kit is back pressure compensated and hence is perfectly suited for high boost turbo use. The Bosch LSU 4.2 sensors are rated at a continuous 930 deg C and 1030 deg C for short periods. The AEM weld bungs locate the sensor so the tip is basically flush with the runner wall. This reduces the heat exposure as well as ensuring the sensors aren't restricting flow.

You still haven't mentioned the boost you are running so it's hard to be specific. On the face of it 12-13 degrees seems low to me, even with 10.5:1 and a 150 shot. My usual guide is 2 degrees retard per 50 hp which would have your timing somewhere around 18-19 degrees off the gas. Like I say it's hard to be more specific without knowing your boost pressure but for E98 I would expect a little more advance. What I would try next time you're on the dyno is doing a base pull and then adding 2 degrees advance and see what the net result is. my guess is you're going to pick up quite a lot of power on boost and see the EGT drop (I've been wrong before but with the limited info that would be my first test).

As for AFR, I treat E85/E98 in a similar way to a high quality race fuel. Even under high boost I would be starting with a target lambda around 0.78 and tuning from there. You shouldn't need to be anywhere near 0.70 and if you were I would expect the power to suffer.

As for boost typically between 45-50psi for the scope of this conversation. Good to know about the 930C continuous....had no idea they were rated that high!

Off the gas the timing falls about where you saying and we did not pickup any HP or MPH/ET by going further, so that appears to be about optimal. I pulled out a degree just for safety factor, especially with the higher EGTs.

We are pulling 4 degrees on the direct port.

I'm surprised that the engine doesn't want to see more timing to be honest. Pulling that extra degree of timing for safety though will in fact increase your EGT, so kind of making matters worse for you. If you're engine is knock limited I'm a big fan of having a good degree of safety in your timing. If you aren't anywhere near the knock threshold though you can probably leave the timing set at MBT with a reasonable degree of certainty that it won't be dangerous.

If you tried more timing on the dyno and had no trouble with knock, I would do a run at the strip with an extra 2 degrees timing and see how that effects your EGT.