A good day at the dyno...

[jss06c6]

Gents, with all due respect, trying to replicate all MAP cells at all RPM bands on the road is very time consuming, inefficient and requires riding the brake to get cells populated. I certainly don't believe GM and Mercruiser tuned our engines by driving them around with a laptop and tuning software. (If they did, I stand corrected) I would expect they did it on an engine Dyno. The hub Dynos are effectively the same setup, but rather than bolting straight into the flywheel, they both up to the axles. So, yes, there is drivetrain loss, but you have full control of the loads and RPM presented to the engine. Having driven around for hours and hours, riding the brake trying to get decent counts in all VE table cells for my LS engines and now with my LT-5, doing it on an engine Dyno or Hub Dyno is far better and indeed safer, in my humble opinion.

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[XfireZ51]

I’m sure that GM starts out w a base map from engine dyno but why do u suppose they have laptops in cars testing on real roads and in real world driving
environs? If anyone could simulate the driving conditions on a particular road, it would be GM. No substitute for the real thing IMO.
Having said that, I would love to have access to the tools u have as well. I just don’t think u have a finished product without putting on the road.

[Top Toy]

Tuning is invariably an iterative process to get it right. Street tuning for driveability, off to the dyno for max power, then back to the street to verify the dyno tune didn't mess up drivability. In the end, some compromise is unavoidable because our 25 year old ECM's just aren't smart enough to optimize for every variation in driving conditions.

[jss06c6]

Originally Posted by XfireZ51

I’m sure that GM starts out w a base map from engine dyno but why do u suppose they have laptops in cars testing on real roads and in real world driving
environs? If anyone could simulate the driving conditions on a particular road, it would be GM. No substitute for the real thing IMO.
Having said that, I would love to have access to the tools u have as well. I just don’t think u have a finished product without putting on the road.

Yes, I completely agree that the fine tuning comes from real road time!

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[Hog]

I used to have a picture of 4 GM Powertrain engineers in a Chevelle out driving around finishing up the calibration for the Ramjet ZL1 454. That was the Ramjet EFI engine that was rated at 510hp@6300rpm/493 lb/ft torque, with its solid roller camshaft. That was the crate engine where the old Winters foundry tooling was used, along with some changes, were used to cast the modern aluminum BBC blocks. They only built 200 of the ZL1 Ramjets.
There were more than a couple laptops on board.


I also remember some of the ZR-1s that were wired up for testing in North America. There is a video of it around somewhere, there were many analogue gauges.


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I don't think that the OEM LT5 ECMs are lacking for any sort of conditions that it will see. The ECM makes adjustments for air temps, air pressures. Its not like if you are running a stock ECM setup that there are conditions that it cant deal with.
Of course there are advantages to other certain ECMs, but the stock ECM is fine for most users, and once you have the ability to make changes to the stock calibrations, there's really not much you cant get accomplished. The stock ECM isn't limiting top end power or anything, the rev limit can be raised(if you need to) the Injector Flow Rate is adjustable, so you can fuel whatever power level you need.


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Operating environment is important when calibrating.
This is esp. true in the OEM supercharged cars with the GEN 4 LS9/LSA, GEN 5 LT4 and the upcoming LT5. These powertrains are influenced heavily by ambient temperatures and airflow with the amount of heat rejection equipment that is installed on them. IIRC the 2019 LT5 has 4 more "rads" in its heat rejection system.

[Pete]

Originally Posted by Hog

I used to have a picture of 4 GM Powertrain engineers in a Chevelle out driving around finishing up the calibration for the Ramjet ZL1 454. That was the Ramjet EFI engine that was rated at 510hp@6300rpm/493 lb/ft torque, with its solid roller camshaft. That was the crate engine where the old Winters foundry tooling was used, along with some changes, were used to cast the modern aluminum BBC blocks. They only built 200 of the ZL1 Ramjets.
There were more than a couple laptops on board.


I also remember some of the ZR-1s that were wired up for testing in North America. There is a video of it around somewhere, there were many analogue gauges.


xxxxxxxx




I don't think that the OEM LT5 ECMs are lacking for any sort of conditions that it will see. The ECM makes adjustments for air temps, air pressures. Its not like if you are running a stock ECM setup that there are conditions that it cant deal with.
Of course there are advantages to other certain ECMs, but the stock ECM is fine for most users, and once you have the ability to make changes to the stock calibrations, there's really not much you cant get accomplished. The stock ECM isn't limiting top end power or anything, the rev limit can be raised(if you need to) the Injector Flow Rate is adjustable, so you can fuel whatever power level you need.


xxxxxxxxxxxxx


Operating environment is important when calibrating.
This is esp. true in the OEM supercharged cars with the GEN 4 LS9/LSA, GEN 5 LT4 and the upcoming LT5. These powertrains are influenced heavily by ambient temperatures and airflow with the amount of heat rejection equipment that is installed on them. IIRC the 2019 LT5 has 4 more "rads" in its heat rejection system.

What he said.


Is there better ECM/ECU technology today yes of course there is.
For our N/A LT5 our ECM is adequate to handle more power then the block can handle.

Pete

[XfireZ51]

“I don't think that the OEM LT5 ECMs are lacking for any sort of conditions that it will see. The ECM makes adjustments for air temps, air pressures. Its not like if you are running a stock ECM setup that there are conditions that it cant deal with.
Of course there are advantages to other certain ECMs, but the stock ECM is fine for most users, and once you have the ability to make changes to the stock calibrations, there's really not much you cant get accomplished. The stock ECM isn't limiting top end power or anything, the rev limit can be raised(if you need to) the Injector Flow Rate is adjustable, so you can fuel whatever power level you need.”

I am really in agreement w both Paul and Pete here. On an N/A LT-5, I don’t think the stock ECM exhibits any limitations to tuning ur setup. I wish we could bypass the ICM, but beyond that the OEM engine management is very extensive
because it needs to be.
Limited purpose motors are a different story if u want to extract the maximum.

[jss06c6]

So far, I have not seen any limitations presented by the OEM ECM. OBDII controls are a bit richer, but the ECM in the LT-5 is definitely state of the art for the time it was introduced. Managing effectively two tunes, real time, is a testament to the engineers that put this engine in the market..

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[Hog]

Originally Posted by jss06c6

So far, I have not seen any limitations presented by the OEM ECM. OBDII controls are a bit richer, but the ECM in the LT-5 is definitely state of the art for the time it was introduced. Managing effectively two tunes, real time, is a testament to the engineers that put this engine in the market..

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(Emphasis mine.)


Hear, hear!


These 2 power/torque curves certainly had different calibration requirements. Same engine, Port Throttles Open vs. Port Throttles Closed.
(dyno graph supplied by Graham Behan)






As you can see, she gets a bit wheezy with the Power Key Turned to Reduced/Normal from Full. Cuts down over 225 crank hp @ 6500rpm


Yes the ECMs ability to switch from 8 injectors to 16 and to keep up with the variable geometry plenum were simply amazing for 1980s technology.
Going from 16 injectors down to 8 required a TPS % zero out IIRC, at least in the OEM cals. The LT5 was a huge step coming out of the performance doldrums of the 1970s and early 80's when 3221 1980 Corvettes were available with a 180hp@4200/255lb/ft@2000rpm SAE net hp LG4 305 "gasp" with 8.5:1c/r(and a $50 rebate for such a necessity-the L48 350 made 190hp@4200rpm/280lb/ft@2400rpm with 8.2:1 c/r, the L82 made 230hp@5200rpm/ 275lb/ft torque@3600rpm with 9.0:1c/r).


So I'd agree with you and say that more than doubling the output of the engine, in less than 10 model years of a car, without using forced induction, while still maintaining emissions and still pulling a 16/25 MPG rating, is certainly an amazing engineering feat. It must have been an exciting time to be an Engineer at Lotus. or any other manufacturer.
Being able to report SAE net ratings of 375hp@6000rpm and 405hp @5800rpm and then develop the 3rd iteration of the LT5 with numbers over 525hp@7200rpm must have been a satisfying "days work".
It would take the Chev guys well over 10 years to get over 500hp into a N/A car with the 2006 LS7 and its SAE Certified 505hp@6300rpm/470 lb/ft @4700rpm, but into a car the GEN 4 LS7 went. I so wish the GEN 3 LT5 went into a C5, with the Lotus C5 powebulge hood and all.

[Vette73]

The saving grace back in the mid 70s and early 80s was the ease of modding the sbc if you couldn't afford a ZR-1...Take out the smog choked L-48 and for that matter the L-82 and put in a 383 stroker or 406 small block..

From what I understand the trannies back in the mid 70s could handle big jumps in horsepower ...If you had a four speed even better...

You can build a streetable 450 horsepower sbc for 4-5 thousand dollars......Not many people could afford to spend 60-65K on a Z back in the day...