E85 EGTs
 

Hi guys looking for some tips on how I can improve my map, especially in trying to lower EGTS as I've been coming close to 1000 deg C on full power runs.
Engine is running on race E85 and is slightly ported and using a single turbo BW S363 with 1.0AR and 3.5 downpipe / 4.0 inch exhaust. All your comments are appreciated. I am attaching the ecu file and a sample of latest log running this file.

This is pretty much where I stopped researching last. Let me know what you find!

What is the actual EGT setup? The log file is reading different values in EGT1-4 implying all of those inputs are receiving some sort of signal. I'm assuming there are twin probes with one in each runner, and that they are sending signal to EGT1 and EGT2, but out of curiosity which of those is the front and which is the rear? And I'm correct about those, what is reading to EGT3 and 4?

https://cimg0.ibsrv.net/gimg/www.rx7...6c764688c5.png

Hi Skeese thanks for replying. It's a TC4 Unit connected through serial. Only 2 sensors are connected 1 & 2. 1 being the front. So you are correct. As for why 3 & 4 still show a reading without sensors connected I am at a loss. Maybe it's got something to do with the TC4 Unit.

Mine does the same. 3 and 4 arn't used but they send something.

Hey!

So I haven't had time to dig into the actual data and don't know when I will, but wanted to post the MLV charts from your log. They are scaled in the same RPM x MAP step sizes as are in your tune file to make it easy to interpret.

These first two are the temps from each individual thermocouple averaged across the cells of the entire log, if that makes sense.

https://cimg0.ibsrv.net/gimg/www.rx7...a049ecfc4e.png


https://cimg4.ibsrv.net/gimg/www.rx7...9fa08ff638.png

And lastly this third chart shows the split different between the two charts above, for what it is worth.

https://cimg3.ibsrv.net/gimg/www.rx7...929b0589a9.png


I'm surprised the car runs so close to the target lambda with a flat VE map that hasn't seen any tuning. It appears to me that there has been a good amount of detail put into the rest of the tune file, so it just seems odd to me that there is just a flat VE fueling map being run in open loop.

Hope this helps!

Skeese

Hi Skeese

thanks for your points. You are assuming that the map hasn't seen any tuning but the reality is that I just interpolated from corners after many street tuning hours. Having said this, the map isn't final and I keep updating it. Your charts interpret the logs in such a way that makes it easier to see the global picture.

Which brings me back to my question. I am looking for some help re: timing as for fuel i'm in a pretty good position. My dyno guy is currently repairing and calibrating his dyno which will take over an other month to be done hence why I am asking for guidance here.

From what I gathered, Pump Gas should be in the range of 1250-1750F for maximum EGT. 1250 seems VERY low to me.

How ethanol burns in comparison to Pump Gas, we already know. In regards to flame front, fuel density, and resistance to knock, at least... I just don't have a quantified range as to where those safe tuning figures would be for this fuel. :(

Thanks for your input SirLaughsALot.

What would you say your timing map would look like on pump gas to extract the most power while lowering EGTS.

I have zero experience. This is my best estimate:

I have timing maps from UMS Tuning (Tony) and a few others. The Ric Shaw derived basemaps from Adaptronic shouldn't be too far off for pump gas. From there, bring up timing on the lower end (idle to 3k RPM) in 0.5° increments until you sense it's flatness. Back off 1.5° for safety. Then work 3k-5.5k. Then 5.5k to 8k+.

I have a feeling the timing "shape" will be similar, but likely look similar to a "bass boost" applied to your timing map with added timing in lower rpm sections since you have so much detonation resistance, you can have it build torque earlier.

Obviously AFRs and boost should be dialed in before this. I wouldn't adjust timing at all if either were fluctuating at this stage of tuning.

E85 seems to like being run leaner than our standardized rotary Lambda values.

So for instance if you like tuning 11:1 AFR (0.75 Lambda) @ WOT for your 13b on pump gas, it'll likely want something closer to 12:1 Normalized Pump Gas AFR/8:1 e85 AFR (0.82 Lambda).

Tune in Lambda. That's what your sensor reads in, so should you.

Thanks for your insight, very much appreciated. I will continue working on this the coming weekend and will give you guys an update.

I definitely wouldn't use the timing map from the Rick Shaw Adaptronic base map.

For starters that wasn't an E85 car or a single turbo car.

If you do some digging between this forum and the adaptronic forums you'll find multiple places where Elliott (Turblown) has posted tuned maps with various E85 setups. I know for a fact there are E85 timing maps he put together that range from street port 15 PSI E85 all the way to 30 PSI (I don't remember the port of that one).

I like the way his timing maps are laid out. All very smooth with the use of a lot interpolation but if you look at the entire range everything seems to fall within reason and spec. As timing is something that is finitely tuned on a dyno, I believe a good E85 timing map built the way he does his is the way to go. That way there is actually a way to gauge the results when you make it to a dyno. Making changes in a mass of erratic chaos won't give you any interpretable results.

If you can't find what I'm talking about online, I'm pretty sure I have an assortment of them saved on my hard-drive that I can dig up.

Skeese

Back up for a second. What exactly is the problem? The EGT's are fine. You're less than 1000C in a quick transient. The turbo will hold up fine. Modern turbos can handle very high temperatures; it is the older designs (which were really for diesels) that are more sensitive. Nothing's going to melt if you have put your setup together correctly (exhaust manifold is durable etc). This is about the same temperature that a turbo direct injected modern piston engine runs with twin scroll turbo; single scroll can allow slightly more, over 1000C. 1750F as a rule of thumb is 950C. And that's for a quick transient, just hitting that for a second or two. I would say that conservative of a limit applies more to older turbo designs. It's not a bad thing to have safety margin, but there are consequences to bringing down your exhaust temperatures which I will explain.

General rule of thumb with modern turbos is: 980C twin scroll and 1050C single scroll limit for continuous operation. So that's if you had this engine on a dyno and ran it at full boost for 100 hours like the OEM durability tests do. In a transient it can hold up more because it hits those temperatures for a split second and the metal doesn't have time to fully absorb the hot gases. The source of that is material from turbo suppliers I have worked with in my day job.

You've got three options here:

1) advance the timing. This will increase pressure in the combustion chamber. Since we don't know where you're at in terms of combustion pressure, because that instrumentation is very expensive, it is a risk of cracking a plate or breaking a seal. Even if you are not knocking you can still break something because average peak cylinder pressure increases as the combustion is advanced. Of course you can advance timing on the dyno and look at the torque/power gained per each degree added and make a judgment call.

2) richen up the mixture. This will stress your ignition system and increase risk of misfire, but it will bring down EGT and give you more margin for leaning out if the weather changes.

3) turn down the boost. This is the safest thing to do, but obviously you lose power and torque.

Thank you for this.

So just to clarify, you're saying 980C Transient Peak Temperature for a Twin-Scroll, yes? :icon_tup::icon_tup:

What about steady state figures? What can modern turbos handle for LONG durations of cruise to where we get enough thermal expansion to make the turbos efficient?

Hi guys, sorry I didn't get back to you earlier but was overloaded with work and other commitments. Yesterday I managed to find the time to make a few changes and increased timing by a couple degrees. This seems to have worked to a certain extent but I will need to go out again preferably to the drag strip and log everything. Thanks again to everyone for your input, keep it coming.

ps. Fuel I'm using has an AKI 104 (RON 112 & MON 95) rating so I know I'm safe. Also I'm not worried about breaking the engine as this is a spare unit so willing to take it to the extreme in the name of "science"