Before and after dyno results

[Tony D]

I believed all the same things.

Trust me when I say...

We did not TOUCH timing. We were working 'one variable' at a time. We had a timing curve that was not detonating (FINALLY) and were working FUEL ONLY.

 

Lance said something similar to what Mack said, it just doesn't all burn...it gets a free ride out the exhaust valve and down the exhaust.

 

I did not believe him either, and actually Jeff was quite insistent up to that point that we run the recommended 12.5 AFR across the board with minor changes.

 

After torque peak, we pulled fuel and the EGT's dropped, and power came up.

 

EVENTUALLY we went to timing after seeing diminishing returns on the fuel, and STARTED to advance the timing...but ran out of shceduled time on the dyno.

 

Everyone says you can run your whole table in about 2 hours start to finish. I will agree with that. After that two hours you are simply playing around doing things you are curious about...or are too hard-headed about it and are trying to force an issue that will not be resolved without further work in other areas. It was a little of the last two. I think we completed 95% of his fuel spark table in 45 minutes on that run (which lasted ultimately 4 hours I believe), but after that we were curious about what Lance had said to do, and why some things were happening that we couldn't explain.

 

The last part took Jeff many hours in the garage with a dremel tool and an O-Scope to finally make up his mind...

 

Let's just say 'back to square one' regarding fuel maps and timing maps...only this time the system being programmed will not be 'Nissan Based'!

 

 

Oh, on the EGT and lowering it by richening up the mix...this is basically what I did for years on my non-intercooled blowthrough setup. So my logic for believeing the same things you guys are talking about was rooted in personal experience as well. Add fuel, then take it out till peak or desired EGT is achieved. I would never have thought the EGT would have dropped taking fuel out where we did. There were 'four blocks' on Jeff's map that stayed in the 11:1 portion, and they were the ones where we physically could not get enough load on the engine quick enough to get into due to some air density issues the day at the dyno. So he left them pig rich knowing as we all do 'Rich is Safe'.

 

Lance is a bit out there, you talk to the guy for about an hour before you realize where he is in regards to engine performance and management. It takes a while for me to get up to his speed...and till then I guess he tolerates my stupid questions. Once we are on the same page, though, then he goes into warp speed explaining things again thinking now you will keep up...and it's back to 'Stupid Tony Questions' again! The guy is out there, in more ways than one...but man he's got the Engine Management Stuff down in a scary way!

[Tony D]

However, I think it's extrordinarily difficult to 1) determine what AFR is best at each RPM/load point and 2) to tune to the desired AFR once it's know. For that reason I make some broader generalizations on what AFR to run at what load point.

 

Yes it all takes time, but once you get a general idea where the peak power is produced, you simply decide how much 'peak power loss' you can tolerate and set your AFR's up accordingly to give the margin of safety you desire.

 

We were making passes on the Mustang till we reached peak power, then moved timing around in that area to see what effect it had. Sometimes retuned AFR, then went back and checked for repeatability. Once spark and fuel was optimized we went to the next series of bins on the load chart.

 

In the Lower N/A portions of the map, we were leaned out quite a bit for economy, and like you said, JGK, under boost we went a bit more conservative with both timing and AFR.

 

And now we get to do it all over again with the new EMS system!

[RTz]

According to Jeff Hartman...

 

[RTz]

You can put tons of fuel, but it only burns at one rate.

 

Thats contrary to my experience, and Hartmans....

 

 

 

 

These two snips were taken from his book "How to Tune and Modify Engine Management Systems".

 

My findings don't always jive with his, but often enough to justify reading his stuff.

[RTz]

However, I think it's extrordinarily difficult to 1) determine what AFR is best at each RPM/load point and 2) to tune to the desired AFR once it's know.

 

As Tony mentioned, its reasonably straight forward on a static dyno... and thats the key. With the dyno holding you at a specific RPM, you can tune for MBT (mean-best-torque). I wouldn't even begin to try it on an inertia dyno.

[BRAAP]

***edit***

OOPS! I need to clarify my blanket statement which was to be "as interpreted by EGT’s alone".

 

 

***edit, part deux***

 

You know what? This topic is extremely deep. WAY too deep for blanket statements.

[Tony D]

As Tony mentioned, its reasonably straight forward on a static dyno... and thats the key. With the dyno holding you at a specific RPM, you can tune for MBT (mean-best-torque). I wouldn't even begin to try it on an inertia dyno.

 

ARGH! I appreciate you noticed I mentioned Mustang! Andy is a big fan of the Dynojet inertial and I DO NOT LIKE tuning on that machine! I MUCH prefer the Mustang. The ability to simply HOLD a point while I try different things just lets me think stuff out...

 

I mean, we put Jeff's car on a 35% grade and were making passes from 80 to 120mph. Eventually we started toying with some of the Mustang's features that allow it to automatically increase load to prevent the engine from accelerating past X-Point. That was kind of scary... We went back to manually loading the engine at between 15 and 20% grade to allow an 'acceleration' style run. But there were times that I just kept increasing the grade till Jeff gave me the signal that the loadpoint was in the same box he wanted to tune and then he started fiddling while I was watching instaneous torque.

 

At the load points in the upper ranges of the Map...that meant 17psi at 6800, 7000, 7200 rpm and just letting it sit there while he made adjustments.

 

What is wild is how when you let the thing sit at a loadpoint for a second or two, you realize that 'fast instrumentation' is not all that fast, and that there is no way in HELL that I would ever want to seriously tune on an inertia dyno under boost because stuff is lagging so bad... You can 'fudge' your numbers a given ammount and get close...but when you can do it right, why not, Eh?

[Daeron]

*holds hands up to head*

 

 

MY BRAIN Hurts, but it's in a good way...

 

Thanks for the very educational thread, everyone!

[thehelix112]

Dynojet's are inertial? Haha.. no wonder they suck so hard.

 

Dave

[Tony D]

I just got off the phone and confirmed with Jeff P my recollections.

Originally he was running the base tune in the 11:1 range, and we had the timing set. Generally it was around 19 degrees at full rpm and 17-20psi of boost.

 

That original tune was glowing on the dyno. I did confirm that we did not touch the timing, as we were in the 'fuel trim only' mode since our goal was to lean it out till it stopped making more power. We were concentrating on the AFR's near and past the torque peak of the engine (basically 4000 to 7500 rpms).

 

We kept pulling fuel, with bins past the torque peak in some cases in the 12.8 to 13.2 AFR range being where we settled on. That is to say our process was to go until we either got detonation or we started seeing instantaneous torque drop. At either point, we then backed off .2 or .3 AFR points and left it alone to move to the next loadpoint bin.

 

So that means we were actually close to 13.5 to get best torque. That would seem to follow the EGT logic from the articles above, the 11:1 for some reason had very high TIT and TOT (not measuring individual cylinders, just turbine in and out) at the 11:1 AFR for some reason. The only thing I can figure is some sort of 'post burning'.

 

Once we were above 12.5, the differences in TIT AND TOT observed were 'insignificant' on our instrumentation, so it may well have followed the same trend given the 25 degree and 50 degree trends. I used to have access to a 12VDC powered Industrial Engine Exhaust Gas Thermocouple Panel that I would use...digital readout of temperatures accurate as heck. Unfortunately we didn't have that, or the numbers could have been trended closer.

 

Any reason why his engine would have shown higher temps at 11:1 (only after torque peak) than at 12.7 to 13.5?

 

Hope that cleared up the mystery somewhat. We definately were not screwing with timing to get EGT's down, it was set and left alone will we got the AFRs more optimized. We were loosing too much power at 11:1, and felt AFR was where the most traction would be achieved power-wise...

[Tony D]

Dynojet's are inertial? Haha.. no wonder they suck so hard.

 

Dave

 

Apparently there are upgrades you can do to them now to give a load-point constant load. I just haven't seen one yet to compare with how the Mustang works.

 

Then again, the Mustang place straps it down and lets us alone. For $75 an hour with me as the operator, it's hard to argue with price, either!!! Not many places just turn you loose on their $40K dyno and say "let us know when you want to get off, we have someone coming in at 1300, so you have to unstrap by 1230 regardless!"

[ww]

Well put Ron and Tony. I was a "more fuel equals lower EGT's" devotee / religious fanatic until a friend of mine, who's a huge turbo diesel tuner and has tried to describe the same thing to me over and over again for the last 5 years.

 

I now have easy, nearly unlimited access to a free dyno which I prefer to use for tuning rather than my mis-informed religious inclination!

[dapiper]

Fascinating.

 

Can you measure turbine backpress? If it's excessive, it could contribute the afterburn scenario you observed.

[RTz]

Once we were above 12.5, the differences in TIT AND TOT observed were 'insignificant' on our instrumentation, so it may well have followed the same trend given the 25 degree and 50 degree trends.

 

There are probably a few of us that would be interested in your interpretation of the delta's of the TIT/TOT's?

[Tony D]

TIT and TOT were monitored, but we focused mostly on TIT as that was our direct goal for monitoring EGT. I can't even remember the delta on that setup.

 

As for backpressure, with the last build, at 23psi, the backpressure in the manifold was 23psi...

 

Now, with a turbo flowing more, external wastegate, and tubular header to the turbo, and making probably 100 more RWHP at 17psi that we previously did at 23+ psi I'm thinking our backpressure in the manifold is O.K., especially given the way the engine starts breathing and pulling up top!

 

If I had a better (read Digital) EGT Gauge for TIT and TOT, comparisons would probably be more valid... I don't know if I wrote those down. I'm thinking I didn't as the stuff I did write down I seem to be remembering pretty well... BAH!

[Randall]

I know this is an old thread but I have been playing around with my tune and I was curious what egt's you where shooting for?

 

I have heard under 1600 degrees F. Mine with my current tune hits a peak of about 1500 F at 10 psi 12:1 afr without an intercooler. Timing is about 25 degrees. 

 

At first my AFRs were about 11.7 and i think I was having rich misfires. My knocksense light was going off too but I think its just noise as it only goes off above 4000 rpms.

 

Also my EGT's are about 800 at idle and 10-1200 at cruise. 

 

My sensor is in the stock manifold between the turbo flange and the exhaust port flange.

Edited March 24, 2013 by Randall

[Tony D]

That is TIT, a raw composite of all the cylinders combining.

EGT prob is physically as close to the head to manifold flange as you can get it (AIR Injection fittings work great on early NA manifolds!)

 

As noted, you look for variation amongst the cylinders.

[malibud]

I know this an old thread but very informative. I also have read where every engine is different so there is no best but I am looking for some ball park numbers.  have had a hard time finding information on base AFR to tune to. I have a remapped 300zx ECU, 420cc injectors and IC, Borg Warner turbo, Forged pistons. I can only adjust for AFR through my fuel pressure regulator. I am running very rich like 10-10.5 @ 17psi (up from 9 and a smoke screen).  Idle is around 13 afr and cruise is around 15.

My fuel pressure is around 36 PSI at idle with no vacuum to the regulator. (I understand 36psi is stock )

 

Would say 30 PSI be safe to try to get the AFR down?

 

Would a target Afr of 12.5-13 under full boost (17 psi) be safe ?

Thanks '

Dan

[Tony D]

Oversimplified the thread to the extreme. The point of the thread was "it's not that simple"!

[malibud]

I know Tony I wish you were here so I could just pay you to get my set up right. I have been looking at MS maps to try to get a ball park safe range. So far I am still running and fighting boost leaks.